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Amyotrophic lateral sclerosis

Amyotrophic Lateral Sclerosis: Lou Gehrig’s Disease

Amyotrophic Lateral Sclerosis: Lou Gehrig’s disease

Amyotrophic lateral sclerosis (ALS) – a devastating neuromuscular disease that strikes adults in the prime of life – has puzzled physicians since it was first described in medical literature more than 100 years ago. ALS was made famous by baseball legend Lou Gehrig – but anyone can get this disease. ALS is a fatal disorder that causes progressive muscle paralysis. ALS is a terminal neurological disorder that robs patients of their ability to dress themselves, eat, walk, and speak. Patients generally survive three to five years after being diagnosed, with death generally occurring due to respiratory failure. The cause of the deadly disease was and is still a mystery today.

Pathophysiology

The pathogenesis is unclear, but there are three general types of ALS: sporadic, familial and guamanian. (Neurology Channel, 2004) Sporadic is the most common in the United States with the cause believed to be excess levels of a neurotransmitter called glutamate. Glutamate in high levels acts as a neurotoxin that damages and kills nerve cells. Familial ALS (FALS) is linked to a genetic defect of chromosome 21. Mutated superoxide dismutase (SOD) causes motor neuron problems seen in ALS. (Brown, 2001) Guamanian ALS, first seen in Guam in the 1950’s and 1960’s, is suspected to be caused by the Cycad Cyas circinalis seed used to make flour, although not all researchers agree with this explanation. (Muscular Dystrophy Association, 2003) More recent research proposes a theory that bats, a delicacy of native Guamanians, who eat the nuts of the cycad tree, are cause of high rates of ALS in that country. If this holds true, then an environmental toxin in the diet may cause ALS and further investigation is needed. (Muscular Dystrophy Association Research, 2002)

Amyotrophic lateral sclerosis or Lou Gehrig’s disease is a progressive disease that attacks motor neurons, components of the nervous system that connect the brain with the skeletal muscles, or voluntary muscles. "The principle pathologic feature of ALS is lower and upper motor neuron degeneration, although without inflammation". (Boss, 1998) In less than two percent of patients ALS is caused by a mutation of the gene encoding the superoxide dismutase SOD1 that controls oxidative stress. Ninety-eight percent of ALS cases are of unknown causes. (Hum-molgen, 2001) The motor neurons affected by ALS are also known as anterior horn cells since they are located in the anterior, or front, of the spinal cord. The anterior horn cells are the nerves that send messages from the spinal cord to the muscles. The corticospinal tract is a series of structures that start in the brain and descend into the spinal cord to the anterior horn cells; it is part of the nervous system that sends messages regarding movement of the voluntary muscles. (Hole, 1981)

In ALS, the motor neurons deteriorate and eventually die causing the muscles to waste away from disuse. Weakness may begin in any or all muscles of the body with paresis usually beginning in a single muscle group. Corresponding muscle groups are asymmetrically affected in a mottled distribution. Gradual involvement occurs in all striated muscles except extraocular muscles and the heart. A person in the late stages of Lou Gehrig’s disease progresses to paralysis with no remissions. Even though a person’s brain is fully functional and alert, the command to move never reaches the muscles. (ALS & ALSA, 2004)

Diagnosis is "based on characteristic signs of progressive weakness, atrophy, fasiculations, and hyperreflexia affecting several regions of the body." (Walling, 1999) Diagnosis is made after repeated regular physical exams to document involvement of upper and lower motor neurons. The outward signs of ALS are progressive weakness and deterioration of the muscles (amytrophic) beginning in limbs, usually on one side of the body (lateral). Inside the body, the nerves controlling motor function die off after their cell bodies become hardened and shriveled (sclerosis) leaving the patient increasingly helpless.

