ALOBAR HOLOPROSENCEPHALY

Alobar Holoprosencephaly (HPE) is the most severe type of holoprosencephaly, a structural anomaly of the brain that occurs early in gestational development. Inalobar HPE, there is a complete failure of the brain to divide into right and left hemispheres, resulting in the loss of midline structures of the brain and face, as well as fusion of the cavities (ventricles) of the brain.

The affected fetus is usually stillborn or dies soon after birth, or during the first 6 months of life. HPE may be associated with trisomy syndromes or other genetic mutations found in at least 14 different genes.

Diagnostic testing: MRI or CT of the brain

Physical findings: Most infants with alobar HPE have severe facial anomalies, including:

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  A single eye (cyclopia);

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  Very closely spaced eyes (ethmocephaly);

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  Absent eyes (anophthalmia);

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  Very small eye (microphthalmia) with a tubular-shaped nose (proboscis);

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  Closely spaced eyes (hypotelorism) and a flattened nose or cleft lip that occurs in the middle of the lip (median cleft lip) or on both sides (bilateral cleft lip).

Other findings may include:

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  Developmental delay;

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  Seizures;

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  Hydrocephalus (buildup of brain fluid);

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  Hypothalamic/pituitary and brain stem dysfunction;

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  Abnormal swallow or feeding difficulties; and

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  Failure to thrive/abnormal growth.

ICD-9: 742.2

Outcomes for HPE vary based upon the severity of the malformation. Approximately 50% of children with alobar HPE die in the first six months of life before age 4 to 5 months.

There is no cure for HPE. Treatment is symptomatic and supportive and may include antiepileptic drugs for seizures and hormone replacement therapy for pituitary dysfunction.

SUGGESTED PROGRAMMATIC ASSESSMENT*

Suggested MER for Evaluation:

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  Clinical history and physical examination that describes the diagnostic features of the impairment; and

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  Cranial MRI or CT.

Suggested Listings for Evaluation:

REMARKS

Only alobar HPE is considered to meet the criteria in listing 110.08 A. For lobar and semilobar HPE, as the clinical course is more variable, evaluate on a case-by-case basis under affected body systems; growth and development, and functional limitation.