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SURGICAL APPROACHES TO EPILEPSY: SURGERY FOR PARTIAL (FOCAL) SEIZURES – EVALUATION OF LANGUAGE

Posted on June 19, 2011, under Epilepsy.

Speech is usually located on the left side of the brain, in the posterior temporal lobe (see Chapter 6). However, in 10 to 15 percent of left-handed people speech is on the right side. It is vital to know where it is before proceeding with surgery.
The Wada test, named after the neurosurgeon Dr. Juhn Wada, is designed to localize speech and memory. A catheter is threaded from the groin of the awake patient up to the internal carotid artery, the main artery supplying one side of the brain. After a small injection of a dye, which can be seen on x-ray, a small amount of barbiturate is injected and that side of the brain is briefly “put to sleep.”
As the test begins, the patient is asked to hold his arms up in the air and to count. If the injection is done on the left side of the brain, the right arm becomes weak as the left side of the brain goes “to sleep.” If speech is on that same side, the child will simultaneously, but briefly, lose the ability to speak or count. Memory is also tested by showing objects and pictures. When the medication wears off, the patient will be asked to recall the objects he has seen. If lost, speech and memory quickly return when the drug wears off. In this crude fashion the laterality (side) of speech is determined. The same procedure may also be carried out on the other side of the brain, because occasionally speech is located on both sides.
If injecting the right side produces no alteration in speech or memory, then it can be assumed that it is safe to operate on that side. If speech is on the left and the surgery is to be done near that area, then far more careful evaluation of speech, language, and the epileptic focus must precede a decision about surgery.
Detailed neuropsychological testing may be performed prior to surgery to assess the person’s intellectual function and personality. This may help in understanding if certain parts of the brain previously have been damaged.
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DRUGS FOR ABSENCE AND OTHER GENERALIZED SEIZURES: WHAT MAY VALPROIC ACID CAUSE?

Posted on February 25, 2011, under Epilepsy.

In some children, valproic acid may cause an increase in the blood level of ammonia, leading to sleepiness, headache, nausea, or vomiting. Children with these symptoms should have a blood ammonia level test, and if the ammonia level is found to be elevated, the valproic acid dose should be decreased or the medication stopped.
Valproic acid itself rarely affects learning or behavior negatively. It seldom causes sleepiness. If these symptoms occur when the drug is started, they usually are a consequence of an increase in the level of some other drug the child is taking, particularly phenobarbital. Valproic acid increases the blood level of phenobarbital by 30 percent; thus, the dose of phenobarbital must be decreased by one-third when valproate is begun.
Valproic acid (Depakene) may be irritating to the stomach and cause nausea, vomiting, and a decrease in appetite. These symptoms decrease if the drug is taken along with meals. Depakote, a slightly different form of the drug, is said to have fewer effects on the stomach.
Weight gain, loss of appetite, and temporary loss of hair also occur in some individuals who are taking valproic acid.
Although the list of side effects of valproate seems long, we repeat that it is an excellent anticonvulsant drug, and, if used properly, it is also very safe.
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DRUGS FOR ABSENCE AND OTHER GENERALIZED SEIZURES: WHAT MAY VALPROIC ACID CAUSE?In some children, valproic acid may cause an increase in the blood level of ammonia, leading to sleepiness, headache, nausea, or vomiting. Children with these symptoms should have a blood ammonia level test, and if the ammonia level is found to be elevated, the valproic acid dose should be decreased or the medication stopped.Valproic acid itself rarely affects learning or behavior negatively. It seldom causes sleepiness. If these symptoms occur when the drug is started, they usually are a consequence of an increase in the level of some other drug the child is taking, particularly phenobarbital. Valproic acid increases the blood level of phenobarbital by 30 percent; thus, the dose of phenobarbital must be decreased by one-third when valproate is begun.Valproic acid (Depakene) may be irritating to the stomach and cause nausea, vomiting, and a decrease in appetite. These symptoms decrease if the drug is taken along with meals. Depakote, a slightly different form of the drug, is said to have fewer effects on the stomach.Weight gain, loss of appetite, and temporary loss of hair also occur in some individuals who are taking valproic acid.Although the list of side effects of valproate seems long, we repeat that it is an excellent anticonvulsant drug, and, if used properly, it is also very safe.*126\208\8*

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LIVING WITH EPILEPSY: WHAT TO DO DURING A SEIZURE

Posted on December 9, 2009, under Epilepsy.

What should a bystander do during a grand mal attack? The onset is often so sudden that it is difficult to do much at all in the early stage, though it may be possible to break the person’s fall. Parents or other relatives may recognize the warning signs that may occur if the generalized seizure follows a focal discharge, and so may have time to help the person to a chair or to a bed before the grand mal begins.

