Page 250 - ILAE_Lectures_2015

Chapter 24

Investigation of progressive neurological impairment in children
with epilepsy

J. HELEN CROSS1 and AILSA McLELLAN2

1UCL Institute of Child Health, Great Ormond Street Hospital for Children NHS Trust,
London, and the National Centre for Young People with Epilepsy, Lingfield, and
2Department of Paediatric Neurosciences, Royal Hospital for Sick Children, Edinburgh

Whether epilepsy has presented as the initial feature of a progressive neurodegenerative
disease in a child is often a diagnostic dilemma in those with more challenging cryptogenic
epilepsy. Epilepsy as a sole presenting feature is rare, but recognised in a certain number of
disorders (see below). More specifically, in a child presenting with cognitive decline, the
question may remain as to whether this is secondary/related to the epilepsy or whether there
is associated intrinsic pathology.

Cognitive or developmental plateau or regression is well recognised at the onset of certain of
the more severe early epilepsy syndromes. The underlying pathophysiology to this remains
uncertain, however, and appears to be related in part to the early onset of frequent seizures.
The term ‘epileptic encephalopathy’ is now recognised as part of the ILAE classification of
the epilepsies1, described as disturbances of cognition, behaviour, and motor control that
occur with epileptic seizures and are attributed to epileptiform activity, which may be
subclinical. Many individuals show periods of apparent improved developmental progress in
association with improved seizure control. In some children it is relatively easy to determine
the relationship of epilepsy to the cognitive problems and the need to investigate such.
Although aggressive treatment of overt seizures is appropriate, it is more difficult to define
the criteria to treat subclinical discharges, in the absence of overt non-convulsive status
epilepticus.

Is it real?

The initial phase of the evaluation is to determine whether the cognitive decline is ‘real’ as
opposed to ‘apparent’. Children may experience developmental plateau in association with
the presentation of severe epilepsy. There is usually an accurate documentation by the parents
of previous developmental milestones, and the history may give detail of lack of progress
with, rather than loss of, milestones. It is more difficult to determine the answer to the
question ‘Why is he going backwards?’ In children with long-standing symptomatic epilepsy
lack of progress becomes evident. In these children, learning does not progress with age,
which means the gap between the child and their peers widens – with a consequent drop in
IQ. This is not a loss of skills but rather a failure to progress, and becomes particularly
apparent around the age of seven years when abilities such as practical reasoning and abstract
thought start to develop in normal children.

Key points in the history are age at onset, the relationship or not to frequency of seizures, and
the pattern of regression. A pattern of fluctuating abilities as opposed to steady decline is
likely to suggest an epileptiform basis, although some neurodegenerative conditions may
show a stepwise progression. Periods of apparent encephalopathy should also alert the doctor
to the need for investigation. The history may distinguish whether this is likely to be part of