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Focal cortical dysplasias (FCD) are localized regions of malformed cerebral cortex. They are a common cause of focal seizures. They are classified by their neuropathological features.

  • FCD Type I refers to isolated lesions, which present either as radial (FCD Type Ia) or tangential (FCD Type Ib) dyslamination of the cortex, that may be identified in one or multiple lobes of the brain.
  • FCD Type II is an isolated lesion characterized by cortical dyslamination and dysmorphic neurons without (Type IIa) or with balloon cells (Type IIb).
  • FCD Type III describes FCD that occurs in combination with hippocampal sclerosis (FCD Type IIIa), with glioneuronal tumors (FCD Type IIIb), adjacent to vascular malformations (FCD Type IIIc) or in association with lesions acquired in early life, such as a previous ischemic injury (FCD Type IIId).

Clinical context

The clinical presentation of focal cortical dysplasia depends on the extent and location of the malformation, and co-occurring structural abnormalities. Unless the area of focal cortical dysplasia is large, patients do not initially suffer from significant developmental, neurological or cognitive impairment. Onset of seizures can be at any age, with two thirds having seizure onset by 5 years of age and most patients having seizure onset by 16 years. Older age of onset is rarely seen. While around one fifth of patients may show transient responsiveness to medication (seizure freedom for one year or more), seizures are usually difficult to control with medication (seen in around 80% of patients). Both sexes may be affected.

CAUTION developmental and cognitive outcome may be worse in children with uncontrolled seizures in early life, especially if epileptic spasms or generalized seizure types appear, therefore proactive seizure control is important, this may include epilepsy surgery, if seizures are not controlled with medication.

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