amen of Monro from a neoplasm such as a thalamic tumor [1]. Other causes include choroid plexus cyst, abscess, vas- cular anomaly, gliomatosis, post inflam-.
Pediatr Radiol (1993) 23:69~0
Pediatric Radiology 9 Springer-Verlag 1993
Prenatal diagnosis of unilateral hydrocephalus N. Anderson 1, T. Malpas 2, M. Davison 3 Department of Radiology, Christchurch Hospital, Christchurch, New Zealand 2Department of Paediatrics, Christchurch Hospital, Christchurch, New Zealand 3Department of Neurosurgery, Christchurch Hospital, Christchurch, New Zealand Received: 6 July 1992/Accepted: 17 September 1992
Abstract. We report a case of unilateral hydrocephalus diagnosed at 20 weeks' gestation, at which time marked facial and cranial asymmetry was present already. Brain mantle reconstitution was Correspondence to: N. Anderson
incomplete following vetriculo-peritoneal shunting, and the child has significant neurodevelopmental disability.
Unilateral hydrocephalus is rare. It is usually due to obstruction of the foramen of M o n r o from a neoplasm such as
Fig.1. Coronalviewoffetalheadand face through frontal region and orbits at 20 weeksgestation. The left hemicranium is considerably smaller than the right, and the falx is deviated. F, falx; L, left; R, right; O, orbit; M, mandible Fig. 2. Axial image of fetal brain at 22 weeks gestation showing marked unilateral ventriculomegaly (occipital horn between markers) and axial asymmetry of the falx. V, occipital horn of enlarged right ventricle (between markers); F, falx; C, choroid plexus in normal-sized left lateral ventricle Fig. 3. Axial computed tomogram at 7 days of age showing marked asymmetry of the brain with marked enlargement of the body and occipital horn of the right lateral ventricle. The right choroid plexus is hanging, the left choroid plexus is normal. F, falx; C, choroid plexus; T, third ventricle
a thalamic tumor [1]. Other causes include choroid plexus cyst, abscess, vascular anomaly, gliomatosis, post inflammatory (including mumps), and congenital atresia [1]. We report a case of unilateral hydrocephalus due to atresia of the foramen of M o n r o diagnosed at 20 weeks gestation.
Casereport A 33-year-old white woman, a smoker, in her fourth pregnancy (3 previous normal pregnancies) had pregnancy ultrasound at 20 weeks as she seemed large for dates. The fetus had unilateral right ventriculomegaly (Figs. 1, 2). No other fetal anomaly was seen. The appearances remained similar on subsequent scans apart from growth. Pregnancyinduced hypertension developed at 33 weeks gestation. An emergency caesarian section
70 was performed for fetal distress following elective induction of labour at 36 weeks, and a male baby weighing 2.28 kg with prominence of the right side of his head and face was delivered. His head circumference was 37 cm. His first seizure occurred at 24 h of age. Postnatal ultrasound and computed tomography confirmed the antenatal findings of marked unilateral isolated ventriculomegaly (Fig. 3). Recurrent seizures were controlled with anticonvulsant therapy. A ventriculoperitoneal shunt was inserted at 14 days of age. The cerebrospinal fluid was clear but at moderately elevated pressure. Following shunting the right lateral ventricle decreased in size but remained moderately dilated. At 6 months of age the boy developed a raised, pigmented nevus in the distribution of the right fifth cranial nerve. By 1 year of age, his left hemiparesis persisted, he had global developmental delay, but his seizures were moderately well controlled by a regimen of phenobarbitone, sodium valproate and clonazepam.
Discussion Prenatally diagnosed ventriculomegaly (hydrocephalus) almost always is bilateral. In general it has a poor prognosis, with approximately 85% mortality, often related to associated anomalies. Only 7.5 % of victims are likely to have normal psychomotor development [2]. Unilateral ventriculomegaly due to congenital atresia of the foramen of Monro has a very different prognosis. The survival rate is over 70 %, and a normal developmental outcome can be anticipated in most cases, provided no other anomalies are present. In all published
cases, ventriculoperitoneal shunting has been required because of progressive head enlargement. Fourteen cases in which congenital atresia or stenosis of the foramen of Monro causing unilateral hydrocephalus was diagnosed in the perinatal period have been published. In 6 cases, the diagnosis was made antenatally [1, 3-5], at 2836 weeks. The only infant to die had multiple other congenital anomalies. The 5 who survived all had ventriculoperitoneal shunts, and 4 are developmentally normal. The other infant has intractable seizures and a poor prognosis. Interestingly, this infant is the only one in whom the brain mantle remained thinned following shunting. In the other 4, almost complete reconstitution of brain mantle thickness occurred following shunting. The significant features in our case are that the diagnosis was made at 20 weeks gestation, when considerable midline shift had already occurred, yet ventriculomegaly was only moderate. Despite shunting, the child remains seriously impaired at 1 year of age with intractable seizures, developmental delay, and hemiparesis. Brain mantle reconstitution following shunting was only moderate. The asymmetry of the cranium and attachment of the falx was present even at 20 weeks gestation. This implies that in our case the abnormality leading to atresia of the foramen of Monro was present from very early in the gestation. Perhaps the poor outcome was predetermined.
In the light of the admittedly limited literature on unilateral hydrocephalus, we believe the following statements can be made. The prognosis is much better than for bilateral hydrocephalus. Ventriculoperitoneal shunting is likely to be needed within the first month of life. If brain mantle reconstitution is evident soon after shunting, a favourable prognosis can be expected. If brain mantle reconstitution is limited, or the infant has seizures, the prognosis remains guarded.
Acknowledgement. We are grateful for assistance from Mr Martin MacFarlane, who was responsible for the neurosurgical care of this child.
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