Case 196 Answers

Basic Human Neuroanatomy

A Clinically Oriented Atlas

Case 196 Answers

1. Considering the patient’s history and physical examination, how precisely can the neurologic lesion be localized in this case?

Not very precisely (see below and see slide #1)

2. Indicate the level of the neurologic lesion in this case as precisely as possible and the structures involved by the pathologic process. If precise localization is not possible, list as many levels or structures as you can that might produce the same clinical picture.

Signs or Symptoms
Weakness of RUE & RLE,
mild R UMN facial weakness

RUE & RLE neocerebellar signs
(dysmetria, impaired finger-to-nose,
heel-to-shin, dyssynergia,
intention tremor,
dysdiadochokinesis)

Site of Lesion
L corticospinal and corticonuclear tracts,
above the lower third of the pons

R cerebellar hemisphere, R SCP below
(or L SCP above) the inferior midbrain,
L VL nucleus of the thalamus,
L thalamocortical radiations,
L corticopontine tracts, L pontine nuclei

3. Discuss the “localization of the lesion” in this case.

It is difficult to localize the lesion in this case and in this syndrome. Basically, this syndrome can be caused by a fairly discrete lesion at any location where the corticospinal fibers and the neocerebellar (cortico-ponto-cerebellar) pathways lie in close approximation. The usual lesions (in a case such as this) would be in the left base of the pons, left cerebral peduncle involving the pyramidal tract in the crus cerebri and the superior cerebellar peduncle (SCP) after its decussation, and the left posterior limb of the internal capsule involving the pyramidal tract and the thalamocortical radiations and/or the frontopontine fibers.

4. The findings in this case represent a classic neurologic syndrome. What is the name of that syndrome, and what is its usual cause?

Ataxic hemiparesis. Lacunar infarct (variable locations, as above).

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

Vascular – Lacunar infarct is most common. In this case, the infarct was in the left basilar (anterior) part of the pons and involved the descending pyramidal tract fibers, the pontine nuclei, and the corticopontine fibers.

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

References:
1. Fisher CM, Cole M. J Neurol Neurosurg Psychiatry 1965;28:48-55.
2. Koppel BS, Weinberger G. Eur Neurol 1987;26:211-215.
3. Nabatame H, Fukuyama H, Akiguchi I, et al. Ann Neurol 1987;21:204-207.
4. Helweg-Larsen S, Larsson H, Henriksen O, Sorensen PS. Neurology 1988;38:1322-1324.

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