GIANT AXONAL NEUROPATHY
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ALTERNATE NAMES
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GAN; Giant Axonal Disease |
DESCRIPTION
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Giant Axonal Neuropathy (GAN) is a rare inherited genetic disorder that affects both the central and peripheral
nervous systems. GAN is caused by mutations in the GAN gene, the gene that provides
instructions for making a protein called gigaxonin, an important protein in cellular
development. The majority of children with GAN will begin to show symptoms of the
disease sometime before five years of age. Signs of GAN usually begin in the peripheral
nervous system, which controls movement and sensation in the arms, legs, and other
parts of the body. The typical symptoms of GAN are clumsiness and muscle weakness
that progresses from a “waddling gait” to a pronounced difficulty in walking. Additional
symptoms include numbness or lack of feeling in the arms and legs, seizures, nystagmus
(rapid back and forth movement of the eyes), and intellectual disability.
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DIAGNOSTIC TESTING, PHYSICAL FINDINGS, AND
ICD-9-CM/ICD-10-CM
CODING
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Diagnostic testing: The diagnosis of GAN is established by clinical findings including:
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Nerve conduction velocity (NCV);
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Brain magnetic resonance imaging (MRI);
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Peripheral nerve biopsy; and
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EEG (electroencephalogram).
A definitive diagnosis of GAN using genetic testing is available on a research basis.
Physical findings:
Physical examination of GAN may reveal:
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Impaired muscle coordination;
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ICD-9:
356.0
ICD-10:
G60.0
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PROGRESSION
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GAN usually appears in infancy or early childhood. GAN generally progresses slowly
as neurons degenerate and die. Most children have problems with walking in the early
stages of the disorder. Later they may lose sensation, coordination, strength, and
reflexes in their arms and legs. As time goes on, the brain and spinal cord may become
involved, causing a gradual decline in mental function, loss of control of body movement,
and seizures. Most children become wheelchair dependent in the second decade of life.
Some children may survive into early adulthood.
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TREATMENT
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There is no cure for this disorder. Treatment for GAN is symptom specific and supportive.
Children with GAN usually work with a medical team consisting of a pediatric neurologist,
orthopedic surgeon, physiotherapist, psychologist, and speech and occupational therapists.
The primary goal of treatment is to maximize intellectual and physical development
and improve adaptive functioning. Many children with GAN have normal intellectual
development and are able to attend regular school. As the disease progresses neurological
deterioration may occur. School age children may need to be monitored at least once
a year to assess their intellectual abilities and signs of neurological deterioration.
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SUGGESTED PROGRAMMATIC ASSESSMENT*
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Suggested MER for Evaluation:
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Clinical history and examination that describes the diagnostic features of the impairment
and laboratory findings are needed to confirm the diagnosis.
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Developmental assessment or psychological assessment to address allegations of mental
impairment may be warranted.
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Suggested Listings for Evaluation:
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DETERMINATION
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LISTING
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REMARKS
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Meets
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11.17
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Listing level neurological and/or cognitive findings must be documented; diagnosis
of GAN or laboratory testing results alone does not meet listing severity.
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111.17
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Listing level neurological and/or cognitive findings must be documented; diagnosis
of GAN or laboratory testing results alone does not meet listing severity.
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Equals
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111.02
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Must satisfy listing-level severity.
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112.02
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Must satisfy listing-level severity. |
* Adjudicators may, at their discretion, use the Medical Evidence of Record or the
listings suggested to evaluate the claim. However, the decision to allow or deny the
claim rests with the adjudicator.
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