MOVEMENT DISORDERS AND DYSTONIA
The movements of the human body are mostly voluntary and are dependent on three major groups of neurons & tracts, each of which comprises a different system.
i. Pyramidal system.
ii. Para pyramidal system.
iii. Extra pyramidal system.
The first system is the most important of them all. The hindrance in the normal working of this system leads to paralysis, i.e. defect in the neurons causes the organs to stop functioning, gradually leading to spasticity.
1. Pyramidal system arises from the neurons of theposterior portion of the frontal lobe of the brain and the anterior part of the parietal lobe, which form the corona radiata, and passes through the posterior portion of the internal capsule situated between the basal ganglia. [Please see picture: 2 chapter: 1 ]. It then passes below ‘the cerebral peduncle forming the pyramidal tracts. These tracts decussate in the medulla and pass to the contra lateral halves of the spinal cord, as the crossed lateral corticospinal tracts. These end into the cells of the spinal cord, known as anterior horn cells. It is these lower motor neurons that ultimately control the movement of the limbs. The orders from the brain are sent through these lower motor neurons so that the movement of the body is initiated. This entire process is completed in less than a second. Thus the frontal lobe of the brain is the main part of the entire system. Also -along with this there is another part of the brain known as supplementary motor cortex that generates messages before movements. The contribution of this part is also very high. Any damage to the pyramidal system results in paralysis.
2. The Para pyramidal system mainly consists of rubrospinal, tectospinal, reticulospinal, and vestibulo-spinal tracts. Its main function is to influence the pyramidal system in such a way that voluntary movements are conducted in a particular systematic way. Red nucleus, tectum etc. various parts of the brain are associated with it. Any damage to it results in symptoms like imbalance, tremors etc.
3. The diseases we are going to talk in this chapter are called movement disorders. The nuclei or cluster of cells affected in these disorders are chiefly basal ganglia which are situated in the middle of the brain on either side. This system is called extra pyramidal system. We will discuss the diseases known as movement disorders. The neurons present in the middle part of the brain called basal ganglia perform a very important activity and form the extra pyramidal system.
As shown in the picture the system consists of frontal lobe, globuspallidus, putamen, caudate nucleus, claustrum and amygdala etc. This system controls the pyramidal system in its own way. Any fault or cessation of function of this system does not produce paralysis but can create two types of problems which we call as syndromes.
a. Akinetic rigid syndrome (Parkinsonism- which will be discussed in detail in the subsequent chapter) in which there is stiffness of limbs and all functions become slow, there is also trembling in the limbs and all movements becomes slow. This occurs due to the deficiency of a chemical called dopamine in the brain.
b. Hyper kinetic disorders: In short, an excess of dopamine in the brain results in hyper kinetic disorder. Here uncontrolled extra movements like dystonia, chorea, dyskinesia and hemiballismus accompany the voluntary movements.
If any movement continues in the same abnormal posture for a long time then it is called dystonia. If the neck remains pulled and bent towards one side then it is known as cervical dystonia (Torticollis). If the eye and facial muscles are pulled towards one side again and again, it is calledhemifacial spasm. If the eyes keep closing involuntarily, especially if it becomes difficult to keep the eyes open while talking to someone, it is calledblepharospasm. If the surrounding parts of the mouth or the tongue move abnormally then it is called facial dystonia or meige’s syndrome.
Another condition known as writer’s Cramps is a well known disease. In such cases the patient suffers from writing problems. Initially there is deterioration in handwriting.
The writing speed becomes less. And eventually the patient cannot even sign his name. People like clerks and teachers who have to write a lot, find it very difficult to cope in their profession or job. For example if an executive has difficulty in signing cheques then they may bounce or if there is a difference in the signatures on contracts, it may lead to serious trouble. And the interesting part is that the patient suffers from difficulty only in writing. He may not have any problems in eating or holding objects and there are no symptoms of paralysis. Other Dystonia are similar. In a similar way if the voice thins, down or the person has problems in speaking, it is called vocal cord Dystonia.
According to an opinion, there are more than 100 types of such Dystonia. If a violin player suffers from a finger Dystonia, the musician can lose his name, fame and living. If a tabla player suffers from a finger Dystonia, the music rhythm can change completely. One can thus imagine how this disease can affect careers.
This Dystonia occurs due to defects in the working of basal ganglia. Due to an increase in dopamine, the movements of the patient increase or some muscles constantly remain contracted causing disruption in rhythmic movements and as a result the trouble occurs.
The above mentioned Dystonias are usually primary and normally occurs in young people. The reason for this is unknown. This can occur due to either mental tension or repeatedly and continuously doing the same work (like writing). But why it happens to only a few of such innumerable people doing similar work is still not known. It may be possible that the disease occurs due to the combination of various factors related to genetic or hereditary reasons, environment as well as the lifestyle, food habits or psychological makeup of the patient.
Whatever may be the causes, it is equally difficult to treat such cases. Medicines for such kind of diseases are given on the basis of inference, as the cause is unknown. For example trihexiphenydil, haloperidol, benzodiazepines (like Clonazepam), tetrabenazine etc. are given either as a single dose or in combinations. The dose also varies from patient to patient. But these drugs are effective in only 30% to 40% of cases and that too not completely. The drug is effective only till it is taken and the patient feels better temporarily. With passage of time the effectiveness of the drugs decreases. But the side effects of these medicines are a cause of concern especially for young patients. Therefore, doctors are advised to use them with discretion and not prescribe them extensively.
