Primary intradural extramedullary lesions: a longitudinal study of 212 patients and analysis of predictors of functional outcome.

Background: Primary intradural extramedullary (IDEM) lesions are rare, with an incidence of about 1/100,000 person-years. The aim of this study was to investigate their demographic, clinical, imaging, management, histopathological and outcome parameters. Another objective was to evaluate the various predicting factors leading to long-term favorable outcomes, thereby answering the controversial question: when to operate?

Methods: This study observed 212 patients of primary IDEM lesions and followed-up for a mean of 53.80 months. The patient's outcome using McCormick grade at follow-up was correlated with age, sex, duration of symptoms, preoperative McCormick grade, tumor location and extent, extradural spread, extent of excision, vascularity, WHO grade and histopathological tumor type.

Results: Benign nerve sheath tumors were the commonest lesions (47.17% schwannoma, 4.72% Neurofibroma), followed in incidence by meningioma (19.34%). There was predominance of males (57.08%), except in meningiomas (male: female ratio 1:2.15). Pain was the commonest initial symptom (51.88%). Limb weakness was the most common presenting complaint (88.68%). Gross total excision was achieved in 81.60% of cases and 70.75% of patients improved following surgery. The significant factors predicting favorable outcome included preoperative McCormick grade (P=0.001), the vertical extent of the tumor (P=0.027), histopathological tumor type (P=0.023) and WHO grading (P=0.015); and extent of excision had an odds ratio of 1: 2.5.

Conclusions: Significant predictors of functional outcome following surgery in IDEM lesions included preoperative McCormick grade, extent of the tumor, tumor type, WHO grading and extent of resection. The authors recommend surgery with the intent of complete tumor excision, before the onset of substantial symptoms, for better outcome.