A special role of the parvocellular red nucleus in lesion-induced spontaneous tremor in monkeys

Clinical Features, Neuroimaging, and Levodopa-Responsiveness in Holmes' Tremor: A Video-Based Case-Series with a Review of the Literature

BACKGROUND

Holmes' tremor (HT) is a low-frequency tremor characterized by a combination of rest, posture, and action components. We are reporting the clinical features, neuroimaging findings, and levodopa responsiveness in 12 patients with HT.

CASES

The majority of the patients were male (11/12). Dystonia was observed in 10 patients and the remaining two patients had head tremor, a "forme-fruste" of cervical dystonia. The underlying etiologies were vascular (n = 8), head trauma (n = 2), and tumor resection (n = 2). Neuroimaging showed isolated involvement of the midbrain in four, thalamus in two, and basal ganglia and cerebellum in one patient each. A combination of the lesion (thalamus and cerebellum = 2; cerebellopontine angle = 1, and cortical/subcortical = 1) was present in four patients. Levodopa responsiveness was seen in 75% of patients including one with levodopa-induced dyskinesia.

LITERATURE REVIEW

Of 139 patients from 49 studies, levodopa was tried in 123 patients. Improvement with levodopa was seen in 71 patients (57.72%). No improvement with levodopa was observed in 33 patients (26.82%) and details regarding therapeutic response were unavailable in 19 patients (15.44%).

CONCLUSIONS

Dystonia is an important clinical manifestation of HT. Levodopa responsiveness seen in the majority of the patients is consistent with the hypothesis that nigrostriatal pathway damage is crucial for the pathophysiology of HT.

Treatment-responsive Holmes tremor in a child with low-pressure hydrocephalus: video case report and systematic review of the literature

OBJECTIVE

Holmes tremor (HT) is a rare and debilitating movement disorder comprising both rest and action tremor, and it is known for its resistance to treatment. Its most common causes include ischemic or hemorrhagic insults and trauma. Mechanistically, the combined rest and action tremor is thought to require a double lesion of both the dopaminergic nigrostriatal system and the dentatorubrothalamic pathways, often near the midbrain where both pathways converge. The aim of this study was to characterize HT as a presenting sign in cases of hydrocephalus and to discuss potential pathomechanisms, clinical presentations, and treatment options.

METHODS

MEDLINE and Web of Science were searched for cases of HT with hydrocephalus from database inception to August 2021, and these were compiled along with the authors' own unique case of treatment-responsive HT in a child with low-pressure obstructive hydrocephalus secondary to a tectal tumor. Patient characteristics, presenting signs/symptoms, potential precipitating factors, interventions, and patient outcomes were recorded.

RESULTS

Nine patients were identified including the authors' video case report. All patients had a triventriculomegaly pattern with at least a component of obstructive hydrocephalus, and 4 patients were identified as having low-pressure hydrocephalus. Parinaud's syndrome and bradykinesia were the most commonly associated signs. Levodopa and CSF diversion were the most commonly used and effective treatments for HT in this population. This review was not registered and did not receive any funding.

CONCLUSIONS

HT is a poorly understood and probably underrecognized presentation of hydrocephalus that is difficult to treat, limiting the strength of the evidence in this review. Treatment options include CSF diversion, antiparkinsonian agents, antiepileptic agents, deep brain stimulation, and MR-guided focused ultrasound, and aim toward the nigrostriatal and dentatorubrothalamic pathways hypothesized to be involved in its pathophysiology.

Hypertrophic Olivary Degeneration and Holmes Tremor: Case Report and Review of the Literature

BACKGROUND

Hypertrophic olivary degeneration (HOD) is very rare type of degeneration that causes hypertrophy rather than atrophy. The classical presentation of HOD is palatal myoclonus. However, HOD may rarely present with Holmes tremor (HT). HT is unusual symptomatic tremor characterized by combination of rest and intention tremor. It has been reported in small case series, so far.

CASE DESCRIPTION

In this study, a man aged 62 years with HOD and HT spreading to the upper and lower extremities after pontine-midbrain hemorrhage due to cavernoma was presented.

CONCLUSIONS

Although pontine-midbrain hemorrhage may cause HT in the late period, HOD can be revealed on magnetic resonance imaging. Tract anatomy, especially the Guillain-Mollaret triangle, should be considered to explain the relationship between HT and HOD.