Instead of these drugs, a novel treatment called Botulinum injection (botox), which when injected in the muscles in an appropriate dose gives good results in various types of Dystonia. It has been found to be miraculously effective in all the above-mentioned Dystonia, from cervical Dystonia (Torticollis) to blepharospasm, hemi facial spasm, writer’s cramps etc.
Neurologists trained in using these injections are there in Delhi, Mumbai, Ahmedabad, Kolkatta and many other places. They decide the dose and location of the injection to avoid side effects. For example, it is given particularly in the muscle where there is maximum contraction so as to bring it back to normal. The functioning of the muscle becomes normal and the pain is relieved, cosmetically too it helps the patient and he or she can return to his or her routine job.
This injection is moderately expensive and at present the treatment cost of hemi facial spasm is around Rs. 4,000 to 5,000 and for blepharospasm it is around Rs.6,000. It has to be administered every 4 to 6 months as its effect gradually diminishes. Sometimes it is difficult to identify the muscles affected and a test called E.M.G test has to be done to locate these. If an excessive dose is given, the muscles become weak for a few days, like the eye-lid drooping over the eye (in case of blepharospasm the injection is given in the eye-lids). Therefore, it is essential to take this injection from a neurologist or a specially trained physician.
These Botulinum injections are available as Botox, Portox injections. They form such a bond at the presynaptic cholinergic terminal of the synapse* (the junction where the two neuron meet) that the muscle fibres controlled by these nerves undergo functional denervation and weaken them. This weakness lessens gradually. The treatment by botox injection is rapidly gaining recognition even in cases where there is contraction or pain in the muscles without dystonia. It is also effective in the spasticity and abnormal posture occurring due to paralysis. But the effectiveness of this injection decreases in 4 to 6 months This injection is also useful in the treatment of other problems ranging from spasticity due to cerebral palsy, muscular pain and even cosmetic purpose like wrinkle removal. The dosage can range from 2 units in small muscles to 150-200 units.
Dystonia can be controlled to a large extent by drugs as well as Botulinum toxin injections and necessary surgery can also be resorted to. Surgery includes Rhizotomy, denervationprocedure etc. In some cases spinal cord stimulation can be done. While in some cases of dystonia the exterior belts (splints) can also be used.
Some cases of Dystonia are called secondary Dystonia. In this case there are some defects in the brain like congenital metabolic disease of the cells, Wilson’s disease, Dystonia musculoformans, brain tumor, blood disorders, side effects of drugs etc. Once these causes are cured Dystonia is cured too. But many of them however, cannot be controlled.
Apart from Dystonia, there are many other important movement disorders.
If a difficulty arises in the working of caudate nucleus situated in the basal ganglia, it causes a series of jerky, quasi-purposive movements of the limbs, neck face, etc. which often occur from one part of the body to another, again and again in the same order.
1. Chorea that occurs due to rheumatic fever.
2. Huntington’s chorea (hereditary).
3. Senile chorea.
4. Chorea that occurs in diseases like diphtheria, whooping cough, rubella etc.S.
5. Chorea due to increase in thyroid.
6. Neuroacanthosis Chorea.
7. Chorea due to side effects of the medicines especially drugs for mental disorders, contraceptive pills, lithium, antiemetic drugs (for vomiting), mercury poisoning etc.
As described earlier chorea occurs due to an increase in the levels of the chemical dopamine and so drugs like’ haloperidol, chlorpromazine, tetrabenazine, reserpin etc. (that oppose dopamine) are used.
Shaking of fingers of the limbs and sometimes of the neck and lips in a continuous, rhythmic manner is called tremors. This is the most common movement disorder. Y
Many a times it may also occur in normal people due to tiredness, lethargy, drug side effects, intake of coffee or pregnancy. The medicines that can cause tremors as a side effect are steroids, theophylline (used for asthma); lithium, tricyclic or antipsychotic drugs (used for mental diseases) and valproate (used for seizures). Tremors may also occur due to an increase in the levels of thyroid hormone.
In many cases tremor can be hereditary which is called familial essential tremor. Some people also experience tremor because of old age. Tremor is one of the main symptoms of Parkinson’s disease.
Different medicines are used for the treatment of tremors caused by different reasons. They are beta blockers (propranolol), diazepam, clonazepam, gabapentin, primidone, etc. and dopaminergic drugs for Parkinson’s disease. In selective cases surgery can also be done.
Repeated, quick, habitual movements are called tics. 5 % of the children have the habit that cures itself as they grow up. This can ‘,also happen due to side effects of medicines or viral disease. However, the worst form of Ticsis seen in Gilles de la Tourettee Syndrome. It accompanies behavioral changes, (ADHD, OCD) and utterance of obscenities is also seen. This should be treated accordingly.
The movement disorders occurring due ‘to theside effects of some modern medicines can be summarized as under:
Dyskinesia: Dystonia or chorea that occurs due to medicines like phenothiazines, levodopa etc
Dystonia: The sustained contraction state of the limbs occurring due to the drugs of neuroleptic group 3. Akathisia: An uneasy state due to the use of antipsychotic medicines.
Parkinsonism: For example haloperidol; Parkinsonism occurring due to medicines for psychological disorders.
Chorea: Due to contraceptive pills
Neuroleptic Malignant syndrome: The severe reaction occurring due to anesthesia during surgery.
Tardive dyskinesia: Chorea or dystonia occurring due to the long-term usage of neuroleptic medicines.
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