Address Correspondence to Gary M. Joffe, MD, Department of Maternal-Fetal Medicine, University of New Mexico Medical Center, 4th Floor, ACC 2211 Lomas, N.E., Albuquerque, NM 87131-     Ph: 502-272-6386 Fax: 505-272-6385

Synonyms: Vesiculocephaly¹.

Definition: Disproportionate enlargement of the occipital horns of the lateral ventricles in association with partial or complete agenesis of the corpus callosum.

Etimology: Greek: koiloV, kolpoV: hollow and kefalh: head

Prevalence: Approximately 36 cases have been described in children, but the antenatal diagnosis is infrequent².

Etiology: Two theories are debated in the literature. The generally accepted theory is that of interrupted migration of white matter precursor cells during the first two to five months of fetal life^1,3,4. Fibers radiating from and associated with the corpus callosum, such as the anterior forceps, tapetum, and optic radiation are atrophic or absent. Absence of these structures in the parieto-occipital regions leads to large outpouchings of the posterior ventricular system⁴. The second theory, perhaps less accepted, is that of local destruction of previously formed elements that give rise to the walls of the occipital horns of the lateral ventricles². Associated findings have included trisomy 8 mosaic⁵, trisomy 9 mosaic², Toxo­plasma gondii², maternal ingestion of alcohol, oral contraceptive medication, diethylpropion hydrochloride (Tenuate^®), and doxylamine succinate (Bendectin^®)².

Associated anomalies: Optic nerve hypoplasia, chorioretinal coloboma, microcephaly, micrognathia, cleft palate, hypoplastic nails, simian creases, cerebellar atrophy⁶, enlargement of the cisterna magna, microgyria, macrogyria, pachygyria, lissencephaly⁷, meningomyelocele, Pierre-Robin syndrome⁶, neurofibromatosis⁶, schiz­encephaly³.

Differential diagnosis: Poren­cephaly, stenosis of interventricular foramen, supratentorial ara­chnoid cyst.

Prognosis: Mild to severe mental retardation, poor vision, mild to severe seizures, developmental delay. Occasional report of normal physical and neurodevelopmental assessment.

Recurrence risk: No reported figures given in the literature.

Management: Prenatal diagnosis should prompt search for associated anomalies, karyotypic abnormality, gestational viral exposure, and maternal toxin ingestion.

MESH Cerebral-ventricles-abnormalities BDE 2012 CDC 742.280 ICD9 742.2

Introduction

The term colpocephaly, meaning disproportionate enlargement of the posterior horns of the lateral ventricles, is found throughout the neurology literature. However, the term is rarely found in the radiology literature. Perhaps, this is due to lack of consensus regarding the pathogenesis of the process, numerous reported etiologic associations, and lack of strict definition. The following is a case report of antenatal diagnosis of colpoce­phaly, and a review of the literature.

Case report

The patient is a 26-year-old G₁ white woman referred to our institution at 34 weeks of gestation for evaluation of fetal ventriculomegaly. Her prenatal course had been remarkable for an elevated maternal serum alpha-fetoprotein at 16 weeks. Amniocentesis revealed a 46 XX karyotype and a normal amniotic fluid alpha-fetoprotein. At 28 weeks of gestation, she was noted to have a lag in fundal height. Repeat ultrasound revealed the fetus to have measurements consistent with 26 weeks of gestation. The cisterna magna measured 10mm. A repeat ultrasound was obtained at 34 weeks of gestation. Biometric measurements were reportedly consistent with 31 weeks, and ventriculomegaly (fig. 1) was noted for the first time.

Figure 1: Dilatation of the occipital horns without concomitant distention of the rest of the ventricular system.

Upon referral to our institution at 35 weeks, an abdominal ultrasound revealed a symmetrically growth retarded fetus with an estimated fetal weight of 1574g—well below the 5^th percentile for gestational age. The intracranial anatomy was significant for marked enlargement of the occipital horn of the lateral ventricles: the largest diameter measuring 22 mm (fig. 1-3).

Figure 2: A drooping choroid plexus is seen in the distended occipital horn.

Figure 3: The third ventricle is not distended.

In addition, the atria measured 14mm. The atrophic cerebellum measured 28mm in diameter, with the vermis noted to be present (fig. 4). The cisterna magna was enlarged. The remaining intracranial anatomy appeared normal. The remainder of the anatomy appeared normal, as did the amniotic fluid index and Doppler assessment of umbilical arterial systolic to diastolic flow ratio.

Figure 4: The cisterna magna is large.

At 37 weeks of gestation, non-stress testing revealed a late appearing fetal heart rate deceleration with an isolated contraction. A contraction stress test was performed and was positive. A cesarean section was performed with delivery of a 2170g female infant with Apgar"s of 4 and 7 at one and five minutes, respectively. The infant"s peripartum course was complicated by a transient episode of bradycardia, but was otherwise unremarkable. Serum TORCH titers were negative.

Magnetic resonance imaging of the infant"s cranium revealed marked enlargement of both occipital horns of the lateral ventricles, agenesis of the corpus callosum, cerebellar hypoplasia, and enlargement of the cisterna magna (fig. 5). The infant was discharged home on the fifth day of life.

Figure 5: Coronal and axial MRI of the newborn head reveals marked enlargement of both occipital horns of the lateral ventricles, agenesis of the corpus callosum, cerebellar hypoplasia, and enlargement of the cisterna magna.

Discussion

Prevalence

Approximately 36 reports of colpocephaly have appeared in the literature. This figure may be misleading, however, as there is a lack of consensus as to the precise definition of the term colpocephaly.

