Initial experience with magnetic resonance-guided focused ultrasound stereotactic surgery for central brain lesions in young adults

OBJECTIVE

Magnetic resonance-guided focused ultrasound (MRgFUS) is an incisionless procedure capable of thermoablation through the focus of multiple acoustic beams. Although MRgFUS is currently approved for the treatment of tremor in adults, its safety and feasibility profile for intracranial lesions in the pediatric and young adult population remains unknown.

METHODS

The long-term outcomes of a prospective single-center, single-arm trial of MRgFUS at Nicklaus Children's Hospital in Miami, Florida, are presented. Patients 15-22 years of age with centrally located lesions were recruited, clinically consistent with WHO grade I tumors that require surgical intervention. This cohort consisted of 4 patients with hypothalamic hamartoma (HH), and 1 patient with tuberous sclerosis complex harboring a subependymal giant cell astrocytoma (SEGA).

RESULTS

In each case, high-intensity FUS was used to target the intracranial lesion. Real-time MRI was used to monitor the thermoablations. Primary outcomes of interest were tolerability, feasibility, and safety of FUS. The radiographic ablation volume on intra- and postoperative MRI was also assessed. All 5 patients tolerated the procedure without any complications. Successful thermoablation was achieved in 4 of the 5 cases; the calcified SEGA was undertreated due to intratumor calcification, which prevented attainment of the target ablation temperature. The HHs underwent target tissue thermoablations that led to MR signal changes at the treatment site. For the patients harboring HHs, FUS thermoablations occurred without procedure-related complications and led to improvement in seizure control or hypothalamic hyperphagia. All 5 patients were discharged home on postoperative day 1 or 2, without any readmissions. There were no cases of hemorrhage, electrolyte derangement, endocrinopathy, or new neurological deficit in this cohort.

CONCLUSIONS

This experience demonstrates that FUS thermoablation of centrally located brain lesions in adolescents and young adults can be performed safely and that it provides therapeutic benefit for associated symptoms.

Neural Interactions Underlying Visuomotor Associations in the Human Brain

Rapid and flexible learning during behavioral choices is critical to our daily endeavors and constitutes a hallmark of dynamic reasoning. An important paradigm to examine flexible behavior involves learning new arbitrary associations mapping visual inputs to motor outputs. We conjectured that visuomotor rules are instantiated by translating visual signals into actions through dynamic interactions between visual, frontal and motor cortex. We evaluated the neural representation of such visuomotor rules by performing intracranial field potential recordings in epilepsy subjects during a rule-learning delayed match-to-behavior task. Learning new visuomotor mappings led to the emergence of specific responses associating visual signals with motor outputs in 3 anatomical clusters in frontal, anteroventral temporal and posterior parietal cortex. After learning, mapping selective signals during the delay period showed interactions with visual and motor signals. These observations provide initial steps towards elucidating the dynamic circuits underlying flexible behavior and how communication between subregions of frontal, temporal, and parietal cortex leads to rapid learning of task-relevant choices.

Post mortem examination of Parkinson's disease brains suggests decline in mitochondrial biomass, reversed by deep brain stimulation of subthalamic nucleus

Deep brain stimulation (DBS) of the subthalamic nucleus (STN) is the most commonly used surgical treatment for Parkinson's disease (PD). The disease-modifying aspects of DBS at a cellular level are not fully understood, and the key question of the effect of DBS on the degeneration of the dopaminergic (DA) neurons in the substantia nigra pars compacta (SNpc) remains to be answered. A major technical hurdle in determining any neuroprotective effect by DBS is its use in mid- to late-stage patients with PD when a majority of the DA neurons have been lost. In this work, we hypothesized that the long-term clinical benefits of DBS are, at least in part, due to a neuromodulatory effect on the SNpc neurons. These changes would affect cellular energetics and mitochondrial metabolism. We examined the number and volume of mitochondria as well as their vicinity to the DA presynaptic terminals postmortem caudate and putamen of 3 healthy individuals, 4 PD cases, and 3 DBS-treated patients. PD seems to have caused an increase in the mean distance between mitochondria and presynaptic terminals as well as a decrease in mean mitochondrial volume and numbers in DA projections. Although there was no difference in distance between mitochondria and presynaptic terminals of SNpc neurons in PD brains vs. DBS-treated brains, DBS treatment seemed to have inhibited or reversed the reduction in mitochondrial volume and numbers caused by PD. These results suggest enhanced metabolic plasticity leading to neuroprotection in the SNpc as a result of STN-DBS.-Mallach, A., Weinert, M., Arthur, J., Gveric, D., Tierney, T. S., Alavian, K. N. Post mortem examination of Parkinson's disease brains suggests decline in mitochondrial biomass, reversed by deep brain stimulation of subthalamic nucleus.

Neurological adverse event profile of magnetic resonance imaging-guided focused ultrasound thalamotomy for essential tremor

BACKGROUND

Magnetic resonance imaging-guided focused ultrasound thalamotomy is approved by the U.S. Food and Drug Administration for treatment of essential tremor. Although this incisionless technology creates an ablative lesion, it potentially avoids serious complications of open stereotactic surgery.

