3Lytic & sclerotic lesions in the skull Lytic lesionsMetast. & M.M.Geographic skull in histiocytosis X.Sclrotic lesionsLocalized sclerosis… metastases
4CT Brain Normal CT Abnormal CT cardinal signs -abnormal tissue density high density…recent hge, calcified and contrast enhancementlow density….neoplasm, infarct, oedema
5Abnormal CT…cont. Mass effect ..compressed or displaced lateral ventriclesMidline shiftDilatation of ventricular system-CT with contrast; CT angio
6MRI of brain Multiplanar capability….extent of tumor. esp. for post. Fossa & craniovertebral junction.Disadvantage; inability to show calcification and bone detailslong scan timedifficulty in monitoring critical patients
10Brain Tumors Glioma Solitary irregular mass surrounded by edema may compress or displace ventricle.usually hypodensemay be hyper or mixed.may calcifymost show partial enhancement.may be ring enhancement.Low in T1 , high in T2
11Metastasesmay be of high or low density.surrounded by edematypically multiplea solitary metast. could not be diff. froma primary neither by CT nor by MRI
12Meningiomaarise from meninges of the vault, falx & tentorium.commonest sites are parasagittal region over the cerebral convexities & sphenoid ridge.Slightly hyperdense on native CTmarked enhancementAcoustic neuroma; in the CPA near IAM.
14Cerebral infarction & hemorrhage Clinically similarCT is the initial exam.Hge….high density surrounded by edema.May be SAH or intraventricular.In Infarction ….CT normal initially.MRI diffusion Weighted Images.
15SAH usually due to rupture aneurysm. CT is the best initial exam.The large aneurysms are seen by CT.MRA can show smaller aneurysms.Arteriography is the best.AVM may present with Hge….CT can show the AVM esp. with contrast.But MRI is better even without contrast.
17Head Injury:Fractures# more translucent# may branch abruptlySuture in known anatomical positions.Depressed #....dense.EDH can result from # through MMA groove.
18CT in head injury CT should be done when there is: -deterioration in the conscious level.-worsening of neurological deficits.Extracerebral lesions-EDH.. biconvex. Associated with #High density for 2Wks.After 3-4Wks…..hypodenseIsodense in between.-SDH…….concavoconvex
19Fractures of the base & vault are easily seen in bone windowIntracerbral lesions:-Edema- homogenous low density.-Contusions- patchy low density areas-Intracerebral hematomaSevere head injury can exist with no abnormal CT