ALTERNATE
NAMES
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Arginyl-Trna Synthetase; Cerebellar Atrophy with Progressive Microcephaly; CLAM; Congenital
Pontocerebellar Hypoplasia; Encephalopathy, Fatal Infantile, with Olivopontocerebellar
Hyperplasia; Fetal-Onset Olivopontocerebellar Hypoplasia; Olivopontocerebellar Hypoplasia,
Fetal-Onset; PCH with Optic Atrophy; Pontocerebellar Hypoplasia with Anterior Horn
Cell Disease; Pontocerebellar Hypoplasia with Infantile Spinal Muscular Atrophy; Pontocerebellar
Hypoplasia with Progressive Cerebral Atrophy; RARS; Volendam Neurodegenerative Disease
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DESCRIPTION
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Pontocerebellar
hypoplasia
(PCH) is a group of related conditions that affect the development of the brain. The term
"pontocerebellar" refers to the pons and the cerebellum, which are the brain structures
that are most severely affected in many forms of this disorder. The pons is located
at the base of the brain in an area called the brainstem, where it transmits signals
between the cerebellum and the rest of the brain. The cerebellum, which is located
at the back of the brain, normally coordinates movement. The term "hypoplasia" refers
to the underdevelopment of these brain regions.
PCH also causes impaired growth of other parts of the brain, leading to an unusually
small head size (microcephaly). This microcephaly is usually not apparent at birth
but becomes noticeable as brain growth continues to be slow in infancy and early childhood.
PCH can result from mutations in several genes. About half of all cases of PCH type
1 (PCH1) are caused by mutations in the EXOSC3 gene. PCH1 can also result from mutations in several other genes, including TSEN54, RARS2, and VRK1. PCH type 2 (PCH2) is caused by mutations in the TSEN54, TSEN2, TSEN34, or SEPSECS gene. caused by mutations in other genes. In some cases, the genetic cause of PCH
is unknown.
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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 PCH is made by:
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A history and physical exam;
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Genetic testing (only available for certain types);
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Magnetic resonance imaging (MRI) of the brain and spinal cord;
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Computed tomography (CT) scan of the brain;
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Nerve conduction studies;
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Electroencephalograph (EEG) scan; and
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Muscle, skin, and nerve biopsy (in types with known genetic mutations.
Physical findings: Signs and symptoms for PCH vary depending on the type. The signs and symptoms that
are consistent for all types of PCH are:
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Abnormally small cerebellum and brain stem;
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Problems with movement; and
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Severe to profound intellectual disability.
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Other signs and symptoms of PCH may include:
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Microcephaly (abnormally small head size);
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Encephalopathy (impaired brain function);
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Nystagmus (uncontrolled eye movements);
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Ataxia (lack of muscle control or coordination of voluntary movements);
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Dystonia (involuntary repetitive or twisting movements;
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Hypotonia (poor muscle tone);
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Hypertonia (too much muscle tone); and
ICD-9: 742.2
ICD-10: Q04.3
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PROGRESSION
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Researchers have described at least 10 types of PCH. All forms of this condition are
characterized by impaired brain development, delayed development overall, problems
with movement, and intellectual disability. The brain abnormalities are usually present
at birth, and in some cases, they can be detected before birth. Many children with
PCH live only into infancy or childhood, although some affected individuals have lived
into adulthood.
The prevalence of PCH is unknown, although most forms of the disorder appear to be
very rare.
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TREATMENT
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There is no known cure for PCH. Treatment of PCH is symptomatic and supportive.
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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;
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Genetic testing (only available for certain types);
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MRI of the brain and spinal cord;
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Nerve conduction studies;
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Muscle, skin, and nerve biopsy (in types with known genetic mutations).
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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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111.08 A or B
111.22 A
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Equals
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* Adjudicators may, at their discretion, use the Medical Evidence of Record or the
listings suggested evaluating the claim. However, the decision to allow or deny the
claim rests with the adjudicator.
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