Hoffmann's sign

The Hoffmann's sign, named after the German neurologist, Johann Hoffmann (born 1857, Rheinhesse; died 1919, Heidelberg), is a finding elicited by a reflex test which verifies the presence or absence of problems in the corticospinal tract. It is also known as the finger flexor reflex.

The test involves tapping the nail or flicking the terminal phalanx of the third or fourth finger. A positive response is seen with flexion of the terminal phalanx of the thumb.

Relation to Babinski sign
Hoffmann's sign is often considered the upper limb equivalent of the Babinski's sign because it, like the Babinski sign, indicates upper motor neuron dysfunction. Mechanistically, it differs considerably from the Babinski or plantar reflex; Hoffmann's sign involves a monosynaptic reflex pathway in Rexed lamina IX of the spinal cord, normally fully inhibited by descending input. The pathways involved in the plantar reflex are more complicated, and different sorts of lesions may interrupt them. This fact has led some neurologists to reject strongly any analogies between the finger flexor reflex and the plantar response.