Post-traumatic midbrain tremors

Unilateral deep brain stimulation (DBS) of nucleus ventralis intermedius thalami (Vim) for the treatment of post-traumatic tremor in children: a multicentre experience

PURPOSE

Deep brain stimulation (DBS) of nucleus ventralis intermedius thalami (Vim) is a validated technique for the treatment of essential tremor (ET) in adults. Conversely, its use for post traumatic tremor (PTT) and in paediatric patients is still debated. We evaluated the efficacy of Vim-DBS for lesional tremor in three paediatric patients with drug-resistant post-traumatic unilateral tremor.

METHODS

We retrospectively collected data regarding three patients with unilateral tremor due to severe head injury, with no MRI evidence of basal ganglia lesions. The three patients underwent stereotactic frame-based robot-assisted DBS of Vim contralateral to the tremor side.

RESULTS

Mean follow-up was 48 months (range: 36-60 months). Tremor was reduced in all patients with a better control of voluntary movements and improvement of functional status (mean FIM scale improvement + 7 points). No surgical complications occurred.

CONCLUSION

Unilateral contralateral DBS of Vim could be efficacious in post-traumatic tremor, even in paediatric patients and should be offered in PTT drug-resistant patients.

Benedikt syndrome in a 74-year-old hypertensive woman: A case report

Benedikt syndrome is a rare neurological disorder of the midbrain. Herein, we present a case of Benedikt syndrome, who presented with left-sided body weakness, right oculomotor nerve palsy, cerebellar ataxia, and Holmes tremor in the left upper limb following midbrain infarction. She was treated with aspirin, clopidogrel, and amiodarone.

Study on the pathogenesis of Holmes tremor by multimodal 3D medical imaging: case reports of three patients

Background

We examined for the first time the imaging characteristics of Holmes tremor (HT) through multimodal 3D medical imaging.

Case presentation

Three patients with Holmes tremor who visited the Affiliated Hospital of Chengdu University of TCM from August 2018 to April 2021 were retrospectively investigated to summarize their clinical and imaging data.

Results

Holmes tremor in two of the three patients was caused by hypertensive cerebral hemorrhage and in the third patient induced by hemorrhage due to ruptured brain arteriovenous malformations. HT occurred 1 to 24 months after the primary disease onset and manifested as a tremor in the contralateral limb, mostly in the upper portion. Cranial MRI showed that the lesions involved the thalamus in all three patients. The damaged thalamic nuclei included the ventral anterior nucleus, ventral lateral nucleus and ventromedial lateral nucleus, and the damaged nerve fibers included left thalamocortical tracts in one patient. In the other two patients, the damaged thalamic nuclei included the centromedian and dorsomedial nucleus, and the damaged nerve fibers included left cerebellothalamic and thalamocortical tracts. One patient showed significant improvement after treatment with pramipexole while the other two patients exhibited a poor response, one of whom had no response to the treatment with pramipexole and was only significantly relieved by clonazepam.

Conclusion

We used multimodal 3D medical imaging for the first time to analyze the pathogenesis of HT and found that multiple thalamic nuclei were damaged. The damaged nuclei and nerve fiber tracts of two patients were different from those of the third patient, with different clinical manifestations and therapeutic effects. Therefore, it is speculated that there may be multiple pathogeneses for HT.

Damage to the central nucleus of the thalamus via atypical Holmes tremor: a case report

Holmes tremor (HT) is a rare symptomatic movement disorder characterized by a combination of resting, postural, and action tremors. HT is usually caused by lesions in the brain stem, thalamus, and cerebellum, and the pathogenesis is believed to be related to the nigrostriatal pathway and/or the cerebello–thalamo–cortical pathway. Many medications have been used to treat HT with various degrees of effectiveness. We herein present a case involving an elderly woman who developed atypical HT 23 months after cerebral hemorrhage. The atypical HT manifested as a tremor of the right limb with involuntary flexion of the distal five fingers of the right upper limb. Imaging findings suggested the existence of an old hemorrhage in the left thalamus. Specifically, diffusion tensor imaging data of the whole brain and multimodal three-dimensional medical imaging revealed significant white matter microstructural changes in the centromedian nucleus of the left thalamus. Treatment with high-dose oral levodopa was not efficient, but the symptoms gradually decreased in severity and disappeared 1 month after switching to oral clonazepam treatment.

Using Preimplanted Deep Brain Stimulation Electrodes for Rescue Thalamotomy in a Case of Holmes Tremor: A Case Report and Review of the Literature

BACKGROUND

Chronic stimulation of the thalamus is a surgical option in the management of intractable Holmes tremor. Patients with deep brain stimulation (DBS) can encounter infection as a postoperative complication, necessitating explantation of the hardware. Some studies have reported on the technique and the resulting efficacy of therapeutic lesioning through implanted DBS leads before their explantation.

