Electrical stimulation of the globus pallidus internus in patients with primary generalized dystonia: long-term results

Successful deep brain stimulation surgery with intraoperative magnetic resonance imaging on a difficult neuroacanthocytosis case: case report

BACKGROUND AND IMPORTANCE

Chorea acanthocytosis is a progressive hereditary neurodegenerative disorder characterized by hyperkinetic movements, seizures, and acanthocytosis in the absence of any lipid abnormality. Medical treatment is typically limited and disappointing.

CLINICAL PRESENTATION

We report on a 32-year-old patient with chorea acanthocytosis with a failed attempt at awake deep brain stimulation (DBS) surgery due to intraoperative seizures and postoperative intracranial hematoma. He then underwent a second DBS operation, but under general anesthesia and with intraoperative magnetic resonance imaging guidance. Marked improvement in his dystonia, chorea, and overall quality of life was noted 2 and 8 months postoperatively.

CONCLUSION

DBS surgery of the bilateral globus pallidus pars interna may be useful in controlling the hyperkinetic movements in neuroacanthocytosis. Because of the high propensity for seizures in this disorder, DBS performed under general anesthesia, with intraoperative magnetic resonance imaging guidance, may allow successful implantation while maintaining accurate target localization.

Deep brain stimulation: indications and evidence

Deep brain stimulation is a minimally invasive targeted neurosurgical intervention that enables structures deep in the brain to be stimulated electrically by an implanted pacemaker. It has become the treatment of choice for Parkinson's disease, refractory to, or complicated by, drug therapy. Its efficacy has been demonstrated robustly by randomized, controlled clinical trials, with multiple novel brain targets having been discovered in the last 20 years. Multifarious clinical indications for deep brain stimulation now exist, including dystonia and tremor in movement disorders; depression, obsessive-compulsive disorder and Tourette's syndrome in psychiatry; epilepsy, cluster headache and chronic pain, including pain from stroke, amputation, trigeminal neuralgia and multiple sclerosis. Current research argues for novel indications, including hypertension and orthostatic hypotension. The development, principles, indications and effectiveness of the technique are reviewed here. While deep brain stimulation is a standard and widely accepted treatment for Parkinson's disease after 20 years of experience, in chronic pain it remains restricted to a handful of experienced, specialist centers willing to publish outcomes despite its use for over 50 years. Reasons are reviewed and novel approaches to appraising clinical evidence in functional neurosurgery are suggested.

Treatment of dystonia

Selecting the appropriate treatment for dystonia begins with proper classification of disease based on age, distribution, and underlying etiology. The therapies available for dystonia include oral medications, botulinum toxin, and surgical procedures. Oral medications are generally reserved for generalized and segmental dystonia. Botulinum toxin revolutionized the treatment of focal dystonia when it was introduced for therapeutic purposes in the 1980s. Surgical procedures are available for medication-refractory dystonia, markedly affecting an individual's quality of life.

A randomized double-blind crossover trial comparing subthalamic and pallidal deep brain stimulation for dystonia

Object

The authors' aim was to compare the subthalamic nucleus (STN) with the globus pallidus internus (GPi) as a stimulation target for deep brain stimulation (DBS) for medically refractory dystonia.

Methods

In a prospective double-blind crossover study, electrodes were bilaterally implanted in the STN and GPi of 12 patients with focal, multifocal, or generalized dystonia. Each patient was randomly selected to undergo initial bilateral stimulation of either the STN or the GPi for 6 months, followed by bilateral stimulation of the other nucleus for another 6 months. Preoperative and postoperative ratings were assessed by using the Burke-Fahn-Marsden Dystonia Rating Scale (BFMDRS) and video recordings. Quality of life was evaluated by using questionnaires (36-item Short Form Health Survey). Supplemental Toronto Western Spasmodic Torticollis Rating Scale (TWSTRS) scores were assessed for patients with focal dystonia (torticollis) by examining the video recordings.

Results

On average for all patients, DBS improved the BFMDRS movement scores (p < 0.05) and quality of life physical scores (p < 0.01). After stimulation of the STN, the mean 6-month improvement in BFMDRS movement score was 13.8 points; after stimulation of the GPi, this improvement was 9.1 points (p = 0.08). Quality of life did not differ significantly regardless of which nucleus was stimulated. All 12 patients accepted 6 months of stimulation of the STN, but only 7 accepted 6 months of stimulation of the GPi. Among those who rejected stimulation of the GPi, 3 accepted concomitant stimulation of both the STN and GPi for 6 months, resulting in improved quality of life physical and mental scores and BFMDRS movement scores. Among the 4 patients who were rated according to TWSTRS, after 6 months of stimulation of both the STN and GPi, TWSTRS scores improved by 4.7% after stimulation of the GPi and 50.8% after stimulation of the STN (p = 0.08).

Conclusions

The STN seems to be a well-accepted, safe, and promising stimulation target in the treatment of dystonia, but further studies are necessary before the optimal target can be concluded. Simultaneous stimulation of the STN and GPi should be further investigated. Clinical trial registration no.: KF 01-110/01 (Committees on Biomedical Research Ethics of the Capital Region of Denmark).

Tolerance of early pallidal stimulation in pediatric generalized dystonia

The authors report on 2 cases of pediatric generalized dystonia with a DYT1 mutation; the patients, an 11-year-old girl and a 9-year-old boy, underwent chronic, pallidal deep brain stimulation (DBS) of the globus pallidus internus (GPi). The dystonic postures in both cases showed dramatic improvements with pallidal DBS, but each patient's symptoms gradually recurred within a year, irrespective of exhaustive readjustments of the stimulation settings. After the recurrence of the dystonic symptoms, the DBS leads were replaced within the GPi in one patient (Case 1) and additional DBS leads were implanted into the bilateral subthalamic nuclei in the other patient (Case 2). Neither measure produced any further clinical benefit, and the patient in Case 2 died of status dystonicus 2 days after reoperation. These findings suggest that early pallidal DBS for pediatric dystonia is indeed effective, although there are some cases in which its therapeutic effect is lost. One possible reason may be the ability of the preadolescent brain to tolerate chronic electrical stimuli during the active maturation process.

Deep brain stimulation in children and young adults with secondary dystonia: the Children's Hospital Los Angeles experience

Background

Dystonia is a movement disorder in which involuntary sustained or intermittent muscle contractions cause twisting and repetitive movements, abnormal postures, or both. It can be classified as primary or secondary. There is no cure for dystonia and the goal of treatment is to provide a better quality of life for the patient.

Surgical intervention is considered for patients in whom an adequate trial of medical treatment has failed. Deep brain stimulation (DBS), specifically of the globus pallidus interna (GPi), has been shown to be extremely effective in primary generalized dystonia. There is much less evidence for the use of DBS in patients with secondary dystonia. However, given the large number of patients with secondary dystonia, the significant burden on the patients and their families, and the potential for DBS to improve their functional status and comfort level, it is important to continue to investigate the use of DBS in the realm of secondary dystonia.

Object

The objective of this study is to review a series of cases involving patients with secondary dystonia who have been treated with pallidal DBS.

