Sleep and Awake EEG

[Andrew Lee]

Early research on sleep and epilepsy were focused on the relationship
between seizures during waking and sleeping. The earliest findings
showed that almost two thirds of seizures occurred between 8 PM and 8
AM with insufficient sleep activating seizures. It was noted that 21%
of seizures happened only at night, 42% during the day, and 37% during
the night or day (out of 850 patients). Nocturnal seizures happened
most often during the near end of sleep period (5 – 6 AM) and less
often 1-2 hours after sleep onset whereas daytime seizures were
clustered in the early morning and late afternoon which lead the
conclusion that peaks in seizures occurred in reponse to falling
asleep and awakening. Another study found that generalized tonic-
clonic seizures occurred 44% in sleep, 33% at awakening, and randomly
in 23% of cases. It was also found that awakening epilepsies were
unlikely to have a known cause whereas sleep and random epilepsies
more did have a known cause. Several epilepsy syndromes are
characterized by seizures happening mostly or exclusively from sleep
or upon awakening. More recently, it was found that seizures in
patients with frontal lobe epilepsies typically arise from sleep,
almost exclusively during non REM sleep. Sleep tends to activate
frontal rather than temporal seizures. Also secondary generalized
seizures of partial seizures tend to occur more than wakefulness.