Acute motor axonal neuropathy
Encyclopedia
Acute motor axonal neuropathy (AMAN) is a variant of Guillain-Barré syndrome
. It is characterized by acute paralysis
and loss of reflex
es without sensory
loss. Pathologically
, there is motor axonal
degeneration with antibody-mediated
attacks of motor nerves and nodes of Ranvier
.
and Pennsylvania State University
neurologists
in collaboration with neurologists from the Second Teaching Hospital of Hebei Medical School
and Beijing Children's Hospital. In 1991, Doctors Guy Mckhann, Jack Griffin, Dave Cornblath and Tony Ho from Johns Hopkins University and Dr. Arthur Asbury from University of Pennsylvania visited China to study a mysterious epidemic
of paralytic syndrome
occurring in northern China. Every summer, hundreds of children from rural China developed acute paralysis and respiratory failure
. Hospitals were overwhelmed with number of cases and often ran out of ventilators
and hospital beds. Examination of these children showed that many of them had acute flaccid paralysis
and areflexia
but with little or no sensory loss. Electrophysiological
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
confirmed the focus of the immune attack was at the motor axolemma
especially around the nodes of Ranvier. These cases showed deposition of antibody and complement
along the motor axolemma and associated macrophage
infiltration.
A link to Campylobacter jejuni
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.
show normal motor conduction velocity and latency with decreased amplitude of compound muscle action potential
s. F-waves and sensory nerve action potentials are often normal in this illness. Pathologically, it is a noninflammatory
axonopathy without demyelination. Antibodies attack the coating of the motor neurons without causing inflammation or loss of myelin
. It does not affect sensory neurons, so sensation remains intact despite loss of movement.
Guillain-Barré syndrome
Guillain–Barré syndrome , sometimes called Landry's paralysis, is an acute inflammatory demyelinating polyneuropathy , a disorder affecting the peripheral nervous system. Ascending paralysis, weakness beginning in the feet and hands and migrating towards the trunk, is the most typical symptom...
. It is characterized by acute paralysis
Paralysis
Paralysis is loss of muscle function for one or more muscles. Paralysis can be accompanied by a loss of feeling in the affected area if there is sensory damage as well as motor. A study conducted by the Christopher & Dana Reeve Foundation, suggests that about 1 in 50 people have been diagnosed...
and loss of reflex
Reflex
A reflex action, also known as a reflex, is an involuntary and nearly instantaneous movement in response to a stimulus. A true reflex is a behavior which is mediated via the reflex arc; this does not apply to casual uses of the term 'reflex'.-See also:...
es without sensory
Sensory system
A sensory system is a part of the nervous system responsible for processing sensory information. A sensory system consists of sensory receptors, neural pathways, and parts of the brain involved in sensory perception. Commonly recognized sensory systems are those for vision, hearing, somatic...
loss. Pathologically
Pathology
Pathology is the precise study and diagnosis of disease. The word pathology is from Ancient Greek , pathos, "feeling, suffering"; and , -logia, "the study of". Pathologization, to pathologize, refers to the process of defining a condition or behavior as pathological, e.g. pathological gambling....
, there is motor axonal
Motor neuron
In vertebrates, the term motor neuron classically applies to neurons located in the central nervous system that project their axons outside the CNS and directly or indirectly control muscles...
degeneration with antibody-mediated
Autoimmunity
Autoimmunity is the failure of an organism to recognize its own constituent parts as self, which allows an immune response against its own cells and tissues. Any disease that results from such an aberrant immune response is termed an autoimmune disease...
attacks of motor nerves and nodes of Ranvier
Nodes of Ranvier
Myelin sheath gaps or nodes of Ranvier are the gaps formed between the myelin sheaths generated by different cells. A myelin sheath is a many-layered coating, largely composed of a fatty substance called myelin, that wraps around the axon of a neuron and very efficiently insulates it...
.
History
AMAN, also known as Chinese Paralytic Syndrome, was first described by a group of Johns Hopkins UniversityJohns Hopkins University
The Johns Hopkins University, commonly referred to as Johns Hopkins, JHU, or simply Hopkins, is a private research university based in Baltimore, Maryland, United States...
and Pennsylvania State University
Pennsylvania State University
The Pennsylvania State University, commonly referred to as Penn State or PSU, is a public research university with campuses and facilities throughout the state of Pennsylvania, United States. Founded in 1855, the university has a threefold mission of teaching, research, and public service...
neurologists
Neurology
Neurology is a medical specialty dealing with disorders of the nervous system. Specifically, it deals with the diagnosis and treatment of all categories of disease involving the central, peripheral, and autonomic nervous systems, including their coverings, blood vessels, and all effector tissue,...
in collaboration with neurologists from the Second Teaching Hospital of Hebei Medical School
Hebei University
Hebei University is the only Comprehensive University in Hebei which is directly under Hebei provincial government and the Ministry of Education, China. It's located in Baoding, Hebei Province, China....
and Beijing Children's Hospital. In 1991, Doctors Guy Mckhann, Jack Griffin, Dave Cornblath and Tony Ho from Johns Hopkins University and Dr. Arthur Asbury from University of Pennsylvania visited China to study a mysterious epidemic
Epidemic
In epidemiology, an epidemic , occurs when new cases of a certain disease, in a given human population, and during a given period, substantially exceed what is expected based on recent experience...
