Indian Journal of Radiology and Imaging Indian Journal of Radiology and Imaging

: 2003  |  Volume : 13  |  Issue : 3  |  Page : 327--328

Radiological quiz - neuroradiology

S Krishan, U Hemal 
 Dept of Radiodiagnosis, Lady Hardinge Medical College and ass. Hospital New Delhi-110001, India

Correspondence Address:
S Krishan
C/o Mr.Pradeep Krishan, B-206, Him Hit CGHS, Plot No.8, Sector 22, Dwarks, New Delhi-110045

How to cite this article:
Krishan S, Hemal U. Radiological quiz - neuroradiology.Indian J Radiol Imaging 2003;13:327-328

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Krishan S, Hemal U. Radiological quiz - neuroradiology. Indian J Radiol Imaging [serial online] 2003 [cited 2021 Jan 23 ];13:327-328
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Full Text

A 2 year old male child presented with delayed milestones,recurrent generalized seizures. On examination child had microcephaly,diplegia and severe mental retardation.The patient was subjected to plain followed by contrast enhanced CT of the head. [Figure 1] at the level of body of lateral ventricle.

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 Radiological Diagnosis



Contrast enhanced CT scan of head reveals absent sulci with smooth cortical surface,Sylvian fissures are straight oblique resulting in a figure of eight appeareance of brain.There is also evidence of colpocephaly.

Lissencephaly or smooth brain refers to paucity of gyral and sulcal development on the surface of brain.[1] It is a severe form of agyria pachygyria group of disorders of neuronal migration.[2] The neuronal population of normal cerebral cortex arrives by a process of outward migration from periventricular germinal matrix between the eighth and sixteenth week of gestation.[3] This complex process of cell migration can be interfered with by many causes sporadic, unknown,chromosomal or genetic and intrauterine infections.[4] Smooth brain is however physiological at 16-17 weeks of intrauterine life.

This condition is best imaged by MRI but CT is also effective in many cases.[3][4][5][6][7] Agyria is described as absence of gyri on the surface of brain synonymous with complete lissencephaly while pachygyria is defined as few broad flat gyri.[3] Focal pachygyria may be cause of focal epilepsy .Polymicrogyria may coexixt with pachgyria.[4],[5] In polymicrogyria neurons reach the cortex but are distributed abnormally. Localized abnormalities are more common than generalized and often involve arterial territories specially the middle crebral artery.The most common location is around sylvian fissure.

Lissencephaly is of three types:

In type I or classical lissencenpaly children always have global developmental delay and seizures although the age of onset and severity of symptoms may vary.[4][5][6][7][8] Some patients have chromosome 17 or X chromosome defect. Children with complete lissencephaly are hypotonic at birth with gradually developing spasticity. Medically refractive epilepsy with increasing complex seizure disorder over time is characteristic. Systemic abnormalities of the eyes, ears, heart, kidney and severe mental retardation are also present.[5][6][7][8] Some infants have specific dysmorphic features Miller Dieker syndrome, and Norman Roberts syndrome.[6][7][8] On imaging there is small brain, colpocephaly i.e. dilated ventricular trigone and occipital horns, a thickened cortex with broad flat gyri, diminished white matter ,smooth white -grey matter interface and straight oblique or shallow sylvian fissures giving a figure of eight appearance.[4][5][6][7][8] Parenchymal calcifications can be present if lissencephaly is due to intrauterine infections.[5],[6]There may be corpus callosal agenesis . Small brainstem may be seen due to maldevelopment of corticospinal and corticobulbar tracts.Our case fitted into type I lissencephaly.[6][7][8]

Type two or cobblestone lissencephaly results from overmigration of neurons.[4][5][6][7][8] These patients suffer from associated muscular dystrophy, hypotonia, myelination delay, hydrocephalus and ocular abnormalities. There is agyric severely disorganized unlayered thick cortex with poor and irregular corticomedullary demarcation.[4][5][6][7][8] On MRI cortex is thick with polymicrogyria, hypomyelination, hydrocephalus, microophthalmia and callosal hypogenesis.[4][5][6][7][8] The abnormality may be focal, seen in the frontal or temporooccipital cortex.[4][5][6][7][8]

In type III lissencephaly MR shows microcephaly, thick cortex, enlarged ventricles and hypoplastic braistem and cerebellum.[3],[6],[7]There may be vermian hypogenesis with cerebellar polymicrogyria. Dysplasia of the crebellar cortex manifests as dysplastic folia with subcortical cysts located predominantly in the dorsal portion of the cerebellar hemisphere.[3],[6][7][8] Myelination is often delayed.[6]


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