Cortical myoclonus in huntington's disease associated with an enlarged somatosensory evoked potential

Caviness, John N.; Kurth, Mathias

doi:10.1002/mds.870120633

Cited by 25 publications

(7 citation statements)

References 22 publications

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“…Thus, there is a significant possibility that the mechanism of myoclonus in PD is quite different from the much more frequently encountered cortical reflex myoclonus physiology. Indeed, this group of electrophysiological findings distinguishes the myoclonus in PD from the myoclonus seen in multiple‐system atrophy, corticobasal degeneration, reported cases of Alzheimer's disease, minipolymyoclonus, and cortical tremor 3, 4, 13, 17–19. If we had tested for long‐latency EMG responses during activation, perhaps a small abnormality would have been detectable.…”

Section: Discussionmentioning

confidence: 94%

“…It is remarkable that not a single patient had evidence of exaggerated reflex features, as shown by the lack of reflex myoclonus on clinical examination, the finding that cortical SEP waves were not enlarged, and the absence of long‐latency reflexes at rest. This collection of electrophysiological characteristics is unusual, as most instances of positive–negative EEG transients detected on back‐averaging of myoclonus are described as cortical reflex myoclonus, which is associated with clinical reflex myoclonus, an enlarged cortical SEP wave, and long‐latency EMG responses at rest consistent with a transcortical conduction time 13. It may be argued that this apparent absence of reflex myoclonus is simply due to the insufficient sensitivity of our current methods to detect very mild reflex cortical hyperexcitability in our 20 patients.…”

Section: Discussionmentioning

confidence: 97%

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Small‐Amplitude cortical myoclonus in Parkinson's disease: Physiology and clinical observations

et al. 2002

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We studied the occurrence of small-amplitude myo- clonus in 20 idiopathic Parkinson's disease patients who had no evidence of dementia as defined by criteria in the Diagnostic and Statistical Manual of Mental Disorders, fourth edition. Parkinson's disease was diagnosed by United Kingdom Brain Bank criteria, and clinical assessment was performed with the Unified Parkinson's Disease Rating Scale motor score, Hoehn and Yahr staging, and the Mini-Mental State Examination. Clinical assessment showed a range of mild-to-moderate disease severity. All patients underwent polygraphic electro-encephalographic-electromyographic (EMG) recording with back-averaging, somatosensory evoked potential testing, and attempted elicitation of long-latency EMG responses. Multichannel surface EMG recording during muscle activation showed irregular, multifocal, brief (<50 msec) myoclonus EMG discharges. Back-averaging consistently showed a focal, short-latency, electroencephalographic transient prior to the myoclonus EMG discharge. Cortical somatosensory evoked potential waves were not enlarged, and long-latency EMG responses at rest were not present. The small-amplitude myoclonus in such cases arises from an abnormal discharge from the sensorimotor cortex. The mechanism of this cortical myoclonus in Parkinson's disease has differences from the more common "cortical reflex myoclonus" physiology. Advanced parkinsonism is not a requirement for manifestation of this myoclonus type. Although the myoclonus occurred without dementia in these cases, its relationship to the subsequent development of cognitive impairment remains to be defined.

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Section: Discussionmentioning

confidence: 94%

Section: Discussionmentioning

confidence: 97%

Small‐Amplitude cortical myoclonus in Parkinson's disease: Physiology and clinical observations

et al. 2002

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“…[22][23][24][25] An enlarged SSEP has been reported by one group of investigators 25 but not others. MN-SSEPs and posterior tibial nerve (PTN)-SSEPs are often abnormal in Huntington's chorea.…”