CASE DESCRIPTION

We report the case of a patient with Holmes tremor who had stable control of symptoms with DBS of the nucleus ventralis intermedius of the thalamus (VIM) but developed localized infection over the extension at the neck, followed by gradual loss of a therapeutic effect as the neurostimulator reached the end of its service life. Three courses of systemic antibiotic therapy failed to control the infection. After careful consideration, we decided to make a rescue lesion through the implanted lead in the right VIM before explanting the complete DBS hardware. The tremor was well controlled after the rescue lesion procedure, and the effect was sustained during a 2-year follow-up period.

CONCLUSION

This case and the previously discussed ones from the literature demonstrate that making a rescue lesion through the DBS lead can be the last plausible option in cases where the DBS system has to be explanted because of an infection and reimplantation is a remote possibility.

Holmes' or functional tremor?

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We report the case of an Holmes tremor with atypical features.

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The association between Holmes and functional tremor has never been reported before.

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We propose a fast battery for the differential diagnosis of functional tremor.

Objective

Holmes tremor is a rare kind of hyperkinetic movement disorder, clinically characterized by irregular, monolateral, high-amplitude jerks, sharing a quite similar frequency with those observed in Parkinson’s disease; its generation likely relies on a combined involvement of cerebello-thalamic and nigrostriatal pathways.

Methods

We report the case of a man with a combined resting-postural-kinetic tremor. Neuroimaging revealed an intracranial dermoid cyst at the right pontocerebellar angle with brainstem dislocation. We performed an extensive electrophysiological assessment from the extensor digitorum communis (EDC) and flexor carpi radialis (FCR) muscles.

Results

Both the spontaneous variability of tremor frequency and frequency entrainment argued against an organic aetiology. Polymyography revealed: 1) a paradoxical increase of tremor amplitude with mass loading; 2) jerks’ synchronization between antagonistic muscles during voluntary contralateral motor performances; 3) tremor inhibition while asking the patient to make a ballistic movement.

Conclusions

We suggest a complete psychogenic genesis or, at least in part, a possible co-existence of a rubral tremor with functional traits.

Significance

Here, we propose a simple and fast test battery for an early diagnosis of functional tremor. Our results prompt further studies to re-define electrodiagnostic criteria in hyperkinetic movement disorders, possibly updating the floating border between organic and psychogenic disease.

Bilateral Hypertrophic Olivary Degeneration and Holmes Tremor without Palatal Tremor: An Unusual Association

BACKGROUND

Lesions in the Guillain-Mollaret triangle or dentate-rubro-olivary pathway may lead to hypertrophic olivary degeneration (HOD), a secondary trans-synaptic degeneration of the inferior olivary nucleus. HOD is usually associated with palatal tremor and rarely with Holmes tremor. Bilateral HOD is a very unusual condition and very few cases are reported.

CASE REPORT

We report here two cases of bilateral HOD after two different vascular lesions located at the decussation of superior cerebellar peduncles, thus impairing both central tegmental tracts and interrupting bilaterally the dentate-rubral-olivary pathway. Interestingly, both developed bilateral Holmes tremor but not palatal tremor.

DISCUSSION

Lesions in some of the components in the Guillain-Mollaret triangle may develop Holmes tremor with HOD and without palatal tremor. Magnetic resonance imaging is an invaluable tool in these cases. Better understanding of the pathways in this loop is needed.

Holmes tremor: Clinical description, lesion localization, and treatment in a series of 29 cases

OBJECTIVE

To describe the clinical features, etiology, findings from neuroimaging, and treatment results in a series of 29 patients with Holmes tremor (HT).

METHODS

A retrospective study was performed based on review of medical records and videos of patients with HT diagnosis.

RESULTS

A total of 16 women and 13 men were included. The mean age at the moment of CNS insult was 33.9 ± 20.1 years (range 8-76 years). The most common causes were vascular (48.3%), ischemic, or hemorrhagic. Traumatic brain injury only represented 17.24%; other causes represented 34.5%. The median latency from lesion to tremor onset was 2 months (range 7 days-228 months). The most common symptoms/signs associated with HT were hemiparesis (62%), ataxia (51.7%), hypoesthesia (27.58%), dystonia (24.1%), cranial nerve involvement (24.1%), and dysarthria (24.1%). Other symptoms/signs were vertical gaze disorders (6.8%), bradykinesia/rigidity (6.8%), myoclonus (3.4%), and seizures (3.4%). Most of the patients had lesions involving more than one area. MRI showed lesions in thalamus or midbrain or cerebellum in 82.7% of the patients. Levodopa treatment was effective in 13 out of 24 treated patients (54.16%) and in 3 patients unilateral thalamotomy provided excellent results.

