Transient Global Amnesia - Causes - Epilepsy

Epilepsy

Amnesia is often a symptom in epilepsy, and for that reason people with known epilepsy are disqualified from most studies of TGA. In a study where strict criteria were applied to TGA diagnosis, no epileptic features were seen in EEGs of over 100 patients with TGA. However, despite the fact that EEG readings are usually normal during a TGA attack, and other usual symptoms of epilepsy are not observed with TGA it has been speculated that some initial epileptic attacks present as TGA. The observation that 7% of people who experience TGA will develop epilepsy calls into question whether those case are, in fact, TGA or transient epileptic amnesia (TEA). TEA attacks tend to be short (under one hour) and tend to recur, so that a person who has experienced both repeated attacks of temporary amnesia resembling TGA and if those events lasted less than one hour is very likely to develop epilepsy.

There is additional speculation that atypical cases of TEA in the form of nonconvulsive status epilepticus may present with duration similar to TGA. This may constitute a distinct subgroup of TGA. TEA, as opposed to "pure" TGA, is also characterized by "two unusual forms of memory deficit …: (i) accelerated long-term forgetting (ALF): the excessively rapid loss of newly acquired memories over a period of days or weeks and (ii) remote autobiographical memory loss: a loss of memories for salient, personally experienced events of the past few decades."

Whether an amnestic event is TGA or TEA thus presents a diagnostic challenge, especially in light of the recently published descriptions of possible long-term cognitive deficits with (presumably correctly diagnosed) TGA.