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Although the generation of symptomatic palatal tremor (SPT) is thought to derive from the abnormal activity of hypertrophic inferior olivary neurones, the actual mechanism of SPT has not yet been elucidated. We therefore investigated the relationship between SPT and the pathological process of inferior olivary hypertrophy (IOH). We examined 16 autopsied subjects with cerebrovascular lesions of the dentate‐olivary tracts. We analysed the size of the olives, the number of olivary neurones, synaptic, axonal and astrocytic changes in the olives and the clinical course in the subjects. SPT was observed in eight patients, in seven of whom it appeared 1–2 months after interruption of the afferents then progressed to reach a peak ∼1–2 years from the onset. SPT persisted for the rest of the subjects’ lives without decreasing in severity. Neuronal hypertrophic change began 20–30 days after the onset of the causative lesions and reached maximum size, accompanied by prominent astrocytosis and synaptic and axonal remodelling, 6–7 months later. The number of olivary neurones decreased to <10% of that in controls in patients who survived >6 years. Despite the persistence of SPT, both the myelin and the axons of efferent fibres from olivary neurones were severely degenerated in patients who survived several years. Therefore, the appearance of SPT may depend on the hyperactivity of olivary neurones released from inhibitory inputs until the peak of both IOH and SPT. However, the persistence of peak intensity and distribution of established SPT is probably due to both the disturbance of natural rhythmicity in the body and the lack of feedback from the abnormal movement resulting from the dysfunction of the olive.

Although the generation of symptomatic palatal tremor (SPT) is thought to derive from the abnormal activity of hypertrophic inferior olivary neurones, the actual mechanism of SPT has not yet been elucidated. We therefore investigated the relationship between SPT and the pathological process of inferior olivary hypertrophy (IOH). We examined 16 autopsied subjects with cerebrovascular lesions of the dentate-olivary tracts. We analysed the size of the olives, the number of olivary neurones, synaptic, axonal and astrocytic changes in the olives and the clinical course in the subjects. SPT was observed in eight patients, in seven of whom it appeared 1-2 months after interruption of the afferents then progressed to reach a peak approximately 1-2 years from the onset. SPT persisted for the rest of the subjects' lives without decreasing in severity. Neuronal hypertrophic change began 20-30 days after the onset of the causative lesions and reached maximum size, accompanied by prominent astrocytosis and synaptic and axonal remodelling, 6-7 months later. The number of olivary neurones decreased to <10% of that in controls in patients who survived >6 years. Despite the persistence of SPT, both the myelin and the axons of efferent fibres from olivary neurones were severely degenerated in patients who survived several years. Therefore, the appearance of SPT may depend on the hyperactivity of olivary neurones released from inhibitory inputs until the peak of both IOH and SPT. However, the persistence of peak intensity and distribution of established SPT is probably due to both the disturbance of natural rhythmicity in the body and the lack of feedback from the abnormal movement resulting from the dysfunction of the olive.

We investigated the effect of fluoxetine, a selective serotonin reuptake inhibitor (SSRI), on L-DOPA-derived extracellular dopamine (DA) levels in the striatum of rats with nigrostriatal dopaminergic denervation using in vivomicrodialysis. Treatment with fluoxetine (10 mg/kg, i.p.) induced a 41 reduction in the cumulative amount of extracellular DA during 300 min following L-DOPA administration (50 mg/kg, i.p.;p< 0.01). This effect was antagonized by pretreatment with WAY-100635, a potent 5-HT1A antagonist, indicating that this effect of fluoxetine is due to its indirect 5-HT1A agonistic property. These results suggest that SSRIs may impair motor functions in patients with Parkinson's disease by reducing efflux of exogenous L-DOPA-derived DA.

We analyzed onset and peak latencies of the N20 response of median nerve somatosensory evoked potentials (SEPs) in 21 healthy subjects by simultaneous recordings with noncephalic or ear reference from multiple scalp sites. The cortical onset was defined as the fork at which the contralateral parietal and frontal or ipsilateral parietal waves diverged. We found the N20 onset unchanged between noncephalic and ear reference recordings, or among the recordings around the contralateral centroparietal scalp. The N20 peak was prolonged when the recording position moved posteriorly. We suggest that N20 onset latency is more stable than N20 peak. © 2000 John Wiley & Sons, Inc. Muscle Nerve 23: 278–282, 2000.