CONCLUSIONS

The most common causes of HT in our series were vascular lesions. The most common lesion topography was mesencephalic, thalamic, or both. Treatment with levodopa and thalamic stereotactic lesional surgery seems to be effective.

Holmes tremor: Clinical description, lesion localization, and treatment in a series of 29 cases

OBJECTIVE

To describe the clinical features, etiology, findings from neuroimaging, and treatment results in a series of 29 patients with Holmes tremor (HT).

METHODS

A retrospective study was performed based on review of medical records and videos of patients with HT diagnosis.

RESULTS

A total of 16 women and 13 men were included. The mean age at the moment of CNS insult was 33.9 ± 20.1 years (range 8-76 years). The most common causes were vascular (48.3%), ischemic, or hemorrhagic. Traumatic brain injury only represented 17.24%; other causes represented 34.5%. The median latency from lesion to tremor onset was 2 months (range 7 days-228 months). The most common symptoms/signs associated with HT were hemiparesis (62%), ataxia (51.7%), hypoesthesia (27.58%), dystonia (24.1%), cranial nerve involvement (24.1%), and dysarthria (24.1%). Other symptoms/signs were vertical gaze disorders (6.8%), bradykinesia/rigidity (6.8%), myoclonus (3.4%), and seizures (3.4%). Most of the patients had lesions involving more than one area. MRI showed lesions in thalamus or midbrain or cerebellum in 82.7% of the patients. Levodopa treatment was effective in 13 out of 24 treated patients (54.16%) and in 3 patients unilateral thalamotomy provided excellent results.

CONCLUSIONS

The most common causes of HT in our series were vascular lesions. The most common lesion topography was mesencephalic, thalamic, or both. Treatment with levodopa and thalamic stereotactic lesional surgery seems to be effective.

Caudal Zona Incerta/VOP Radiofrequency Lesioning Guided by Combined Stereotactic MRI and Microelectrode Recording for Posttraumatic Midbrain Resting-Kinetic Tremor

OBJECTIVE

Reporting the outcome of two patients who underwent unilateral ablative stereotactic surgery to treat pharmacologic resistant posttraumatic tremor (PTT).

METHODS

We present two patients (31 and 47 years old) with refractory PTT severely affecting their quality of life. Under stereotactic guidance, refined by T2-weighted magnetic resonance imaging and double-channel multiunit microelectrode recording (MER), three sequential radiofrequency lesions were performed in the caudal zona incerta (cZi) up to the base of thalamus (VOP). Effects of cZi/VOP lesion were prospectively rated with a tremor rating scale.

RESULTS

Both patients demonstrated intraoperative tremor suppression with sustained results up to 18 months follow-up, with improvement of 92% and 84%, respectively, on the tremor rating scale. Tremor improvement was associated with enhancement functionality and quality of life for the patients. The patients returned to their work after the procedure. No adverse effects were observed up to the last follow-up.

CONCLUSION

Radiofrequency lesion of the cZi/VOP target was effective for posttraumatic tremor in both cases. The use of T2-weighted images and MER was found helpful in increasing the precision and safety of the procedure, because it leads the RF probe by relying on neighbor structures based on thalamus and subthalamic nucleus.

Movement disorders secondary to craniocerebral trauma

Over the past few decades it has been recognized that traumatic brain injury may result in various movement disorders. In survivors of severe head injury, post-traumatic movement disorders were reported in about 20%, and they persisted in about 10% of patients. The most frequent persisting movement disorder in this population is kinetic cerebellar outflow tremor in about 9%, followed by dystonia in about 4%. While tremor is associated most frequently with cerebellar or mesencephalic lesions, patients with dystonia frequently have basal ganglia or thalamic lesions. Moderate or mild traumatic brain injury only rarely causes persistent post-traumatic movement disorders. It appears that the frequency of post-traumatic movement disorders overall has been declining which most likely is secondary to improved treatment of brain injury. In patients with disabling post-traumatic movement disorders which are refractory to medical treatment, stereotactic neurosurgery can provide long-lasting benefit. While in the past the primary option for severe kinetic tremor was thalamotomy and for dystonia thalamotomy or pallidotomy, today deep brain stimulation has become the preferred treatment. Parkinsonism is a rare consequence of single head injury, but repeated head injury such as seen in boxing can result in chronic encephalopathy with parkinsonian features. While there is still controversy whether or not head injury is a risk factor for the development of Parkinson's disease, recent studies indicate that genetic susceptibility might be relevant.

