Sedentary Work Exerting up to 10 pounds (4.5 kg) of force occasionally and/or a negligible amount of force frequently or constantly to lift, carry, push, pull, or otherwise move objects, including the human body. Sedentary work involves sitting most of the time, but may involve walking or standing for brief periods of time. Jobs are sedentary if walking and standing are required only occasionally and other sedentary criteria are met.

Light Work Exerting up to 20 pounds (9.1 kg) of force occasionally and/or up to 10 pounds (4.5 kg) of force frequently, and/or negligible amount of force constantly to move objects. Physical demand requirements are in excess of those for Sedentary Work. Light Work usually requires walking or standing to a significant degree. However, if the use of the arm and/or leg controls requires exertion of forces greater than that for Sedentary Work and the worker sits most the time, the job is rated Light Work.

Medium Work Exerting up to 50 (22.7 kg) pounds of force occasionally, and/or up to 25 pounds (11.3 kg) of force frequently, and/or up to 10 pounds (4.5 kg) of forces constantly to move objects.

Heavy Work Exerting up to 100 pounds (45.4 kg) of force occasionally, and/or up to 50 pounds (22.7 kg) of force frequently, and/or in excess of 20 pounds (9.1 kg) of force constantly to move objects.

Very Heavy Work Exerting in excess of 100 pounds (45.4 kg) of force occasionally, and/or in excess of 50 pounds (22.7 kg) of force frequently, and/or in excess of 20 pounds (9.1 kg) of force constantly to move objects.

Job Classification

In most duration tables, five job classifications are displayed. These job classifications are based on the amount of physical effort required to perform the work. The classifications correspond to the Strength Factor classifications described in the United States Department of Labor's Dictionary of Occupational Titles. The following definitions are quoted directly from that publication.

Sedentary Work Exerting up to 10 pounds (4.5 kg) of force occasionally and/or a negligible amount of force frequently or constantly to lift, carry, push, pull, or otherwise move objects, including the human body. Sedentary work involves sitting most of the time, but may involve walking or standing for brief periods of time. Jobs are sedentary if walking and standing are required only occasionally and other sedentary criteria are met.

Light Work Exerting up to 20 pounds (9.1 kg) of force occasionally and/or up to 10 pounds (4.5 kg) of force frequently, and/or negligible amount of force constantly to move objects. Physical demand requirements are in excess of those for Sedentary Work. Light Work usually requires walking or standing to a significant degree. However, if the use of the arm and/or leg controls requires exertion of forces greater than that for Sedentary Work and the worker sits most the time, the job is rated Light Work.

Medium Work Exerting up to 50 (22.7 kg) pounds of force occasionally, and/or up to 25 pounds (11.3 kg) of force frequently, and/or up to 10 pounds (4.5 kg) of forces constantly to move objects.

Heavy Work Exerting up to 100 pounds (45.4 kg) of force occasionally, and/or up to 50 pounds (22.7 kg) of force frequently, and/or in excess of 20 pounds (9.1 kg) of force constantly to move objects.

Very Heavy Work Exerting in excess of 100 pounds (45.4 kg) of force occasionally, and/or in excess of 50 pounds (22.7 kg) of force frequently, and/or in excess of 20 pounds (9.1 kg) of force constantly to move objects.

Atrophy, Muscular (Progressive)


Related Terms

  • Bulbospinal Muscular Atrophy
  • Duchenne-Aran disease
  • Duchenne-Aran muscular atrophy
  • Familial Muscular Atrophy
  • Hereditary Muscular Atrophy
  • Motor Neuron Disease
  • Pure Progressive Muscular Atrophy

Differential Diagnosis

  • Amyotrophic lateral sclerosis (ALS or Lou Gehrig's disease)
  • Chronic inflammatory disease of the spinal cord and meninges
  • Intrinsic muscle disease
  • Primary lateral sclerosis
  • Progressive bulbar palsy
  • Progressive spinal muscular atrophy
  • Pseudobulbar palsy
  • Spinal cord compression by tumor

Specialists

  • Internal Medicine Physician
  • Neurologist
  • Occupational Therapist
  • Physical Therapist
  • Psychiatrist

Comorbid Conditions

Factors Influencing Duration

Length of disability may be influenced by the individual's general health and mental and emotional stability. The severity and progression of symptoms will ultimately determine how long the individual is able to continue working.

