Pathophysiologic Approach by Blink Reflex and EMG Studies in Essential Blepharospasm Comparison with Other Facial Involuntary Movement

Background and objectives: Blepharospasm (BS) is best categorized as focal dystonia, but the biochemical and neuroanatomical mechanisms are poorly understood. We performed this study in order to postulate the pathophysiologic mechanism of essential BS, using blink reflex test and EMG studies. METHODS: We studied 24 patients with essential BS and 51 normal adults. Blink reflex tests and EMG on orbicularis oculi muscle were performed in all patients. We evaluated our electrophysiological data, comparing with those obtained from other studies, in which bulbocavernosus reflex, H-reflex, and T-reflex tests were done. We also compared our EMG data with those of hemifacial spasm and facial myokymia in other studies. Results: 1. Rl response latency of blink reflex test in 24 patients with essential BS was not changed, but R2 latency in the papient group was significantly shortened, comparing with those of normal control group. These results can be explained by overexcitability of the interneuron with polysynaptic pathway. Another supporting evidence is the fact that the latency of polysynaptic bulbocavernous reflex test in upper motor neuron lesion is shorter than normal control, although the latency of monosynaptic H-reflex and T-reflex test are not changed. 2. EMG on orbicularis oculi muscle in patients with essential BS showed spontaneous MUPs at irregular intervals at rest, while those in patients with hemifacial spasm and facial myokymia, known to be caused by overexcitability of facial nucleus, showed spontaneous MUPs at regular intervals. EMG in patients with essential BS, during the period of spasm, showed relatively long brief bursts at irregular intervals from 30 to 100 ms, lasting inconstant duration ranging from 30 to 300 ms. CONCULSIONS: It is suggested that the pathophysiology of essential BS is overexcitability of interneuron due to disinhibition in inhibitory interneuron, and that EMG findings of essential BS are remarkably different from those of hemifacial spasm and facial myokymia.

A Case of Paramyotonia Congenita

Paramyotonia congenita (PMC), an autosomal dominant non-progressive muscle disorder, is characterised by cold-induced stiffness followed by muscle weakness. The weakness is considered to be caused by a dysfunction of the sodium channel in muscle fiber. We report a 37-year-old male patient with PMC, complaining of episodic myotonia and motor weakness on cold exposure. In this patient, we performed clinical and neurological examination, electrophysiologic examination and muscle biopsy. On electrophysiologic study, needle EMG showed spontaneous myotonic discharges at room temperature but disappeared after cooling. Amplitude of compound action potential in abductor pollicis brevis muscle decreased significantly after cooling the tested extremity. Muscle biopsy showed a minimal variation of muscle fiber diameters, internal nuclei, chained nuclei, occasional atrophic fibers in vastus lateralis muscle. His mother, his son, three of six siblings, and five of eleven nephewes are affected with same symptomes.

Motor Involvement in Herpes Zoster Using EMG Study

Herpes zoster(HZ) is well known as a benign viral infection affecting the sensory nerves. That this disease may also cause motor paralysis is less well known. We performed this study to evaluate the exact prevalence of motor involvement and to compare the extent of EMG abnormality with that of skin lesions. Ninety patients with HZ who did not sho w clinical motor weakness except 4 patients with Ramsay-Hunt syndrome were studied prospectively for 2 years using EMG which is generally known to be very sensitive method for detection of motor involvement. The results turned out as follows. I.. In patients with Herpes zoster, motor involvement(denervation m EMG study) is 56.67%(51/90 patients) and subclinical motor involvement is 54.65%(47/86 patients). 2. There was no statistically significant difference m the rates of motor involvement among the cranial, cervical, thoracic & lumbosacral regions. 3. There was no statistically significant difference in the rates of motor involvement between the male and female, although the positivity were higher in male. 4. The subclnical motor involvement was gradually increased by aging, as seen in clinical motor paralysis of other report. 5. There was significant statistic difference between the number of dermatome involved by skin lesion(mean 1.88) and that of myotome with motor involvement (mean 2.55). In conclusion, it is suggested that subclnical motor involvement in Herpes zoster is rather frequent and extensive than generally expected.

A case of Myasthenia Gravis associated with Premature ovarian failure and thyroid autoanibodies

Myasthenia gravis (MG) is regarded as autoimmune disorder of neuromuscular transmission and apparently is due to formation of humoral antibody that cross-link to acetylcholine receptor at skeletal muscle end plate. Patients with autoimmune diseases often have circulating antibodies to a variety of different autoantigens and show a variety of manifestations of autoimmune diseases in more than one organ. Therefore, MG patients frequently have manifestations of autoimmune diseases such as thyroid disease, rheumatoid arthritis and systemic lupus erythematosus. But MG in association with premature ovarian failure (POF) rarely has been described. A case of MG with POF and thyroid autoantibodies was experienced and presented with a brief review of literature.

Excitotoxic change of Hippocampal Neuron by Kainic Acid in Rat Brain

The excitotoxic effect of kainic acid on dendrites and neuronal cell bodies of hippocampus and dentate gyrus was studied with time (1, 4, 8, 16 hours, 2, 7, 14 days) light and electron microscopically by intraperitonial injection into rat. The results obtained were as follows. 1) The acute dendrotoxic effect was observed as laminar pattern of swelling along pyramidal cell body layer and dendritic fields and was most prominently at 2-4 hours after kainic acid injection. In ultractructural study, the acute change occurred in dendrites of pyramidal cells in hipocampus because the synapses between nerve terminals and swollen components were not destroyed and remained intact and, identified the swollen structures as dendrites. So, it was obvious from the results that the acute change by kainic acid was osmolysis and was continued till initial 4 hours but was finally faded out. 2) The distribution of kainic acid receptor within hippocampus was different because the prominent dendritic swelling occurred in proximal basilar dendritic field of CA 3 and 4 and the proximal and distal basilar dendritic fields of CA 1 and 2, and no change was observable in dentate granule cell. The sensitivity of hippocampal dendritic fields to kainic acid could be put in decreasing order as CA3, CA4, CA1, CA2 and dentate granule cell 3) With the elapse of time, the acute change disappeared and pyramidal cells began to degenerate by the chronic reaction about 7 days after kainic acid injury, and the pyramidal cell density in CA regions greatly decreased. Almost all pyramidal cells degenerated the dentate granule cells were not affected to kainic acid throughout the time. In conclusions, hippocampal neurons were postulated to be very sensitive to kainic acid, and in contrast to the gradual disappearance of acute change within several hours, the degeneration of pyramidal neurons by chronic change was developed within several days regardless of acute change.