Weakness - Types, Causes, Symptoms, Diagnosis, Treatment

Weakness or asthenia is a symptom of a number of different conditions. The causes are many and can be divided into conditions that have true or perceived muscle weakness. True muscle weakness is a primary symptom of a variety of skeletal muscle diseases, including muscular dystrophy and inflammatory myopathy. It occurs in neuromuscular junction disorders, such as myasthenia gravis.

Spinal Cord Anatomy

Dorsal Column – Medial Lemniscus (fine touch, proprioception)

Afferent sensory fibers with a cell body in DRG
Ascend in ipsilateral posterior column
Synapse in the medulla, decussate, ascend in the contralateral medial lemniscus
Synapse in the thalamus (VPL)
Synapse in a sensory strip of the post-central gyrus

Spinothalamic Tract (pain, temperature)

Afferent sensory fibers with a cell body in DRG
Ascends 1-2 levels
Synapse in the ipsilateral spinal cord, decussate, ascend in the contralateral lateral spinothalamic tract
Synapse in the thalamus (VPL)
Synapse in a sensory strip of the post-central gyrus

Lateral Corticospinal Tract (motor)

Efferent cell body in a motor strip of pre-central gyrus
Descends through the internal capsule
Decussates in the pyramid of the medulla descend in the contralateral lateral corticospinal tract
Synapse in the anterior horn, lower motor neuron to muscle fiber

Types

Muscle fatigue can be central, neuromuscular, or peripheral muscular. Central muscle fatigue manifests as an overall sense of energy deprivation, and peripheral muscle weakness manifests as a local, muscle-specific inability to do work. Neuromuscular fatigue can be either central or peripheral.

Central weakness

Central fatigue is generally described in terms of a reduction in the neural drive or nerve-based motor command to working muscles that results in a decline in the force output. It has been suggested that the reduced neural drive during exercise may be a protective mechanism to prevent organ failure if the work was continued at the same intensity. The exact mechanisms of central fatigue are unknown, though there has been a great deal of interest in the role of serotonergic pathways.

Neuromuscular weakness

Nerves control the contraction of muscles by determining the number, sequence, and force of muscular contraction. When a nerve experiences synaptic fatigue it becomes unable to stimulate the muscle that it innervates. Most movements require a force far below what a muscle could potentially generate, and barring pathology, neuromuscular fatigue is seldom an issue

Peripheral muscle weakness

Peripheral muscle fatigue during physical work is considered an inability of the body to supply sufficient energy or other metabolites to the contracting muscles to meet the increased energy demand. This is the most common cause of physical fatigue—affecting a national average of 72% of adults in the workforce in 2002. This causes contractile dysfunction that manifests in the eventual reduction or lack of ability of a single muscle or local group of muscles to do work.

Causes

Weakness may be all over the body or in only one area. Weakness is more noticeable when it is in one area. Weakness in one area may occur:

After a stroke
After an injury to a nerve
During a flare-up of multiple sclerosis (MS)

Weakness may be caused by diseases or conditions affecting many different body systems, such as the following:

METABOLIC

Adrenal glands not producing enough hormones (Addison disease)
Parathyroid glands produce too much parathyroid hormone (hyperparathyroidism)
Low sodium or potassium
Overactive thyroid (thyrotoxicosis)

BRAIN/NERVOUS SYSTEM (NEUROLOGIC)

Disease of the nerve cells in the brain and spinal cord (amyotrophic lateral sclerosis; ALS)
Weakness of the muscles of the face (Bell palsy)
Group of disorders involving brain and nervous system functions (cerebral palsy)
Nerve inflammation causing muscle weakness (Guillain-Barre syndrome)
Multiple sclerosis
A pinched nerve (for example, caused by a slipped disk in the spine)
Stroke

MUSCLE DISEASES

Becker muscular dystrophy
Dermatomyositis
Muscular dystrophy (Duchenne)
Myotonic dystrophy

POISONING

Botulism
Poisoning (insecticides, nerve gas)
Shellfish poisoning

OTHERS

Not enough healthy red blood cells (anemia)
Disorder of the muscles and nerves that control them (myasthenia gravis)
Polio
Electrolyte Imbalances
Malignant Tumors
Malnutrition
Muscle Disease Medications
Muscular Dystrophy
Myotonic Dystrophy
Nerve Impingement
Poisoning (Organophosphates)
Poliomyelitis
Thyrotoxicosis
Trauma