Clinical neurophysiology in movement disorders

Neurophysiological tools are very helpful in characterizing various movement disorders, consequently guiding etiological research and therapy. Movement disorders recordings are currently underutilized in neurological practice in adults and could also be extended to the pediatric population. Surface polymyography (EMG) combined with accelerometry is commonly used for the analysis of many types of hyperkinetic movement disorders, mainly myoclonus, tremor, dystonia, and sometimes tics and chorea. To study myoclonus, techniques exploring cortical excitability, namely conventional EEG, EEG-jerk-locked-back-averaging (JLBA), somatosensory evoked potentials (SEP) and C-reflex studies, should necessarily complete the EMG analysis. Premovement potential recording and measures of the stimulus induced jerks latencies may help to differentiate psychogenic jerks from myoclonus. The field of clinical usefulness of movement disorders recordings is large. Main issues are: (1) to differentiate tremor from myoclonus, (2) to demonstrate and locate dystonic features, either isolated or associated to tremor and myoclonus, (3) to define the nature of a tremor, (4) to assess the psychogenic nature of a tremor or jerks, and (5) to define the neurophysiological generator of myoclonus in the central nervous system. Neurophysiological data allow us to clearly classify myoclonus as cortical, cortico-thalamic, and subcortical-resulting from lesions or dysfunctions of basal ganglia/reticular system-or spinal.

An Overview of Surgical Therapy for Movement Disorders

Surgical treatments are an important consideration in the management of many movement disorders, particularly for patients refractory to medications. Increasing number of published reports have demonstrated an overall improvement in motor function, activities of daily living and quality of life particularly with deep brain stimulation. In addition the procedure is also relatively safe. In this article, we review the various types of movement disorders that may benefit from surgical intervention.

Advances in neuropharmacological rehabilitation for brain dysfunction

The use of pharmacological agents as rehabilitative tools following brain injury remains to some degree both a science and an art. Recent work in the area of the neural sciences has shed new light on the workings of basic CNS neurochemical systems and the use of pharmacologic agents in altering central neurophysiologic processes. The major central neurochemical systems are reviewed both anatomically and physiologically. An overview is provided of basic neuropharmacologic agents by class. Lastly, some of the newer neuropharmacological options for treatment of post-acute brain injury deficits are examined.

Holmes tremor secondary to brainstem hemorrhage responsive to levodopa: report of 2 cases

We report 2 patients who presented a brainstem hemorrhage and who, after 1 and 6 months, respectively, developed a 4-Hz postural and resting tremor consistent with Holmes tremor, which severely interfered with the activities of daily living. In both cases, levodopa dramatically improved the tremor. Pharmacological treatment of this condition is usually disappointing, and surgical procedures are commonly required for severe cases. Our patients, together with 13 others gleaned from the literature, suggest that in cases of Holmes tremor secondary to brainstem hemorrhage, levodopa can be a useful treatment, and it should be tested before considering invasive therapies.

Differential diagnosis of common tremor syndromes

Tremor is one of the most common involuntary movement disorders seen in clinical practice. In addition to the detailed history, the differential diagnosis is mainly clinical based on the distinction at rest, postural and intention, activation condition, frequency, and topographical distribution. The causes of tremor are heterogeneous and it can present alone (for example, essential tremor) or as a part of a neurological syndrome (for example, multiple sclerosis). Essential tremor and the tremor of Parkinson's disease are the most common tremors encountered in clinical practice. This article focuses on a practical approach to these different forms of tremor and how to distinguish them clinically. Evidence supporting various strategies used in the differentiation is then presented, followed by a review of formal guidelines or recommendations when they exist.

Successful treatment of rubral tremor by high-dose trihexyphenidyl: a case report

A 24-year-old male suffered from acute-onset right-sided hemiparesis, dysarthria, and ophthalmoplegia in February 2001. Brain magnetic resonance imaging revealed a cavernous angioma with hemorrhage over the left thalamus. Moreover, some rhythmic, coarse, low-frequency (2-3 Hz) oscillation over the right wrist and elbow was noted 1 month later. Action tremor was more predominant than resting tremor. Rubral tremor was diagnosed on the basis of the clinical presentation and tremography analysis. Rubral tremor is not unusual, and pharmacotherapy is nearly always ineffective in clinical practice. Deep brain stimulation, thalamotomy, and pallidotomy are all considered effective according to recent research. However, they are either very expensive or invasive, and involve surgical risks. In our patient, we tried valproate, clonazepam, and verapamil one after another, but all in vain. Finally, titration of trihexyphenidyl provided significant benefit. The tremor was successfully controlled by a single high daily dose of trihexyphenidyl (38 mg) without severe or uncomfortable side effects. Here, we report a case of successful monotherapy of rubral tremor with high-dose trihexyphenidyl.

