DIAGNOSTIC TESTSMost neuroradiologic examinations of the central nervous system (CNS) consist of computed tomography (CT), mag-netic resonance imaging (MRI), magnetic resonance angiog-raphy (MRA), and single-photon emission computed tomog-raphy (SPECT). Figure 341 shows normal contrast-enhanced CT anatomy. Figure 342 shows a normal MRI brain scan. MRI is more sensitive than CT for detection of neoplasms (Fig. 343). Small infarcts are also more easily visualized by MRI, especially if they are located in the cerebellum (Fig. 344) or brainstem. With diffusion-weighted imaging (DWI), ischemic lesions can be demonstrated early. DWI is based on

the examination of free water movement. Restricted free water movement is detected early, paralleling the development of cytotoxic edema. The imaging sequences used are fast and not as easily disturbed by inappropriate patient movement. A normal SPECT scan is shown in Figure 345. SPECT scanning can be used for evaluating neoplasms (Fig. 346) and demen-tia (Fig. 347).

Imaging of precerebral and cerebral vesselsDuplex sonography allows for the evaluation of vessel anatomy, along with measurement of the direction and velocity of blood ow. The degree of stenosis is calculated from the blood ow

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Chapter 34 Diagnostic tests and procedures

A B C

D E F

tp

tns

aw

cs

cq

P baba

tca

i

mc

t

sfac ac

cspmc

lgbcpdpc

fh

fm

ec

c

c

cc

sp

cv

sttr

sf

o

bvcv

f

f

llcth

st

ss

cp

3

pgV

Fig 341Normal contrast-enhanced CT anatomy. Figures A through F show normal CT scans at various levels in the brain. 3, 4, third and fourth ventricles; ac, anterior cerebral artery; ba, basilar artery; bv, body of lateral ventricle; c, caudate nucleus; cc, corpus callosum (genu); cp, cerebral peduncle; csp, cave of septum pellucidum; cv, internal cerebral vein; f, falx; fh, frontal horn of lateral ventricle; fm, foramen of Monro; i, infundibulum of pitu-itary; mc, middle cerebral artery; o, white matter tracts; p, pons; pc, posterior cerebral artery; pg, pineal gland; sf, sylvian ssure; sp, septum between lateral ventricles; th, thalamus; tp, temporal horn; tr, trigone of lateral ventricle.(From Grainger RG, Allison DJ, Adam A, Dixon AK [eds]: Grainger and Allisons Diagnostic Radiology: A Textbook of Medical Imaging, 4th ed. London. Harcourt, 2001.)

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Chapter 34: Diagnostic tests and procedures 34

cc

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Fig 342Normal MRI. A, T2-weighted sagittal images through the midline. B, Corneal T2-weighted images through the hippocampi. C, Coronal T1-weighted images through the level of the third ventricle. 3,4, third and fourth ventricles; a, amygdala; aca, anterior cerebral artery; ba, basilar ar-tery; cc, corpus callosum; cf, calcarine ssure; ch, cerebellar hemisphere; cn, caudate nucleus; cs, central sulcus; ec, external capsule; fh, frontal horn; fh, frontal lobe; fm, foramen of Munro; gf, gyrus fusiformis; gp, globus pallidus; h, hippocampus; mca, middle cerebral artery; oc, optic chi-asm; oh, occipital horn; p, pons; pg, parahippocampal gyrus; pm, putamen; pof, parieto-occipital ssure; pvs, perivascular spaces; sf, sylvian s-sure; t, tectal plate; th, temporal horn; tha, thalamus; tl, temporal lobe.(From Grainger RG, Allison DJ, Adam A, Dixon AK [eds]: Grainger and Allisons Diagnostic Radiology: A Textbook of Medical Imaging, 4th ed. London. Harcourt, 2001.)

A B

C D

Fig 343Oligodendroglioma. A, CT after intravenous contrast medium shows a large left frontal tumor that involves the cortex. It is predominantly solid with irregular en-hancement, but there are also cysts and coarse cal-ci cation. B, Follow-up after 2 years with CT. T2-weighted MRI (C) and T1-weighted postcontrast MRI (D) show more extensive cyst formation and cal-ci cation than on the rst scan. The calci cation is much less apparent on MRI and appears as nonspe-ci c low signal areas. Posterior in ltration of the tu-mor is, however, best seen on MRI (C). Note that the patient had undergone a left frontal craniotomy after the rst scan.(From Grainger RG, Allison DJ, Adam A, Dixon AK [eds]: Grainger and Allisons Diagnostic Radiology: A Textbook of Medical Imaging, 4th ed. London. Harcourt, 2001.)

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A B CFig 344Top of the basilar syndrome. T2-weighted MRI show multiple infarcts in the basilar and posterior cerebral artery territories including the left thalamus (A), both occipital lobes (B) and cerebellar hemispheres (C). Note the absence of ow void in the distal basilar artery in B (arrow).(From Grainger RG, Allison DJ, Adam A, Dixon AK [eds]: Grainger and Allisons Diagnostic Radiology: A Textbook of Medical Imaging, 4th ed. London. Harcourt, 2001.)

Fig 34599mTcHMPAO single-photon emission computed tomography scan of the brain: axial (left) and sagittal (right) images. A, anterior; R, right; L, left; P, posterior.(From Grainger RG, Allison DJ, Adam A, Dixon AK [eds]: Grainger and Allisons Diagnostic Radiology: A Textbook of Medical Imaging, 4th ed. London. Harcourt, 2001.)

