Headache, which could be migraine, or due to tension, is the most common neurological disorder. Next to headache, epilepsy is most prevalent, with around 5.7 people in every thousand in cities, 11.9 (in a thousand) in villages and overall, around nine in every thousand being affected. About three percent of the population suffers from neurological disorders and approximately one third of this section suffers from epilepsy. There are also other disorders like stroke, Parkinson''''s disease, mental retardation, tremors and muscular dystrophy.The spread of neurological disorders can be determined either through the hospital statistics or through community-based health service. But the exact magnitude is determined by population surveys. In the urban areas, it is about 23 per thousand, while in the rural it is about 43 per thousand.
What is the cause for such a difference in numbers between the rural and urban areas?
Though this has not been scientifically analysed; one can presume that it is because health services in villages don''''t match those in cities. Childbirth may not be properly monitored and children may be born with defects leading to mental retardation. Infections in childhood may not be well controlled and the general health may not be as good as those of children in urban areas. We have to now take every disease and look at the risk factors.
Headache was once considered more common in the urban areas than in the rural areas. But this has been proved otherwise, because it is observed that even in rural areas there are several women who suffer from headaches. Tensions may be due to different factors like socio-economic causes, poverty or large families.
Which age group is affected most with the disorders you have just mentioned?
One has to be disease specific when it comes to age groups. Epilepsy normally affects the younger age group, while cerebrovascular disorders are found more in the older age group. Although epilepsy is common among the young, even old people can be affected by it.
To what extent can these neuro disorders be brought under control?
In the case of epilepsy, 75-80 percent can be managed with anti-epileptic drugs like phenobarbitone, carbamazepine, phenytoin and valproate, which are easily available and affordable. These are the first line of drugs and we do not need to administer newer anti-epilepsy drugs, which are expensive. The treatment has to be continued for a period of three years or as the case may demand. Under supervision, the dosage could be reduced or even the treatment could be ceased.
Around 20-25 percent of the epilepsy cases, which are refractory, needs specialised treatment from institutions like NIMHANS. Doctors will have to make detailed studies on them and understand the nature of the lesions, administer the second line of drugs, which are a little more expensive, to control the disorder.
Only 10 percent of the cases require epilepsy surgery, a pre-requisite being demonstration of epileptic focus on EEG and lesion on MRI. If there is a detectable lesion, then it could be removed after ensuring that it does not interfere with other functions. There are specially trained neurologists and neurosurgeons in India who evaluate the cases. worldover, it is known that 50 percent of the epilepsy cases do not come to the hospitals and continue to suffer. The fear and stigma of epilepsy should be removed.
How can this be done?
By increasing public awareness through lectures, seminars, discussions and education of teachers in schools/colleges that epilepsy is not caused due to evil spirits or other mystical powers or influences.
Scientific research has shown that there is a biological basis to the disease and there are effective drugs to control the seizures. If the myths and misconceptions about epilepsy are removed, then people need not hide the fact that they have epilepsy and realize that they can cure themselves with drugs.
Could you tell us something about other neuro disorders?
Stroke or cerebral vascular disorder is another preventable disease and occurs when the blood flow to the brain is decreased, leaving the patient paralysed or causing speech defects. Common risk factors are blood pressure, smoking, diabetes and obesity; which is similar to heart diseases. Infections of the brain are very common in India compared to developed countries. Tuberculosis of the brain and parasitic diseases, Cysticercosis are frequently observed. Cysticercosis causes fits and several neurological defects. There are drugs for treating this condition, but the most important aspect is the need for improved public health and sanitation. The high prevalence is cause for concern in India, Mexico and Brazil where hygiene is poor. The disease is eminently preventable by simple measures to improve sanitation and hygiene.
The other infection is Japanese encephalitis. There have been repeated outbreaks of Japanese encephalitis in Karnataka, West Bengal and Uttar Pradesh. It can also be prevented by controlling the mosquito population and by isolating pigs from human habitation.
The brain is a very important target organ for the infections to strike. The neurologist is challenged by all these problems and other problems, which are occurring in developing countries like epilepsy, stroke and Parkinson''''s disease, etc.
What about hereditary factors contributing to the disease?
Yes, there are diseases which have a definite genetic base like muscular dystrophy, spino-cerebellar ataxia, Huntington''''s disease, spinal muscular atrophies that are rare compared to epilepsy or headache. Large number of other disorders has been demonstrated to have a genetic basis.
How will mapping of the human genes help neurologists or the public?
We are the utilisers of this information. From the clinical point of view, a number of neurological disorders do not have a cure, e.g. muscular dystrophy, therefore the attempt is to prevent it. Duchenne Muscular Dystrophy (DMD) is a progressive disorder leading to difficulty in walking and other activities, confinement to wheel chair or bed, and death by the age of 20-25 years. Since the abnormality is on X-chromosomes, boys are the affected ones.
Could you briefly tell us about the findings you have made regarding muscular dystrophy and about the project taken up for the identification of genes that contribute to this disorder?
Step one would be to identify specific genes for a specific disease. The next would be to find out the protein or an enzyme abnormality as a consequence of deletion or mutation of genes.
In the case of DMD, it is known that there is an abnormality in the mutation -- a deletion that affects the X chromosome and that codes for a protein called dystrophin. It is also known that dystrophin which is present in the muscles of healthy individuals provides stability to the muscle membrane. Therefore, if dystrophin is absent or dropped or reduced, one gets a muscle weakness. Then, from natural history, it is known what happens to the patient. It is also clear that the mother or the sister could be the carrier because it is X-linked and it comes from the female.
Now, there is information to see if the carrier can be detected. So one could even do pre-natal diagnosis taking the biopsy tissue from the mother''''s womb and examine whether that has the same delesion as the previous child who was born with the disease. This is predictive neurology and has worked well for some disorders where the inheritance factor is very clear. We know it is a single gene disorder and we know whether it is a protein or an enzyme. But problems would come where there are multiple genes involved in such a disorder. Then it will be more difficult to tackle this. For instance, for hypertension or diabetes, which are called poly-genetic in their origin, doctors cannot offer such a clear-cut kind of advice.
There are also other disorders like behaviour disorder and manic depression called bipolar disorder, where one could identify a gene. But for these conditions, there are a lot of environmental factors and other issues, which determine the behaviour of the individual.
What is the advantage of the Human Genome Project?
Once specific genetic abnormalities are identified, diagnostic tests could be developed for precision in diagnosis. Another benefit is that it offers drug targets and the scope for drug development and modification of existing drugs. This is what scientists all over the world and India are waiting and hoping for, to offer better treatment to the suffering humanity.
Information about human gene will help in providing precise DNA based
diagnosis, detect healthy carriers of gene abnormality, facilitate counselling and thus lead to predictive and preventive neurology.