Savage SA, Butler CR, Hodges JR and Zeman AZ have published a paper ‘Transient Epileptic Amnesia over twenty years: Long-term follow-up of a case series with three detailed reports‘ in the journal Seizure (subscription needed).
Transient Epileptic Amnesia refers to a condition in which seizures are associated with a transient loss of memory. An intuitive question to ask here is whether the memory loss is progressive.
The authors here have published a case series of 10. This isn’t a big number but even so I find the conclusions convincing. 9 of the people were included in the follow-up and only one had received a diagnosis of Dementia – Vascular Dementia after 20 years.
At 10 years there was stability in the neuropsychology performance. At 20 years there was some general cognitive decline but this wasn’t consistent with the pattern seen in Alzheimer’s Type Dementia.
A 20 year follow-up is convincing. The numbers aren’t big and in the Cochrane hierarchy of evidence case series are pretty low on the hierarchy of evidence. For me this should call us to reconsider whether evidence should be weighted so mechanically.
Case studies and case series have been an integral part of medicine for a very long time and allow the clinician to communicate their clinical insight or intuition. This can then be confirmed or refuted by other clinicians in the course of clinical praxis.
The case series offers an answer to a clinical question. In the absence of other evidence, it is an answer. In the presence of other evidence there is an opportunity for confirmation or debate.
There are many rare conditions or unique circumstances where larger trials are not available. Perhaps a renaissance in the case study and case series would stimulate an academic conversation about under-represented conditions.
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