Familial startle disease (hyperexplexia). Electrophysiologic studies

Six affected members from a family of 15 patients with familial startle disease (hyperexplexia) underwent extensive electrophysiologic evaluation. The most marked abnormality consisted of prominent C response 60 to 75 ms after median and peroneal nerve stimulation. The somatosensory evoked responses were also relatively high in amplitude. These findings suggest that hyperactive long-loop reflexes may constitute the physiologic basis of startle disease.     

Electrophysiological studies of myoclonus

As myoclonus is often associated with abnormally increased excitability of cortical structures, electrophysiological studies provide useful information for its diagnosis and classification, and about its generator mechanisms. The electroencephalogram-electromyogram polygraph reveals the most important information about the myoclonus of interest. Jerk-locked back-averaging and evoked potential studies combined with recording of the long-latency, long-loop reflexes are useful to investigate the pathophysiology of myoclonus further, especially that of cortical myoclonus. Recent advances in magnetoencephalography and transcranial magnetic stimulation have contributed significantly to the understanding of some of the cortical mechanisms underlying myoclonus. Elucidation of physiological mechanisms underlying myoclonus in individual patients is important for selecting the most appropriate treatment.     

Electrophysiological studies of myoclonus

As myoclonus is often associated with abnormally increased excitability of cortical structures, electrophysiological studies provide useful information for its diagnosis and classification and about its generator mechanisms. The EEG-EMG polygraph provides the most essential information about the myoclonus of interest. Jerk-locked back averaging and evoked potential studies combined with recording of the long latency, long loop reflexes are useful to further investigate the pathophysiology of myoclonus, especially that of cortical myoclonus. A recent advance in magnetoencephalographic techniques has contributed significantly to the elucidation of some of the cortical mechanisms underlying myoclonus. Elucidation of physiological mechanisms underlying myoclonus in each individual patient is important for selecting the most appropriate treatment of choice.     

Electrophysiological studies of a child with presumed botulism

Electrophysiological studies of a child with presumed botulism showed that the amplitude of the serially and electrically elicited blink reflexes Rl, R2 and R2’ was reduced during recovery. These findings suggest a conduction block of the facial nerves. Other nerve conduction studies and an incremental response to repetitive stimulation demonstrated a block of the presynaptic neuromuscular transmission. Results of the biological tests were negative, but those of electrodiagnosis and clinical examination favored a diagnosis of botulism. A combination of electrically elicited blink reflexes and rapid repetitive stimulation of the peripheral nerves was found to be a sensitive method of assessing the integrity of neuromuscular junctions and the subclinical impairment of muscle nerves. Received: 27 November 1997 Revised: 25 September 1998     

Electrophysiological studies on hydranencephaly

Electrophysiological studies were performed on two children with hydranencephaly that was diagnosed by CT and/or magnetic resonance imaging (MRI). Case 1 was a 4-months-old boy who had no rostral tissue above the midbrain. Case 2 was a 5-years-old boy in whom CT showed the presence of the thalamus. Short latency somatosensory evoked potentials (SSEP) in both cases exhibited the absence of cortical activity (N1 and P4) with the preservation of waves of brainstem origin. However, in case 1, the wave component N0 was not observed, while N0 was seen in case 2. Thus, the N0 was component of SSEP on median nerve stimulation in children, which corresponds to N16 in adults, may originate in the thalamus.     

Electrophysiological studies in alcoholism

Using a range of electrophysiological techniques, it has been possible to demonstrate impaired function in smaller calibre motor fibres and in distal large cutaneous sensory nerve fibres in both alcoholic patients without neuropathy and in those alcoholics with clinical manifestations of peripheral nerve disease. Evidence of more proximal involvement of Ia sensory fibres was obtained, but in the majority of our patients, large motor fibres functioned normally. The nature of the underlying pathological process is discussed.     

Electrophysiological investigations in a case of cephalic tetanus

Summary In a case of cephalic tetanus the amplitudes and the latencies of the compound action potentials recorded from the facial muscles after stimulation of the facial nerve at the mastoid were not significantly different on the two sides. With repetitive stimulation at 30/sec a pathological facilitation was observed on both sides. The blink reflex bilaterally had normal latencies but the amplitudes of the reflex potentials were always significantly lower on the paretic side. It is concluded that facial palsy in cephalic tetanus is mainly due to a functional block of conduction in the course of the peripheral nerve whereas the disturbance of neuromuscular transmission probably has little importance in these cases.

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Zusammenfassung Bei einem Fall von Kopftetanus mit rechtsseitiger Fazialisparese wurden bei Reizung des N.facialis am Mastoid von den Gesichtsmuskeln beidseits gleichhohe Summenpotentiale mit normaler Latenzzeit abgeleitet. Bei Reizung mit 30 Hz kam es beidseits zu einer pathologischen Fazilitierung der Potentialamplituden. Der Blinkreflex wies auf der paretischen Seite immer eine niedrigere Amplitude bei normalen Latenzzeiten auf als auf der Gegenseite. Aufgrund dieser Befunde und der Berichte in der Literature wird auf einen funktionellen Leitungsblock im Verlaufe des N. facialis als wichtigste Ursache der Parese geschlossen, die Störung der neuromuskulären Überleitung hat klinisch wahrscheinlich geringere Bedeutung.

     

Electrophysiological studies of NMDA receptors

Recent electrophysiological studies of NMDA receptors and of the associated ion channels (NMDA channels) have revealed five properties of this system: (1) the NMDA channels are blocked by Mg²⁺ in a voltage-dependent way; (2) the NMDA channels are permeable to Ca²⁺ as well as to Na⁺ and K⁺; (3) the NMDA channels may adopt multiple conductance states; some of the minor states (small conductances) resemble the major conductance states opened by non-NMDA agonists; (4) continued exposure to NMDA agonists produces short-term and long-term decreases in the sensitivity of the NMDA system; and (5) glycine potentiates the response to NMDA.     

重症肌无力的电生理研究

目的探讨重症肌无力（ＭＧ）患者的电生理特征及其诊断价值。方法应用针极肌电图（ＥＭＧ），重复神经电刺激（ＲＮＳ）和激发重复神经电刺激（ＡＲＮＳ）方法，对４７例ＭＧ患者的肌肉和神经肌肉传递功能进行研究。结果部分患者的肌肉见到病理自发电位及短小动作电位，具近端肌分布特征。ＡＲＮＳ阳性率（９０．６％）较ＲＮＳ阳性率（８３．０％）高。Ⅰ型患者肢体肌群存在多项电生理异常。结论适当、综合应用电生理检测技术有助于ＭＧ的早期诊断