Epilepsy is a chronic disease of disturbed electrical activity in the brain, resulting in recurrent seizures with or without convulsions. Epilepsy is a disorder with profound impact on lifestyle and patients are often dependent upon caregivers to assist with medications and transportation. All states impose limitations on driving for individuals who have recently had a seizure with impaired consciousness.
The pathophysiology of a seizure is due to an unstable cell membrane in the gray matter of the brain. The cause of the unstable cell membrane has been linked to three causes: an abnormality in potassium conductance, an abnormality in voltage-sensitive ion channels, or a deficiency in membrane ATPases linked to ion transport. Excitatory neurotransmitters (glutamate, aspartate, acetylcholine, norepinephrine) enhance the propagation of seizures while inhibitory neurotransmitters (gamma-aminobutyric acid [GABA], dopamine) decrease the propagation of seizure activity in the brain. The spread can be local (partial seizure) or throughout the entire brain (generalized seizure). The different types of epilepsies are due to the different pathophysiologic abnormalities.
Epilepsy is classified by the seizure presentation (Table 53-1). The classification system is based on how the seizure begins; therefore, obtaining an adequate description from a third party is important. The classifications of epilepsy are:
Absence seizures (petit mal)—sudden interruption of activities and a blank stare.
Myoclonic seizures—brief shock-like contraction of a muscle group.
Clonic seizures—jerking motion while tonic seizures involve a sustained muscle contraction.
Tonic-clonic seizures (grand mal)—alternating muscle contraction and jerking.
Atonic seizures involve a sudden loss of muscle tone known as drop attacks.
TABLE 53-1Classification and Management of Seizure Disorders ||Download (.pdf) TABLE 53-1Classification and Management of Seizure Disorders
|Seizure Type ||Features ||Conventional Antiseizure Drugs ||Recently Developed Antiseizure Drugs |
|Partial Seizures |
|Simple partial ||Diverse manifestations determined by the region of cortex activated by the seizure (eg, if motor cortex representing left thumb, clonic jerking of left thumb results; if somatosensory cortex representing left thumb, paresthesia of left thumb results), lasting approximating 20-60 s. Key feature is preservation of consciousness. ||Carbamazepine, phenytoin, valproate || |
|Complex partial ||Impaired consciousness lasting 30 s to 2 min, often associated with purposeless movements such as lip smacking or hand wringing. || ||Gabapentin, lacosamide, lamotrigine, levetiracetam, rufinamide, tiagabine, topiramate, zonisamide |
|Partial with secondarily generalized tonic-clonic seizure ||Simple or complex partial seizure evolves into a tonic-clonic seizure with loss of consciousness and sustained contractions (tonic) of muscles throughout the body followed by periods of muscle contraction alternating with periods of relaxation (clonic), typically lasting 1-2 min. ||Carbamazepine, phenobarbital, phenytoin, primidone, valproate || |
|Generalized Seizures |
|Absence seizure ||Abrupt onset of impaired consciousness associated with staring and cessation of ongoing activities typically lasting less than 30 s. ||Ethosuximide, valproate, clonazepam ||Lamotrigine |
|Myoclonic seizure ||A brief (perhaps a second), shock-like contraction of muscles that may be restricted to part of one extremity or may be generalized. ||Valproate, clonazepam...|