Hemiparkinsonism and levodopa-induced dyskinesias after focal nigral lesion

We present a patient with tremor-dominant hemiparkinsonism after a focal lesion to the substantia nigra. An excellent response to levodopa was complicated by rapid development of motor fluctuations and disabling dyskinesias. Stereotactic thalamotomy resulted in a persistent extinction of parkinsonism and of dyskinesias along with stopping dopaminergic treatment.

Thalamic deep brain stimulation for posttraumatic action tremor

We report a case of thalamic deep brain stimulation (DBS) for treatment of posttraumatic tremor. An 18-year-old right-handed man developed a disabling and medically refractory action tremor in the right upper extremity 9 months after sustaining diffuse axonal injury in a motor vehicle collision. DBS of the left ventral intermediate nucleus of the thalamus (Vim) suppressed the tremor without complication and should be considered as an option for the management of intractable posttraumatic tremor.

Approche chirurgicale d’un tremblement de Holmes associé à un tremblement synchrone de haute fréquence

INTRODUCTION

The effectiveness of thalamic stimulation is now clearly demonstrated for essential tremor, but remains to be demonstrated for other types of tremor.

OBSERVATION

A young woman presented Holmes' tremor resulting from a pontine tegmental hemorrhage related to an arteriovenous malformation. A surgical approach was considered when major functional impairment persisted at 2-year follow-up despite drug therapy. The patient underwent unilateral thalamic deep brain stimulation (Vim); major improvement persisted at eighteen months follow-up.

CONCLUSION

This observation is in line with previous reports suggesting that thalamic surgery can be one of the best options for treating medically intractable Holmes' tremor. The mechanism underlying the tremor, implying dentate-rubro-thalamic pathways is discussed. Moreover, the patient exhibited short periods of 16Hz tremor when her arms were maintained outstretched. Thalamic stimulation also appears to be effective for these high-frequency synchronous cerebellar bursts.

Posttraumatic tremor without parkinsonism in a patient with complete contralateral loss of the nigrostriatal pathway

We present a patient with posttraumatic tremor who did not show any [(123)I]FP-CIT uptake in the contralateral putamen and caudate. The absence of hypokinesia and rigidity is surprising in the presence of a striatal dopaminergic denervation that is even more severe than in Parkinson's disease. An explanation, therefore, could be that the lesion in the subthalamic nucleus in our patient prevented the onset of a Parkinson syndrome.

Head injury and posttraumatic movement disorders

WE REVIEW THE phenomenology, pathophysiology, pathological anatomy, and therapy of posttraumatic movement disorders with special emphasis on neurosurgical treatment options. We also explore possible links between craniocerebral trauma and parkinsonism. The cause-effect relationship between head injury and subsequent movement disorder is not fully appreciated. This may be related partially to the delayed appearance of the movement disorder. Movement disorders after severe head injury have been reported in 13 to 66% of patients. Although movement disorders after mild or moderate head injury are frequently transient and, in general, do not result in additional disability, kinetic tremors and dystonia may be a source of marked disability in survivors of severe head injury. Functional stereotactic surgery provides long-term symptomatic and functional benefits in the majority of patients. Thalamic radiofrequency lesioning, although beneficial in some patients, frequently is associated with side effects such as increased dysarthria or gait disturbance, particularly in patients with kinetic tremor secondary to diffuse axonal injury. Deep brain stimulation is used increasingly as an option in such patients. It remains unclear whether pallidal or thalamic targets are more beneficial for treatment of posttraumatic dystonia. Trauma to the central nervous system is an important causative factor in a variety of movement disorders. The mediation of the effects of trauma and the pathophysiology of the development of posttraumatic movement disorders require further study. Functional stereotactic surgery should be considered in patients with disabling movement disorders refractory to medical treatment.

Holmes' tremor following midbrain Toxoplasma abscess: clinical features and treatment of a case

The label Holmes' tremor defines a rare symptomatic movement disorder frequently occurring with midbrain damage. It appears at rest and worsens adopting a posture and on attempting movements. We describe the case of a patient with Holmes' tremor due to a presumed Toxoplasma abscess of the midbrain. The positive response to a combined therapy with levodopa and isoniazid is also reported.