OBJECTIVE

To determine the safety profile of magnetic resonance imaging-guided focused ultrasound unilateral thalamotomy for essential tremor, including frequency, and severity of adverse events, including serious adverse events.

METHODS

Analysis of safety data for magnetic resonance imaging-guided focused ultrasound thalamotomy (186 patients, five studies).

RESULTS

Procedure-related serious adverse events were very infrequent (1.6%), without intracerebral hemorrhages or infections. Adverse events were usually transient and were commonly rated as mild (79%) and rarely severe (1%). As previously reported, abnormalities in sensation and balance were the commonest thalamotomy-related adverse events.

CONCLUSION

The overall safety profile of magnetic resonance imaging-guided focused ultrasound thalamotomy supports its role as a new option for patients with medically refractory essential tremor. © 2018 International Parkinson and Movement Disorder Society.

Deep brain stimulation: foundations and future trends

Deep brain stimulation (DBS) has emerged as a revolutionary treatment option for essential tremor (ET), Parkinson's disease (PD), idiopathic dystonia, and severe obsessive-compulsive disorder (OCD). This article reviews the historical foundations of DBS including basal ganglia pathophysiological models, classic principles of electrical stimulation, technical components of the DBS system, treatment risks, and future directions for DBS. Chronic high frequency stimulation induces a number of functional changes from fast physiological to slower metabolic effects and ultimately leads to structural reorganization of the brain, so-called neuroplasticity. Examples of each of these fast, slow, and long-term changes are given in the context of Parkinson's disease where these mechanisms have perhaps been the most intensely investigated. In particular, details of striatal dopamine release, expression of trophic factors, and a possible neuroprotective mechanism of DBS are highlighted. We close with a brief discussion of technical and clinical considerations for improvement. Deep brain stimulation will continue to offer a reversible and safe therapeutic option for a host of neurological conditions and remains one of the best windows into human brain physiology.

The incidence and healthcare costs of persistent postoperative pain following lumbar spine surgery in the UK: a cohort study using the Clinical Practice Research Datalink (CPRD) and Hospital Episode Statistics (HES)

OBJECTIVE

To characterise incidence and healthcare costs associated with persistent postoperative pain (PPP) following lumbar surgery.

DESIGN

Retrospective, population-based cohort study.

SETTING

Clinical Practice Research Datalink (CPRD) and Hospital Episode Statistics (HES) databases.

PARTICIPANTS

Population-based cohort of 10 216 adults who underwent lumbar surgery in England from 1997/1998 through 2011/2012 and had at least 1 year of presurgery data and 2 years of postoperative follow-up data in the linked CPRD-HES.

PRIMARY AND SECONDARY OUTCOMES MEASURES

Incidence and total healthcare costs over 2, 5 and 10 years attributable to persistent PPP following initial lumbar surgery.

RESULTS

The rate of individuals undergoing lumbar surgery in the CPRD-HES linked data doubled over the 15-year study period, fiscal years 1997/1998 to 2011/2012, from 2.5 to 4.9 per 10 000 adults. Over the most recent 5-year period (2007/2008 to 2011/2012), on average 20.8% (95% CI 19.7% to 21.9%) of lumbar surgery patients met criteria for PPP. Rates of healthcare usage were significantly higher for patients with PPP across all types of care. Over 2 years following initial spine surgery, the mean cost difference between patients with and without PPP was £5383 (95% CI £4872 to £5916). Over 5 and 10 years following initial spine surgery, the mean cost difference between patients with and without PPP increased to £10 195 (95% CI £8726 to £11 669) and £14 318 (95% CI £8386 to £19 771), respectively. Extrapolated to the UK population, we estimate that nearly 5000 adults experience PPP after spine surgery annually, with each new cohort costing the UK National Health Service in excess of £70 million over the first 10 years alone.

CONCLUSIONS

Persistent pain affects more than one-in-five lumbar surgery patients and accounts for substantial long-term healthcare costs. There is a need for formal, evidence-based guidelines for a coherent, coordinated management strategy for patients with continuing pain after lumbar surgery.

Relationship between initial therapy and blood pressure control for high-risk hypertension patients in the UK: a retrospective cohort study from the THIN general practice database

OBJECTIVE

To examine the UK practice patterns in treating newly diagnosed hypertension and to determine whether subgroups of high-risk patients are more or less likely to follow particular therapeutic protocols and to reach blood pressure goals.

DESIGN

Retrospective cohort study.

SETTING

This study examined adults in The Health Improvement Network (THIN) UK general practice medical records database who were initiated on medication for hypertension.

PARTICIPANTS

48 131 patients with essential hypertension diagnosed between 2008 and 2010 who were registered with a participating practice for a minimum of 13 months prior to, and 6 months following, initiation of therapy. We excluded patients with gestational hypertension or secondary hypertension. Patients were classified into risk groups based on blood pressure readings and comorbid conditions.

