Chiari I malformation and pregnancy: a comprehensive review of the literature to address common questions and to guide management

The optimal management of Chiari I malformation during pregnancy remains uncertain. Labor contractions, which increase intracranial pressure, and neuraxial anesthesia both carry the theoretical risk of brainstem herniation given the altered CSF dynamics inherent to the condition. Mode of delivery and planned anesthesia, therefore, require forethought to avoid potentially life-threatening complications. Since the assumed potential risks are significant, we seek to systematically review published literature regarding Chiari I malformation in pregnancy and, therefore, to establish a best practice recommendation based on available evidence.

The English-language literature was systematically reviewed from 1991 to 2018 according to PRISMA guidelines to assess all pregnancies reported in patients with Chiari I malformation. After analysis, a total of 34 patients and 35 deliveries were included in this investigation. Additionally, a single case from our institutional experience is presented for illustrative purposes but not included in the statistical analysis.

No instances of brain herniation during pregnancy in patients with Chiari I malformation were reported. Cesarean deliveries (51%) and vaginal deliveries (49%) under neuraxial blockade and general anesthesia were both reported as safe and suitable modes of delivery. Across all publications, only one patient experienced a worsening of neurologic symptoms, which was only later discovered to be the result of a previously undiagnosed Chiari I malformation. Several patients underwent decompressive suboccipital craniectomy to treat the Chiari I malformation during the preconception period (31%), during pregnancy (3%), and after birth (6%). Specific data regarding maternal management were not reported for a large number (21) of these patients (60%). Aside from one abortion in our own institutional experience, there was no report of any therapeutic abortion or of adverse fetal outcome.

Although devastating maternal complications are frequently feared, very few adverse outcomes have ever been reported in pregnant patients with a Chiari I malformation. The available evidence is, however, rather limited. Based on our survey of available data, we recommend vaginal delivery under neuraxial blockade for truly asymptomatic patients. Furthermore, based on our own experience and physiological conceptual considerations, we recommend limiting maternal Valsalva efforts either via Cesarean delivery under regional or general anesthesia or by choosing assisted vaginal delivery under neuraxial blockade. There is no compelling reason to offer suboccipital decompression for Chiari I malformation during pregnancy. For patients with significant neurologic symptoms prior to conception, decompression prior to pregnancy should be considered.