Diagnostic yield and adverse effects of MRI-guided free-hand brain biopsies through a mini-burr hole in dogs with encephalitis.

Background: The diagnosis of encephalitis is usually presumptive based on MRI, cerebrospinal fluid analysis, or both. A definitive diagnosis based on histopathology, however, is required for optimizing treatment strategies.

Objective: To investigate the diagnostic yield and adverse effects of minimally invasive brain biopsies in dogs with encephalitis.

Animals: Seventeen dogs with suspected encephalitis, based on MR imaging and cerebrospinal fluid analysis.

Methods: Retrospective study. Minimally invasive, free-hand brain biopsy specimens were taken from forebrain lesions through a 4-mm burr hole using a Sedan side-cutting needle. Routine histopathological examination was performed. The adverse effects were assessed by MRI evaluations after biopsy procedure (12/17) and by sequential neurological examinations.

Results: The overall diagnostic yield with regard to a specific type of encephalitis was 82%. Encephalitis was evident in an additional 12%, but a specific disease could not be determined. There were no deaths caused by the biopsy procedure itself, but the indirect case fatality rate was 6%. Morbidity was 29%, including stupor, seizures, tetraparesis, hemiparesis, ataxia, and loss of conscious proprioception. All these signs resolved within 3-14 days.

Conclusions and clinical importance: Minimally invasive brain biopsy in dogs with suspected encephalitis leads to a definite diagnosis in the majority of dogs, allowing for a specific treatment. The advantages of a definite diagnosis outweigh potential case fatality rate and temporary neurological deficits.