Wednesday, September 7, 2011

Amyotrophic lateral sclerosis

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Amyotrophic lateral sclerosis is a degenerative motor neuron disorder caused by the degenerative changes occurs on the neurons at the ventral horn of the spinal cord as well as on the cortical neurons. This condition is also known as Lou Gehrig’s disease as this was first observed in a famous baseball player named Lou Gehrig.
This is a progressive degenerative disorder characterised by rapidly progressing muscle weakness, atrophy, spasticity, dysarthria, dysphagia and finally respiratory compromise. Patients with Amyotrophic lateral sclerosis dye of respiratory compromise and pneumonia within 2 to 3 years.

Amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis

Epidemiology

Amyotrophic lateral sclerosis is the most common neuromuscular disease and people with all races and ethnic backgrounds are affected. Two in one lack people are affected every year worldwide. People with 40 to 60 years of age are mostly affected.

Signs and symptoms

Muscle weakness and atrophy of muscles that is progressive in nature.

Loss of control of all voluntary muscles except bladder and bowel sphincter muscles and muscles responsible for eye movement.

Initial symptoms

• Muscle weakness and atrophy
• Muscle twitching, cramping and stiffness
• Slurred and nasal speech
• Initially limbs are affected causing tripping or stumbling or dropped foot.
• When arms are affected, it causes inability in simple tasks like buttoning a shirt, writing etc.
• When other systems are affected, symptoms like difficulty in speech and swallowing are noticed. Loss of mobility of tongue also occurs.

Progression of the disease

As the disease progresses symptoms worsens. Patients will not be able to walk and move hands. They become bed ridden. There will be risk of choking and aspiration of foods as the disease progresses. Weight loss and nutritional deficiency occurs as the patient is not able to take food by mouth. A small percent of people develop dementia as a result of fronto- temporal involvement. Cognitive abilities are not affected in most of the patients.

As the muscles of diaphragm and ribs that are essential for breathing are involved, breathing will become difficult and patient may develop pneumonia. Usually death is due to breathing difficulty and pneumonia.

Cause

In 95 per cent of the cases the cause is unknown and there will be no family history of the disease. In patients with a family history of Amyotrophic lateral sclerosis, the cause is due to any genetic disorder. In 20 per cent of patients with family history of amyotrophic lateral sclerosis, there will be a defect in chromosome 21 that causes the disease.

There are several risk factors identified and are:

1. Exposure to dietary neuro toxin called BMAA which is produced by Cyanobacteria.
2. Use of pesticides that are neurotoxin.
3. Some performance enhancing drugs used by athletes may cause amyotrophic lateral sclerosis

Diagnosis

Disease is usually diagnosed based on the presentation (signs) of the disease and based on the neurologic examination.

Magnetic Resonance Imaging may reveal increased T2 signal within posterior part of internal capsule.

Electromyography is performed to inspect the electrical activity in muscles.
Nerve conduction velocity test is done to rule out possible peripheral neuropathy or myopathy.


Treatment

Slowing disease progression

Riluzole is the only drug of choice used to reduce the damage of motor nurons. This drug also offers some neuro-protective effects.

Symptomatic Treatment

Medications to control increased salivation are prescribed if needed. Pain , constipation, sleep disturbances and depression are managed with appropriate drugs. Physical therapies are performed to delay muscle atrophy and loss of muscle strength. Support for speech and language are also given. As respiratory compromise occurs, respiratory support with tracheotomy may be done.
Prognosis

Most of the patients will die on respiratory failure within 2 to 3 years and 10 to 20 per cent patients may survive longer than 10 years.

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