PRIMARY AND SECONDARY OUTCOME MEASURES

Odds of receiving single versus fixed or free-drug combination therapy and odds of achieving blood pressure control were assessed using multivariable logistic regression.

RESULTS

The vast majority of patients (95.8%) were initiated on single drug therapy. Patients with high cardiovascular risk (patients with grade 2-3 hypertension or those with high normal/grade 1 hypertension plus at least one cardiovascular condition pretreatment) had a statistically significant benefit of starting immediately on combination therapy when blood pressure control was the desired goal (OR: 1.23; 95% CI: 1.06 to 1.42) but, surprisingly, were less likely than patients with no risk factors to receive combination therapy (OR: 0.53; 95% CI: 0.47 to 0.59).

CONCLUSIONS

Our results suggest that combination therapy may be indicated for patients with high cardiovascular risk, who accounted for 60.6% of our study population. The National Institute for Health and Care Excellence guideline CG34 of 2006 (in effect during the study period) recommended starting with single drug class therapy for most patients, and this advice does seem to have been followed even in cases where a more aggressive approach might have been considered.

A Randomized Trial of Focused Ultrasound Thalamotomy for Essential Tremor

BACKGROUND

Uncontrolled pilot studies have suggested the efficacy of focused ultrasound thalamotomy with magnetic resonance imaging (MRI) guidance for the treatment of essential tremor.

METHODS

We enrolled patients with moderate-to-severe essential tremor that had not responded to at least two trials of medical therapy and randomly assigned them in a 3:1 ratio to undergo unilateral focused ultrasound thalamotomy or a sham procedure. The Clinical Rating Scale for Tremor and the Quality of Life in Essential Tremor Questionnaire were administered at baseline and at 1, 3, 6, and 12 months. Tremor assessments were videotaped and rated by an independent group of neurologists who were unaware of the treatment assignments. The primary outcome was the between-group difference in the change from baseline to 3 months in hand tremor, rated on a 32-point scale (with higher scores indicating more severe tremor). After 3 months, patients in the sham-procedure group could cross over to active treatment (the open-label extension cohort).

RESULTS

Seventy-six patients were included in the analysis. Hand-tremor scores improved more after focused ultrasound thalamotomy (from 18.1 points at baseline to 9.6 at 3 months) than after the sham procedure (from 16.0 to 15.8 points); the between-group difference in the mean change was 8.3 points (95% confidence interval [CI], 5.9 to 10.7; P<0.001). The improvement in the thalamotomy group was maintained at 12 months (change from baseline, 7.2 points; 95% CI, 6.1 to 8.3). Secondary outcome measures assessing disability and quality of life also improved with active treatment (the blinded thalamotomy cohort)as compared with the sham procedure (P<0.001 for both comparisons). Adverse events in the thalamotomy group included gait disturbance in 36% of patients and paresthesias or numbness in 38%; these adverse events persisted at 12 months in 9% and 14% of patients, respectively.

CONCLUSIONS

MRI-guided focused ultrasound thalamotomy reduced hand tremor in patients with essential tremor. Side effects included sensory and gait disturbances. (Funded by InSightec and others; ClinicalTrials.gov number, NCT01827904.).

Optimizing microdialysis for deep brain stimulation

Cerebral microdialysis is a chemical detection method capable of identifying and simultaneously sampling a wide range of substances in the micromilieu of the monitoring probe. The interstitial space of biological tissues and fluids is sampled through a thin fenestrated dialysis catheter inserted into the brain. The technique has been reported in patients with Parkinson's disease. However, the procedure is not widely used by neurosurgeons, possibly owing to unclear indications and poor effective benefits, mostly secondary to significant pitfalls. In spite of the feasibility of microdialysis in humans, many factors can affect the quality of the process. Possible pitfalls include improperly designed probe, probe insertion effects, ineffective perfusion rate, issues to optimize stabilization period, and insufficient volume sample. This article reviews those key technical features necessary for performing microdialysis in humans during deep brain stimulation for Parkinson's Disease.

Evolution of Movement Disorders Surgery Leading to Contemporary Focused Ultrasound Therapy for Tremor

Progressively less invasive neurosurgical approaches for the treatment of movement disorders have evolved, beginning with open craniotomy for placement of lesions within pyramidal structures followed by refined stereotactic ablation of extrapyramidal targets that encouraged nondestructive electrode stimulation of deep brain structures. A noninvasive approach using transcranial high-energy focused ultrasound has emerged for the treatment of intractable tremor. The ability to target discreet intracranial sites millimeters in size through the intact skull using focused acoustic energy marks an important milestone in movement disorders surgery. This article describes the evolution of magnetic resonance-guided focused ultrasound for ventrolateral thalamotomy for tremor.

Rapid Modulation of Protein Expression in the Rat Hippocampus Following Deep Brain Stimulation of the Fornix

BACKGROUND

The forniceal area is currently being evaluated as a target for deep brain stimulation (DBS) to improve cognitive function in patients with Alzheimer's disease. The molecular changes at downstream targets within the stimulated circuit are unknown.