Methods

A retrospective review of 9 patients with secondary dystonia who received treatment with DBS between February 2011 and February 2013 was performed. Preoperative and postoperative videos were scored using the Barry-Albright Dystonia Scale (BADS) and Burke-Fahn-Marsden Dystonia Rating Scale (BFMDRS) by a neurologist specializing in movement disorders. In addition, the patients' families completed a subjective questionnaire to assess the perceived benefit of DBS.

Results

The average age at DBS unit implantation was 15.1 years (range 6–20 years). The average time to follow-up for the BADS evaluation from battery implantation was 3.8 months (median 3 months). The average time to follow-up for the subjective benefit evaluation was 10.6 months (median 9.5 months). The mean BADS scores improved by 9% from 26.5 to 24 (p = 0.04), and the mean BFMDRS scores improved by 9.3% (p = 0.055). Of note, even in patients with minimal functional improvement, there seemed to be decreased contractures and spasms leading to improved comfort. There were no complications such as infections or hematoma in this case series. In the subjective benefit evaluation, 3 patients' families reported “good” benefit, 4 reported “minimal” benefit, and 1 reported no benefit.

Conclusions

These early results of GPi stimulation in a series of 9 patients suggest that DBS is useful in the treatment of secondary generalized dystonia in children and young adults. Objective improvements in BADS and BFMDRS scores are demonstrated in some patients with generalized secondary dystonia but not in others. Larger follow-up studies of DBS for secondary dystonia, focusing on patient age, history, etiology, and patterns of dystonia, are needed to learn which patients will respond best to DBS.

Neuromodulation for dystonia: target and patient selection

Treatment of dystonia refractory to oral medications or botulinum toxin injections includes the use of deep brain stimulation (DBS). Expectations should be established based on patient-related factors, including type of dystonia, genetic cause, target symptoms, age at the time of surgery, disease duration, or the presence of fixed skeletal deformities. Premorbid conditions such as psychiatric illness and cognitive impairment should be considered. Target selection is an emerging issue in DBS for dystonia. Although efficacy has been established for targeting the globus pallidus internus for dystonia, other brain targets such as the subthalamic nucleus, thalamus, or cortex may be promising alternatives.

Bilateral subthalamic nucleus deep brain stimulation for refractory total body dystonia secondary to metabolic autopallidotomy in a 4-year-old boy with infantile methylmalonic acidemia: case report

The methylmalonic acidemias (MMAs) are a group of inborn errors of metabolism resulting in the accumulation of methylmalonic acid in body tissues and fluids. A recognized complication of MMA is bilateral liquefaction of the globus pallidi, resulting in a fulminant total body dystonia of childhood often refractory to medical treatment. This case of total body dystonia due to MMA in a 4-year-old boy had been medically refractory for 15 months. Complete metabolic destructive liquefaction of the pallidi, that is, autopallidotomy, necessitated an alternative, bilateral subthalamic nucleus (STN) target for deep brain stimulation (DBS) with a marked improvement in dystonia and reduction in pain. The case illustrates the efficacy of STN DBS in this condition and the technical challenges in targeting the STN in a small child.

Treatment of classic pantothenate kinase-associated neurodegeneration with deferiprone and intrathecal baclofen

Neurodegeneration with brain iron accumulation (NBIA) describes a heterogeneous family of diseases characterized by high brain iron, particularly in the basal ganglia. The most common manifestation of childhood NBIA is classic pantothenate kinase-associated neurodegeneration (PKAN), a severe, progressive type of autosomal recessive neuroaxonal dystrophy characterized by early onset of symptoms (as opposed to atypical PKAN, with an average age of onset of 14 yrs). There is currently no established therapy for the disease. Intrathecal baclofen has been reported to improve ease of care and dystonia in patients with PKAN. Deferiprone, an iron chelator, has been shown to be safe and tolerable in patients with PKAN as well as effective in reducing brain iron accumulation, as measured by magnetic resonance imaging. This case report highlights the potency of combining intrathecal baclofen and oral deferiprone in a patient with classic PKAN. Although treatment with deferiprone alone was not attempted, this combination therapy seems to be more efficacious than treatment with only intrathecal baclofen.

Pallidal stimulation in children: comparison between cerebral palsy and DYT1 dystonia

The authors compared the outcomes of 17 children aged 7 to 15 years with DYT1 dystonia or cerebral palsy following deep brain stimulation. While patients with cerebral palsy presented with significantly greater motor disability than the DYT1 cohort at baseline, both groups demonstrated improvement at 1 year (cerebral palsy = 24%; DYT1 = 6%). The group as a whole demonstrated significant improvement on the Barry-Albright Dystonia Scale across time. Gains in motor function were apparent in both axial and appendicular distributions involving both upper and lower extremities. Gains achieved by 6 months were sustained in the cerebral palsy group, whereas the DYT1 group demonstrated continued improvement with ongoing pallidal stimulation beyond 18 months. Young patients with dystonia due to cerebral palsy responded comparably to patients with DYT1 dystonia. The severity of motor impairment in patients with cerebral palsy at baseline and follow-up raises the issue of even earlier intervention with neuromodulation in this population to limit long-term motor impairments due to dystonia.

Proportion of life lived with dystonia inversely correlates with response to pallidal deep brain stimulation in both primary and secondary childhood dystonia

AIM

The aim of this study was to examine the impact of dystonia aetiology and duration, contracture, and age at deep brain stimulation (DBS) surgery on outcome in a cohort of children with medically refractory, disabling primary, secondary-static, or secondary-progressive dystonias, including neurodegeneration with brain iron accumulation (NBIA).

METHOD

Dystonia severity was assessed using the Burke-Fahn-Marsden Dystonia Rating Scale (BFMDRS) motor score at baseline and 6 and 12 months postoperatively in a cohort of 70 consecutive children undergoing DBS between June 2005 and July 2011.

RESULTS

Two children (3%) received unilateral DBS for hemidystonia and were excluded and five (7%) developed infections requiring part-DBS removal within 6 months, leaving 63 children (90%) undergoing bilateral DBS for follow-up (34 males, 29 females; mean age at surgery for the whole group 10y 4mo, SD 4y 2mo, range 1-14y). Seventeen children were classified with primary dystonia: mean age 12 years 11 months, SD 4 years 6 months range 4 years 6 months to 17 years 3 months; 28 as having secondary-static dystonia: mean age 10 years 2 months, SD 4 years 9 months (range 3y 3mo-20y); five as having secondary-progressive dystonia: mean age 8 years 11 months, SD 3 years 9 months (range 5y 5mo-13y 1mo); and 13 as having NBIA dystonia: mean age 10 years 2 months, SD 3 years 11 months (range 1-14y). Children with primary dystonias demonstrated greater improvements in BFMDRS motor score than those in the other aetiological categories (Kruskal-Wallis test, p<0.001), which correlated negatively with dystonia duration and more strongly still against the ratio of dystonia duration normalized to age at surgery (DD/AS ratio) at 1 year (Spearman's rank correlation coefficient 0.4752 and -0.599 respectively). A similar significant negative correlation was found in the secondary-static dystonia group between outcome at 1 year and DD/AS ratio (-0.461). Poorer outcome in secondary dystonia coincided with the absence of a period of normal motor development in comparison with the primary dystonia group. A significant improvement in BFMDRS motor score was seen in the NBIA group at 6, but not 12 months (Wilcoxon signed rank test p=0.028, p=0.85 respectively). No reduction in efficacy was seen in children with a musculoskeletal deformity at the time of surgery.

