Holoprosencephaly

Definition

Holoprosencephaly is a malformation with impaired formation of the forebrain (prosencephalon), in the early stages of fetal development, at the 3rd week of gestation (when there are 3-5 brain vesicles) in which the front brain bubble is not partially or completely divided into two symmetrical hemispheres.

Etiology

Etiological factors are trisomy of the 13th, 15th, 21st pairs of chromosomes, Down syndrome, other chromosomal aberrations, exposure to ionizing radiation. Holoprosencephaly is often found in children whose mothers had severe diabetes.

Morphology

Depending on the severity, 3 types of holoproencephaly are distinguished: alobar, semilobar and lobar. This division is based on the severity of diverticulum disorders.

Alobar holoproencephaly is the most severe form, complete by the fusion of the cerebral hemispheres, characterized by the presence of a monoventricular brain without dividing it into lobes and hemispheres.

Semilobar holoproencephaly - fusion of the frontal lobes with the presence of a slight septum in the back and the presence of a sickle in the interhemispheric fissure, partial separation of the brain with incomplete formation of the lobes. Partially there is an interhemispheric fissure.

Lobar holoprosencephaly - fusion of the frontal lobes with preserved separation of the brain into the left and right hemispheres, as well as the preservation of the lateral ventricles, characterized by the absence of a transparent septum in the presence of formed lobes and interhemispheric fissure. The frontal lobes are not formed; there is an unpaired anterior cerebral artery. This form is often combined with malformations of the eyes (from cyclopia to coloboma).

holoprosencephaly

Fig.2

With cyclopia, the skull is sharply reduced, the nasal primordium is located above the orbit, the optic nerve passes from the eye through the median located optic opening and can be divided into 2 parts, there is no visual cross.

Associated Anomalies

  • hydrocephalus
  • corpus callosum
  • porencephaly
  • Anomalies of the facial skeleton:
    • cyclopia (the only eye socket located in the midline),
    • ethmocephaly (absence of nasal bones, shells, ethmoid septum),
    • cebocephaly (single optic canal, absence of nasal septum and incisal bone)

Clinical picture, treatment and prognosis

Treatment of holoprosencephaly is mainly aimed at eliminating symptoms and prolonging life. Children with a pronounced manifestation of this defect have a short lifespan. When planning a second pregnancy, consult with a geneticist

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Author: radiologist, candidate of medical sciences Vlasov Evgeny Aleksandrovich


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