Don’t try to open the person’s clenched mouth. The tongue, if bitten, is bitten at the onset of the attack, so there is no point in trying to save it. If the bystander uses his own fingers to try to force the mouth open, they may well be bitten in the clonic phase. If he tries to force a spoon or pencil between the teeth, the person’s teeth may be damaged. These manoeuvres are still sometimes attempted by tradition, and sometimes, presumably, because it is assumed that the person’s blue colour and arrest of breathing are due to obstruction to the passage of air into the lungs. Attempts to ‘loosen the collar’ presumably result from the same thoughts. However, all of us have enough gaps between our teeth to allow passage of air around them as readers can readily show for themselves by clenching their teeth, pinching the nose, and breathing in. Obstruction to the airway may occur during a seizure, if the person is lying on his back. The tongue may then fall backwards into the pharynx, and, for this reason, it is worth turning someone suffering a grand mal seizure into a position halfway between lying on his or her side and face, and thumping the back so that the tongue and any dentures fall forwards. This position also has the advantage that if the person vomits, as occasionally happens, the contents of the stomach pass easily out of the mouth, and there is no danger of vomit entering the trachea and lungs.

If a grand mal seizure occurs in a public place, it usually happens that someone calls an ambulance—very often to the annoyance of the person with epilepsy, who is well on the way to recovery by the time the ambulance driver delivers him to the local hospital. There is no need to call an ambulance unless it is clear that repeated seizures are occurring.

There is usually little to be done during a partial seizure, except to stand by in a reassuring manner until seizure activity ceases. Occasionally gentle restraint may be necessary in the case of complex automatic behaviour.

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THE TREATMENT OF EPILEPSY: SHOULD ANTI-EPILEPTIC MEDICATION BE GIVEN?

Posted on December 9, 2009, under Epilepsy.

A person who has had two or three seizures does not necessarily need treatment. For example, an adult who has two or three generalized tonic-clonic seizures (grand mal fits) in a two-week period and who might lose his job if he had a seizure at work requires early treatment, whereas a child who has cerebral palsy and learning difficulties and who had had two partial seizures six months apart does not necessarily require treatment with anti-epileptic drugs. Remember also that there are people whose seizures can be clearly attributed in part to a non-recurring cause. For example, seizures may begin for the first time whilst the person is on an antidepressant drug, such as amitriptyline, which is known to induce seizures in some people. Clearly the drug is not the only factor. Thousands of people take amitriptyline without having seizures. In those who do, the drug presumably acts on those with a low seizure threshold. Nevertheless it would seem reasonable to see how such a person gets on without antidepressants, before prescribing anti-epileptic medication. Other precipitating factors, if specific, such as occur in epilepsy induced by television may be avoided, and make anti-epileptic medication unnecessary.

It is therefore important that each patient is considered as an individual. The choice of whether or not anti-epileptic medication should be used is made in equal partnership between patient (or parent) and doctor. For example, a woman may wish to avoid anti-epileptic medication if planning a pregnancy even though her chances of further seizures are high.

One common decision that has to be made is whether or not to start anti-epileptic medication after a single seizure in an adult, often for which no clearly defined precipitating factor can be identified. It used to be advised that ‘one seizure did not make a diagnosis of epilepsy’. Although true by definition, the risk of a second seizure is in adults as high as 78% over the next three years, the risk being its highest in the first few weeks. Recent trials have shown clearly that an anti-epileptic drug given after the first seizure does significantly reduce the chances of a second. Patients should be offered the choice of anti-epileptic medication at this stage, with a clear explanation of the risks of further seizures and the relative drawbacks of medication, even though a number will decide to take their chances.

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TESTS IN EPILEPSY: BRAIN IMAGING INVESTIGATIONS AND THE CT SCAN

Posted on December 9, 2009, under Epilepsy.

The EEG is a ‘functional’ investigation, recording the brain’s function through normal and abnormal electrical activity. Imaging procedures or brain scans provide information about the brain’s structure, and revealing normal and abnormal anatomy. Most, if not all patients who have epilepsy need to have at least one EEG, fewer than perhaps 1 in 5 or 1 in 6 patients need to have an imaging investigation. Research is underway to determine who should be scanned.

Two types of imaging techniques are currently available in the developed world; these are the computerized tomographic (CT) brain scan and magnetic resonance imaging (MRI).

The CT scan-This is an abbreviation the computerized axial tomography (CAT) scan. The technique was developed in the 1970s and is a type of X-ray investigation. Tomography is a word dating from earlier X-ray techniques. The patient lies still on a table whilst a rotating X-ray machine takes two-dimensional pictures of the head from many different angles or positions. The information is then processed by a computer to produce pictures (or images) at different levels of the brain. The test is safe, and other than keeping the head still, there are no particular precautions to be taken. Children may have to be given a sedative drug or short anaesthetic so that they can keep still for the scan. The test takes approximately 15-20 minutes. If an area of interest is seen on the initial images, some contrast (special dye) is injected into a vein in the hand or arm and then the scan repeated. The dye may enhance contrast in areas of interest and give more detailed information. CT scanning has proved to be very useful in detecting structural abnormalities within the brain, such as strokes, infections, tumours, and congenital malformations which may cause epilepsy. However, only 20-25 per cent of patients with epilepsy referred to special centres will have an abnormal CT scan. Abnormalities on the CT scan in patients who have epilepsy are more likely to be found in the following situations:

• patients whose seizures affect only one side of the body;

• patients whose EEG shows a persistent slow wave abnormality on one side of the brain;

• when epilepsy starts in newborn babies and continues;

• when epilepsy starts in later life; and

• if the patient has abnormal findings on neurological examination, for example, mild weakness down one side of the body, or changes in the reflexes.

