MORPHOLOGY OF THE CAUDAL FOSSA IN MESATICEPHALIC AND BRACHYCEPHALIC CATS AND ASSOCIATED CLINICAL SIGNS.

Morphological abnormalities of the caudal fossa are increasingly
recognized as a cause of morbidity in many brachycephalic
dogs but there is little information about these conditions in cats.
The objective of this study was to investigate presence of similar
morphological abnormalities of the caudal fossa of mesaticephalic
and brachycephalic cats and possible association with clinical signs
and final diagnosis.
Feline brain MRI studies at two referral centres were reviewed
for cases without visible disease that could alter anatomic
landmarks or raise intracranial pressure. T2 weighted median plane
images of the brain and if available spinal cord were reviewed for
the presence of caudal cerebellar indentation, coning, herniation,
syringohydromyelia, and fluid accumulation in the middle ear. Area
of the cerebral hemispheres and cerebellum was also measured Blind
measurements were taken by two observers and reviewed.
There were 53 feline MRI studies meeting the inclusion criteria.
Cerebellar herniation was found in 48% of mesaticephalic and
78% of brachycephalic cats. Syringohydromyelia was not identified
in any of the MR studies including only the first two cervical
spinal cord segments (36 cats) or more regions of the spinal cord
(17 cats). High signal on T2-weighted transverse images of the
middle ear was detected in 8% of mesaticephalic and 17% of
brachycephalic cat. Information on presenting complaint, results
of neurological examination and final diagnosis in cats with and
without cerebellar herniation was reviewed.
Mesaticephalic breed of cats show indentation of the caudal
aspect of the cerebellum and caudal cerebellar coning similar to
brachycephalic breeds of cats. The dimensions of the foramen magnum
planum and the area of the cerebral hemispheres and cerebellum
measured on a T2W sagittal MR image of the brain were also
similar between the two groups. However, brachycephalic cats had
a higher percentage of herniation of the cerebellar vermis through
the foramen magnum. Herniation of the cerebellar vermis does not
appear to be associated with syringomyelia in cats.