For a few hours after Jan Quinlan's first epileptic seizure, doctors thought her condition was due to misuse of drink or drugs. She remembers that clearly because she knew they were mistaken. Several days later she had surgery to remove a benign brain tumour. She remembers that time too, even though it was 14 years ago. What she doesn't remember is her sister's wedding in 2006 or 2007. She knows that she was there, because photographs prove it, but her only recollection of the day is that it was sunny.

“My memory is like pictures, but now some parts are blank,” she says. “It's like someone's turned off the TV. Nothing is left and nothing anyone says makes them come back. Random parts of my past have gone. There was no gradual deterioration; they just went after I had fits. I love my sister and it makes me feel emotional that I can't remember her wedding.”

Four years ago the first doctor to whom Quinlan reported that she had permanently lost chunks of her long-term memory told her that this was because of her age. Quinlan, now 55, was certain that her inability to remember some significant events from her past was connected to her epilepsy and sought a second opinion. This time the doctor supported her.

It is well-known that people with epilepsy commonly report difficulties with memory. What is not always accepted by doctors is that epilepsy could be the cause of the memory problems. “The prevalence of the memory impairment that goes along with epilepsy is under-recognised and under-appreciated,” says John Duncan, professor of neurology at University College, London, and medical director of the National Society for Epilepsy. “People often make light of it. I don't think there's any conspiracy; it's just what people have been taught. There can be many factors and it can be difficult to tease out the contribution of the different parts.”

Duncan believes that long-term memory loss can be caused by epilepsy, particularly if the seizures involve the temporal lobe (the part of the brain where memories are laid down). He describes a seizure as an abnormal firing of nerve cells. “It's like an excessive electrical discharge that burns out some of the wiring. Each seizure may knock out one nerve cell in 1,000, which wouldn't be obvious, but if someone over the course of years has hundreds of seizures, there would be a cumulative effect.”

Gus Baker, professor of clinical neuropsychology at the University of Liverpool, works exclusively in the field of epilepsy. “In the 20 years I've been in clinical practice, I've yet to come across a patient who hasn't experienced memory difficulties,” he says. “There are a number of studies that show that epilepsy and epileptic foci, the part of the brain that causes people to have seizures, disrupts the long-term consolidation of memory.” Baker says memory is important because it is one of the foundation blocks of our relationships. “Some patients avoid contact with other people because they're embarrassed about memory loss. Having a good memory is important for social skills - and also for learning. It's frustrating to see adolescents with epilepsy, where there is little recognition that they are likely to have memory problems and need extra support in the acquisition of knowledge, particularly when they come to GSCEs.”

Another reason for the underrecognition of the link between epilepsy and memory is that conventional memory tests don't pick up autobiographical memory problems, says Adam Zeman, Professor of Cognitive and Behavioural Neurology at the Penisula Medical School in Exeter. “Often when one sends people with epilepsy to have standard psychological tests, the report comes back normal. That's because typically the tests ask you to learn a list of words and remember them half an hour later; they don't tap your autobiographical memory.”

Zeman, like Duncan and Baker, does not attribute long-term memory problems to the drugs used to treat epilepsy - modern drugs are less toxic in this respect than the sedating barbiturates used in the past - although large combinations of combined drugs can impair a person's concentration and speed of thought. In Zeman's study of 50 people with adult-onset epilepsy, all suffered from transient epileptic amnesia, a short period of amnesia when they had seizures, and about three quarters had patchy but permanent long-term memory loss for past events that they often knew they could remember previously. “One reason for wondering whether the seizures are the cause is that with this condition you can make the seizures go away, but people are still left with the memory loss of their personal past.”

Treatment for memory loss is a difficult area. It is clearly helpful to use drugs to try to reduce seizures and, if a regime slows down a patient, it can be changed. Depression and anxiety can also be treated, and increasingly doctors recommend that patients with memory problems develop strategies to help them: Baker's team at the Walton Centre for Neurology and Neurosurgery in Liverpool has developed a memory programme that advises on techniques for remembering.

Even though epilepsy affects one British person in 131, its treatment has always been underfunded. Doctors and patients recognise that the condition carries a stigma, largely because seizures are frightening. This is why Quinlan is speaking out. A tall, elegant woman who was a career counsellor and “didn't do ill” until she had her first seizure, she is now unable to work but lives independently in Middlesex. She says her current doctor has given her psychological succour by believing in her memory loss, though it has damaged some of her friendships. When I ask how she fills her time she mentions some weekends away but can't provide many details, which she says illustrates her point. “I spend a lot of time alone. I don't know whether it's choice or circumstance. I'm resourceful and I've got used to it.”

National Society for Epilepsy: www.epilepsynse.org.uk; helpline 01494 601400.

Epilepsy Action produces a free booklet on memory: www.epilepsy.org.uk; helpline 0808 8005050.

Epilepsy Research UK: www.epilepsyresearch.org.uk

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