<prompt> Baby with fused eyes and single nasal chamber, undeveloped callosum. What is diagnosis?HoloprosencephalySchizencephalyPlagiocephalyBrachycephaly  <response>: 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 featuresLISSENCEPHALYAGYRIA 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 