Reversible electrophysiological abnormalities in acute secondary hyperkalemic paralysis
A 57-year-old man presented in April 2011 with rapidly evolving quadriparesis of 4 hours that started proximally in both lower limbs progressing to quadriparesis making him bedbound. He had well-controlled diabetes for 15 years. Mild renal impairment was noted 3 months ago. Two months before admission, he developed progressive distal paresthesiae in the feet and hands.\nExamination revealed a middle-aged man with normal pulse, blood pressure and respiration without edema or thickened nerves. Chest, abdomen and cardiac examination were normal. He was awake, alert and oriented with normal language functions. He had generalized hypotonia with atrophy of intrinsic muscles of hands and feet. He had quadriparesis with distal more than proximal weakness []. There was graded distally dominant symmetrical sensory impairment involving touch, pain and vibration up to the knees and wrist. Muscle stretch reflexes were absent.\nMotor nerve conduction studies (NCS) revealed increased latencies, segmental reduction of conduction velocities and partial conduction blocks [, ] with absent sensory nerve action potentials (SNAP) in bilateral sural, right median and ulnar nerves. F-waves were delayed in the right median nerve [] and absent in the other nerves. He was diagnosed to have acute demyelinating polyneuropathy. Distal symmetric amyotrophy and sensory loss were considered to be due to probable diabetic neuropathy.\nSerum biochemistry revealed hyperglycemia (222 mg/dL) with elevated glycated hemoglobin (10.6%) and severe azotemia (urea 249 mg/dL, creatinine 13.2 mg/dL) with marked hyperkalemia (9.9 mEq/L). Serum creatinine kinase, calcium and magnesium were normal. Electrocardiogram revealed sinus rhythm with broad QRS complexes and tall T waves []. He had dimorphic anemia (hemoglobin 8.2 gm/dL) with bone marrow revealing early megaloblastic changes. Urgent hemodialysis was started in view of severe hyperkalemia and azotemia. There was rapid reversal of quadriparesis during dialysis, except for partial improvement in hand and foot muscles with reduction of serum potassium to 4.5 mEq/L. Sensory deficits remained unchanged. Cerebrospinal fluid revealed 5 lymphocytes/mm3 and 56 mg/dL protein.\nNerve conductions repeated on the third day revealed significant improvements [; Figures and ]. Small amplitude sural SNAP could be recorded (right 0.6 μV and left 0.8 μv) with reduced conduction velocity of 28.5 m/s (right) and 27.6 m/s (left), whereas SNAPs continued to be absent in the median and ulnar nerves. Concentric needle electromyography (CNEMG) revealed fibrillations and positive sharp waves in the hand and leg muscles with increased duration and amplitude of motor unit potentials.\nHe has been on maintenance hemodialysis since then and has had no further episodes of hyperkalemia or worsening of weakness. Oral anticoagulation was started for deep venous thrombosis which precluded the planned nerve biopsy to elucidate the nerve pathology.