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Lou Gehrig’s Disease (Amyotrophic lateral sclerosis – ALS)

Lou Gehrig’s Disease Definition

Lou Gehrig’s disease, also known as Amyotrophic lateral sclerosis (ALS), is a motor neuron disease resulting due to upper and lower motor neuron degeneration, which are located in the ventral horn of spinal cord and cortical neurons, which provide their efferent input. This disease got its name from the New York Yankees baseball player, being diagnosed as Lou Gehrig’s disease in the year 1939.

The synonym Amyotrophic lateral sclerosis is derived from the Greek language (A means- no or absent, myo- muscle, trophic- nourishment, lateral- areas of spinal cord, where nerve cells signaling and controlling the muscle are located, sclerosis- scarring). Thus, when the muscle does not have nourishment, it wastes or atrophies. Since, only the motor neurons are affected, sensory system and the eye and bladder muscles are spared.

Lou Gehrig’s Disease Epidemiology

Lou Gehrig’s disease is one among the most common neuromuscular disease, and people of every race and ethnic background are affected. Two in 1,00,000 individuals suffer from Lou Gehrig’s disease each year. Men are affected than the women. The age group most commonly affected is 40-60 years. Heredity cause contributes to about 5-10 %, and is called as familiar Lou Gehrig’s disease; whereas, 90% of the cases are sporadic. In families with Lou Gehrig’s disease, 50% of the total offspring suffer from this disease.

Lou Gehrig’s Disease Symptoms

  • Muscle weakness of arms and legs
  • Abnormal fatigue in the arms and legs
  • Foot drop
  • Difficulty in walking (clumsy walk)
  • Difficulty in activities of daily living
  • Muscle cramps and twitches in arm, shoulders and tongue
  • Tripping and dropping things
  • Dysphagia (swallowing difficulty) – Choking easily, Drooling and Gagging
  • Head drop due to weakness of the neck muscles
  • Fasciculation (involuntary muscle contractions)
  • Dysarthria (speech difficulty/slurring)
  • Dyspnea (breathing difficulty)
  • Voice hoarseness
  • Weight loss
  • Involuntary laughter and crying

Lou Gehrig’s Disease  Causes

Genetic mutation

This result in inherited Lou Gehrig’s disease


Atrophy and death of neurons

Hence, they do not send message to the muscles, resulting in twitching, weakening and an inability to move the arms, legs, and body.

Chemical imbalance

Increase in the glutamate level, which is a chemical messenger in the brain, acts as toxic to certain nerve cells.

Protein mishandling

Accumulation of abnormal forms of proteins within the nerve cells or neurons causes nerve cell necrosis.

Disorganized immune response

Attacking body’s own normal cells may trigger Lou Gehrig’s disease.

Lou Gehrig’s Disease Risk factors

  • Heredity
  • Age (40-60 yrs)
  • Males are more susceptible (both genders are equally affected after 70 years)
  • Environmental factors:
  1. Smoking – It increases the risk to about twice than non-smokers
  2. Lead exposure – Exposure to lead in the workplace may be associated with the development of Lou Gehrig’s disease
  3. Military service – Exposure to certain chemicals, metals, viral infections, traumatic injuries and intense exertion may be the causative factors triggering the disease.

Lou Gehrig’s Disease – Pathophysiology

Lou Gehrig’s disease is a neurodegenerative disease affecting the nerve cells of the brain and spinal cord. Since, the motor neurons reach from the brain to the spinal cord and from there, to the muscles of the body, the progressive motor neuron degeneration occurring in Lou Gehrig’s disease leads to death. The astrocytic gliosis replaces the lost neurons. The disappearance of cortical motor cells leads to retrograde axonal loss and gliosis in the pyramidal or corticospinal tract. The so formed gliosis results in bilateral white matter changes in the brain that is visible with a MRI.

As a result, the spinal cord atrophies, thereby losing the large myelinated fibers in the motor nerves. The affected muscles atrophy and the frontal or temporal cortical neurons are lost, as in frontotemporal dementia. Hence, when motor neurons die, brain’s ability in initiating and controlling the movement of muscle is completely lost.

Thus, when the voluntary muscle action is progressively affected, in the later stage, the patient may be totally paralyzed. As the motor neurons keep on degenerating, they lose their capability to send impulses to the muscles, which normally causes the muscle movement.

