Hemispheric malformations of cortical development: surgical indications and approach

The term "hemispheric malformation of cortical development" (MCD) has come into the medical lexicon in the past 20 years as improvements and availability of advanced imaging techniques have permitted more precise diagnosis of a variety of brain developmental disorders that affect large regions of brain. These conditions are united by their propensity to elicit seizures that are difficult to control with medication in the children who suffer them.

The goal of surgical intervention is always to achieve seizure freedom and thereby give the affected child the best possible hope for neurological development. Even when seizure freedom cannot be achieved, a reduction in seizure burden is necessary to permit the survival of the child in many cases of MCD.

A presurgical evaluation of a patient presenting with severe epilepsy and a possible hemispheric malformation can be divided into three stages. The first includes an evaluation of available imaging, clinical, and genetic data to accurately diagnose the child and help determine if surgical intervention is an option. The next includes an evaluation of EEG and neurological data, although this has limited utility in many clinical circumstances. Finally, a clinical team must decide upon an appropriate surgical strategy among a variety of options.

In this review, we will examine the set of diagnoses and associated imaging characteristics that describe the set of conditions for which surgical intervention is a possibility. We include a discussion of available surgical options, describing our own experience with surgery for MCD and the associated postoperative considerations including rates of seizure freedom, considerations for reoperation, and hydrocephalus.