Demographics of focused ultrasound thalamotomy for essential tremor and trends in deep brain stimulation surgery after its introduction in the USA

Background

Essential tremor (ET) is a movement disorder that affects 4%-5% of adults >65 years. For patients with medically refractory ET, neurosurgical interventions such as deep brain stimulation (DBS) and unilateral MR-guided focused ultrasound thalamotomy (MRgFUS) are available. In this retrospective cohort study, we examined the demographics of patients with ET who have received MRgFUS and evaluated trends in DBS usage in the USA after the introduction of MRgFUS in 2016.

Methods

We used multiple databases to examine the demographics of patients who received DBS and MRgFUS, and trends in DBS. To assess the demographics, we queried the TriNetX database from 2003 to 2022 to identify patients diagnosed with ET and stratify them by DBS or MRgFUS treatment by using Current Procedural Terminology codes. Patient demographics were reported as frequencies and percentages. To examine the trends in DBS for ET, the yearly frequency of DBS procedures done for ET between 2012 and 2019 was extracted from the National Inpatient Sample (NIS) database, and breakpoint analysis was performed. Additionally, the yearly frequency of MRgFUS procedures for ET was obtained from Insightec Exlabate.

Results

Most of the patients (88.69%) in the cohort extracted from TriNetX database self-identified as white, followed by black or African American (2.40%) and Asian (0.52%). A higher percentage of black patients received MRgFUS treatment than DBS (4.10% vs 1.88%). According to the NIS database, from 2012 to 2020, 13 525 patients received DBS for ET.

Conclusion

This study provides an overview of the characteristics of patients who undergo DBS or MRgFUS. We found notable differences in sex and race among patients who underwent each treatment type. Additionally, until at least the beginning of 2020, the number of DBS procedures for ET was not negatively affected after the introduction of MRgFUS.

Intraoperative physiology augments atlas-based data in awake deep brain stimulation

BACKGROUND

Deep brain stimulation (DBS) is commonly performed with patients awake to perform intraoperative microelectrode recordings and/or macrostimulation testing to guide final electrode placement. Supplemental information from atlas-based databases derived from prior patient data and visualised as efficacy heat maps transformed and overlaid onto preoperative MRIs can be used to guide preoperative target planning and intraoperative final positioning. Our quantitative analysis of intraoperative testing and corresponding changes made to final electrode positioning aims to highlight the value of intraoperative neurophysiological testing paired with image-based data to optimise final electrode positioning in a large patient cohort.

METHODS

Data from 451 patients with movement disorders treated with 822 individual DBS leads at a single institution from 2011 to 2021 were included. Atlas-based data was used to guide surgical targeting. Intraoperative testing data and coordinate data were retrospectively obtained from a large patient database. Medical records were reviewed to obtain active contact usage and neurologist-defined outcomes at 1 year.

RESULTS

Microelectrode recording firing profiles differ per track, per target and inform the locations where macrostimulation testing is performed. Macrostimulation performance correlates with the final electrode track chosen. Centroids of atlas-based efficacy heat maps per target were close in proximity to and may predict active contact usage at 1 year. Overall, patient outcomes at 1 year were improved for patients with better macrostimulation response.

CONCLUSIONS

Atlas-based imaging data is beneficial for target planning and intraoperative guidance, and in conjunction with intraoperative neurophysiological testing during awake DBS can be used to individualize and optimise final electrode positioning, resulting in favourable outcomes.

Ipsilateral and axial tremor response to focused ultrasound thalamotomy for essential tremor: clinical outcomes and probabilistic mapping

BACKGROUND

MR-guided focused ultrasound (MRgFUS) thalamotomy has been shown to be a safe and effective treatment for essential tremor (ET).

OBJECTIVE

To investigate the effects of MRgFUS in patients with ET with an emphasis on ipsilateral-hand and axial tremor subscores.

METHODS

Tremor scores and adverse effects of 100 patients treated between 2012 and 2018 were assessed at 1 week, 3, 12, and 24 months. A subgroup analysis of ipsilateral-hand tremor responders (defined as patients with ≥30% improvement at any time point) and non-responders was performed. Correlations and predictive factors for improvement were analysed. Weighted probabilistic maps of improvement were generated.

RESULTS

Significant improvement in axial, contralateral-hand and total tremor scores was observed at all study visits from baseline (p<0.0001). There was no significant improvement in ipsilateral subscores. A subset of patients (n=20) exhibited group-level ipsilateral-hand improvement that remained significant through all follow-ups (p<0.001). Multivariate regression analysis revealed that higher baseline scores predict better improvement in ipsilateral-hand and axial tremor. Probabilistic maps demonstrated that the lesion hotspot for axial improvement was situated more medially than that for contralateral improvement.