Current Opinions and Consensus for Studying Tremor in Animal Models

Tremor is the most common movement disorder; however, we are just beginning to understand the brain circuitry that generates tremor. Various neuroimaging, neuropathological, and physiological studies in human tremor disorders have been performed to further our knowledge of tremor. But, the causal relationship between these observations and tremor is usually difficult to establish and detailed mechanisms are not sufficiently studied. To overcome these obstacles, animal models can provide an important means to look into human tremor disorders. In this manuscript, we will discuss the use of different species of animals (mice, rats, fruit flies, pigs, and monkeys) to model human tremor disorders. Several ways to manipulate the brain circuitry and physiology in these animal models (pharmacology, genetics, and lesioning) will also be discussed. Finally, we will discuss how these animal models can help us to gain knowledge of the pathophysiology of human tremor disorders, which could serve as a platform towards developing novel therapies for tremor.

Tremor

Tremor is a phenomenon observed in a broad spectrum of diseases with different pathophysiologies. While patients with tremor may not complain in the clinic of symptoms of imbalance, gait difficulties, or falls, laboratory research studies using quantitative analysis of gait and posture and neurophysiologic techniques have demonstrated impaired gait and balance across a variety of tremor etiologies. These findings have been supported by careful epidemiologic studies assessing symptoms of imbalance. Imaging and neurophysiologic studies have identified cerebellar networks as important mediators of tremor, and therefore a likely common site of dysfunction to explain the phenomenologic overlap between impaired postural and gait control with tremor. Further understanding of these mechanisms and networks is of crucial importance in the development of new treatments, particularly surgical or minimally invasive lesional therapies.

Transsylvian Transuncal Approach for an Anterior Midbrain Cavernous Malformation Resection: A Case Report

BACKGROUND AND IMPORTANCE

Cavernous malformations (CMs) are vascular abnormalities with a hemorrhage risk of 0.2% to 5% per year, according to their location. Brainstem CMs seem to have a greater hemorrhagic risk and represent a neurosurgical challenge. We report here the first transsylvian transuncal (TS-TU) approach for an anteromedial mesencephalic CM resection.

CLINICAL PRESENTATION

A 29-yr-old female suddenly presented a left hemiparesis and central facial paresis with a diplopia in the upward gaze. A cerebral imagery revealed an 18-mm right cerebral peduncle CM with signs of acute hemorrhage. Two months later, she rebleed while pregnant. The pregnancy was interrupted. Five months later, a 3.0 Tesla magnetic resonance imaging (MRI) with diffusion tensor imaging sequences was realized for preoperative planning followed by a gross total resection of the CM through a TS-TU approach to avoid the perforating arteries of the anterior perforated substance. The patient presented postoperatively again a left hemiparesis and central facial paresis with a right oculomotor nerve paresis. On the tenth postsurgical day, she developed a Holmes’ tremor of the left upper limb, for which a Levodopa treatment was initiated. Three months postoperative, MRI showed a gross total resection of the mesencephalic CM without complications. A complete clinical recovery was observed 1 yr later.

CONCLUSION

We describe here the first performance of a TS-TU approach for an anterior mesencephalic CM resection. This surgical approach allowed direct access to the CM, avoiding the vascularization of the anterior perforated substance.

Generalized myoclonus: a rare manifestation of stroke

Movement disorders have been reported as rare complications of stroke. The basal ganglia have been implicated in the pathophysiology of most post-stroke dyskinesias. We outline different types of post-stroke myoclonus and their possible pathophysiology. A middle-aged man developed generalized myoclonus after an ischemic stroke in the superior midbrain and subthalamic nuclei. Spontaneous resolution was seen by 72 hours. A lesion to the subthalamic nuclei disrupted the normal thalamic inhibition, which likely led to the involuntary movements seen in our patient. In this case, myoclonus was generalized, which, to the best of our knowledge, has not been reported in the literature as a direct consequence of focal stroke.

