mirror focus
Secondary epileptic focus that develops in the hemisphere opposite to an established primary focus.
Full Definition
A mirror focus is a secondary epileptogenic region that develops in the brain hemisphere contralateral to an established primary epileptic focus, typically in homologous cortical areas. This phenomenon occurs through trans-callosal kindling mechanisms, where repeated seizure activity from the primary focus gradually induces epileptogenesis in corresponding regions of the opposite hemisphere. Mirror foci are particularly concerning in epilepsy surgery candidates because they may continue to generate seizures even after successful resection of the primary focus. Their identification through prolonged EEG monitoring is crucial for surgical planning and outcome prediction.
Usage
Usage note: Two words; implies secondary development rather than independent bilateral foci.
In Context
- "Long-term monitoring revealed development of a mirror focus in the right temporal lobe." — Pre-surgical evaluation
- "The presence of a mirror focus complicated surgical decision-making in this patient." — Multidisciplinary conference note