PURPOSE: For intradural extramedullary (IDEM) tumors with extraspinal extension, complete neural decompression and complete tumor removal may require different anatomical exposures. We examined the long-term consequences of retaining an extraspinal residual after complete intraspinal decompression.
METHODS: This retrospective single-center cohort included 51 patients: 17 underwent GTR including the extraspinal component and 34 had retained extraspinal residual (STR). Thirty STR patients had reliable serial MRI for residual-growth analysis. Progression was defined as a ≥ 20% increase from the first postoperative MRI suitable for residual measurement (V1); V2 was the first threshold-crossing MRI in progressors. Nurick outcome, clinically significant progression, and reoperation were assessed separately.
RESULTS: Tumors were predominantly cervical (42/51, 82.4%) and mainly nerve-sheath tumors (45/51, 88.2%). Median clinical and radiological follow-up were 152.9 and 46.3 months, respectively. Median Nurick grade improved from 3 to 2 (paired n = 51, p < 0.001). Six of 30 evaluable STR residuals (20.0%; exact 95% CI 7.7-38.6%) met the growth threshold; 24 (80.0%) remained below it during the analyzed interval. The six progressors increased by 40.98 ± 16.13% on average. Final Nurick grade at ≥ 2 years was similar between growth groups (median 1 vs. 1; p = 0.588). Reoperation for retained/progressive extraspinal disease occurred in 2/34 STR patients (5.9%).
CONCLUSION: After complete neural decompression, many retained extraspinal residuals remain clinically manageable. Radiographic growth does not necessarily equal clinical failure. Extraspinal GTR should remain the goal when its incremental anatomical risk is acceptable; otherwise, retained residual with structured long-term surveillance may be reasonable.
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