CONCLUSION

Response to pallidal DBS in the treatment of dystonia declines with the proportion of life lived with dystonia in primary and secondary dystonia. Other intrinsic factors reduce the median magnitude of reduction in secondary dystonia after DBS. DBS should be offered early, preferably within 5 years of onset, to maximize benefits and reduce the childhood experience of dystonia, including musculoskeletal deformity. Other multidimensional assessments are required to understand how DBS improves the lives of children with dystonia.

Accuracy of stimulating electrode placement in paediatric pallidal deep brain stimulation for primary and secondary dystonia

BACKGROUND

Accuracy of electrode placement is an important determinant of outcome following deep brain stimulation (DBS) surgery. Data on accuracy of electrode placement into the globus pallidum interna (GPi) in paediatric patients is limited, particularly those with non-primary dystonia who often have smaller GPi. Pallidal DBS is known to be more effective in the treatment of primary dystonia compared with secondary dystonia.

OBJECTIVES

We aimed to determine if accuracy of pallidal electrode placement differed between primary, secondary and NBIA (neuronal degeneration and brain iron accumulation) associated dystonia and how this related to motor outcome following surgery.

METHODS

A retrospective review of a consecutive cohort of children and young people undergoing DBS surgery in a single centre. Fused in frame preoperative planning magnetic resonance imaging (MRI) and postoperative computed tomography (CT) brain scans were used to determine the accuracy of placement of DBS electrode tip in Leskell stereotactic system compared with the planned target. The differences along X, Y, and Z coordinates were calculated, as was the Euclidean distance of electrode tip from the target. The relationship between proximity to target and change in Burke-Fahn-Marsden Dystonia Rating Scale at 1 year was also measured.

RESULTS

Data were collected from 88 electrodes placed in 42 patients (14 primary dystonia, 18 secondary dystonia and 10 NBIA associated dystonia). Median differences between planned target and actual position were: left-side X-axis 1.05 mm, Y-axis 0.85 mm, Z-axis 0.94 mm and Euclidean difference 2.04 mm; right-side X-axis 1.28 mm, Y-axis 0.70 mm, Z-axis 0.70 mm and Euclidean difference 2.45 mm. Accuracy did not differ between left and right-sided electrodes. No difference in accuracy was seen between primary, secondary or NBIA associated dystonia. Dystonia reduction at 1 year post surgery did not appear to relate to proximity of implanted electrode to surgical target across the cohort.

CONCLUSIONS

Accuracy of surgical placement did not differ between primary, secondary or NBIA associated dystonia. Decreased efficacy of pallidal DBS in secondary and NBIA associated dystonia is unlikely to be related to difficulties in achieving the planned electrode placement.

Occipital-C2 transarticular fixation for occipitocervical instability associated with occipitalization of the atlas in patients with klippel-feil syndrome, using intraoperative 3-dimensional navigation system

STUDY DESIGN

Retrospective case series.

OBJECTIVE

The aim of this study was to describe the clinical outcomes of cervical reduction and occipital-C2 transarticular (OCTA) fixation with an assistance of intraoperative 3-dimensional navigation system (ITNS) during the treatment of reducible occipitocervical instability (OCI) in patients with Klippel-Feil syndrome (KFS) with occipitalization of the atlas and fusion of C2-C3.

SUMMARY OF BACKGROUND DATA

Patients with KFS have congenital fusions of at least 2 cervical segments and may gradually develop symptoms at the hypermobile articulations adjacent to the cervical synostosis. This is particularly common in patients with KFS with occipitalization of the atlas and C2-C3 fusion. These patients may be at risk for instability and neurological complications of the occipitocervical junction that require occipitocervical reconstruction and fusion. Numerous treatment techniques are available for this pathological condition. However, there has yet to be a study of reducible OCI, showing successful treatment with intraoperative reduction and posterior OCTA fixation using ITNS.

METHODS

From 2006 to 2011, 9 patients with KFS with reducible OCI attributed to occipitalization of the atlas and C2-C3 fusion were surgically treated. After a limited foramen magnum decompression, reduction of the OCI was conducted by intraoperative cervical traction and extension, followed by OCTA fixation using a direct posterior approach and with the assistance of ITNS. The follow-up period ranged from 6 to 60 months (mean, 31 mo).

RESULTS

Good decompression and bone fusion were achieved in all the patients. The clinical symptoms had improved for all patients. There were no intraoperative or postoperative complications.

CONCLUSION

In patients with KFS with occipitalization of the atlas and C2-C3 fusion, manual cervical traction in tandem with cervical extension, followed by posterior OCTA fixation and fusion provides a safe, effective treatment of OCI and ventral brainstem impingement. IFTN is a feasible tool for monitoring cervical reduction and OCTA screw insertion in patients with KFS with this pathological condition.

High-frequency pallidal stimulation disrupts information flow through the pallidum by GABAergic inhibition

To elucidate the mechanism of deep brain stimulation (DBS) targeting the internal segment of the globus pallidus (GPi), neuronal activity of the GPi and the external segment of the globus pallidus (GPe) was examined during local electrical microstimulation in normal awake monkeys. Single-pulse stimulation of the GPi evoked brief inhibition in neighboring GPi neurons, which was mediated by GABA(A) receptors. High-frequency stimulation of the GPi completely inhibited spontaneous firings of GPi neurons by activation of GABA(A) and GABA(B) receptors. Local single-pulse stimulation directly excited some GPi neurons. Such directly evoked responses were also inhibited by high-frequency stimulation through GABA(A) receptors. In contrast to the GPi, single-pulse and high-frequency stimulation of the GPe induced complex responses composed of GABAergic inhibition and glutamatergic excitation in neighboring GPe neurons. Cortically evoked triphasic responses of GPi neurons were completely inhibited during high-frequency GPi stimulation. These findings suggest that GPi-DBS dissociates inputs and outputs in the GPi by intense GABAergic inhibition and disrupts information flow through the GPi.

Neuromodulation and Palliative Medicine

The palliative care population is generally vulnerable to experiencing medication-induced adverse effects and drug–drug interactions. Neuromodulation may offer particular advantages over systemic medications in this population. Spinal cord stimulation and peripheral nerve stimulation have long been utilized in efforts to provide analgesia for various painful conditions. More recently, deep brain stimulation/motor cortex stimulation has anecdotally been utilized for certain intractable pain states. Although brain electrical stimulation has not been adequately trialed or in some cases even tried at all for management of a variety of symptoms, it is conceivable that in the future it may be a potential therapeutic option in efforts to palliate various severe refractory symptoms (eg, intractable pain, nausea, dyspnea, delirium).

Occipitocervical fusion using a contoured rod and wire construct in children: a reappraisal of a vintage technique

OBJECT

Many methods to stabilize and fuse the craniocervical junction have been described. One of the early designs was a contoured (Luque) rod fixated with wires, the so-called Hartshill-Ransford loop. In this study, the authors report their 20-year experience with this surgical technique in children.

METHODS

The authors reviewed the medical records of patients 18 years of age or younger who underwent dorsal occipitocervical fusion procedures between March 1992 and March 2012 at Le Bonheur Children's Hospital using a contoured rod and wire construct. Data on basic patient characteristics, causes of instability, neurological function at presentation and at last follow-up, details of surgery, complications, and radiographic outcome were collected.

