Magnetic Resonance Imaging Contrast Enhancement of the Trigeminal Nerve in 42 Dogs without Evidence of Trigeminal Neuropathy
Medical records and brain magnetic resonance imaging (MRI) were reviewed retrospectively from 2002-2007 in order to establish the incidence of trigeminal nerve contrast enhancement in dogs with an otherwise normal MRI and no clinical evidence of trigeminal neuropathy. Only cases without abnormalities detected on blood work, CSF analysis or MRI, and where the neurological examination did not reveal any brainstem or trigeminal nerve abnormalities, were included in the study. The MRI of 42 dogs were evaluated by a board certified radiologist and board certified neurologist. The trigeminal nerve was divided into 3 regions identified as A, B, and C. The total number of evaluations performed by the reviewers was 126. Only in 3/126 (2.4%) of evaluations, could the trigeminal nerve not be identified. Region A was the only region where the trigeminal nerve could not be visualized (n=3). In 120/126 or 95% of these evaluations contrast enhancement was observed. In region A 34/42 (81%) of the dogs showed contrast enhancement. In region B 42/42 (100%) of the dogs had contrast enhancement of the trigeminal nerve. In region C 41/42 (98%) of dogs had contrast enhancement of the trigeminal nerve. The intensity of contrast enhancement was considered less than what was seen in the pituitary gland in 105/126 (83%) of the evaluations. MRI contrast enhancement of the trigeminal nerve was seen in a majority of dogs with no clinical evidence of trigeminal nerve pathology.