Focal seizures are usually seen, with features referable to the location of the heterotopia. They may be frequent and fail to respond to medication. If these do not have motor features, they may be difficult to detect in infants.
Focal to bilateral tonic-clonic seizures can occur, these may have focal features referable to the location of the grey matter heterotopia if this information is carefully sought.
Epileptic spasms can occur and may be the presenting seizure type, these may have focal features that are referable to the location of the heterotopia.
Status epilepticus, including focal status epilepticus, can occur.
CAUTION patients with heterotopia, who have earlier age of seizure onset, may have a change in their seizure types over time, with the emergence of epileptic spasms or generalized seizure types, such as atypical absence, atonic and tonic seizures. Developmental and cognitive impairments are more common in this group. If these seizure types are seen, and if seizure control is not achieved with medication, epilepsy surgery may be considered if the region of heterotopia is localized.