LESION	CRITICAL	EMERGENT
Non-neurological	Shock (VS, clinical assessment) Hypoglycemia (POC glucose) Electrolyte derangement (BMP) Anemia (POC Hb, CBC) MI (ECG, troponin) CNS depression (Utox, EtOH)
Cortex	Stroke	Tumor Abscess Demyelination
Brainstem	Stroke	Demyelination
Spinal Cord	Ischemia Compression (disk, abscess, hematoma)	Demyelination (transverse myelitis)
Peripheral	Acute demyelination (GBS)	Compressive plexopathy
Muscle	Rhabdomyolysis	Inflammatory myositis

Symptoms

Slow or delayed movement in performing specific tasks.
Muscle cramps
Episodes of tremors or shaking while doing any task.
Muscle twitching.
Fever may be a common sign of asthenia affecting the whole body.
Tiredness, loss, or reduced energy is a common sign and symptom of asthenia.
Physical discomfort, loss, or absence of muscle strength is also a symptom of asthenia.
Inability to finish a task or a movement.
Change in mental state or sometimes confusion.
Sudden change or reduced vision
Sudden loss of consciousness
Difficulty in speech, difficulty swallowing, etc.

Weakness over all syndromes

Unilateral weakness, ipsilateral face
Lesion: Contralateral cortex, internal capsule Causes: Stroke (sudden onset), demyelination/mass (gradual onset) Symptoms: Neglect, visual field cut, aphasia Findings: UMN signs Key features: Association with headache suggests hemorrhage or mass
Unilateral weakness, contralateral face
Lesion: Brainstem Causes: Vertebrobasilar insufficiency, demyelination Symptoms: Dysphagia, dysarthria, diplopia, vertigo, nausea/vomiting Findings: CN involvement, cerebellar abnormalities
Unilateral weakness, no facial involvement
Lesion: Contralateral medial cerebral cortex, discrete internal capsule Causes: Stroke Rare Cause: Brown-Sequard if contralateral hemibody pain and temperature sensory disturbance
Unilateral weakness in single limb (mono paresis/plegia)
Lesion: Spinal cord, peripheral nerve, NMJ UMN signs: Brown-Sequard if contralateral pain and temperature sensory disturbance LMN signs: Radiculopathy if associated sensory disturbance Normal reflexes, normal sensation: Consider NMJ disorder
Bilateral weakness of lower extremities (paraparesis/plegia)
Lesion: Spinal cord, peripheral nerve UMN signs: Anterior cord syndrome (compression, ischemia, demyelination) if contralateral pain and temperature sensory disturbance Cauda equina: Loss of perianal sensation, loss of rectal tone, or urinary retention GBS: If no signs of cauda equina and sensory disturbances paralleling ascending weakness (with hyporeflexia)
Bilateral weakness of upper extremities
Lesion: Central cord syndrome Causes: Syringomyelia, hyperextension injury Findings: Pain and temperature sensory disturbances in upper extremities (intact proprioception)
Bilateral weakness of all four extremities (quadriparesis/plegia)
Lesion: Cervical spinal cord Findings: UMN signs below the level of injury, strength/sensory testing identifies the level
Bilateral weakness, proximal groups
Lesion: Muscle Causes: Rhabdomyolysis, polymyositis, dermatomyositis, myopathies Findings: Muscle tenderness to palpation, no UMN signs, no sensory disturbances
Facial weakness, upper and lower face
Lesion: CN VII Causes: Bell’s palsy, mastoiditis, parotitis Other CN involvement suggests brainstem lesions, multiple cranial neuropathies, or NMJ.

Diagnosis

Another testing is done based on where doctors think the problem is:

A brain disorder: Magnetic resonance imaging (MRI) or, if MRI is not possible, computed tomography (CT.
A spinal cord disorder: MRI or, when MRI is not possible, CT myelography and sometimes a spinal tap (lumbar puncture)
A peripheral nerve disorder (including polyneuropathies) or a neuromuscular junction disorder: Electromyography and usually nerve conduction studies
A muscle disorder (myopathy): Electromyography, usually nerve conduction studies, and possibly MRI, measurement of muscle enzymes, muscle biopsy, and/or genetic testing.
For CT myelography, CT is done after a needle is inserted into the lower back to inject a radiopaque dye into the fluid that surrounds the spinal cord.