Lou Gehrig’s Disease – Diagnosis

Even though no definitive diagnostic biomarker or diagnostic tests exists for Lou Gehrig’s disease, depending on the clinical features, the following tests are performed to rule out other causes.

1. El Escorial criteria

These are standardized widely accepted criteria considered for the diagnosis of Lou Gehrig’s disease for clinical practice, therapeutic trials and other research purposes. It was established in 1994. To be diagnosed as Lou Gehrig’s disease,

It requires the presence of:-

LMN signs by clinical, electrophysiological or neuropathological examination
UMN signs by clinical examination
Progression of disease within a region and other regions by clinical examination or via medical history

It requires the absence of:-

Electrophysiological and pathological evidence of other diseases that may explain the UMN and LMN signs.
Neuroimaging evidence of other disease processes that may explain the observed clinical and electrophysiological signs

2. Genetic testing

To diagnose familial Lou Gehrig’s disease

3. Electromyography

Examines the nerve currents to see which nerve is not functioning

Nerve conduction velocity studies

Nerve and muscle biopsies

Cervical spine CT or MRI

To rule out any cervical disease mimicking the Lou Gehrig’s symptoms (to evaluate the existence of any structural, infective or spinal fluid cause)

Blood and urine test

To detect thyroid and parathyroid hormone levels to rule out thyroid diseases and urine test to detect the presence of heavy metals

Lumbar puncture (spinal tap):

Here, the physician inserts a needle into the lower back for withdrawing a sample of spinal fluid for examining the cerebrospinal fluid.

Differential diagnosis

  • Brainstem Gliomas
  • Chronic Inflammatory Demyelinating Polyradiculoneuropathy
  • Central Cord Syndrome
  • Dermatomyositis/Polymyositis
  • Lyme Disease
  • Lambert-Eaton Myasthenic Syndrome (Myasthenia Gravis)
  • Posttraumatic Syringomyelia
  • Multiple Sclerosis
  • Spinal Muscular Atrophy
  • Primary Lateral Sclerosis
  • Sarcoidosis and Neuropathy

Lou Gehrig’s Disease Prognosis

Better prognosis is achievable with:-

  • Age at the time of onset maintains a strongest relationship to Lou Gehrig’s disease. Research has proven that 35-40 years of me of age at the time of onset had better 5 year survival rates compared to older individuals. Individuals with limb onset disease ALS has better prognosis than bulbar onset.
  • Less severe involvement at the time of onset
  • Longer interval between onset and diagnosis
  • No dyspnea at the time of onset

Lou Gehrig’s Disease Complications

  • Aspiration
  • Loss of self-care ability
  • Pneumonia
  • Lung failure
  • Pressure sores
  • Weight loss

Lou Gehrig’s Disease Treatment

Even though, there is no cure for Lou Gehrig’s disease, the treatment modalities cannot reverse or stop the disease condition; instead, it prolongs the life span. It ultimate treatment goal is to control the symptoms.

Medical management

Glutamate antagonist

Riluzole is a benzothiazole agent gets absorbed with 60 % average oral bioavailability and 12 hours of mean elimination half-life. With multiple dose administration, steady state is supposed to reach in 5 days’ time. As a result, few minor and six major metabolites are being produced after metabolism takes place in the liver.

Even though, Riluzole’s exact mechanism is not known, it counteracts with the glutaminergic (excitatory amino acid) pathways. Hence, this drug prolongs the median tracheostomy-free survival rate by 2-3 months, if the patient is less than 75 years.

Skeletal muscle relaxants

Muscle relaxants decrease muscle spasm and spasticity in patients having limb weakness.

  • Baclofen (Lioresal, Gablofen) – After getting metabolized in the liver, baclofen is primarily excreted in urine.
  • Tizanidine (Zanaflex) – It is a centrally acting skeletal muscle relaxant that metabolizes in the liver and excretes in urine and feces. It is used to reduce the spasticity in the limbs.

Mucolytics

Mucolytics like guaifenesin is used for treatment of making the thickened accumulated secretions thin. It is recommended to make the room air adequately humid and hydrated. In certain cases, mechanical suction may be necessary.

Antidepressants

Serotonin reuptake inhibitors like citalopram 10-40 mg/d are used in the treatment of depression.

Sedatives/anxiolytic

Lorazepam 0.5-1.0 mg is the commonly used drug that acts as sedative/hypnotic, anxiolytic, amnesic, muscle relaxanant and antiemetic; but, should be used with extreme caution as it may cause respiratory depression.

