A Case Report of Mega Cisterna Magna with Extra-cranial Features of Dandy-Walker Malformation in an Adult: Implications for the Dandy-Walker Complex Continuum.

Posterior fossa malformations are rare cyst-like pathologies of the central nervous system. Outcomes of patients with these conditions are largely documented in fetal or early childhood studies as most cases are non-compatible with life. Also, different schemes to categorize these occurrences have been proposed. One classification puts forth that the entities are a continuum of pathologies, called the Dandy Walker Complex, wherein Mega Cisterna Magna is the most benign to Dandy Walker Malformation as the most severe form. We report the first case of a patient with a mixed presentation of Mega Cisterna Magna having extracranial manifestations of Dandy Walker Malformation reaching her adult years. The patient is a 26-year-old female who was apparently well until she presented with recurrent headache and seizure episodes of 2-year duration. She had an unremarkable birth and childhood history, apart from learning difficulties in school. In her adult years, she gave birth to an infant with multiple physical anomalies. She has a maternal uncle with abnormal facie and intellectual disability. Physical examination of the patient exhibited a bulging occiput, hypertelorism, down-slanting palpebral fissures, large globular nose, large ear lobules, high arched palate, and clinodactyly. Neurologic examination was unremarkable. Magnetic resonance imaging confirmed Mega Cisterna Magna and was deemed non-surgical. She remained seizure-free during admission as well as on follow-up, maintained on Phenytoin. The existence of a Dandy-Walker continuum is still debated, as the link among the disease entities are yet to be established using developmental or genetic studies. This case, however, supports the Dandy-Walker Complex classification by demonstrating a rare combination of Mega Cisterna Magna with features of Dandy-Walker Malformation in an adult. This can contribute to disease definition and eventually to the discovery of the pathobiological mechanisms of posterior fossa cysts, and to appropriate diagnosis and management.