Which findings are typical of a corticospinal tract lesion on neurological examination?

• A. Contralateral weakness with UMN signs (spasticity, hyperreflexia, Babinski), possible mild atrophy.
• B. Ipsilateral weakness with fasciculations.
• C. Bilateral sensory loss without motor involvement.
• D. Pure cerebellar ataxia with intention tremor.

Answer: (A)

Corticospinal tract lesions produce upper motor neuron signs with weakness on the side opposite the lesion when the tract is above where it crosses in the medulla. On examination you’d expect contralateral weakness with spasticity, increased deep tendon reflexes (hyperreflexia), and a Babinski sign. Mild muscle wasting may occur from disuse, but the primary issue is UMN involvement rather than direct muscle or nerve degeneration.

This fits the described pattern: contralateral weakness plus UMN signs are typical of corticospinal tract damage above decussation. In contrast, fasciculations suggest lower motor neuron pathology, bilateral sensory loss without motor involvement points to sensory pathways, and pure cerebellar signs indicate a cerebellar problem rather than corticospinal tract involvement.