Section: Huntington's Choreamentioning

confidence: 84%

Somatosensory Evoked Potentials in Pediatrics—Abnormal

Gilmore¹

2006

Clinical Neurophysiology of Infancy, Childhood, and Adolescence

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SSEPs are useful in evaluating children in coma. In a series of 43 children in coma from head trauma or hypoxic-ischemic encephalopathy in which all children had Abnormal Evoked Potentials 25 Somatosensory Evoked Potentials in Pediatrics-Abnormal ROBIN L. GILMOREFIGURE 25-1 Comparison of the median nerve evoked short latency (bottom two traces) and longer latency (top traces) potentials in a normal child and a child with degenerative disease. In the bottom two traces the analysis time is 20 milliseconds. In the normal child, three short-latency positive potentials are recorded in the Cz′-hand reference lead (arrowheads). In the Cz′-ear lead only the second two potentials are seen (arrowheads). In the patient, only the first two positive potentials are recorded in the Cz′-hand reference lead (arrowheads). Only the second positive potential is seen in the Cz′-ear lead (arrow). The analysis time in the top traces is 200 milliseconds. In the normal child the Cz′-ear lead yields prominent longer latency potentials. No response is recorded in the patient. (From Cracco JB, Bosch VV, Cracco RQ: Cerebral and spinal somatosensory evoked potentials in children with CNS degenerative disease. Electroencephalogr Clin Neurophysiol 1980;49:437-445.) C4 C4 -Shoulder C4 C4 -Ear Spine -Cz Cz ' ' ' FIGURE 25-12 Median nerve somatosensory evoked potentials in a 7-year-old girl with severe injury to the brachial plexus at birth. Note that this child has no avulsion, the dorsal root ganglion is intact, and a sensory potential is recorded over Erb's point. Only a P9 is recorded in the C4′-shoulder lead and a barely detectable N9 in the C7 spine-Cz′ lead. Potentials are absent in the C4′-ear lead. (From Cracco JB, Bosch VV, Cracco RQ: Cerebral and spinal somatosensory evoked potentials in children with CNS degenerative disease. Electroencephalogr Clin Neurophysiol 1980;49: 437-445.) Cz' FIGURE 25-13 Posterior tibial nerve somatosensory evoked potentials from a young child with Guillain-Barré syndrome. The time base and polarity are identical to those of Figure 25-8. No potential rostral to the peripheral N5 is identified.

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“…However, the absence of jerk-locked EEG abnormalities does not completely exclude a direct cortical involvement in the origin of myoclonic discharges [39,40,60]. A cortical origin has been proposed for the myoclonus occurring in patients with corticobasal degeneration [6,9,60], Huntington's disease [8,59], or the cerebellar-type multiple system atrophy [39,44]. The presence in many of our patients of an abnormally reduced inhibition of brainstem reflexes does not permit to exclude hyperexcitability of brainstem reticular formation as a possible source of myoclonic jerks.…”

Section: Discussionmentioning

confidence: 99%

Sensorimotor integration in patients with parkinsonian type multisystem atrophy

et al. 2005

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Sensorimotor integration is an essential feature of the central nervous system that contributes to the accurate performance of motor tasks. Some patients with multiple system atrophy with parkinsonian features (MSAp) exhibit clinical signs compatible with an abnormal central nervous system excitability to somatosensory inputs, such as action myoclonus or enhanced cutaneo-muscular reflexes. To investigate further the site where such dysfunction in sensorimotor integration takes place, we examined the inhibitory effects of a cutaneous afferent volley at two different levels of the motor system in 10 MSAp patients and in 10 age-matched healthy volunteers. Electrical digital nerve stimuli were given as the conditioning stimulus for the motor evoked potentials (MEP) elicited by transcranial magnetic stimulation in hand muscles, and for the blink reflex responses obtained in the orbicularis oculi muscles by supraorbital nerve stimulation. Intervals for the conditioning were 20 to 50 ms for the MEP and 90 to 110 ms for the blink reflex. The MEP was significantly inhibited in test trials in healthy volunteers, reaching a mean of 32% of the baseline values at the ISI of 35 ms. Significant inhibition occurred also in the blink reflex, in which the R2 response was a mean of 12% of baseline values at the ISI of 100 ms. The inhibitory effects were abnormally reduced in 8 patients on the MEP, and in 7 patients on the blink reflex. There were significant group differences between patients and control subjects in the size of the conditioned MEP and blink reflex. These results suggest that sensorimotor integration is abnormal in patients with MSAp in at least two central nervous system sites: the sensorimotor cortex, and the brainstem reticular formation.

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Cortical myoclonus in huntington's disease associated with an enlarged somatosensory evoked potential

Cited by 25 publications

References 22 publications

Small‐Amplitude cortical myoclonus in Parkinson's disease: Physiology and clinical observations

Small‐Amplitude cortical myoclonus in Parkinson's disease: Physiology and clinical observations

Somatosensory Evoked Potentials in Pediatrics—Abnormal

Sensorimotor integration in patients with parkinsonian type multisystem atrophy

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