1/19. Giant visually-evoked potentials without myoclonus in the Heidenhain type of Creutzfeld-Jakob disease.In a 64-year old woman with progressive visual impairment for 4 weeks, probable Creutzfeld-Jakob disease without myoclonus was diagnosed after rapidly progressive mental deterioration had also developed, and CSF and EEG showed characteristic findings. Pattern-reversal and flash visually-evoked potentials, recorded 5, 6, 7 and 8 weeks after onset, showed a maximum P100 latency of 210 ms, 8 weeks after onset, and a maximum N75/P100 amplitude of 33.1 microV, 5 weeks after onset. While the P100 latency progressively increased, the N75/P100 amplitude continuously decreased after reaching its maximum. In the Heidenhain type of Creutzfeld-Jakob disease giant visually-evoked potentials may be recorded during the early stages of the disease, even in the absence of myoclonus. Visually-evoked potentials may prove useful in diagnosing Creutzfeld-Jakob disease with atypical initial presentation.- - - - - - - - - - ranking = 1keywords = giant (Clic here for more details about this article) |
2/19. Disinhibition of somatosensory and motor cortex in mitochondriopathy without myoclonus.OBJECTIVE: To test electrophysiologically, if patients with mitochondriopathy but without evidence of myocloni have subclinical signs of disinhibition in motor and somatosensory cortices. methods: Two patients were studied and compared with age-matched control groups. RESULTS: In both patients, giant somatosensory evoked potentials after median nerve stimulation and a reduced intracortical inhibition tested by transcranial magnetic stimulation in a paired pulse paradigm indicated a dysfunction of inhibitory circuits in the motor as well as the somatosensory cortex. In addition, the somatosensory evoked 600 Hz activity recorded by magnetoencephalography was abolished. CONCLUSIONS: patients with mitochondriopathy may suffer from a subclinical disturbance of inhibition in the sensorimotor cortex. The loss of 600 Hz activity indicates that these high-frequency oscillations could reflect the activity of inhibitory neurons in the somatosensory cortex.- - - - - - - - - - ranking = 1keywords = giant (Clic here for more details about this article) |
3/19. Segmental myoclonus and basilar artery. Giant aneurysm. Case report.A 70 years-old man was admitted at our hospital because of unstable angina pectoris. He had essential hypertension and right hemiplegia from a ischemic stroke two years before admission. On neurologic examination, it was found mental disorientation, unstable emotionality, right spastic hemiparesis with right Babinski sign, and segmental myoclonus affecting the superior lip and the palate (palatal nystagmus) on the right side. On the CT scan, a giant aneurysm of the basilar artery was detected. We conclude that the segmental myoclonus could be explained by ischemic lesions in the Guillain-Mollaret triangle.- - - - - - - - - - ranking = 1keywords = giant (Clic here for more details about this article) |
4/19. Cortical reflex myoclonus associated with mitochondrial myopathy, encephalopathy, lactic acidosis and stroke-like episodes (MELAS): a case report.A 9-year-old female MELAS patient with myoclonus is reported, with emphasis on the results of electrophysiological studies of the myoclonus. At age 5 years she experienced a stroke-like episode, and a diagnosis of MELAS was made at age 6 years on the basis of muscle biopsy findings. At age 9 years spontaneous and segmental myoclonus, predominantly affecting the upper extremities, developed because of complications. Electrophysiological examination, including of somatosensory-evoked potentials (SEPs) and averaged EMG for long loop reflexes, revealed so-called "giant SEP" and enhanced long loop reflexes reflecting cortical hyperexicitability. Jerk-locked averaging yielded no myoclonus related spikes, but myoclonus-contingent 4-5 Hz theta bursts appeared. These findings suggest that some types of MELAS may be associated with cortical types of myoclonus.- - - - - - - - - - ranking = 1keywords = giant (Clic here for more details about this article) |
5/19. Cortico-muscular coupling in a patient with postural myoclonus.We investigated the cortico-muscular coherence in a patient with posturally induced cortically originating negative myoclonus. We recorded simultaneously 50 channels EEG and EMG from quadriceps and biceps femoris muscles of the left upper leg. Three experimental conditions were investigated with the patient in a seated position: (i) recording during rest (rest), (ii) recording while the patient had to hold his left leg horizontally stretched out (Postural), and (iii) recording while the patient had to hold his left leg horizontally stretched out against a vertical force (Postural against force). Coherence, phase difference and cumulant density were computed as indicators for cortico-muscular coupling. The cortical component preceding the silent period was shown by averaging and was reconstructed. During postural and postural against force conditions, the EEG over the vertex was significantly coherent with EMG, in alpha (7-15 Hz) and beta range (15-30 Hz). The strongest coherence peak was at 21 Hz. No high-frequency coherence was observed. The phase difference and the cumulant density estimate corresponded to a 32 ms time lag between motor cortex and muscles, with EEG leading. The broadening of the coherence spectrum at which the motor cortex drives the muscles together with the excessive coherence levels and the giant SEP could reflect the hyperexcitability of the sensorimotor cortex. The frequency content of the coherence may be characteristic for this type of myoclonus. The results lend support to the view that the frequency analysis may have some diagnostic potential in cortical myoclonus.- - - - - - - - - - ranking = 1keywords = giant (Clic here for more details about this article) |
