Hoffmann's Sign

Hoffmann's Sign (Joh. Hoffmann), an increase in mechanical and electrical excitability of sensory nerves, characteristic of tetany. Even slight pressure on a sensory nerve causes paresthesias radiating in the area of distribution of this nerve, whereas in normal conditions such pressure leads only to a local sensation. In healthy individuals, irritation of sensory nerves with galvanic current first leads to CZO (cathode-closure sensation), then to CZDO (c.-z. prolonged sensation) and finally to AZO (anode-closure sensation) and AZDO (a.-z. prolonged sensation). Only with further strengthening of the current does a radiating sensation occur instead of a local one. In tetany, however, a radiating sensation already arises when irritated by a relatively weak galvanic current.