Generalized Onset Seizures Present with Bilateral Symptoms and Impaired Awareness
Yes, patients with generalized onset seizures typically present with bilateral symptoms and impaired awareness (loss of consciousness). According to the International League Against Epilepsy (ILAE) classification, generalized seizures rapidly affect both cerebral hemispheres and both sides of the body, causing bilateral symptoms and typically impaired awareness 1.
Characteristics of Generalized Onset Seizures
- Generalized seizures affect both hemispheres simultaneously at onset and cause bilateral symptoms 1
- They are subdivided into tonic-clonic, other motor, or nonmotor (absence) types 1
- Impaired awareness is a hallmark feature of generalized seizures, with complete loss of consciousness occurring when epileptic activity involves both cortical and subcortical structures 2
- Generalized seizures typically present with symmetrical, synchronous movements, unlike the asymmetrical movements often seen in syncope 1
Clinical Manifestations of Impaired Awareness
- Eyes are typically open during unconsciousness in generalized seizures, whereas they are often closed in psychogenic non-epileptic seizures (PNES) 1
- Oral automatisms such as chewing, smacking, and blinking may be observed 1
- Cyanotic face is common in epileptic seizures and cardiac syncope 1
- Duration of loss of consciousness (LOC) is typically longer in epileptic seizures (mean 74-90 seconds) compared to syncope (typically <30 seconds) 1
- Stertorous (snoring) breathing is more common in epileptic seizures than in PNES 1
Differentiating Features from Other Conditions
- Tongue biting, especially on the lateral side, is more common in epileptic seizures than syncope 1
- Urinary incontinence does not reliably differentiate epileptic seizures from syncope 1
- Head turning is typically prolonged in epileptic seizures compared to syncope with deep hypoperfusion (<30 seconds) 1
- Many movements ("100", "cannot count") are more suggestive of epilepsy than syncope, which typically has fewer movements 1
Special Considerations
- While generalized seizures typically present with impaired awareness, rare exceptions exist. There have been documented cases of bilateral clonic or tonic-clonic seizures with retained consciousness, though these are uncommon and may be misdiagnosed as pseudoseizures 3
- The subjective experience of consciousness during seizures exists on a continuum rather than distinct levels, with focal to bilateral tonic-clonic and generalized tonic-clonic seizures most frequently associated with descriptions of total loss of consciousness 4
- In absence seizures (a type of generalized seizure), there is typically brief impairment of awareness with 3 Hz spike-wave discharges on EEG 5
Pathophysiological Mechanism
- Loss of consciousness in generalized seizures occurs when epileptic activity involves both cortical and subcortical structures 2
- Involvement of the bilateral thalamus and upper brainstem leads to selective impairment of frontoparietal association cortices and midline 'default mode' networks, resulting in ictal loss of consciousness 2
- Unlike focal impaired awareness seizures where slow-wave activity increases, generalized seizures show paradoxical decreases in slow-wave activity and increases in high-gamma activity in certain brain regions 6
Remember that accurate classification of seizure types is crucial for appropriate treatment, accurate prognosis, and effective communication among healthcare providers 1.