Test For Epilepsy

It is a useful test for the diagnosis of epilepsy, where the report of an eyewitness is not either completely available, or is not available at all. But, in such cases, a word of caution. The EEG must be read very carefully, and the guidance of a specialist must be obtained, so that a non-epileptic person may not be labelled as a case of epilepsy, which will be indeed very unfortunate for the patient.

In some cases, where the EEG is negative, and the patient is still strongly suspected to be a case of epilepsy, EEG recordings are done after showing a flash to the patient (photic stimulation), and/or asking the patient to deeply breath (hyperventilation), or the EEG is recorded when the patient is instructed to be awake the whole night before the test is taken (called sleep-deprivation EEG), as under these circumstances there is a possibility of a positive graph. But again, a careful analysis of the EEG is required by an expert to exclude falsepositive results. In any case, if the EEG is grossly abnormal, risk of repeated attacks of epilepsy must be explained both to the patient and his family members, so that he remains under observation all the time till the attacks are controlled with specific treatment. An EEG is equally important for the diagnosis of childhood epilepsy.

In selected cases, a 24-hour continuous ambulatory recording of EEG may be taken on the same pattern as the Holter test, done in heart patients to see the various irregularities in the rhythm of the heart (arrhythmias). In such a continuous record of EEG, the chances of a positive graph increase, as the recording is for a considerable length of time, which increases the chances of detection of any abnormality in the graph. However, this test too has got its own limitations.

Hence, the value of clinical diagnosis and the true report of an eyewitness should be emphasized again.

Computed tomographic (CT) scanning

A computed tomographic (CT) scan is, indeed, a valuable, non-invasive test in detecting the causative lesions in cases of epilepsy, especially in cases of brain tumours. Besides tumours, the test is also useful in diagnosing other causes of epilepsy, like post-traumatic scarring/gliosis or porencephaly, i.e. cavity in the brain, tuberculoma (due to tuberculosis), cysticercosis (due to ingestion of infected pork), or cerebral infarction (due to occlusion/thrombosis of one of the vessels of the brain).

However, again a very careful interpretation is required for reading a CT scan for the diagnosis of a shadow /s, as it has been shown in various studies that following an attack of epilepsy, temporary shadows (disappearing in about 1-3 months) of varying sizes may appear in the brain. But such a diagnosis may not be free from danger, as such shadows may be pathological, more so, malignant, and therefore, a close follow-up is necessary, and repeated scans may be required to check if the lesion is lessening, persisting or increasing, so that no time is lost in carrying out life-saving treatment. At the same time, unnecessary treatment/ panic may be avoided.

Such lesions/shadows may probably be due to post-epileptic oedema/ swelling of the brain.

However, for a neurologist, such lesions create no problem for reaching a precise diagnosis, and, above all, the picture is seen as a whole, i.e., all accounts/aspects of the case are taken into consideration - the clinical manifestation of an attack of epilepsy, age of the patient, EEG report, and follow-up reports.

In several hospitals, special epilepsy clinics are being run where a large number of cases are seen/followed up weekly / fortnightly and, therefore, with experience, such problems are tackled in a routine manner, but may create a genuine difficulty, at times, for a general practitioner who may need the urgent opinion of a specialist.

Magnetic resonance imaging (MRI)

This test is more sensitive than a CT scan, and, therefore, in doubtful cases, it must be carried out, especially when a CT scan is not contributory, and there is no satisfactory improvement in the condition of the patient, in spite of a potent drug therapy for epilepsy.

Other tests may also be required, such as the examination of stools for worms, especially for pork tapeworm (Taenia solium), X-ray of both the calf muscles, below the knee, for the presence of calcified cysts of cysticerci, especially in places where the incidence of epilepsy is common as a result of taking infected pork. Worms in the gut, in general, irrespective of the type, may precipitate an attack of epilepsy, especially among children.

Needless to say that investigations have a definite role in suspected epilepsy, more so for the detection of possible lesions and their cure. Many of the cases of epilepsy are idiopathic, i.e., where no cause is available, requiring a long course of drugs, and in a very few, even a lifelong maintenance dose may be required.


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