6/19. Electrophysiological and pharmacological studies of somatosensory reflex myoclonus.reflex myoclonus displays symptomatological heterogeneity involving the cortical and brain stem types that seem to originate above the spinal cord. Three cases of generalized myoclonus proved to be spontaneous and stimulus-sensitive, and increased with action. Segmental spinal myoclonus was spontaneous, stimulus-sensitive and rhythmical and decreased with action. Two cases of post-anoxic myoclonus seemed to be of the reticular reflex in which myoclonus was manifested in all muscles, particularly the proximal ones, and for which the EEG showed no spikes preceding myoclonus. The evoked electromyogram showed a long-loop reflex (LLR) of high amplitude, with no giant somatosensory evoked potential (SEP). Pharmacological examinations showed that the thyrotropin-releasing hormone (TRH) enhanced the onset of myoclonus, shortened the latency of the LLR and increased its amplitude, but caused no remarkable changes in SEP. These results indicate that TRH stimulates the medullary reticular neuron, thereby enhancing reticular reflex myoclonus. The myoclonus of a 3rd case was believed to be cortical reflex myoclonus on the basis of the emergence of giant SEP, increased LLR and the onset of spikes in the EEGs preceding myoclonic jerks, as ascertained by jerk-locked averaging analysis with muscular discharge. Pharmacologically, LLR, SEP and myoclonus showed no definite changes in response to TRH. Segmental myoclonus which seemed to have a spinal origin, showed no giant SEP, enhanced LLR or cortical spikes in the electrophysiological studies. No definite clinical or electrophysiological changes in response to TRH were observed. We believe the TRH administration test may be useful in the differential diagnosis of stimulus-sensitive myoclonus. In addition, the origins and nature of these types of reflex myoclonus are discussed.- - - - - - - - - - ranking = 3keywords = giant (Clic here for more details about this article) |
7/19. Spinal myoclonus with giant somatosensory evoked potentials and enhanced long-loop reflex: a case report.We describe a patient with an ischaemic lesion of the cervical spinal cord who presented with clinical evidence of stimulus-sensitive, multisegmental myoclonic jerks restricted to the truncal and proximal limb muscles and accompanied by electrophysiological features (giant somatosensory evoked potentials and enhanced long-loop reflex) of cortical myoclonus. We hypothesize that these features might result from a loss of inhibitory influences on the sensory input to cortical structures: a concomitant contribution of spinal and cortical hyperexcitability seems to have played a crucial role in inducing myoclonus in our patient.- - - - - - - - - - ranking = 5keywords = giant (Clic here for more details about this article) |
8/19. Cortical mechanisms mediating asterixis.We describe a patient with chronic renal failure who suffered multifocal action-induced jerks. electromyography (EMG) recorded the typical silence of asterixis. back-averaging the EEG activity preceding the EMG silent periods in the forearm showed a biphasic wave antedating the asterixis by 23 ms. Somatosensory evoked potentials (SEPs) after median nerve stimulation were pathologically enlarged on both hemispheres. Brain-mapping of the biphasic wave preceding asterixis and the giant SEPs indicated a common origin in the sensorimotor cortex. This observation provides further documentation of a cortical origin for some types of asterixis in humans.- - - - - - - - - - ranking = 1keywords = giant (Clic here for more details about this article) |
9/19. Generators and temporal succession of giant somatosensory evoked potentials in cortical reflex myoclonus: epicortical recording from sensorimotor cortex.OBJECTIVE: To clarify the generator mechanism of giant somatosensory evoked potentials (giant SEPs) and the hyperexcitability of primary somatosensory and motor cortices (SI and MI). methods: In a patient with intractable focal seizures manifesting cortical reflex myoclonus of the left foot, giant SEPs to left tibial nerve stimulation were epicortically recorded as a part of presurgical evaluation with subdural electrodes. RESULTS: In the single pulse SEPs, enlarged P1-N1 components were observed at the foot area of the SI and MI (86.5-258.8 microV, respectively), and the peak latencies were always shorter at SI than at MI by 6 ms. Similar findings were obtained for peroneal and sural nerve stimulation. In the paired pulse SEPs, the second response was less suppressed, as compared to other interstimulus intervals (ISIs), with ISIs of 40 and 200 ms both at SI and MI. CONCLUSIONS: In this particular patient, cortical hyperexcitability to somatosensory stimuli seems to originate from SI but subsequently both SI and MI are responsible for the generation of giant SEPs and cortical reflex myoclonus. SIGNIFICANCE: Somatosensory and primary motor cortices both generated enhanced early cortical components of SEPs, most likely by enhancing the latter by the former.- - - - - - - - - - ranking = 8keywords = giant (Clic here for more details about this article) |
10/19. myoclonus and sensorimotor integration in a patient with Ramsay Hunt syndrome.Clinical and neurophysiologic studies were done on a patient with action myoclonus secondary to Ramsay Hunt syndrome (dyssynergia cerebellaris myoclonica). Myoclonic jerks in the arms were much more common during movements directed to a target than in other movements. They appeared to be triggered primarily by external sensory inputs relevant to the movement rather than by the motor activity itself. Both somatosensory and visual inputs appeared able to trigger the myoclonic jerks. Myoclonic jerks in the deltoid muscle followed finger contact with a target by approximately 100 msec. Electrical stimuli delivered to the fingers during a reaching movement also triggered myoclonic jerks with a similar latency and also evoked giant cortical potentials which preceded the myoclonic jerks in deltoid by 15-20 msec. Our results suggest that during sensory guided movements, sensory inputs relevant to successful completion of the movement may have access to motor systems controlling the muscles involved. In our patient, who likely has lesions involving the cerebellar nuclei and/or cerebellar cortex, these sensory inputs appeared to result in an excessive motor response, possibly through mechanisms involving cerebellar-motor cortex connections.- - - - - - - - - - ranking = 1keywords = giant (Clic here for more details about this article) |
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