Atrophy was prominent in the first dorsal interosseal muscle and less obvious in the
hypothenar muscles (Figure-1).
Inclusion criteria required a diagnosis of CubTS according to guidelines provided by the American Association of Neuromuscular and Electrodiagnostic Medicine:[sup][4] (1) symptoms of impairment of ulnar nerve, such as paresthesia of the digitus annularis and digitus minimus, hand clumsiness, atrophy of
hypothenar muscles, weakness of the muscles dominated by the ulnar nerve, pain, or numbness in ulnar nerve dominated area, positive Froment's sign, positive Wartenberg's sign, and so on; (2) routine motor NCS results suggested CubTS; (3) informed consent signed; and (4) age between 18 and 85 years old.
voluntary muscle testing showed Grade 0 power in the thenar and
hypothenar muscles bilaterally.
In another case of ulnar nerve lesion, one could not find any denervation in
hypothenar muscles.
On motor examination, there was wasting of thenar and
hypothenar muscles of the right side with normal left sided examination.
The deep ulnar nerve is responsible for motor control of intrinsic hand function through innervation of the dorsal and palmar interossei, the lumbricals of fourth and fifth digits, the
hypothenar muscles (abductor, flexor and opponens digiti minimi), adductor pollicis muscle and the deep head of flexor pollicis brevis.
Atrophy of the first dorsal interosseous and
hypothenar muscles is common.
The deep branch curves around the hook of the hamate and turns radially across the interossei, supplying the
hypothenar muscles, the ulnar two lumbricals, all the interossei, and the adductor pollicis.
Hypothenar muscles include the abductor digiti minimi (abducts the 5th finger), flexor digiti minimi (flexes the little finger) and oppenens digiti minimi (opposes the fifth digit).
In the distal canal, the ulnar nerve bifurcates into a superficial sensory branch and a deep motor branch, which supplies the
hypothenar muscles and then passes across the palm, distributing to other intrinsic hand muscles.
For clinical work, stimulation was applied to the median or ulnar nerve at the wrist by a constant current pulse and the EMG was recorded from the thenar or
hypothenar muscles in the hand.
He could move his upper extremities with full strength, except for minimal weakness in the
hypothenar muscles.
