Asymmetric Findings of Symmetric Symptoms: Bilateral Peripheral Polyneuropathy with a Congenitally Shorter Lower Extremity

Case Diagnosis: Length dependent, axonal, sensory and motor, diabetic peripheral polyneuropathy

Case Description or Program Description: A 69-year-old male with past medical history of non-ischemic cardiomyopathy, optic ischemic neuritis, diabetes mellitus, chronic kidney disease, hypothyroidism and left ACA stroke status post heart and renal transplant, presented for electrodiagnostic evaluation of his bilateral lower extremities for burning sensation in his feet. His foot burning has been worsening over the past year and is worse at night. Of note, he was born with a leg length discrepancy: his right leg is seven inches shorter than his left leg.

Setting: Outpatient General Rehabilitation

Assessment/Results: Electrodiagnostic studies showed evidence of length dependent axonal, sensory motor peripheral polyneuropathy. Left fibular and left tibial motor studies showed reduced amplitudes. Left sensory studies had no response. The right, significantly shorter lower extremity, did not show reduced amplitudes on motor studies and had intact sensory studies. Needle EMG showed mild chronic neuropathic changes distally bilaterally, with no sign of acute radiculopathy or plexopathy.

Discussion (relevance): With sensory studies being intact in the significantly shorter limb (right), absent in the longer limb (left) and reduced CMAP amplitudes isolated to the longer limb. A length dependent peripheral neuropathic process is likely, especially in the setting of diabetes mellitus and bilateral symptoms. It was unlikely that he had chronic left lumbosacral plexopathy, though it would be difficult to rule out.

Conclusions: Despite symmetrical symptoms, the significant leg length discrepancy illustrates the pathophysiology of a length dependent peripheral polyneuropathy and its severity objectively.