Skull & BrainSkull & BrainImaging TechniquesImaging Techniques

Plain……..trauma Plain……..trauma

CT & MRI …standard investig.CT & MRI …standard investig.

USUS

Angiography….Limited to Angiography….Limited to stenosis. stenosis.

aneurysm & aneurysm & AVMAVM

Imaging TechniquesImaging Techniques

Plain ….Plain …. Normal….inner & outer tables (compact)Normal….inner & outer tables (compact) Diploic space ( spongy bone )Diploic space ( spongy bone ) Sutures remain visible even Sutures remain visible even after fusion. after fusion. Metopic suture. InconstantMetopic suture. Inconstant vascular impressionsvascular impressions arachnoid granulationsarachnoid granulations position of calc. pineal body.position of calc. pineal body.

Plain film…..cont.Plain film…..cont.

Abnormal plain films; look forAbnormal plain films; look for

-intra-cranial calcifications -intra-cranial calcifications

-pit. fossa…..pit. tumors-pit. fossa…..pit. tumors

-bones for lytic, sclerotic, #-bones for lytic, sclerotic, #

-calcifications & signs of raised ICP -calcifications & signs of raised ICP are are

import. signs in the plain films.import. signs in the plain films.

Intracranial calcificationsIntracranial calcifications

Most intra-cranial calcif. is normal & of no Most intra-cranial calcif. is normal & of no significance.significance.

Normal intra-cranial calcifications:Normal intra-cranial calcifications: pineal, choroid, interclinoid, petroclinoid, pineal, choroid, interclinoid, petroclinoid,

falx, atheromatous calcification in carotid.falx, atheromatous calcification in carotid.

pathological calcifications:pathological calcifications: primary tumors, meningioma, glioma, primary tumors, meningioma, glioma,

craniopharyngioma, AVM , aneurysm & craniopharyngioma, AVM , aneurysm & old abscess.old abscess.

Raised ICP Raised ICP

Plain film abnormality in prolonged Plain film abnormality in prolonged cases.cases.

Sutural diastasis.Sutural diastasis.Destruction of dorsum sellae.Destruction of dorsum sellae.

Lytic & sclerotic lesions in the Lytic & sclerotic lesions in the skullskull

Lytic lesionsLytic lesions Metast. & M.M.Metast. & M.M. Geographic skull in histiocytosis X.Geographic skull in histiocytosis X. Osteoporosis circumscripta …paget’sOsteoporosis circumscripta …paget’s

Sclrotic lesionsSclrotic lesions Hyperostosis frontalis interna….commonest cause Hyperostosis frontalis interna….commonest cause Localized sclerosis…St. mixed with lytic inLocalized sclerosis…St. mixed with lytic in meningioma, metastases, fibrous dysplasiameningioma, metastases, fibrous dysplasia Paget’s ……cotton-wool app. (thickening of Paget’s ……cotton-wool app. (thickening of

calvarum)calvarum)

CT BrainCT Brain

Normal CT Normal CT Abnormal CT cardinal signsAbnormal CT cardinal signs

-abnormal tissue density-abnormal tissue density

high density…recent hge, calcified high density…recent hge, calcified and contrast enhancementand contrast enhancement

low density….neoplasm, infarct, low density….neoplasm, infarct, oedema (surrounding neoplasm, oedema (surrounding neoplasm, infarcts, hge, inflammation) infarcts, hge, inflammation)

Abnormal CT…cont.Abnormal CT…cont.

Mass effect ..compressed or displacedMass effect ..compressed or displaced lateral ventricleslateral ventricles Midline shiftMidline shift

Dilatation of ventricular systemDilatation of ventricular system Obst. to CSF flow within the system ( non-Obst. to CSF flow within the system ( non-

communicating)communicating) Obst. over the surface of brain Obst. over the surface of brain

(communicating)(communicating) Secondary to brain atrophySecondary to brain atrophy -CT with contrast-CT with contrast

MRI of brainMRI of brain

Multiplanar capability….extent of Multiplanar capability….extent of tumor.tumor.

esp. for post. Fossa & craniovertebral esp. for post. Fossa & craniovertebral junction.junction.

Disadvantage; inability to show Disadvantage; inability to show calcification and bone details calcification and bone details

long scan timelong scan time

difficulty in monitoring critical patientsdifficulty in monitoring critical patients

MRI BrainMRI Brain

ContrastContrast

GadoliniumGadolinium

MRA severe stenosis & aneurysmMRA severe stenosis & aneurysm

MRVMRV

MRI BrainMRI Brain

It is more often possible to make a It is more often possible to make a specific diagnosis with MRI than CT.specific diagnosis with MRI than CT.

