UNIQUE ANGIOGRAPHIC AND VENTRICULOGRAPHIC PATTERN OF ALOBAR HOLOPROSENCEPHALY (ARHINENCEPHALY).

Abstract

The brain malformation in which the prosencephalon fails to divide into hemispheres and cerebral lobes is termed alobar holoprosencephaly (arhinencephaly) (2). Almost all these patients have severe median facial defects such as orbital hypotelorism, a flat nose, and a median cleft of the lip. When present in typical patterns, the facial defects are pathognomonic of the malformed cerebrum (3). Rarely, an alobar holoprosencephalic patient has no striking or obvious facial defects, or the facial pattern may be atypical (4). In these cases, contrast studies should prove diagnostic of the alobar holoprosencephaly. Since the literature contains few previous radiographic studies of this condition (5, 8), we thought our findings in one patient would be of interest. Case Report The patient, a 4-month-old white male, had trigonocephaly, orbital hypotelorism, a flat nasal bridge, absence of the crista galli and nasal septum, and a median cleft of the lip and palate. The head was transilluminated. During the infant's six months of life, he had poikilothermia, convulsions and vomiting, and he made no psychomotor progress. The fontanels bulged, and the head increased in size because of increased intracranial pressure. The frontal bulging from the increased pressure acted to blunt the originally sharp keel of the trigonocephaly. Full clinical details are given elsewhere (2, Case III). At autopsy, the cerebrum was a saucer-shaped mass confined to the frontal region (Fig. 1, A and B). The basin of the saucer formed the floor of the cerebral monoventricle. The hippocampi (labeled 4 in Fig. 1, A) had failed to roll in to form the choroid fissure and to bury the thin, membranous, ventricular roof deep within the cerebral wall. Lacking support from the cerebral wall or confinement by a corpus callosum, the ventricular roof expanded from the margins of the saucer. The dorsal sac thus formed occupied most of the supratentorial space. Radiographic Studies Plain skull radiographs showed an inter-orbital distance of only 8 mm. No crista galli, nasal septum, premaxilla, or nasal bones were seen. The secondary palate had a median cleft. These findings, of themselves, are diagnostic of alobar holo-prosencephaly (8), but contrast procedures were undertaken because of the increased intracranial pressure, an unusual complication in this malformation. Through a needle puncture in the anterior fontanel, 40 cc of ventricular fluid was withdrawn from the dorsal sac and replaced with air. In Figure 2, A, the air sharply outlines the cerebral mass in the frontal region. The shelf projecting from the posterior edge of the cerebrum is the free margin of the gyrus cinguli homologue (mesopallium, labeled 6 in Fig. 1, A). By inverting the infant, the air bubble was traced around the vault until it became arrested against the tentorium cerebelli and dorsum of the cerebellum (Fig. 2, B).