Midline sacral meningeal cysts: Neurophysiology abnormalities and their correlation with pelvic sensory and visceral symptoms.

Background and purpose: Midline sacral meningeal cysts (MSMCs) are cerebrospinal fluid-filled dural diverticula. Although widely considered asymptomatic, cases involving voiding difficulties or pain have been reported. The aims of this study were, firstly, to describe the clinical presentation of patients with symptomatic MSMCs, secondly, to assess the impact of the cyst on nerve root function, and, thirdly, to assess whether nerve root injury is more frequent in patients with MSMCs than those with Tarlov cysts (TCs).

Methods: Consecutive patients with MSMCs presenting with at least one pelvic symptom participated in a cross-sectional review of symptoms using validated questionnaires. Findings of pelvic neurophysiology (pudendal sensory evoked potentials, sacral dermatomal sensory evoked potentials, external anal sphincter electromyography) and urodynamic testing were collected retrospectively. The relationship between neurophysiology, magnetic resonance imaging findings and patients' symptoms were assessed using Fisher's and analysis of variance tests. Neurophysiology findings were compared with those of TC patients.

Results: Eleven female patients were included (mean age 42.3 ± 12.4 years). All reported urinary symptoms. Back pain (91%), radicular leg pain (91%), bowel symptoms (45%) and sexual dysfunction (75%) were also frequently reported. Nine patients (82%) had abnormal findings on neurophysiology; three patients (27%) had one abnormal test, and six (55%) had two abnormal tests. Patients with MSMCs were more likely to have at least two abnormal neurophysiology test results compared to TC patients (55% vs. 18%, respectively; p = 0.018).

Conclusion: Our results indicate that MSMCs are indeed associated with injury to the sacral somatic innervation when symptomatic. MSMCs are more likely to cause sacral nerve root damage compared to TCs.