Demyelinating plaques of MSDemyelinating plaques of MSAVMAVM

NeurosonographyNeurosonography

HydrocephalusHydrocephalusHemorrhageHemorrhageCongenital abnormalities.Congenital abnormalities.

Brain TumorsBrain Tumors GliomaGlioma

Solitary irregular massSolitary irregular mass

surrounded by edemasurrounded by edema

may compress or displace ventricle.may compress or displace ventricle.

usually hypodense usually hypodense

may be hyper or mixed.may be hyper or mixed.

may calcifymay calcify

most show partial enhancement.most show partial enhancement.

may be ring enhancement.may be ring enhancement.

Low in T1 , high in T2Low in T1 , high in T2

MetastasesMetastases

may be of high or low density.may be of high or low density.

surrounded by edemasurrounded by edema

typically multiple typically multiple

a solitary metast. could not be diff. a solitary metast. could not be diff. fromfrom

a primary neither by CT nor by MRIa primary neither by CT nor by MRI

MeningiomaMeningioma arise from meninges of the vault, falx & arise from meninges of the vault, falx &

tentorium.tentorium. commonest sites are parasagittal commonest sites are parasagittal

region over the cerebral convexities & region over the cerebral convexities & sphenoid ridge.sphenoid ridge.

Slightly hyperdense on native CTSlightly hyperdense on native CT marked enhancementmarked enhancement Sclerosis & thickening of adjacent bone.Sclerosis & thickening of adjacent bone.

Acoustic neuroma;Acoustic neuroma; in the CPA near IAM. in the CPA near IAM.

Pit. Tumors:Pit. Tumors:

microadenoma < 10mmmicroadenoma < 10mm

macroadenoma.> 10mmmacroadenoma.> 10mm

endocrine active 80%endocrine active 80%

endocrine inactive. 20%endocrine inactive. 20%

Gd is better for demost. Gd is better for demost. microadenomasmicroadenomas

Cerebral infarction & hemorrhageCerebral infarction & hemorrhage

Clinically similarClinically similar

CT is the initial exam.CT is the initial exam.

Hge….high density surrounded by Hge….high density surrounded by edema.edema.

May be SAH or intraventricular.May be SAH or intraventricular.

In Infarction ….CT normal initially.In Infarction ….CT normal initially.

MRI diffusion Weighted Images.MRI diffusion Weighted Images.

SAH SAH usually due to rupture usually due to rupture aneurysm.aneurysm.

CT is the best initial exam.CT is the best initial exam.

The large aneurysms are seen by CT.The large aneurysms are seen by CT.

MRA can show smaller aneurysms.MRA can show smaller aneurysms.

Arteriography is the best.Arteriography is the best.

AVMAVM may present with Hge….CT can may present with Hge….CT can show the AVM esp. with contrast.show the AVM esp. with contrast.

But MRI is better even without But MRI is better even without contrast.contrast.

AbscessAbscess

Low density with ring enhancementLow density with ring enhancement

Herpes encephalitisHerpes encephalitis

enhancing low density areas in the enhancing low density areas in the

temporal lobes.temporal lobes.

Head Injury:Head Injury:FracturesFractures# more translucent# more translucent# may branch abruptly# may branch abruptly# have straight or jagged edge that fit # have straight or jagged edge that fit

together. While venous channels have together. While venous channels have undulating irregular edges which cannot undulating irregular edges which cannot be fitted together.be fitted together.

Arterial grooves have parallel sides (more Arterial grooves have parallel sides (more easily confused with #)..but present in easily confused with #)..but present in known anatomical positions.known anatomical positions.

Suture in known anatomical positions & Suture in known anatomical positions & show regular interdigitations. Widening of show regular interdigitations. Widening of a suture has the same significance as a #a suture has the same significance as a #

Depressed #....denseDepressed #....denseEDH can result from # through MMA groove.EDH can result from # through MMA groove.

CT in head injuryCT in head injuryCT should be done when there is:CT should be done when there is:-deterioration in the conscious level.-deterioration in the conscious level.-worsening of neurological deficits.-worsening of neurological deficits.

Extracerebral lesionsExtracerebral lesions-EDH.. -EDH.. biconvex. Associated with #biconvex. Associated with # High density for 2Wks.High density for 2Wks.After 3-4Wks…..hypodenseAfter 3-4Wks…..hypodenseIsodense in between. Isodense in between.

-SDH-SDH…….concavoconvex…….concavoconvex

Fractures of the base & vault are easily Fractures of the base & vault are easily seen in bone windowseen in bone window

Intracerbral lesions:Intracerbral lesions:-Edema- -Edema- homogenous low density.homogenous low density.-Contusions- -Contusions- patchy low density areaspatchy low density areas-Intracerebral hematoma-Intracerebral hematoma

Severe head injury can exist with no Severe head injury can exist with no abnormal CTabnormal CT