A 10-year-old, spayed domestic shorthaired cat presented with a 1-month history of walking in circles to the left and reluctance to go outside. She had previously been an indoor–outdoor cat and would readily spend a significant amount of time outside, but recently preferred to stay indoors and was often found hiding in the closet. The owners reported that she was eating, drinking, and eliminating normally.

Physical examination was unremarkable. On neurologic examination, the gait and segmental reflexes were within normal limits. Assessment of cranial nerves revealed an absent menace response in the right eye with normal palpebral and pupillary light reflexes in the left eye. The cat was circling propulsively to the left and had diminished postural responses in the right thoracic and pelvic limbs. The remainder of the neurologic examination findings were within normal limits.

Routine blood work (complete blood count, chemistry panel, and FeLV and FIV testing) and urinalysis results were all normal. Three-view thoracic radiographs were within normal limits. Magnetic resonance imaging (MRI) of the head was performed. T2-weighted (FIGURE A), T1-weighted (FIGURE B), and T1-weighted postcontrast (gadolinium; FIGURE C ) images were obtained.

1. What is the neuroanatomic diagnosis based on the neurologic examination?

2. Describe the lesion seen on MRI.

3. What is the presumptive diagnosis?

4. What is the prognosis?

To see the answers, download the pdf .