NBME Neuroscience 3

Question 1

A patient loses fine touch, vibration, and proprioception below the level of a thoracic spinal cord lesion, bilaterally. Which tract is most likely damaged?

Accepted Answer

Dorsal columns (posterior funiculus)

Answer

The dorsal columns (fasciculus gracilis and cuneatus) carry ipsilateral fine touch, vibration, and proprioception; bilateral loss indicates bilateral dorsal column damage.

Question 2

A patient sustains a left hemisection of the thoracic spinal cord (Brown-Séquard). Which finding is expected below the lesion?

Accepted Answer

Left-sided loss of proprioception; right-sided loss of pain/temperature

Answer

Brown-Séquard: ipsilateral (left) UMN weakness and dorsal column loss because those tracts are uncrossed at that level; contralateral (right) spinothalamic (pain/temp) loss because the STT crosses within 1-2 spinal levels.

Question 3

Which dopaminergic pathway is most associated with the positive symptoms of schizophrenia?

Accepted Answer

Mesolimbic pathway

Answer

Hyperactivity of the mesolimbic dopaminergic pathway (VTA to nucleus accumbens/limbic areas) underlies the positive symptoms (hallucinations, delusions) of schizophrenia.

Question 4

An ascending demyelinating polyneuropathy with albuminocytologic dissociation on CSF analysis and autonomic instability is most consistent with which diagnosis?

Accepted Answer

Guillain-Barré syndrome

Answer

Guillain-Barré syndrome is an autoimmune demyelinating polyradiculoneuropathy with ascending weakness, areflexia, albuminocytologic dissociation (high protein, normal cells), and potential autonomic dysfunction.

Question 5

A patient presents with fasciculations, muscle atrophy, hyperreflexia, and a Babinski sign in the same extremities. Which diagnosis best explains both upper and lower motor neuron signs?

Accepted Answer

Amyotrophic lateral sclerosis (ALS)

Answer

ALS selectively destroys both UMNs (cortex, corticospinal tract) and LMNs (anterior horn cells, cranial motor nuclei), producing simultaneous hyperreflexia/spasticity and fasciculations/atrophy.

NBME Practice Test

NBME Practice Test

NBME Neuroscience 3