Medical Codes

ICD-9-CM:
335.21 - Muscular Atrophy, Progressive; Duchenne-Aran Muscular Atrophy

Overview

Progressive muscular atrophy is an inherited disorder affecting the nerves that control muscle activity in the body (motor neuron disease). Motor neurons are divided into upper motor neurons and lower motor neurons. Upper motor neurons originate in the motor region of the cerebral cortex or the brainstem and send motor information to the lower motor neurons found in the spinal cord (spinal lower motor neurons) and in the cranial nerve nuclei of the brainstem (cranial nerve lower motor neurons). In progressive muscular atrophy, only the lower motor neurons are involved.

This condition is a progressively debilitating disease. As the nerves deteriorate, the weakened muscles of the hands, arms, and legs waste (atrophy), stiffen, and may twitch involuntarily (fasciculate). Muscles controlling swallowing, chewing, coughing, breathing, and speech may be affected to varying degrees, but those controlling the bowels and bladder are usually spared.

The most common varieties of motor neuron disease are progressive bulbar palsy, pseudobulbar palsy, progressive spinal muscular atrophy, primary lateral sclerosis, spinal muscular atrophy, amyotrophic lateral sclerosis (ALS), and progressive muscular atrophy. It has been proposed that progressive muscular atrophy is a form of ALS.

Source: Medical Disability Advisor



Causation and Known Risk Factors

Onset of the disease is usually earlier than in other motor neuron diseases. Many cases, especially those with childhood onset, are associated with autosomal recessive inheritance; however, some cases are sporadic. Significantly more males than females are affected.

Source: Medical Disability Advisor



Diagnosis

History: As the spinal cord nerves degenerate, individuals typically present with muscle weakness and wasting (atrophy), initially in the hands and later in the arms, shoulders and legs. This may be accompanied by involuntary muscle twitching (fasciculation). In some forms of the disease, the face and tongue muscles are especially affected by twitching. Over time, the individual experiences increased difficulty speaking (dysarthria), swallowing (dysphagia), and breathing. Because awareness and intellect remain unchanged, this disease can be especially distressing for the individual and family. The disease frequently evolves into ALS.

Physical exam: The exam reveals progressive muscle weakness and wasting. Although individuals may have vague sensory complaints, the senses (hearing, sight, smell, taste, and touch) show no objective changes.

Tests: Diagnosis is aided by electromyography (EMG). Measurement of muscle electrical activity will show a peculiar pattern but must be interpreted with caution, together with the clinical features.. A muscle biopsy can also exclude myopathic conditions. Cerebrospinal fluid is usually normal. To rule out other diseases, additional testing may include blood studies, myelography (x-ray study of the spinal cord that has been injected with contrast dye), computed tomography (CT), or magnetic resonance imaging (MRI). Genetic testing is now also available to identify progressive muscular atrophy.

Source: Medical Disability Advisor



Treatment

At this time, there is no known effective treatment or means of slowing the nerve deterioration. Treatment, therefore, is designed to relieve specific symptoms and provide needed support. Anticholinergic drugs that decrease the amount of saliva produced by the salivary glands can be prescribed if drooling is troublesome. Benzodiazepine tranquilizers and muscle relaxants may decrease muscular spasticity. Narcotic analgesics are important in reducing the discomfort of muscle pain and cramps associated with motor neuron disease. Currently, the glutamate antagonist, riluzole, is the only approved treatment for motor neuron disease; however, it only increases life expectancy by about 2 months.

Physical therapy and occupational therapy maintain joint mobility, prevent shortening of muscle tissue (contractures), and maintain strength in those muscles that are still functioning. Braces and walkers can provide stability and improve mobility. Independence is maintained as long as possible by the use of wheelchairs, walkers, and other aids.

In later stages, feeding by means of a tube inserted either through the nose and into the stomach (nasogastric tube) or through a surgical opening directly into the stomach (gastrostomy) may be necessary because of choking and difficulty swallowing. An opening in the windpipe (tracheostomy) may be necessary if respiratory muscles are severely affected.

Source: Medical Disability Advisor



Prognosis

The progress of progressive muscular atrophy is especially devastating because individuals with the disease retain their mental powers (cognition) while their bodies gradually waste away. Individuals in the end stages may be totally paralyzed and unable to speak, move, or breathe on their own. Death generally occurs 3 to 6 years after the onset of the disease, usually as a result of pulmonary infections.

Source: Medical Disability Advisor



Rehabilitation

The goal of rehabilitation for progressive muscular atrophy is to maintain function and enhance mobility for as long as possible. In the early stage of the disease, physical therapy for active range of motion exercises can help maintain flexibility and strength and relieve the musculoskeletal pain associated with muscular weakness, paralysis, and immobility. During active range of motion exercises, the individual performs all the motion independently with or without resistance from an outside force. Resistance may be provided through use of an elastic band or light weights (isotonic exercise). In later stages, passive range of motion is preferable to avoid overexertion or possible damage to the muscles. In passive range of motion exercises, the therapist moves the involved limb without effort from the individual.

