Acute motor axonal

neuropathy Peripheral neuropathy, often shortened to neuropathy, is a general term describing disease affecting the peripheral nerves, meaning nerves beyond the brain and spinal cord. Damage to peripheral nerves may impair sensation, movement, gland, or o ...

(AMAN) is a variant of

Guillain–Barré syndrome Guillain–Barré syndrome (GBS) is a rapid-onset muscle weakness caused by the immune system damaging the peripheral nervous system. Typically, both sides of the body are involved, and the initial symptoms are changes in sensation or pain often ...

. It is characterized by acute

paralysis Paralysis (also known as plegia) is a loss of motor function in one or more muscles. Paralysis can also be accompanied by a loss of feeling (sensory loss) in the affected area if there is sensory damage. In the United States, roughly 1 in 50 ...

and loss of

reflex In biology, a reflex, or reflex action, is an involuntary, unplanned sequence or action and nearly instantaneous response to a stimulus. Reflexes are found with varying levels of complexity in organisms with a nervous system. A reflex occurs ...

es without sensory loss. Pathologically, there is motor axonal degeneration with antibody-mediated attacks of motor nerves and

nodes of Ranvier In neuroscience and anatomy, nodes of Ranvier ( ), also known as myelin-sheath gaps, occur along a myelinated axon where the axolemma is exposed to the extracellular space. Nodes of Ranvier are uninsulated and highly enriched in ion channels, al ...

Signs and symptoms

Causes

A link to ''

Campylobacter jejuni ''Campylobacter jejuni'' () is a species of pathogenic bacteria, one of the most common causes of food poisoning in Europe and in the US. The vast majority of cases occur as isolated events, not as part of recognized outbreaks. Active surveillan ...

'' was suspected when a young girl was admitted to Second Teaching Hospital. She had become ill after feeding the family chickens. She developed acute paralysis and respiratory failure. Investigators discovered that several of the chickens in the home displayed similar symptoms and ''C. jejuni'' was found in their droppings. Several of the paralysis patients were found to have antibodies to ''C. jejuni'' and anti-GD1a antibodies, suggesting a link between the pathogen and the disease. In 2015,

Zika virus ''Zika virus'' (ZIKV; pronounced or ) is a member of the virus family ''Flaviviridae''. It is spread by daytime-active '' Aedes'' mosquitoes, such as '' A. aegypti'' and '' A. albopictus''. Its name comes from the Ziika Forest of Uganda, w ...

was linked to AMAN.

Diagnosis

The syndrome typically presents as a progressive flaccid symmetric paralysis with

areflexia Hyporeflexia is the reduction or absence of normal bodily reflexes (areflexia). It can be detected through the use of a reflex hammer and is the opposite of hyperreflexia. Hyporeflexia is generally associated with a deficit in the lower motor neu ...

, often causing respiratory failure. Electromyographic studies and

nerve conduction studies A nerve conduction study (NCS) is a medical diagnostic test commonly used to evaluate the function, especially the ability of electrical conduction, of the motor and sensory nerves of the human body. These tests may be performed by medical spec ...

show normal motor conduction velocity and latency with decreased amplitude of compound muscle

action potential An action potential occurs when the membrane potential of a specific cell location rapidly rises and falls. This depolarization then causes adjacent locations to similarly depolarize. Action potentials occur in several types of animal cells, ...

s. Pathologically, it is a noninflammatory axonopathy without demyelination. Antibodies attack the coating of the motor neurons without causing inflammation or loss of

myelin Myelin is a lipid-rich material that surrounds nerve cell axons (the nervous system's "wires") to insulate them and increase the rate at which electrical impulses (called action potentials) are passed along the axon. The myelinated axon can be ...

. It does not affect sensory neurons, so sensation remains intact despite loss of movement.

Treatment

the majority of patients have complete symptom resolution with 5-day intravenous immunoglobulin (IV Ig) treatment. Patients with AMAN continue to see improvements in ambulation and functional ability up to four years post-diagnosis.

