SUPERnegro.com Medical Blog

December 16, 2009

TESTS IN EPILEPSY: OTHER IMAGING TECHNIQUES

Filed under: Epilepsy — admin @ 12:10 pm

Before the development of CT scanning, simple skull X-rays or air-encephalograms (in which the structure of the brain was outlined by injected air) were the only techniques available. These have been superseded entirely. Another technique, angiography, is still used in some patients with epilepsy due to a structural cause. In this technique, an iodine-containing solution which is opaque to X-rays is injected directly into one or other carotid artery (in the neck), or through a catheter introduced into the brachial (elbow) or femoral (groin) arteries and passed into the region of the carotid. Immediately after the injection, a series of X-ray pictures are taken which outlines the arteries and veins containing the iodine solution. This technique identifies precisely any abnormal blood vessels and may be extremely valuable if surgery is being considered on an angioma or tumour. Advances in MRI mean that the circulation can usually be imaged by special pulse techniques and image processing software, so angiography is likely to be superseded in the near future.

Other imaging techniques are available at research centres. These include positron emission tomography (PET), or single photon emission computerized tomography (SPECT). In these procedures, variations in function in different parts of the brain can be imaged.

The technique involves injecting a glucose solution, or breathing oxygen, either of which is labelled with a specially marked atom. The oxygen or glucose is taken up and metabolized by different parts of the brain at different rates. The marker atoms attached to the oxygen or glucose allows images to be obtained which may show an area or areas of the brain which take up a lot of oxygen and glucose during a seizure, and which could be an epileptic focus. Between seizures, the same areas are relatively silent. Such studies may help neurologists and neurosurgeons decide on the suitability of a child or adult for epilepsy surgery.

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THE FIRST SEIZURE AND THE DIAGNOSIS OF EPILEPSY: IS REFERRAL TO A SPECIALIST NECESSARY?

Filed under: Epilepsy — admin @ 12:08 pm

Most referrals occur not because family doctors are uncertain as to whether a patient has had a seizure or not, nor because they are seriously concerned in every case about the possibility of serious underlying disease, but for the following reasons:

• People do not like being told they have had an epileptic seizure. One survey showed that this difficult task is left to the hospital doctor in about half the cases.

• People with epilepsy themselves very often feel that some sort of special test is necessary to ‘prove’ the diagnosis. It must be very difficult to accept the diagnosis, with all its social implications, when it is made on the basis of a 30-second description given to a doctor by a relative or bystander. Somehow it does not seem ’scientific’ enough, and yet paediatricians and neurologists place enormous weight on the recounted stories.

• People with epilepsy are very concerned to discover the ’cause’ of their epilepsy. A cause is often not found, but most people think in terms of a single cause, which they believe, if eradicated, will result in the problem being solved once and for all. Occasionally, of course, an important treatable cause is found, and usually special tests are indeed necessary to show this. The difficulty lies in deciding which patients should be so investigated.

• Traditional medical textbooks accentuate the unusual and ‘interesting’ causes of epilepsy, at the expense of the more usual patients. Family doctors, educated partly by these books, tend to play safe and refer if referral centres are available.

• The necessary decisions are quite complex. There are three possible preliminary

diagnoses—seizure, not seizure, and may be seizure; two policies about investigation—to be arranged or not; and four possible outcomes—treatment, no treatment, adoption of a

wait-and-see policy, and referral to another specialist. We do have some sympathy with our colleagues in primary care, when all these combinations are considered, and can readily understand why so many patients are referred.

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THE DIFFERENT TYPES OF EPILEPTIC SEIZURE: RARER TYPES OF SEIZURE

Filed under: Epilepsy — admin @ 12:04 pm

Atypical absences (petit mal variant)-This phrase is used in two different ways—to describe absences which are clinically similar to typical absences associated with an EEG record that is not typical, and to describe absences in association with other features which are not typical, of which loss of postural control is the most marked. In these fortunately unusual so-called ‘akinetic drop attacks’, children may crash to the floor with such force and frequency that they have to wear a crash helmet to protect the head from damage.

Clonk seizures-The distinction between these and myoclonic jerks is slight. If jerks are multiple, then the seizures tend to be called clonic.

Tonic seizures-A tonic (rigid) posturing of all limbs without a clonic phase is sometimes seen in some generalized cerebral disorders in childhood. The same name is given to one rare form of partial seizure in which one part of the body briefly maintained abnormal tonic posture. Such seizures may occasionally occur in adults with multiple sclerosis.

Infantile spasms (salaam seizures; West’s syndrome)-These seizures of infancy are characterized by a brief, sudden flexion of head, trunk, and limbs, as if the baby is bowing a ’salaam.’ The infant may appear to be thrown forwards or backwards with the arms outstretched. Each spasm lasts about one second or less. The spasms may occur in runs or clusters

(up to 40-50 spasms per cluster) over a 5-10 minute period; when this happens the infant may appear distressed afterwards and cry. Spasms are more likely to occur at certain times of the day, either just after the infant has woken up from a sleep, or is about to fall asleep. In some children, the spasms may occur almost continuously throughout the day, happening several times an hour. The EEG in infants with this type of seizure shows very abnormal patterns of activity called hypsarrhythmia.

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