Serial stereotactic biopsy of brainstem lesions in adults improves diagnostic accuracy compared with MRI only

Objective: The aim of the current prospective study was to analyse the validity of MRI based diagnosis of brainstem gliomas which was verified by stereotactic biopsy and follow-up evaluation as well as to assess prognostic factors and risk profile. Methods: Between 1998 and 2007, all consecutive adult patients with radiologically suspected brainstem glioma were included. The MRI based diagnosis of the lesions was made independently by an experienced neuroradiologist. Histopathological evaluation was performed in all patients from paraffin embedded specimens obtained by multimodal image guided stereotactic serial biopsy technique. Histopathological results were compared with prior radiological assessment. Length of survival was estimated with the Kaplan-Meier method and prognostic factors were calculated using the Cox model. Results: 46 adult patients were included. Histological evaluation revealed pilocytic astrocytoma (n = 2), WHO grade II glioma (n = 14), malignant glioma (n = 12), metastasis (n = 7), lymphoma (n = 5), cavernoma (n = 1), inflammatory disease (n = 2) or no tumour/gliosis (n = 3). Perioperative morbidity was 2.5% (n = 1). There was no permanent morbidity and no mortality. All patients with "no tumour'' or "inflammatory disease'' survived. Patients with low grade glioma and malignant glioma showed a 1 year survival rate of 75% and 25%, respectively; the 1 year survival rate for patients with lymphoma or metastasis was 30%. In the subgroup with a verified brainstem glioma, negative predictors for length of survival were higher tumour grade (p = 0.002) and Karnofsky performance score <= 70 (p = 0.004). Conclusion: Intra-axial brainstem lesions with a radiological pattern of glioma represent a very heterogeneous tumour group with completely different outcomes. Radiological features alone are not reliable for diagnostic classification. Stereotactic biopsy is a safe method to obtain a valid tissue diagnosis, which is indispensible for treatment decision.