Median Nerve Injury at the Elbow

Aka: Median Nerve Injury at the Elbow, Pronator Syndrome, Anterior Interosseous Nerve Entrapment

1. See Also
   1. Peripheral Nerve Injury
2. Definitions
   1. Pronator Syndrome
      1. Forearm compression of the Median Nerve between the two heads of the pronator teres Muscle
      2. Slow, insidious onset over the course of months to years with pronator overuse (hammering, backhand tennis swing)
   2. Anterior Interosseous Nerve Entrapment
      1. Affects Motor Nerve for deep ForearmMuscles (flexor pollicis longus, flexor digitorum profundus)
      2. Nerve injury results in weakness in making the "OK" sign
3. Differential Diagnosis
   1. Carpal Tunnel Syndrome
4. Symptoms
   1. Forearm volar discomfort and ache
   2. Provoked with elbow extension
   3. Paresthesias in the thumb, index and middle finger
5. Signs
   1. Sensory loss over thenar eminence (not present in Carpal Tunnel Syndrome)
   2. Tinel sign absent (contrast with Carpal Tunnel Syndrome)
   3. Phalen maneuver (contrast with Carpal Tunnel Syndrome)
   4. Normal forearm Sensation
   5. Sensation in fingers may also be normal
   6. Pronator Syndrome
      1. Pronation against resistance from neutral elbow position to elbow extension
      2. Positive test if pain and Paresthesias occur with maneuver
   7. Anterior Interosseous Nerve Entrapment
      1. Weakness in maintaining the "OK" sign against resistance
6. Management
   1. Modify activity avoiding provocative measures
   2. Consider steroid injection (Pronator Syndrome)
   3. Consider brief Splinting with elbow at 90 degrees (risk of loss of elbow range of motion)
   4. Surgery indications
      1. Space occupying lesion
      2. No improvement with 3-4 months of conservative therapy
7. Course
   1. Anticipate 3-6 month course with therapy
8. References
   1. Neal (2010) Am Fam Physician 81(2): 147-55 [PubMed]