Rubral tremor after thalamic infarction in childhood

The occurrence of tremor after thalamic lesions is well known. Delayed rubral tremor secondary to bilateral thalamic infarction is a rare finding and has not been reported previously in childhood. We present two children with a combined resting-postural-kinetic tremor caused by bithalamic infarction. The first child was a male 14 months of age, and the second was a male 9 years of age. These children come from unrelated families. On hospital admission of the first patient, generalized seizures and routine electroencephalogram (EEG) findings with diffuse spike-wave discharges predominantly over the left frontal area were clinically observed, leading to the initial diagnosis of epilepsia partialis continua. However, clinical observation and video-EEG monitoring of the movements revealed nonepileptiform accompaniments, favoring the diagnosis of rubral tremor. In the second patient, EEG revealed no paroxysmal activity and was within normal limits for age. In both patients, cranial magnetic resonance imaging revealed ischemic lesions in thalami bilaterally but failed to reveal any mesencephalic lesion. These patients demonstrate that thalamic infarction can cause rubral tremor in childhood.

Phenomenology and treatment of tremor disorders

Tremor is classified according to anatomic distribution among body parts, and by frequency and amplitude during rest, postural maintenance, movement, intention, and the performance of specific tasks. Key historical features include age at onset, progression over time, family history, exacerbating and remitting factors and behaviors, response to alcohol and medications, and additional neurological signs and symptoms. Accurate diagnosis is a critical factor in predicting the natural history and response to treatment.

Posteroventral pallidotomy for midbrain tremor after a pontine hemorrhage. Case report

This 49-year-old man gradually developed a disabling action tremor in the proximal right upper extremity 8 months after suffering a pontine tegmental hemorrhage. The intraoperative microrecording in the nucleus ventralis intermedius (VIM) of the left thalamus revealed tremor-synchronous grouped discharges with a vigorous (2.7 Hz) action tremor predominantly in the shoulder and upper arm. High frequency electrical stimulation in the VIM did not affect the tremor. A posteroventral pallidotomy (PVP) was performed and resulted in the successful alleviation of all tremor activity. Posteroventral pallidotomy is known to alleviate parkinsonian tremors, especially those occurring in the contralateral lower extremity, trunk, and proximal segment of the contralateral upper extremity. The authors consider the pallidoreticular pathway to be an important tremor-mediating pathway for the proximal segment of the upper extremities and believe it can be controlled more effectively by PVP than by VIM thalamotomy, as demonstrated by the PVP-induced resolution of the midbrain tremor observed in this case.

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.

Apomorphine and levodopa challenge in patients with a focal midbrain lesion

Three patients who presented with parkinsonian signs resulting from a focal midbrain lesion are reported. In all patients parkinsonian features occurred acutely and improved following acute challenge with apomorphine but not with levodopa. Remission of parkinsonian signs occurred spontaneously to a different degree. Inconsistent clinical response following administration of levodopa has been well documented in patients with focal midbrain lesions associated with parkinsonian signs; however, the efficacy of apomorphine has not been tested before. Anatomic or etiologic features do not allow us to predict in which cases parkinsonian signs secondary to a midbrain lesion would respond to levodopa or to dopamine agonists. A trial with apomorphine is warranted in all such cases.

Midbrain infarction: a rare presentation of cryptococcal meningitis

A 20-year-old farmer who had headache and fever for 1 month, suddenly developed left hemiplegia, tremor in left arm and titubation followed by deep coma. Cranial CT scan revealed an infarction in right crus of midbrain. His CSF revealed 66 mg/dl protein, 10 lymphocytes/mm3, and 70 mg/dl glucose. CSF was positive for cryptococcal antigen. He improved following i.v. amphotericin 0.5 mg/kg and fluconazole 200 mg daily, continued for 6 and 12 weeks respectively. Infarctions though rare in cryptococcal meningitis should be considered in patients with chronic meningitis with vasculitis.

Pharmacologic treatment of tremor

Tremor is a common neurologic symptom that can also be incapacitating to the patient, so effective therapy is needed. The causes of tremor are heterogeneous. Essential tremor (ET) and the tremor associated with Parkinson's disease (PD) are the most common encountered in clinical practice. Beta-adrenergic blockers and primidone remain the mainstay of treatment for ET, whereas carbidopa/levodopa and anticholinergics are most beneficial in PD. However, the efficacy of various other medications has been studied in ET and PD, and also in patients with tremor resulting from other conditions, with varying results.

Pathology of symptomatic tremors

Symptomatic tremors are labeled in the literature under different names including rubral tremor, midbrain tremor, thalamic tremor, myorhythmia, Holmes' tremor, cerebellar tremor, and goal-directed tremor. The most common tremor is a delayed-onset postural and action tremor with a low frequency of 3 Hz and a proximal distribution. Resting irregular tremor is sometimes present. Mild cerebellar dysmetria is often detected. The lesions are mainly located in the thalamus, the brain stem, and the cerebellum, with secondary interruption and degeneration of various pathways and olivary hypertrophy. The more consistent lesions are found in the cerebello-thalamo-cortical and dentato-rubro-olivary pathways. The role of superimposed dysfunction of the nigrostriatal system may account for the rest component. The role of the basal ganglia in the emergence and control of tremor is poorly understood.