Parkinson's disease tremor-related metabolic network: characterization, progression, and treatment effects

The circuit changes that mediate parkinsonian tremor, while likely differing from those underlying akinesia and rigidity, are not precisely known. In this study, to identify a specific metabolic brain network associated with this disease manifestation, we used FDG PET to scan nine tremor dominant Parkinson's disease (PD) patients at baseline and during ventral intermediate (Vim) thalamic nucleus deep brain stimulation (DBS). Ordinal trends canonical variates analysis (OrT/CVA) was performed on the within-subject scan data to detect a significant spatial covariance pattern with consistent changes in subject expression during stimulation-mediated tremor suppression. The metabolic pattern was characterized by covarying increases in the activity of the cerebellum/dentate nucleus and primary motor cortex, and, to a less degree, the caudate/putamen. Vim stimulation resulted in consistent reductions in pattern expression (p<0.005, permutation test). In the absence of stimulation, pattern expression values (subject scores) correlated significantly (r=0.85, p<0.02) with concurrent accelerometric measurements of tremor amplitude. To validate this spatial covariance pattern as an objective network biomarker of PD tremor, we prospectively quantified its expression on an individual subject basis in independent PD populations. The resulting subject scores for this PD tremor-related pattern (PDTP) were found to exhibit: (1) excellent test-retest reproducibility (p<0.0001); (2) significant correlation with independent clinical ratings of tremor (r=0.54, p<0.001) but not akinesia-rigidity; and (3) significant elevations (p<0.02) in tremor dominant relative to atremulous PD patients. Following validation, we assessed the natural history of PDTP expression in early stage patients scanned longitudinally with FDG PET over a 4-year interval. Significant increases in PDTP expression (p<0.01) were evident in this cohort over time; rate of progression, however, was slower than for the PD-related akinesia/rigidity pattern (PDRP). We also determined whether PDTP expression is modulated by interventions specifically directed at parkinsonian tremor. While Vim DBS was associated with changes in PDTP (p<0.001) but not PDRP expression, subthalamic nucleus (STN) DBS reduced the activity of both networks (p<0.05). PDTP expression was suppressed more by Vim than by STN stimulation (p<0.05). These findings suggest that parkinsonian tremor is mediated by a distinct metabolic network involving primarily cerebello-thalamo-cortical pathways. Indeed, effective treatment of this symptom is associated with significant reduction in PDTP expression. Quantification of treatment-mediated changes in both PDTP and PDRP scores can provide an objective means of evaluating the differential effects of novel antiparkinsonian interventions on the different motor features of the disorder.

Unilateral rubral tremor following treatment with risperidone

Rubral tremor is a rare movement disorder that occurs typically with midbrain damage. The main features of this tremor are its low frequency, irregular rhythm, presence at rest, and acceleration during posture and active movement. Antipsychotic agent-induced tremors are usually bilateral parkinsonian tremors. We found no previous reports of unilateral rubral tremor in the literature. A 23-year-old man had unilateral rubral tremors as a result of a midbrain lesion plus risperidone exposure for treatment of manic symptoms. After we stopped the use of risperidone, the tremor became less apparent and then disappeared. This case highlights the importance of being aware of this rare complication in susceptible patients receiving risperidone treatment.

SPECT imaging, immunohistochemical and behavioural correlations in the primate models of Parkinson's disease

Dopamine active transporter (DAT) single photon emission computerised tomography (SPECT) is considered a useful and practical technique for early diagnosis of Parkinson's disease (PD) and assessment of its progression. The application of this technique, particularly as a surrogate marker for therapeutic and neuroprotective trials in Parkinsonism, however, is dependent on pathological validation. In the absence of human studies, we used 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) primate models of Parkinsonism to verify correlation between the SPECT, immunohistochemical and behavioural data. The DAT SPECT data correlated strongly and significantly with the substantia nigra pars compacta tyrosine hydroxylase and Nissl cell counts as well as the behavioural scores. Within the limitations of small numbers inherent to such studies, this data provides the first attempt at pathological validation of SPECT in primates.

Cell survival patterns in the pedunculopontine tegmental nucleus of methyl-4-phenyl-1,2,3,6-tetrahydropyridine-treated monkeys and 6OHDA-lesioned rats: evidence for differences to idiopathic Parkinson disease patients?

