IMAGING MODALITIES Computerized Tomography Magnetic Resonance Imaging Advantages

IMAGING MODALITIES • Computerized Tomography • Magnetic Resonance Imaging

Advantages of C. T • Detection of calcification and calvarial defects • No contraindication

Disadvantages of CT • Use of ionizing radiation • Reaction to iodinated contrast • Nephrotoxicity

Advantages of MRI • No radiation • Excellent soft tissue resolution • Multiplanar imaging

Limitations of MRI • Hyperacute bleed • Evaluation of calcification

Contraindications for MRI • Cochlear implants • Cardiac pace maker • Neuro stimulator

Lissencephaly • Most severe of neuronal migrational abnormalities • Generalized paucity of gyral and sulcal formation • Vertically oriented sylvian fissures

Torch Infections • Toxoplasmosis • Rubella • Cytomegalovirus - Most common cause of congenital CNS infection • Herpes simplex virus

Focal cortical dysplasia • Common location – temporal lobes • Expanded gyrus with abnormally oriented sulci and thickened cortex • Subcortical white matter hyperintensity • Surgical excision of dysplastic focus when possible is often curative

Cortical dysplasia – Balloon Cell Type of Taylor • Focal cortical thickening • Blurring of the gray-white matter junction • Hyperintensity (on T 2 -weighted images) of subcortical white matter often tapering toward the ventricle

Unilateral megalencephaly • Hamartomatous overgrowth of a part or whole of cerebral hemisphere • Ipsilateral migrational defects • Hypoplastic / hyperplastic white matter • Intractable seizures, hemiplegia and severe developmental delay

Peri-Sylvian syndrome • Anomalous cortical development overlying underdeveloped sylvian fissures • Dorsal perirolandic extension of sylvian fissures

Septo-optic dysplasia (de Morsier syndrome) • Partial or complete absence of septum pellucidum • Squared off appearance of frontal horns • Hypoplasia of optic nerves and chiasm ( 40 -80%) • Hypoplasia of hypothalamus

Tuberous sclerosis (Bourneville disease) • Incidence -- 1: 10, 000 -50, 000 • Inheritance -- autosomal dominant -- low penetrance -- chromosomes: 9, q 32 - 34; 11, ? ?

Tuberous sclerosis Clinical - “classic” triad of: > Papular facial lesions > seizures > mental retardation- 50% of patients

Tuberous sclerosis • CNS lesions - Subependymal nodules - Giant cell astrocytoma - Cortical tubers - White matter lesions • Non- CNS lesions - Skin, kidneys, cardiovascular, Liver, spleen, pancreas and Musculoskeletal

Sturge-weber syndrome (Encephalotrigeminal angiomatosis) • Inheritance : none • Clinical : port wine stain in CN - V distribution

Sturge-weber syndrome • Aetiology - Normal cortical venous drainage fails to develop • Pathology - Leptomeningeal angiomatous vascular plexus with secondary dystrophic cortical changes

Sturge-weber syndrome • Calcification • Atrophy • Enlarged med, sub-epen veins • Ocular lesions

Periventricular leukomalacia • Commonly seen in premature infants • Ischemic lesions are most obvious in parieto-occipital regions • Paucity of white matter in the parietooccipital regions • Indentation of the lateral ventricles

Hippocampus Mean volumes: Right Left Male - 2. 20+0. 47 cu. cm 2. 17+0. 72 cu. cm Female- 2. 27+0. 47 cu. cm 2. 23+0. 48 cu. cm Hippocampal sclerosis: 1. 46+0. 60 cu. cm

Hippocampus Normal: NAA/Cho: 1. 20 + 0. 27 Hippocampal sclerosis: NAA/Cho: 0. 99 + 0. 14

Hippocampus T 2 Relaxometry Mean T 2 time: 110 -115 ms Prolonged in Hippocampal sclerosis

Dysembryoplastic Neuroepithelial Tumor • Slow growing superficial lesions usually within temporal lobe but always supratentorial • Focal cortical lesion , hypointense on T 1 & hyperintense on T 2 Wt. images • Surgery is curative