Antenatal ultrasound and magnetic resonance imaging in localizing the level of lesion in spina bifida and correlation with postnatal outcome.

OBJECTIVE

To compare prenatal ultrasonography and magnetic resonance imaging (MRI) in the diagnosis of spina bifida with postnatal MRI/surgical findings and to study the postnatal outcome in relation to the level of lesion and head signs on antenatal imaging.

METHODS

A retrospective study of babies referred to a tertiary neurosurgical unit with a diagnosis of spina bifida in the years 2000-2002 was performed. The levels of lesions and head signs diagnosed using antenatal ultrasonography and MRI were compared with postnatal MRI and operative findings. The levels of lesions and head signs diagnosed pre- and postnatally were used to study the correlation with neurological outcome at a mean follow-up period of 12 months.

RESULTS

Twelve antenatally diagnosed and five postnatally diagnosed cases of spina bifida were seen. The level of lesion as identified by antenatal ultrasound correlated with that observed postnatally in 8/12 cases and the antenatal ultrasound diagnosis of ventriculomegaly was confirmed postnatally in all cases. The level of lesion as identified by antenatal MRI correlated with that observed postnatally in 4/8 cases (50%) and the antenatal MRI diagnosis of ventriculomegaly was confirmed postnatally in 5/8 (63%) cases. 12/17 babies were found to have residuals in the immediate postnatal urodynamic studies, of which 83% (n = 10) required intermittent catheterization of the bladder at 12 months of age. Low spinal lesions were associated with increased bladder morbidity when compared to high spinal lesions (8/10 vs. 4/7, P < 0.05) (odds ratio (OR) = 10.0; 95% CI, 1.05-95.01). The level of spinal lesion and the presence of ventriculomegaly did not have any statistically significant correlation with motor functions, morbidity and developmental milestones.

CONCLUSIONS

Antenatal ultrasonography is a good tool in the diagnosis of spina bifida. We could not demonstrate any advantage of antenatal MRI over ultrasonography. There is better correlation of ultrasonography than MRI with postnatal MRI/operative findings in terms of level of lesion and head signs. Low spinal lesions appear to be associated with increased bladder morbidity.