Neurotransmitter – Winston

winstonWinston, a 6 year old Cavalier King Charles Spaniel, was referred by Seneca Hill Animal Hospital for collapse with a concern for a seizure like episode.

Presenting Complaint/History:
Winston was out for a walk when he collapsed on his side, went stiff and starting trembling. He remained stiff with an altered gait overnight and in the morning could walk a little but would stagger to the right.

Exam Findings:
Winston was ambulatory with marked ataxia. He would fall and list to the right and “crab walked” to the right. He was hypermetric in the left thoracic and pelvic limbs. His right limbs had normal proprioception, but his left limbs had absent placing and hopping was delayed and exaggerated. He had a normal menace response bilaterally and a normal physiologic nystagmus. He was not painful on palpation of his head or spine.

Localization / Assessment:
Left vestibular system because of his tetra-ataxia, falling and listing to the right. Most concerned for a central lesion due to his left sided CP deficits and specifically the cerebellum because of his absent menace response.

MRI showed a lesion in the left dorsolateral cerebellum most consistent with a cerebrovascular accident (stroke). See figure 1.


xrayCross sectional MRI of the brain at the level of the rostral cerebellum. The image shows the cerebrum dorsally, the pons ventrally and the cerebellum in the middle. The white triangle on the left side of the cerebellum is the area of the stroke and comprises about 1/4 of the cross sectional area of the cerebellum.

CSF centesis and analysis showed a neutrophilic pleocytosis (elevated number of WBC, specifically neutrophils).

Left cerebellar stroke.

Cerebrovascular accidents (strokes) occur in dogs and cats from disease in the blood vessels that supply the brain. The most common area of the brain to be affected is the cerebellum, with the rostral cerebellar artery being the most commonly affected blood vessel. However, strokes can occur anywhere in the brain. Signs of stroke vary depending on the area affected. With cerebellar strokes the most common signs are ipsilateral ataxia, head tilt, nystagmus, opisthotonus and menace deficits.

In about half of all dogs, an underlying etiology is never found. However, a variety of diseases including neoplasia, hypertension, hypothyroidism, sepsis, vascular malformations, coagulopathies, chronic renal disease and hyperadrenocorticism have all been associated with strokes and searching for an underlying cause is recommended. The prognosis is generally good for dogs and cats with strokes with no underlying cause and in animals where the underlying cause is found and treated. Supportive care both in hospital and at home may be needed depending on their deficits and level of impairment. Most animals recover within a few weeks.

MRI is the gold standard for diagnosing strokes. We use a variety of sequences including diffusion-weighted imaging (DWI) to diagnose strokes and differentiate them from other possible lesions including neoplasia and inflammatory disease. CSF centesis and analysis is also sometimes performed and the results can range from normal to a mild to moderate monocytic or neutrophilic pleocytosis.

Within two to three days, Winston was walking well and was about 90% normal. A few weeks later, his family reported that he was completely normal.

Take Home Points:
1. Cerebrovascular accidents (strokes) can occur in any dog or cat breed.
2. About half of dogs affected will have a primary disease process associated with the stroke and treating that primary disease will improve chances of them not having another stroke.
3. Half of dogs who have strokes have no underlying disease process that can be identified. We often see them recover and never have another stroke.
4. Signs will vary with the region of the brain affected. Supportive care, both in hospital and at home, are usually what the dog needs most and most make an excellent recovery within a few weeks.