CONCLUSION

MRgFUS significantly improved axial, contralateral-hand and total tremor scores. In a subset of patients, a consistent group-level treatment effect was observed for ipsilateral-hand tremor. While ipsilateral improvement seemed to be less directly related to lesion location, a spatial relationship between lesion location and axial and contralateral improvement was observed that proved consistent with the somatotopic organisation of the ventral intermediate nucleus.

TRIAL REGISTRATION NUMBERS

NCT01932463, NCT01827904, and NCT02252380.

Functional tremor developing after successful MRI-guided focused ultrasound thalamotomy for essential tremor

OBJECTIVE

To describe a case of functional tremor occurring after a successful MR-guided focused ultrasound thalamotomy (MRgFUS) for essential tremor.

METHODS

A 71-year-old right-handed man with essential tremor was referred to us for consideration of deep brain stimulation surgery for worsening bilateral upper limb tremor after a successful left MRgFUS for essential tremor.

RESULTS

On clinical exam, signs compatible with a functional tremor were noted, including entertainability and suppressibility. Electrophysiological studies were consistent with essential tremor and superimposed tremor fulfilling the laboratory-supported criteria for functional tremor.

DISCUSSION

We describe the first reported case of a functional movement disorder occurring after successful MRgFUS procedure for essential tremor. Recognising this entity and its development after such therapeutic interventions is essential to avoid further unnecessary invasive therapies.

Unusual tremor syndromes: know in order to recognise

Tremor is a common neurological condition in clinical practice; yet, few syndromes are widely recognised and discussed in the literature. As a result, there is an overdiagnosis of well-known causes, such as essential tremor. Many important unusual syndromes should be considered in the differential diagnosis of patients with tremor. The objective of this review is to provide broad clinical information to aid in the recognition and treatment of various unusual tremor syndromes in the adult and paediatric populations. The review comprised of a comprehensive online search using PubMed, Ovid database and Google Scholar to identify the available literature for each unusual tremor syndrome. The review includes fragile X-associated tremor/ataxia syndrome, spinocerebellar ataxia type 12, tremors caused by autosomal recessive cerebellar ataxias, myorhythmia, isolated tongue tremor, Wilson's disease, slow orthostatic tremor, peripheral trauma-induced tremor, tardive tremor and rabbit syndrome, paroxysmal tremors (hereditary chin tremor, bilateral high-frequency synchronous discharges, head tremor, limb-shaking transient ischaemic attack), bobble-head doll syndrome, spasmus nutans and shuddering attacks. Rare tremors generally present with an action tremor and a variable combination of postural and kinetic components with resting tremors less frequently seen. The phenomenology of myorhythmia is still vague and a clinical definition is proposed. The recognition of these entities should facilitate the correct diagnosis and guide the physician to a prompt intervention.

What do patients with scans without evidence of dopaminergic deficit (SWEDD) have? New evidence and continuing controversies

The term SWEDD (scans without evidence for dopaminergic deficit) refers to the absence, rather than the presence, of an imaging abnormality in patients clinically presumed to have Parkinson's disease (PD). However, such a term has since been widely used in the medical literature, even as a diagnostic label. While many authors have suggested that different disorders of PD lookalikes may account for a proportion of SWEDD cases, others have claimed that some of them may have a benign subtype of PD. Thus, there has been ensuing controversy and confusion and the use of this term continues without clarity of what it represents. We have systematically reviewed all the studies involving patients with SWEDD with the aim of shedding light on what these patients actually have. It becomes clear from this systematic review that while most 'SWEDD' cases are due to a clinical misdiagnosis of PD, there exists a small proportion of patients with SWEDD who may have PD on the basis of a positive levodopa response, clinical progression, imaging and/or genetic evidence. The latter challenge the seemingly incontrovertible relationship between dopaminergic tracer binding and the diagnosis of nigrostriatal parkinsonism, particularly PD. Patients with SWEDD are unlikely to reflect a single clinical entity and we suggest that the term SWEDD should be abandoned.

The long-term outcome of orthostatic tremor

OBJECTIVES

Orthostatic tremor is a rare condition characterised by high-frequency tremor that appears on standing. Although the essential clinical features of orthostatic tremor are well established, little is known about the natural progression of the disorder. We report the long-term outcome based on the largest multicentre cohort of patients with orthostatic tremor.

METHODS

Clinical information of 68 patients with clinical and electrophysiological diagnosis of orthostatic tremor and a minimum follow-up of 5 years is presented.

