Transient Epileptic Amnesia (TEA)
"Transient amnesia" refers to repeated attacks of memory loss.
There are a number of well recognised causes of transient amnesia, the most common probably being head injury, followed by transient global amnesia, migraine, drugs and rarely, transient ischemic attacks ("mini strokes"). It has recently been recognised that transient amnesia can also be caused by epilepsy.
TEA is often misdiagnosed as either transient global amnesia (TGA) or psychogenic amnesia. Distinguishing TEA from other causes of amnesic attacks is an important step in developing successful treatment programmes for this form of amnesia and its associated memory deficits.
A diagnosis of TEA requires the following:
- Recurrent witnessed episodes of amnesia
- Cognitive functions besides memory remain intact (e.g. language, attention and decision-making)
- Evidence for the diagnosis of epilepsy
- EEG abnormalities
- The experience of other common epileptic symptoms, such as, involuntary movements, hallucinations of smell or feeling a swirling sensation in your tummy
- A clear response to anti-epileptic drugs
Butler and colleagues recruited 50 patients with TEA using these diagnostic criteria in order to assess the clinical features of the syndrome. They found the following:
- Onset typically occurs in late-middle to old age (median 62 years)
- The syndrome predominantly occurs in men (male to female ratio 2:1)
- The amnesic attack is brief (typically 30-60 minutes duration)
- The amnesic attacks are recurrent (average 12 per year)
- Attacks often occur on waking
- Often associated with hallucinations of smell & involuntary movements (automatisms)
- Clinicians often make an incorrect initial diagnosis of the condition
- Memory difficulties involve a mixture of anterograde and retrograde amnesia
Results from our studies have also shown that TEA is associated with two particular types of memory difficulty between attacks:
In addition, some patients with TEA also notice an impaired ability to navigate around new and familiar routes; called topographical amnesia.