Get Adobe Acrobat ReaderResearch Areas - Transient Epileptic Amnesia (TEA)
Amnesia is the key presenting feature of one subtype of TLE. This presentation of TLE was originally described in case reports and small case series, and identified as an important differential diagnosis of Transient Global Amnesia (TGA). Zeman et al described the clinical and neuropsychological features of 10 personally studied cases, reviewing a further 21 previously published cases. Zeman et al adopted the term originally coined by Kapur for this disorder, Transient Epileptic Amnesia, to emphasise the similarities and differences between this condition and Transient Global Amnesia. We more recently described the clinical features of 50 TEA cases using the following diagnostic criteria:
A diagnosis of TEA requires the following:
- A history of recurrent witnessed episodes of transient amnesia
- Cognitive functions other than memory judged to be intact during typical episodes by a reliable witness
- Evidence for a diagnosis of epilepsy based on one or more of the following:
- Epileptiform abnormalities on electroencephalography (EEG)
- The concurrent onset of other clinical features of epilepsy (e.g. lip-smacking, olfactory hallucinations)
- A clear-cut response to anticonvulsant therapy.
Read a description of a transient epileptic attack
Read patient case studies which help describe the disorder of TEA
Clinical Features of TEA
We found the following features in 50 TEA patients referred nationwide via the British Neurological Surveillance Unit to the TIME project.
| Mean age at onset (yr) | 62.1 (range 44-77) |
|---|---|
| Sex distribution (M/F) | 34/16 |
| Median number of attacks | 10 (IQR, 6-30) |
| Median frequency (attacks per year) | 12 (IQR, 5-20) |
| Median attack duration | 30-60 minutes (range, <1 minute to days) |
| Attacks on waking | 74% |
| Repetitive questioning | 50% |
| Partial anterograde amnesia | 66% |
| Olfactory hallucinations | 42% |
| Motor automatisms | 36% |
| Good response to AED | 94% |
| Interictal EEG positive | 37% |
| Incorrect initial diagnosis | 76% |
The amnesia occurring in attacks of TEA involves a variable mixture of anterograde amnesia (inability to form new memories) and retrograde amnesia (inability to retrieve old memories) but the former is often partial so that subjects 'remember not being able to remember'. The frequency and brevity of attacks of TEA distinguish this condition from TGA. The diagnosis is often delayed, but the attacks respond promptly to modest doses of anticonvulsant. Some patients' attacks are exclusively amnesic whilst others display more familiar features of epilepsy in some or all attacks.
Two additional, persistent, interictal memory complaints are common among patients with TEA:
- Accelerated Long-term Forgetting is the excessively rapid decay of memories that appear to have been acquired successfully, noted by the patient days to weeks after initial encoding
- Autobiographical Amnesia is a patchy, but dense, loss of the ability to evoke memories for salient life events, often extending back over several decades, well before the onset of symptoms of epilepsy