Cheiralgia Paresthetica - Handcuff Neuropathy- Wartenberg syndrome- wristwatch neuropathy

This neuropathy was first identified by Robert Wartenberg in a 1932 paper. Demographics- male:female ratio is 1:4, more common in women, age bracket is 20-70 years. 

Cheiralgia paraesthetica is a neuropathy of the hand generally caused by compression or trauma to the superficial branch of the radial nerve. The exact etiology is unknown, as it is unclear whether direct pressure by the constricting item is alone responsible, or whether edema associated with the constriction also contributes. Diagnostically it is often subsumed into compression neuropathy of the radial nerve as a whole (e.g. ICD-9 354.3), but studies and papers continue to use the older term to distinguish it from more extensive neuropathies originating in the forearm.

The most common cause is thought to be constriction of the wrist, as with a bracelet, wrist band, plaster cast or watchband (hence reference to "wristwatch neuropathy"). The patient may have history of trauma causing forearm fracture. It is especially associated with the use of handcuffs and is therefore commonly referred to as handcuff neuropathy. Other injuries or surgery in the wrist area can also lead to symptoms, including surgery for other syndromes such as de Quervain's.

The area affected is typically on the back or side of the hand at the base of the thumb, near the anatomical snuffbox, but may extend up the back of the thumb and index finger and across the back of the hand. 

The superficial sensory branch of the radial nerve arises from the bifurcation of the radial nerve in the proximal forear and travels deep to the brachioradialis in the forearm, emerging from between brachioradialis and ECRL 9cm proximal to radial styloid and bifurcates proximal to the wrist. The dorsal branch lies 1-3cm radial to Lister's tubercle and supplies 1st and 2nd web space. The palmar branch passes within 2cm of 1st dorsal compartment, directly over EPL and supplies dorsolateral thumb

Pathoanatomy- SRN compressed by scissoring action of  brachioradialis and ECRL tendons during forearm pronation, also by fascial bands at its exit site in the subcutaneous plane.

Symptoms include numbness, tingling, burning or pain (over dorsoradial hand). Symptom aggarvation is by motions involving repetitive wrist flexion and ulnar deviation. Since the nerve branch is sensory there is no motor impairment. 

Physical exam (provocative tests)-

Tinel's sign over the superficial sensory radial nerve (most common exam finding).

Finkelstein test increases symptoms in 96% of patients because of traction on the nerve

Investigations- X ray and NCV are of limited role.

Differential Diagnosis

It may be distinguished from de Quervain syndrome because it is not dependent on motion of the hand or fingers.

Lateral antebrachial cutaneous nerve (LACN) neuritis- positive Tinel's sign over LACN can be mistaken for positive Tinel's over superficial sensory radial nerve.

Intersection syndrome- may have dorsoradial forearm swelling, symptom exacerbation and "wet leather" crepitus on repeated wrist flexion/extension.

Symptoms commonly resolve on their own within several months when the constriction is removed- A superficial sensory cutaneous twig of the radial nerve is the branch most easily injured by constriction of the wrist. Its area of innervation can vary widely (see figure). Axonal regeneration of contused nerves proceeds at about l mm per day (or about an inch a month); thus recovery may require two months (measuring from site of injury in wrist to end of area of paresthesia). 

NSAIDs are commonly prescribed. 

In some cases surgical decompression is required(74% success after surgical decompression)- longitudinal incision volar to Tinel's sign,neurolysis and release of fascia between brachioradialis and ECRL.

The efficacy of cortisone and laser treatment is disputed. Permanent damage is possible.