Neurology Case of the Month (Nov 2012): Chronic, progressive ataxia in a Labrador

Written on November 01, 2012 by Mark T. Troxel, DVM, DACVIM (Neurology) Hospital: Massachusetts Veterinary Referral Hospital

Signalment: 7yr MC Lab

History: The patient was referred to the Neurology Department for evaluation of a 6-month progressive gait abnormality. The patient had not responded to oral antibiotics (Clavamox) or a tapering course of prednisone.

Case Video:

What is your neurolocalization? What are the top differential diagnoses? (SCROLL DOWN TO SEE NEURO EXAM DETAILS AND ANSWERS)

Neurological exam:

Mental status: QAR
Gait/posture: Marked cerebellar/vestibular ataxia, truncal ataxia, intermittent thoracic limb hypermetria, intention tremors
Cranial nerves: WNL
Postural reactions: Normal CP x 4
Spinal reflexes: WNL x 4
Spinal pain: None
Muscle tone: Normal x 4
Muscle atrophy: None
Pain sensation: Normal x 4
Cutaneous trunci: WNL bilaterally

Neurolocalization = Cerebellum

Differential diagnoses

• Neoplasia
• Encephalitis
• Cerebellar abiotrophy or other degenerative disorder

Diagnostics

• CBC/biochemical profile: Unremarkable
• Thoracic radiographs: WNL for age/breed
• MRI: See image below. On T2-weighted images, there is an increase in the amount of CSF signal surrounding the cerebellum suggesting atrophy of the cerebellar folia.
• CSF: WNL

Diagnosis
Presumptive cerebellar abiotrophy

Treatment
Unfortunately, there are no effective treatment options available for cerebellar abiotrophy.

Prognosis
The prognosis for cerebellar abiotrophy is generally poor. Most patients continue to progress despite supportive care, although some patients signs will stabilize.

Outcome
The patient was humanely euthanized due to the progressive signs and guarded to poor prognosis. Necropsy confirmed the diagnosis of cerebellar abiotrophy.

CEREBELLAR HYPOPLASIA VS. ABIOTROPHY

• Cerebellar hypoplasia – This is a condition in which there is loss of the Purkinje cell layer and hypoplasia of the granular cell layer in the cerebellum due to disease affecting the cerebellum prior to birth or very soon after birth. The clinical signs are present when the patient first starts to ambulate and are not progressive. The most common form in small animals is feline cerebellar hypoplasia secondary to feline panleukopenia virus. It occurs in dogs as well, but much less commonly. Canine herpes virus and parvovirus have been implicated in some cases.
• Cerebellar abiotrophy – This is a condition in which there is spontaneous, premature, and progressive loss of the Purkinje cell layer in the cerebellum due to an unidentified inborn error of metabolism. These patients are normal when they first start to ambulate and the signs don’t occur until months to years later. It is seen most often in young dogs (e.g., Kerry Blue Terrier, young adult Gordon Setters), but it has a “geriatric” onset in several breeds of dogs (e.g., Brittany Spaniel, Old English Sheepdog)