A closer look at Saturday Night Palsy

I was reading James’ post on Saturday Night Palsy and thought about having a closer look.

Saturday night palsy occurs due to pressure on the radial nerve by keeping the arm over the handle of a chair or in some unusual position while sleeping, usually following heavy drinking. The palsy occurs due to injury to the radial nerve in the radial groove of the humerus (bone of the arm). The radial nerve, also known as the musculospiral nerve, lies in the radial groove in the posterior aspect of the humerus. The resulting paralysis from the injury is usually temporary, neuropraxia in type and resolves by itself but in some unfortunate cases, rhabdomyolysis may occur due to prolonged immobilization of the musculature as reported by Brian M. Devitt et al.  in a case report.

Radial Groove on humerus. Modified from Wikipedia

They reported a case of a 18 year male who suffered from Saturday Night Palsy after binge drinking and subsequently sleeping with his right arm wrapped around a suitcase. He woke up with paralysis of the right arm, severe pain and swelling. He also suffered from rhabdomyolysis. The course was not good. Total debridement of the biceps and brachialis muscle and partial debridement of brachioradialis muscle had to be done. All because of falling asleep while drunk!

Saturday night palsy is characterized by wrist drop. Injury to the radial nerve in the radial groove causes motor paralysis of the extensor muscles of the wrist, resulting in wrist drop. The patient is unable to lift up his wrist and it hangs down. Extensor muscles of all the joints of the thumb are paralyzed hence the patient is unable to extend his thumb. Extensor muscles of the fingers as a whole are not affected because the interossei muscles and lumbrical muscles which are responsible for extension remain unaffected as they are supplied by the ulnar nerve and the median and ulnar nerves respectively. The supinator and brachioradialis muscles are paralysed but supination movement of the forearm is possible by the intact biceps muscle.

The triceps muscle escapes paralysis although it is supplied by the radial nerve because nerve supply to all the three heads of the muscle arises before the radial nerve enters in the radial groove.

Sensory loss is present on the back of the hand, on the lateral side of the thumb and adjacent part of the palm. There is sensory loss on the medial side of the thumb and adjoining sides of the index, middle and lateral side of the ring finger. Anesthesia of the back of the fingers also occurs up to the proximal interphalangeal joint except over the thumb where it reaches up to the nail.

Saturday night palsy is usually managed conservatively with removal of compression, physical therapy and wrist splints.

Reference:

Devitt, B., Baker, J., Ahmed, M., Menzies, D., & Synnott, K. (2010). Saturday night palsy or Sunday morning hangover? A case report of alcohol-induced Crush Syndrome Archives of Orthopaedic and Trauma Surgery DOI: 10.1007/s00402-010-1098-z