[Somatic mosaicism of p(CTG)n expansion in a case of myotonic dystrophy with parotid tumor].

Myotonic dystrophy (MD) is an autosomal dominant systemic disorder with an unstable expansion of the CTG triplet repeat in the 3'-untranslated region of the gene encoding myotonine protein kinase (DMPK) which maps to chromosome 19q13.3. Somatic mosaicism of CTG repeats in MD has been reported; and it has been observed that CTG repeats in tumor tissues associated with MD are more expanded than the other tissues. It is not rare that parotid tumors are found in patients with MD. We performed Southern blot analysis for tissues from the parotid tumor, the normal parotid gland, the skeletal muscles, and the leukocyte from a 60-year-old patient with MD. CTG repeat was most expanded in the parotid tumor, and the normal parotid gland had longer expansion of CTG repeat than the skeletal muscles. The leukocyte had the shortest expansion of CTG repeat. The expansion of CTG repeat in the parotid tumor may be related to active cell division and may underlie the occurrence of tumors in MD.

[Pure word deafness after cerebral hemorrhage in the left temporal lobe: a case report].

We report a patient with pure word deafness after subcortical hemorrhage in the left temporal lobe. Repetition and auditory comprehension were severely impaired, while reading and visual comprehension of the same material were almost normal. He did not show hearing loss, but speech discrimination and melody recognition was poor. On the speech discrimination test, his score was low especially in the right ear. The threshold on the directional hearing test was mildly elevated. There was no temporal summation by click sounds. CT and MRI disclosed a subcortical hematoma in the left superior temporal gyrus. PET demonstrated hypoperfusion in the surrounding area, which was not activated by hearing a story. It was considered that pure word deafness in this case was due to the interruption of auditory inputs to Wernicke's area from both hemisphere by the hematoma. After 5 months, auditory comprehension recovered so that he did not have difficulty in conversation. Speech discrimination improved in both ears, probably due to the recovery of two auditory pathways; the ipsilateral pathway through the left auditory radiation and the contralateral pathway through the right auditory radiation and the corpus callosum. This case suggests that in pure word deafness due to a unilateral lesion, the improvement in speech discrimination during follow-up period may provide a clue as to the site of the responsible lesion and its recovery.

[Retrocollis and oculogyric crisis in association with bilateral putaminal hemorrhages].

A 50-year-old man with a history of hypertension developed right hemiparesis in February, 1985. Four years later, he noted tremor and involuntary extension of the neck (retrocollis) which was aggravated by walking or emotional stimuli. In addition to retrocollis, which was most pronounced upon turning the head to the left or backward, there also was upward deviation of the eyes (oculogyric crisis) and contraction of the left orbicularis oculi muscle. Magnetic resonance imaging study revealed one small old hematoma in the left posterior putamen and two in the right lenticular nucleus (one in the posterior putamen and the other in the globus pallidus). The findings in this case and in other reported cases of symptomatic retrocollis suggest that bilateral lesions of the putamen are associated with this type of focal dystonia.

SEPs in two patients with localized lesions of the postcentral gyrus.

Scalp distributions of median nerve SEPs were studied in normal controls and 2 patients with localized lesions of the postcentral gyrus. In controls, parieto-occipital electrodes registered N20-P27 while frontal electrodes registered P20-N27. Other small components, parieto-occipital P22 and frontal N22, were recognized in about half of the control records. The wave forms at a frontal and a parieto-occipital electrode, both distant from the central region, formed exact mirror images of each other concerning N20-(P22)-P27 and P20-(N22)-N27. Electrodes near the central region contralateral to the stimulation registered cP22-cN30 (central P22 and central N30). When the postcentral gyrus was damaged, N20/P20-P27/N27 and cP22-cN30 were eliminated and the only remaining components were a frontal negative wave (frN) and a contralateral parieto-occipital positive wave (poP). Digital nerve stimulation also evoked poP and frN in both cases. In case 2, poP coincided with P22 of the non-affected side. The following generators were proposed; N20/P20-P27/N27: area 3b, cP22-cN30: areas 1 and 2, poP/early frN (= P22/N22): area 4 at the anterior wall of the central sulcus (due to direct thalamic inputs to motor cortex), late frN: uncertain (SMA?, SII?).

