Weakness is one of the most common reasons patients present to primary care clinicians. Weakness is loss of muscle strength, although many patients also use the term when they feel generally fatigued or have functional limitations even though muscle strength is normal.

Weakness may affect a few or many muscles and develop suddenly or gradually. Other symptoms may be present depending on the cause. Weakness of specific muscle groups can cause disorders of eye movement, dysarthria, dysphagia, or respiratory weakness.


Many causes of muscle weakness are categorized by location of the lesion (see table Some Causes of Muscle Weakness). Usually, lesions in a given location manifest with similar clinical findings. However, some disorders have characteristics of lesions in more than one location.

Common causes of focal weakness include.

  • Stroke - the most common cause of unilateral weakness.
  • Neuropathies - including those that are caused by trauma or entrapment immune-mediated (eg, Bell palsy)
  • Spinal root entrapment (eg, herniated intervertebral disk)
  • Spinal cord compression (eg, cervical spondylosis, epidural cancer metastasis, trauma)
  • Multiple sclerosis
  • Temporary focal weakness may occur as part of postictal (Todd) paralysis, which usually resolves over several hours, or result from a transient ischemic attack hypoglycemia

The most common causes of generalized weakness are

  • Deconditioning due to inactivity (disuse atrophy) resulting from illness or frailty, especially in older patients
  • Generalized muscle wasting due to prolonged immobilization in an intensive care unit (ICU)—a condition called ICU myopathy
  • Critical illness polyneuropathy (ICU neuropathy)
  • Common myopathies (eg, alcoholic myopathy, hypokalemia, corticosteroid myopathy)


  • Fatigue - Common causes of fatigue include acute severe illness
  • Cancers
  • chronic infections (eg, HIV infection, hepatitis, endocarditis, mononucleosis), endocrine disorders, renal failure, hepatic failure, heart failure, and anemia. Multiple sclerosis can cause daily fatigue that increases with exposure to heat and humidity.
  • Addison's Disease
  • chronic fatigue
  • weight loss
  • loss of appetite
  • stomach pain
  • Anemia
  • Chronic Fatigue Syndrome
  • Diabetes
  • Fibromyalgia



A complete neurologic and muscle examination is done to identify localizing or diagnostic findings. Key findings usually involve

  • Cranial nerves
  • Motor function
  • Coordination
  • Gait
  • Sensation
  • Reflexes

 Cranial nerve examination 

 Motor examination 

Strength testing 

 0: No visible muscle contraction

  • 1: Visible muscle contraction with no limb movement
  • 2: Limb movement but not against gravity
  • 3: Movement against gravity but not resistance
  • 4: Weakness against resistance
  • 5: Full strength

Coordination testing .

Gait is observed for the following:

  • Ignition failure (temporary freezing in place when starting to walk, followed by festination): Parkinson disease
  • Apraxia, as when feet stick to the floor: Normal-pressure hydrocephalus or other frontal lobe disorders
  • Festination: Parkinson disease
  • Limb asymmetry, as when patients drag a leg, have reduced arm swing, or both: Hemispheric stroke
  • Ataxia: Midline cerebellar disease
  • Instability during turns: Parkinsonism


Reflexes are tested.

The classic Babinski reflex (the great toe extends and the other toes fan apart) is highly specific for a corticospinal tract lesion.

  • A normal jaw jerk and hyperreflexic arms and legs suggest a cervical lesion affecting the corticospinal tract, usually cervical stenosis.
  • Anal tone, anal wink reflex, or both are reduced or absent in spinal cord injury but are preserved in ascending paralysis due to Guillain-Barré syndrome.
  • Abdominal reflexes are absent below the level of spinal cord injury.
  • A cremasteric reflex can test the integrity of the upper lumbar cord and roots in males.


  • Signs of respiratory distress (eg, tachypnea, weak inspiration) are noted. The skin is examined for jaundice, pallor, rash, and striae.
  • The neck, axillae, and inguinal area should be palpated for adenopathy; any thyromegaly is noted.
  • Heart and lungs are auscultated for crackles, wheezes, prolonged expiration, murmurs, and gallops.
  • abdomen is palpated for masses, including, if spinal cord dysfunction is possible, a grossly enlarged bladder.
  • Joint range of motion is assessed.
  • If tick paralysis is suspected, the skin, particularly the scalp, should be thoroughly inspected for ticks.


1. Picric Acid – great weakness in the legs along with a feeling of heaviness. The legs feel weak from a short walk and feel heavy all the time. There may be trembling in the legs, numbness, crawling, and a pricking sensation. The person may feel tired by the least amount of exertion. Both mental and physical weakness may be present.

2. Causticum – muscle weakness in the arms. There is a progressive loss of muscular strength in the arms, which feel weak and lame. Weakness in arms usually is seen to get worse in the night time. A tearing, dull pain in the arms may be present. Causticum is also indicated for muscle weakness in the hands and fingers. There appears fullness in hands when the person tries to grasp anything. Fingers may also feel icy cold. The person needing Causticum may have a high sensitivity towards cold air. Apart from muscle weakness, Causticum is a top ranking medicine for paralysis (loss of muscle function).

3. Gelsemium Sempervirens – Muscle weakness attended with deep-seated muscle pains is indicative of its use. The person needing this medicine has weakness in the arm and leg muscles. The muscles lose their power to contract effectively. Arms feel powerless and numb. Trembling of hands and legs (that feel fatigued and tired from little exercise) are other symptoms. There appears difficulty in walking, with an unsteady gait from a weakness of the leg muscles. Drawing, contractive, cramping, and deep-seated muscular pains in the legs are also present. The calf muscles feel bruised, and there is a numbness in the limbs. General fatigue and weakness are also well-noted along with these symptoms.

5. Kali Phos – There is muscle weakness with lameness throughout the body. The limbs feel weak and tired, and there is debility and weakness. Use of Kali Phos is also considered in cases of muscle weakness present in chronic fatigue syndrome.

6. Arsenic Album – The entire body feels weary, with an aversion towards any effort. Limbs feel excessively weak and exhausted. Exhaustion confines the person to the bed. Other symptoms include sleeplessness, anxiety, and restlessness. The person may experience debility and exhaustion from the slightest amount of over-work.

7. Stannum Met – muscle weakness in limbs attended with heaviness. There appears to be a loss of power in the limbs. Arms feel weak and heavy. Motion worsens it. Weakness and fatigue of arms arise from lifting a small weight, or from the slightest exercise. The person may be unable to hold an object due to weakness. There may be twitching of muscles of the forearm and hand. The thighs also feel weak and heavy. Walking worsens it, making the person want to sit down. Excessive weariness and fatigue with a desire to lie down may be present.

8. Conium Maculatum - muscle weakness in the legs attended with their trembling. Loss of muscle power in legs and extreme weakness from walking short distance is present. The person is unable to walk and has a staggering gait. Shooting pain in the legs may arise. Legs feel heavy and weary. Knees also feel weak. Conium Maculatum is also an indicated medicine for paralytic weakness in lower limbs that ascends upwards.

9. Plumbum Met – progresses rapidly. marked debility, weakness, and lameness of the arms. Muscles of the arm lack the power to move. Muscle weakness is severe and progressive. Cramping in the calf muscles may also be present. Plumbum Met is also a prominently indicated medicine for paralysis of limbs along with atrophy (wasting) of the muscles.