Generalized weakness resident survival guide
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Moises Romo M.D.
Synonyms and Keywords: dystrophy, myasthenia gravis, Guillian-barre syndrome, polymyositis, emg
Overview
Generalized weakness or lack of strength is a direct term for the inability to exert force with ones muscles to the degree that would be expected given the individual's general physical fitness. The weakness may be caused due to affection in the muscle, nerve, or neuromuscular plate. Causes of generalized weakness may be as varied as cardiovascular, chemical, dermatologic, drugs side effects, endocrine, environmental, gastroenterologic, genetic, hematologic, iatrogenic, infectious, musculoskeletal, neurologic, nutritional, oncologic, overdose, psychiatric, and renal. A test of strength is often used during a diagnosis of a muscular disorder before the etiology can be identified. Many times, the cause of weakness may be identified with the history and physical examination; emg may guide into the type of weakness, but other times biopsy or other laboratory test may be necessary.
Causes
Life Threatening Causes
Life-threatening causes include conditions that may result in death or permanent disability within 24 hours if left untreated.
- Cadmium poisoning
- Dicamba poisoning
- Fluoride poisoning
- Hexane-2,5-dione poisoning
- Temik poisoning
- Benztropine Mesylate overdose
- Hypercalcemia
- Hyperkalaemic periodic paralysis
- Hypermagnesemia
- Hypermethioninemia
- Hypokalemic periodic paralysis
- Hypomagnesemia
- Hypophosphatemia
- Uremia
Common Causes
Diagnosis
Shown below is an algorithm summarizing the diagnosis of Generalized weakness according to the American Academy of Neurology guidelines:
| Generalized weakness symptoms | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| True motor weakness? | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| No | Yes | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Evaluate for causes of fatigue or muscle pain | Fluctuating | Constant | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| •Myasthenia Gravis •Lambert-Eaton syndrome •Periodic paralysis •Metabolic myopathy | Acquiered | Life-long/chronic | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| •Polymyositis •Dermatomyositis •Inclusion body myopathy •Amyotrophic lateral sclerosis •Multifocal motor neuropathy | Non-progessive | Progressive | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| •Congenital myopathy •Congenital dystrophy | Ocular •Kearns-sayre syndrome •Oculopharyngeal dystrophy •Ocular dystrophy | Facial •Fascioscapulohumeral dystrophy •Myotonic dystrophy | Upper extremities •Emery-Dreiffus dystrophy •Hereditary distal myopathy | Lower extremities •Duchenne's muscular dystrophy •Becker's muscular dystrophy •Sarcoglycanopathies •Spinal muscular atrophy •Limb girdle dystrophy | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Treatment
Treat the underlying cause.
- To view the treatment of Guillian-Barre syndrome click here.
- To view the treatment of Myasthenia Gravis click here.
- To view the treatment of Polymyositis click here.
- To view the treatment of Lambert-Eaton syndrome click here.
- To view the treatment of Botulism click here.
Do's
- Inquiere about social history and family history for genetic disorders.
- Review medications list.
- Look for upper motor and lower neuron motor signs.
- Evaluate if weakness is symetrical or asymetrical, as well as for exacerbating factors.
- Order TSH testing.
- Order glucose and vitamin B12 deficiency when deficiency is suspected.
- Order serum and urine testing for drug and toxins exposure.
- Perform electromyogram and nerve conduction test if lab results are inconclusive.
Don'ts
- Do not use a muscle biopsy as first testing modality; this should usually be reserved after all other diagnostic workup has failed to reveal a cause.