Neurology Case of the Month (Sept 2012): Ataxic Wheaten TerrierWritten on September 02, 2012 by Mark Troxel, DVM, DACVIM (Neurology) Hospital: Massachusetts Veterinary Referral Hospital

Signalment: 11yr MC Wheaten Terrier

History: One month progressively abnormal gait. Significant worsening in the past 48 hours with development of a head tilt.

Case Video:

Neurological exam:

Mental status: QAR / disoriented
Gait/posture:
Right head tilt, leaning & veering to the right, left-sided hypermetria
Cranial nerves:
WNL – no nystagmus noted
Postural reactions:
Absent CP & delayed to absent hopping LFL & LHL; normal CP & hopping RFL & RHL
Spinal reflexes:
WNL x 4
Spinal pain:
None
Muscle tone:
Normal x 4
Muscle atrophy:
None
Pain sensation:
Normal x 4
Cutaneous trunci:
Normal bilaterally

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


 

 

 

 

 

 

Neurolocalization = Left paradoxical central vestibular

 

Why is this paradoxical? The paradox is that the vestibular signs (head tilt, leanign/veering) suggest a right-sided lesion while the hypermetria suggests a left-sided lesion. When paradoxical signs are present, the lesion is located ipsilateral to the postural reaction deficits. With paradoxical vestibular disease, the lesion location is in the cerebellum or caudal cerebellar peduncle. Hypermetria in this case was also consistent with a cerebellar disorder. In some cases of cerebellar disease, you may observe an absent menace response ipsilateral to the lesion in patients that are visual and have a positive blink reflex (indicating normal optic & facial nerve function). This is because the cerebellum has an influence on the menace response.

 

Differential diagnoses

  • Neoplasia
  • Encephalitis
  • Other much less likely causes: degenerative diseases, anomaly

Infarction is very unlikely given progression of clinical signs, unless the recent worsening was unrelated to the 1-month progressive signs. However, this would be uncommon.

 

Diagnostics

  • CBC/biochemical profile: stress leukogram, mildly elevated ALP
  • Systolic BP: 150 mmHg
  • Thoracic radiographs: WNL for age/breed
  • MRI: Poorly contrast-enhancing intra-axial cerebellar mass
  • CSF: WNL

 

Diagnosis
Presumptive glioma, but other neoplasms or focal inflammatory/infectious disease can’t be excluded

 

Treatment
The mass is not surgically accessible. Radiation therapy (RT) would be the most definitive treatment option and may provide up to 1-2 years survival time. Chemotherapy may provide a few extra months survival time over prednisone alone, which has an average survival time of about 3-6 months. The patient was started on prednisone to reduce edema surrounding the mass. If there is a good response to prednisone, they will be pursuing RT.

 

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