Focal seizures

Focal seizures are the transient occurrence of signs and/or symptoms due to abnormal excessive or synchronous neuronal activity in the brain originating within networks limited to one hemisphere.

Focal seizures can be caused by overt brain lesions (e.g., stroke, tumor), but neuroimaging studies often do not identify any underlying pathology.

History-taking is the most important aspect of diagnosis. Supportive tests, although helpful, need not be abnormal for a diagnosis of focal seizures.

Monotherapy with anticonvulsant medication is the initial and preferred treatment. Choice of medication should be tailored to the needs of the individual patient, taking into account factors such as age, sex, and comorbidities.

When at least two monotherapy trials fail to achieve seizure remission, dual therapy may be tried; use of drugs with different mechanisms of action should be considered to maximize efficacy and minimize toxicity.

Patients in whom seizure remission is not achieved with two monotherapy trials followed by dual therapy are considered to have refractory focal seizures. They should be evaluated to confirm the diagnosis and for consideration of resective epilepsy surgery and/or neuromodulation therapies.

Focal seizures (formerly known as partial seizures) refer to the electrical and clinical manifestations of seizures that arise from one portion of the brain. An electroencephalogram typically indicates a localized discharge over the area of onset, or regions beyond the initial onset as the abnormal electrical activity propagates. Focal seizures can originate from any lobe in the brain. Focal epilepsy of temporal lobe origin is the most frequently recognized focal epilepsy.

Focal aware seizures (formerly known as simple focal seizures) are those in which consciousness is preserved. Focal impaired awareness seizures (formerly known as complex focal seizures) are characterized by loss of awareness, memory loss for the clinical event, and impaired responsiveness at the time of the event.

Focal seizures may evolve into bilateral tonic-clonic seizures (formerly known as secondarily generalized tonic-clonic seizures). The clinical manifestations of a particular seizure depend on the clinically eloquent structures of the brain that are activated.[1]Fisher RS, Cross JH, French JA, et al. Operational classification of seizure types by the International League Against Epilepsy: position paper of the ILAE Commission for Classification and Terminology. Epilepsia. 2017 Apr;58(4):522-30. https://onlinelibrary.wiley.com/doi/full/10.1111/epi.13670 http://www.ncbi.nlm.nih.gov/pubmed/28276060?tool=bestpractice.com

The clinical definition of epilepsy includes any of the following conditions: 1) at least two unprovoked seizures occurring >24 hours apart; 2) one unprovoked seizure and a probability of further seizures similar to the general recurrence risk (at least 60%) after two unprovoked seizures, occurring over the next 10 years; 3) diagnosis of an epilepsy syndrome.[1]Fisher RS, Cross JH, French JA, et al. Operational classification of seizure types by the International League Against Epilepsy: position paper of the ILAE Commission for Classification and Terminology. Epilepsia. 2017 Apr;58(4):522-30. https://onlinelibrary.wiley.com/doi/full/10.1111/epi.13670 http://www.ncbi.nlm.nih.gov/pubmed/28276060?tool=bestpractice.com [2]Fisher RS, Acevedo C, Arzimanoglou A, et al. ILAE official report: a practical clinical definition of epilepsy. Epilepsia. 2014 Apr;55(4):475-82. https://onlinelibrary.wiley.com/doi/full/10.1111/epi.12550 http://www.ncbi.nlm.nih.gov/pubmed/24730690?tool=bestpractice.com