RESULTS

Twenty patients (11 male) were identified, with a mean age of 5.5 years (range 1-18 years) and a median follow-up of 43.5 months. Fourteen patients had atlantooccipital dislocation, 2 patients had atlantoaxial fracture-dissociations, 2 had Down syndrome with occipitocervical and atlantoaxial instability, 1 had an epithelioid sarcoma from the clivus to C-2, and 1 had an anomalous atlas with resultant occipitocervical instability. Surgical stabilization extended from the occiput to C-1 in 3 patients, C-2 in 6, C-3 in 8, and to C-4 in 3. Bone morphogenetic protein was used in 2 patients. Two patients were placed in a halo orthosis; the rest were kept in a hard collar for 6-8 weeks. All patients were neurologically stable after surgery. One patient with a dural tear experienced wound dehiscence with CSF leakage and required reoperation. Eighteen patients went on to achieve fusion within 6 months of surgery; 1 patient was initially lost to follow-up, but recent imaging demonstrated a solid fusion. There were no early hardware or bone failures requiring hardware removal, but radiographs obtained 8 years after surgery showed that 1 patient had an asymptomatic fractured rod. There were no instances of symptomatic junctional degeneration, and no patient was found to have increasing lordosis over the fused segments. Five (31%) of the 16 trauma patients required a shunt for hydrocephalus.

CONCLUSIONS

Despite the proliferation of screw-fixation techniques for craniocervical instability in children, the contoured rod-wire construct remains an effective, less expensive, and technically easier alternative that has been in use for almost 30 years. It confers immediate stability, and therefore most patients will not need to be placed in a halo device postoperatively. A secondary observation in our series was the high (30%) rate of hydrocephalus requiring a shunt in patients with traumatic instability.

Deep brain stimulation for dystonia

The few reported controlled studies show that bilateral stimulation of the globus pallidus interna (GPi) is a safe and effective long-term treatment for hyperkinetic disorders. However, the recently published data on deep brain stimulation (DBS) applied to different targets or patients (especially those with secondary dystonia) are mainly uncontrolled case reports, precluding a clear determination of its efficacy, and providing little guidance as to the choice of a "good" target in a "good" patient. This chapter reviews the literature on DBS in primary dystonia, paying particular attention to the risk:benefit ratio in focal and segmental dystonias (cervical dystonia, cranial dystonia) and to the predictive factors for a good outcome. The chapter also highlights recent data on the marked benefits of the technique in myoclonus dystonia (in which pallidal, as opposed to thalamic, stimulation is more effective) and in tardive dystonia-dyskinesia. Although, the decision to treat appears relatively straightforward in patients with primary dystonia, myoclonus-dystonia, and tardive dystonia who have a normal findings on magnetic resonance imaging and normal cognitive function, there are still no reliable tools to help predict the timescale of postoperative benefit. This chapter provides a comprehensive analysis of the use of the treatment in various types of secondary dystonia, with little to moderate benefit in most cases, based on single cases or small series. Beyond the reduction in the severity of dystonia, the global motor and functional outcome is difficult to determine owing to the paucity of adequate evaluation tools. Because of the large interpatient variability, different targets may be effective depending on the symptoms in each individual.

Outcomes of instrumented fusion in the pediatric cervical spine

Object

The most common cause of cervical spine arthrodesis in the pediatric population is instability related to congenital or traumatic pathology. Instrumenting the cervical spine can be challenging given smaller anatomical structures, less ossified bone, and future growth potential and development. Studies in adult patients have suggested that using screw constructs results in improved outcomes with lower rates of instrumentation failure. However, the pediatric literature is limited to small retrospective series. Based on a review of the literature and their own patient series, the authors report that instrumenting the pediatric cervical spine with screw constructs may be safer and more effective than using wiring techniques.

Methods

The authors reviewed the existing pediatric cervical spine arthrodesis literature and contributed 31 of their own cases from September 1, 2007, to January 1, 2011. They reviewed 204 abstracts from January 1, 1966, to December 31, 2010, and 80 manuscripts with 883 total patients were included in the review. They recorded demographic, radiographic, and outcomes data—as well as surgical details—with a focus on fusion rates and complications.

Patients were then grouped into categories based upon the procedure performed: 1) patients who underwent fusions bridging the occipitocervical junction and 2) patients who underwent fusion of the cervical spine that did not include the occiput, thus including atlantoaxial and subaxial fusions. Patients were further subdivided according to the type of instrumentation used—some had posterior cervical fusion with wiring (with or without rod implantation); others had posterior cervical fusion with screws.

Results

The entire series comprised 914 patients with a mean age of 8.30 years. Congenital abnormalities were encountered most often (in 55% of cases), and patients had a mean follow-up of 32.5 months. From the entire cohort, 242 patients (26%) experienced postsurgical complications, and 50 patients (5%) had multiple complications. The overall fusion rate was 94.4%.

For occipitocervical fusions (N = 285), both screw and wiring groups had very high fusion rates (99% and 95%, respectively, p = 0.08). However, wiring was associated with a higher complication rate. From a sample of 252 patients, 14% of those treated with screw instrumentation had complications, compared with 50% of patients treated with wiring (p < 0.05).

In cervical fusions not involving the occipitocervical junction (N = 181), screw constructs had a 99% fusion rate, whereas wire instrumentation only had an 83% fusion rate (p < 0.05). Similarly, patients who underwent screw fixation had a lower complication profile (15%) when compared with those treated with wiring constructs (54%, p < 0.05).

Conclusions

The results of this study are limited by variations in construct design, use of orthoses, follow-up duration, and newer adjuvant products promoting fusions. However, a literature review and the authors' own series of pediatric cases suggest that instrumentation of the cervical spine in children may be safer and more efficacious using screw constructs rather than wiring techniques.

The influence of deep brain stimulation intensity and duration on symptoms evolution in an OFF stimulation dystonia study

BACKGROUND

Deep brain stimulation (DBS) of the internal globus pallidus (GPi) is an established therapy for primary generalized dystonia. However, the evolution of dystonia symptoms after DBS discontinuation after years of therapy has only rarely been reported. We therefore longitudinally studied the main physiological measurements known to be impaired in dystonia, with DBS ON and then again after termination of DBS, after at least five years of continuous DBS.

OBJECTIVE

We studied whether dystonia evolution after DBS discontinuation in patients benefiting from long-term GPi DBS is different from that observed in earlier stages of the therapy.

METHODS

In eleven DYT1 patients treated with bilateral GPi DBS for at least 5 years, dystonia was assessed ON-DBS, immediately after switch-off (OFF-DBS1) and 48 h after DBS termination (OFF-DBS2). We studied the influence of DBS intensity on dystonia when DBS was discontinued.

RESULTS

On average a significant difference in symptoms was measured only between ON-DBS and OFF-DBS1 conditions. Importantly, none of the patients returned to their preoperative dystonia severity, even 48 h after discontinuation. The amount of clinical deterioration in the OFF conditions positively correlated with higher stimulation current in the chronic ON-DBS condition.

CONCLUSIONS

The duration of DBS application influences symptom evolution after DBS termination. DBS intensity seems to have a prominent role on evolution of dystonic symptoms when DBS is discontinued. In conclusion, DBS induces changing modulation of the motor network with less worsening of symptoms after long term stimulation, when DBS is stopped.