OBJECTIVE

To analyze the modulation of hippocampal protein expression following 1 h of fornix DBS in the rat.

METHODS

Animals underwent bilateral forniceal DBS for 1 h and sacrificed at different time-points after the initiation of the stimulation (1 h, 2.5 h, 5 h, 25 h). Bilateral hippocampi were isolated for western blot analyses.

RESULTS

Forniceal DBS led to a dramatic elevation of cFos post-stimulation, suggesting that forniceal DBS activates the hippocampus. There was also a significant increase in candidate proteins including several trophic factors, such as brain derived neurotrophic factor (BDNF) and vascular endothelial growth factor (VEGF) but not glial cell-derived neurotrophic factor (GDNF). There was in addition, increased expression of the synaptic markers growth associated protein 43 (GAP-43), synaptophysin and α-synuclein. No changes were observed at the studied time-points in Alzheimer's-related proteins including amyloid precursor protein (APP), tau, phosphorylated tau (ptau), or selected chaperone proteins (HSP40, HSP70 and CHIP).

CONCLUSIONS

Forniceal DBS triggers hippocampal activity and rapidly modulate the expression of neurotrophic factors and markers of synaptic plasticity known to play key roles in memory processing. The clinical effects of DBS of the fornix may, in part, be mediated by producing changes in the expression of these proteins.

Isolation, culture and long-term maintenance of primary mesencephalic dopaminergic neurons from embryonic rodent brains

Degeneration of mesencephalic dopaminergic (mesDA) neurons is the pathological hallmark of Parkinson's diseae. Study of the biological processes involved in physiological functions and vulnerability and death of these neurons is imparative to understanding the underlying causes and unraveling the cure for this common neurodegenerative disorder. Primary cultures of mesDA neurons provide a tool for investigation of the molecular, biochemical and electrophysiological properties, in order to understand the development, long-term survival and degeneration of these neurons during the course of disease. Here we present a detailed method for the isolation, culturing and maintenance of midbrain dopaminergic neurons from E12.5 mouse (or E14.5 rat) embryos. Optimized cell culture conditions in this protocol result in presence of axonal and dendritic projections, synaptic connections and other neuronal morphological properties, which make the cultures suitable for study of the physiological, cell biological and molecular characteristics of this neuronal population.

Decrease in gamma-band activity tracks sequence learning

Learning novel sequences constitutes an example of declarative memory formation, involving conscious recall of temporal events. Performance in sequence learning tasks improves with repetition and involves forming temporal associations over scales of seconds to minutes. To further understand the neural circuits underlying declarative sequence learning over trials, we tracked changes in intracranial field potentials (IFPs) recorded from 1142 electrodes implanted throughout temporal and frontal cortical areas in 14 human subjects, while they learned the temporal-order of multiple sequences of images over trials through repeated recall. We observed an increase in power in the gamma frequency band (30–100 Hz) in the recall phase, particularly in areas within the temporal lobe including the parahippocampal gyrus. The degree of this gamma power enhancement decreased over trials with improved sequence recall. Modulation of gamma power was directly correlated with the improvement in recall performance. When presenting new sequences, gamma power was reset to high values and decreased again after learning. These observations suggest that signals in the gamma frequency band may play a more prominent role during the early steps of the learning process rather than during the maintenance of memory traces.

Deep brain stimulation and ablation for obsessive compulsive disorder: evolution of contemporary indications, targets and techniques

Surgical therapy for treatment-resistant obsessive compulsive disorder (OCD) remains an effective option for well-selected patients managed within a multidisciplinary setting. Historically, lesions within the limbic system have been used to control both obsessive thoughts and repetitive compulsions associated with this disease. We discuss classical targets as well as contemporary neuromodulatory approaches that have been shown to provide symptomatic relief. Recently, deep brain stimulation (DBS) of the anterior limb of the internal capsule/ventral striatum received Conformité Européene (CE) mark and Food and Drug Administration (FDA) approvals for treatment of intractable OCD. Remarkably, this is the first such approval for neurosurgical intervention in a strictly psychiatric indication in modern times. This target is discussed in detail along with alternative targets currently being proposed. We close with a discussion of gamma knife capsulotomy, a modality with deep historical roots. Further directions in the surgical treatment of OCD will require better preoperative predictors of postoperative responses, optimal selection of individualized targets, and rigorous reporting of adverse events and standardized outcomes. To meet these challenges, centers must be equipped with a multidisciplinary team and patient-centered approach to ensure adequate screening and follow up of patients with this difficult-to-treat condition.

