Spagnoli Anna Maria, Fino Pasquale, Fioramonti Paolo, Sanese Giuseppe, Scuderi Nicolo'
Ann Ital Chir. 2017;88:95-96.
Dear sir, one of the most common entrapment neuropathy syndromes in clinical practice is "Entrapment of median nerve in carpal tunnel" also called "Carpal tunnel syndrome (CTS)" (Aydin et al., 2007; Huisstede et al., 2010). This syndrome is caused by entrapment of the median nerve in the wrist (Preston and Shapiro, 2005) when the pressure increases in the carpal tunnel. A high division of the median nerve proximal to the carpal tunnel, also known as a bifid median nerve, is a rare anatomic variation that may be associated with CTS and with persistent median vessels (Lanz, 1977). This anatomic variation has an incidence of 0,8% to 2,3% in patients with CTS. Lanz (1977) has characterized this anatomic condition of the median nerve in the carpal tunnel. These anatomic variants have been classified into four groups: - Group 0: extraligamentous thenar branch (standard anatomy); - Group 1: variations of the course of the thenar branch; - Group 2: accessory branches at the distal portion of the carpal tunnel; - Group 3: divided or duplicated median nerve inside the carpal tunnel; - Group 4: accessory branches proximal to the carpal tunnel. During dissection of the wrist performed for the treatment of a CTS under local anesthesia, we found an anatomical variation of the median nerve that was divided in two branches inside the carpal tunnel (Group 3 of Lanz Classification) and in which its radial branch passed through its own compartment. The two parts of the nerve seems to be unequal in size (Fig. 1). Moreover the nerve passed in carpal tunnel associated with a median artery, so we classified this variation in the group 3b of Lanz Classification (Fig. 2). The persistence of median artery coexisting with a bifid median nerve has been widely reported in surgical literature (Lanz, 1977; Barbe et al., 2005). Before surgical intervention clinical evaluation of patient and electrophysiological examination showed no differences compared to a non bifid median nerve entrapment syndrome. In conclusion the bifid median nerve may facilitate compression of median nerve in the carpal tunnel because of its increased cross sectional area even if it has no electrophysiological or clinical differential diagnosis in case of CTS. The aim of this letter is aware the physicians in order to borne in mind the possible presence of a median nerve variation during dissection of carpal tunnel in order to avoid the damage of this non common anatomical structures.
尊敬的先生，临床实践中最常见的卡压性神经病综合征之一是“腕管综合征中的正中神经卡压”，也称为“腕管综合征（CTS）”（艾登等人，2007年；胡伊斯泰德等人，2010年）。该综合征是由于腕管内压力升高时正中神经在腕部受到卡压所致（普雷斯顿和夏皮罗，2005年）。正中神经在腕管近端高位分支，也称为双叉正中神经，是一种罕见的解剖变异，可能与腕管综合征以及永存正中血管有关（兰茨，1977年）。这种解剖变异在腕管综合征患者中的发生率为0.8%至2.3%。兰茨（1977年）对腕管内正中神经的这种解剖状况进行了描述。这些解剖变异已被分为四组：- 0组：韧带外鱼际支（标准解剖结构）；- 1组：鱼际支走行变异；- 2组：腕管远端的副支；- 3组：腕管内正中神经分支或重复；- 4组：腕管近端的副支。在局部麻醉下为治疗腕管综合征而进行腕部解剖时，我们发现正中神经的一种解剖变异，即其在腕管内分为两个分支（兰茨分类的3组），且其桡侧支穿过自己的间隙。神经的两部分似乎大小不等（图1）。此外，神经在腕管内走行时伴有一条正中动脉，因此我们将这种变异归类为兰茨分类的3b组（图2）。正中动脉与双叉正中神经并存的情况在外科文献中已有广泛报道（兰茨，1977年；巴贝等人，2005年）。在手术干预前，对患者的临床评估和电生理检查显示，与非双叉正中神经卡压综合征相比无差异。总之，双叉正中神经可能因其横截面积增加而便于腕管内正中神经受压，即使在腕管综合征病例中它没有电生理或临床鉴别诊断。这封信的目的是提醒医生，在进行腕管解剖时要记住正中神经变异的可能存在，以避免损伤这种不常见的解剖结构。
