What sign on exam indicates an upper motor neuron lesion in the upper limb?

• A. Positive Hoffmann sign indicates an upper motor neuron lesion in the upper limb.
• B. Loss of pinprick sensation indicates an upper motor neuron lesion.
• C. Hyporeflexia indicates an upper motor neuron lesion.
• D. Nystagmus indicates an upper motor neuron lesion.

Answer: (A)

Hoffmann sign reflects corticospinal tract dysfunction in the cervical region, an upper motor neuron (UMN) lesion affecting the upper limb. It’s elicited by flicking the distal phalanx of the middle finger; if the thumb and index finger briefly flex in response, that positive sign indicates UMN involvement in the upper limb.

Other signs listed don’t fit as UMN indicators for the upper limb. Loss of pinprick is a sensory pathway issue, not a motor pathway sign. Hyporeflexia points toward lower motor neuron involvement (or an acute stage), whereas UMN lesions typically produce hyperreflexia and increased tone. Nystagmus is an ocular movement abnormality related to brainstem or cerebellar disease, not a primary upper limb UMN sign.

So the positive Hoffmann sign is the best match for an upper motor neuron lesion in the upper limb.