Introduction
Herpes zoster infection cause motor weakness that affects the myotomal muscles corresponding to the dermatomal distribution of skin lesion. The most commonly affected nerve is the cranial nerves. Cervical and lumbosacral myotomal regions are equally likely to be affected. However, isolated anterior interosseous neuropathy following herpes zoster infection is a very rare and worldwide only one case (2nd finger spared) was reported in 1989. In this study, we report on one case of isolated complete anterior interosseous neuropathy following herpes zoster infection combined with chronic cervical C8 or T1 radiculopathy.
Case Presentation
A 54-year-old female noticed the weakness of left thumb and index finger within two 2weeks of having developed “shingles” causing vesicular lesions, redness and pain on forearm 2 years ago. Clinical testing at our neurophysiological lab revealed normal motor power in both upper extremities except that motor power of flexion in the interphalangeal (IP) joint of left thumb and distal interphalangeal (DIP) joint of left index finger was grade 0 by Medical Research Council scale, grade 3+ in pronation of left forearm with elbow fully extended and grade 4 in left first dorsal interosseous muscle. There was no sensory change on left forearm and hand.
Routine motor and sensory nerve conduction studies performed in median and ulnar nerves on both arm showed normal values, except that motor nerve conduction study for left median nerve recorded in pronator quadratus muscle by needle electrode showed no response.
Electromyography (EMG) was conducted on deltoid, biceps, triceps, flexor carpi radialis, abductor pollicis brevis, first dorsal interosseous, flexor digitorum profundus of 2nd, 3rd, 4th , and 5th finger, flexor pollicis longus, flexor digitorum superficialis, pronator quadratus and flexor carpi ulnaris in left upper extremity. Also, Left paraspinal muscles of C6, C7, and T1 level were included. There was no volitional activity in flexor pollicis longus, flexor digitorum profundus of 2nd finger and pronator quadratus innervated by anterior interosseous nerve. At rest, abnormal spontaneous activities were showed with mild to moderate level in left first dorsal interosseous, flexor digitorum profundus of 3rd, 4th, and 5th finger, flexor carpi ulnaris and paraspinal muscles of C7 and T1. And complex repetitive discharge was showed in flexor digitorum profundus of 4th, 5th finger. Finally, we concluded left complete anterior interosseous neuropathy at proximal forearm level combined with left chronic C8 or T1 radiculopathy.
Conclusion
We therefore present this patient as a possible case of complete anterior interosseous neuropathy following herpes zoster infection combined with chronic C8 or T1 radiculopathy.
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