Types of Motor Neuron Disease :
1. First of all, let us discuss about the primary (idiopathic) motor neuron disease, which occurs due to unknown reasons. In this, the main defect is in the motor neurons, and so the anterior horn cells from which the nerves of the spinal cord originate, and the brain stem or the bulbar neurons from which the cranial nerves emerge, are gradually destroyed due to some unknown reasons.
2. The muscles in the hands and legs start wasting and the movement becomes less. There is difficulty in holding things, writing or moving the hands up and down and gradually climbing stairs and even wearing footwear also becomes difficult. In 3 to 7 years of the onset of the disease the patient becomes completely bedridden and the body weight reduces drastically. This type is called Amyotrophic Lateral Sclerosis(A.L.S.). In this, the anterior horn cells of the spinalcord as well asthe pyramidal fibres, which control the spinal cord, are affected. In neurological language, in this disease signs of both upper and lower motor neuron dysfunction are seen (on examination).
3. Progressive Muscular Atrophy is a type of motorneuron disease in which the pyramidal fibres are not affected and thus the neurological signs of upper motor neuron are not seen (like brisk jerk, extensor plantar etc). This is comparatively a slow -evolving disease.
4. As mentioned earlier, in Bulbar Motor Neurondisease, the cells from which the cranial nerves emergeget afflicted and so important functions like swallowing food, and speech etc get affected and there is difficulty in respiration. In this, the death occurs quickly within 1 to 3 years.
5. Pseudobulbar Palsy is related to A.L.S. and is adisorder of the cranial nerves in which as mentioned earlier swallowing, speech and some other functions are affected. Involuntary laughter, crying etc. like peculiar symptoms may also be seen.
6. In some cases by chance the disease is limited to a single limb, which is known as Monomelic MotorNeuron Disease. Associated deafness, which is notpresent in other motor neuron diseases, is noted in Madras Motor Neuron disease.