Clinical Presentation And Classification Of Cerebral Cortical Malformations By Stages Of Cortical Development

The process of brain development, which follows a sequence that is under genetic regulation, provides a framework for understanding the variety of cerebral cortical malformations encountered in patients with pedi-atric epilepsy. The classification presented by Barkovich and colleagues has evolved to include an ever-expanding list of genetic etiologies for many cerebral malformations (1, 19, 66). The importance of its emphasis on genetic causes cannot be overstated; even when epilepsy is not the presenting symptom of a cerebral malformation, clinicians must address important questions regarding possible genetic etiologies. Table 6-3 presents the major categories of malformations of cortical development according to the stage that is thought to be first or primarily disrupted in brain development.

We begin this section with some general clinical observations regarding patients with epilepsy caused by cerebral cortical malformations. We briefly review the normal sequence of cortical development before discussing representative examples from each major group according to the first stage of brain development known or thought to be disrupted.

General Clinical Observations

The focus of this chapter is the relationship between malformations of cortical development and epilepsy, so we provide estimates of the prevalence of epilepsy among patients with specific malformations when this information is available. In general, though the prevalence of epilepsy in each group is not 100 percent, we recommend advising patients with cerebral cortical malformations and their families that epilepsy is a common symptom of any structural brain malformation.

Apart from the minority of patients with cerebral cortical malformations who are asymptomatic, many patients with malformations of cortical development have what some clinicians term a "chronic static encephalopathy,"

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