of paralytic syndrome
Paralysis
Paralysis is loss of muscle function for one or more muscles. Paralysis can be accompanied by a loss of feeling in the affected area if there is sensory damage as well as motor. A study conducted by the Christopher & Dana Reeve Foundation, suggests that about 1 in 50 people have been diagnosed...
occurring in northern China. Every summer, hundreds of children from rural China developed acute paralysis and respiratory failure
Respiratory failure
The term respiratory failure, in medicine, is used to describe inadequate gas exchange by the respiratory system, with the result that arterial oxygen and/or carbon dioxide levels cannot be maintained within their normal ranges. A drop in blood oxygenation is known as hypoxemia; a rise in arterial...
. Hospitals were overwhelmed with number of cases and often ran out of ventilators
Medical ventilator
A medical ventilator can be defined as any machine designed to mechanically move breatheable air into and out of the lungs, to provide the mechanism of breathing for a patient who is physically unable to breathe, or breathing insufficiently....
and hospital beds. Examination of these children showed that many of them had acute flaccid paralysis
Flaccid paralysis
Flaccid paralysis is a clinical manifestation characterized by weakness or paralysis and reduced muscle tone without other obvious cause .-Polio:...
and areflexia
Reflex
A reflex action, also known as a reflex, is an involuntary and nearly instantaneous movement in response to a stimulus. A true reflex is a behavior which is mediated via the reflex arc; this does not apply to casual uses of the term 'reflex'.-See also:...
but with little or no sensory loss. Electrophysiological
Electrophysiology
Electrophysiology is the study of the electrical properties of biological cells and tissues. It involves measurements of voltage change or electric current on a wide variety of scales from single ion channel proteins to whole organs like the heart...
testing of these children showed motor axonal loss with occasional conduction block with a lack of demyelinating
Demyelinating disease
A demyelinating disease is any disease of the nervous system in which the myelin sheath of neurons is damaged. This impairs the conduction of signals in the affected nerves, causing impairment in sensation, movement, cognition, or other functions depending on which nerves are involved.The term...
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
Autopsy
An autopsy—also known as a post-mortem examination, necropsy , autopsia cadaverum, or obduction—is a highly specialized surgical procedure that consists of a thorough examination of a corpse to determine the cause and manner of death and to evaluate any disease or injury that may be present...
confirmed the focus of the immune attack was at the motor axolemma
Axolemma
The axolemma is the cell membrane surrounding an axon. It is responsible for maintaining the membrane potential of the neuron, and it contains ion channels through which ions can flow. When this occurs, the voltage inside the axon changes, and depolarization or hyperpolarization of the membrane can...
especially around the nodes of Ranvier. These cases showed deposition of antibody and complement
Complement system
The complement system helps or “complements” the ability of antibodies and phagocytic cells to clear pathogens from an organism. It is part of the immune system called the innate immune system that is not adaptable and does not change over the course of an individual's lifetime...
along the motor axolemma and associated macrophage
Macrophage
Macrophages are cells produced by the differentiation of monocytes in tissues. Human macrophages are about in diameter. Monocytes and macrophages are phagocytes. Macrophages function in both non-specific defense as well as help initiate specific defense mechanisms of vertebrate animals...
infiltration.
A link to Campylobacter jejuni
Campylobacter jejuni
Campylobacter jejuni is a species of curved, helical-shaped, non-spore forming, Gram-negative, microaerophilic bacteria commonly found in animal feces. It is one of the most common causes of human gastroenteritis in the world. Food poisoning caused by Campylobacter species can be severely...
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.
Presentation and Diagnosis
The syndrome typically presents as a progressive flaccid symmetric paralysis with areflexia, often causing respiratory failure. Electromyographic studies and nerve conduction studiesNerve conduction study
A nerve conduction study is a test commonly used to evaluate the function, especially the ability of electrical conduction, of the motor and sensory nerves of the human body.Nerve conduction velocity is a common measurement made during this test...
show normal motor conduction velocity and latency with decreased amplitude of compound muscle action potential
Action potential
In physiology, an action potential is a short-lasting event in which the electrical membrane potential of a cell rapidly rises and falls, following a consistent trajectory. Action potentials occur in several types of animal cells, called excitable cells, which include neurons, muscle cells, and...
s. F-waves and sensory nerve action potentials are often normal in this illness. Pathologically, it is a noninflammatory
Inflammation
Inflammation is part of the complex biological response of vascular tissues to harmful stimuli, such as pathogens, damaged cells, or irritants. Inflammation is a protective attempt by the organism to remove the injurious stimuli and to initiate the healing process...
axonopathy without demyelination. Antibodies attack the coating of the motor neurons without causing inflammation or loss of myelin
Myelin
Myelin is a dielectric material that forms a layer, the myelin sheath, usually around only the axon of a neuron. It is essential for the proper functioning of the nervous system. Myelin is an outgrowth of a type of glial cell. The production of the myelin sheath is called myelination...
. It does not affect sensory neurons, so sensation remains intact despite loss of movement.