Unilateral Tremor Research Articles

Tremor-correlated cortical activity in essential tremor

In patients with parkinsonian resting tremor, tremor-correlated activity in the contralateral sensorimotor cortex has been studied by both magnetoencephalography (MEG) and electroencephalography (EEG). In essential tremor, MEG failed to detect cortical involvement. The objective of this study was to investigate whether EEG recording can reveal tremor-correlated cortical activity in patients with essential tremor or enhanced physiological tremor. Seven patients with essential tremor and three patients with enhanced physiological tremor participated in the study. Unilateral postural tremor was activated by wrist extension on the right or on the left side. Electromyography (EMG) signals arising from the wrist extensor and flexor muscles, and a high-resolution EEG were recorded simultaneously. Coherences between the time series of the rectified tremor EMG and the EEG were estimated. In five of nine arms with essential tremor, we found highly significant coherences at the tremor frequency between the tremor EMG and the EEG. Isocoherence maps illustrating the topography of significant coherences over the scalp showed that the maximum coherences were located over the contralateral sensorimotor cortex. In the patients with enhanced physiological tremor, we were unable to detect consistent significant corticomuscular coherences at the tremor frequency. Using simultaneous EEG-EMG recordings, we showed that significant corticomuscular coherences at the tremor frequency can be found in essential tremor. This finding contrasts with a recent study based on MEG recordings. The results suggest that the sensorimotor cortex is involved in the generation of essential tremor, in a similar way to that previously shown in parkinsonian resting tremor.

Essential tremor: an overdiagnosed condition?

The diagnosis of essential tremor (ET) and its differentiation from other types of tremor is often difficult. In 1994 Bain et al. defined a classical phenotype by studying 20 patients with pure essential tremor and similarly affected family members in at least three generations. We assessed how many of the patients diagnosed by different neurologists at our institution as having ET conformed to this defined phenotype. We randomly selected 50 patients who were diagnosed with ET by any neurologist at the National Hospital for Neurology and Neurosurgery since the publication of the Bain et al. report, and determined the number of patients who had clinical features compatible with the phenotype that it had defined. Only 25 (50%) of these patients had ET so defined. Ten patients clearly had alternative diagnoses: four had clear additional dystonia, two neuropathic tremor, two had unilateral leg tremor, one drug-induced tremor, and one sudden onset after head trauma. The remaining 15 patients also had atypical features including myoclonus (one), onset in a body part other than the arms (six), sudden onset (two), rest tremor (seven), onset after the age of 65 years (four), a family member with an isolated head tremor (one), or reduced armswing (two). The diagnosis of ET is overused even among experienced neurologists, and other types of tremor should be considered in atypical patients before making this diagnosis.

Progressive myoclonic ataxia associated with celiac disease presenting as unilateral cortical tremor and dystonia

Progressive myoclonic ataxia associated with celiac disease presenting as unilateral cortical tremor and dystonia

Subthalamic Prelemniscal Radiation Stimulation for the Treatment of Parkinson's Disease: Electrophysiological Characterization of the Area

BackgroundPrevious reports have provided evidence of a reticulo-thalamic system, extending from the mesencephalic reticular formation (MRF) to the ventrolateral thalamus (VL), involved in the production of tremor. In humans, a funnel of fibers in the posterior subthalamus named the prelemniscal radiations (Raprl) has been described as an exquisite target to treat tremor in cases of Parkinson's disease. MethodsIn the present study, a group of 14 patients suffering from Parkinson's disease, with prominent unilateral tremor and rigidity, were implanted with tetrapolar depth brain stimulation (DBS) electrodes in Raprl to perform chronic electrical stimulation (ES) for the treatment of patient symptoms. Electrodes were left externalized to corroborate their placement throughout MRI studies and also to perform the following electrophysiological battery: (a) recording of somatosensory-evoked responses (SEP) through different electrode contacts and scalp by means of a paradigm to study the attention process; (b) evoking scalp EEG responses by stimulation with low (3 cps, 6 cps) and high (60–120 cps) frequencies with stimuli delivered through different electrode contacts, and (c) studying recovery cycle (RC) potentials in the Raprl while the upper MRF was being stimulated and, conversely, the RC in MRF while Raprl was being stimulated, before and after subacute Raprl stimulation. Thereafter, the electrodes were internalized and connected to a pulse generator (IPG) to carry on chronic ES, while the effects of stimulation were determined through a quantitative evaluation that measured phasic and tonic muscular activity with EMG recordings during different motor tasks. ResultsResults indicate the following: (a) that late, but not early, SEP components were recorded in Raprl and modulated in different attentive conditions; (b) that bilateral recruiting responses and spike and wave complexes were elicited by Raprl through low-frequency stimulation, while bilateral positive DC shifts induced by high-frequency stimulation were recorded, similar to those obtained in animals from MRF, and (c) that Raprl-ES induced RC inhibition at Raprl, but Raprl ES did not change MRF-RC. Long-term Raprl-ES induced a significant decrease in tremor and rigidity. ConclusionsIt was concluded that Raprl represents a subthalamic circuit electrophysiologically related to MRF in the genesis of tremor and rigidity and in the process of selective attention. Raprl-ES induced a significant improvement in tremor and rigidity by causing inhibition of the stimulated area.