Deep Brain Stimulation of the Globus Pallidus in a 7-Year-Old Girl with DYT1 Generalized Dystonia

The experience of pediatric deep brain stimulation (DBS) of the globus pallidus internus (GPi) in the treatment of early-onset DYT1 generalized dystonia is still limited. Here, we report the surgical experience of bilateral GPi-DBS under general anesthesia by using microelectrode recording in a 7-year-old girl with early-onset DYT1 generalized dystonia. Excellent improvement of her dystonia without neurological complications was achieved. This case report demonstrates that GPi-DBS is an effective and safe method for the treatment of medically refractory early-onset DYT1 generalized dystonia in children.

Beyond the Burke-Fahn-Marsden Dystonia Rating Scale: deep brain stimulation in childhood secondary dystonia

PURPOSE

Deep brain stimulation is now widely accepted as an effective treatment for children with primary generalized dystonia. More variable results are reported in secondary dystonias and its efficacy in this heterogeneous group has not been fully elucidated. Deep brain stimulation outcomes are typically reported using impairment-focused measures, such as the Burke-Fahn-Marsden Dystonia Rating Scale, which provide little information about function and participation outcomes or changes in non-motor areas. The aim is to demonstrate that in some cases of secondary dystonia, the sole use of impairment level measures, such as the Burke-Fahn-Marsden Dystonia Rating Scale, may be insufficient to fully evaluate outcome following deep brain stimulation.

METHODS

Six paediatric cases who underwent deep brain stimulation surgery with a minimum of one year follow up were selected on the basis of apparent non-response to deep brain stimulation, defined as a clinically insignificant change in the Burke-Fahn-Marsden Dystonia Movement Scale (<20%), but where other evaluation measures demonstrated clinical efficacy across several domains.

RESULTS

Despite no significant change in Burke-Fahn-Marsden Dystonia Rating Scale scores following deep brain stimulation, parallel outcome measures demonstrated significant benefit in a range of child and family-centred goal areas including: pain and comfort, school attendance, seating tolerance, access to assistive technology and in some cases carer burden.

CONCLUSIONS

Sole use of impairment-focused measures, are limited in scope to evaluate outcome following deep brain stimulation, particularly in secondary dystonias. Systematic study of effects across multiple dimensions of disability is needed to determine what deep brain stimulation offers patients in terms of function, participation, care, comfort and quality of life. Deep brain stimulation may offer meaningful change across multiple domains of functioning, disability and health even in the absence of significant change in dystonia rating scales.

Complex Chiari malformations in children: an analysis of preoperative risk factors for occipitocervical fusion

OBJECT

Chiari malformation Type I (CM-I) is a congenital anomaly often treated by decompressive surgery. Patients who fail to respond to standard surgical management often have complex anomalies of the craniovertebral junction and brainstem compression, requiring reduction and occipitocervical fusion. The authors hypothesized that a subgroup of "complex" patients defined by specific radiographic risk factors may have a higher rate of requiring occipitocervical fusion.

METHODS

A retrospective review was conducted of clinical and radiographic data in pediatric patients undergoing surgery for CM-I between 1995 and 2010. The following radiographic criteria were identified: scoliosis, syringomyelia, CM Type 1.5, medullary kinking, basilar invagination, tonsillar descent, craniocervical angulation (clivoaxial angle [CXA] < 125°), and ventral brainstem compression (pB-C2 ≥ 9 mm). A multivariate Cox regression analysis was used to determine the independent association between occipitocervical fusion and each variable.

RESULTS

Of the 206 patients who underwent CM decompression with or without occipitocervical fusion during the study period, 101 had preoperative imaging available for review and formed the study population. Mean age at surgery was 9.1 years, and mean follow-up was 2.3 years. Eighty-two patients underwent suboccipital decompression alone (mean age 8.7 years). Nineteen patients underwent occipitocervical fusion (mean age 11.1 years), either as part of the initial surgical procedure or in a delayed fashion. Factors demonstrating a significantly increased risk of requiring fusion were basilar invagination (HR 9.8, 95% CI 2.2-44.2), CM 1.5 (HR 14.7, 95% CI 1.8-122.5), and CXA < 125° (HR 3.9, 95% CI 1.2-12.6).

CONCLUSIONS

Patients presenting with basilar invagination, CM 1.5, and CXA < 125° are at increased risk of requiring an occipitocervical fusion procedure either as an adjunct to initial surgical decompression or in a delayed fashion. Patients and their families should be counseled in regard to these findings as part of a preoperative CM evaluation.

Toward a network model of dystonia

Dystonia has generally been considered a basal ganglia (BG) disorder. Early models hypothesized that dystonia occurred as the result of reduced mean discharge rates in the internal segment of the globus pallidus (GPi). Increasing evidence suggests a more systemwide disruption of the basal ganglia thalamic circuit (BGTC) resulting in altered firing patterns, synchronized oscillations, and widened receptive fields. A model of dystonia incorporating these changes within the BGTC is presented in which we postulate that this pathophysiology arises from disruptions within the striatum. Alterations in the cerebellothalamocortical (CBTC) pathway to the development of dystonia may also play a role. However, the contribution of CBTC abnormalities to dystonia remains unclear and may vary with different etiologies of dystonia. Finally, the relevance of established and emerging theories related to the pathophysiology of dystonia is addressed within the context of improving conventional approaches for deep brain stimulation (DBS) treatment strategies.

Battery life following pallidal deep brain stimulation (DBS) in children and young people with severe primary and secondary dystonia

BACKGROUND

The finite life of non-rechargeable batteries powering implantable pulse generators (IPG) necessitates their periodic replacement. Children receiving deep brain stimulation (DBS) may require frequent battery changes over their treatment lifetime.

OBJECTIVES

We aimed to determine the battery life of IPGs used in pallidal DBS for the treatment of dystonia in children and young people.

METHODS

We make use of a review of case notes of all children and young people undergoing DBS surgery at our institution from June 2005 to May 2010.

RESULTS

A total of 54 children and young people underwent surgery on at least one occasion, with a total of 76 IPGs implanted. Replacement IPGs due to battery failure were required in 15 out of 54 (27.8%). The average time to battery failure was 24.5 ± 2.9 months (95% confidence interval), with a range of 13-39 months. Battery life was significantly longer in primary compared to subsequent IPGs. No difference in longevity was seen between different IPG devices.

CONCLUSIONS

IPG battery life may be short in children and young people receiving treatment for dystonia. These findings highlight the potential benefits of the recently introduced rechargeable neurostimulators.

Current and future medical treatment in primary dystonia

Dystonia is a hyperkinetic movement disorder, characterized by involuntary and sustained contractions of opposing muscles causing twisting movements and abnormal postures. It is often a disabling disorder that has a significant impact on physical and psychosocial wellbeing. The medical therapeutic armamentarium used in practice is quite extensive, but for many of these interventions formal proof of efficacy is lacking. Exceptions are the use of botulinum toxin in patients with cervical dystonia, some forms of cranial dystonia (in particular, blepharospasm) and writer's cramp; deep brain stimulation of the pallidum in generalized and segmental dystonia; and high-dose trihexyphenidyl in young patients with segmental and generalized dystonia. In order to move this field forward, we not only need better trials that examine the effect of current treatment interventions, but also a further understanding of the pathophysiology of dystonia as a first step to design and test new therapies that are targeted at the underlying biologic and neurophysiologic mechanisms.

