|MOTOR NEURON DISEASE-FINAL MBBS REVISION MATERIAL
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|Author:||lakshmidr [ 16 Feb 2019 12:40 ]|
|Post subject:||MOTOR NEURON DISEASE-FINAL MBBS REVISION MATERIAL|
DEFINITION & OVERVIEW
• Motor neuron disease (MND) refers to a group of conditions wherein the nerves in the brain and spinal progressively lose their function.
• The main symptoms include progressive weakness of the various muscles of the body and eventually the respiratory muscles with respiratory failure
• Motor neurons are nerve cells that convey electrical impulses to the muscles to stimulate movement of the desired muscles
• The condition is fortunately rare but is progressive and currently has no cure. However supportive and symptomatic treatment can improve the person’s quality of life
• The condition may be diagnosed at any age but most cases are above 40 years. Men are affected more commonly than women
TYPES OF MND
MND is classified into several types based on whether they affect upper or lower motor neurons, the initial symptoms, the age of onset and prognosis. These include
Amyotrophic lateral sclerosis (ALS), or Lou Gehrig's disease – This is the most common type, and affects muscles of the arms, legs, mouth, and respiratory system. It affects both upper and lower motor neurons. Average survival following diagnosis is 3 to 5 years, but some people live 10 years or more with supportive care.
Progressive muscular atrophy (PMA) – The condition progressively causes muscle wasting, especially in the mouth, arms, and legs. It involves only the lower motor neurons. Prominent symptoms include progressive weakness but signs of UMN lesions such as rigidity are absent. It has a better prognosis than ALS
Primary lateral sclerosis (PLS) – It is a rare form of MND that progresses more slowly than ALS. It involves the upper motor neurons. Although not fatal, it can affect the quality of life. It tends to progress more slowly than ALS, and patients commonly live upto 20 years following diagnosis. In children, it is termed juvenile primary lateral sclerosis.
Progressive bulbar palsy (PBP) – This type of MND involves the brain stem. People with ALS often have PBP too. Patients frequently suffer from difficulty speaking, eating, choking spells and swallowing. With progression, limb weakness develops with both upper and lower motor neurone signs
Spinal muscular atrophy (SMA) – This is an inherited MND that affects children. It is caused by an abnormal gene known as SMA1 and there are three types. It tends to affect the legs, arms and trunk. Long-term outlook varies according to type. Type 1 has a poor prognosis and most children die by the age of 2 years.
Other types include post polio syndrome which follows polio virus infection and involves the lower motor neurons. Another type is Kennedy disease caused by a X-linked mutation that affects the androgen receptor. Symptoms include progressive muscle weakness and gynecomastia, erectile dysfunction and testicular atrophy due to involvement of the androgen receptor.
DIAGNOSIS AND INVESTIGATIONS IN MND
In the early stages, diagnosis may be difficult, because the features are similar to other conditions, such as Parkinson’s disease, multiple sclerosis (MS), or an inflamed nerve.
A complete and detailed history and neurological examination may point to motor neuron disease and further investigations are necessary to confirm the diagnosis
Blood and urine tests – Measurement of creatinine kinase may help detect conditions in which muscle breakdown occurs
MRI brain scan – Cannot diagnose MND, but it can help rule out other disorders, such as tumor, stroke, problems in brain circulation, or abnormal brain structure.
Electromyography (EMG) and nerve conduction study (NCS) - These are usually performed concurrently. An EMG detects the degree of electrical activity within muscles, while NCS tests the speed at which the nerve impulse moves through muscles.
Spinal tap, or lumbar puncture – A sample of CSF is obtained by introducing a needle in the spinal space and analyzed
Muscle biopsy - A muscle biopsy may be performed to rule out primary muscular disease rather than MND
The patient will be usually monitored for sometime following investigations before confirming the diagnosis of MND.
Diagnostic El Escorial criteria
The following clinical criteria may aid in the diagnosis of ALS. These include:
• Muscle atrophy, weakness or twitching
• Muscle stiffness or abnormal reflexes
• Progression of symptoms into new muscle groups
• Absence of other factors to explain the symptoms
TREATMENT OF MND
Currently there is no cure for MND, and treatments aim to slow down disease progression and improving the patient’s quality of life and independence
Slowing disease progression – Riluzole or Rilutek is approved and effective in early stages of ALS and in older patients and prolongs survival. They lower glutamate levels in the body. In 2017 another drug Radicava was also approved to treat MND
Muscle cramps and stiffness – Physical therapy, medications such as botulinum injections, and baclofen a muscle relaxant.
Drooling is treated by scopolamine patch worn behind the ear
Uncontrolled crying or laughter may be treated with antidepressants such as serotonin reuptake inhibitors (SSRIs)
Speech difficulties can be treated with the help of a speech therapist. Physical and occupational therapy help to improve movement and function and retain independence
Swallowing difficulties – Treated by a percutaneous endoscopic gastrostomy (PEG), in which a feeding tube that is placed on the abdomen by a simple surgical procedure
Pain – Painkillers such as NSAIDs can help with mild to moderate muscle stiffness and muscle spasms but opioids may become necessary for severe muscle and joint pain in later stages
Respiratory difficulties – When respiratory muscles become weak, mechanical ventilation where a machine pumps in filtered humidified air via a tracheostomy tube can help
Diet and supplements – A healthy diet and supplementation of necessary vitamins can improve the overall health of the patient
Stem cell transplant – Stem cell transplant and gene therapy research is underway and show promise
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