Tremor-correlated cortical activity detected by electroencephalography

Objective: In this study we investigated whether cortical activity related to Parkinsonian resting tremor can be detected by electroencephalography (EEG).Methods: Seven patients with idiopathic Parkinson's disease suffering from unilateral tremor participated in the study. Electromyography (EMG) signals arising from the wrist extensor and flexor muscles as well as a high resolution EEG were recorded simultaneously. Coherencies between EEG and EMG were calculated.Results: In all patients, we found highly significant coherencies at the tremor frequency or its first harmonic between the tremor EMG and contralateral EEG channels. There were no significant coherencies between the tremor EMG and ipsilateral EEG channels. Isocoherency maps illustrating the topography of the coherencies over the scalp showed that the maximum coherencies were situated over the cortical motor areas. In one case, a high coherency was also found over the parietal cortex.Conclusions: The results show for the first time that tremor-correlated cortical activity can be detected by electroencephalography. The findings underline that motor areas of the cerebral cortex are involved in the neuronal network generating resting tremor in Parkinson's disease.

Cerebral arteriovenous malformations and movement disorders

A series of six patients with movement disorders associated with cerebral arteriovenous malformations (AVM) is reported. The AVMs were classified according to the Spetzler–Martin classification as grade V (one patient), grade IV (four patients), and as grade III (one patient). One patient had action-induced hemidystonia caused by a contralateral frontoparietal AVM which compressed the putamen and was supplied partially by enlarged lenticulostriate arteries. Two patients presented with unilateral cortical tremor associated with contralateral high-frontal cortical/subcortical AVMs sparing the basal ganglia. Another patient developed hemidystonia and hemichorea-hemiballism after bleeding of a contralateral temporooccipital AVM and subsequent ischemia. Two patients had focal dystonia after thalamic and basal ganglia hemorrhage from AVMs. Five patients were operated on. The movement disorder was abolished in one patient postoperatively. Different mechanisms were identified that are relevant for the development of AVM-related movement disorders: mass effect, diaschisis, local parenchymal altered cerebral blood flow, and hemorrhagic or ischemic structural lesions.

Involuntary movements and abnormal spontaneous EMG activity in syringomyelia and syringobulbia.

To describe different types of involuntary movements and abnormal spontaneous electromyographic (EMG) activity in patients with syringomyelia. A comprehensive study on involuntary movements in patients with syringomyelia has not yet been undertaken, to these authors' knowledge. One hundred adult patients with syringomyelia were examined over the last 15 years. Involuntary movements were videotaped and evaluated by two independent observers. Electromyographic recordings were made using bipolar surface electrodes. The H-reflex recovery curve was obtained after stimulation of the median nerve at the elbow and recording from the flexor carpi radialis. Involuntary movements or abnormal postures were observed in 22 patients. Three patients showed segmental spinal myoclonus, nine minipolymyoclonus, and four propriospinal myoclonus. Five patients had unilateral or bilateral hand postural tremor (8-10 Hz). Focal or segmental dystonia was observed in three patients. Electromyography showed spontaneous bursts of grouped action potentials synchronous in muscles innervated by the same spinal segment, synchronous firing of neurogenic motor unit potentials, or continuous motor unit activity. Increased H-reflex responses to conditioning stimuli were found in patients with spinal myoclonus. Long latency responses were obtained during peripheral nerve stimulation in four patients. Four patients had rigidity and abnormal upper limb posture. Respiratory synkinesis was observed in three patients. One patient developed inverse masticatory muscle activity. Patients with syringomyelia showed a wide spectrum of involuntary movements. An increased excitability of spinal motor neurons was probably the basic underlying mechanism.

Delayed Unilateral Post-Traumatic Tremor: Localization Studies Using Single-Proton Computed Tomographic and Magnetic Resonance Spectroscopy Techniques

We present the case of a 46-year-old former U.S. Marine who developed unilateral dystonic tremor responsive to anticholinergic medications 13 years after contralateral, combat-induced head trauma. Although conventional neuroimaging techniques showed normal brain anatomy, single-proton computed tomographic scans demonstrated hypometabolism ipsilateral to the area of old trauma. Proton echoplanar spectral imaging demonstrated decreased signal in this same area on creatine imaging, which normalized on anticholinergic medication. Choline imaging on medication showed a signal void in the clinically suspected basal ganglia-thalamus region. We believe that these results indirectly suggest a trans-synaptic origin of the patient's movement disorder.

