Abstract | March 5, 2024
Prenatal Diagnosis of Fetal Brainstem Disconnection
Learning Objectives
- Understand the negative prognostic implication of the finding of brainstem disconnection in the setting of Dandy Walker malformation
- Describe the role that prenatal diagnosis plays in allowing for shared decision making and informed care
- Explain how prenatal imaging can inform delivery planning
Introduction: Dandy-Walker is a common posterior fossa malformation, with phenotypes ranging from mild to severe. Diagnosis is usually made prenatally on ultrasound by fourth ventricle dilation that fills the posterior fossa and cerebellar vermis hypoplasia. In extremely rare cases, it can be associated with brainstem disconnection. In this condition, only a thin cord of tissue connects the superior and inferior portions of the brainstem.1 There exist only 14 known cases of brainstem disconnection.2 The vast majority were not diagnosed prenatally and were almost universally lethal in the months following delivery.3
Case Report: Here we describe a 15th case of brainstem disconnection. The patient was a 38-year-old G1P0 with an uncomplicated prenatal course until findings consistent with Dandy Walker malformation were noted on anatomy scan at 18 weeks. She presented for a second opinion with a maternal fetal medicine specialist and findings were confirmed with absent cerebellar vermis, enlarged cisterna magna, and severe ventriculomegaly. Amniocentesis with whole genome sequencing demonstrated no relevant abnormalities.
Final/Working Diagnosis: Fetal MRI revealed kinking of the brainstem and positioning at the level of the foramen magnum consistent with brainstem disconnection. This represents only the second known case to be diagnosed prenatally. The patient was counseled that, from the few known cases, outcomes are poor with the majority of neonates dying within days to months.2
Management/Outcome/Follow-up: Given the prognosis, the patient was referred to palliative care. After counseling by a multidisciplinary team, she elected comfort care. Close follow-up with serial ultrasounds demonstrated increasing fetal head size. This ultimately necessitated earlier delivery at 37 weeks as well as cephalocentesis, and classical Cesarean delivery. The neonate was found to have severe macrocephaly, ear underdevelopment, micrognathia, cleft lip, and hypotonicity. Unfortunately, the neonate died less than an hour after delivery.
Conclusion: Brainstem disconnection significantly worsens the prognosis of Dandy Walker malformation. The constellation of findings ultimately resulted in increased morbidity of delivery and neonatal death shortly thereafter. In this case, MRI provided the diagnosis of brainstem disconnection during the prenatal course. Unlike in previous cases, this allowed for multidisciplinary palliative care counseling which informed the patient’s decision for comfort care.
References and Resources
- Barkovich AJ, Millen KJ, Dobyns WB. A developmental and genetic classification for midbrain-hindbrain malformations. Brain. 2009;132(12):3199-3230. doi:10.1093/brain/awp247
- Vekemans M, Maurice P, Lachtar M, et al. Additional evidence for the vascular disruption defect hypothesis in a novel case of brainstem disconnection syndrome. Birth Defects Research. 2022;114(19):1298-1306. doi:10.1002/bdr2.2100
- Duffield C, Jocson J, Wootton-Gorges SL. Brainstem disconnection. Pediatric Radiology. 2009;39(12):1357-1360. doi:10.1007/s00247-009-1378-3