We explore the patterns of cell loss in the pedunculopontine tegmental nucleus (PpT), a major locomotor and muscle tone suppression centre of the brainstem, in two animal models of Parkinson disease, namely MPTP (methyl-4-phenyl-1,2,3,6-tetrahydropyridine)-treated monkeys and 6-hydroxydopamine(6OHDA)-lesioned rats. Although there have been many studies documenting the loss of dopaminergic cells from the substantia nigra in these animal models, there has been little, if any, documentation of a loss of cells in the PpT. Results were obtained from macaque monkeys (Macaca fascicularis) and Sprague-Dawley rats. For the monkey series, animals were injected intramuscularly with MPTP (0.2 mg/kg) for 8 days consecutively and then allowed to survive for 21 days thereafter. Each monkey underwent behavioural assessment for parkinsonian symptoms. For the rat series, 6OHDA was injected into the midbrain using stereotactic coordinates. Rats were then allowed to survive for either 7, 14, 28, or 84 days thereafter. Monkey and rat brains were aldehyde-fixed and processed for routine tyrosine hydroxylase (TH; to label nigral dopaminergic cells) and nitric oxide synthase (NOs; to label PpT cholinergic cells) immunocytochemistry. In monkeys, the morphology, distribution and number of NOs(+) cells in the controls and MPTP-treated cases were very similar. In fact, in terms of number, there was only a 1% difference in the mean cell number between the controls and MPTP-treated cases. A comparable pattern was evident in 6OHDA-lesioned rats; there was no substantial difference in morphology, distribution and number of NOs(+) cells on the 6OHDA-lesioned cases when compared to the controls at each of the survival periods post-surgery. In summary, we show no loss of the large cholinergic/NOs(+) cells in the PpT in two animal models of Parkinson disease. This is in contrast to the heavy loss of these cells reported by previous findings in idiopathic Parkinson disease in patients.

Differential survival patterns among midbrain dopaminergic cells of MPTP-treated monkeys and 6OHDA-lesioned rats

We explore the patterns of survival among dopaminergic cells of the midbrain in MPTP-treated macaque monkeys and 6OHDA-lesioned Sprague-Dawley rats. For the monkeys, animals were injected intramuscularly with MPTP for 8 days consecutively and then allowed to survive for 21 days. For the rats, 6OHDA was injected into the midbrain and then allowed to survive for either 7, 28 or 84 days. Brains were processed for tyrosine hydroxylase (TH) and calbindin immunocytochemistry to label populations in the ventral and dorsal tiers of midbrain dopaminergic cells. In monkeys, while there was a decrease in the TH+ cell number in the ventral tier of MPTP-treated cases (65%), there was an overall increase (22%) in the TH+ and calbindin+ cell number in the dorsal tier. Double labelling studies indicate that approximately 50% of TH+ cells of the dorsal tier contain calbindin also. In rats, there was a decrease in TH+ cell number in the ventral tier of 6OHDA-lesioned cases (97%), and to a lesser extent, in the TH+ and calbindin+ cell number in the dorsal tier ( approximately 40%). In conclusion, we show a surprising increase in TH+ and calbindin+ cell number in the dorsal tier in response to MPTP insult; such an increase was not evident after 6OHDA insult. We suggest that the increase in antigen expression relates to the dopaminergic reinnervation of the striatum in MPTP-treated cases. We also suggest that the greater loss of dopaminergic cells in the ventral tier when compared to the dorsal tier relates to glutamate toxicity.

Head tremor and progressive multifocal leukoencephalopathy in AIDS patients: report of two cases

Progressive multifocal leukoencephalopathy (PML) is caused by replication of JC virus in oligodendrocytes of immunocompromised patients. Common manifestations are focal motor and sensory deficits, gait abnormalities, speech and language disturbances, cognitive disorders, headache, and visual impairment. Although the occurrence of movement disorders is rare in PML, bradykinesia, rigidity, dystonia, myoclonic jerks and myoclonic ataxia have been described. Head tremor associated with PML has not been previously reported. We report two cases of PML in whom head tremor was present.

Possible necessity for deep brain stimulation of both the ventralis intermedius and subthalamic nuclei to resolve Holmes tremor. Case report

Holmes tremor is characterized by resting, postural, and intention tremor. Deep brain stimulation (DBS) of both the nucleus ventralis intermedius (Vim) and the subthalamic nucleus (STN) may be required to control these three tremor components. A 79-year-old man presented with a long-standing combination of resting, postural, and intention tremor, which was associated with severe disability and was resistant to medical treatment. Neuroimaging studies failed to reveal areas of discrete brain damage. A DBS device was placed in the Vim and produced an improvement in both the intention and postural tremor, but there was residual resting tremor, as demonstrated by clinical observation and quantitative tremor analysis. Placement of an additional DBS device in the STN resolved the resting tremor. Stimulation of the Vim or STN alone failed to produce global resolution of mixed tremor, whereas combined Vim-STN stimulation produced global relief without creating noticeable side effects. Combined Vim-STN stimulation can thus be a safe and effective treatment for Holmes tremor.

