Hypokalemic periodic paralysis presenting as asymmetric focal flaccid paralysis: A case report and literature review

Patients with the most common form of hypokalemic periodic paralysis (HypoKPP) exhibit symmetrical limb weakness. However, few patients present with asymmetric limb weakness. Here, we describe a unique case of HypoKPP presenting as asymmetric focal flaccid paralysis. In addition, a literature review is performed to provide a perspective for clinical management of similar cases. We present a detailed characterization of this rare type of HypoKPP. The initial presentation was right hand weakness, which progressed to bilateral lower limb weakness. Neurological examination showed that the affected muscles were uniquely confined to specific nerve innervation, i.e., right distal median nerve-innervated muscle, right deep peroneal nerve-innervated muscle and left side. The patient's serum level of potassium was lower than normal; the decline of long exercise test (LET) was higher than normal range; neurophysiological assessment revealed low amplitude compound muscle action potential (CMAP) during attack, the CMAP and patient's weakness rapidly returned to normal level after potassium supplementation. Therefore, HypoKPP can be formally diagnosed based on neurological examination, medical history, timely neural electrophysiological examinations and measurement of blood potassium level.