COMPUTERIZED TOMOGRAPHY-GUIDED STEREOTAXIC SURGERY FOR BRAIN-STEM MASSES - A RISK-BENEFIT ANALYSIS IN 71 PATIENTS

The benefits of the use of computerized tomography (CT)-guided stereot actic surgical techniques for the management of intrinsic brainstem ma sses diagnosed from clinical evaluation and imaging studies were evalu ated vis-a-vis the risks involved in 71 consecutive patients. Seventy- two procedures were performed. The masses were diffuse, involving two or three contiguous brainstem segments, in 60 patients and focal in 11 patients. On the CT scans, 25 patients had hypodense nonenhancing mas ses, two had isodense nonenhancing masses, 19 had ring-enhancing masse s, and 25 had heterogeneously enhancing masses. A positive biopsy was obtained in 68 of 69 patients (98.5%) undergoing a biopsy procedure. I n nine patients (12.6%) with suspected malignant masses a benign patho logy was diagnosed (four tuberculomas, two epidermoid cysts, one pyoge nic abscess, one epidermal cyst, and one case of encephalitis). Additi onally, fluid from cystic masses could be aspirated in eight cases, pr oviding bene fit in six (four patients had benign lesions and two had neoplastic lesions). Thereby, a total of 13 patients (18.3%) were deem ed to have benefited from the surgery (two patients were included in b oth categories). Patients with focal masses and ring-enhancing masses had the highest proportion of benign lesions (60% and 36.8%, respectiv ely) and therefore derived the most benefit from histological verifica tion. There was no procedure related mortality. One patient (1.4%) suf fered permanent morbidity and four others (5.6%) had transient worseni ng attributable to the procedure. The authors conclude that CT-guided stereotactic surgery of the brainstem is safe and reliable. Histologic al verification of all enhancing (especially ring-enhancing) and focal brainstem masses should be undertaken to identify patients with benig n nonneoplastic lesions. Selected patients with diffuse hypodense none nhancing masses with atypical clinical or imaging features may also be nefit from stereotactic biopsy. Even in these patients the lack of enh ancement on a contrast-enhanced magnetic resonance image, rather than the diffuse location of the tumor alone, should form the basis for dia gnosing a malignant glioma. The main value of stereotactic surgery lie s in the identification of benign masses in a significant proportion o f patients with intrinsic brainstem masses and in providing a rapid an d safe method for evacuation of the contents of cystic masses.