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Showing papers by "Mark Hallett published in 1989"


Journal ArticleDOI
TL;DR: Benefit was seen in 16 patients, lasted between 1 and 6 months, and was reproducible, and subjective improvement of cramping, pain and/or tension was associated with temporary weakness in injected muscles.
Abstract: The effects of botulinum toxin injections have been studied on 19 patients with hand dystonia. The dystonic muscles were identified by clinical examination and EMG findings of localised bursts of muscle activation with fine wire electrodes during the tasks that precipitated the dystonia. Injections into the most active muscles were given to each patient every 2 weeks in increasing doses (up to 20 U the first week, up to 40 U the second week, and up to 80 U the third week) until performance improvement was achieved. Subjective improvement of cramping, pain and/or tension was associated with temporary weakness in injected muscles. Benefit was seen in 16 patients, lasted between 1 and 6 months, and was reproducible.

163 citations


Journal ArticleDOI
TL;DR: This test is the first to demonstrate physiologic disturbance in patients with hand cramps, and both groups showed less inhibition than the control group, but the abnormality was greater in the dystonic cramp group.
Abstract: We studied inhibition of median nerve H-reflex produced by radial nerve stimulation in both arms of 14 patients with hand cramps and 15 normal volunteers. Median nerve stimulation was delivered 1 and 0.5 msec before and 0, 0.5, 1, 2, 10, 20, 30, 50, 75, 100, 200, 500, and 1,000 msec after radial nerve stimulation. Recordings were from surface electrodes positioned over flexor carpi radialis. We identified three periods of attenuation of median nerve H-reflex amplitude in the control group. When radial nerve conditioning stimuli were delivered simultaneously, 10 and 75 msec before median nerve test stimuli, H-reflex amplitude diminished to 47%, 61%, and 69%. In the patient group we also found three periods of attenuation at the same delays, but the amount of attenuation was significantly less than in controls. Dividing the patients into two groups, dystonic hand cramp and simple hand cramp, both showed less inhibition than the control group, but the abnormality was greater in the dystonic cramp group. This test is the first to demonstrate physiologic disturbance in patients with hand cramps.

126 citations


Journal ArticleDOI
TL;DR: The recruitment curves for H reflexes and M responses were studied in 10 healthy subjects and the durations of the electrical stimulus used ranged from 0.1 to 3 msec, and the amplitude of the H reflex and the relation between the H Reflex and M response changed with stimulus duration.
Abstract: Authorities advocate different stimulus durations to produce an H reflex. In order to find the optimal stimulus duration for recording H reflexes, the recruitment curves for H reflexes and M responses were studied in 10 healthy subjects. The H reflex was recorded in the upper and lower extremities, and the durations of the electrical stimulus used ranged from 0.1 to 3 msec. The amplitude of the H reflex and the relation between the H reflex and M response changed with stimulus duration. H reflexes are brought out to advantage using a stimulus duration between 0.5 and 1 msec.

97 citations


Journal ArticleDOI
TL;DR: The Nyquist distances for interelectrode spacing necessary to record accurately the geographically small components of the SEP in the region of the sensory strip are determined.

88 citations


Journal ArticleDOI
TL;DR: It is demonstrated that active movement gates sensory input, while sustained tonic muscular activity with an opposing constant load does not, and that different somesthetic inputs may be processed differently during movement.

79 citations


Journal ArticleDOI
28 Jul 1989-JAMA
TL;DR: Examination showed decreased visual acuity and pale discs on funduscopic evaluation, and magnetic stimulation of the motor areas of the brain showed delayed motor evoked potentials in abductor pollicis.
Abstract: SELECTED CASE A 34-YEAR-OLD woman was well until age 22 years, when she experienced transient numbness of both hands. At age 24 years she had her first bout of urinary incontinence, a problem that continued intermittently. At age 26 years she experienced double and "faded" vision. Subsequently, she noted the gradual development of weakness and stiffness of both legs, making walking difficult. Examination showed decreased visual acuity and pale discs on funduscopic evaluation. Tone was moderately increased in the legs, but there was only minimal weakness in distal flexors. Sensation was minimally impaired distally in the legs. Reflexes were brisk and there were bilateral Babinski's responses. Visual evoked potentials were increased in latency, right side more than left. Brain-stem auditory evoked potentials from the right ear were abnormal. Somatosensory evoked potentials were normal. Magnetic stimulation of the motor areas of the brain showed delayed motor evoked potentials in abductor pollicis

61 citations


Journal ArticleDOI
TL;DR: The results indicate that patients with SD have increased excitability of blink reflexes, which suggests that the dystonia involves not only the larynx but also other anatomical structures.
Abstract: We studied 12 patients with spasmodic dysphonia (SD) and 12 healthy control subjects. The patients, who had no symptomatic involvement of the eyes, were evaluated for increased excitability of blink reflexes, which is characteristic of blepharospasm and generalized dystonia. We measured symptom severity from sound spectrograms of five sentences, including sentence production time, number of pitch phonatory breaks, and percentage of aperiodic phonation. We evoked blink reflexes by electrical and mechanical stimulation, and assessed excitability by obtaining excitability recovery curves and responses to trains of stimuli. Patients and controls differed from each other in test R2 amplitude attenuation across all intervals from 150 to 1,000 msec to electrical and mechanical stimulation. Our results indicate that patients with SD have increased excitability of blink reflexes, which suggests that the dystonia involves not only the larynx but also other anatomical structures.

