Prenatal diagnosis of Chiari malformation with syringomyelia in the second trimester.

Routine anatomic ultrasound performed in the second trimester has a detection rate of approximately 70-90% for fetal congenital abnormalities (Nyberg and Souter, J Ultrasound Med 2001;6:655-674). The central nervous system abnormalities are one of the most common ones detected. Chiari malformation is among the CNS abnormalities diagnosed in the fetal period (Bianchi et al., Fetology - diagnosis and management of the fetal patient, McGraw-Hill, 2000). The Arnold-Chiari malformation was first described in 1883 by Cleland (Romero et al., Prenatal diagnosis of congenital anomalies, Appleton and Lange, 1988). It is characterised by the prolapse of the hindbrain structures below the level of the foramen magnum. It can be associated with skeletal abnormalities and neurological dysfunction. In type I, a lip of cerebellum is downwardly displaced with the tonsils, but the fourth ventricle remains in the posterior fossa. This condition may coexist with syringomyelia, which is a cyst formation on the cervical portion of the spinal cord (Creasy et al., Maternal fetal medicine principles and practice, 2004). We present a case where Chiari type 1 and syringomyelia detected at 18 weeks of gestation. The reason for referral to our center was an abnormal inward posturing of both upper and lower extremities (minimal gross movement and almost inexistent range of motion on fetal joints). On further fetal evaluation, an abnormal brain ultrasound was identified. Prenatal diagnosis of Chiari type 1 malformation and syringomyelia is almost nonexistent when reviewing the literature is the reason why this case is presented.