History

AMAN, also known as Chinese Paralytic Syndrome,Biller J. Practical Neurology, Second Edition. Lippincott Williams and Wilkins; 2002:Pg 361 was first described by a group of

Johns Hopkins University Johns Hopkins University (Johns Hopkins, Hopkins, or JHU) is a private university, private research university in Baltimore, Maryland. Founded in 1876, Johns Hopkins is the oldest research university in the United States and in the western hem ...

and

University of Pennsylvania The University of Pennsylvania (also known as Penn or UPenn) is a private research university in Philadelphia. It is the fourth-oldest institution of higher education in the United States and is ranked among the highest-regarded universitie ...

neurologists Neurology (from el, νεῦρον (neûron), "string, nerve" and the suffix -logia, "study of") is the branch of medicine dealing with the diagnosis and treatment of all categories of conditions and disease involving the brain, the spinal ...

in collaboration with neurologists from the Second Teaching Hospital of Hebei Medical School and

Beijing Children's Hospital } Beijing ( ; ; ), alternatively romanized as Peking ( ), is the capital of the People's Republic of China. It is the center of power and development of the country. Beijing is the world's most populous national capital city, with over 21 ...

. In 1991, Guy Mckhann, Jack Griffin, Dave Cornblath and Tony Ho from Johns Hopkins University and Arthur Asbury from University of Pennsylvania visited China to study a mysterious

epidemic An epidemic (from Ancient Greek, Greek ἐπί ''epi'' "upon or above" and δῆμος ''demos'' "people") is the rapid spread of disease to a large number of patients among a given population within an area in a short period of time. Epidemics ...

of paralytic syndrome occurring in northern China. Every summer, hundreds of children from rural China developed acute paralysis and

respiratory failure Respiratory failure results from inadequate gas exchange by the respiratory system, meaning that the arterial oxygen, carbon dioxide, or both cannot be kept at normal levels. A drop in the oxygen carried in the blood is known as hypoxemia; a rise ...

. Hospitals were overwhelmed with number of cases and often ran out of

ventilators A ventilator is a piece of medical technology that provides mechanical ventilation by moving breathable air into and out of the lungs, to deliver breaths to a patient who is physically unable to breathe, or breathing insufficiently. Ventilators ...

and hospital beds. Examination of these children showed that many of them had acute

flaccid paralysis Flaccid paralysis is a neurological condition characterized by weakness or paralysis and reduced muscle tone without other obvious cause (e.g., trauma). This abnormal condition may be caused by disease or by trauma affecting the nerves associ ...

and

but with little or no sensory loss.

Electrophysiological Electrophysiology (from Greek , ''ēlektron'', "amber" etymology of "electron"">Electron#Etymology">etymology of "electron" , ''physis'', "nature, origin"; and , ''-logia'') is the branch of physiology that studies the electrical properties of bi ...

testing of these children showed motor axonal loss with occasional conduction block with a lack of demyelinating features and normal sensory potentials. In contrast, the common form of Guillain–Barré syndrome in the West often presents with sensory loss and demyelination on electrophysiology testing and is more common in adults. Later, several

autopsies An autopsy (post-mortem examination, obduction, necropsy, or autopsia cadaverum) is a surgical procedure that consists of a thorough examination of a corpse by dissection to determine the cause, mode, and manner of death or to evaluate any d ...

confirmed the focus of the immune attack was at the motor

axolemma In neuroscience, the axolemma (, and 'axo-' from axon) is the cell membrane of an axon, the branch of a neuron through which signals (action potentials) are transmitted. The axolemma is a three-layered, bilipid membrane. Under standard electron m ...

especially around the nodes of Ranvier. These cases showed deposition of antibody and

complement A complement is something that completes something else. Complement may refer specifically to: The arts * Complement (music), an interval that, when added to another, spans an octave ** Aggregate complementation, the separation of pitch-clas ...

along the motor axolemma and associated

macrophage Macrophages (abbreviated as M φ, MΦ or MP) ( el, large eaters, from Greek ''μακρός'' (') = large, ''φαγεῖν'' (') = to eat) are a type of white blood cell of the immune system that engulfs and digests pathogens, such as cancer cel ...

infiltration.

References

External links

{{DEFAULTSORT:Acute Motor Axonal Neuropathy Neurological disorders Syndromes affecting the nervous system