Occult tethered cord syndrome: a rare, treatable condition

Occult tethered cord syndrome (OTCS) is an entity that shows tethered cord syndrome (TCS) with normal spinal MRI findings. The definition and treatment of OTCS have been controversial since first proposal. The purpose of this study was to evaluate the existence, prevalence, histological characteristics, and surgical outcomes of OTCS.We retrospectively analyzed patients who underwent untethering surgery for OTCS from January 2010 to December 2019. Inclusion criteria were (1) clinical manifestation of TCS; (2) supported by urodynamic study (UDS) or electromyography/nerve conduction study; (3) no structural lesions in the urological tract or spinal cord, and no developmental delay; and (4) postoperative follow-up for > 6 months. Sectioned fila from OTCS patients were histologically compared with those from cases of thickened filum or low-lying conus.Five (four female, one male) of 439 patients (1.1%) who underwent untethering surgeries for occult spinal dysraphism corresponded to OTCS. Mean age at the time of surgery was 16 years (7-22 years). Mean postoperative follow-up duration was 45 months (15-114 months). The main symptom was urinary dysfunction in four patients and leg pain in one. All patients had detrusor-sphincter dyssynergia. Fila from OTCS patients revealed increased fibrous tissue as in TCS patients. Four patients showed postoperative improvement and one with preoperative static course had no improvement.This study suggests that OTCS is a definitely existing entity although rare. OTCS is curable when timely treatment is given. Sudden onset with rapid progression of symptom seems the best indication for surgery.