Holmes tremor in association with bilateral hypertrophic olivary degeneration and palatal tremor: chronological considerations. Case report

Hypertrophic olivary degeneration (HOD) is a rare type of neuronal degeneration involving the dento-rubro-olivary pathway and presents clinically as palatal tremor. We present a 48 year old male patient who developed Holmes' tremor and bilateral HOD five months after brainstem hemorrhage. The severe rest tremor was refractory to pharmacotherapy and botulinum toxin injections, but was markedly reduced after thalamotomy. Magnetic resonance imaging permitted visualization of HOD, which appeared as a characteristic high signal intensity in the inferior olivary nuclei on T2- and proton-density-weighted images. Enlargement of the inferior olivary nuclei was also noted. Palatal tremor was absent in that moment and appears about two months later. The delayed-onset between insult and tremor following structural lesions of the brain suggest that compensatory or secondary changes in nervous system function must contribute to tremor genesis. The literature and imaging findings of this uncommon condition are reviewed.

Experimental parkinsonism in primates

Early in the 1960s the primate model of Parkinson's disease was first introduced by placing an electrolytic lesion in the midbrain. In the 1980s, a dopaminergic neurotoxin, 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) was accidentally shown to induce parkinsonism in humans, and subsequently was confirmed to reproduce an almost perfect model of parkinsonism in primates. In the late 1980s chemical manipulations of the basal ganglia were shown to induce parkinson symptoms, especially dyskinesia, and more recently, chemical lesioning of the pedunculopontine tegmental nucleus has also been shown to induce parkinsonism. We still do not have a perfect animal model of parkinsonism, however, these models have offered excellent opportunities to study the basic mechanisms in parkinsonism and the function of the basal ganglia.

Deep brain stimulation of the ventral intermediate nucleus of the thalamus for control of tremors in Parkinson's disease and essential tremor

The beneficial effects of ventral intermediate nucleus (VIM) stimulation were evaluated in 20 patients with tremor refractory to medical therapy. Thalamic stimulation is a non-ablative procedure which has the advantage of a reversible, non-destructive lesion. Eleven patients [7 with Parkinson's disease (PD) and 4 with essential tremor (ET)] received unilateral VIM implantation, while 9 patients had staged bilateral VIM implantation (4 with PD, 5 with ET). PD patients showed a significant improvement in contralateral arm and leg rest tremor and ipsilateral leg rest tremor (p < 0.02) at a mean follow-up period of 16.2 +/- 7.0 months. Patients with PD did not demonstrate any significant decrease in medication use at follow-up. ET patients demonstrated significant improvement in postural and action tremor in the contralateral arm (p < 0.001), but no significant improvement in the contralateral leg tremor at follow-up. Significant improvements were also seen in ET patients in the Clinical Rating Scale for Tremor (p < 0.001) with respect to several activities of daily living at a mean follow-up of 14.9 +/- 8. 1 months. Deep brain stimulation is a safe and effective treatment for severe tremor refractory to medications. It is a highly effective, reversible, adaptable, and predictable procedure which avoids the complication of cognitive deficit seen in patients with bilateral thalamotomies.

Animal models of tremor

Animal models of tremor have been widely used in experimental neurology, because they are an indispensable requirement for understanding the pathophysiology of human tremor disorders and the development of new therapeutic agents. This review focuses on three approaches to produce tremor in animals (application of tremorgenic drugs, experimental central nervous system lesions, study of genetic mutants) and their use in simulating tremor syndromes of humans. Whereas harmaline induces a postural/kinetic tremor in animals that shares some features with human essential tremor/enhanced physiological tremor, MPTP tremor is the best model available for rest tremor in people. The tremor following experimental lesion of the ventromedial tegmentum in primates closely resembles Holmes tremor in humans, whereas cerebellar intention tremor is mimicked by cooling of the lateral cerebellar nuclei. The "campus syndrome," discovered in a breed of Pietrain pigs, might be a useful model of human orthostatic tremor. However, no animal model has yet been generated that exactly recreates all features of any of the known tremor disorders in humans. Problems encountered when comparing tremor in animals and humans include differing tremor frequencies and the uncertainty, if specific transmitter abnormalities/central nervous system lesions seen in animal tremor models are characteristic for their human counterparts. The search for adequate tremor models continues.

