Piso-hamate hiatus syndrome in a patient with Riche-Cannieu anastomosis

Abstract

Various nerve anastomoses and anatomic variants in the nervous system have been described. It is important to be familiar with these anastomoses because they can mimic several clinical conditions, possibly leading to misdiagnosis. We report the case of a patient who experienced progressive loss of strength in his left hand without sensory complaints. On neurological examination atrophy was seen in the thenar and first dorsal interosseous muscles of the left hand. Serial electrophysiological studies ruled out motor neuron disease. Electromyography and nerve conduction studies revealed a Riche-Cannieu anastomosis in the left hand. In combination with piso-hamate hiatus syndrome, this anastomosis explained the clinical condition of the patient. It is important to be aware of this anastomosis and this syndrome because it can mimic motor neuron disease.

Figure 1

(A) Atrophy of the first dorsal interosseous muscle (FDI) of the left hand. (B) Detail showing atrophy of the FDI of the left hand. (C) Atrophy of the abductor pollicis brevis muscle (APB) of the left hand. Note the extensive callus formation on both palms. (D) Detail showing atrophy of the APB of the left hand.

Figure 2

Motor nerve conduction study, recorded from the first dorsal interosseous muscle (FDI; A1–A4) and from the abductor digiti minimi muscle (ADM; B1–B4) on the left side. Stimulation of the ulnar nerve generates a compound muscle action potential (CMAP), recording from the FDI (A1–A2) and from the ADM (B1–B2). Stimulation of the median nerve generates a CMAP, recording from the FDI (A3–A4). Stimulation of the median nerve did not generate a CMAP, recording from the ADM (B3–B4).

Figure 3

Motor nerve conduction study recorded from the abductor pollicis brevis muscle in the left hand. Stimulation of the median nerve generates a compound muscle action potential (CMAP; C1–C2). Stimulation of the ulnar nerve also generates a CMAP (C3–C4).

Figure 4

(A) Schematic illustration of the piso-hamate ligament and Riche-Cannieu anastomosis in the left hand of our patient. (B) The red oval areas represent the atrophic muscles (the upper indicates the abductor pollicis brevis muscle, and the lower the first dorsal interosseous muscle). The blue oval area indicates the unaffected abductor digiti minimi muscle. The black star indicates the site of the lesion. H, hook of hamate; MN, median nerve; P, pisiforme; PL, piso-hamate ligament; RCA, Riche-Cannieu anastomosis; S, tuberosity of scaphoid; UN, ulnar nerve.