This type of seizure begins similarly to FAS or FIAS, originating in a specific area of one of the brain’s hemispheres. However, if the epileptic activity spreads to most of the brain, the seizure typically results in impaired consciousness and other symptoms resembling a generalized seizure. The older term for these seizures is “secondarily generalized seizures.”
In FBTCS (Focal to Bilateral Tonic-Clonic Seizure), the first tonic phase of the seizure involves the patient losing consciousness, stiffening, often letting out a cry, collapsing, and sometimes biting their tongue. Due to the spasm of respiratory muscles, breathing temporarily stops, and the patient turns pale. The upper and lower limbs become symmetrically extended (lasting 3–30 seconds).
The seizure then transitions into the clonic phase, characterized by symmetrical, rhythmic jerking movements of the limbs, lasting 30 seconds to 2 minutes. Unlike generalized seizures, FBTCS may end with asymmetrical jerking movements.
After the jerking subsides, involuntary urination or defecation may occur. The seizure is often accompanied by groaning sounds and excessive salivation.
Once the seizure ends and consciousness returns, the patient is typically drowsy, disoriented, and has complete amnesia regarding the seizure for several minutes.