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THE CAUSES OF EPILEPSY: PRECIPITANTS OF SEIZURES-SLEEP AND LACK OF SLEEP

Posted on December 9, 2009, under Epilepsy.

Whatever the ’cause’, most people with epilepsy analyse their day to day lives in an attempt to detect factors which precipitate seizures.

Virtually every conceivable life event may be blamed by some people with epilepsy, who may become overly obsessional about avoiding factors they consider important. For example, a man had each of his two seizures on railway trains. He firmly believes that in some way trains make him have seizures. It is likely that this occurrence is just coincidental, but we cannot be entirely sure that he is wrong!

There are, however, a number of factors which do seem to precipitate seizures in at least some people with epilepsy.

Sleep and lack of sleep-The electroencephalogram (EEG). At this stage, it is only necessary to know that it records the changes in voltage resulting from activity of cerebral nerve cells. The EEGs of people without epilepsy change during the passage from normal wakefulness, through drowsiness, to sleep. Sleep is not constant, as judged by body movements and EEG patterns, throughout the night. At various intervals one pattern of brain waves occur in association with rapid movements of the eyes. Through waking patients at this time we know that it is during this stage of sleep that dreams occur.

The changing electrical activity of the brain during drowsiness and sleep may allow seizure discharges to ‘escape’. Indeed, those analysing EEGs hope that their patients drop off to sleep during the procedure as the possibility of recording an abnormality is considerably enhanced.

Some subjects have all or virtually all the seizures whilst asleep—but they can never be entirely sure that a daytime attack will not occur. A follow-up study of one group of people with ‘nocturnal’ epilepsy showed that about a third had a daytime seizure in the next five years. The effects of depriving people of sleep have also been studied by keeping volunteers continuously awake, or by waking them up every time the EEG showed the pattern of rapid eye movement sleep. In each case EEGs on subsequent undisturbed nights showed that the subjects were catching up on the rapid eye movement sleep they had missed. Deprivation of sleep, therefore, has been shown to alter cerebral electrical activity, and it is not surprising that this is another factor in precipitating seizures. In practical terms, repeatedly staying up late may precipitate seizures in young adults.

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HOW COMMON IS EPILEPSY?

Posted on December 9, 2009, under Epilepsy.

The incidence of a disease means the number of new cases in a defined population (usually

100 000) in a defined period of time (usually one year).

Good figures for the incidence of new cases of epilepsy come from the population of Olmstead County in Minnesota. People in this rural part of the USA do not move around very much, and have the good fortune to be cared for by doctors at the famous Mayo Clinic. Research workers there have long had an interest in identifying all patients with epilepsy.

The incidence of new cases is highest in infancy and in old age, but new cases can occur at any age. Throughout middle life the incidence is about 40 cases per 100 000 per year. As the years go by, the risk of having had epilepsy at some time in one’s life increases in a cumulative fashion. The cumulative incidence in a population of children studied in the UK was 410 per 100 000 by the age of eleven, 600 by the age of 16, and 1000 per 100 000 by the age of 23. From the United States study cited above, the cumulative risk by age 75 was 3400 per 100 000 (3.4 per cent) for males and 2800 per 100 000 (2.8 per cent) for females. Epilepsy is thus not a rare or unusual disorder; seizures may impinge upon the lives of any one of us.

Another word used in counting cases of disease is prevalence. Here it is best to consider first another common illness which has a prolonged and steady course such as Parkinson’s disease. It is quite easy (though expensive) to do a door to door survey and count the people found to have Parkinson’s disease, as the signs of it will always be apparent. Prevalence is usually expressed per 1000. The prevalence of cases per 1000 population means that this number of people have the disease on the day of the survey. This technique is more difficult for epilepsy because of its episodic nature. Clearly, common sense dictates that if someone had a seizure during a day on which a survey day was done, they should be included, but what about someone who had many seizures in the past, but none for three years? One has to judge where to draw the line. In practice, most surveys of prevalence include people who have had more than one non-febrile seizure in the past, and are on continuing anti-epileptic drugs and/or who have had at least one seizure in the last two years. After early childhood, the prevalence is more or less constant throughout life at about seven per 1000 in developed countries, and considerably higher in developing countries.

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