Pharmacologic management of movement disorder after midbrain haemorrhage

Movement disorders following midbrain haemorrhage are infrequently encountered in rehabilitation, and are uncommonly corrected by pharmacologic means. This report describes a 20 year-old male with a prior history of cocaine abuse who presented with a 4 day history of dysarthria and blurred vision following methamphetamine abuse. Physical examination demonstrated hypertension, left facial hemispasm, bilateral upward gaze paresis and ataxic gait. Magnetic resonance imaging/magnetic resonance angiography (MRI/MRA) showed multifocal parenchymal haematomas in the mesencephalic tegmentum, subcortical left front region and right anterior thalamus consistent with cavernous angiomas. The patient was transferred to rehabilitation on hospital day 5. The following day, he developed choreoathetoid movements, dystonia, and aphasia, secondary to an extension of the midbrain haemorrhage. Cogentin was initiated with slight improvement in choreoathetoid movements. The patient began intensive multidisciplinary rehabilitation therapy but after 18 days of therapy, the patient remained totally dependent in activities of daily living (ADLs), transfers, mobility and was unable to communicate in any manner. A trial of Sinemet was initiated, with resultant steady improvement in functional ability over the next month. By discharge, the patient was independent in ADLs and ambulation. By 9 months post discharge follow-up, the patient was fully independent with normal cognition, and had self tapered all medications without ill effect. Dopamine agonist trials of appropriate duration appear indicated in cases of movement disorder (paucity or excess) following midbrain lesions.

Posttraumatic movement disorders after moderate or mild head injury

We examined the occurrence of posttraumatic movement disorders after moderate or mild head injury with a three-level follow-up study including questionnaires, telephone interviews, and personal examinations 4-6 years after the trauma (mean 5.2 years). Sixteen of 158 patients (10.1%) for whom a detailed follow-up was available had developed movement disorders most probably related to craniocerebral trauma. The most frequent finding was a low-amplitude postural/intention tremor that appeared to resemble enhanced physiological or essential tremor. Twelve patients reported transient tremor, two patients had persistent tremor, one patient had transient tremor and persistent hyperekplexia, and another patient had mild persistent cervical myoclonic twitches. Overall, the movement disorder was transient in 12 patients (7.6%) and persisted in only 4 patients (2.6%). These movement disorders were not disabling and did not require medical therapy. Taking into account possible bias by selection of the sample group, the frequency of movement disorders secondary to moderate or mild head trauma might be lower than 10.1%. Posttraumatic movement disorders occurred significantly more often in the group of patients with Glasgow Coma Scores between 9 and 14 than in those with a score of 15. Severe movement disorders such as low-frequency kinetic tremor or hemidystonia were not identified in this survey.

Midbrain tremor and hypertrophic olivary degeneration after pontine hemorrhage

A severe rest tremor arose in a patient's right arm 9 months after a pontine tegmental hemorrhage. Magnetic resonance studies at 4 and 10 months showed residual hemosiderin in the pons and increasing hypertrophic olivary degeneration (HOD) affecting primarily the left olive. The tremor was refractory to pharmacotherapy (clonazepam, propranolol, and levodopa), but was reduced after implantation of a thalamic stimulator device. Although pontine hemorrhage is among several common causes of HOD, it has not previously been appreciated as a cause of midbrain ("rubral") tremor. A disynaptic dentatorubroolivary tract associated with tremor and monosynaptic dentatoolivary tract associated with HOD may both be components of the rubroolivocerebellorubral loop implicated in midbrain tremor. Their proximity makes the combination of tremor and HOD after pontine tegmental damage plausible and even likely.

Activation mapping in essential tremor with functional magnetic resonance imaging

We used functional magnetic resonance imaging (FMRI) to study possible cerebral activation patterns associated with unilateral postural tremor in 12 patients with essential tremor (ET), with mimicked postural tremor in 15 control subjects, and with passive wrist oscillation in both groups. During essential tremor, patients showed mainly contralateral activation of the primary motor and primary sensory areas, the globus pallidus, and the thalamus, but bilateral activation of the nucleus dentatus, the cerebellar hemispheres, and the red nucleus. Only 2 patients presented with activity in the medulla close to the olivary nucleus. Unilateral passive wrist oscillation of ET patients resulted in only unilateral activation of the cerebellum, nuclei dentati, and red nuclei. In contrast to the involuntary tremor condition of ET patients, the mimicked tremor condition of the control subjects was not associated with bilateral activity in the cerebellum, nuclei dentati, or red nuclei. Involuntary tremor of ET patients was associated with a significantly larger extent of activation in the cerebellar hemispheres and the red nucleus (p < 0.003) compared with mimicked tremor in the control group. Our FMRI study indicates that ET is mainly associated with an additional contralateral cerebellar pathway activation and overactivity in the cerebellum, red nucleus, and globus pallidus without significant intrinsic olivary activation.