Frequency-dependent effects of electrical stimulation in the globus pallidus of dystonia patients

Deep brain stimulation (DBS) in the globus pallidus internus (GPi) has been shown to improve dystonia, a movement disorder of repetitive twisting movements and postures. DBS at frequencies above 60 Hz improves dystonia, but the mechanisms underlying this frequency dependence are unclear. In patients undergoing dual-microelectrode mapping of the GPi, microstimulation has been shown to reduce neuronal firing, presumably due to synaptic GABA release. This study examined the effects of different microstimulation frequencies (1–100 Hz) and train length (0.5–20 s), with and without prior high-frequency stimulation (HFS) on neuronal firing and evoked field potentials (fEPs) in 13 dystonia patients. Pre-HFS, the average firing decreased as stimulation frequency increased and was silenced above 50 Hz. The average fEP amplitudes increased up to frequencies of 20–30 Hz but then declined and at 50 Hz, were only at 75% of baseline. In some cases, short latency fiber volleys and antidromic-like spikes were observed and followed high frequencies. Post-HFS, overall firing was reduced compared with pre-HFS, and the fEP amplitudes were enhanced at low frequencies, providing evidence of inhibitory synaptic plasticity in the GPi. In a patient with DBS electrodes already implanted in the GPi, recordings from four neurons in the subthalamic nucleus showed almost complete inhibition of firing with clinically effective but not clinically ineffective stimulation parameters. These data provide additional support for the hypothesis of stimulation-evoked GABA release from afferent synaptic terminals and reduction of neuronal firing during DBS and additionally, implicate excitation of GPi axon fibers and neurons and enhancement of inhibitory synaptic transmission by high-frequency GPi DBS as additional putative mechanisms underlying the clinical benefits of DBS in dystonia.

Anesthetic considerations for awake craniotomy for epilepsy and functional neurosurgery

The two most common neurosurgical procedures that call for an awake patient include epilepsy surgery and functional neurosurgery. Monitoring patients in the awake state allows more aggressive resection of epileptogenic foci in functionally important brain regions. Careful patient selection and preparation combined with attentive monitoring and anticipation of events are fundamental to a smooth awake procedure. Current pharmacologic agents and techniques at the neuroanesthesiologist's disposal facilitate an increasing number of procedures performed in awake patients.

High-frequency pallidal stimulation for camptocormia in Parkinson disease: case report

BACKGROUND AND IMPORTANCE

Camptocormia is characterized by abnormal flexion of the thoracolumbar spine that increases during upright posture and abates in the recumbent position and has been reported to occur in patients with Parkinson disease. Camptocormia causes significant spinal and abdominal pain, impairment of balance, and social stigma.

CLINICAL PRESENTATION

A 57-year-old woman with Parkinson disease developed severe camptocormia, which did not improve with trials of antiparkinsonian and muscle relaxant medications. The patient was successfully treated with bilateral globus pallidus interna deep brain stimulation surgery under general anesthesia. High-frequency neuromodulation afforded relief of camptocormia and improvement in Parkinson disease symptoms.

CONCLUSION

Camptocormia in Parkinson disease may represent a form of dystonia and can be treated effectively with chronic pallidal neuromodulation.

Staged implantation of multiple electrodes in the internal globus pallidus in the treatment of primary generalized dystonia

Object

Deep brain stimulation (DBS) is used for treating various types of dystonia. Multiple electrodes could be proposed to improve the therapeutic outcome enabling the targeting of specific neuronal populations not reached by the electrical field generated by the initially implanted electrode. The authors address the question of the feasibility and safety of staged multiple lead implantations in the sensorimotor internal globus pallidus (GPi) in primary generalized dystonia (PGD). Criteria for patient selection, surgical technique, target selection, electrical settings management, and clinical outcome are presented.

Methods

Sixteen patients (8 harbored the DYT1 gene mutation) presented with PGD and were enrolled in this study. Patients underwent clinical assessment using the Burke-Fahn-Marsden Dystonia Rating Scale preoperatively and during follow-up with DBS. Prior to the addition of electrodes, the authors confirmed, by turning off stimulation, that the patient was still benefiting from DBS and that DBS settings adjustment did not provide further improvement. The second target was defined according to the position of the first electrode, to the residual volume within the sensorimotor GPi, and according to residual symptoms. The second surgery followed the same protocol as the first and the new electrode were inserted using the same bur hole as the first electrode.

Results

The addition of a new pair of electrodes was followed by significant improvement in the whole population (p = 0.005), as well as in the DYT1-negative subgroup (p = 0.012) but not in the DYT1 subgroup (p = not significant). Nevertheless, some patients did not exhibit significant additional benefit. Seven hardware-related complications occurred during the entire follow-up, 3 prior to it, and 4 after the addition of the second pair of electrodes.

Conclusions

The addition of a second pair of electrodes in the GPi in patients with PGD with suboptimal or decaying benefit following the first surgery seems to be a safe procedure and is not followed by an increase in surgery-related complications. This staged procedure may provide further clinical improvement in patients with PGD in whom DBS effect is initially incomplete or when disease progression occurs over time. The position of the additional electrode within the GPi is determined by the available volume within the posteroventral GPi and by the distribution of the dystonic symptoms that need to be controlled.

Five-year follow-up of 10 patients treated with globus pallidus internus deep brain stimulation for segmental or multisegmental dystonia

INTRODUCTION

Globus pallidus internus (GPi) deep brain stimulation (DBS) represents a validated, effective, and safe treatment for patients affected by generalized dystonia resistant to conservative treatment. Segmental and multisegmental dystonia have more recently been proposed as further indications for GPi DBS despite the lack of long-term homogenous follow-up. Here we present an original and detailed long-term follow-up (5 years) of a homogeneous population of 11 patients affected by segmental or multisegmental dystonia.

MATERIALS AND METHODS

Ten patients underwent bilateral GPi DBS electrode implantations under a Leksell stereotactic guide, with intraoperative neurophysiological monitoring. The follow-ups at 1, 3 and 5 years were collected using video-BFMDRS for motor and disability scores. The statistical analysis of the results is provided.

RESULTS

We reported a statistically significant improvement in motor and disability overall scores until 5 years after treatment. At the last follow-up, even the single motor subitems were statistically improved.

DISCUSSION

We observed a continuous and statistically significant improvement in all of the motor subitems and in the overall disability score until the 3-year follow-up. These results did not improve any further but they appeared steady at the last follow-up. We also report a significant improvement in the cranial-cervical subitems.

CONCLUSIONS

GPi DBS should definitely be considered a safe and effective treatment also for segmental and multisegmental dystonia even in cases of relevant or prevalent cranial-cervical involvement.

Deep brain stimulation in children with dystonia: experience from a tertiary care center

OBJECTIVE

To investigate the efficacy and safety of deep brain stimulation (DBS) of the globus pallidus internus (GPi) in children with dystonia.

METHODS

Retrospective chart review of patients (≤21 years) with dystonia who underwent GPi DBS. Outcome measures were assessed by the Burke-Fahn-Marsden Dystonia Rating (BFMDR) movement and disability scales pre- and post-DBS.