Neuromodulation for neurodegenerative conditions

Pharmacological therapy has had limited success in the treatment of most major neurological diseases. This has motivated the development of a number of novel surgical approaches designed to ameliorate drug-induced side effects or pharmacoresistant symptoms. Deep brain stimulation (DBS) has been quite successful in controlling both the cardinal motor manifestation of Parkinson's disease and the side effects of prolonged levodopa therapy. This has encouraged the application of DBS technology to treat a number of other neurodegenerative conditions, including secondary dystonia associated with pantothenate kinase-associated neurodegeneration (PKAN, formerly Hallervorden-Spatz syndrome), chorea associated with Huntington's disease, and most recently, cognitive decline associated with Alzheimer's type dementia. We review the rationale, indications and outcomes of neuromodulation for selected neurodegenerative conditions. In addition to DBS, we discuss select small molecule and gene-based neuromodulatory approaches. Ongoing study of basic pathophysiological mechanisms may eventually allow directed primary prevention of some of these diseases, but until then, invasive neuromoduation will likely continue to play an ever-increasing role in the delivery of the most advanced care for patients with these debilitating conditions.

Surgical treatment for secondary dystonia

Surgical therapy for the secondary dystonias is generally perceived to be less effective than for primary disease. However, a number of case reports and small open series have recently appeared describing quite favorable outcomes following surgery for some nonprimary dystonias. We discuss surgical treatment options for this group of diverse conditions, including tardive dystonia, dystonic cerebral palsy, and certain heredodegenerative diseases in which deep brain stimulation and ablative lesions of the posteroventral pallidum have been shown to be effective. Other types of secondary dystonia respond less well to pallidal surgery, particularly when anatomical lesions of the basal ganglia are prominent on preoperative imaging. For these conditions, central baclofen delivery and botulinum toxin denervation may be considered. With optimal medical and surgical care, some patients with secondary dystonia have achieved reductions in disability and pain that approach those documented for primary dystonia.

Novel applications of deep brain stimulation

The success of deep brain stimulation (DBS) surgery in treating medically refractory symptoms of some movement disorders has inspired further investigation into a wide variety of other treatment-resistant conditions. These range from disorders of gait, mood, and memory to problems as diverse as obesity, consciousness, and addiction. We review the emerging indications, rationale, and outcomes for some of the most promising new applications of DBS in the treatment of postural instability associated with Parkinson's disease, depression, obsessive–compulsive disorder, obesity, substance abuse, epilepsy, Alzheimer′s-type dementia, and traumatic brain injury. These studies reveal some of the excitement in a field at the edge of a rapidly expanding frontier. Much work still remains to be done on basic mechanism of DBS, optimal target and patient selection, and long-term durability of this technology in treating new indications.

Deep brain stimulation emerging indications

There are a number of emerging surgical indications for deep brain stimulation. We have shown that modulation of activity within motor, mood, and cognitive circuits has beneficial effects in patients with Parkinson's disease, treatment-resistant depression, and perhaps Alzheimer's type dementia. We review the rationale, safety, and efficacy for each of these indications, focusing on disease mechanisms and relevant data that are necessary to document therapeutic value in each case. The review closes with some thoughts on possible future directions for deep brain stimulation. It is likely that applications for deep brain stimulation will continue to expand as accumulating data establish its safety and efficacy profile in these and other conditions.

Recombinant adeno-associated virus type 2 pseudotypes: comparing safety, specificity, and transduction efficiency in the primate striatum. Laboratory investigation

OBJECT

Although several clinical trials utilizing the adeno-associated virus (AAV) type 2 serotype 2 (2/2) are now underway, it is unclear whether this particular serotype offers any advantage over others in terms of safety or efficiency when delivered directly to the CNS.

METHODS

Recombinant AAV2-green fluorescent protein (GFP) serotypes 2/1, 2/2, 2/5, and 2/8 were generated following standard triple transfection protocols (final yield 5.4 × 10(12) particles/ml). A total of 180 μl of each solution was stereotactically infused, covering the entire rostrocaudal extent of the caudoputamen in 4 rhesus monkeys (Macaca mulatta) (3.0 ± 0.5 kg). After 6 weeks' survival, the brain was formalin fixed, cut at 40 μm, and stained with standard immunohistochemistry for anti-GFP, anticaspase-2, and cell-specific markers (anti-microtubule-associated protein-2 for neurons and anti-glial fibrillary acidic protein for glia). Unbiased stereological counting methods were used to determine cell number and striatal volume.

RESULTS

The entire striatum of each animal contained GFP-positive cells with significant labeling extending beyond the borders of the basal ganglia. No ischemic/necrotic, hemorrhagic, or neoplastic change was observed in any brain. Total infusate volumes were similar across the 4 serotypes. However, GFP-labeled cell density was markedly different. Adeno-associated virus 2/1, 2/2, and 2/5 each labeled < 8000 cells/mm(3), whereas serotype 8 labeled > 21,000 cells, a 3- to 4-fold higher transduction efficiency. On the other hand, serotype 8 also labeled neurons and glia with equal affinity compared with neuronal specificities > 89% for the other serotypes. Moderate caspase-2 colabeling was noted in neurons immediately around the AAV2/1 injection tracts, but was not seen above the background anywhere in the brain following injections with serotypes 2, 5, or 8.

