What's involved:

Radial Nerve

Location:

	Most frequently at the Spiral Groove of the humerus
	Could be at the Axilla (Saturday Night palsy)
	Or in the Forearm (Posterior Interosseous Syndrome)

Common symptoms:

	Wrist drop, Patient unable to extend wrist or fingers up
	Almost always unilateral
	No associated pain
	Occasional forearm/hand/thumb numbness
	Symptoms always present no night/day preference

Onset:

	Sudden
	Usually happens upon waking up one morning
	Or, after a "Saturday Night" at the bar falling asleep with arm hanging over back of chair
	Or following prolonged sitting in a position with arm leaning against sharp object
	Or following misplaced intramuscular injection in the vicinity of the Radial nerve

Risk factors:

	No gender preference
	Diabetes or family history of Diabetes, Alcoholism
	Leaning on arms/axilla, sleeping in wrong position or with somebody leaning on arm, trauma

Exam:

	When first seen, weakness but no atrophy
	Wrist drop with inability to extend wrist, fingers
	Always check the three following muscles: Triceps: Ask subject to extend elbow Brachio-Radialis: Ask subject, with thumb pointing to ceiling, to flex forearm. Make sure the belly of the Brachio-Radialis is easily visible (compare to healthy side) Extensor Indicis Proprius: With hand flat on bed, ask subject to raise index finger up
	Occasional numbness/decreased sensation over dorsum of hand/thumb area
	Difficulty spreading fingers (pseudo-ulnar interosseii weakness)
	Pseudo-Ulnar weakness correctible when wrist held level with forearm by examiner
	Positive Tinel sign (tingling upon tapping nerve) at the humeral Spiral Groove when lesion at that location

Localization:

Three possible locations determined by exam of Triceps, Brachio-Radialis and Extensor Indicis Proprius Axilla: Triceps, Brachio-Radialis and Extensor Indicis Proprius all weak, normal to decreased sensation over dorsum hand/thumb area Humeral Spiral Groove: Triceps strength is normal, weak Brachio-Radialis (can barely see belly of muscle) and weak Extensor Indicis Proprius, normal to decreased sensation over dorsum hand/thumb area  Forearm (Posterior Interosseous Syndrome): Triceps and Brachio-Radialis normal, Extensor Indicis Proprius weak, normal sensation over dorsum hand/thumb area

EMG:

	Very Good for localization (Axilla, Spiral Groove, Forearm)
	Very Good for Prognostic value: In pure myelin lesions (conduction block), recovery may occur after three weeks to a month In moderate/severe axonal lesions, recovery may take from 6 months to a year In mixed lesions, somewhere in between
	Findings: Slowing, drop in Extensor Indicis Proprius amplitude across compression area in myelin lesions Diffuse drop in Extensor Indicis Proprius amplitude with or without slowing in axonal lesions Mixture of above in mixed lesions Radial sensory spared only in forearm (posterior interosseous) lesions

Recommendations:

	Symptomatic treatment
	Stop/decrease cause
	Wrist/finger splint to keep fingers extended in moderate to severe axonal lesions
	Passive wrist, fingers Range of Motion to maintain mobility

What else could it be:

	If other nerves involved, could be Brachial Plexus lesion (do not make the mistake of diagnosing a superimposed Ulnar neuropathy because the interosseii "appear" weak)
	Bilateral Radial palsies, always look for Lead poisoning
	Very rarely, Myotonic Dystrophy can cause weak, wasted forearms and bilateral wrist drop