RESULTS

There was a clear female preponderance (76.5%) with a mean age of onset at 54 years. Median follow-up was 6 years (range 5-25). On diagnosis, 86.8% of patients presented with isolated orthostatic tremor and 13.2% had additional neurological features. At follow-up, seven patients who initially had isolated orthostatic tremor later developed further neurological signs. A total 79.4% of patients reported worsening of orthostatic tremor symptoms. These patients had significantly longer symptom duration than those without reported worsening (median 15.5 vs 10.5 years, respectively; p=0.005). There was no change in orthostatic tremor frequency over time. Structural imaging was largely unremarkable and dopaminergic neuroimaging (DaTSCAN) was normal in 18/19 cases. Pharmacological treatments were disappointing. Two patients were treated surgically and showed improvement.

CONCLUSIONS

Orthostatic tremor is a progressive disorder with increased disability although tremor frequency is unchanged over time. In most cases, orthostatic tremor represents an isolated syndrome. Drug treatments are unsatisfactory but surgery may hold promise.

The safety and efficacy of thalamic deep brain stimulation in essential tremor: 10 years and beyond

BACKGROUND

Deep brain stimulation (DBS) has proven to be a safe and effective therapy for refractory essential tremor, but information regarding long-term outcomes is lacking.

OBJECTIVES

We aimed to assess the long-term safety and efficacy of DBS in patients with essential tremor.

METHODS

Patients treated with DBS for essential tremor for at least 8 years were evaluated in the 'on' and 'off' state using the Fahn-Tolosa-Marin tremor rating scale, and their medical records were reviewed to assess complications related to this therapy.

RESULTS

We studied 13 patients (7 men): median age at evaluation 79 years (range 47-88), median age at electrode implantation 68 years (range 37-78) and mean time since electrode implantation 132.54±15.3 months (range 114-164). The difference between the 'off' and 'on' state on the motor items of the tremor rating scale was 41.9% (58.62 vs. 34.08, p<0.001) in the non-blinded and 37.2% (56.07 vs. 35.23, p<0.001) in the blinded rating. DBS provided a functional improvement of 31.7% in the 'on' state (15.07 vs. 22.07, p<0.001). A total non-blinded improvement in the tremor rating scale of 39% was observed in the 'on' state (49.15 vs. 80.69, p<0.001). Dysarthria and disequilibrium were common in patients with bilateral stimulation. A DBS-related surgery (electrode revision or internal pulse generator exchange) was necessary on average every 47.9 months to continue with the DBS therapy.

CONCLUSIONS

Thalamic DBS is a safe and effective therapy in patients with essential tremor followed for up to 13 years.

48, XXYY syndrome associated tremor

48, XXYY syndrome is a form of sex chromosome aneuploidy that affects between 1 in 18&emsp14;000 to 1 in 40&emsp14;000 males. It is not inherited and is diagnosed by karyotyping. It has similarities to 47, XXY Klinefelter's syndrome, with tall stature, micro-orchidism, hypergonadotropic hypogonadism and infertility in males. However, patients with 48, XXYY syndrome also commonly have dental problems, tremor, attention deficit disorder, learning difficulties, allergies and asthma. The tremor is typically reported as an intention tremor (in 71% of patients XXYY aged >20 years with 48), which becomes more common with age and worsens over time.

Pharmacology of tremor-producing amino alcohols

The pharmacological properties of a series of amino alcohols of the general formula RCH(NH2)&#x006d;̇(CH2)n&#x006d;̇C(OH)R2 have been studied The most striking action of these compounds is their ability to produce a sustained tremor, which is compared with those produced by other tremorogenic agents. The activities of various drugs as antagonists of the amino alcohol tremor are described.

INVOLUNTARY MOVEMENTS FOLLOWING STEREOTACTIC OPERATIONS FOR PARKINSONISM WITH SPECIAL REFERENCE TO HEMI-CHOREA (BALLISMUS)

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THE NEUROLOGICAL AND DEVELOPMENTAL EFFECTS OF NEONATAL HYPOGLYCEMIA: A FOLLOW-UP OF 22 CASES

Twenty-two infants in whom hypoglycemia (blood sugar less than 20 mg./100 ml.) was noted during the first few days of life were followed up when eight to 30 months of age. In eight such symptoms as muscular tremors, cyanosis, apneic spells and convulsions were associated with the hypoglycemia; five of these had abnormal central nervous system signs and retarded development. One other had possible impairment of development and another had a recurrence of hypoglycemia after having been well for four years. Fourteen of the 22 infants had no symptoms associated with the hypoglycemia, and on follow-up only two of these showed possible impairment. The rest were normal.This preliminary study suggests that hypoglycemia associated with neurological symptoms in the newborn period carries a poor prognosis with respect to permanent neurological damage. Asymptomatic hypoglycemia may have a relatively good prognosis.