disassociated wasting of the intrinsic hand muscles, with some or all of those occupying the lateral (radial) aspect of the hand, i.e., the first dorsal interosseous and thenar eminences being much more severely affected than those occupying the medial (ulnar) aspect, i.e., the hypothenar eminence. If deep branch ulnar nerve lesions in the hand located distally to the motor fibers supplying the hypothenar muscles are excluded, this is nearly always a sign of cervical anterior horn cell disease involving the C8 and T1 segments.
