Seizures are sudden periodic attacks or spasms (also referred to as paroxysmal events) that are produced by abnormal electrical discharges in the brain. They can result in sudden brief attacks that may alter consciousness, motor activity or sensory experience. Any recurrent pattern of seizures is considered epilepsy. Epilepsy can be due to a large variety of insults to the brain including structural abnormalities such as space-occupying lesions (e.g., tumors or vascular malformations), lesions caused by head trauma and pathological processes of unknown etiology.
It is reported that approximately 2% of the U.S. population will experience at least one seizure during the course of a lifetime and that 1% of the population will be diagnosed with epilepsy. The incidence for seizures tends to peak during early childhood and again in late adulthood (over age 75). The the likelihood of having additional seizures in a person who has had one seizure of unknown origin (may be referred to as idiopathic or cryptogenic seizures) ranges between 30% & 50%. The recurrence of seizures when their origin is known (e.g., brain tumor or other lesion) tends to be over 50%.
Seizures can be classified into two primary types: Generalized and Partial. Generalized seizures account for approximately 1/3 of all patients with epilepsy. This type of seizure originates in the deep structures of the brain including the brain stem and thalamus. In generalized seizures the individual does not experience any psychic or sensory phenomena at the start of the seizure (aura) and there are no focal motor behaviors caused by the seizure. Generalized seizures can be further divide into those with motor activity (e.g., tonic or clonic) and absence seizures, which occur during childhood, usually between ages 4 and 12 years and tend not to persist into adulthood. These seizures are usually brief in length, lasting 5 to 30 seconds and involve staring spells and a characteristic EEG profile.
Partial seizures, whether simple or complex, occur in 2/3 of the population diagnosed with epilepsy. Partial seizures begin in one part of the brain and may or may not spread to other parts. Unlike generalized seizures, partial seizures include specific motor, sensory and psychic phenomena. The most common signs to look for include stereotyped, repetitive movements such as lip smacking, chewing and eye blinking. These seizures most often originate from one or both temporal lobes, specifically from the hippocampus and amygdala, which are involved in memory and emotional functioning. As such, these seizures are often accompanied by emotional changes such as fear, sadness, pleasure or deja vu. Hallucinations that can involve auditory, visual or olfactory phenomena may also occur.
Partial seizures may be either simple or complex. In simple seizures there are no alterations in consciousness. Complex seizures result in impaired consciousness directly as a result of the seizure discharge. When the localized electrical discharge spreads to other areas of the brain it can result in a secondarily generalized seizure.
Temporal Lobe Epilepsy (TLE) is thought to occur in 25% of children and approximately 50% of adults with known seizure disorders. In 80% of TLE cases an aura precedes onset of the seizure. Furthermore, because of the specific functions associated with the temporal lobes (e.g., memory, emotion, hearing, taste and smell) specific sensory phenomena, including hallucinatory experiences and memory problems have been noted.
The impact that seizures have on the brain and its ability to perform its job properly is complex. The purpose of the neuropsychological evaluation is to provide an understanding of the impact that the seizures are having on the person including: 1) providing a detailed account of the person’s cognitive strengths and weaknesses; 2) helping to lateralize (left vs. right hemisphere) and localize (based on type of functional impairment) dysfunctional brain regions; 3) identification of presurgical candidates who are likely to suffer debilitating functional impairment following surgery; & 4) the scope and type of services, neurological, psychological and academic that are likely to be helpful to the individual.
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