Abstract

A low risk 29–year-old primigravida booked at 8 weeks. Booking ultrasound was normal. Second trimester serum screening was abnormal with a raised AFP of 2.17MoM. Following this she had an ultrasound at 20 weeks that showed an Arnold Chiari malformation, prominent ventricles and disruption of the lumbosacral spine. Associated with this bony disruption was a hyperechoic tubular structure extending posteriorly with the appearances suggestive of a ‘tail’ that was continuous with an amniotic band. An MRI organised for further assessment was inconclusive with the spine essentially appearing normal. She underwent a repeat ultrasound scan, which confirmed the findings of the first. After counselling she underwent termination of pregnancy and consented to a full post-mortem. The autopsy identified “tethered cord syndrome” with a caudal tail. There was small spinal defect seen in the caudal region, but the defect was covered with skin. The filum terminale appeared to pass through the defect and was attached to the amniotic band above the skin closure. This is rare case of a “caudal tail” that has happened primarily because of an amniotic band that became attached to the spinal cord at the time of canal closure causing a tethered cord. Moreover, the inconclusive MRI was unable to provide further clarity of diagnosis resulting in greater importance being placed on the ultrasound findings. Use of MRI in early pregnancy for fetal anomalies needs to be interpreted with caution. It may be necessary to repeat the study again later in pregnancy to confirm the findings.