Resting hand tremor in abstinent cocaine-dependent, alcohol-dependent, and polydrug-dependent patients

Laboratory studies of cocaine-exposed rodents, and positron emission tomographic studies of human cocaine abusers have suggested that chronic cocaine abuse downregulates dopaminergic function in the basal ganglia. The present study sought to provide behavioral evidence for this phenomenon by demonstrating enhanced levels of resting hand tremor among patients with previous histories of cocaine dependence. to determine the specificity of the phenomenon, patients with previous histories of alcohol dependence, cocaine/alcohol codependence, and cocaine/opiate codependence were also evaluated. Patients were assigned to one of four groups according to DSM-IIIR diagnostic criteria: (1) cocaine dependent (n = 19); (2) cocaine and alcohol dependent (n = 12); (3) cocaine and opiate dependent (n = 7); (4) alcohol dependent (n = 9). All were abstinent from their primary drug of abuse for a period of 1 to 5 months. The three patient groups with histories of cocaine dependence exhibited significantly more resting hand tremor than the alcohol-dependent and normal control groups. Furthermore, hand tremor in the former three groups was positively related to the number of self-reported uses of cocaine and negatively related to the number of months of cocaine abstinence.

Rest tremor and extrapyramidal symptoms after midbrain haemorrhage: clinical and 18F-dopa PET evaluation

A 25 year old man had an acute subarachnoid haemorrhage due to the rupture of a right peduncular subthalamic arteriovenous malformation. Seven months later he developed a left rest tremor associated with mild bilateral extrapyramidal symptoms and responsive to levodopa treatment. Surface EMG recording showed synchronous activity of agonist and antagonist muscles in the left limbs. A PET 18F-dopa study showed a large decrease of the Ki value in the right striatum. One year after the stroke a persistent postural component developed in the tremor.

The treatment of posttraumatic tremor by stereotactic surgery. Symptomatic and functional outcome in a series of 35 patients

The authors report the long-term results of stereotactic surgery for severe posttraumatic appendicular tremor in 35 patients. The tremors developed after severe head trauma in 33 patients (94%) and after mild to moderate head trauma in two (6%). In all but one, the tremor was most evident during activity. The amplitude of the kinetic tremor was greater than 5 cm in 33 patients (94%) and greater than 12 cm in 19 patients (54%). All were severely incapacitated in their daily living activities due to the tremors. The 35 patients underwent 42 stereotactic operations; five patients were reoperated on the same side and two were treated with a bilateral staged procedure. The contralateral zona incerta was the stereotactic target in 12 patients and was targeted in combination with the base of the ventrolateral (oroventral) thalamus in 23 patients. Long-term postoperative follow-up review was obtained in 32 patients (mean follow-up period 10.5 years). Persistent improvement of tremor was noted in 88%. The tremor was absent or markedly reduced in 65%. Functional disability was assessed and quantified with a modified form of an established rating scale for patients with tremor; it was reduced from a mean value of 57% of maximum disability to 37% over the long term (p < 0.001). Follow-up lesion assessment was obtained in 18 patients by multiplanar magnetic resonance imaging and at autopsy in one patient whose death was unrelated to surgery. As in previous studies, the frequency of persistent side effects was relatively high (38%). These consisted mainly of aggravation of preoperative symptoms. The results are compared to those of a total of 55 patients reported from 1960 to 1992. The occurrence of dystonia and dystonic postures is discussed. Stereotactic surgery is a powerful tool to alleviate posttraumatic tremor and to improve functional disability. However, as there is considerable risk of persistent morbidity in patients after severe head trauma, the operation should be restricted to selected cases with disabling tremor.

Magnetic resonance imaging of patients with intention tremor

We evaluated the magnetic resonance images of the patients with intention tremor. Five patients out of seven had some atrophic structures or changes in signal intensity in the cerebello-rubral thalamic tract. Moreover, the T2-weighted images of the patients group detected the dentate and red nuclei more poorly than those of our control group. From these results, the etiological significance of the tract was confirmed and the mechanism of the intention tremor onset was discussed.