Abstracts

Rationale: : Midbrain and hindbrain represent posterior fossa structures which comprise cerebellum, brainstem and related cerebrospinal fluid spaces. Developmental disorders affecting midbrain-hindbrain have been increasingly recognised during past two decades due to advances in neuroimaging. Midbrain-hindbrain malformations may occur as isolated abnormalities or as part of larger developmental disorders, yet large cohort data on their association with supratentorial cortical malformations, defining the clinical and imaging spectrum is lacking. The aims of this study were to investigate the spectrum of midbrain-hindbrain malformations in patients with supratentorial cortical malformations and epilepsy and to compare the clinical and imaging features of two groups of patients: those with supratentorial cortical malformations and midbrain-hindbrain malformations to those with supratentorial cortical malformations and without midbrain-hindbrain malformations. Methods: Two hundred and twenty patients (116 women, mean age 31 16.6, range 2-76) with supratentorial cortical malformations and epilepsy were identified at the Departments of Neurology and Pediatrics, Innsbruck Medical University, Austria. All underwent highresolution MRI (1.5-Tesla) between 2002 and 2008. Midbrain-hindbrain structures were visually assessed by three independent raters. Results: Midbrain-hindbrain malformations were seen in 17 %, 38/220 of patients (the most common was Dandy-Walker malformation - 32%, 12/38). Unilateral brainstem hypoplasia (21%, 8/38) was invariably associated with ipsilateral perisylvian polymicrogyria. No other significant associations between different midbrain-hindbrain malformations and supratentorial cortical malformations were observed. Patients with midbrain-hindbrain malformations had a higher rate of extensive bilateral supratentorial cortical malformations (63%, 24/38 vs. 36%, 66/182; p=0.004), dysgenesis of corpus callosum (26%, 10/38 vs. 4%, 7/182; p<0.001), hippocampal abnormalities (52%, 20/38 vs. 27%, 49/182; p=0.004), learning disability (71%, 27/38 vs. 38%, 70/182; p<0.001), delayed developmental milestones (68%, 26/38 vs. 35%, 63/182; p<0.001), as well as earlier age at seizure onset (mean 7.6 years vs. 9.5 years; p=0.043), compared to those without midbrain-hindbrain malformations