Epidemiology & Etiology

There is an estimated 30,000 Americans with ALS. Since it is impossible to predict how long the disease has been active before being diagnosed, many patients last less than a year. However, life span can be five years after diagnosis and a small percentage survive ten years. Older persons and those with bulbar form tend to have a worse prognosis. About five to ten percent of ALS victims have an inherited disease, which strikes at a younger age and consecutive generations. Non-inherited ALS develops between 40 to 70 years of age and does not have racial, ethnic, or socioeconomic boundaries. (Mayo Clinic, 2004)

Etiology may be multifactorial or result from different neuronal insults. Several theories have been introduced over the years to try to explain ALS. The first is an abnormality of calcium and glutamate, which is essential to neurotransmission. Pathologic changes occur with cell metabolism damage with entry of the compounds in excessive amounts. Other causes are hypothesized to be from neurotoxicity of various metals, foods, or chemicals. (Walling, 1999) Approximately one third of neurons are destroyed before atrophy occurs. Patients do not know what is going on with their bodies other than the symptoms are progressively getting worse. The first symptoms are spastic gait and manual dexterity involvement. Functions not affected by ALS are extraoccular muscle movement, bladder and bowel control, sensory function and usually skin integrity. (Walling, 1999) As the disease progresses, the muscles that control swallowing, chewing, and breathing are affected. When the respiratory muscles weaken, some sort of mechanical breathing support may be needed. Respiratory problems are irreversible and once developed, a respirator is usually needed for the rest of the patient’s life.

Pharmacotherapeutic Options

There has been no treatment since the disorder was first identified more than 125 years ago until now. The first drug to slow the disease’s progression (riluzole or Rilutek) was approved by the Food and Drug Administration in 1995. Rilutek may slow progression for some patients and prolong life for a few months (Mayo Clinic, 2004) With no cure for ALS in sight; the primary care provider will try to control the manifestations of the disease. Anti-oxidants (vitamins E, C, and beta-carotene, nerve growth factor, gabapentin, myotrophin, and thyrotropin releasing hormone are being tested in therapeutic trials but reports are not encouraging. (Dambro, 2000)

Rilutek’s mode of action is unknown but properties that may be related to effects include: 1) an inhibitory effect on glutamate release, 2) inactivation of voltage-dependent sodium channels, and 3) the ability to interfere with intracellular events that follow transmitter binding at excitatory amino acid receptors. (The 2005 Physician’s Desk Reference Electronic Library) The drug is metabolized in the liver and excreted in the urine and feces. Precautions need to be utilized in patients with liver and/or renal insufficiency. There have been no clinical trials to evaluate drug interaction; however, if hepatotoxic drugs are being taken, caution must be used with Rilutek. Adverse reactions during trials included nausea, dizziness, decreased lung function, diarrhea, abdominal pain, pneumonia, vomiting, vertigo, circumoral parathesis, anorexia, and somnolence. Nausea, dizziness, anorexia, vertigo, somnolence, and circumoral paresthesia are dose related. (The 2005 Physician’s Desk Reference Electronic Library) These adverse reactions were similar between genders and were independent of age. Recommended dose is 50 mg every 12 hours taken one hour before or two hours after a meal.

Symptomatic treatment for ALS depends on the individual and possible benefits of treatment. There are three drugs used to relieved spasticity: baclofen (Lioresal) 10 to 25 mg three times a day, diazepam (Valium) 2 to 15 mg three times a day, or dantrolene (Dantrium) titrated dose 50 to 100 mg four times a day. Adverse effects of these drugs are increased weakness, sedation, and dizziness. (Walling, 1999)

Painful muscle cramps can be treated with nonsteroidal anti-inflammatory agents and anticonvulsive medications including carbamazepine (Tegretol) dose up to 200 mg three times a day, or phenytoin (Dilantin) 300 mg at bedtime. In early ALS, amitriptyline (Elavil) 50 to 100 mg at bedtime or nortriptyline (Pamelor) 50 to 75 mg at bedtime helps to potentiate analgesic medications. (Walling, 1999)

