Transient epileptic amnesia: the contribution of the british neurological surveillance unit.
Zeman A., Dewar B., Butler C.
Transient Epileptic Amnesia (TEA) is a subtype of temporal lobe epilepsy characterised by recurrent episodes of transient amnesia, usually in middle aged people, often occurring on waking, which prove to be due to epilepsy. Attacks are sometimes accompanied by other more familiar manifestations of epilepsy, especially olfactory hallucinations. The epilepsy typically responds very well to anticonvulsant treatment but interictal memory disturbance often persists despite abolition of the seizures, in particular an extensive autobiographical amnesia (AA), and a tendency for memories to fade more rapidly than usual over days to weeks (accelerated long-term forgetting, ALF). The TIME project (The Impairment of Memory in Epilepsy: see http://www.exeter.ac.uk/time/) was established in 2003 to study TEA and its associated interictal memory disturbance. It has since generated around 20 publications describing the clinical, neuropsychological and radiological features of TEA, AA and ALF.(1-4) The British Neurological Surveillance Unit (BNSU) contributed to patient recruitment in 2003-2005 and again recently (2011-present). In 2003-5, 32 patients were referred via the BNSU. 16 were included in the patient cohort described in our 2007 report,(1) nine were excluded as they did not satisfy our diagnostic criteria, seven were potentially suitable but study resources did not allow us to assess them fully. 22 cases have been referred recently. Details are awaited for 13, one refused consent, four have been assessed, three await assessment, one was excluded after assessment. The BNSU has made a major contribution to the success of the TIME project. The recruitment process would work more smoothly if participating neurologists i) asked patients for consent to pass on demographical and clinical details at the time of the clinic visit on which they are identified, ii) communicated these immediately to the researcher or iii) kept a note of patient details if i) and ii) are not feasible. The current system works well, and helps greatly in the recruitment of series of cases of moderately rare disorders, but its efficiency could be improved.