Saturday Night Palsy

Saturday night palsy is a transient compressive radial neuropathy at the spiral groove of the humerus, caused by prolonged pressure on the upper arm, classically from sleeping with the arm hanging over the back of a chair or bench or lying on the arm after heavy alcohol or sedative use, resulting in sudden wrist drop.

• It is a neurapraxia (conduction block with preserved axons) in most patients, so recovery is complete in the large majority within 6 to 12 weeks.
• Risk factors: alcohol intoxication, sedative or opioid use, deep sleep, anaesthesia, being thin, diabetes, repetitive arm positioning, and an inherited tendency to pressure palsies.
• Related conditions with the same mechanism: honeymoon palsy (partner's head on the arm), tourniquet palsy and crutch palsy.
• Recurrent palsies or palsies involving several nerves suggest hereditary neuropathy with pressure palsies or vasculitis.

• Wake with a weak, numb hand: wrist drop, finger drop and weak thumb extension, usually painless.
• Numbness over the dorsum of the hand in the first web space and radial side; sometimes tingling.
• Triceps strength and elbow extension are normal because the lesion is distal to the triceps branches; brachioradialis and wrist extensors are weak.
• Elbow flexion in mid-pronation is weak, with a reduced brachioradialis reflex.
• Tenderness or a groove at the posterolateral upper arm; no pain on neck movement.
• Check for bruising, fracture, intoxication or head injury, other nerves (ulnar, median), and signs of rhabdomyolysis if the patient was immobile for hours (muscle swelling, dark urine).

• Clinical, from the history of prolonged arm compression and the typical pattern of weakness with preserved triceps.
• Nerve conduction studies and EMG at 3 weeks if recovery is not clear, to confirm conduction block (good prognosis) or axonal loss (slower recovery).
• Creatine kinase, creatinine and urinalysis if prolonged immobilisation or intoxication raises the risk of rhabdomyolysis.
• Blood tests for a persisting or recurrent palsy: glucose and HbA1c, FBC, ESR, CRP, vitamin B12, TSH, blood lead level, and alcohol assessment.
• X-ray of the humerus if there was a fall or injury.
• Differentials: stroke (hand weakness with facial or speech signs), C7 radiculopathy, posterior interosseous palsy, extensor tendon rupture, cervical cord lesion, lead poisoning.

Reassure and explain

• The nerve is bruised rather than cut; about 90 percent recover fully within 6 to 12 weeks.

Protect the hand during recovery

• Wrist cock up splint holding the wrist at 20 to 30 degrees extension, worn during the day and removed for exercise, to prevent overstretching and contracture.
• Gentle passive range of motion of the wrist, fingers and thumb several times a day; progress to active strengthening as power returns.
• Avoid further pressure on the arm: no leaning on the arm, avoid sleeping in awkward positions and avoid alcohol or sedatives to the point of insensible sleep.

Medicines

• Pain is uncommon; use paracetamol 1 g up to four times daily (maximum 4 g) if needed.
• For neuropathic pain: amitriptyline 10 mg at night increasing to 50 mg, or gabapentin 300 mg at night increasing to 300 to 600 mg three times daily.
• Oral corticosteroids have no proven benefit and are not given.
• If alcohol misuse is present: advise abstinence or reduction, give thiamine 100 mg orally daily, and offer brief intervention and referral for alcohol use disorder.

Follow up and escalation

• Review at 2 weeks, 6 weeks, and 12 weeks with serial power grading.
• Arrange nerve conduction studies if there is no improvement by 4 to 6 weeks.
• Refer to a hand or peripheral nerve surgeon if there is no recovery by 3 months, or if rhabdomyolysis, fracture or other nerve injuries are present.
• Recurrent episodes: test for hereditary neuropathy with pressure palsies (PMP22 deletion), diabetes and vasculitis.