Most authors appear to agree that the findings of colpocephaly include disproportionate enlargement of the occipital horns, with the remaining ventricular system maintaining normal size and configuration. In addition, most, but not all, authors believe that the condition is associated with partial or complete agenesis of the corpus callosum².

Definition

The debate in the literature centers around the morphogenesis of the process, with some authors viewing it strictly as developmental anomaly³. Others view the term colpocephaly as only being descriptive. They find no inconsistency in using the term to describe isolated occipital ventriculomegaly resulting from destruction of neural elements that had previously been normally formed².

From the standpoint of antenatal diagnosis, the term should probably be  descriptive of isolated occipital ventriculomegaly rather than as a unique clinical entity. This is because, in most cases, the underlying etiology, be it failure of morphogenesis or a destructive process, will not be known.

Embryology

The lateral ventricles arise as cavities within the telencephalon. The telencephalon gives rise to two diverticula that expand over the diencephalon and mesencephalon to give rise to the cerebral hemispheres. "During the third gestational month, there is formation of the temporal pole and the ventricles are now in a `U" shape⁴".

The appearance and growth of the occipital ventricular projection takes place between 23 and 34 weeks⁸.

The normal reduction in diameter of the occipital horns of the lateral ventricles is critically dependent upon correct morphogenesis of the corpus callosum. "The fibers of the corpus callosum, the forceps and the tapetum, the internal parietooccipital fissure, and the calcarine fissure all take part in shaping and reducing the size of the occipital horn⁴".

Pathogenesis

The term colpocephaly was originally coined by Yakovlev and Wadsworth, who stated that "in the apparent dilatation of the occipital horns...it represented a failure of development of the cerebral wall with persistence of the embryonal vesicular character of the brain³".

If colpocephaly is the result of abnormal morphogenesis, then any process that inhibits the normal neuronal migration from within the ventricle, and likewise the normal genesis of the corpus callosum, may result in this entity.

Clearly, however, not all patients with agenesis of the corpus callosum manifest isolated ventriculomegaly of the occipital horns. Therefore, the precise pathogenesis of this process remains incompletely explained.

Etiology

Colpocephaly has been associated with chromosomal anomalies such as trisomy 8 mosaic⁵ and trisomy 9 mosaic². Infectious associations have included gestational exposure to Toxoplasma gondii². Maternal gestational ingestion of ethanol, oral contraceptive medications, dipropion hydrochloride (Tenuate^®)^, and doxylamine succinate (Bendectin^®) have been reported in association with colpocephaly². Colpocephaly has been described in conjunction with Pierre-Robin syndrome⁶.

Associations such as those listed above must be viewed with caution, however, as timing, duration, and quantity of exposure are rarely reported in the literature.

Associated anomalies

In cases not associated with chromosomal aberration, extra-cranial anomalies have included cleft palate and chorioretinal coloboma⁴. Associated intracranial anomalies have included microcephaly, agenesis of the corpus callosum, meningomyelocele⁶, optic nerve atrophy, lissen­ce­phaly⁷, periventricular leuko­mala­cia, enlargement of the cisterna magna and cerebellar hypoplasia⁶.

Prenatal diagnosis

Antenatal diagnosis is made with the demonstration of enlargement of either or both occipital horns of the lateral ventricles. The atria may be enlarged as well. The remainder of the ventricular system should have normal dimensions and configuration. To meet the criteria established by Yakovlev, partial or complete agenesis of the corpus callosum should be noted as well.

Prognosis

A wide range of neuro-developmental outcomes has been reported in the presence of colpocephaly². Perhaps this is because of uncertainty as to the exact etiology of the process.

Of 36 cases reported in the modern literature, 13 patients had seizures. Twelve patients were noted to have mental retardation. Thirteen of 36 cases were affected by mild to severe movement disorders. Other reported outcomes include poor vision, speech and language difficulties, deafness, and chorioretinitis.

Three of the 36 cases reviewed had completely normal neurologic and motor development^2-6.

Management

Antenatal diagnosis of colpocephaly should prompt a search for underlying associations such as karyotypic abnormalities. In addition, maternal exposure to viral or parasitic pathogens should be considered. Finally, maternal ingestion of medication or toxic substances should be evaluated.

In the absence of macrocephaly, there should be no contraindication to vaginal delivery.

References

1. Benda CM: Microcephaly. Am J Psychol 97:1135-46, 1984.

2. Landman J, Weitz R, Dlitzki F, et al.: Radiological colpocephaly: a congenital malformation or the result of intrauterine and perinatal brain damage? Brain Dev 11:313-6, 1989.

3. Yakovlev PI, Wadsworth RC: Schizencephalies: a study of the congenital clefts in the cerebral mantle. I. Clefts with fused lips. J Neuropathol Exp Neurol 5:116-30, 1946.

4. Garg BP: Colpocephaly, an error of morphogenesis? Arch Neurol 39:243-246, 1982.

5. Herskowitz J, Rosman P, Wheeler CB: Colpocephaly: clinical, radiologic, and pathogenetic aspects. Neurology 35:1594-8, 1985.

6. Noorani PA, Bodensteiner JB, Barnes PD: Colpocephaly: frequency and associated findings. J Child Neurol 3:100-104, 1988.

7. Krawinkel M, Steen HJ, Terwey B: Magnetic resonance imaging in lissencephaly. Eur J Pediatr 146:205-208, 1987.

8. Nyberg DA, Pretorius DH: Cerebral malformations. in Nyberg DA, Mahony BS, Pretorius DH (Eds) Diagnostic Ultrasound of Fetal Anomalies. Mosby Year Book, St. Louis, pp83-145, 1990.