The Oppenheim Test is used to detect which category of lesion?

• A. Lower motor neuron lesion
• B. Peripheral nerve entrapment
• C. Radiculopathy
• D. Upper motor neuron lesion

Answer: (D)

Oppenheim's sign is a test for upper motor neuron pathway dysfunction. When you rub a blunt object along the tibial crest from knee to ankle, a positive response is extension of the great toe (and sometimes spreading of the other toes). This extensor plantar response reflects loss of descending inhibitory control over the corticospinal tract, a hallmark of upper motor neuron lesions.

In contrast, lower motor neuron lesions tend to present with weakness, atrophy, fasciculations, and reduced reflexes, not a persistent extensor toe response. Peripheral nerve entrapment and radiculopathy produce localized sensory and motor signs tied to a nerve root or peripheral nerve, rather than the generalized UMN pattern. So the presence of a positive Oppenheim sign points to an upper motor neuron lesion.