Cerebral Abnormalities in Spina Bifida: A Neuropathological Study.

INTRODUCTION: Spina bifida (SB) is the most common neural tube defect in humans. Here, we analyzed systematically the neuropathological findings of the brain in SB cases. METHODS: 79 cases with SB aperta (SBA) and 6 cases with SB occulta (SBO) autopsied at the Charité Neuropathology from 1974 to 2000 were re-evaluated retrospectively. For this, case files and spinal cord as well as brain sections were studied. RESULTS: While no brain malformations were detected in SBO cases, 95% of SBA cases had brain malformations. Main brain anomalies identified were hydrocephalus (71%), Chiari II malformation (36%), heterotopia (34%), other cerebellar anomalies (36%), gyrification defects (33%), and ependymal denudation (29%). Hydrocephalus was observed as early as gestational week 17 and was highly associated to Chiari II and ependymal denudation. In 55% SBA was accompanied by further anomalies not primarily affecting the CNS. CONCLUSION: We confirm using neuropathologic methods brain malformations in most SBA but none in SBO cases. In addition to our previous radiologic study, we now demonstrate the high prevalence of cerebellar malformations and cerebral heterotopias in SBA. The early detection of hydrocephalus and Chiari II malformation in fetuses raises the question whether these arise parallel rather than in strict temporal sequence.

Systematic Classification of Spina Bifida.

Spina bifida (SB) is an umbrella term for multiple conditions characterized by misclosure of vertebral arches. Neuropathologic findings in SB cases are often reported with imprecise and overlapping terminology. In view of the increasing identification of SB-associated genes and pathomechanisms, the precise description of SB subtypes is highly important. In particular, the term "myelomeningocele" is applied to various and divergent SB subtypes. We reevaluated 90 cases with SB (58 prenatal; 32 postnatal). The most frequent SB phenotype in our cohort was myeloschisis, which is characterized by an open neural plate with exposed ependyma (n = 28; 31.1%). An open neural plate was initially described in only in two-thirds of the myeloschisis cases. An additional 21 cases (23.3%) had myelomeningocele; 2 cases (2.2%) had a meningocele; and 21 cases (23.3%) had an unspecified SB aperta (SBA) subtype. Overall, the SB phenotype was corrected in about one-third of the cases. Our findings highlight that "myelomeningocele" and "SB aperta" cannot be used as synonymous terms and that myeloschisis is an underreported SB phenotype. Based on our findings and a review of literature we propose a classification of SB subtypes in SB occulta and the 3 SBA subtypes, meningocele, myelomeningocele, and myeloschisis.