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.