Brain Stem Disconnection: Two Additional Patients and Expansion of the Phenotype
Introduction: Brain stem disconnection (BD) is a rare posterior fossa abnormality defined by the nearly complete absence of a brain stem segment with the rostral and caudal brain stem portions connected only by a thin cord of tissue. BD has a poor outcome and the majority of children die within the first 2 months of life without achieving developmental milestones. Only 12 children with BD have been reported so far. We report the case of two new patients with BD and a prolonged spontaneous survival to expand the phenotype.
Case Report: In both the children, neuroimaging findings included discontinuity between the upper pons and the medulla and vermian hypoplasia. Neither patient required intubation or mechanical ventilation and each survived longer than 2 months (patient 1 died at 8 months and patient 2 is alive at 4.5 years). Patient 1 is the only child with BD reported so far who achieved some developmental milestones. At the age of 8 months, he was able to hold brief fixation, smiled, looked at an object at near distance, and reached for it. He brought his hands to his mouth and showed some emerging reaching skills. In both the children, temperature instability and seizures were recognized, and extracerebral involvement including hydronephrosis and left ectopic ureter in patient 1 and VACTERL association in patient 2. Whole-exome sequencing in patient 1 and array CGH in patient 2 did not show causative genetic anomalies causative for BD.
Conclusion: Although the long-term neurodevelopmental outcome of BD remains unfavorable, the expansion of the phenotypic spectrum may be important in terms of counseling. The pathogenesis (malformative vs. disruptive) of BD remains unknown.
Keywords: brain stem, MRI, malformation, disruption.