Aprosencephaly: review of the literature and report of a case with cerebellar hypoplasia, pigmented epithelial cyst and Rathke's cleft cyst.

Aprosencephaly is a very rare brain malformation that occurs in isolated and sydromatic forms. The syndromatic form has been named "XK-aprosencephaly", and is characterized by near total absence of prosencephalon with a midline oculofacial defect similar to the most severe forms of holoprosencephaly, in association with limb and genital anomalies. We present a case of syndromatic aprosencephaly with absence of thumb and abnormal external genitalia. A previously undescribed finding was a Rathke's cleft cyst. Two other cystic structure were also identified--an ependymal cyst, which may represent a dorsal cyst as in holoprosencephaly, and a pigmented epithelial cyst, which may represent a rudimentary eye. Additional findings were extensive calcific vasculopathy in the rudimentary prosencephalon, absence of pituitary gland, forking of the aqueduct of Sylvius and marked cerebellar hypoplasia. Since calcific vasculopathy is a common accompaniment of other inflammatory diseases of the central nervous system, its presence in this case suggests that destructive processes may be involved in the genesis of some cases of aprosencephaly.