THE CUTANEOUS INNERVATION OF THE PALM - AN ANATOMIC STUDY OF THE ULNAR AND MEDIAN NERVES

Twenty-five fresh-frozen cadaveric hands without obvious deformity wer e dissected using 3.5x loupe magnification. Median and ulnar nerves we re identified in the proximal forearm and dissected distally to the mi dpalm. Cutaneous branches of median and ulnar nerves were described re lative to an incision for carpal tunnel release. The palmar cutaneous branch of the median nerve was present in all 25 specimens. In a singl e specimen, the palmar cutaneous branch of the median nerve was isolat ed as it crossed the incision, and in another two specimens, the termi nal branches of the nerve were identified at the margin of the incisio n. In 4 hands, a classic palmar cutaneous branch of the ulnar nerve wa s found an average of 4.9 cm proximal to the pisiform. In 10 specimens , a nerve of Henle arose an average of 14.0 cm proximal to the pisifor m and traveled with the ulnar neurovascular bundle to the wrist flexio n crease. In 24 specimens, at least one - usually multiple - transvers e palmar cutaneous branch was identified originating an average of 3 m m distal to the pisiform within Guyon's canal. The origin and destinat ion of these nerves was highly variable. In 16 specimens, an incision in the axis of the ring finger would likely have encountered at least one branch of the ulnar-based cutaneous innervation to the palm. Cutan eous branches of the ulnar nerve would be expected to cross the line o f dissection frequently during open carpal tunnel release. Decreased l evels of discomfort in patients undergoing endoscopic and subcutaneous types of carpal tunnel release may be in part due to the preservation of the crossing cutaneous nerves with these procedures.