Individual Weak Muscles

What Causes Muscle Weakness?

Muscle weakness can have various causes, ranging in severity from 'troubling' to 'very serious'.  Finding the true cause means ruling out or confirming each possibility – in other words, diagnosis.

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Diagnosis is usually a complex process due to the sheer number of possible causes and related symptoms.  In order to diagnose muscle weakness, we could:

  • Research the topic
  • Find a doctor with the time
  • Use a diagnostic computer system.
The process is the same, whichever method is used.

Step 1: List all Possible Causes

We begin by identifying the disease conditions which have "muscle weakness" as a symptom.  Here are eight of many possibilities (more below):
  • Nephrotic Syndrome
  • Muscular Dystrophy
  • Polymyositis
  • Fluorosis
  • Vitamin B12 Need
  • Guillain-Barre Syndrome
  • Male Hypogonadism
  • Dermatomyositis

Step 2: Build a Symptom Checklist

We then identify all possible symptoms and risk factors of each possible cause, and check the ones that apply:
regular episodes of diarrhea
slightly impaired ability to walk
some muscle wasting
heaviness of the legs
severe cold weather muscle spasms
jaundiced skin
having had a small bowel resection
high sensitivity to bright light
having foamy urine
edema of the feet
reduced mental clarity
inability to tell hot from cold
... and more than 60 others

Step 3: Rule Out or Confirm each Possible Cause

A differential diagnosis of your symptoms and risk factors finds the likely cause of muscle weakness:
Cause Probability Status
Male Hypogonadism 98% Confirm
Fluorosis 24% Unlikely
Dermatomyositis 23% Unlikely
Nephrotic Syndrome 2% Ruled out
Vitamin B12 Need 1% Ruled out
Muscular Dystrophy 1% Ruled out
Guillain-Barre Syndrome 0% Ruled out
Polymyositis 0% Ruled out
* This is a simple example to illustrate the process

Arriving at a Correct Diagnosis

The Analyst™ is our online diagnosis tool that learns all about you through a straightforward process of multi-level questioning, providing diagnosis at the end.

If you indicate having muscle problems / disease, The Analyst™ will ask further questions including this one:
Do you have specific muscles that feel weak, or weaker than they should be?
Possible responses:
→ Don't know
→ No
→ One muscle is slightly weak
→ One muscle very weak / slight weakness in several
→ Serious weakness in several muscles
Based on your response to this question, which may indicate no individual weak muscles, specific muscle weakness or severe muscle weakness, The Analyst™ will consider possibilities such as:
Environmental Illness / MCS

The muscular weakness may be due to a nerve problem caused by chemical exposure and immune system changes associated with MCS.

Fluoride Toxicity

Early warning signs of fluorosis include loss of muscle power, weakness and pain.

Guillain-Barre Syndrome

GBS can cause muscles to weaken and atrophy.  Progressive weakening or paralysis may occur, typically beginning in the feet, hands or face.  The paralysis characteristically involves more than one limb, most commonly the legs.  The paralysis is progressive and usually ascending, spreading to the rest of the limb, and from there may spread to the legs, arms and the rest of the body.  The arms may feel weak, the patient no longer being able to lift heavy objects.

Magnesium Toxicity

Magnesium overload can depress the central nervous system, causing muscle weakness, lethargy, sleepiness, hyperexcitability, mental status changes, nausea, appetite loss, extremely low blood pressure, and irregular heartbeat.

Multiple Sclerosis

Gait disorders varying from an inability to walk the usual distance to an inability to walk at all are the principal problems of patients with MS.

Muscular Dystrophy

Dystrophin is a protein required for normal muscle function.  Muscular dystrophy leads to a lower concentration of dystrophin in certain muscles, thus causing weakness.

Myasthenia Gravis

Although Myasthenia Gravis (MG) can affect any of the voluntary muscles, certain muscle groups are more often affected than others.  More than half of patients experience eye symptoms; 1-in-7 have face and throat muscle symptoms; MG affects the arms more often than the legs.


Symptoms of neuritis include a weakness in the muscles and a wasting away of muscle tissue.  Without proper nerve stimulation the muscles are no longer healthy and cannot be effective.


Muscle weakness is the most common symptom of Polymyositis and Dermatomyositis (PM/DM), which are chronic inflammatory diseases of the muscle.

West Nile Virus

True muscle weakness in the presence of other related symptoms is suggestive of West Nile virus infection.

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