Fig 346201Tl single-photon emission computed tomography scan in a 40-year-old man with a left frontotemporal mass on MRI. This reveals the high uptake typical of high-grade glioma, which was con rmed on biopsy to be a glioblastoma.(Courtesy of Professor Donald M. Hadley, Glasgow.)

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A B

C D

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Fig 347Single-photon emission computed tomography scans of normal subject (A); patient with Alzheimers disease showing bilateral parietal lobe abnor-malities more marked on the right side (B); patient with frontotemporal dementia, showing bilateral frontal lobe abnormalities (C); patient with pro-gressive supranuclear palsy, showing bilateral anterior abnormalities (D); patient with corticobasal degeneration, showing asymmetrical right fronto-parietal abnormality (E); patient with Creutzfeldt-Jakob disease, showing multifocal cortical abnormalities (F).(From Tallis R, Fillit H: Brockelhurstss Textbook of Geriatric Medicine and Gerontology, 6th ed. London, Churchill Livingstone, 2003.)

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A B CFig 348Imaging of precerebral and cerebral vessels. A, Color-coded Doppler sonography of the internal carotid artery close to the bifurcation in a patient with pronounced atherosclerotic changes and stenosis causing slowing of blood ow and turbulence (green and blue signals). B, Contrast-enhanced magnetic resonance angiography showing a tight stenosis of the internal carotid artery (arrow). C, Conventional angiography showing a very tight stenosis of the internal carotid artery (arrow).(From Crawford, MH, DiMarco JP, Paulus WJ [eds]: Cardiology, 2nd ed. St. Louis, Mosby, 2004.)

Anteriorcommunicating

artery

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artery

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Fig 349Magnetic resonance angiogram showing the arterial supply to the brain.(From Crawford, MH, DiMarco JP, Paulus WJ [eds]: Cardiology, 2nd ed. St. Louis, Mosby, 2004.)

velocity. Color-coded Doppler signals help visualize the direc-tion of blood ow (Fig. 348 )

Conventional angiography (see Fig. 348C) allows good visualization of the aortic arch and the origins of the neck arter-ies but has a potential risk of nephrotoxicity, allergic reactions, and thromboembolism.

MRA (Fig. 349) is useful for detection of carotid artery stenosis (see Fig. 348B) and suspected carotid or vertebral ar-tery dissection. MRA is also useful for evaluating the aortic arch (Fig. 3410) and the intracranial circulation (Fig. 3411).ELECTROENCEPHALOGRAPHYElectroencephalography (EEG) is a measure of the electrical activity generated by the central nervous system. It is useful to document abnormalities of the brain that are not associated with detectable structural alterations in brain tissue. It also pro-vides a continuous measure of cerebral function over time. Electroencephalographic signals are generated by the cerebral cortex. Different parts of the cortex generate distinct uctua-tions. The uctuations also differ with eye opening and in the sleep and waking states. Figure 3412 shows an electroencepha-logram of a normal subject; an electroencephalogram of a brain-dead patient is shown in Figure 3413.

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Chapter 34: Diagnostic tests and procedures 34

Fig 3410Contrast-enhanced MRA of aortic arch. A three-dimensional gradient-echo sequence has been acquired during the rst pass of an intrave-nously injected gadolinium bolus. It shows the origins of the great ves-sels. Note also that there is background opaci cation of the pulmonary vessels.(From Grainger RG, Allison DJ, Adam A, Dixon AK [eds]: Grainger and Allisons Diagnostic Radiology: A Textbook of Medical Imaging, 4th ed. London. Harcourt, 2001.)

ACCM

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Fig 3411Three-dimensional TOF MRA of the intracranial circulation, axially col-lapsed maximum intensity projection. A1, precommunicating segment of anterior cerebral artery; ACOM, anterior communicating artery; BA, basilar artery; CS, carotid siphon; M1, rst (horizontal) segment of mid-dle cerebral artery; M2, M2 segments of middle cerebral artery; P1, precommunicating segment of posterior cerebral artery; P2, P2 seg-ment of posterior cerebral artery; PCOM, posterior communicating artery; petr CA, petrous segment of internal carotid artery.(From Grainger RG, Allison DJ, Adam A, Dixon AK [eds]: Grainger and Allisons Diagnostic Radiology: A Textbook of Medical Imaging, 4th ed. London. Harcourt, 2001.)

Eyesopen

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Fig 3412A posteriorly predominant 9-Hz alpha rhythm is present when the eyes are closed and is attenuated by eye opening in the electroencephalo-gram of this normal subject. Electrode placements in this and Figure 34-13 are as follows. A, earlobe; C, central; F, frontal; Fp, frontopolar; O, occipital; P, parietal; Sp, sphenoid; T, temporal. Right-sided place-ments are indicated by even numbers and left-sided placements by odd numbers.(From Goetz CG, Pappert EJ: Textbook of Clinical Neurology, Philadelphia, WB Saunders, 1999)

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Fig 3413Electrocerebral silence in the electroencephalogram of a brain-dead patient following attempted resuscitation after cardiopulmonary arrest. See Figure 34-12 for electrode placements.(From Goetz CG, Pappert EJ: Textbook of Clinical Neurology. Philadelphia, WB Saunders, 1999.)

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