CONCLUSIONS

Intrastriatal delivery of AAV2 yields the highest cell transduction efficiencies but lowest neuronal specificity for serotype 8 when compared with serotypes 1, 2, and 5. Only AAV2/1 revealed significant caspase-2 activation. Careful consideration of serotype-specific differences in AAV2 neurotropism, transduction efficiency, and potential toxicity may affect future human trials.

Infantile myofibromatosis: a nontraumatic cause of neonatal brachial plexus palsy

Most injuries to the neonatal brachial plexus occur acutely at birth, and are iatrogenic in origin. However, when weakness is accompanied by atrophy, nontraumatic etiologies should be considered. The differential diagnosis of chronic congenital brachial plexopathy includes cervical bone malformations, humeral osteomyelitis, varicella, and compression from various types of infantile tumors. An illustrative male infant delivered at 37 weeks of gestation with wasted musculature of the left upper arm, ipsilateral Horner's syndrome, and a hemidiaphragm is presented. On further examination, this patient manifested an underlying cervical tumor compressing the brachial plexus. Diagnostic steps leading to the pathologic identification of a solitary cervical myofibroma included physical examination, electromyography, radiographic imaging, and open biopsy. This report emphasizes the importance of differentiating acute from chronic congenital plexus palsy and of recognizing the possibility that infection or neoplasm may underlie the latter.

Intracranial delivery of the nitric oxide donor diethylenetriamine/nitric oxide from a controlled-release polymer: toxicity in cynomolgus monkeys

OBJECTIVE

Diethylenetriamine/nitric oxide (DETA/NO) has been shown to be an effective treatment for delayed posthemorrhagic vasospasm when released abluminally from ethylene-vinyl acetate copolymer (EVAc). However, the observed mortality associated with this drug warrants further investigation. To establish a maximum tolerable dose, this study evaluated the toxicity of DETA/NO released from EVAc in a dose-escalation series in cynomolgus monkeys (Macaca fascicularis).

METHODS

DETA/NO was incorporated into EVAc at a 20:80 dry weight ratio (DETA/NO:EVAc). A total of 13 animals underwent a right frontotemporal craniotomy for placement of a single polymer delivering no drug (n = 3), 0.5 +/- 0.1 mg/kg (n = 3), 0.9 +/- 0.1 mg/kg (n = 3), 1.9 +/- 0.2 mg/kg (n = 3), or a 3.2 mg/kg dose (n = 1) into the subarachnoid space.

RESULTS

The animal receiving the highest dose of DETA/NO (3.2 mg/kg) died 46 hours after surgery. The remaining animals survived for the planned duration of the study. One animal in the group receiving the 1.9 mg/kg dose experienced a seizure 25 hours after surgery and remained lethargic for 2 days before making a complete recovery. The remaining animals exhibited no adverse behavioral effects. Histopathological examination of brain tissue revealed hemorrhagic and ischemic changes at doses above 0.9 mg/kg. No evidence of vascular wall pathology or infection was observed in any animal.

CONCLUSION

The greatest amount of DETA/NO safely delivered from EVAc copolymer to the subarachnoid space of the cynomolgus monkey is approximately 1.0 mg/kg. These findings show that continuous intracisternal delivery of DETA/NO is a safe and potentially effective strategy for prophylactic treatment of delayed cerebral vasospasm.

Prevention of experimental cerebral vasospasm by intracranial delivery of a nitric oxide donor from a controlled-release polymer: toxicity and efficacy studies in rabbits and rats

BACKGROUND AND PURPOSE

A reduction in the local availability of nitric oxide (NO) may play a role in the etiology of chronic cerebral vasospasm after subarachnoid hemorrhage (SAH). We investigated the toxicity and efficacy of a locally delivered NO donor from a controlled-release polymer in preventing experimental cerebral vasospasm in rats and rabbits, respectively.

METHODS

Diethylenetriamine/NO (DETA/NO) was incorporated into controlled release ethylene-vinyl acetate (EVAc) polymers. Twenty-eight rats were used in a dose-escalation toxicity study to establish a maximally tolerated dose of DETA/NO-EVAc polymer. In the efficacy experiment, 20 rabbits were assigned to 4 experimental groups (n=5 per group): sham operation; SAH only; SAH+empty EVAc polymer; and SAH+DETA/NO-EVAc polymer. Treatment was initiated 30 minutes after blood deposition. Basilar artery lumen patency was assessed 72 hours after hemorrhage to evaluate the efficacy of DETA/NO in preventing cerebral vasospasm.

RESULTS

In the toxicity study, a dose of 3.4 mg/kg was identified as the LD(20) (dose with 20% mortality during the study period) of this DETA/NO formulation. Brain histology revealed hemorrhage and ischemic changes at the implantation site associated with high concentrations of DETA/NO. In the efficacy study, treatment with DETA/NO-EVAc polymer resulted in a significant decrease in basilar artery vasospasm compared with no treatment (93.0+/-4.9% versus 71.4+/-11.9%; P=0.035) or compared with treatment with blank EVAc polymer (93.0+/-4.9% versus 73.2+/-6.4%; P=0.003).

