Occult residual disease after presumed gross-total resection of a predominantly intramuscular paraspinal lumbar schwannoma: a case report introducing the VERIFY-GTR end-of-resection bundle.

Background: Paraspinal schwannomas arising from exiting lumbar nerve roots are uncommon but clinically important because deep intramuscular extension can obscure tumor boundaries. In multilobulated lesions, an intraoperative declaration of gross-total resection (GTR) based on direct visualization alone can be misleading. Case Description: A 60-year-old man presented with 12 months of progressive left anterolateral thigh pain and numbness [Visual Analogue Scale (VAS) 6/10; Oswestry Disability Index (ODI) 70%] without motor deficit. Magnetic resonance imaging (MRI) demonstrated a large, predominantly extraforaminal/paraspinal dumbbell schwannoma from L1 to L2 (30 mm × 43 mm × 72 mm; ellipsoid volume approximately 48.6 cm Conclusions: Occult residual tumor can persist after apparent GTR and complete clinical recovery. We propose VERIFY-GTR: a proposed, auditable end-of-resection verification bundle coupled with an early postoperative contrast-enhanced MRI baseline (ideally within 48-72 hours when feasible) to define a combined surgical plus radiologic endpoint for radiologically verified GTR, avoid premature finalization of GTR status based on intraoperative inspection alone, and to guide surveillance intensity.