Age / Sex : 32 / M

Chief complaint: Flexion limitation of right thumb for 1 month

1) What is your impression?

Two weeks later, you can see the final diagnosis with a brief discussion of this case.

(답안은 한 개만 보내주시기 바랍니다)

Courtesy: 추혜정 (Hye Jung Choo), 인제대학교 부산백병원 (Inje University Busan Paik Hospital)

Anterior interosseous nerve syndrome (Kiloh-Nevin syndrome)

Discussion

Anterior interosseous nerve

•       Pure motor nerve

•       Arises from the median nerve just distal to the pronator teres muscle

•       Supplies radial half of the flexor digitorum profundus, flexor pollicis longus, and the pronator quadratus muscles

Anterior interosseous nerve syndrome

•       Causes

•       Forearm or supracondylar fracture

•       Local pressure after sleeping on the affected arm

•       Poorly applied cast

•       Exercise and weight lifting, and viral neuritis

•       Others – lipoma, ganglion, accessory muscles, fibrotic band, vascular malformation

•       Clinical presentations

•       Pronation weakness

•       Pinching deformity (“Circle sign positive”) – weakness of thumb and index finger

•       Dull pain without sensory change

•       MRI findings

•       Edema (acute~subacute) and atrophy/fatty change (chronic) of the three innervated muscles

•       Edema in the pronator quadratus muscle - the most reliable sign (high sensitivity / low specificity)

References:

1.     Kim SJ, Hong SH, Jun WS, et al. MR imaging mapping of skeletal muscle denervation in entrapment and compressive neuropathies. Radiographics 2011;31:319-32.

2.     Andreisek G, Crook DW, Burg D, Marincek B, Weishaupt D. Peripheral neuropathies of the median, radial, and ulnar nerves: MR imaging features. Radiographics 2006;26:1267-87.