High-frequency stimulation of the subthalamic nucleus suppresses experimental resting tremor in the monkey

The effect of high-frequency stimulation of the subthalamic nucleus on parkinsonian-like resting tremor was investigated in two monkeys ( Macaca fascicularis). Unilateral tremor of the arm and leg was induced by electrical coagulation of the brainstem area including the substantia nigra and the red nucleus. The tremor was only seen at rest condition with a very stable frequency of 4.46±0.59 Hz (mean±S.D.). Apomorphine (0.1–0.4 mg/kg, s.c.) completely blocked the tremor, suggesting that it was a dopaminergic-dependent symptom just like the parkinsonian tremor. When the stimulating frequency varied from 20 to 1 000 Hz, both mono- and bipolar stimulation (square pulses, 0–5 mA, 0.06 ms) of the subthalamic nucleus suppressed resting tremor in a frequency-dependent manner but monopolar stimulation was more effective. These effects remained stable for more than two years. The present results suggest that the subthalamic nucleus is involved in the control and mechanism of resting tremor and that the high-frequency stimulation of the subthalamic nucleus can be used as an alternative therapy in parkinsonian patients with akinesia, rigidity and resting tremor.

Ablative Therapy for Movement Disorders: Does Thalamotomy Alter the Course of Parkinson’s Disease?

Although there is no confirmed evidence that therapy alters the course of Parkinson's disease, some follow-up of patients who have undergone thalamotomy has suggested it might slow or even halt the progress of the disease. A retrospective semiquantitative assessment of 55 patients undergoing bilateral thalamotomy and 31 undergoing unilateral operation confirms the previously held notion that postencephalitic disease or clinical onset below age 40 may progress so slowly as to appear arrested after thalamotomy. Patients left with no tremor and minimal rigidity after completion of unilateral or bilateral surgery, whether their disease is of youthful onset, postencephalitic or not, may also appear to follow stable courses postoperatively. This occurs in patients whose tremor and rigidity have been controlled by bilateral thalamotomy and also in those in whom unilateral tremor and rigidity have been controlled by unilateral surgery in the absence of significant tremor and rigidity on the other side of the body. Possible explanations are discussed.

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.

Inclusion body myositis associated with a severe unilateral levodopa-responsive upper extremity tremor

Inclusion body myositis associated with a severe unilateral levodopa-responsive upper extremity tremor

Writing tremor after discrete cortical infarction.

Hand tremor is a rare manifestation of stroke, and writing tremor has not been reported to be produced by stroke. We describe a patient who developed a unilateral hand tremor mimicking primary writing tremor after discrete cerebral cortical infarction. A 67-year-old man developed mild right hemiparesis. Brain magnetic resonance imaging showed a discrete cortical infarct in the left frontal area. After recovery of motor power, the patient showed significant right hand tremor exclusively during writing or similar motor activities including tooth brushing or shaving. The tremor was temporarily alleviated by clonazepam but persisted until 7 months of follow-up. Medical history suggested that the patient had mild essential tremor, but he did not experience tremor on writing before the onset of stroke. This observation suggests that unilateral hand tremor mimicking primary writing tremor may be produced by cortical infarction. It remains unclear whether the patient's previous essential tremor played an additional role in the development of this symptom.

CT-Oriented Microrecording Guided Selective Thalamotomy

A further trial of CT-oriented microrecording guided stereotactic selective thalamotomy was conducted at the Centro Internacional de Restauración Neurológica, Havana City as treatment of resting tremor in 11 patients with idiopathic Parkinson's disease (PD), and in 3 other patients with intentional tremor associated with multisystemic atrophy and cerebral palsy. Three of the parkinsonian patients had undergone fetal mesencephalic tissue transplantation with significant improvement of the most debilitating symptoms of PD and stabilization of the motor state, but predominantly unilateral tremor had impaired them progressively despite increased levodopa doses. A Leksell frame was used with a novel surgical planning system and electrophysiological recordings to identify the optimal target point inside the ventralis intermedius. In all but 1 case, the tremor was totally arrested. No persistent complications were observed.

Blinded evaluation confirms long-term asymmetric effect of unilateral thalamotomy or subthalamotomy on tremor in Parkinson's disease.

In the past, stereotactic surgery was a regular treatment for prominent unilateral tremor in Parkinson's disease (PD), but follow-up studies were usually short-term and always unblinded. We examined 17 PD patients in long-term follow-up (mean, 10.9 years after surgery) and used videotapes and the Unified Parkinson's Disease Rating Scale to blindly compare tremor ipsilateral and contralateral to the side of surgery. Since the patients were specifically selected for stereotactic surgery because of asymmetric tremor, and the surgical side chosen was contralateral to the predominant tremor, a sign of long-term efficacy would be current postoperative reversal of tremor side predominance. Upper extremity tremor was significantly better contralateral to the surgery compared with the ipsilateral side. We conclude that stereotactic surgery improved the absolute magnitude of tremor or ameliorated its rate of progression. Since asymmetric bradykinesia and dyskinesia were not a prerequisite for the choice of surgical side, we cannot make any conclusion about long-term impact of surgery on these features.

