Long-term outcomes following surgical treatment of spinal arachnoid cysts: a population-based consecutive cohort study

Abstract

Background context: Spinal arachnoid cysts (SACs) are rare, cerebrospinal fluid-filled sacs lined by an arachnoid membrane in the spinal canal. Symptoms can develop due to pressure on the spinal cord or adjacent spinal nerves by the cyst itself or by interrupted flow of cerebrospinal fluid. If noninvasive management fails or neurological deterioration occurs, surgical treatment is recommended. However, data is lacking on long-term outcomes after surgery.

Purpose: To determine long-term outcomes in patients surgically treated for SACs.

Study design: Population-based cohort-study.

Patient sample: All consecutive patients treated for either intra- or extradural SACs with surgery between 2005 and 2020 at the author's institution were included.

Outcome measures: American Spinal Injury Association Impairment Scale (AIS) and modified Japanese Orthopedic Association score (mJOA).

Methods: Data was primarily extracted from electronic patient medical notes. Telephone interviews were performed to assess long-term postoperative outcomes. All analyses were conducted using the statistical software program R version 4.0.5. Statistical significance was set at p<.05.

Results: Thirty-four patients were included. Cyst excision was performed in 11 (32%) cases, and fenestration in the remaining 23 (68%). The median follow-up time was 8.0 years. Surgery resulted in a significant long-term improvement in both AIS (p=.012) and mJOA (p=.005). Sensory deficit was the symptom that most often improved (81%), followed by pain (74%) and motor function (64%). AIS deteriorated in two patients, of which one case was attributed to a surgical complication. Local cyst recurrence requiring reoperation was seen in 4 (12%) cases, all of them following cyst fenestration. One patient (3%) required reoperation for progression of the cyst progression at a different level.

Conclusion: This study reports outcomes of surgically treated SACs with the longest follow-up time to date. Microsurgical cyst excision or fenestration were safe treatment options, and the neurological improvements seen in the immediate postoperative phase were maintained at long-term follow-up.

Keywords: Extradural cyst; Intradural cyst; Long-term outcome; Neurosurgery; Spinal arachnoid cysts; Spinal cord; Spine surgery.