A novel five-category multimodal T1-weighted and T2-weighted magnetic resonance imaging-based stratification system for the selection of spinal arachnoid cyst treatment: a 15-year experience of 81 cases

BACKGROUND: Idiopathic spinal arachnoid cysts are rare cystic masses of the spinal canal generally classified as intra- or extradural, based on anatomical presentation. However, this system may not effectively indicate treatment. OBJECTIVE: To investigate the incidence, resection modality, and prognosis of spinal arachnoid cyst in a 15-year case series. PATIENTS AND METHODS: A retrospective study was conducted in 81 spinal arachnoid cyst patients (male:female 34:47, mean age 36.5 years, age range 6–66 years) classified using a novel five-category T1-weighted and T2-weighted magnetic resonance imaging (MRI) classification system (intramedullary, subdural extramedullary, subdural/epidural, intraspinal epidural, or intraspinal/extraspinal). Conservative treatment failed in all patients. They underwent spinal surgery between January 1995 and December 2010 and were followed up for 69 (range 3–187) months. Performance outcomes were assessed using the Fugl-Meyer (FM) scale 90 days after operation. Recurrences and deaths were recorded. RESULTS: Subdural/epidural and intraspinal epidural cysts accounted for 66.7% (54 of 81) of patients, but exhibited relatively lower rates of postsurgical improvement using FM, with only 66.7% (36 of 54) of patients showing improvements. Excellent outcomes using the FM scale were reached in 100% (eight of eight) of intramedullary, intraspinal/extraspinal, and subdural extramedullary cyst patients, 86.7% (13 of 15) of subdural extramedullary cyst patients, and 66.7% (36 of 54) of epidural intraspinal cyst patients. CONCLUSION: The proposed five-category multimodal MRI-based stratification system for spinal arachnoid cyst patients may more effectively allow clinicians to select the appropriate surgical intervention, and may help to predict outcomes.