The cross-sectional area of the median nerve at the inlet of the carpal tunnel (at the level of the
pisiform bone) is the most sensitive and specific ultrasound finding in patients with CTS1.
The US criteria (7) we use for diagnosing the median nerve compression at the carpal tunnel include increased cross-sectional area proximally to the compression site, usually at the level of the proximal
pisiform bone (Normal cross-sectional area of the median nerve is not greater than 9 mm2) nerve flattening (in the transverse section the nerve is at least 3 times wider than it is thickness) and lower echogenicity.
The forearm being held in neutral position, the perforator was marked with the aid of a hand-held Doppler, one cm proximal to the metacarpophalangeal (MCP) joint, over an axial line drawn between the ulnar margin of the
pisiform bone and the ulnar aspect of the fifth metacarp's basis [Figure 1].
Plain radiographs of the left wrist revealed a 1.3 x 0.7 cm area of calcific deposit about the volar aspect of the
pisiform bone (Figure 1).
Examination revealed an abrasion over the hypothenar eminence and point tenderness over the volar aspect of the right wrist, overlying the
pisiform bone. No crepitus was noted.
The anomalous branch, known as Kaplan anastomosis, was originally described by Kaplan in 1963, as a communication which was originated from the DBUN, crossing from the posterior to the anterior side, close to the
pisiform bone, anastomosing with the superficial branch of the ulnar nerve (SBUN), close to the ulnar canal (Kaplan, 1963).
between the fifth metacarpophalangeal joint and the
pisiform bone. The compound muscle action potentials (CMAPs) were evoked by the electrical stimulation (0.1 ms duration, constant current pulse) of the ulnar nerve, starting with a minimum and progressing to the maximum intensity of the stimuli.
To measure the internal carpal tunnel dimensions (Figure 1), the radio-ulnar diameter and the dorsopalmar diameter of the carpal tunnel were measured at defined levels between the scaphoid and the
pisiform bone, the flexor retinaculum above the median nerve, and the lunate bone, respectively.
pisiform bone - a small wrist bone that articulates only with the triquetral