Generalized Onset Seizures and Impaired Awareness
No, not all patients with generalized onset seizures present with impaired awareness, as some generalized seizures can occur with preserved awareness depending on the specific seizure type and individual patient factors.
Types of Generalized Seizures and Their Relationship to Awareness
Generalized seizures involve both cerebral hemispheres from the onset and can be categorized into different types with varying effects on consciousness:
Generalized seizures are classified as motor and non-motor (absence) seizures according to the International League Against Epilepsy classification system 1
Typical absence seizures are characterized by brief episodes with impairment of awareness and associated with 3 Hz spike-wave discharges on EEG 2
Some generalized seizures, particularly myoclonic seizures, may occur without significant impairment of awareness 3
Tonic-absence seizures represent a specific seizure type where a tonic phase with generalized paroxysmal fast activity is followed by an absence phase with impaired awareness 4
Factors Affecting Awareness in Seizures
The level of awareness impairment during seizures can vary based on several factors:
Impaired consciousness in absence seizures is not monolithic but varies in severity between patients and even between episodes in the same patient 5
Some aspects of consciousness may be more severely affected than others during seizures, suggesting focal rather than generalized disruption of brain functions 5
The depth of consciousness impairment can differ between seizure types, with focal to bilateral tonic-clonic seizures often causing deeper loss of consciousness than focal impaired awareness seizures 6
Clinical Presentation and Assessment
When evaluating patients with generalized seizures, clinicians should consider:
Motor manifestations can include bilateral tonic-clonic movements, while non-motor manifestations may include staring spells indicating impaired awareness 1
The duration of impaired awareness can vary significantly, from brief episodes in typical absence seizures to more prolonged periods in complex seizure types 4
EEG findings are crucial for diagnosis, with generalized seizures typically showing bilateral, synchronous discharges 3
Diagnostic Considerations
Proper diagnostic workup for patients with generalized seizures includes:
MRI is the preferred neuroimaging modality when imaging is indicated, though it is rarely needed in neurologically normal patients with typical generalized seizures due to their genetic underpinnings 3
EEG is recommended as part of the neurodiagnostic evaluation, particularly to differentiate between generalized and focal seizures 3
Laboratory tests should be ordered based on individual clinical circumstances, especially if there are suggestive findings of metabolic disturbances 3
Special Populations and Considerations
Certain patient populations require special attention:
In patients with 22q11.2 deletion syndrome, seizures can be of various types, including generalized tonic-clonic, typical or atypical absences, myoclonic, or focal with preserved or impaired awareness 3
IQSEC2-related epilepsy can present with different seizure types across age ranges, including focal onset seizures with impaired awareness and generalized motor seizures 7
The frequency of recurrence for focal seizures (up to 94%) is considerably higher than for generalized seizures (approximately 72%), which may influence management decisions 3
Common Pitfalls and Caveats
Important considerations to avoid misdiagnosis or improper management:
Not all generalized seizures cause impaired awareness, and the degree of impairment can vary significantly between seizure types and individual patients 5
Seizure classification should be based on clinical presentation, EEG findings, and response to treatment rather than assumptions about awareness 3
Focal seizures with secondary generalization (now termed "focal to bilateral tonic-clonic") should not be confused with primary generalized seizures, as they have different mechanisms and treatment implications 3
Absence seizures specifically lead to selective deficits in consciousness with relatively little motor manifestations, making them a unique subtype of generalized seizures 5