Case 5: 61 year old man with progressive numbness and paresthesia in the feet and hands

61 year old non-diabetic African American male with significant PMH of congestive heart failure (CHF) presented with 3 years of progressive numbness on the  bilateral plantar surfaces of the feet as well the fingertips. Two years before he was diagnosed with bilateral carpal tunnel syndrome and underwent decompression surgery on bilateral wrists, which resulted in only temporary relief of his symptoms. Family history is significant for sudden cardiac death in a sister at 35 years old and another sister with CHF at age 60.

Neurological exam showed that the mental status and cranial nerves were normal,  there was weakness and atrophy of thenar and hypothenar muscles, and of the distal foot muscles, but the more proximal limb muscles had normal bulk and strength.  DTRs were absent at the ankles. Sensory exam showed diminished pinprick and temperature up to the wrists and ankles, and normal vibratory and proprioception. Click here for nerve conduction study results. What is the differential diagnosis and further diagnostic steps? (click here)