Jacksonian seizures
| Focal seizure | |
|---|---|
| Classification and external resources | |
| Specialty | neurology |
| ICD-10 | G40.0-G40.2 |
| ICD-9-CM | 345.4-345.5 |
| MedlinePlus | 000697 |
| MeSH | D004828 |
Focal seizures (also called partial seizures and localized seizures) are seizures which affect initially only one hemisphere of the brain. The brain is divided into two hemispheres, each consisting of four lobes – the frontal, temporal, parietal and occipital lobes. In partial seizures the seizure is generated in and affects just one part of the brain – the whole hemisphere or part of a lobe. Symptoms will vary according to where the seizure occurs. In the frontal lobe symptoms may include a wave-like sensation in the head; in the temporal lobe, a feeling of déjà vu; in the parietal lobe, a numbness or tingling; and in the occipital lobe, visual disturbance or hallucination.
Focal seizures are split into two main categories; simple focal seizures and complex focal seizures.
In simple focal seizures a small part of one of the lobes may be affected and the person remains conscious. This will often be a precursor to a larger seizure such as a complex partial seizure. When this is the case, the simple partial seizure is usually called an aura.
A complex focal seizure affects a larger part of the hemisphere than a simple partial seizure and the person may lose consciousness.
If a focal seizure spreads from one hemisphere to the other side of the brain, this will give rise to a secondarily generalised seizure. The person will become unconscious and may well have a tonic clonic seizure. When people have multiple focal seizures they generally have a condition known as temporal lobe epilepsy.
Simple focal seizures are seizures which affect only a small region of the brain, often the temporal lobes or hippocampi. People who have simple partial seizures retain consciousness. Simple partial seizures often precede larger seizures, where the abnormal electrical activity spreads to a larger area of (or all of) the brain, usually resulting in a complex partial seizure or a tonic-clonic seizure.
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