Colpocephaly is a cephalic disorder involving the disproportionate enlargement of the occipital horns of the lateral ventricles and is usually diagnosed early after birth due to seizures.

It is a nonspecific finding and is associated with multiple neurological syndromes, including agenesis of the corpus callosum, Chiari malformation, lissencephaly, and microcephaly.

During the seventh week of gestation, neurons start proliferating in the germinal matrix which is located in the subependymal layer of the walls of the lateral ventricles.

During the eighth week of gestation, the neurons then start migrating from the germinal zone to cortex along specialized radial glial fibers.

The partial or complete absence of white matter, also known as agenesis of the corpus callosum results in anatomic malformations that can lead to colpocephaly.

Myelination of the ventricular walls and association fibers of the corpus callosum and the calcarine fissure helps shape the occipital horns.

The authors suggest a genetic origin with an autosomal or X-linked recessive inheritance rather than resulting from early prenatal disturbances.

The corpus callosum plays an extremely important role in interhemispheric communication, thus lack of or absence of these neural fibers results in a number of disabilities.

[12] The lemon sign on CT scans of patients refers to the shape of the fetal skull when the frontal bones lose their normal convex contour and appear flattened or inwardly scalloped.

Physicians look for abnormally large occipital horns of the lateral ventricles and diminished thickness of white matter.

[12] Spinal tapping is not a preferred method for diagnosis because newborn babies with colpocephaly or hydrocephaly have open fontanelles which makes it difficult to collect CSF.

Similar symptoms (absence of corpus callosum and increased head circumference) were noted as in the case of colpocephaly that is associated with microcephaly.

[14][15] It was suggested that the enlargement of ventricles occurred as a result of white matter development arrest during early fetal life.

[4] They 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 brain."

He suggested the term 'hydrocephalus ex vauco' to be used for enlargement of the occipital horns of the lateral ventricles as a result of damage to the brain after it is normally formed.