Cerebrocortical microdysgenesis is enhanced in c57BL/6J mice exposed in utero to acetazolamide

Divergence and inheritance of neocortical heterotopia in inbred and genetically-engineered mice

Cortical function emerges from the intrinsic properties of neocortical neurons and their synaptic connections within and across lamina. Neurodevelopmental disorders affecting migration and lamination of the neocortex result in cognitive delay/disability and epilepsy. Molecular layer heterotopia (MLH), a dysplasia characterized by over-migration of neurons into layer I, are associated with cognitive deficits and neuronal hyperexcitability in humans and mice. The breadth of different inbred mouse strains that exhibit MLH and inheritance patterns of heterotopia remain unknown. A neuroanatomical survey of numerous different inbred mouse strains, 2 first filial generation (F1) hybrids, and one consomic strain (C57BL/6J-Chr 1^A/J/NaJ) revealed MLH only in C57BL/6 mice and the consomic strain. Heterotopia were observed in numerous genetically-engineered mouse lines on a congenic C57BL/6 background. These data indicate that heterotopia formation is a weakly penetrant trait requiring homozygosity of one or more C57BL/6 alleles outside of chromosome 1. These data are relevant toward understanding neocortical development and disorders affecting neocortical lamination.

Neocortical molecular layer heterotopia in substrains of C57BL/6 and C57BL/10 mice

Abnormal development of the neocortex is often associated with cognitive deficits and epilepsy. Rodent models are widely used to study normal and abnormal cortical development and have revealed the roles of many important genetic and environmental factors. Interestingly, several inbred mouse strains commonly used in behavioral, anatomical, and/or physiological studies display neocortical malformations including C57BL/6J mice, which are among the most widely utilized mice. In the present report we describe the prevalence and cytoarchitecture of molecular-layer heterotopia in C57BL/6J mice and related strains obtained from three commercial vendors as well as mice bred in academic vivaria from founders obtained commercially. In particular, we found that the prevalence of molecular-layer heterotopia vaired according to the sex as well as the vendor-of-origin of the mouse. These data are relevant to the use of this strain as a mouse-model in the study of brain-behavior relationships.

Cytoarchitecture and transcriptional profiles of neocortical malformations in inbred mice

Malformations of neocortical development are associated with cognitive dysfunction and increased susceptibility to epileptogenesis. Rodent models are widely used to study neocortical malformations and have revealed important genetic and environmental mechanisms that contribute to neocortical development. Interestingly, several inbred mice strains commonly used in behavioral, anatomical, and/or physiological studies display neocortical malformations. In the present report we examine the cytoarchitecture and myeloarchitecture of the neocortex of 11 inbred mouse strains and identified malformations of cortical development, including molecular layer heterotopia, in all but one strain. We used in silico methods to confirm our observations and determined the transcriptional profiles of cells found within heterotopia. These data indicate cellular and transcriptional diversity present in cells in malformations. Furthermore, the presence of dysplasia in nearly every inbred strain examined suggests that malformations of neocortical development are a common feature in the neocortex of inbred mice.

Idiopathic intracranial hypertension

OBJECTIVE

The history, diagnosis, and therapy of idiopathic intracranial hypertension (IIH) (pseudotumor cerebri) are reviewed. Theories of pathogenesis are considered, the clinical presentation is described, and potential diagnostic and therapeutic challenges are explored.

METHODS

An extensive literature review of IIH and related conditions (secondary pseudotumor syndromes) was performed. The history of and rationale for the diagnosis and medical and surgical approaches to treatment are reviewed. Available outcome studies are presented.

RESULTS

Diagnosis of IIH requires that the modified Dandy criteria be satisfied. Multiple potential contributing causes of intracranial hypertension must be identified or excluded. The clinical presentation most often includes headaches and papilledema, but many other findings have been described. The most important goal of therapy is to prevent or arrest progressive visual loss. Medical therapies include alleviation of associated systemic diseases, discontinuation of contributing medications, provision of carbonic anhydrase inhibitors, and weight loss. Surgical therapies include lumboperitoneal shunting, ventriculoperitoneal shunting, and optic nerve sheath fenestration. On the basis of the advantages and disadvantages of these treatment modalities, a suggested treatment paradigm is presented.

CONCLUSION

Idiopathic intracranial hypertension is the term to be adopted instead of pseudotumor cerebri. IIH remains an enigmatic diagnosis of exclusion. However, prompt diagnosis and thorough evaluation and treatment are crucial for preventing visual loss and improving associated symptoms.