Fluctuation of Clinical Signs With Near-Syncopal Episodes in a Dog With Gliomatosis Cerebri: A Diagnostic Challenge.

A 2-year-old Bull Mastiff cross Boxer neutered male dog was evaluated because of 2-month history of non-progressive right head tilt and mild vestibular ataxia. MRI of the brain revealed a faint T2W, FLAIR, DWI and ADC heterogenous hyperintense and T1W isointense intra-axial lesion with indistinct margins at the level of the pons and medulla oblongata. The lesion did not show any susceptibility artefact on T2* GRE images or contrast enhancement and CSF analysis was normal. Analysis of the spectra from MRS of the thalamus not promptly available at the time of the MRI study revealed a decreased level of NAA, as seen in people with gliomatosis cerebri. The dog represented 3 weeks later and, on this occasion, displayed left-sided head tilt, left-sided postural reaction deficits and near-syncopal episodes associated with state of confusion. Repeated MRI revealed a larger non-enhancing intra-axial lesion with a more hyperintense signal than previously described. CSF was normal and PCR of CSF for infectious diseases was negative. Thoracic and abdominal computed tomography did not reveal any primary or metastatic process. Immunosuppressive treatment was attempted and the dog remained stable over 5 days, then developed generalized tonic-clonic seizures which led to status epilepticus and death. Histopathology supported the diagnosis of gliomatosis cerebri. Gliomatosis cerebri remains difficult to diagnose ante-mortem, due to the broad age of onset and the variable duration and wide range of clinical signs. The mismatch between MRI findings and clinical presentation, the fluctuating clinical signs with near-syncopal episodes associated with a state of confusion, the presence of an infiltrative brain disease as depicted on MR imaging and a normal CSF analysis, should prompt the clinician to consider possible diagnosis of a widespread infiltrative neoplasm. Although, MRS may help narrow the differential diagnosis in favor of a neoplastic lesion, the overall prognosis remains poor.