Because of muscle weakness in the legs, balance exercises are beneficial and include side stepping and walking with the eyes closed with and without assistance. Respiratory muscles can also become progressively weak as the disease advances, so exercises to strengthen muscles that assist in breathing become part of the program.

Learning how to avoid injury is another important intervention in the rehabilitation of progressive muscular atrophy. Occupational therapy helps individuals arrange their homes and organize their lives in ways that support their physical and mental well-being. Activities are also provided to relieve the mental boredom of inactivity. Devices and techniques that help the individual communicate are invaluable in maintaining peace of mind.

Counseling and support groups can help individuals and caregivers cope with the devastating physical aspects of the disease. The rehabilitation program varies between individuals with progressive muscular atrophy as the intensity and progression of the exercise depends on the stage of the disease and the individual's overall health.

Source: Medical Disability Advisor



Complications

Individuals with progressive muscular atrophy are susceptible to all the diseases and conditions common to other chronically ill, weakened individuals with impaired mobility. These conditions include vascular disease, stroke, blood clots, choking and aspiration, infectious disease, gastrointestinal disorders, diabetes, respiratory complications, and pressure sores. If surgical intervention is required for any of these conditions, the individual is subject to the usual surgical complications such as infection, adverse reaction to the anesthetic, pneumonia, or poor wound closure.

Source: Medical Disability Advisor



Ability to Work (Return to Work Considerations)

Because work is often therapeutic, the individual may strive to continue working as long as possible. Limited work activities may be possible, depending on the nature of the work and the individual's degree of muscular weakness. The individual's workspace may need to be changed to accommodate a wheelchair and provide a safe environment. Safety issues and accommodations revolve around the individual's weakness, physical instability, and tendency to choke.

Risk: As the disease progresses, affected individuals present an increasing safety risk to themselves and their coworkers, which may become inconsistent with employment. No job causes this condition.

Capacity: The amount of risk from working with progressive muscular atrophy is dependent on the extent of the individual's neuromuscular deterioration, loss of coordination and mobility, and swallowing and breathing ability. Capacity will become increasingly affected as the disease progresses; consequently, progressive work limitations will be necessary.

Tolerance: Tolerance factors include pain from muscle cramps and spasticity, the ability of the individual to manage his or her swallowing secretions, and the presence of dysarthria. Individuals with a significant amount of drooling and those with dysarthria may feel self-conscious about their appearance and may request job duties that require less public interaction. There is limited benefit from medication.

Source: Medical Disability Advisor



Maximum Medical Improvement

360 days.

Source: Medical Disability Advisor



Failure to Recover

If an individual fails to recover within the expected maximum duration period, the reader may wish to consider the following questions to better understand the specifics of an individual's medical case.

Regarding diagnosis:

  • Does individual have muscle weakness and wasting (atrophy) in the hand, arms, shoulders, and legs? Does any involuntary muscle twitching (fasciculation) occur?
  • Does individual have increased difficulty speaking, swallowing, and breathing? Was individual's awareness and intellect unchanged?
  • Does individual have vague sensory complaints? Are hearing, sight, smell, taste, and touch unchanged?
  • Was an EMG, muscle biopsy, blood tests, myelography, CT, or MRI done?
  • Were conditions with similar symptoms ruled out?

Regarding treatment:

  • Is individual receiving symptomatic treatment with support?
  • Were anticholinergic drugs prescribed? Muscle relaxants?
  • Is physical therapy involved in treatment?
  • Was a feeding tube necessary? Tracheostomy?
  • How long ago was the diagnosis made?

Regarding prognosis:

  • Can individual's employer accommodate any necessary restrictions?
  • Is individual active in rehabilitation? Does individual have a home exercise program?
  • Are individual and caregivers involved in support groups? Counseling?
  • Does individual have any conditions that may affect the disease process?
  • Are there any complications such as vascular disease, stroke, blood clots, choking and aspiration, infectious disease, gastrointestinal disorders, diabetes, respiratory complications, or pressure sores?

Source: Medical Disability Advisor



References

Cited

"Motor Neuron Diseases Fact Sheet." National Institute of Neurological Disorders and Stroke. 10 Dec. 2014. National Institutes of Health (NIH). 22 Apr. 2015 <http://www.ninds.nih.gov/disorders/motor_neuron_diseases/detail_motor_neuron_diseases.htm>.

Source: Medical Disability Advisor






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