Complications
Prevalence of severe cognitive impairment is >90% in Lennox-Gastaut syndrome and >50% in epilepsy with myoclonic absences. The exact mechanism of epileptic encephalopathy is poorly understood. All types of absence seizure, including childhood absence epilepsy (CAE), have been associated with learning disability, attention deficit hyperactivity disorder (ADHD), and developmental delay.[84][85]
The presence of learning disability or cognitive impairment at time of diagnosis is predictive of this complication.[86] The presence of absence seizure at time of the first recognized seizure increases risk for cognitive difficulties compared with other seizure types at epilepsy onset.[87] Results from a very small study suggest that seizure control with medication may improve cognitive function.[88] In a large cohort of patients with CAE, high rate of attentional deficits were reported pretreatment.[89] These deficits persisted post-treatment at 16 to 20 weeks, regardless of seizure freedom. Valproic acid was associated with more significant attentional deficits than ethosuximide or lamotrigine.[89]
Approximately 50% of all patients with absence seizures also have GTC seizures.[83] This varies significantly between epilepsy syndromes, with essentially all juvenile myoclonic epilepsy patients having GTC seizures, compared with 30% or fewer patients with childhood absence epilepsy.
Treatment with valproic acid, lamotrigine, topiramate, or zonisamide is indicated, with a goal of seizure elimination.
Standard practice in the US is to only prescribe valproate-containing medicines if alternative medications are not acceptable or not effective. If the patient is taking the drug to prevent major seizures and is planning to become pregnant, the decision to continue valproate or to switch to an alternative agent should be made on an individual basis.
In 2018, the European Medicines Agency affirmed that valproate-containing medicines must not be used during pregnancy, unless no other effective treatment is available. Woman for whom there is no suitable alternative treatment to valproate are subject to specialist care, support, and counseling. In both Europe and the US, valproate and its analogs must not be used in female patients of childbearing potential unless there is a pregnancy prevention program in place and certain conditions are met.[69]
In general, patients with epilepsy are at increased risk for accidental injuries. One 24-month prospective case-controlled study reported a 27% risk of accident among patients with idiopathic, cryptogenic, or remote symptomatic epilepsy, compared with a 17% risk in matched controls.[80] The majority of accidents were seizure related.
The most concerning injuries are submersion injuries, burns, fractures, head injuries, soft-tissue injuries, dental injuries, and motor vehicle accidents.[81] In general, these would be expected to be less frequent with absence seizures than with other types of seizures.
Absence (nonconvulsive) status epilepticus may occur in 5.8% to 9.4% of patients with childhood absence epilepsy (CAE), 20% with juvenile absence epilepsy (JAE), and 6.7% with juvenile myoclonic epilepsy (JME).[82] Tonic-clonic status epilepticus is exceedingly rare.[82]
Similar provocative factors are attributed to status epilepticus as breakthrough seizures: for example, sleep deprivation. It should be treated with benzodiazepines such as intravenous lorazepam or rectal diazepam. If unresponsive after a number of treatments, loading with a medication such as valproate rather than phenytoin or phenobarbital should be considered, due to the risk of worsening absence status epilepticus.
Death occurs in the setting of status epilepticus in approximately 1% of all epilepsy patients. Sudden unexpected death in epilepsy (SUDEP) has been reported as a cause of death in 1 in 4500 children. The major risk factor for SUDEP is the occurrence of generalized tonic-clonic seizures.[76]
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