Case 29 Answers

Basic Human Neuroanatomy

A Clinically Oriented Atlas

Case 29 Answers

1. What is the cause of the diplopia and the ptosis?

Right oculomotor nerve (III) lesion

2. Is the left facial weakness of the upper motor neuron or lower motor neuron type?

Upper motor neuron (UMN) facial weakness

3. How precisely can the neurologic lesion be localized in this case?

Very precisely

4. What specific structures are involved to produce the left UMN facial weakness?

Right corticonuclear (corticobulbar) fibers above the lower pons

5. What specific structures are involved to produce the left-sided weakness?

Right corticospinal fibers above the lower pons

6. Why are the motor signs and ocular signs on opposite sides of the body?

UMN (pyramidal) tracts cross in the lower medulla (pyramidal decussation) to supply spinal cord LMNs

7. What is the location of the neurologic lesion, and which side of the nervous system is involved?

Right upper midbrain (superior colliculus level), with involvement of the right oculomotor nerve (III) as it emerges into the interpeduncular fossa and the right pyramidal tract fibers in the crus cerebri

8. The findings in this case represent a classic neurological syndrome. What is the name of that syndrome?

Weber syndrome

9. In general, what type of pathologic process do you think is involved in this case?

Subacute Weber syndrome caused by a Basilar tip aneurysm compressing the right crus cerebri and right oculomotor nerve (III)

10. What diagnostic procedure(s) would you undertake at this point?

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