Function of the cerebellum in Parkinsonian rest tremor and Holmes' tremor

We describe a patient who developed Parkinson's disease (PD) 17 years after resection of his right cerebellum because of a Lindau tumor. He showed a classic 4.3-Hz resting tremor on the left side but a 3.1-Hz resting, postural, and intention tremor on the right side compatible with midbrain tremor (Holmes' tremor). We conclude that the generator of the tremor in PD cannot be located within the olivocerebellar loop. The cerebellum, however, seems to modulate the tremor frequency of parkinsonian rest tremor and may prevent the rest tremor from transforming into a postural and goal-directed tremor.

Animal models of action tremor

This article is devoted to animal models of tremors that emerge from lesions in the Guillain-Mollaret triangle. Cerebellar intention tremor is caused by lesions in the brachium conjunctivum or in the interpositus nucleus, possibly in combination with damage to the dentate nucleus. Impaired feed-forward motor control delays the braking of rapid movements, resulting in target overshoot and subsequent oscillation. Transcortical and transcerebellar sensorimotor loops undergo oscillation at a frequency that depends on the mechanical properties of the limb and the length of the sensorimotor loop (mechanical reflex oscillation). The crescendo quality of intention tremor may be a result of amplification of tremor in reverberating brain stem-cerebellar or thalamocortical loops. So-called rubral or midbrain tremor is caused by a combination of damage to the brachium conjunctivum and nigrostriatal pathways in the vicinity of the red nucleus. Secondary compensatory changes in the motor system are probably involved because midbrain tremor in people usually begins weeks or months after a midbrain stroke or trauma. Harmaline causes enhanced neuronal synchrony and rhythmicity in the inferior olive; this animal model, although as yet unproven, is the most popular one for essential tremor (ET). Additional studies in laboratory animals are needed to define the seemingly universal involvement of the cerebellum and ventrolateral thalamus (ventralis intermedius [Vim]) in virtually all human tremor disorders.

Central mechanisms of tremor

Physiologic and pathologic tremors are mechanistically classified into two broad groups: (1) those produced by oscillation in sensorimotor loops, so-called mechanical-reflex tremors, and (2) those produced by the oscillatory properties of central neuronal networks. This review provides a contemporary perspective of tremor pathophysiology while acknowledging that no form of tremor is understood completely. Indeed, the origin of oscillation in most forms of tremor is undefined, and in many instances the underlying pathology is unknown.

Chronic electrical stimulation of the ventralis intermedius nucleus of the thalamus as a treatment of movement disorders

Tremor was suppressed by test stimulation of the thalamic ventralis intermedius (VIM) nucleus at high frequency (130 Hz) during stereotaxy in nonanesthetized patients suffering from Parkinson's disease or essential tremor. Ventralis intermedius stimulation has since been used by the authors over the last 8 years as a treatment in 117 patients with movement disorders (80 cases of Parkinson's disease, 20 cases of essential tremor, and 17 cases of various dyskinesias and dystonias including four multiple sclerosis). Chronic electrodes were stereotactically implanted in the VIM and connected to a programmable stimulator. Results depend on the indication. In Parkinson's disease patients, tremor, but not bradykinesia and rigidity, was selectively suppressed for as long as 8 years. Administration of L-Dopa was decreased by more than 30% in 40 Parkinson's disease patients. In essential tremor patients, results were satisfactory but deteriorated with time in 18.5% of cases, mainly for patients who presented an action component of their but deteriorated with time in 18.5% of cases, mainly for patients who presented an action component of their tremor. In other types of dyskinesias (except multiple sclerosis), results were much less favorable. Fifty-nine patients underwent bilateral implantation and 14 other patients received implantation contralateral to a previous thalamotomy. Thirty-seven patients (31.6%) experienced minor side effects, which were always well tolerated and immediately reversible. Three secondary scalp infections led to temporary removal of the implanted material. There was no permanent morbidity. This tremor suppression effect could be due to the inhibition or jamming of a retroactive loop. Chronic VIM stimulation, which is reversible, adaptable, and well tolerated even by patients undergoing bilateral surgery (74 of 117 patients) and by elderly patients, should replace thalamotomy in the regular surgical treatment of parkinsonian and essential tremors.

Treatment of post-traumatic midbrain resting-kinetic tremor with combined levodopa/carbidopa and carbamazepine

A patient with a post-traumatic midbrain haemorrhagic lesion documented by magnetic resonance imaging (MRI) presented with a combined resting-kinetic contralateral upper extremity tremor. The resting tremor component responded to levodopa/carbidopa, while the kinetic component improved with the addition of carbamazepine.