RESULTS

Eight patients underwent DBS; mean age of onset was 7.5 ± 4.8 years (7 were male). Mean age at DBS was 14.1 ± 4.6 years. Etiology of dystonia was primary in 6 patients and secondary in 2. There was significant improvement of BFMDR movement as well as BFMDR disability scales in 6 patients with primary dystonia with modest improvement in those scales in 2 patients with secondary dystonia. Hardware-related problems were observed in 2 and infection was noted in 1.

CONCLUSIONS

GPi DBS is an effective and safe therapy in pediatric patients with primary as well as selected cases of secondary dystonia.

Reducing hemorrhagic complications in functional neurosurgery: a large case series and systematic literature review

Object

Hemorrhagic complications carry by far the highest risk of devastating neurological outcome in functional neurosurgery. Literature published over the past 10 years suggests that hemorrhage, although relatively rare, remains a significant problem. Estimating the true incidence of and risk factors for hemorrhage in functional neurosurgery is a challenging issue.

Methods

The authors analyzed the hemorrhage rate in a consecutive series of 214 patients undergoing imageguided deep brain stimulation (DBS) lead placement without microelectrode recording (MER) and with routine postoperative MR imaging lead verification. They also conducted a systematic review of the literature on stereotactic ablative surgery and DBS over a 10-year period to determine the incidence and risk factors for hemorrhage as a complication of functional neurosurgery.

Results

The total incidence of hemorrhage in our series of image-guided DBS was 0.9%: asymptomatic in 0.5%, symptomatic in 0.5%, and causing permanent deficit in 0.0% of patients. Weighted means calculated from the literature review suggest that the overall incidence of hemorrhage in functional neurosurgery is 5.0%, with asymptomatic hemorrhage occurring in 1.9% of patients, symptomatic hemorrhage in 2.1% and hemorrhage resulting in permanent deficit or death in 1.1%. Hypertension and age were the most important patient-related factors associated with an increased risk of hemorrhage. Risk factors related to surgical technique included use of MER, number of MER penetrations, as well as sulcal or ventricular involvement by the trajectory. The incidence of hemorrhage in studies adopting an image-guided and image-verified approach without MER was significantly lower than that reported with other operative techniques (p < 0.001 for total number of hemorrhages, p < 0.001 for asymptomatic hemorrhage, p < 0.004 for symptomatic hemorrhage, and p = 0.001 for hemorrhage leading to permanent deficit; Fisher exact test).

Conclusions

Age and a history of hypertension are associated with an increased risk of hemorrhage in functional neurosurgery. Surgical factors that increase the risk of hemorrhage include the use of MER and sulcal or ventricular incursion. The meticulous use of neuroimaging—both in planning the trajectory and for target verification—can avoid all of these surgery-related risk factors and appears to carry a significantly lower risk of hemorrhage and associated permanent deficit.

Deep brain stimulation in children: experience and technical pearls

OBJECT

Deep brain stimulation (DBS) is an established technique for the treatment of several movement disorders in adults. However, the technical approach, complications, and results of DBS in children have not been well documented.

METHODS

A database of DBS implantations performed at a single institution, prospectively established in 1998, was reviewed for patients who received DBS prior to the age of 18. Diagnoses, surgical technique, and complications were noted. Outcomes were assessed using standard rating scales of neurological function.

RESULTS

Of 815 patients undergoing DBS implantation over a 12-year period, 31 were children (mean age at surgery 13.2 years old, range 4-17 years old). Diagnoses included the following: DYT1 primary dystonia (autosomal dominant, Tor1AΔGAG mutation, 10 cases), non-DYT1 primary dystonia (3 cases), secondary dystonia (11 cases), neurodegeneration with brain iron accumulation (NBIA, 3 cases), levodopa-responsive parkinsonism (2 cases), Lesch-Nyhan disease (1 case), and glutaric aciduria Type 1 (1 case). Six children ages 15-17 years old underwent awake microelectrode-guided surgery. For 25 children operated under general anesthesia, the surgical technique evolved from microelectrode-guided surgery to image-guided surgeries using real-time intraoperative MR imaging or CT for lead location confirmation. Complications included 5 hardware infections, all in children younger than 10 years old. At 1 year after implantation, patients with DYT1 dystonia had a mean improvement in the Burke-Fahn-Marsden Dystonia Rating Scale movement subscore of 75%, while those with secondary dystonia had only small improvements. Outcomes in the 3 children with NBIA were disappointing.

CONCLUSIONS

Results of DBS in children with primary and secondary dystonias were similar to those in adults, with excellent results for DYT1 dystonia in children without fixed orthopedic deformity and much more modest results in secondary dystonia. In contrast to reported experience in adults with NBIA, these results in children with NBIA were poor. Infection risk was highest in the youngest patients.

Good long-term efficacy of pallidal stimulation in cervical dystonia: a prospective, observer-blinded study

BACKGROUND AND PURPOSE

Deep brain stimulation of the internal globus pallidus (GPi-DBS) is established as an effective treatment of primary generalised dystonia in controlled studies. In cervical dystonia (CD), only one previous study has reported observer-blinded outcome assessment of long-term GPi-DBS, with 1-year follow-up.

METHODS

In this prospective, single-centre study, eight patients with CD (7 women:1 man, 4 focal:4 segmental) treated with bilateral GPi-DBS for median (range) 30 (12-48) months, were evaluated by the Toronto Western Spasmodic Torticollis Rating Scale (TWSTRS; Severity, Disability and Pain scores), the Short-Form Health Survey-36 (SF-36), and the Becks Depression Index in an open design. In addition, a blinded rater assessed the TWSTRS Severity score from videos obtained preoperatively and at the last follow-up.

RESULTS

In the blinded evaluation, median (range) TWSTRS Severity score improved from 25 (19-30) to 8 (4-23) (P = 0.028), thus a 70% (23-82) score reduction. In the open evaluation, median Severity score improvement at the last follow-up was 73%, representing a significant further improvement from 50% at 6 months. The Disability and Pain scores improved by median 91% and 92%, respectively, and the SF-36 subdomain scores improved significantly. A reversible right hemiparesis and aphasia occured in one patient 4 days postoperatively, because of reversible oedema around the left electrode. No other serious adverse effects and no permanent morbidity were observed.

CONCLUSIONS

This single-blinded study shows good long-term efficacy of GPi-DBS in CD patients and supports using this treatment in those who have insufficient response to medical treatment.

Early postoperative management of DBS in dystonia: programming, response to stimulation, adverse events, medication changes, evaluations, and troubleshooting

Early postoperative management in deep brain stimulation-treated patients with dystonia differs from that of patients with essential tremor and Parkinson's disease, mainly due to the usually delayed effects of deep brain stimulation and the heterogenous clinical manifestation and etiologies of dystonia. The present chapter summarizes the available data about and concentrates on practical clinical aspects of early postoperative management in deep brain stimulation-treated patients with dystonia.

