MATERIAL and METHODS: The present study involved the retrospective review of radiologic examinations and medical files of 81 patients who underwent surgery for myelomeningocele between 2015 and 2022 in the neurosurgery clinic of Ankara Training and Research Hospital. Then, MMC sac volumes were measured and the statistical relationship of these measurements with the Evans Index, progressive enlargement of the ventricles after sac repair and CM was investigated.

RESULTS: Of the 81 patients, 41 (50.6%) were boys and 40 (49.4%) were girls. The median MMC sac volume was 11,005.28 mm³ and the mean Evans index (EI) based on brain tomography performed on postnatal day1was 0.405 ± 0.146. Analysis of the relationship between the EI and MMC sac volume yielded r=0.622, p<0.001 and showed a strong positive correlation between the two parameters at a statistical significance level of 5%. Evans Indexes based on brain tomography scans performed on postnatal day 1 showed that ventriculomegaly was present in 49 (60.5%) patients and absent in 32 (39.5%) patients. In patients who developed hydrocephalus after sac repair, there was no correlation between the day of intervention and sac volume. Mean sac volume was 28,297.36 mm³ in 28 patients with comorbid CM versus 7,600.32 mm³ in patients without CM. All children with CM required shunting.

CONCLUSION: Patients with larger myelomeningocele sac volume have higher risk of concomitant hydrocephalus or subsequent development of hydrocephalus after sac repair compared to patients with a smaller sac volume. These patients should definitely be evaluated for same-session intervention. Patients with a larger sac volume and/or comorbid CM should be followed up more frequently and for a longer period of time. Keywords : Arnold-Chiari malformation, Evans index, Hydrocephalus, Myelomeningocele, Ventriculomegaly