Median Nerve Entrapment Clinical Presentation

Updated: Mar 15, 2022
  • Author: Bardia Amirlak, MD; Chief Editor: Harris Gellman, MD  more...
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History and Physical Examination

Carpal tunnel syndrome

Symptoms of carpal tunnel syndrome (CTS) include paresthesia or numbness in the median nerve distribution of the hand (the thumb, the index finger, the middle finger, and the radial side of the ring finger). Patients may describe aching in the thenar eminence and, with severe nerve compression, weakness and atrophy of the abductor pollicis brevis (APB) and opponens pollicis. [52, 53] This leads to weakness and clumsiness of hand movements and, frequently, complaints of dropping things.

There is increased symptomatology upon active hand use, especially grasping, and the patient may have numbness in the fingers and pain in the wrist or distal forearm upon waking. Nocturnal symptoms are often alleviated by the patient's shaking of the hand or rubbing. Associated conditions and occupational and sports activities should be investigated.

Wasting of the thenar eminence is an advanced sign of CTS and usually responds poorly to surgical decompression.

Presence of the Tinel sign at the wrist—distal lancinating paresthesia in the distribution of the median nerve on light percussion—suggests CTS. It is also useful to clinically follow nerve regeneration after injury. [54, 55, 56, 57] An equally important clinical sign that is probably more specific to CTS is the Phalen sign, in which the symptoms of CTS are reproduced upon wrist flexion. [58]

In a prospective study of 1039 patients with a neurophysiologic diagnosis of CTS, Nora et al found that the most characteristic manifestation of the syndrome was paresthesia in the median nerve distribution, frequently extending to the whole hand. [59] Pain was very common but less specific, and weakness was rare. Tinel and Phalen signs were observed in 34.2% and 56.3% of the hands, respectively.

Pronator syndrome

Patients with pronator syndrome (pronator teres syndrome [PTS]) typically present with aching discomfort in the forearm, local pain over the median nerve distribution distal to the elbow, weakness in the hand, and numbness in the thumb and index finger, especially after repeated and prolonged stress. [60, 2]

Development of paresthesia in the hand after 30 seconds or less of manual compression of the median nerve at or near the pronator teres (pronator compression test) can aid in clinical diagnosis. [61, 62]

Provocation maneuvers may also indicate the possible site of entrapment in PTS. [63, 11] Reproduction of symptoms upon flexion of the elbow against resistance between 120° and 135° suggests compression of the median nerve by the ligament of Struthers. Compression by bicipital aponeurosis may be diagnosed on the basis of pain upon elbow flexion against resistance when the arm is pronated.

Compression by the pronator teres is suggested by symptoms upon resisted pronation of the forearm with wrist flexion (to relax the flexor digitorum superficialis [FDS]) or direct pressure on the leading edge of the pronator while the forearm is in maximum supination with the wrist in a neutral position. Compression may be at the FDS proximal arch if symptoms are aggravated by resisted flexion of the FDS to the middle finger.

Anterior interosseus nerve syndrome

Typical symptoms of anterior interosseus nerve (AIN) syndrome (AINS) include inability to flex the terminal phalanges of the thumb and index finger (eg, loss of pinch and fine motor skills such as writing) and inability to pronate the forearm when the elbow is flexed. [64, 3] This results from motor loss of the flexor pollicis longus (FPL), the flexor digitorum profundus (FDP) of the index finger, and the pronator quadratus. [65] Absence of sensory symptoms is typical; the AIN is a pure motor nerve.

AINS should be differentiated from flexor tendon rupture or other tendon pathologies. This can be accomplished by observing passive flexion of the interphalangeal (IP) joints in AINS when the wrist and metacarpophalangeal (MCP) joints are hyperflexed.

Parsonage-Turner syndrome presents with symptoms that are similar to those observed in AINS. [66] It is preceded by severe pain for weeks. Treatment consists of high-dose corticosteroids and acyclovir. Decompression typically does not help.