Long-Term management of DBS in dystonia: response to stimulation, adverse events, battery changes, and special considerations

Multiple independent case series have documented sustained benefit of bilateral pallidal deep brain stimulation (DBS) up to 3 years in patients with primary dystonia. Growing evidence exists for positive outcomes extending up to 10 years. The beneficial effects from DBS are usually reported to be stable, thus requiring little long-term modifications of the parameters of stimulation. Speech and swallowing abnormalities are less responsive than other dystonic symptoms. Symptom exacerbation after initial benefit has been reported in a few cases. It is not known whether this is related to potential tolerance or habituation to stimulation or to progression of the underlying disease. Failures of pallidal DBS, at least in primary dystonia patients, should not be accepted without further re-evaluation of each individual case, including possible revisions of the electrode location. Both hardware- and stimulation-related adverse effects, including insufficient relief of speech function, have been reported in the long-term. Despite early reports suggesting that hardware problems might be more frequent in dystonia, more recent studies did not confirm these observations. In patients with severe segmental (e.g., axial) or generalized dystonia, sudden cessation of stimulation may become a medical emergency and should be anticipated changing the neurostimulator before its natural end of life.

Inclusion and exclusion criteria for DBS in dystonia

When considering a patient with dystonia for deep brain stimulation (DBS) surgery several factors need to be considered. Level B evidence has shown that all motor features and associated pain in primary generalized and segmental dystonia are potentially responsive to globus pallidus internus (GPi) DBS. However, improvements in clinical series of ≥ 90% may reflect methods that need improvement, and larger prospective studies are needed to address these factors. Nevertheless, to date the selection criteria for DBS-specifically in terms of patient features (severity and nature of symptoms, age, time of evolution, or any other demographic or disease aspects)--have not been assessed in a systematic fashion. In general, dystonia patients are not considered for DBS unless medical therapies have been previously and extensively tested. The vast majority of reported patients have had DBS surgery when the disease was provoking important disability, with loss of independence and impaired quality of life. There does not appear to be an upper age limit or a minimum age limit, although there are no published data regarding the outcome of GPi DBS for dystonia in children younger than 7 years of age. There is currently no enough evidence to prove that subjects with primary--generalized dystonia who undergo DBS at an early age and sooner rather than later after disease onset may gain more benefit from DBS than those undergoing DBS after the development of fixed skeletal deformities. There is no enough evidence to refuse or support consideration of DBS in patients with previous ablative procedures.

Chronic bilateral pallidal stimulation in patients with generalized primary dystonia - multi-contact cathodal stimulation is superior to bipolar stimulation mode. Preliminary results

BACKGROUND AND PURPOSE

Primary generalized dystonia (PGD) is a medically refractory progressive disease of the brain causing near total handicap of affected patients. The aim of the study was to assess the efficacy and safety of bilateral pallidal stimulation in patients with PGD.

MATERIAL AND METHODS

The study population is composed of 5 patients with PGD. The formal objective assessment included the Burke-Fahn-Marsden dystonia rating scale (BFMDRS). All stereotactic procedures were performed in general anaesthesia using a Leksell G stereotactic head frame without electrophysiological guidance. Immediately after insertion of deep brain stimulation (DBS) leads, the internal pulse generators (Itrel II or Soletra) were implanted subcutaneously in the chest wall or abdominal region.

RESULTS

There were no complications related to the stereotactic procedures. The hardware-related complications (two broken DBS leads) were replaced successfully. There were no infections or erosions of implanted hardware. It has been observed that in the long-term follow-up period primary set bipolar stimulation mode lost its benefit achieved previously. Various stimulation combinations were investigated. Monopolar cathodal or especially multi-contact cathodal stimulation was the most effective one. The efficacy of bilateral pallidal stimulation was proved by the objective validated BFMDRS at long-term follow-up.

CONCLUSIONS

Response to DBS may improve with the number of activated cathodal contacts within the globus pallidus internus.

Shaping reversibility? Long-term deep brain stimulation in dystonia: the relationship between effects on electrophysiology and clinical symptoms

Long-term results show that benefits from chronic deep brain stimulation in dystonia are maintained for many years. Despite this, the neurophysiological long-term consequences of treatment and their relationship to clinical effects are not well understood. Previous studies have shown that transcranial magnetic stimulation measures of abnormal long-term potentiation-like plasticity (paired associative stimulation) and GABAa-ergic inhibition (short-interval intracortical inhibition), which are seen in dystonia, normalize after several months of deep brain stimulation. In the present study, we examine the same measures in a homogenous group of 10 DYT1 gene-positive patients after long-term deep brain stimulation treatment for at least 4.5 years. Recordings were made 'on' deep brain stimulation and after stopping deep brain stimulation for 2 days. The results show that: (i) on average, prior to discontinuing deep brain stimulation, the paired associative stimulation response was almost absent and short-interval intracortical inhibition was reduced compared with normal. This pattern differs from that in both healthy volunteers and from the typical pattern of enhanced plasticity and reduced inhibition seen in deep brain stimulation-naïve dystonia. It is similar to that seen in untreated Parkinson's disease and may relate to thus far unexplained clinical phenomena like parkinsonian symptoms that have sometimes been observed in patients treated with deep brain stimulation. (ii) Overall, there was no change in average physiological or clinical status when deep brain stimulation was turned off for 2 days, suggesting that deep brain stimulation had produced long-term neural reorganization in the motor system. (iii) However, there was considerable variation between patients. Those who had higher levels of plasticity when deep brain stimulation was 'on', had the best retention of clinical benefit when deep brain stimulation was stopped and vice versa. This may indicate that better plasticity is required for longer term retention of normal movement when deep brain stimulation is off. (iv) Patients with the highest plasticity 'on' deep brain stimulation were those who had been receiving stimulation with the least current drain. This suggests that it might be possible to 'shape' deep brain stimulation of an individual patient to maximize beneficial neurophysiological patterns that have an impact on clinical status. The results are relevant for understanding long-term consequences and management of deep brain stimulation in dystonia.

Chiari malformation Type I and syrinx in children undergoing magnetic resonance imaging

OBJECT

Chiari malformation Type I (CM-I) with an associated spinal syrinx is a common pediatric diagnosis. A better understanding of the relative age-related prevalence and MR imaging characteristics of these associated conditions may lead to improved treatment decisions.

METHODS

The authors performed a retrospective review of 14,116 consecutive individuals 18 years of age or younger who had undergone brain or cervical spine MR imaging at the University of Michigan between November 1997 and August 2008. In the patients with CM-I, demographic, clinical, and radiographic information was recorded.

RESULTS

Five hundred nine children (3.6%) with CM-I were identified. Among these patients, 23% also had a spinal cord syrinx, and 86% of the syringes were found in the cervical spine. The MR imaging prevalence of CM-I with a syrinx was 1.2% in girls and 0.5% in boys (p < 0.0001). The severity of impaired CSF flow at the foramen magnum was associated with the amount of tonsillar herniation (p < 0.0001) and conformation of the tonsils (p < 0.0001). Patients with CM-I were treated surgically in 35% of cases; these patients exhibited more severe tonsillar herniation (p < 0.0001) and impaired CSF flow (p < 0.0001) as compared with those who did not undergo surgery. On imaging, 32% of all the patients with CM-I were considered symptomatic by the treating physician. Patients were more likely to be considered symptomatic if they were female, had a syrinx, displayed abnormal tonsillar pulsations, or had a greater amount of tonsillar herniation.

CONCLUSIONS

In this study the authors describe the age-related prevalence and MR imaging characteristics of CM-I and its association with a syrinx and other abnormalities in a large group of children who underwent MR imaging for any indication. Syringes are more common in older children, in girls, and in patients with a greater degree of tonsillar descent and CSF flow impairment.