Tinel’s Sign (Hoffmann-Tinel Sign)
Tinel’s sign (Hoffmann-Tinel sign) is present when tingling (paresthesia) is experienced when tapping lightly with a finger or a tendon hammer over a compressed or regenerating peripheral nerve. The tingling (Tinel’s "sign of formication") is present in the cutaneous distribution of the damaged nerve ("peripheral reference"). Although originally described in the context of peripheral nerve regeneration after injury, Tinel’s sign may also be helpful in diagnosing focal entrapment neuropathy, such as carpal tunnel syndrome. However, it is a "soft" sign; like other provocative tests for carpal tunnel syndrome (e.g., Phalen’s sign) it is not as reliable for diagnostic purposes as electromyography (EMG). One study found a specificity of 59-77%, and sensitivity of 60-67%.
A "motor Tinel sign" has been described, consisting of motor EMG activity and jerking of muscles evoked by manipulation of an entrapped nerve trunk.
The neurophysiological basis of Tinel’s sign is presumed to be the lower threshold of regenerating or injured (demyelinated) nerves to mechanical stimuli, which permits ectopic generation of orthodromic action potentials, as in 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
Montagna P. Motor Tinel sign: a new localizing sign in entrapment neuropathy. Muscle Nerve 1994; 17: 1493-1494
Pearce JMS. Hoffmann and Tinel’s sign of formication. In: Pearce JMS. Fragments of neurological history. London: Imperial College Press, 2003: 375-377