Epileptic seizures are often un-witnessed and can result in hypoxic brain
damage or can be fatal due to injuries, status epilepticus or sudden
unexpected death in epilepsy (SUDEP). The first aim of this thesis was to
investigate some of the physiological parameters that accompany an epileptic
seizure and may be useful in a seizure alarm system. The second aim was to
investigate aspects of cardiac dysfunction during clinical and sub-clinical
seizures that may be potential contributing factors in SUDEP. Percentage
heart rate change and oxygen saturation were studied prospectively during
527 epileptic seizures in 50 patients aged from one-day full term neonate to
60 years with a variety of seizure types (absences, generalised tonic clonic
seizures, myoclonic seizures, tonic seizures and focal seizures) and in normal
physiological events (e.g. coughing, turning in bed). Higher percentage heart
rate change occurred during epileptic seizures (21.8%) than during normal
physiological events (16.4%) p<0.001. Diagnostic testing of clinically
significant seizures i.e seizures that could potentially lead to serious
consequences if left undetected (n=61) had a sensitivity of 91% and specificity
of 75% when percentage heart rate change and hypoxaemia parameters were
combined. Percentage heart rate change and oxygen saturation could be used
as reliable indicators of a seizure when set at specific levels and distinguish
clinically significant seizures from normal physiological events. These
parameters can now be used to develop a reliable alarm system to detect
epileptic seizures at night. Prolongation of QTc and increased vagal tone may
be possible mechanisms underlying SUDEP. Corrected Q-T cardiac repolarisation
time 5 minutes before and throughout 156 epileptic seizures
were analysed using four corrective formulae (Bazett, Hodge, Fridericia and
Framingham). All formulae indicated statistically significant lengthening of
the corrected Q-T during epileptic seizures (p<0.001) compared to pre-seizure
values. All formulae agreed that the greatest lengthening of the corrected QT
beyond normal limits occurred during right temporal lobe seizures in two
patients. Reflex and tonic vagal activity utilising R-R intervals was assessed
in 33 sub-clinical seizures occurring during stages 3 or 4 sleep and was
compared to matched counts of R-R interval non-ictal baseline studies from
the same stage of sleep in each patient. Altered vagal activity occurred
during total sub-clinical seizures compared to baseline studies (p<0.001).
Lengthening of the corrected Q-T and changes in cardiac vagal tone during
epileptic seizures may have a role in the patho-physiology of SUDEP