CONCLUSIONS

Local delivery of DETA/NO prevents vasospasm in the rabbit basilar artery. Local delivery of DETA/NO via polymers is a safe and effective strategy for preventing cerebral vasospasm after SAH in this model.

Prevention and reversal of experimental posthemorrhagic vasospasm by the periadventitial administration of nitric oxide from a controlled-release polymer

OBJECTIVE

Despite improvements in the care of patients with aneurysmal subarachnoid hemorrhage, delayed cerebral vasospasm remains a major cause of morbidity and death. There is now evidence that a decrease in the local availability of nitric oxide (NO) plays a role in delayed cerebral vasospasm. We evaluated a controlled-release polymer containing the NO donor (Z)-1-[2-(2-aminoethyl)-N-(2-ammonioethyl)amino]diazen-1-ium-1,2-diolate (DETA/NO) for the treatment of chronic posthemorrhagic vasospasm in the rat femoral artery model.

METHODS

The release kinetics of ethylene/vinyl acetate copolymers loaded with 20% (w/w) DETA/NO were determined in vitro. Chronic vasospasm was induced in the left femoral artery of adult male Fischer 344 rats (n = 35) by exposure to autologous blood. At 1, 3, or 7 days after blood exposure, either a 5-mg polymer loaded with 20% (w/w) DETA/NO or an empty 5-mg polymer was placed in the periadventitial space next to the left femoral artery. At the same time, an empty 5-mg polymer was placed next to the right femoral artery. On the 8th day after blood exposure (at the peak of vasospasm in this model), rats were transcardially perfused with 4% paraformaldehyde, and the left and right femoral arteries were removed for histological processing and morphometric analyses. Vasospasm was expressed as the percent lumen patency of the treated left artery, compared with the control right artery.

RESULTS

The in vitro release kinetics demonstrated that the 20% DETA/NO-loaded polymers released up to 15% of their total drug load during a 9-day period. DETA/NO treatments initiated at 1, 3, or 7 days after blood deposition all significantly inhibited vasospasm, compared with control values (94.6 +/- 7.2% versus 67.6 +/- 5.8%, 104.6 +/- 5.5% versus 64.9 +/- 1.7%, and 102.4 +/- 5.1% versus 73.6 +/- 1.4%, respectively; mean +/- standard error of the mean percent lumen patency; P < 0.001). No adverse effects of treatment were observed.

CONCLUSION

The diazeniumdiolate NO donor DETA/NO can be effectively released from ethylene/vinyl acetate polymers. Administration of DETA/NO into the periadventitial space can prevent the development of chronic posthemorrhagic vasospasm in the rat femoral artery and can reverse established vasospasm. No adverse effects of DETA/NO were observed in this model.

Development of brain-derived neurotrophic factor and neurotrophin-3 immunoreactivity in the lower auditory brainstem of the postnatal gerbil

The localization of brain-derived neurotrophic factor (BDNF) and neurotrophin-3 (NT-3) in the gerbil auditory brainstem was studied during normal postnatal development. The principal objective of this paper was to compare the developmental distribution of BDNF and NT-3 proteins to the known developmental distribution of their cognate, high-affinity tyrosine kinase receptors. BDNF and NT-3 proteins were localized using standard immunohistochemistry. No specific immunoreactivity for BDNF or NT-3 was detected on the day of birth (P0) in any auditory structure, although fibers comprising the spinal tract of the Vth cranial nerve were well labelled with antibodies against BDNF. Diffuse immunoreactivity for both BDNF and NT-3 was first detected at P3 in the cochlear nucleus and in several second order auditory nuclei in the superior olivary complex. This diffuse immunoreactivity became clustered and restricted to neuronal cell bodies by P10. Immunoreactivity for both BDNF and NT-3 transiently disappeared in the lateral and medial superior olivary nuclei at P10. However, neurons in the medial nucleus of the trapezoid body remained immunopositive for both BDNF and NT-3. Fibers in the trapezoid body were labelled with BDNF immunoreactivity by P12. Between P12 and P15, the distribution of BDNF and NT-3 immunoreactivity in the cochlear nucleus and superior olivary complex became comparable to adult (P140) immunolabel. These results show that the normal developmental distribution of the neurotrophins BDNF and NT-3 in the lower auditory brainstem occurs during the first two postnatal weeks in parallel with the developmental expression of their cognate receptors, trkB and trkC.

Naturally occurring neuron death during postnatal development of the gerbil ventral cochlear nucleus begins at the onset of hearing

Postnatal development of the gerbil ventral cochlear nucleus (VCN) was studied quantitatively under the light microscope in Nissl-stained serial sections at postnatal day 0 (P0), P5, P7, P10, P12, P15, and P140. VCN boundaries were unambiguous at all ages, and nucleus volume was calculated planimetrically for all groups. Measurements of neuron soma cross-sectional area and number were made in all groups except P0. Both VCN volume and soma area doubled between P5 and P10. Although somatic growth did not continue beyond P10, VCN volume increased a further 57% between P15 and P140. Neuron number did not change significantly between P5 and P10, averaging approximately 36,000 neurons. Between P10 and P12, neuron number decreased significantly by 22%, with no further change thereafter. Our data show that, following significant postnatal growth in the gerbil VCN, a brief period of naturally occurring neuron death begins at the onset of hearing.

