S45. To report abnormal nerve conduction studies in two patients with hypokalemic paralysis

Abstract

Introduction In hypokalemic paralysis, hypokalemia-induced inactivity of the muscle fibre Na+K+ ATPase pump is supposed to be responsible for motor inexcitability, resulting reduced or non-recordable CMAP amplitudes. Hence, nerve conduction studies (NCS) mainly includes reversible reduction in compound muscle action potential (CMAP) amplitude. Other NCS abnormalities are very uncommon and suggest more widespread channel abnormality. We report two patients with hypokalemic paralysis with reversible NCS abnormalities. Methods Sensory-motor NCS of all four limbs (bilateral median, ulnar, tibial, peroneal and sural nerves) and other relevant blood investigations were performed in two young adult male patients during first episode of reversible quadriparesis. NCS was repeated 24 h after improvement of motor power. Secondary causes of hypokalemia were excluded by relevant investigations. Results Serum potassium (K+) was low ( Conclusion CMAP and F wave may be abnormal during hypokalemic paralysis due to abnormal Na+K+ ATPase at muscle fibres. However,other NCS abnormalities like abnormal SNAPs, prolonged DL, or non recordable proximal CMAP (specially when distal CMAP is recordable) are rarely reported in hypokalemic paralysis. These abnormalities are marker of nerve fibre abnormality and supposed to be normal in muscle disease. These abnormal and reversible NCS in present case series suggests that Na+K+ ATPase abnormalities are not restricted to muscle fibres but probably more widespread and involve nerve fibres also. However, larger study is required to evaluate this aspect of hypokalemic paralysis.