Analgesics

Tramadol, ketorolac, morphine (immediate or extended release) or fentanyl patch may be utilized. A chance of respiratory depression is noted with opiates.

Anticholinergic agents

Oral atropine or amitriptyline, glycopyrrolate and hyoscine may control the swallowing difficulty that causes choking and drooling as well. Side effects include glaucoma exacerbation and confusion.

Botulinum toxin

It is used for paralyzing the parotid glands that influences the saliva secretion to increase, resulting in drooling.

Antiarrhythmic agent

A combination of quinidine (Nuedexta) dextromethorphan has proven to be efficient in reducing the involuntary laughing and crying, which is the pseudobulbar affect.

Respiratory Symptoms

Respiratory muscle weakness caused decrement in ventilation and increases the risk of dypnea, sleep apnea and aspiration. Noninvasive ventilatory support improves the quality of life and life expectancy of a patient during the early ventilatory failure. This is the most effective treatment to prolong the life span compared to others. Polysomnography identifies any disruption in the sleep contiguity resulting due to ventilatory failure, which is caused by nosturnal oxygen desaturation, apneas and hypopneas.

On the contrary, invasive ventilatory support that requires tracheostomy is chosen in patients having respiratory failure, but neurologically intact. Another suitable candidate is those whose secretions are unmanageable, and needs to be kept alive for a long term, which is otherwise, not possible in noninvasive ventilatory support.

Bulbar Weakness

Being one among the distressing features of Lou Gehrig’s disease, it causes weakness of pharynx, tongue and facial muscles, and loss of salivary control as well. Consequently, the patient may have swallowing difficulty, and may start to choke and drool. Hence, the excess saliva should be controlled. Anticholinergic agents may decrease these symptoms; whereas, parotid glands may be paralyzed using botulinum toxin.

Psychological Symptoms

Psychological symptoms like depression and suicidal thoughts emerge due to decline in muscle strength, along with at least five other symptoms like loss of interest, fatigue, insomnia, weight loss, diminished concentration, etc., for a period of 2 weeks. Beck Depression Inventory is the screening tool used for assessing the depression level. Psychopharmacology, Counseling, and social support may prove to reduce major depression in 80% to 90% of patients.

Dietary Considerations in swallowing difficulty

As the disease progresses, appetite declines, and the swallowing may become difficult. In compensation to this loss, a nutritionist, dietician and speech therapist should be consulted. It is recommended to take dietary supplements to get adequate calorie intake. Hence, in patients with low calorie intake and swallowing difficulty, feeding gastrostomy is placed. If PEG or percutaneous endoscopic gastrostomy needs to be placed, gastroenterologist should be consulted.

Activity Restriction

Even though, initially, no activity restriction is needed, take should be taken not to overexert to the fatigue or pain threshold. Regular mild exercises can be performed, if the condition permits; endurance exercises should be avoided, as it can increase the level of fatigue. The primary goals of being active are to prevent painful contractures, maintain normal joint range of motion and maintain the strength and tone of the muscles not or minimally affected. Assistive devices should be used to prevent the risk of falling.

Physical therapy Management

  • Active or passive range of motion exercises
  • Chest physical therapy
  • Mobility and transfer
  • Two hour turning regime to prevent pressure sores
  • Assistive devices

Lou Gehrig’s Disease – Prevention

Genetic counseling is recommended if a significant family history of Lou Gehrig’s disease is present to minimize the risk of gene transmission to the next generation.

Avoidance of smoking, which is a risk factor for this disease.

Even though the treatment techniques mentioned above are standardized, it is still recommended to consult your physician prior to adopting any self-treatments.

References

Physical rehabilitation, 5th Ed, Susan Sullivan & Thomas Schmitz

http://en.wikipedia.org/wiki/Amyotrophic_lateral_sclerosis

http://www.alsa.org/about-als/what-is-als.html

http://www.webmd.com/brain/news/20110822/common-cause-of-lou-gehrigs-disease-found

http://www.mayoclinic.com/health/amyotrophic-lateral-sclerosis/DS00359

http://www.healthscout.com/ency/68/53/main.html

http://health.nytimes.com/health/guides/disease/amyotrophic-lateral-sclerosis/overview.html

http://www.nursingcenter.com/prodev/ce_article.asp?tid=756417

http://emedicine.medscape.com/article/1170097-overview

http://www.news-medical.net/?tag=/lou+gehrig%27s+disease

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