Susceptibility of developing cochlear nucleus neurons to deafferentation-induced death abruptly ends just before the onset of hearing

To investigate the ability of developing cochlear nucleus (CN) neurons to survive in the absence of afferent input, left cochlear removals were performed on gerbils at 2 day intervals from postnatal (P)3 to P11, and at P18 and P93. After a 3 month postsurgical survival period, Nissl-stained frontal sections through the brainstem were analyzed under the light microscope. CN volume, anteroventral cochlear nucleus (AVCN) neuron cross-sectional area, and total number of neurons in the CN were measured on both sides of the brain. Mean volume reduction of the deafferented CN relative to the intact CN ranged between 76% in the P3 group to 33% in the P11 group and did not differ significantly between P11 and P93. Cochlear removal at all ages reduced AVCN neuron cross-sectional area by approximately 40% in the deafferented CN relative to the intact CN, except for the P93 group where neuron atrophy was significantly less severe (23% mean reduction). Massive loss of CN neurons (>50% of the intact side) was observed following cochlear removal performed during the first postnatal week. However, between P7 and P9, neurons in all areas of the CN lose susceptibility to deafferentation-induced neuron death. No significant neuron loss was observed following cochlear removal after P7. This study shows that an abrupt transition in the ability of CN neurons to survive in the absence of afferent input is coincident with events leading to the onset of hearing.

Binaural interaction in human neonatal auditory brainstem

Binaural interaction (BI) in brainstem auditory evoked response (BAER) were examined in normal term neonates. The BI components coincided consistently with the latency range of BAER wave IV through wave VII. Most BI components seen in the adults could be identified in the neonates, but the later components, i.e. those with longer latency, were underdeveloped in wave form. Wave DV was the most consistent and reproducible BI component. A marked difference between the neonatal and adult BI wave forms was that wave DVII was particularly small in the neonates. It appears that neuronal responses contributing to later BI components such as wave DVII are particularly immature at birth. Wave latencies and interpeak intervals were longer and amplitudes were smaller in the neonates than in the adults, which was associated with the differences between the neonates and adults in the BAER components. Changes in the BI components with stimulus intensity and rate in the neonates were fundamentally similar to but more significant compared with those in the adults. These findings suggest that neural connections in human auditory brainstem subserving the BI are established at birth but, particularly at higher levels of the brainstem, are immature.

Long-term effect of perinatal and postnatal asphyxia on developing human auditory brainstem responses: brainstem impairment

Long-term effect of perinatal and postnatal asphyxia on the developing auditory brainstem was investigated in children, particularly those who exhibited residual neurodevelopmental deficits, by analyzing the central components of brainstem auditory evoked responses (BAER). The major abnormalities in the BAER were a reduction of wave V amplitude, followed by a decrease in V/I amplitude ratio, while abnormalities in interpeak intervals were relatively rare. These findings suggest that asphyxia could result in residual neural dysfunction of the brainstem but does not appear to exert any major long-term effect on neuronal transmission. BAER abnormalities occurred more frequently in the children with residual neurodevelopmental deficits than those without these deficits after perinatal asphyxia. The occurrence of BAER abnormalities was related to the duration as well as the degree of asphyxia. No significant difference was found in the abnormalities of the central BAER components between the children after perinatal asphyxia and those after postnatal asphyxia, suggesting that perinatal and postnatal asphyxia exerts a similar long-term effect on the developing central nervous system.

Development of human peripheral hearing revealed by brainstem auditory evoked potentials

Development of human peripheral hearing from birth to 6 years was investigated by recording brainstem auditory evoked potentials (BAEPs). The threshold of BAEPs decreased rapidly during the first 3 months after birth (2.7 dB/week during the neonatal period, 2.6 dB/month at 1-3 months), after which further decrease occurred more slowly but continued through 1 year of age (0.26 dB/month at 3-12 months). A few days after birth, the threshold was 18 dB higher compared to the adults, and progressively decreased to 10, 5 and 2 dB at 1, 3 and 12 months, respectively. The latencies of waves I and V decreased as a function of age at a rate of 0.01 and 0.05 ms/week during the neonatal period, 0.02 and 0.10 ms/month at 1-3 months and 0.014 and 0.076 ms/month at 3-12 months, respectively. Adult latency value was attained by 2 and 4 years for waves I and V, respectively. These findings suggest that although the ear is reported to be almost adult-like at birth, the immaturity in neural functional properties limits auditory sensitivity during early childhood. It appears that human peripheral hearing threshold decreases rapidly through the third postnatal month and thereafter continues to improve slowly through early childhood. It is postulated that the first 3 months after birth are likely to be a critical period in postnatal development of human peripheral hearing.