Baby with fused eyes and single nasal chamber, undeveloped callosum. What is diagnosis?
Correct Answer: Holoprosencephaly
Description: A i.e. HoloprosencephalyRef: Nelson, Textbook of Pediatrics, 20th edition, page 2640Explanation:HoloprosencephalyDisorder of neuronal migration with defective cleavage of the prosencephalon (the forebrain of the embryo fails to develop into two hemispheres) and inadequate induction of the forebrain structures.Cause - Mutations in the "sonic hedgehog" gene at 7q, maternal diabetes.Three groups:Alobar-Severe facial anomalies, including lack of a nose and the eyes merged to a single median structure, e.g. cyclopia.Semilobar-lntermediate form.Lobar-Least severe formMiddle interhemispheric fusion (MIHF variant) or syntelencephaly - involves a segmental area of non-cleavage of the posterior frontal and parietal lobes.Facial abnormalities - Cyclopia (fused eyes and single nasal chamber), cebocephaly, single central incisor tooth, premaxillary agenesis and anosmia.A prenatal diagnosis - ultrasonography after the 10th week of gestation for more severe types.Other disorder of neural migration:DisorderPathologyClinical featuresLISSENCEPHALY/AGYRIA* Absence of cerebral convolutions, poorly formed sylvian fissure, giving the appearance of a 3-4 months fetal brain* Associated with enlarged lateral ventricles and heterotopias in the white matterPresents with failure to thrive, microcephaly, marked developmental delay, and a severe seizure disorder, hypoplasia of the optic nerve and microphthalmia associated withMiller-Dieker Syndrome (MDS)* Gene LIS-1 (lissencephaly 1) that maps to chromosome region 17p13.3 is deleted* Prominent forehead, bitemporal hollowing, anteverted nostrils, a prominent upper lip, and micrognathia* CT and MRI scans typically show a smooth brain with an absence of sulciSCHIZENCEPHALYPresence of unilateral or bilateral clefts within the cerebral hemispheres* Mental retardation, refractory seizures and microcephaly* Unilateral schizencephaly is a frequent cause of congenital hemiparesis* With spastic quadriparesis when the clefts are bilateral* CT scan is diagnostic and clearly demonstrates the size and extent of the cleftPORENCEPHALYPresence of cysts - in sylvian fissure and typically communicate with the subarachnoid space, the ventricular system, or both, associated with microcephaly, abnormal patterns of adjacent gyri, and ence- phaloceleMental retardation, spastic hemi- or quadriparesis, optic atrophy and seizures.Pseudoporencephalic cysts* Perinatal or postnatal period and result from abnormalities (infarction, hemorrhage) of arterial or venous circulation* Cysts extend to be unilateral* They do not communicate with a fluid-filled cavity; and* They are not associated with abnormalities of cell migration or CNS malformations* Present with hemiparesis and focal seizures in the 1st year of life
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