We analyzed onset and peak latencies of the N20 response of median nerve somatosensory evoked potentials (SEPs) in 21 healthy subjects by simultaneous recordings with noncephalic or ear reference from multiple scalp sites. The cortical onset was defined as the fork at which the contralateral parietal and frontal or ipsilateral parietal waves diverged. We found the N20 onset unchanged between noncephalic and ear reference recordings, or among the recordings around the contralateral centroparietal scalp. The N20 peak was prolonged when the recording position moved posteriorly. We suggest that N20 onset latency is more stable than N20 peak. © 2000 John Wiley & Sons, Inc. Muscle Nerve 23: 278–282, 2000.

The effect of L-dihydroxyphenylalanine (L-DOPA) on extracellular dopamine (DA) in the striatum was determined by microdialysis in 6-hydroxydopamine (6-OHDA)-lesioned rats treated with and without the serotonergic neurotoxin 5,7-dihydroxytryptamine (5,7-DHT). At the same time the intensity of L-DOPA-induced rotational behavior was assessed. In 6-OHDA-lesioned rats treated with 5,7-DHT, L-DOPA (50 mg/kg, i.p.) increased extracellular DA only to 20 of that measured in animals not treated with 5,7-DHT. Like-wise, 6-OHDA-lesioned rats treated with 5,7-DHT exhibited a significantly lower number of L-DOPA-induced rotations. These results suggest that serotonergic terminals in the striatum can convert exogenously administered L-DOPA into DA that can be released into the extracellular space.

We report a case of Isaacs' syndrome showing F‐wave hyperexcitability which was reversible after either epidural block or plasmapheresis. A 14‐year‐old girl with progressive muscle cramp and myokymia in the legs showed high amplitude, long duration, polyphasic F‐waves after either tibial nerve or peroneal nerve stimulation. Potassium current of PC‐12 cell membrane was suppressed by her serum, IgM of which strongly reacted with proteins of approximately 50 kDa of the lysates of a PC‐12 cell line. After an epidural nerve block with 1 per cent lidocaine 10 ml, the myokymia temporally improved, during which time the hyperexcitable F‐waves became normalized. We treated her with double filtration plasmapheresis, which resulted in remarkable improvement of myokymia; simultaneously, the abnormal F‐waves showed a decrease in amplitude, duration, and in the number of phases. We concluded that there was hyperexcitability of the proximal site of motor fibers in our patient, and possible immune mechanisms gave rise to the myokymia and unusual F‐wave features.

To study the correlation between somatosensory central conduction time (CCT) and the subject's height, we recorded somatosensory evoked potentials (SEPs) from the neck and scalp elicited by median nerve stimulation in 72 normal young adults. We determined the CCT in each subject from peak-to-peak and onset-to-onset measurements. The mean value for the onset CCT was 6.2 ± 0.4 msec and for the peak CCT, 5.7 ± 0.5 msec. The peak CCT was significantly shorter but showed a wide range. There was a significant correlation between the onset CCT, but not the peak CCT, and height. Our findings confirm that the length of the central somatosensory pathway is proportional to the subject's height and indicate that the “conventional” peak CCT measurement of median nerve SEPs is inadequate.

Abstract: Acute ataxic neuropathy is characterized by sensory ataxia and areflexia. There is no established treatment. We tried immunoadsorption plasmapheresis 15 days after the onset for a 46‐year‐old woman suffering from this neuropathy. She could not walk even with assistance because of sensory ataxia. A sural nerve biopsy revealed active axonal degeneration and loss of myelinated fibers. We tried 5 sessions of plasmapheresis during 2 weeks. She could walk with assistance 12 days after the beginning of the plasmapheresis treatment. It took 3 months for her to be able to walk over 5 m without assistance, and she had severe sensory ataxia over a 17 month follow‐up period. Immunoadsorption plasmapheresis started within 2 weeks after the onset of acute ataxic neuropathy may have beneficial effects if the axonal degeneration is mild. The plasmapheresis, however, should be continued for a longer period. A double blind study is necessary to clarify the effectiveness of this treatment on acute ataxic neuropathy.