Widespread N18 in median nerve SEP is preserved in a pontine lesion.

Widespread N18 potential to median nerve stimulation was preserved in a patient who had profound unilateral disturbance of deep sensation and a lesion of the pontine medial lemniscus confirmed by MRI. It was concluded from this result that at least a significant part of the N18 potential was generated caudal to the pontine level or at higher levels via extralemniscal pathways. Careful review of studies in man with intraoperative recordings seemed to support that the N18 potential already exists at the medullary level. We suggested that the potential generated at the cuneate nucleus which was described in cats may correspond to part of the N18 potential.

Somatosensory evoked potential recovery (SEP-R) in myoclonic patients.

Recovery of somatosensory evoked potentials (SEPs) was studied by paired stimulation of the median nerve in patients with various kinds of myoclonus. This technique revealed the hyperexcitability of the central nervous system (CNS) which could not be detected by the conventional SEP technique using a single stimulus. This technique would be useful for studying the excitability of the CNS.

[A case of chronic inflammatory demyelinating polyradiculoneuropathy with orthostatic hypotension].

A 27-year-old man was admitted to our hospital for his legs' numbness of subacute onset and discomfort while standing. No specific previous history was found and his family history was non-contributory. On admission, his general status was unremarkable except for arterial hypertension and mild tachycardia. Moderate impairment of superficial sensations and dysesthesia were noted in the distal extremities, tongue, oral cavity, and lips. Deep sensation was moderately impaired in the lower legs. Romberg sign was positive. He had mild weakness in the proximal muscles of the lower extremities. Hyporeflexia was noted in all extremities, but Achilles reflexes were absent. Pathologic reflexes were not noted. He fainted after two minute standing. On laboratory examination, serum IgM, C3, and C4 were mildly elevated. CSF protein level was prominently high without CSF pleocytosis. MCV was mildly decreased, and F wave conduction velocity was prominently decreased in the posterior tibial nerve, SCV was also mildly decreased in the right sural nerve. Needle electromyography showed mild neuropathic changes. Left sural nerve biopsy showed no abnormal finding in the myelinated and unmyelinated fibers. A 60 degree head-up tilting test caused a hypotensive attack, and Valsalva ratio was decreased. However, hand grip test and cold pressor test were normal. The response to noradrenaline infusion test and CVR-R were also normal. Muscle sympathetic activity (MSA) was recorded from the tibial nerve using a tungsten microelectrode (Iwase, et al.). His basic activity was higher and responsiveness was lower than age-matched normal controls. The regression line existed above the normal range.(ABSTRACT TRUNCATED AT 250 WORDS)

Onset and offset of electromyographic (EMG) silence in asterixis.

The onset and offset of electromyographic (EMG) silence were studied physiologically by silent period locked averaging method (SPLA) combined with a computer-assisted method for detecting EMG changes in 11 patients with asterixis of various aetiologies. The onset followed the EMG discharge which was closely associated with a sharp wave probably generated by the motor cortex in three patients. No EEG activity could be shown to be related to the offset of EMG silence in every patient. Jerky movement of asterixis was temporally related to the offset of EMG silence rather than the onset.

Magneto-electrical stimulation of central motor pathways compared with percutaneous electrical stimulation.

The central motor conduction to the relaxed muscles was studied in 30 normal volunteers using magneto-electrical stimulation (MES) of the central motor pathways. The results were compared with those obtained by the percutaneous electrical stimulation technique (PES) described previously. None of the cortical and spinal latencies (Lcor and Lsp, respectively) and the central motor conduction time were different between MES and PES in the upper limb muscles. In some lower limb muscles, however, the Lsps of MES were significantly shorter than those of PES. This was probably because the magnetic stimulation over the lumbar spinal column activated the motor roots at their exit from the spinal canal rather than the level of conus medullaris, at which activation occurs in the electrical stimulation.

