In which nerve compression causes Saturday night palsy?

NIMHANS Nursing Officer - 2021

Applied Anatomy

Easy

Appeared in: NIMHANS Nursing Officer - 2021

Explanation

Saturday night palsy is the common term for a radial nerve injury caused by prolonged compression.
The compression typically occurs in the spiral groove of the humerus, where the nerve is superficial.
The hallmark sign of this condition is 'wrist drop,' which is the inability to extend the wrist and fingers due to paralysis of the extensor muscles innervated by the radial nerve.
Other causes include pressure from crutches (crutch paralysis) or fractures of the humerus shaft.

Option B: Ulnar nerve compression typically occurs at the elbow ('funny bone') and leads to a 'claw hand' deformity, affecting the 4th and 5th fingers, along with sensory loss in that distribution. It does not cause wrist drop.
Option C: Axillary nerve compression or injury, often due to a shoulder dislocation or fracture of the surgical neck of the humerus, results in weakness of the deltoid muscle (difficulty abducting the arm) and sensory loss over the 'regimental badge' area on the shoulder.
Option D: Median nerve compression most commonly occurs at the wrist (Carpal Tunnel Syndrome) and leads to 'Ape Hand' deformity (wasting of the thenar eminence and inability to abduct the thumb) and the 'Hand of Benediction' sign when attempting to make a fist. It affects flexion and sensation in the lateral fingers.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Etiology of Saturday Night Palsy as background academic context rather than a clinical decision trigger.
Nurses must be vigilant in preventing pressure injuries in sedated, intoxicated, or immobilized patients by ensuring proper positioning and frequent turning, paying special attention to the arms.
Assessment for suspected radial nerve palsy includes checking for wrist drop by asking the patient to extend their wrist and fingers against gravity. Sensory testing on the dorsum of the hand is also crucial.
What if? If a patient with a humeral shaft fracture suddenly develops wrist drop, it is a neurological emergency. This is called Holstein-Lewis fracture, and the nurse must immediately notify the physician as it may indicate nerve entrapment requiring urgent intervention.

How to Approach the Question

First, identify the key term in the question: 'Saturday night palsy'. This is an eponym, a name for a medical condition.
Recall or deduce the underlying pathology associated with this eponym. 'Saturday night palsy' specifically refers to an injury of the radial nerve.
Analyze the mechanism described by the name: it implies prolonged pressure on the arm, often from sleeping in an awkward position, which compresses the nerve.
Evaluate the options provided. Match the identified nerve (Radial nerve) with the corresponding option.
Mentally differentiate the signs of other nerve palsies (Ulnar, Median, Axillary) to confirm your choice and rule out the distractors. For example, associate 'wrist drop' with radial, 'claw hand' with ulnar, and 'ape hand' with median nerve.

Concept Tested & Keywords

QN7x7bippQiCOLcg5rz2IY

E6 Anatomy MindMaps BDChaurasia V1 10e p. 7-9

E6 Anatomy Grays 43e Vol 2 Part 2 p. 114-116

E6 Anatomy BDChaurasia V1 10e p. 100-102