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Clinical exam · Nervous system

Hoffmann sign and clonus !

  • Sign

Two signs of brisk reflexes: the thumb flexes when the middle fingernail is flicked, and the foot beats on its own when stretched.

Updated 2026-11-01

See it in 3D: Spinal cord · Neck nerve roots · Achilles tendon

What it is

The Hoffmann sign is involuntary flexion of the thumb and index finger when the nail of the middle finger is flicked; it is the hand's version of hyperreflexia. Clonus is a rhythmic series of contractions that appears when a muscle is stretched suddenly and held, mostly at the ankle. Both mean the reflex arc is released by an upper motor neuron lesion.

The anatomy it tests

  • Hoffmann: the finger flexor reflex arc (C8 and T1 roots) released from corticospinal inhibition; a high cervical lesion brings it out.
  • Ankle clonus: the triceps surae stretch reflex (S1), which repeats unchecked when descending inhibition fails.
  • The lesion is in the corticospinal tract of the brain or spinal cord.

How to elicit it

  1. Hoffmann: the patient's hand relaxed, wrist slightly extended, middle finger held between the examiner's fingers.
  2. The examiner places a thumb on the middle fingernail and flicks it downwards quickly.
  3. Watch whether the thumb and index finger flex; repeat on the other hand.
  4. Ankle clonus: patient lying down, knee bent and supported by the examiner's hand.
  5. With the other hand, the examiner dorsiflexes the foot briskly and keeps the pressure on.
  6. Count the rhythmic beats and note whether they fade or are sustained.

What a positive result means

  • A positive Hoffmann and sustained clonus: an upper motor neuron lesion above the level of the reflex.
  • Causes: cervical spondylotic myelopathy, multiple sclerosis, stroke, spinal cord tumour or trauma, amyotrophic lateral sclerosis.
  • An asymmetric Hoffmann carries more weight than a symmetric one.
  • Its absence does not rule out myelopathy.

Usefulness and limits

  • The Hoffmann sign has limited sensitivity for cervical myelopathy; MRI confirms the lesion.
  • A tense foot or slow dorsiflexion can stop clonus from appearing.

Test yourself

Think of the answer, then tap the question to see it.

What is the Hoffmann sign?

Involuntary flexion of the thumb and index finger when the middle fingernail is flicked downwards; it shows hyperreflexia from an upper motor neuron lesion.

Which kind of clonus is abnormal?

Sustained clonus, which lasts as long as the stretch is held; a few beats that fade can be normal.

What does a bilateral Hoffmann with brisk leg reflexes suggest in an older adult with clumsy hands?

Cervical myelopathy, for example spondylotic, which is confirmed with MRI.

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See it in 3D

The structures of Durgical's 3D anatomy where it is found.

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Educational content on the clinical exam; it is learned and practised under supervision. It does not replace assessment by a health professional and is not for self-diagnosis.

Sources: How To Assess Reflexes (MSD Manual Professional Edition, 2024); 26.2 Physical Assessment - Clinical Nursing Skills (OpenStax, 2024); Overview of Spinal Cord Disorders (MSD Manual Professional Edition, 2024).

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