Page 343 - ILAE_Lectures

Page 343 - ILAE_Lectures_2015

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Atypical absence status epilepticus
Atypical absence status epilepticus is associated with the epileptic encephalopathies such as
Lennox-Gastaut syndrome. This entity can be difficult to diagnose, but should be considered
if there is change in personality, decrease in cognition or increased confusion in a patient with
one of these epilepsies. The EEG characteristics are usually that of continuous or frequent
slow (< 2.5 Hz) spike and wave. This condition is usually poorly responsive to intravenous
benzodiazepines, which should, in any case, be given cautiously, as they can induce tonic
status epilepticus in these patients. Oral rather than intravenous treatment is usually more
appropriate, and the drugs of choice are valproate, lamotrigine, topiramate, clonazepam and
clobazam. Sedating medication, carbamazepine and vigabatrin have been reported to worsen
atypical absences.

Non-convulsive status epilepticus in coma

Electrographic status epilepticus in coma is not uncommon and is seen in up to 8% of patients
in coma with no clinical evidence of seizure activity. The diagnosis is often debatable as in
many instances burst-suppression patterns, periodic discharges and encephalopathic triphasic
patterns have been proposed to represent electrographic status epilepticus, while these mostly
indicate underlying widespread cortical damage or dysfunction. Non-convulsive status
epilepticus in coma consists of three groups: those who had convulsive status epilepticus,
those who have subtle clinical signs of seizure activity and those with no clinical signs.
Convulsive status epilepticus has, as part of its evolution, subtle status epilepticus in which
there is minimal or no motor activity but ongoing electrical activity. This condition should
be treated aggressively with deep anaesthesia and concomitant AEDs. The association of
electrographic status epilepticus with subtle motor activity often follows hypoxic brain
activity and has a poor prognosis, but aggressive therapy with benzodiazepines, phenytoin
and increased anaesthesia is perhaps justified, since the little evidence available indicates that
such treatment improves prognosis.

Lastly electrographic status epilepticus with no overt clinical signs is difficult to interpret –
does it represent status epilepticus or widespread cortical damage? Since these patients have
a poor prognosis, aggressive treatment is recommended in the hope that it may improve
outcome. Lastly there is a group of patients in whom there are clinical signs of repetitive
movements, but no electrographic seizure activity, and in these patients antiepileptic
treatment and aggressive sedation is not recommended.

Conclusion

Non-convulsive status epilepticus is an all-encompassing term that covers a variety of
conditions with very different prognoses from the entirely benign to the fatal (although this
is mainly due to the underlying aetiology). These conditions are poorly replicated by available
animal models, and this together with the lack of randomised treatment trials has meant that
the best treatment options are unknown. It is important to remember that aggressive AED
treatment is not benign especially when deep anaesthesia is proposed.