50 citations


Journal ArticleDOI

43 citations


Journal ArticleDOI
TL;DR: Two brothers with neuroacanthocytosis had [18F]-2-fluoro-2-deoxyglucose PET scans showing marked glucose hypometabolism of the caudate and putamen, and MRIs showed no evidence of atrophy or modification of signal intensity in these structures.
Abstract: Two brothers with neuroacanthocytosis had [18F]-2-fluoro-2-deoxyglucose PET scans showing marked glucose hypometabolism of the caudate and putamen. MRIs showed no evidence of atrophy or modification of signal intensity in these structures. Decreased glucose utilization of the striatum can underlie hyperkinetic movement disorders of various etiologies.

41 citations


Journal ArticleDOI
TL;DR: The yield of abnormal findings was greatest from measuring absolute motor conduction velocity across the elbow as opposed to comparing the difference in velocities between the elbow and either adjacent segment.
Abstract: Routine evaluation of patients for suspected ulnar neuropathy includes testing of motor conduction velocity across the elbow, although the best position of the elbow for this test is controversial. The preferred testing position--elbow flexion or extension--was studied by determining the yield of abnormality at both positions in patients selected for possible ulnar nerve abnormalities unrelated to motor conduction. We found no major differences between the flexed or extended position of the elbow except that normal values for each of these positions varied. The yield of abnormal findings was greatest from measuring absolute motor conduction velocity across the elbow as opposed to comparing the difference in velocities between the elbow and either adjacent segment.

36 citations


Journal ArticleDOI
TL;DR: Patients with progressive dystonia with diurnal variation with variable effectiveness in PDDV may reflect reduced number or function of biopterin-metabolizing neurons or variable entry of BH4 into these neurons.
Abstract: We administered tetrahydrobiopterin (BH4) to 4 patients with progressive dystonia with diurnal variation (PDDV) One patient improved clinically Deficient CSF concentrations of HVA and 5-HIAA were unchanged despite marked elevation of CSF biopterin concentration Variable effectiveness of BH4 in PDDV may reflect reduced number or function of biopterin-metabolizing neurons or variable entry of BH4 into these neurons

Journal ArticleDOI
TL;DR: The efficacy of botulinum toxin in hemifacial spasm appears to be related to the production of muscle weakness; there is no demonstrable effect on phenomena believed to be ectopic excitation or ephaptic transmission in the facial nerve.
Abstract: Three patients with idiopathic hemifacial spasm were studied clinically and electrophysiologically before and after injections of botulinum toxin into the involved periocular and facial muscles. The spasms were improved for approximately 3 months, and the effect was repeatable on reinjection. The spasms diminished only as long as the muscles were clinically weak, and spasms were observed electromyographically even though therapy eliminated the clinical spasms. Uninjected muscles continued to have spasms. Transmission of excitation from the zygomatic branch to the marginal mandibular branch of the facial nerve and vice versa in all patients was unaltered after therapy, but the amplitude of the response was decreased. The efficacy of botulinum toxin in hemifacial spasm appears to be related to the production of muscle weakness; there is no demonstrable effect on phenomena believed to be ectopic excitation or ephaptic transmission in the facial nerve.

Journal ArticleDOI
TL;DR: Up to 29 channels of somatosensory evoked potentials (SEPs) were recorded in 10 normal volunteers following unilateral femoral nerve (FN) and tibial nerve (TN) electrical stimulation and no correlation was found between the peak latency of P26 and body height.

Journal ArticleDOI
TL;DR: The pathophysiology of the hemiballismus in this case may be loss of tonic inhibition of the lateral globus pallidus from the putamen, leading in turn to greater inhibited of the subthalamic nucleus, less excitation of the medial globus Pallidus, and less inhibition ofThe thalamus and motor cortex, and thus allowing expression of the ballistic movements.
Abstract: A 64-year-old man had right-sided persistent hemiballismus. Cerebral computed tomography (CT) and 0.5-T magnetic resonance imaging (MRI) showed no abnormalities, but 1.5-T MRI showed decreased signal intensity of the putamina, greater on the left than on the right. The subthalamic area was normal on CT and MRI. Positron emission tomography with 18fluoro2-deoxyglucose showed marked hypometabolism of the left putamen (60% of the right) and hypermetabolism of the left parietal lobe (138% of the right). The decreased metabolism of the left putamen may indicate a reduction in neuronal firing. The pathophysiology of the hemiballismus in this case may be loss of tonic inhibition of the lateral globus pallidus from the putamen, leading in turn to greater inhibition of the subthalamic nucleus, less excitation of the medial globus pallidus, and less inhibition of the thalamus and motor cortex, and thus allowing expression of the ballistic movements.

Journal ArticleDOI
TL;DR: This finding offers direct physiologic evidence in humans of monosynaptic excitation from group la afferents to nonhomonymous muscles, a phenomenon for which only limited indirect evidence existed previously.
Abstract: In 6 healthy volunteers, stimulation of the median nerve at the elbow elicited H-reflexes in muscles innervated by the ulnar nerve (flexor digitorum profundus of the 4th and 5th digits of the hand) as well as the median nerve (flexor carpi radialis). This finding offers direct physiologic evidence in humans of monosynaptic excitation from group Ia afferents to nonhomonymous muscles, a phenomenon for which only limited indirect evidence existed previously.