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Flaccid paralysis
Classification and external resources
ICD-10 G810, G820, G823
ICD-9 359.9

Flaccid paralysis (11px /ˈflæksɪd pəˈræləsɪs/) is a clinical manifestation characterized by weakness or paralysis and reduced muscle tone without other obvious cause (e.g., trauma).[1] This abnormal condition may be caused by disease or by trauma affecting the nerves associated with the involved muscles. For example, if the somatic nerves to a skeletal muscle are severed, then the muscle will exhibit flaccid paralysis. When muscles enter this state, they become limp and cannot contract. This condition can become fatal if it affects the respiratory muscles, posing the threat of suffocation.[2]



The term acute flaccid paralysis (AFP) is often used to describe a sudden onset, as might be found with polio.

AFP is the most common sign of acute polio, and used for surveillance during polio outbreaks. AFP is also associated with a number of other pathogenic agents including enteroviruses, echoviruses, and adenoviruses, among others.[3]


The Clostridium botulinum bacteria are the cause of botulism. Vegetative cells of C. botulinum may be ingested. Introduction of the bacteria may also occur via endospores in a wound. When the bacteria are in vivo, they induce flaccid paralysis. This happens because C. botulinum produces a toxin which blocks the release of acetylcholine. Botulism toxin blocks the exocytosis of presynaptic vesicles containing Acetylcholine (ACh).[4] When this occurs, the muscles are unable to contract.[5] Other symptoms associated with infection from this neurotoxin include double vision, blurred vision, drooping eyelids, slurred speech, difficulty swallowing, dry mouth, and muscle weakness. Botulism prevents muscle contraction by blocking the release of ACh, thereby halting postsynaptic activity of the neuromuscular junction. If its effects reach the respiratory muscles, then it can cause respiratory failure, leading to death.[6]


Curare is a poison that comes from a plant grown in the rainforests of South America. The people of South America crush and cook the roots and stems of curare and then mix it with venom from other plants and animals to create this poisonous syrup mixture that they put on the tips of their arrows. This poison has also been used by South Americans to treat madness, dropsy, edema, fever, kidney stones, and bruises.[7] Curare acts as a neuromuscular blocking agent which induces flaccid paralysis. This poison binds to the Acetylcholine (ACh) receptors on the muscle, blocking them from binding to ACh. As a result, ACh accumulates within the neuromuscular junction, but since ACh cannot bind to the receptors on the muscle, the muscle cannot be stimulated. This poison must enter the bloodstream for it to work. If curare affects the respiratory muscles, then its effects can become fatal, placing the victim at risk for suffocation.[8]


Flaccid paralysis can be associated with a lower motor neuron lesion. This is in contrast to a upper motor neuron lesion, which often presents with spastic paralysis, although early on this may present with flaccid paralysis. Included in AFP's list are Poliomyelitis (Polio), Transverse myelitis, Guillain-Barré syndrome, enteroviral encephalopathy [9], traumatic neuritis, Reye's syndrome etc. An AFP Surveillance programme is conducted to increase case yield of poliomyelitis. This includes collection of 2 stool samples within 14 days of onset of paralysis and identification of virus. and control of the outbreak and strengthening immunisation in that area.

Venomous snakes that contain neurotoxic venom such as kraits, mambas, and cobras can also cause complete flaccid paralysis.[citation needed]


  1. Alberta Government Health and Wellness (2005) Acute Flaccid Paralysis Public Health Notifiable Disease Management Guidelines.
  2. Saladin, Kenneth S. Anatomy & Physiology: The Unity of Form and Function. McGraw-Hill. 6th Edition. 2012.
  3. Kelly H, Brussen KA, Lawrence A, Elliot E, Pearn J, Thorley B (2006). Polioviruses and other enteroviruses isolated from faecal samples of patients with acute flaccid paralysis in Australia, 1996-2004. Journal of paediatrics and child health 42 (6): 370–6.
  4. Saladin, Kenneth S. Anatomy & Physiology: The Unity of Form and Function. McGraw-Hill. 6th Edition. 2012.
  5. Disease Listing, Botulism, General Information | CDC Bacterial, Mycotic Diseases
  8. Saladin, Kenneth S. Anatomy & Physiology: The Unity of Form and Function. McGraw-Hill. 6th Edition. 2012.
  9. Anis-ur-Rehman, Idris M, Elahi M, Jamshed, Arif A (Jan-Mar 2007). Guillain Barre syndrome: the leading cause of acute flaccid paralysis in Hazara division. J Ayub Med Coll Abbottabad 19 (1): 26–8.

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Wiktionary: flaccid

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