Delayed radiation-induced bulbar palsy mimicking ALS

Peripheral (limb) myokymic discharges in motor neuron disease

“…Although MDs are more commonly found in limb muscles, clinical myokymia is more often observed in facial muscles, probably owing to less subcutaneous tissues than in limb muscles 11. The mechanism of generation of MDs in ALS is unclear 1 12. Multiple mechanisms such as demyelination, radiation, direct neurotoxic effects, ischaemia, hypoxia and oedema are thought to alter the axon membrane microenvironment and thereby form the basis for hyperexcitablity of the axon membrane 12.…”

“…The mechanism of generation of MDs in ALS is unclear 1 12. Multiple mechanisms such as demyelination, radiation, direct neurotoxic effects, ischaemia, hypoxia and oedema are thought to alter the axon membrane microenvironment and thereby form the basis for hyperexcitablity of the axon membrane 12. However, they might be the result of centrally generated rhythmic discharges that electronically spread to abnormally hyperexcitable anterior horn cells in a variety of peripheral and central nervous system disorders 1.…”

“…However, they might be the result of centrally generated rhythmic discharges that electronically spread to abnormally hyperexcitable anterior horn cells in a variety of peripheral and central nervous system disorders 1. The origin of MDs likely involves spontaneous depolarisation or ephaptic transmission along demyelinated segments of nerve 12. The finding of MDs on EMG is very helpful in limiting the differential diagnosis.…”

EMG-Phänomene peripherer motorisch axonaler Übererregbarkeit

“…Myokyme Entladungen finden sich unspezifisch bei einer Reihe von neurologischen Erkrankungen, wie etwa bei Motoneuronerkrankungen, antikörpervermittelten Erkrankungen spannungsabhängiger Kaliumkanäle (Isaacs Syndrom), episodischer Ataxie mit Myokymien, Multipler Sklerose, pontinen Gliomen, Hirnnervenschädigungen, demyelinisierenden Polyneuropathien, strahleninduzierten peripheren Nervenverletzungen, Karpaltunnelsyndrom, Syringobulbie, multipler Systematrophie oder etwa unter dem Einfluss des Toxins der Klapperschlange 14 45 46 47 50 51 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 .…”

Cranial Nerve XII: The Hypoglossal Nerve

“…In these patients, EMG may demonstrate myokymic discharges during needle examination of the tongue. 18 The bulbar symptoms of motor neuron disease or progressive bulbar palsy may be difficult to distinguish from those of myasthenia gravis, which may need to be considered in the differential of a patient presenting with dysarthria and dysphagia. Myasthenia gravis involves the neuromuscular junction.…”