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The evaluation of progressive neurological and/or cognitive decline poses one of the greatest challenges to the paediatric neurologist. While the potential causes are individually quite rare, collectively neurodegenerative disorders are quite common with an incidence of approximately 0.5/1000 live births.1 Faced with an individual child, it is easy to feel daunted by textbooks2,3 that tend to be organised according to pathology, rather than presentation, and which emphasise that many of these conditions have “variants” that can present at widely differing ages. Confusing terminologies, and non-specific presentations, tend to add to a sense of despair at ever getting to grips with the field.
Confining the scope of this paper to conditions presenting in adolescence limits the number of conditions under discussion, simplifying matters considerably. However, considerations pertinent to the evaluation of progressive disease across the paediatric age range still arise.
PROGRESSION OR EVOLUTION?
In young children, the interplay of physiological developmental progress (even at a reduced rate) and a neurodegenerative condition can result in surprising difficulty in establishing whether signs and symptoms are truly progressive. The progressive nature of a new onset disease in a previously healthy adolescent will clearly be much more obvious, but such clear cut situations are quite rare. Quite frequently, new concerns are raised about an adolescent child with pre-existing neurological signs and symptoms, especially the child with longstanding “learning difficulties” or “cerebral palsy” (CP). Jean-Pierre Lin and Chris Rittey discuss the differential diagnoses of these entities elsewhere (see pages i23 and i30). Such labels may have been assigned after only a limited aetiological work up and mask a slowly progressive primary diagnosis. A diagnosis of severe quadriplegic or dyskinetic CP ideally requires an unambiguous history of severe hypoxic ischaemic encephalopathy (HIE) in a term infant. A diagnosis of diplegic CP is most secure in a child …