Likelihood of Absence Seizures Developing into Generalized Seizures in Adults
Absence seizures in adults have a significant risk of evolving into generalized tonic-clonic seizures, with studies showing this progression occurs in approximately 50-60% of adult patients with absence seizures. 1
Characteristics of Absence Seizures in Adults
Absence seizures are brief (seconds) generalized seizures characterized by:
- Sudden onset and termination
- Impairment of consciousness (which may range from severe to mild)
- Generalized 3-4Hz spike/polyspike and slow wave discharges on EEG 2
Unlike childhood absence epilepsy, absence seizures in adults:
- Often coexist with other seizure types
- May begin in adulthood or continue from childhood/adolescence 3
- Are frequently unrecognized or misdiagnosed as complex partial seizures 4
Risk of Progression to Generalized Seizures
The risk of progression from absence to generalized tonic-clonic seizures is substantial in adults:
- In a study of patients with idiopathic generalized epilepsy, all subjects had recorded seizures that began as typical absence seizures (clinically and electrographically) and evolved into generalized tonic-clonic activity 1
- Approximately 20 out of 23 adult patients (87%) with typical absences also experienced generalized tonic-clonic seizures 4
- Adults with absence seizures are more likely to have poor seizure control compared to children 5
Risk Factors for Progression
Several factors increase the likelihood of absence seizures evolving into generalized seizures:
- Untreated or undertreated absence seizures
- Presence of myoclonic components during absence seizures 5
- Female gender (absence status with progression to generalized seizures appears more common in women) 1
- Focal EEG abnormalities, particularly those with frontal accentuation 5
- Certain epilepsy syndromes (e.g., juvenile myoclonic epilepsy) 2
Clinical Implications
The high risk of progression has important clinical implications:
- Adults with absence seizures require thorough evaluation including EEG and neuroimaging 6
- Treatment should be initiated promptly to prevent progression to generalized seizures
- Valproic acid is often effective, controlling absences in approximately 75% of patients and generalized tonic-clonic seizures in 70% 2
- Alternative treatments include ethosuximide (for absence seizures only) and lamotrigine (which may control both absence and generalized tonic-clonic seizures) 2
Special Considerations
- Absence status epilepticus occurs in approximately 30% of patients with absence seizures 2
- Adults with absence seizures may have focal EEG abnormalities that could be misinterpreted as indicating partial seizures 4
- Seizure threshold may be lowered by various factors including hypocalcemia, hypomagnesemia, and certain medications 6
In conclusion, absence seizures in adults represent a significant risk for progression to generalized tonic-clonic seizures. Early recognition, proper classification, and appropriate treatment are essential to prevent this progression and improve outcomes.