Presurgery motor level assessment for prediction of motor level at birth in fetuses undergoing prenatal repair of open spina bifida: time to abandon anatomical level in counseling

OBJECTIVES

First, to investigate the correlation between prenatal presurgery anatomical and motor levels of the lesion with motor level at birth in cases undergoing prenatal repair of open spina bifida and, second, to identify factors leading to a loss of two or more motor levels between the presurgery and postnatal assessments.

METHODS

This was an observational study of singleton pregnancies undergoing prenatal repair of open spina bifida, conducted between March 2011 and May 2022. All fetuses underwent an ultrasound assessment at 20-24 weeks of gestation to determine the motor and anatomical levels of the lesion before surgery. The anatomical level of the lesion was defined as the highest open posterior vertebral arch. The motor level was determined by systematic observation of the lower limb movements and was defined as the most distal active muscle present. Prenatal repair was performed at 23-26 weeks. At birth, motor level was assessed by a rehabilitation specialist by physical examination. Cases of intrauterine death or termination of pregnancy and those delivered at other sites were excluded from the neonatal assessment. The agreement between presurgery motor level and motor level at birth, and between presurgery anatomical level and motor level at birth, was assessed using the weighted kappa index (wκ). Logistic regression analysis was used to assess factors leading to a loss of two or more motor levels between the presurgery and postnatal assessments.

RESULTS

Presurgery motor and anatomical levels were assessed in 61 fetuses at a median gestational age of 22.7 (interquartile range (IQR), 21.6-24.4) weeks. Prenatal repair was performed at a median gestational age of 24.6 (IQR, 23.7-25.7) weeks. Motor level at birth was assessed in 52 neonates after exclusion of nine fetuses due to loss to follow-up or fetal loss. There was moderate agreement between presurgery motor level and motor level at birth (wκ = 0.42; 95% CI, 0.21-0.63), with a median difference of 0 (IQR, -2 to 9) levels. Factors leading to a loss of two or more motor levels between the presurgery ultrasound assessment and postnatal examination were higher presurgery anatomical level (odds ratio (OR), 0.59 (95% CI, 0.35-0.98); P = 0.04) and larger difference between the anatomical and motor levels before surgery (OR, 1.85 (95% CI, 1.12-3.06); P = 0.017). None of the other ultrasound, surgery-related or neonatal variables assessed was associated significantly with a loss of two or more motor levels. There was slight agreement between the presurgery anatomical level of the lesion and motor level at birth (wκ = 0.07; 95% CI, -0.02 to 0.15).

CONCLUSIONS

There is moderate agreement between fetal motor level of the lesion before prenatal repair of open spina bifida and motor level at birth, as opposed to only slight agreement between presurgery anatomical level and motor level at birth. A loss of two or more motor levels between the presurgery and postnatal assessments is associated with a higher presurgery anatomical level and with a larger difference between the presurgery anatomical and motor levels. Consequently, motor level, rather than the anatomical level, should be used for prenatal counseling. © 2023 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.