Risk Assessment of Injury to Palmar Cutaneous Branch of the Median Nerve Using High-Resolution Ultrasound

OBJECTIVE: To evaluate the relationship between the palmar cutaneous branch of median nerve (PCBMN) and surrounding anatomical structures by using high-resolution ultrasound (HRUS) to assess the risk of PCBMN injury. METHODS: The PCBMN course and the characteristics of bilateral distal forearms and wrists of 30 healthy volunteers were identified. The distance between PCBMN and other anatomical structures at three different levels along its course were measured using HRUS. Moreover, the depth of PCBMN from skin and its cross-sectional area (CSA) were measured. RESULTS: HRUS showed the PCBMN in all subjects. PCBMN branched off from the radial aspect of the median nerve (MN) at 4.69±0.89 cm proximal to the bistyloid line (BSL) and extended radially toward the flexor carpi radialis (FCR) tendon. PCBMN was within the ulnar edge of FCR tendon sheath, and became more superficial and perforated the antebrachial fascia between the FCR tendon laterally and the palmaris longus (PL) tendon medially. PCBMN was located at 4.08±0.72 mm on the ulnar aspect of the FCR tendon and 4.78±0.36 mm radially on the PL tendon at BSL. At the distal wrist crease level, the PCBMN was located at 5.68±0.58 mm on the ulnar side of the FCR tendon. The PCBMN depth from skin at BSL and its branching point was 1.92±0.41 and 7.95±0.79 mm, respectively. The PCBMN CSA was 0.26±0.15 mm² at BSL. CONCLUSION: HRUS can be used to identify PCBMN and its relationship with other anatomical structures. Our data can be used to predict PCBMN location, and prevent complications associated with invasive procedures involving the wrist.

Bilateral triad of persistent median artery, a bifid median nerve and high origin of its palmar cutaneous branch: a case report and clinical implications / Tríada bilateral correspondiente a arteria mediana persistente, nervio mediano bífido y origen alto de la rama cutánea palmar: reporte de caso e implicancias clínicas

We report the association of a persistent median artery, a bifid median nerve with a rare very high origin palmar cutaneous branch, presenting bilaterally in the upper limb of a 75-year-old female cadaver. The persistent median nerve with a bifid median nerve has been reported in patients presenting with carpal tunnel syndrome. Reports of this neurovascular anomaly occurring in association with a high origin palmar cutaneous branch however, are few. This subset of patients is at risk of inadvertent nerve transection during forearm and wrist surgery. Pre-operative magnetic resonance imaging (MRI) and high resolution sonography (HRS) can be used to screen this triad. MRI can reveal if the patient's disability is associated with a persistent median nerve, a bifid median nerve. HRS can help identify a palmar cutaneous branch of the median nerve that arises in an unexpected high forearm location. Such knowledge will help surgeons in selecting the most appropriate surgical procedure, and help avoid inadvertent injury to cutaneous nerves arising in unexpected locations. In patients presenting with a bilateral carpal tunnel syndrome, hand surgeons should consider very high on the list of differential diagnosis a persistent median artery with a concomitant bifid median nerve, with a high suspicion of a possible bilateral occurrence of a bilaterally high arising palmar cutaneous branch of the median nerve.

En este estudio se presenta la disposición bilateral de una arteria mediana persistente, un nervio mediano bífido con ramo cutáneo palmar de origen alto, en los miembros superiores de un cadáver de sexo femenino de 75 años de edad. Clínicamente se asocia la presencia del nervio mediano bífido en pacientes con síndrome de túnel carpiano. Sin embargo, son escasos los informes de esta anomalía neurovascular en asociación con un ramo cutáneo palmar del nervio mediano de origen alto. Este subconjunto de pacientes podría sufrir de transección del nervio durante la cirugía de antebrazo y de la muñeca. Se recomienda utilizar la imagen preoperatoria de resonancia magnética (RM) y sonografía de alta resolución (SAR) para detectar esta tríada. La RM puede revelar si la discapacidad del paciente se asocia con un nervio mediano persistente, un nervio mediano bífido. SAR puede ayudar a identificar un ramo cutáneo palmar del nervio mediano que surge en una situación alta del antebrazo en forma inesperada. Tal conocimiento ayudará a los cirujanos en la selección del procedimiento quirúrgico más apropiado, y a evitar una lesión inadvertida de nervios cutáneos que surgen en lugares inesperados. En los pacientes que presentan un síndrome del túnel carpiano bilateral, los cirujanos de mano deben considerar como prioridad en la lista de diagnóstico diferencial una arteria mediana persistente con un nervio mediano bífido concomitante, con una alta sospecha de una posible aparición bilateral de un ramo cutáneo palmar bilateral alto que surja del nervio mediano.

The Influence of Stimulation Site on the Conduction Study of Palmar Cutaneous Branch of Median Nerve

OBJECTIVE: Nerve conduction study of palmar cutaneous branch of median nerve is infrequently evaluated in spite of its importance because of perceived technical difficulties. This study reports the different nerve conduction responses of palmar cutaneous branch of median nerve by change of stimulation site. METHOD: Conduction study of palmar cutaneous branch of median nerve was performed in 42 normal individuals stimulated at the site of 7 cm proximal to the recording electrode. Results were compared to those of stimulated at the site of 10 cm proximal to the recording electrode with t-test by SPSS 7.5. RESULTS: Values of conduction study stimulated at the site of 10 cm proximal to the recording electrode were 2.37+/-0.48 msec (mean+/-SD) for peak latency, 15.67+/-8.31 micro V for amplitude and 34.52+/-5.97 mA for supramaximal intensity.Those values stimulated at 7 cm proximal were 1.72+/-0.33 msec for peak latency, 24.48+/-11.41 micro V for amplitude and 12.82+/-2.18 mA for supramaximal intensity. Amplitude stimulated at the site of 7 cm was significantly larger than that stimulated at the site of 10 cm (p<0.01). Supramaximal intensity stimulated at the site of 7 cm was significantly smaller than that stimulated at 10 cm (p<0.01). CONCLUSION: The different stimulation site influences on the nerve conduction study of the palmar cutaneous branch of median nerve. Conduction study of palmar cutaneous branch of median nerve with stimulation at 7 cm proximal is a more reliable and convenient method compared to 10cm proximal in respect of larger amplitude and smaller supramaximal intensity.