Anatomical–Motor Level Discrepancy in Prenatal Diagnosis of Open Spinal Dysraphism: A 12‐Year Retrospective Observational Study

OBJECTIVES: To quantify the discrepancy between anatomical and motor levels in foetuses with open spinal dysraphism and identify prenatal factors associated with this difference. We also examined associations between anatomical level and ultrasound findings. DESIGN: Retrospective observational study. SETTING: Single tertiary referral centre. POPULATION OR SAMPLE: A total of 187 foetuses diagnosed with open spinal dysraphism between 2011 and 2022. METHODS: Anatomical level was defined as the highest non-closed vertebra on ultrasound. Motor level was determined through dynamic assessment of the most caudal active muscle group. The anatomical-motor level difference was calculated, and linear regression analyses were used to evaluate associated clinical and ultrasound variables, adjusting for anatomical level. MAIN OUTCOME MEASURES: Difference between anatomical and motor levels; association of ultrasound features with anatomical level. RESULTS: In 85.0% of foetuses, the motor level was more caudal than the anatomical level, with a median difference of two vertebral segments (range -3 to +15). Greater discrepancies were associated with myeloschisis compared to myelomeningocele (adjusted coefficient: 0.78, p < 0.001). Bilateral talipes and kyphosis were linked to smaller discrepancies. Higher anatomical levels were significantly associated with ventriculomegaly and vertebral anomalies. CONCLUSIONS: In foetuses with open spinal dysraphism, the motor level assessed by prenatal ultrasound is frequently more caudal than the anatomical level, with a discrepancy in over 80% of cases. The magnitude is influenced by lesion type and anatomical height, with myeloschisis and higher lesions showing greater differences. Additionally, anatomical level correlates with several ultrasound findings, including ventriculomegaly and vertebral anomalies.