A 45-year-old woman is evaluated for numbness and painful tingling of the right hand. The symptoms began 2 months ago and are especially prominent after she plays tennis. On examination, there is diminished sensation in the lateral palm, thenar eminence, and palmar aspect of the first 3½ digits of the right hand. This patient most likely has an injury involving a nerve that courses between which of the following structures?

Question

A 45-year-old woman is evaluated for numbness and painful tingling of the right hand.  The symptoms began 2 months ago and are especially prominent after she plays tennis.  On examination, there is diminished sensation in the lateral palm, thenar eminence, and palmar aspect of the first 3½ digits of the right hand.  This patient most likely has an injury involving a nerve that courses between which of the following structures?

Quizplus · Accepted Answer

11ec160b_35a0_ba9b_9249_e1c70e122fd0_MD0001_00 This patient has diminished sensation that involves the entire sensory distribution of the median nerve and is exacerbated by repetitive, forceful pronation (eg, tennis). This presentation is most consistent with compression of the median nerve as it passes between the two heads of the pronator teres (ie, pronator teres syndrome). The median nerve arises from the medial and lateral cords of the brachial plexus and travels with the brachial artery in the medial bicipital groove (ie, longitudinal hollow between the biceps brachii and triceps brachii muscles) of the upper arm. In the forearm, the median nerve courses between the humeral and ulnar heads of the pronator teres muscle and between the flexor digitorum superficialis and flexor digitorum profundus muscles before entering the hand through the carpal tunnel. Median nerve compression at the carpal tunnel, which is distal to the takeoff of the palmar branch, typically impairs sensation to the palmar aspects of the first 3½ digits. In contrast, compression by the pronator teres occurs proximal to the takeoff of the palmar branch; therefore, sensation is impaired not only to the palmar aspect of the first 3½ digits but also to the entire lateral palm and thenar eminence (ie, sensory distribution of the palmar branch). (Choice A) The musculocutaneous nerve courses between the biceps brachii and coracobrachialis muscles in the upper arm. Injury (eg, trauma, shoulder dislocation) can cause sensory loss over the lateral forearm. (Choices B and D) The ulnar nerve courses between the olecranon and the medial epicondyle of the humerus (ie, the cubital tunnel) before passing between the flexor carpi ulnaris and flexor digitorum profundus muscles in the forearm. Ulnar nerve injury at the elbow (eg, compression, trauma) can cause sensory loss in the dorsomedial hand, medial palm, and medial 1½ digits. (Choice E) The deep branch of the radial nerve (ie, posterior interosseous nerve) courses between the supinator muscle and the head of the radius in the upper forearm. Injury (eg, humeral fracture, compression) can cause sensory loss in the posterior forearm, dorsolateral hand, and dorsal thumb. Educational objective: In the forearm, the median nerve courses between the humeral and ulnar heads of the pronator teres muscle and between the flexor digitorum superficialis and flexor digitorum profundus muscles. Compression prior to the takeoff of the palmar branch (eg, between the heads of the pronator teres) results in sensory loss over the lateral palm and palmar aspects of the first 3½ digits. __________ References: Median nerve anatomy and entrapment syndromes: a review. (http://www.ncbi.nlm.nih.gov/pubmed/6756339) Ulnar tunnel syndrome, radial tunnel syndrome, anterior interosseous nerve syndrome, and pronator syndrome. (http://www.ncbi.nlm.nih.gov/pubmed/27902538)

A 45-Year-Old Woman Is Evaluated for Numbness and Painful Tingling