Epilepsy

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EPILEPSY

Contrary to what has been asserted in the past, recent literature has demonstrated that the incidence of provoked and unprovoked seizures and of epilepsy and the prevalence of epilepsy in older people is high. It is therefore regrettable that seizures in old age are still relatively under-researched. There are reasons for not relying on data obtained from the general adult population when deriving a picture of epilepsy in old age. The presentation, the etiology, the clinical pharmacology, the functional consequences, and the associated core morbidity are all different in old age.

Presentation and diagnosis

Since many older people live alone, there may be an inadequate history and older people may present with a history of recurrent unexplained falls or of being found on the floor. The vast majority of seizures in old age are either partial seizures with, for example, focal motor events such as recurrent jerking of an arm or leg, or secondary generalized seizure that may present either with disturbances of higher level function as in complex partial seizures or with convulsive movements. The list of conditions that may be confused with epilepsy is very long and includes: fainting; low blood sugar; transient ischaemic attacks; recurrent paroxysmal behavioral disturbances, such as clapping or calling out, secondary to dementia; drop attacks and other nonepileptic causes of falls; transient global amnesia; and nonepileptic attack disorder or psychogenic attacks. Conversely, there is an equally long list of conditions that are genuinely epileptic but may be thought to be nonepileptic; partial motor status epilepticus (e.g., persistent involuntary movement of an arm or leg) may be thought to be an extrapyramidal movement disorder such as Parkinson's disease; sensory epilepsy may be thought to be a transient ischaemic attack; complex partial seizures in which a patient may stare or call out can be confused with psychoses; atonic seizures can be confused with drop attacks or hysteria; and Todd's palsy (transient weakness) following a generalized seizure can be confused with a new stroke or a transient ischaemic attack.

The biggest challenge in elderly epileptology is determining whether or not the patient's events are seizures or fainting (syncope). Differentiating the two conditions may be extremely difficult in the absence of an eyewitness report. Moreover, the usual features that differentiate the two conditions may not apply to older people. For example, whereas syncope is not usually associated with either incontinence (loss of bladder and/or bowel control) or post-event confusion, an elderly person who is already incontinent or has background confusion may be incontinent or confused in association with a syncope attack. Even so, the history remains the most powerful diagnostic tool. Investigations will be guided by the history and the findings on examination. The EEG will rarely be useful in making a diagnosis of epilepsy and certainly should not be used to make up for the shortfalls in history taking. The indications for neuroimaging are not well defined and depend at least in part on the availability of radiological services. Strong indications for neuroimaging include unexplained focal neurological signs, progressive or new neurological symptoms, especially those of raised intracranial pressure, progressive or new neurological signs or poor control of fits not attributable to poor compliance, or continued exposure to precipitants such as alcohol.

The most common cause of seizures in old age is cerebrovascular disease: seizures may be a harbinger of future manifestations of cerebrovascular disease; late onset seizures are associated with a higher level of occult cerebral ischaemia; and overt strokes may trigger seizures either acutely or subsequently. Any patient who develops a seizure for the first time in old age when there was no obvious cause should be thoroughly investigated for cardiovascular risk factors and possibly placed on low dose aspirin, so long as there is no contraindication. Other cerebral causes of seizures include tumor, which may account for 10 to 15 percent of elderly onset cases. However, the proportion of these cases in which seizure is the only manifestation and the proportion in which any underlying tumor found is benign and/or resectable is not known. Seizures may occur in nonvascular cerebral degenerative disease, such as Alzheimer's disease. Non-cerebral causes of seizures include those which are secondary to cerebral anoxia as in prolonged syncopal attacks due, for example, to cardiac arythymias. Seizures may also be triggered by a wide variety of drugs that have proconvulsant side effects, notably tricyclic antidepressants, phenothiazines, and aminophylline. The role of alcohol in triggering seizures in older people or in interfering with control must not be forgotten.

Management

Reassurance, education, and information are of paramount importance in the management of elderly patients with seizures as in any other age group. Guidance on driving regulations, reasonable risk-taking, and the avoidance of precipitants of seizures should be covered. The mainstay of treatment is drug therapy. This should not be undertaken lightly and a so-called therapeutic trial of antiepileptic drugs in patients whose episodes are of uncertain nature is usually undesirable, unless the events are occurring with such frequency that the response to drugs can be assessed very quickly. It must be remembered that the adverse impact of drugs may outweigh the episodic discomfort of an occasional seizure. Drug treatment is usually started in patients who have more than one unprovoked generalized seizure or a single major seizure where there is a continuing underlying cause as in the case of a patient who has had a cerebral infarct in the past. The evidence that early treatment prevents recurrent epilepsy from becoming chronic (the notion that "fits breed fits") is poor. Patients with minor seizures that are not in any way interfering with their life may, if the episodes are infrequent, reasonably elect not to have drug treatment.

Recent meta-analyses have made the choice of anticonvulsant a little easier. There is evidence that carbamazepine has some advantages over the other first-line drugs (phenytoin or sodium valproate) for the generality of elderly people who have partial or secondary generalized seizures. However, there may be a case for using other drugs for first-line treatment in patients with specific problems. Where compliance demands that patients receive medication once daily, there may be a case for phenytoin, although this may predispose to bone demineralization as well as having the neuropsychiatric effects shared with other anticonvulsants. Carbamazepine may predispose to hyponatraemia (low sodium in the blood or less than 130 mmol/l), particularly in patients on diuretics or who have recurrent chest infections. Sodium valproate may be the drug of choice for patients who cannot tolerate either phenytoin or carbamazepine or in the small number of patients who have primary generalized seizures. There is relatively little evidence about the newer generation of anticonvulsants but lamotragine appears to be at least as effective as carbamazepine and may have fewer side effects, although it is expensive; and gabapentin has the advantage of not interacting with other drugs as well as being relatively non-toxic, although it may also be relatively less effect in controlling seizures. There are no recommended doses of anticonvulsants for older people. Overall, the retrospective analysis of a Veterans Administration's study of the effect of age on epilepsy and its treatment showed that older patients' seizures were better controlled and they were on lower doses of anticonvulsants than were younger patients. However, there is enormous variation between older people. Anti-epileptic drug monitoring may be particularly useful in the case of phenytoin and carbamazepine. The prognosis for control is at least as good as, or possibly better than, in the general adult population. There is little evidence about the appropriateness of withdrawal of anticonvulsants as studies have not been done in older people. Presently, an elderly person who has been started appropriately on an anticonvulsant may have to remain on it for the rest of his or her life.

Services for elderly people with epilepsy are often poorly developed: such patients fall between geriatrics and neurology services. There is a case for developing specialized epilepsy services for older people that can address both management of seizures and other concurrent problems and associated disabilities. A key element of that service would be a specialist epilepsy nurse.

Raymond C. Tallis

See also Balance and Mobility; Dementia; Disease Presentation; Drugs and Aging; Fainting; Stroke.