Q.  This 14-year-old female spayed Labrador dog presents to you for a second opinion 8 months after surgical excision of a right parietal lobe meningioma.  The dog initially presented for seizures, head tilt, and behavioral changes before the diagnosis of the meningioma.  Since that time, seizures have been well-controlled with levetiracetam and the head tilt is persistent but improved.  The dog’s behavior changes have slowly progressed, however, with increasing episodes of confusion, inappropriate urination in the house, and increased pacing at night.  You repeat the MRI with pertinent images shown here.  What might account for the behavior changes seen at home?

A.  The dog most likely has canine cognitive dysfunction syndrome from age-related cortical degeneration.  This is based on the prominent sulci and small interthalamic adhesion measurement.  These are changes that can be related to the behavioral signs at home which can still progress despite effective treatment of the meningioma disease.  The irregular appearance to the right parietal lobe is consistent with previous surgical excision of the meningioma.  Contrast enhanced T1 images showed dural-tail type enhacement at the dorsalmedial and lateral aspects of the lesion area without mass effect.

“Measurement of interthalamic adhesion thickness as a criteria for brain atrophy in dogs with and without cognitive dysfunction (dementia)”

Hasegawa et al.

VRUS, Vol 46, No 6, 2005: 452-457

78 dogs of various breeds aged 6 months-18 years.  Average ITA thickness was 6.79+/- 0.70mm in clinically normal dogs versus 3.82+/-0.79mm in clinically demented dogs.

Other typical signs of age-related brain atrophy include:

1. Enlargement of the ventricular system
2. Well-demarcated sulci (enlargement of the subarachnoidal space)
3. Diffuse and scattered T2 hyperintensity lesions in the periventricular white matter

1 and 2 come from parenchymal atrophy.  T2 hyperintensity can come from myelin degeneration, gliosis, or enlarged Virchow-Robin spaces.

While smaller dogs had overall smaller ITA thicknesses, the only statistically significant correlation was between dogs with dementia and behaviorally normal dogs.  A study looking at lysosomal storage disease documented progressive decrease in ITA size suggesting this can be a good measure of parenchymal loss.  Another differential can include increased pressure from obstructive hydrocephalus as was noted in a separate case of a Golden with cerebellar meningioma and small ITA measurement presumed to be associated with intracranial pressure changes related to CSF flow obstruction.