Posterior cervical N13 in median nerve SEP has two components.

Somatosensory evoked potentials (SEPs) to median nerve stimulation were investigated in normal controls and patients with cervical lesions. Attention was paid primarily to the N13 and P13 components in the posterior and anterior cervical records with non-cephalic references. In normal subjects the CV2 and CV6 electrodes registered N13 with almost the same amplitude. Dissociation between N13 at the CV2 electrode (ucN13) and N13 at the CV6 electrode (lcN13) was observed in the patients. In 4 patients with cervical dorsal column lesions, lcN13 was preserved but ucN13 was almost completely absent. Anterior cervical P13 (acP13) was preserved. In a patient with syringomyelia, lcN13 and acP13 were greatly attenuated while ucN13 was relatively well preserved. These results suggested that the origins of ucN13 and lcN13 are different. The generator of lcN13-acP13 was assumed to be the postsynaptic potential of the dorsal horn interneurons. Upon comparison with previous animal studies and intraoperative studies, it was concluded that the generator of ucN13 is the postsynaptic potential of the cuneate nucleus.

Physiological analysis of asterixis: silent period locked averaging.

Asterixis was studied in nine patients, using a new electrophysiological technique: silent period locked averaging (SPLA). There were two types of electromyographic (EMG) silence in the movements clinically judged as asterixis. The jerky movement in one of the two types might be caused by the silent period after the subclinical cortical myoclonus. SPLA would be useful for studying asterixis as well as other EMG silences.

[Magneto-electrical stimulation (MES)--compared with percutaneous electrical stimulation (PES)].

The central motor conduction was studied in 30 normal volunteers using a recently developed magneto-electrical stimulation technique (MES). The results were compared with those obtained by percutaneous electrical stimulation technique (PES) described previously. We made a magnetic stimulator similar to that of Barker et al. To stimulate the motor cortex, the magnetic coil was placed over the head. It was placed over the seventh cervical spinous process (C7) for cervical stimulation, and the first lumbar spinous process (L1) for lumbar stimulation. Cortical stimulation was performed when the subjects were at rest, and also at during weak voluntary contraction in some of them. Recordings were made from the deltoid (Del), biceps brachii (Bi), extensor carpi radialis (ECR), thenar, quadriceps femoris (Quad), tibialis anterior (TA) and flexor hallucis brevis (FHB) muscles with a pair of surface electrodes. The cortical and spinal latent periods (Lcor and Lsp, respectively) were measured. The central conduction time (CCT) was obtained by subtracting Lsp from Lcor for each muscle. In all subjects, responses were readily obtained by cortical, cervical and lumbar stimulations without discomfort in all the muscles examined. The cortical responses with amplitudes of more than 1mV could be recorded even in the lower limb muscles. There were no significant differences in Lsp and CCT between MES and PES, in all the upper limb muscles examined. The Lcors of the lower limb muscles obtained by MES were not different from those obtained by PES. However, the Lsps obtained by MES were significantly shorter than those by PES in the Quad and TA muscles.(ABSTRACT TRUNCATED AT 250 WORDS)

Physiologic analysis of central motor pathways--simultaneous recording from multiple relaxed muscles.

The central motor pathways were studied with the technique of percutaneous electrical stimulation of the central nervous system in 40 normal volunteers. There were no significant differences between the right and left sides, or between males and females. A linear correlation between the cortical latency (Lcor) or the spinal latency (Lsp) and body height was observed, however, there was no correlation between the central conduction time (CCT) (Lcor-Lsp) and body height. Consequently, the CCT appears to provide a reliable estimate of the function of central motor pathways. We have established normal values for eight muscles at rest that would be required for localizing a very small intraspinal lesion.