Saturday, January 2, 2016

What is epilepsy and how is it diagnosed?

Why this blog:
Though, there are many blogs related to epilepsy available already, many people living with epilepsy are still being misled. The reasons for such misleading information are many and beyond the scope of this blog. A blog with credible, specific and up to date information on current understanding of epilepsy and its management is need of the hour. What is better than to share one's own experience of interacting with many patients and families with epilepsy acquired over the years by treating children with epilepsy in many diverse settings. Another reason is the need to create awareness related to epilepsy where this is needed the most, the developing world where most patients with epilepsy live. The prevalence and underlying cause of epilepsy, diagnostic and treatment facilities available, and social pathology vary widely from country to country. My blog posts will focus on the issues related to the management of epilepsy in India.

What is epilepsy?
Epilepsy is a physical disease like headache, backache and asthma. It is one of the most common brain diseases in any age group. Having said that epilepsy is not a single disease, it is rather a group of very different diseases with one common denominator that is enduring tendency to have repeated epileptic seizures. Thus, seizure is a symptom and epilepsy is a disease as in fever is a symptom and malaria is a disease.

What happens in the brain during a seizure?
Brain is like a complex electrical jack box with billions of inter-wined wires and as many junctions between them. Normally, there is balanced and smooth electrical transmissions going on simultaneously in many parts of the brain. Seizure occurs due to an enormous amount of electrical impulse produced suddenly in one part of the brain, with resultant sudden and unexpected physical manifestation. The physical manifestation can be in any form related to the brain function such as, loss of consciousness, unresponsiveness, sudden falling down or violent jerking, etc. The violent jerking of one or more limbs is known as convulsions. Thus, convulsion is one specific type of seizure.

Why do seizures occur?
Any disturbance in the normal brain electrical function due to many different causes can result in seizures. The cause can be as simple as "low sodium" (hyponatremia) in elderly people above 65 years due to poor salt intake or more commonly, immediately following traumatic brain injury during a motor vehicle accident. Like wise there are numerous causes that can result in seizures.

When does the seizure become epilepsy?
The tendency to have seizures in the above two examples abates once the underlying problem is corrected (normal sodium in blood or healing of trauma) and these people have had "provoked" seizures but do not have epilepsy! But in a proportion of patients who had brain injury develop repeated seizures moths and years after the injury. This is due to the scarred brain (in the injured brain region) producing excess of local electrical impulses within the scar. This later condition is called epilepsy when the patient has recurrent "unprovoked" seizures.

What are the types of epilepsy?
There are very different types of epilepsy. It is very important to understand epilepsy in one person is very different to epilepsy in another. So, medical advise given to one person does not automatically apply to another. Over the years, many different medical terminologies are used to group together epilepsies that are similar. Still within the same group of epilepsy, many individual variabilities exist. For ease, I will use focal epilepsy and generalized epilepsy to denote dichotomy between these two groups, as is the conventional wisdom.
In simple terms, seizures in focal epilepsy arise in one particular part of the brain, for example, in the brain scar which is located in the front of the right half of the brain. Whereas, generalized seizures arise in deep brain structures so that most parts of the both sides (hemispheres) of the brain are involved concurrently. Distinguishing between focal and generalized epilepsies is very critical for diagnostic tests and treatment approaches. I will discuss focal epilepsy and other specific types of epilepsy in my subsequent blog posts.

How is epilepsy diagnosed?
Epilepsy is a clinical diagnosis, ie, epilepsy is diagnosed by your doctor after carefully analyzing your symptoms (seizures) to decide if these are indeed unprovoked epileptic seizures. Most important thing here is not all episodes of loss of consciousness/unresponsiveness and shaking are seizures. There are many other phenomena that can be similar to seizures (seizure mimics). Video recordings of the episodes in question, if available, help doctors distinguish between seizures and mimics in many cases. Rarely, video-EEG recording of seizures in hospital is required to make this distinction when in doubt.

What tests are performed in cases of epilepsy?
As I mentioned earlier, epilepsy is a clinical diagnosis and there is no test that will confirm or rule out epilepsy. Tests are usually performed to support the diagnosis (EEG), to know which type of epilepsy one is dealing with (EEG/video-EEG) and to detect the underlying cause of epilepsy (MRI, other brain scans and other tests). The interesting point to note here is that all these tests can be normal in patients with certain types of epilepsy!
Thus, having normal EEG and normal brain scan does not rule out the diagnosis of epilepsy! This is because, the underlying cause of epilepsy may be genetics (known or unknown gene aberration), the gross brain structure may be normal in most such cases. The abnormally excess brain electrical activity is many a times intermittent ie not occurring constantly all the time. So the routine EEG (brain wave test) recorded for 40 minutes or so can miss the abnormality completely. When the seizure focus is very deep down in the brain, EEG may not detect any abnormalities. To make things tricky, EEG may show abnormalities that are unrelated to the patient's episode in question. This brings us back to the same point that epilepsy is a clinical diagnosis and the test results should be interpreted judiciously in the clinical context .

Hope some of your questions are answered in this blog......queries and comments are welcome.

Catch you with my next blog soon....

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