For electromyography, a small needle is inserted into a muscle to record its electrical activity when the muscle is at rest and when it is contracting.
Nerve conduction studies use electrodes or small needles to stimulate a nerve. Then doctors measure how fast the nerve transmits signals.
A complete blood cell count (CBC)
Measurement of levels of electrolytes (such as potassium, calcium, and magnesium), sugar (glucose), and thyroid-stimulating hormone

Erythrocyte sedimentation rate (ESR), which can detect inflammation
Blood tests are sometimes done to evaluate kidney and liver function and to check for the hepatitis virus.
Magnetic Resonance Imaging (MRI) – A diagnostic procedure that uses a combination of large magnets, radio frequencies and a computer to produce detailed images of organs and structures within the body. This test is done to rule out any associated abnormalities of the spinal cord and nerves
Computerized Tomography Scan (also called a CT or CAT scan) – A diagnostic imaging procedure that uses a
combination of X-rays and computer technology to produce cross-sectional images (often called “slices”), both horizontally and vertically, of the body. A CT scan shows detailed images of any part of the body, including the bones, muscles, fat and organs. CT scans are more detailed than general X-rays
EEG (electroencephalogram) – a test that measures the electrical activity in the brain, called brain waves. An EEG measures brain waves through small button electrodes that are placed on your child’s scalp
Spinal tap – also called lumbar puncture, a spinal tap is done to measure the amount of pressure in the spinal canal and/or to remove a small amount of cerebral spinal fluid (CSF) for testing. Cerebral spinal fluid is the fluid that bathes your child’s brain and spinal cord
Karyotype – This test, a chromosomal analysis from a blood test, is used to determine whether the problem is the result of a genetic disorder
Muscle biopsy – a sample of muscle tissue is removed and examined under a microscope

Treatment

Here are the top simple and effective treatments for weakness:

Stay Hydrated: Dehydration can often cause fatigue. Make sure you drink an adequate amount of water each day to keep your body running smoothly.
Eat a Balanced Diet: Nutrient deficiencies can lead to weakness. Consuming a balanced diet rich in protein, carbohydrates, healthy fats, vitamins, and minerals can help boost your energy levels.
Exercise Regularly: Regular physical activity can help enhance your muscle strength and boost your energy levels. Start with light exercises and gradually increase the intensity.
Get Adequate Sleep: Quality sleep is essential for your body to recover and rejuvenate. Make sure you get 7-9 hours of sleep each night.
Take Multivitamins: Multivitamins can supplement your diet by filling in any nutrient gaps, helping to maintain overall health and ward off fatigue.
Limit Alcohol: Alcohol can interfere with the quality of your sleep, leading to fatigue. Try to moderate your alcohol consumption.
Cut Down on Caffeine: While it might give you a short-term energy boost, caffeine can also lead to energy crashes. Try to limit your caffeine intake.
Quit Smoking: Smoking can harm your lungs and decrease the oxygen supply to your body, leading to weakness. Consider quitting or reducing your tobacco usage.
Reduce Stress: High-stress levels can exhaust you mentally and physically. Practice stress-reducing activities like yoga, meditation, or deep breathing exercises.
Control Your Blood Sugar: Fluctuating blood sugar levels can lead to energy dips. Regularly monitoring and managing your blood sugar levels can help maintain consistent energy levels.
Consume Enough Protein: Protein is essential for muscle building and repair. Ensure you’re consuming enough protein each day to avoid muscle weakness.
Maintain a Healthy Weight: Being underweight or overweight can lead to fatigue. Aim to maintain a healthy weight through a balanced diet and regular exercise.
Manage Chronic Conditions: If you have a chronic condition such as diabetes or heart disease, managing these conditions can help reduce fatigue.
Avoid Allergens: Allergies can often cause fatigue. If you’re aware of any allergies you have, try to avoid exposure to those allergens.
Drink Green Tea: Green tea contains antioxidants that can help boost your energy levels.
Take Iron Supplements: Iron deficiency can lead to fatigue. Consult with your doctor about taking iron supplements if you’re deficient.
Get Regular Check-ups: Regular medical check-ups can help catch any health issues early that might be causing your weakness.
Practice Good Posture: Poor posture can lead to muscle fatigue. Ensure you’re maintaining good posture, especially if you’re sitting for extended periods.
Limit Screen Time: Overexposure to screens can strain your eyes and lead to fatigue. Try to take regular breaks from screens throughout the day.
Take Short Breaks: Short breaks during work can help prevent burnout and keep your energy levels stable.
Eat Small, Frequent Meals: Eating small meals throughout the day, rather than large meals, can help keep your energy levels steady.
Take B Vitamins: B vitamins are essential for energy production. Consider taking a B-complex supplement if your diet lacks these vitamins.
Avoid Processed Foods: Processed foods can lead to energy crashes. Try to consume whole, unprocessed foods as much as possible.
Stay Socially Active: Social interaction can help improve your mood and energy levels.
Limit Sugar Intake: While sugar might give you a quick energy boost, it can also lead to energy crashes. Try to moderate your sugar consumption.

