A seizure is the result of an impulsive burst of excess electrical activity in the brain. This causes the brain's messages to become momentarily halted or mixed up. The type of seizure a person has depends on the area of the brain where this activity occurs.
Seizure types are organized firstly according to whether the source of the seizure within the brain is localized (partial or focal onset seizures) or distributed (generalized seizures). Partial seizures are further divided on the extent to which consciousness is affected. If it is unaffected, then it is a simple partial seizure; otherwise it is a complex partial seizure. A partial seizure may spread within the brain - a process known as secondary generalisation. Generalized seizures are divided according to the effect on the body but all involve loss of consciousness. These include absence (petit mal), myoclonic, clonic, tonic,general tonic-clonic (grand mal), and atonic seizures.
Epileptic seizures are classed as partial or generalised. Partial seizures involve part of the brain, while generalised seizures involve the whole brain. It is possible for partial seizures to become generalised seizures if the epileptic activity spreads to the whole brain.
Because there are so many different seizure types and symptoms, epilepsy can be a difficult condition to diagnose. Some people may go for years without being given a correct diagnosis of epilepsy. It is possible for some people to be misdiagnosed with epilepsy.
