Phalen’s sign is present when tingling (paresthesia) is experienced in the distribution of the median nerve when the wrist is held in forced flexion (90º for 30-60 seconds; Phalen’s maneuver). Patients may volunteer that they experience such symptoms when carrying heavy items, such as shopping bags, that put the hand in a similar posture. Hyperextension of the wrist ("reverse Phalen’s maneuver") may also reproduce symptoms. These are signs of compression of the median nerve at the wrist (carpal tunnel syndrome). Like other provocative tests (e.g., Tinel’s sign), the sensitivity of Phalen’s sign for this diagnosis is not high compared to electrophysiological testing.
The pathophysiology of Phalen’s sign is probably the lower threshold of injured nerves to mechanical stimuli, as for Tinel’s sign and Lhermitte’s sign.
Heller L, Ring H, Costeff H, Solzi P. Evaluation of Tinel’s and Phalen’s signs in the diagnosis of the carpal tunnel syndrome. European Neurology 1986; 25: 40-42