Medications

Top drug treatments for weakness to give you a comprehensive understanding of your options. Remember, it’s essential to consult with your doctor before starting any new medication.

Iron Supplements: Iron deficiency often leads to weakness and fatigue. Taking iron supplements can replenish your body’s stores and restore your energy levels.
Vitamin B12 Supplements: If you have a vitamin B12 deficiency, this can result in a form of anemia and general weakness. Regular intake of B12 can help combat this.
Vitamin D Supplements: Lack of vitamin D, the “sunshine vitamin,” can lead to muscle weakness. Vitamin D supplements can help enhance muscle function and energy levels.
Coenzyme Q10: This is a substance that helps generate energy in your cells. Your body produces less of it as you age, so supplementation may help with feelings of weakness and fatigue.
Creatine: Commonly used by athletes for its energy-boosting properties, creatine can help increase muscle strength and reduce fatigue.
Beta-Alanine: This amino acid is known to delay muscle fatigue, improve endurance, and fight weakness.
Caffeine: It’s not just for your morning coffee! Caffeine tablets can help improve focus and fight off feelings of tiredness and fatigue.
Steroids: In some cases, doctors prescribe steroids to combat muscle weakness. However, these must be used under medical supervision due to potential side effects.
Modafinil: A prescription drug that promotes wakefulness, Modafinil is often used to treat excessive sleepiness and fatigue.
Amantadine: Originally used to prevent viral infections, Amantadine can also help manage fatigue in certain medical conditions.
Methylphenidate (Ritalin): This medication is often used for conditions like ADHD but can also help improve energy levels and reduce fatigue.
Dextroamphetamine (Adderall): A potent central nervous system stimulant, it can increase energy and decrease fatigue.
Melatonin: While it’s known as a sleep aid, having a regular sleep cycle can greatly reduce feelings of weakness and fatigue.
Donepezil: This drug is used to treat symptoms of dementia, including fatigue and muscle weakness.
Pyridostigmine: It is used for treating myasthenia gravis, a condition that causes muscle weakness.
Levodopa-Carbidopa (Sinemet): This combination medication is used to treat symptoms of Parkinson’s disease, such as muscle weakness.
Riluzole: This medication slows down the progression of ALS, a condition characterized by muscle weakness.
Edaravone (Radicava): Another treatment for ALS, this medication can help slow the progression of muscle weakness.
Tizanidine: This muscle relaxant is used for treating muscle spasms and weakness in conditions like multiple sclerosis.
Baclofen: A muscle relaxer and an antispastic agent, Baclofen is used to treat muscle symptoms such as spasms, pain, and weakness.
Dantrolene: This medication treats muscle spasticity and weakness in conditions like cerebral palsy.
Neostigmine: This drug is used to improve muscle tone in people with certain muscle diseases, like myasthenia gravis.
Azathioprine: It is used to treat conditions that cause muscle weakness like myasthenia gravis and multiple sclerosis.
Cyclosporine: This immune-suppressing drug can treat muscle weakness in conditions like myositis.
Prednisone: A type of steroid, Prednisone is often used to improve muscle strength in diseases like myasthenia gravis.
Mycophenolate Mofetil: This medication can treat diseases like myasthenia gravis and help improve muscle strength.
Immunoglobulin Therapy: This treatment uses a mixture of antibodies to boost the immune system and is used to treat several conditions that can cause weakness.
Plasmapheresis: This procedure removes harmful antibodies from your blood that may be causing muscle weakness.
Ephedrine: This medication stimulates the nervous system and can increase energy and reduce fatigue.
Venlafaxine: An antidepressant that can also help manage fatigue and weakness associated with certain conditions.

Remember, the right medication for you depends on your specific condition and overall health. Always consult with your healthcare provider to determine which of these options might be best for your situation.

In conclusion, while feeling weak can be distressing, there are numerous treatment options available that can help. Armed with this information, you can have an informed conversation with your healthcare provider and find the best course of treatment to restore your strength and vitality.

References

Weakness