Motor Neuron Disease is a group of neurological disorders. They affect the motor neurons which control the voluntary activities and the movement of the body. It is also called as Lou gehrigs disease.
Motor Neuron disease is classified as follows:
- Wernig- Hoffman disease (Infantile spinal muscular atrophy)
- Kugelberg – Welender disease (Adolescent spinal muscular atrophy)
- Amyotrophic lateral sclerosis (most common)
- Progressive muscular atrophy.
- Progressive bulbar palsy
- Primary Lateral sclerosis
About 90% of Motor Neuron Disease is sporadic. While 10% are familial or by genetic mutation associated with the disease. There is loss of motor neurons and gliosis in motor neurons and motor nuclei of brain stem and anterior horn of spinal cord. There is degeneration of corticospinal tract in spinal cord.
The symptoms are usually seen between ages of 50 to 70. There is weakness, wasting, fasciculation, spasticity and stiffness of muscles of arms and legs.
It has insidious onset and steadily progressive course. Widespread fasciculation are common but there is no sensory or bladder involvement. The Four patterns are recognized which later merge with each other.
Progressive Bulbar Palsy is characterized by Dysarthria, Dysphagia and Dysphonia. There is low volume of speech with difficulty in swallowing and horseness. The tongue is characterized by wasting and fasciculation and spasticity of muscles is observed. There is presence of emotional Lability with uncontrolled laughter and crying.
Amyotrophic Lateral Sclerosis (ALS) is characterized by death of nerve cells which can no longer send signals to muscles. They do not affect the senses but affect the bladder and bowel along with ability to think or reason.
Weakness and wasting of small muscles of hands are early signs of ALS. There is difficulty in breathing and swallowing. Head drops due to weakness of neck muscles. Patient presents with paralysis, speech problems, hoarseness in voice and weight loss.
Progressive Muscular atrophy the occurrence ratio Male: Female is 5:1. There is involvement of only lower motor neurons. The early sign is foot drop which unilateral but as the disease progress it is bilateral. The later manifestations include wasting and weakness of hands. The deep tendon reflexes are lost or are totally absent.
Primary Lateral Disease is a rare form of Motor Neuron Disease, the features of which are restricted to upper motor neurons. There is progressive tetraparesis with terminal pseudo bulbar palsy.
Diagnosis of Motor Neuron Disease is done by Blood tests, Electromyography (EMG), Nerve conduction velocity, Magnetic Resonance Imaging (MRI) of spine, Assessing the thyroid functions. The other investigations include Lumbar puncture and Tran cranial Magnetic Stimulation.
Treatment: There is no as such cure for Motor Neuron Disease but the drug riluzole, a sodium channel blocker, can be used which blocks the effects of neurotransmitter Glutamate and extends the life span of the affected patients. The treatment emphasizes on relief of symptoms associated with the disease.
Walking aids, wheel chair and Physiotherapy are other treatment methods for Motor Neuron Disease.
The patients of Motor neuron disease at their last stage present with Anarthria which is severe dysarthria resulting in speechlessness, Aphagia and widespread limb weakness with full consciousness. Death occurs from Pneumonia or Respiratory failure. The usual duration of survival in bulbar palsy is about 2 years, ALS is 4-5 years while PMA is 8-10 years.
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