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MACROCEPHALY
(MEGALENCEPHALY)
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Megalencephaly is defined as an occipitofrontal head circumference greater than 2 SD above the mean.
Tables and Graphs of normal
Occipitofrontal Diameter.
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ASSOCIATED ANOMALIES |
- Benign autosomal dominant megalencephaly.
- Cerebral gigantism.
- Beckwith - Wiedermann syndrome
- Hemangiomatosis (Bannayan-Zonana syndrome).
- Neurofibromatosis.
- Chromosomal syndromes (fragile X syndrome, Kleinfelter's syndrome).
- Walker-Warburg
syndrome
- Gorlin syndrome
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ULTRASOUND |
- Large fetal head (and a family history of large heads).
- Exclude any intracranial abnormalities that may cause an increase in fetal head size e.g. hydrocephalus, intracranial tumor or macrosomia.
- Unilateral megalencephaly.
- Unilateral hypertrophy of the affected hemisphere, often associated with ipsilateral ventricular dilatation and midline shift.
- May be hemihypertrophy of the cerebellum, brainstem and body.
- Thought to occur as a result of an insult to the germinal matrix between 8 and 16 post menstrual weeks of gestation.
- May find focal increased echogenicity of the affected hemisphere.
- No abnormal karyotypic abnormality has been described.
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REFERENCES |
- Ramirez M, Wilkins I, Kramer L et.al. Prenatal diagnosis of unilateral megalencephaly by real time ultrasonography Am J Obstet Gynecol 1994;170:1384-1385.
- Babyn P, Chuang S, Daneman A et.al. Sonographic recognition of unilateral megalencephaly. J Ultrasound Med 1992;11:563-566.