Chronic ulnar nerve injury results in the classic claw-hand (intrinsic minus) deformity due to atrophy and contracture of the lumbrical and interosseus hand muscles. The deformity is formed by MCP joint hyperextension and flexion at the PIP and DIP joints of the 4th and 5th digits. There is wasting of the interosseous and hypothenar muscles, as well as the hypothenar eminence. The acutely injured patient is unable to abduct or adduct the digits. Chronic median nerve damage also results in the claw-hand deformity, but to the 2nd and 3rd digits with associated atrophy of the thenar. Acute and chronic damage to the proximal portion of the median nerve results in weakness of wrist flexion, forearm pronation, thumb apposition, and flexion of the 1st three digits.
Wrist drop is the most common symptom seen with radial nerve damage, occurring in situations of acute compression. It is frequently referred to as “Saturday night palsy” (as when a person falls asleep on an arm, or with the arm over a chair, resulting in temporary radial nerve neuropraxia).
Claw Hand. Claw-hand appearance resulting from median and ulnar nerve injury. Note metacarpophalangeal joint hyperextension. (Photo contributor: Daniel L. Savitt, MD.)
Management and Disposition
Treatment is aimed at recognizing the underlying cause, including laceration of the nerve, compression from swelling, or hematoma formation. Patients should be placed in a splint and discharged with referral.
Long-term nerve injury results in muscle wasting. Prior to any nerve damage, the thenar and hypothenar eminences have a full appearance. Initially, there is flattening of each eminence, followed by a concave or hollow appearance.
Sensory and two-point discrimination sense is lost in the distribution of any acutely or chronically injured nerve.
Claw Hand. Atrophy of the thenar and hypothenar eminences also occurs as a result of damage to the median and ulnar nerves, respectively. Note the concavity to the hypothenar eminence. (Photo contributor: Cathleen M. Vossler, MD.)