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抄録 片側顔面痙攣の20症例に対し,blink reflexの検討を行い次の結果を得た。(1)患側のR1潜時は顔面神経ブロック未経験群では正常であったが,顔面神経ブロック経験群では遅延していた。(2)患側口輪筋からsynkinetic response (SR)が得られ,その出現率はSR1(100%),SR 2(90%),SR 2c (95%)であった。(3) SR 1潜時はR1潜時より若干延長していた。(4)刺激部位を眼窩上神経から遠ざけ,顔面神経の中枢側に近づけると,R1およびSR 1潜時は短縮し,R 2およびSR 2潜時は延長した。(5)局所麻酔剤で眼窩上神経のブロックを行うと,R2とSR 2は消失したが,R 1とSR 1は残存した。また顔面神経側頭枝のブロックではSR 1が消失した。(6)手術後,SRは消失していくが,R 1潜時の変化はみられなかった。以上の所見からSRの求心路として,SR 1は顔面神経,SR 2は三叉神経を介すると考えられた。このような逆行性および順行性のimpulseがephaptic transmissionにより容易に隣接する神経線維に伝播し,reverberating circuitが形成され,顔面痙攣を誘発すると思われた。
Blink reflexes were studied in 20 patients with hemifacial spasm.
The latencies of R 1 on the affected side was not different from that on the unaffected side in 10 patients who had no previous facial nerve block, but increased in 10 patients with experience of facial nerve block. Synkinetic responses (SR 1, SR 2 and SR 2 c) were observed by the simulta-neous recording from the orbicularis oris muscle on the affected side. SR 1 were obtained in all patients (100%), but SR 2 in 18 patients (90%) and SR 2 c in 19 patients (95%). The mean latency of SR 1 was slightly longer than the mean latency of R1.
When the site of stimulation was moved along the eyebrow from the supraorbital nerve approach-ing to the stylomastoid foramen, the latencies of R 1 and SR 1 became shorter, but R 2 and SR 2 were suppressed with increased latency. Following local anesthesia (xylocaine) to the temporal branch of the facial nerve, SR 1 was abolished with pre-served R1, R2 and SR2. On the other hand, R2 and SR 2 were abolished with preserved R 1 and SR1 following xylocaine block to the supraorbital nerve.
The result suggeted that the afferent pathway of SR 1 is the facial nerve (antidromic conduc-tion) and that of SR 2 is the trigeminal nerve. Ephaptic transmission of those antidromic and orthodromic impulses forming a reverberating cir-cuit should be one of the etiological factors in hemifacial spasm.
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