One of the most distressing symptoms for ALS patients with bulbar type is drooling which can cause bronchospasm. Anticholinergic drugs like Atropine 0.4 mg four times a day or scopolamine (Transderm-Scop) 0.5 mg patch every third day application help to suppress sialorrhea. (Walling, 1999)

There are several tricyclic antidepressants requiring a balancing of effects and adverse effects that are used in the treatment of ALS. Amitriptyline (Elavil), doxepin (Sinequan), and imipramine (Tofranil) have similar effects in providing antidepressant and antisialorrheic actions and provide nocturnal sedation, help potentiate analgesia and possible weight gain. These agents have the potential to produce hypotensive, cardiac, sedative, and anticholinergic side effects. (Walling, 1999)

Individualized therapy is required for the depression and anxiety common to all ALS patients. Fluoxetine (Prozac), a selective serotonin reuptake inhibitor, 20 mg once or twice daily is effective but can cause agitation and insomnia. Anxiety and insomnia may be relieved by benzodiazepines but daytime sedation may be caused. (Walling, 1999)

Conclusion

Each patient and family is unique while experiencing ALS. Various health professionals are utilized to deal with the "adjustment, mental health, disability, and financial" concerns required with this disabling disease. (Walling, 1999) Families require access to the latest information. Written instructions need to be assessed and available regarding respiratory failure and end-of-life decisions. Prior to respiratory failure, if a decision is made to not use a ventilator, the provider needs to be aware of this decision and a Do Not Resuscitate (DNR)

Bibliography:

ALSA: ALS and ALSA (2004). Understanding ALS: Facts about ALS. Retrieved January 23, 2005, from http://www.alsa.org/als/facts.cfm

Boss, B. (1998). Alterations of neurologic function. In K.L. McCance & S.E. Huether (Eds.), Pathophysiology: The biologic basis for disease in adults and children (pp. 562-563). St. Louis: Mosby.

Brown, R., Jr. (2001). Amyotrophic lateral sclerosis and other motor neuron diseases. In E. Braunwald, A.S. Fauci, D.L. Kasper, S.L. Hauser, D.L. Longo, & J.L. Jameson (Eds.), Harrison’s principles of internal medicine (pp. 2412-2415). New York: McGraw-Hill.

Dambro, M. (Ed.). (2000). Amyotrophic lateral sclerosis. In Griffith’s 5-minute clinical consult. (Pp. 36-37). Philadelphia: Lipincott, Williams, & Wilkins.

Hole, J. Jr. (Ed.). (1981). The nervous system. In Human Anatomy and Physiology (2nd ed. pp. 290-294). Dubuque, IA: Wm C. Brown Company Publishers.

HUM-MOLGEN bulletin board. (June 1, 2001). Motor neuron survival and Lou Gehrig’s disease. Retrieved January 23, 2005, from

http://hum-molgen.org/NewsGen/06-2001/msg01.html

Mayo Clinic (December 3, 2004). What is ALS? Retrieved January 24, 2005, from http://www.mayoclinic.com/invoke.cfm?id=DS00359

MDA Research (2002). Guamanian ALS: A tough nut finally cracked? Retrieved January 20, 2005, from http://www.mdausa.org/research/020401batsALS.html

Muscular Dystrophy Association (2003). Facts about amyotrophic lateral sclerosis (ALS). Retrieved January 19, 2005, from http://www.mdausa.org/publications/fa-als.html

Neurology Channel (2004). Amyotrophic Lateral Sclerosis. Retrieved January 22, 2005, from http://www.neurologychannel.com/als/

The 2005 Physician’s Desk Reference Electronic Library. (2005), Medical Economics Company, Inc. Retrieved from CD-ROM database (CD-ROM, 2005 release)

Walling, A. D. (1999). Amyotrophic lateral sclerosis: Lou Gehrig’s disease. American Family Physician. March 15, 1999. Retrieved January 21, 2005, from http://www.aafp.org/afp/990315ap/1489.html



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