Specializing in Canine and Feline Neurology and Neurosurgery for over 35 years

Answer (Question 1): B and C. Nystagmus is characterized by the direction of the fast phase which is generally opposite to the side of the lesion.

Answer (Question 2): D is most correct. There is a slight head tilt to the left, marked horizontal to rotary nystagmus with fast phase to the right, and marked ventrolateral strabismus OS. These signs are consistent with a left peripheral vestibular disorder. However, the wide, side to side head excursions are suggestive of bilateral vestibular involvement. The additional history of seizures would implicate the forebrain (cerebrum or diencephalon) therefore, a diffuse or multifocal disease process is most likely.

Question: A brain MRI was done. The five axial images shown are axial images at the level of the interthalamic adhesion. Can you identify the abnormal finding?

Click on the images to enlarge


AXT2Large AXT1ContrastLarge AXT2StarLarge AXT1ContrastLarge AXFLAIRLarge

T2 (no contrast)

T1 (no contrast)

T2 star (no contrast)

T1 (contrast)

FLAIR (contrast)


Answer: On the T2 (no contrast) image there is a focal ill-defined hyperintensity in the left thalamus/hypothalamus. There are similar but less intense findings on the contralateral side. On the T1 (contrast) image the left thalamic/hypothalamic lesion shows slight contrast enhancement. There is no mass effect.

Comment: There was a curvilinear T2 hyperintensity in the left midbrain and in the substantia nigra region (not show above). The MRI findings in this patient are most consistent with mutiple infacts. No abnormalities were identified in the ear structures, medulla or cerebellum. No specific lesions accounting for the vestibular signs were identified, but it is likely that similar, occult lesions were affecting the brainstem, inner ear structures or 8th nerve(s).

Question: Which of the following are associated with ischemic brain infarction?