Poster 65: An Unusual Case of Ulnar Neuropathy with Posterior Interosseus Nerve Involvement: A Case Report

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Setting: Major metropolitan rehabilitation hospital electrodiagnostic laboratory. Patient: A 53-year-old white man presented with left forth and fifth digit pain and numbness since coronary artery bypass graft surgery 9 weeks earlier, with associated difficulty writing and picking up objects. Case Description: His medical history was significant for hypertension, hypercholesterolemia, and chronic renal insufficiency. Past surgical history was significant for coronary artery bypass graft surgery without acute medical complications, tonsillectomy, and descending thoracic aorta stent graft for sinus of valsalva aneurysm and dissection. Examination revealed atrophy of the left hand ulnar intrinsic muscles, positive left Froment's sign, positive Tinel sign at the left ulnar elbow and wrist, and decreased sensation to light touch in the ulnar distribution of the left hand. There was normative muscle strength in the upper limb except for weakness of the ulnar and posterior interosseus innervated muscles. Electrodiagnostic evaluation yielded diagnosis of acute left ulnar and posterior interosseus neuropathies, with both axonal loss and neurapraxic block at multiple sites of pathology. Assessment/Results: The ulnar and posterior interosseus neuropathies were likely due to localized compression of the forearm during the coronary artery bypass graft surgery by tourniquet injuries. There was also evidence for entrapment neuropathy more proximally in the left upper limb. We considered a possible role of cervical radiculopathy, brachial plexopathy, and lower trunk lesion but the likeliest diagnosis was compression injury to the nerves at the spiral groove, cubital area, and in the forearm. Further developments will be discussed. Conclusions: This is the first reported case, to our knowledge, of ulnar neuropathy with concomitant posterior interosseus neuropathy. This is an unusual case of ulnar and posterior interosseus nerve injury after coronary artery bypass graft surgery. Paresthesias and weakness in complicated nerve injury cases of multiple peripheral nerves can be a diagnostic dilemma. Physiatrists must have knowledge of electrodiagnosis, pathophysiology, and anatomy to evaluate such lesions.