MUSCLE-FIBER CONDUCTION-VELOCITY IN-SITU IN HYPOKALEMIC PERIODIC PARALYZES

Objectives - To clarify the diagnostic yield of conduction velocity al ong muscle fibers in situ (MFCV) in hypokalemic periodic paralyses (HO PPs). Material and methods - MFCV of the short head of biceps brachii was performed in 3 subjects with primary HOPP and in another 3 with se condary HOPP. Results - MFCV was reduced during the recovery period in 2 of the patients with hereditary HOPP and in 3 with secondary hypoka lemia due to hyperaldosteronism, diuretics, and renal tubular acidosis . One case with familiar HOPP showed fluctuating muscle weakness, but never had paralytic attacks. MFCV slowing was similar in both heredita ry and secondary HOPP. Direct stimulation during a major attack with q uadriplegia showed inexcitability of most muscle fibers. Conclusions - Inexcitability during major attacks and MFCV slowing in interictal or recovery periods evidenced sarcolemmal altered function. MFCV is a se nsitive method for the detection of membrane muscle fiber defects in H OPPs and is also an additional diagnostic criterion of these diseases.