Hemiparkinsonism‐hemiatrophy syndrome

We evaluated 11 patients with hemiparkinson-hemiatrophy syndrome, 6 with body and contralateral cerebral hemispheric hemiatrophy, 4 with only body hemiatrophy, and 1 with just brain hemiatrophy. The mean age of symptom onset was 38.1 years (range, 18 to 54) with 5.2 +/- 3.1 (mean +/- SD) years of illness until the last follow-up visit. The presenting symptom was unilateral tremor in 6 patients, hand dystonia in 2, bradykinesia in 2, and abnormal gait in 1 patient. Three patients had a good response to levodopa, 4 had moderate response, and 2 patients had a poor response. During a mean follow-up period of 1.7 years (range, 4 months to 5 years), the Hoehn and Yahr score changed in only 3 patients: 2 gained 1.5 points and 1 gained 3 points over 2.5 years. We discuss the association between hemiparkinsonism-body hemiatrophy and contralateral hemispheric hemiatrophy, and raise the possibility of early childhood brain insult with delayed-onset parkinsonism.

Preliminary report: activation of the cerebellum in essential tremor

Several images of cerebral blood flow were recorded during inhalation of carbon-15-labelled carbon dioxide by positron emission tomography in four patients with essential tremor and four normal controls. Unilateral involuntary postural tremor in essential tremor patients was associated with blood flow significantly greater than that at rest in the contralateral sensorimotor cortex, both lateral premotor regions, and both cerebellar hemispheres. Of these regions, only the cerebellum was not activated in normal controls holding a posture without tremor or in essential tremor patients undergoing passive wrist movement. The increased flow in the cerebellum therefore seems to represent neural activity involved in tremor generation. It is proposed that essential tremor is due to oscillation within cerebello-olivary pathways, relayed by way of the thalamus and motor cortex to the spinal cord.

The role of the left and right thalamus in language asymmetry: Dichotic listening in Parkinson patients undergoing stereotactic thalamotomy

Fourteen patients with Parkinson's disease (rigidity and unilateral tremor as main symptoms) were treated with stereotactic thalamotomy. The operation was performed in either the left or right ventrolateral thalamus, depending on which hand (or foot) was most affected with tremor. Nine patients were operated on the left side and four on the right side. All patients were tested for asymmetry of language functioning with dichotic presentations of consonant-vowel (CV) syllables. The patients had to indicate which of the two syllables he/she heard on each trial. Dichotic listening was performed before and after the operation, as well as during electrical stimulation of the VL nucleus just before the lesion was carried out. The results revealed essentially three things: an overall reduced right ear advantage (REA) in the patient group compared to what is known from studies of healthy individuals; an increase in REA during left-sided stimulations; and a marked reduction in REA after left-sided lesions. It is concluded that the present data support the notion put forward by Ojemann (e.g., 1975) of a lateralized activating gating mechanism in the left VL nucleus that gates access for language information to the appropriate cortical areas. The gating mechanism seems to be activated by stimulation, and deactivated after lesions. Dichotic listening may thus be a heuristic instrument in assessment of language functions in Parkinson patients.

Voluntary vs autonomous control of repetitive finger tapping in a patient with Parkinson's disease

Fourier analysis was used to investigate the role of perceptual information in controlling repetitive finger tapping in a patient with unilateral Parkinsonian tremor. The results are interpreted in the context of Von Holst's theory of relative co-ordination, and demonstrate the subject's reliance on extrinsic information to counteract tremor when performing voluntary repetitive movement.

Stability and tremor in the fingers associated with cerebellar hemisphere and cerebellar tract lesions in man.

Stability and tremor in the fingers were assessed by a new technique in patients with unilateral cerebellar syndromes. In 11 patients with unilateral cerebellar hemisphere lesions tremor was observed with either clear tremor at 5-7 Hz or prolongation of the tremor profile out to 11 Hz. In 10 patients with unilateral cerebellar lesions associated with ipsilateral past-pointing there was an asymmetry in finger stability. Compared with normal subjects there was a significant decrease in stability contralateral to the lesion, while the ipsilateral side's stability was not different from normal. In patients with high brain stem lesions at the level of cranial nerves VII and above, tremor had frequencies of 5-7 Hz. In those with lower brain stem lesions, often with long tract signs as well, the frequencies of tremor were faster, 8-11 Hz, which may reflect damage to cerebellar inflow tracts. A broad if not specific correlation was found between clinical condition, site of lesion and finger stability and tremor.