Page 340 - ILAE_Lectures_2015

Chapter 34

Treatment of non-convulsive status epilepticus

MATTHEW C. WALKER

Institute of Neurology, University College London, National Hospital for Neurology and
Neurosurgery, Queen Square, London
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Introduction

Seizures of any type can continue unabated and they are then considered as a separate entity,
status epilepticus. This is of great importance, as in certain circumstances a persistent seizure
can result in neuronal damage irrespective of any physiological compromise.

Among the diagnoses of status epilepticus are a number that can are considered as non-
convulsive status epilepticus including absence status epilepticus, atypical absence status
epilepticus, electrical status epilepticus during slow-wave sleep (including Landau-Kleffner
syndrome), complex partial status epilepticus and status epilepticus in coma. Indirect
estimates for the incidence of non-convulsive status epilepticus have been as high as 1424
per 100,000 population per year (the majority of these are non-convulsive status epilepticus
in the setting of learning difficulties). Although non-convulsive status epilepticus includes a
number of very different conditions, these forms of status epilepticus share two important
qualities: difficulty in making the diagnosis, and uncertainty about the best mode of
treatment.

Diagnosis

The diagnosis of non-convulsive status epilepticus can be difficult, and is dependent on EEG.
In patients with a previous diagnosis of epilepsy, any prolonged change in personality,
prolonged post-ictal confusion (greater than 20 minutes) or recent onset psychosis should be
investigated with EEG as these can all be presentations of non-convulsive status epilepticus.
If new onset developmental delay occurs in the setting of epilepsy then a sleep EEG should
be considered to look for status epilepticus during slow-wave sleep (see below). In non-
comatose patients with no history of epilepsy, non-convulsive status epilepticus can present
as confusion or personality change (almost invariably in the setting of a metabolic
derangement, encephalitis or other acute precipitant). Rarely, non-convulsive status
epilepticus can present as autism and if suspicions are raised (usually a fluctuating course)
then EEG is indicated.

Non-convulsive status epilepticus can follow convulsive status epilepticus, and is an
important treatable cause of persistent coma following convulsive status epilepticus. This and
status epilepticus with subtle manifestations such as twitching of the limbs, or facial muscles
or nystagmoid eye jerking, which can result from hypoxic brain damage, are often
collectively referred to as subtle motor status epilepticus. Up to 8% of patients in coma who
have no outward signs of seizure activity are in non-convulsive status epilepticus, thus
emphasising the importance of EEG in the investigation of comatose patients. Similarly, non-
convulsive status epilepticus is underdiagnosed in the confused elderly in whom the
confusion is frequently blamed on other causes.
Although EEG interpretation is usually straightforward, with regular repetitive discharges
occurring in some patients in a cyclical fashion, difficulties can occur in differentiating non-
convulsive status epilepticus from an encephalopathy of other cause. Thus electrographic