• Open Access

Diagnostic Yield and Adverse Effects of MRI-Guided Free-Hand Brain Biopsies through a Mini-Burr Hole in Dogs with Encephalitis


  •  Brain biopsies were taken at the University of Leipzig (Germany). Histopathological examinations of biopsy specimens were performed at the Ludwig-Maximilians-University Munich, Germany. Postmortem samples were examined at the Ludwig-Maximilians-University Munich, Germany, and at the University of Bern, Switzerland

Corresponding author: Thomas Flegel, Department of Small Animal Medicine, University of Leipzig, An den Tierkliniken 23, 04107 Leipzig, Germany; e-mail: flegel@kleintierklinik.uni-leipzig.de.



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.


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


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


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.


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.