Acute Bacterial Meningitis
In uncomplicated cases of purulent
meningitis, early CT scans and MRIs
usually demonstrate normal findings or
small ventricles and effacement of sulci.
This axial nonenhanced
scan shows mild
Acute bacterial meningitis.
This axial T2-weighted
magnetic resonance image
shows only mild
This contrastenhanced, axial T1weighted magnetic
resonance image shows
Viral Meningitis and
• The diagnosis is made clinically and imaging
has no contribution.
Brain imaging is frequently normal in viral encephalitis. Occasionally, nonspecific changes consist
of either sulcal effacement (H) (thin arrow), compared with normal sulcal spaces (thick arrow); or
increased signal (I) (arrow), reflecting increased water content in the mildly swollen brain of the
These changes developed in a patient with probable enterovirus encephalitis but can be produced
by many viruses, as well as after head injury and in various metabolic encephalopathies.
Herpes simplex virus encephalitis
. Abnormal signal and edema in the left temporal lobe (short bottom arrow), insula
(long arrow) and cingulate gyrus (arrowhead), sparing deep nuclear structures with
mass effect compressing the left lateral ventricle and uncal herniation; also not
increased signal in the right inferomedial temporal lobe (short bottom arrow) and
insular cortex (long arrow).
Cytomegalovirus encephalitis. Characteristic enhancement in
ependyma around lateral ventricles
Togavirus (Japanese Encephalitis)
Deep-seated structures characteristically involved: subcortical white matter
(top arrow), thalami (middle arrow), and substantia nigra (bottom arrow)
HIV infection of CNS
• Characteristic abnormalities are brain atrophy and diffuse
white matter attenuation
JCV infection- PMLE
Progressive Multifocal Leuco Encephalopathy
Typical multifocal and confluent subcortical nonenhancing white matter hyperintensities extending
to the cortical gray matter
Acute disseminated or post infectious
encephalomyelitis after virus infection
Subcortical white matter lesions (short arrow) involving subcortical U fibers with
tangential lesions (long arrow).
Varicella zoster virus vasculopathy.
Ischemia/infarction more common in white matter (top arrow), particularly at
gray-white matter junctions (short arrow), less frequently in gray matter
(long arrow) and may enhance
Subdual And epidural Empyemas.
• Empyema is a "closed space infection" occurring inside a
body cavity or space
Epidural Empyema CT
Subdural Empyema CT
Axial T1WI shows
fluid collection along the
convexity (small arrows)
with minimal air-fluid
The right subdural
fluid collection is
axial T2WI (arrows).
T1WI shows ring
enhancement of the
right subdural fluid
weighted images shows
increased signal of the
right subdural fluid
collection (arrow) with
low apparent diffusion
A brain abscess is a focal, suppurative infection within the brain
parenchyma, typically surrounded by a vascularized capsule.
MRI is better than CT for demonstrating abscesses in the early (cerebritis)
stages and is superior to CT for identifying abscesses in the posterior
On contrast-enhanced T1-weighted MRI, a mature brain abscess has a
capsule that enhances surrounding a hypo dense center and surrounded
by a hypo dense area of edema.
On T2-weighted MRI, there is a hyper intense central area of pus
surrounded by a well-defined hypo intense capsule and a hyper intense
surrounding area of edema.
The distinction between a brain abscess and other focal CNS lesions such
as primary or metastatic tumors may be facilitated by the use of diffusionweighted imaging sequences on which brain abscesses typically show
increased signal and low apparent diffusion coefficient.
Brain Abscess CT and MRI
Intra-axial mass, located in the posterior left
frontal lobe, in the superior frontal gyrus just
anterior to the precentral gyrus. There is
surrounding vasogenic edema, which expands
the left precentral gyrus. Mass shows a welldefined rim on MR, somewhat
irregular, consistent with a capsule. Central
portion shows pronounced diffusion
Brain : poorly
defined hypodense and
area of cerebritis in the
right parietal lobe.
Multiple areas of
On T2-weighted MRI
image (TR/TE2500/90) T1-weighted image
the lesion is
20/2.1/35°) shows no g development of
tomography (CT) scan in a
patient with tuberculous
marked enhancement in the
basal cistern and
meninges, with dilatation of
tomography (CT) scan of a child
with tuberculous meningitis
hydrocephalus and meningeal
MRI is more sensitive than CT scanning in determining the
extent of meningeal and parenchymal involvement
resonance image of a biopsyproven, right parietal
tuberculoma. Note the low–
signal-intensity rim of the
lesion and the surrounding
T1-weighted gadoliniumenhanced magnetic
resonance image in a
patient with multiple
in both cerebellar
image in a child with a
tuberculous abscess in
the left parietal region.
Note the enhancing
T1-weighted gadolinium-enhanced magnetic
resonance image of the thoracic spinal cord in a
patient with acquired immunodeficiency
syndrome (AIDS) and leptomeningeal
tuberculosis. Note the numerous granulomas on
the dorsal surface of the cord and the dural
T2-weighted magnetic resonance
image of the thoracic spinal cord of
a patient with 2 hyperintense
• CT- The typical lesion is an hypodense focal
area with ring contrast-enhancement and
Nonenhanced T1-weighted images in a
patient infected with human
immunodeficiency virus and cerebral
toxoplasmosis. These images show
hypointense, asymmetrical, bilateral
periventricular/basal ganglial lesions.
T1-weighted axial gadolinium-enhanced
magnetic resonance images. These images
show 2 complex, ring-enhancing lesions in the
basal ganglia on the right, with surrounding
notable white matter edema. This appearance
is typical of central nervous system
toxoplasmosis, which has the propensity for
involvement of the basal ganglia.
Axial fluid-attenuated, inversion recovery brain magnetic
resonance image in a patient infected with human
immunodeficiency virus and cerebral toxoplasmosis. These
images show intense signal at the sites of the infection.
Parenchymal (Single or Multiple)
Nonenhanced CT scan of
the brain demonstrates
the multiple calcified
lesions of inactive
Enhanced CT scan of the brain in a
patient with neurocysticercosis
demonstrates a live cyst with a
minimally enhancing wall and an
eccentric hyperattenuating scolex.
In the colloid stage(when the larva begins to die), the
cyst is encapsulated; it contains a high-protein
fluid, and it demonstrates ring enhancement.
Often, associated edema or enhancement is noted in
the brain parenchyma
CT images of the brain in a patient
with neurocysticercosis show
numerous parenchymal lesions.
Left, CT scan of the brain shows marked
dilatation of the right lateral ventricle in a
patient intraventricular neurocysticercosis.
Right, Contrast-enhanced ventriculogram
shows a fourth ventricular cyst as a filling
defect in the contrast-enhanced spinal column.
T1-weighted (T1), T2-weighted (T2), and fluid-attenuated
inversion recovery (FLAIR) MRIs show a typical cyst with a scolex
(arrow) in a patient with neurocysticercosis (NCC).
T1-weighted (T1) and T2-weighted (T2) MRIs show a
degenerating colloid cyst with a hypointense wall and
hyperintense surrounding edema, which is best depicted on T2weighted images. The patient has neurocysticercosis (NCC).
On MR images, widened perivascular spaces appear as multiple, bilateral, small round-tooval lesions in the basal ganglia and midbrain. These show slightly higher signal than
cerebrospinal fluid on T1W images and high signal on T2W images.
Cryptococcus neoformans infection of the
CNS in an HIV-positive individual., Axial
FLAIR-FSE MRI shows high signal lesions in
the basal ganglia bilaterally with swelling
and hyperintensity of the cerebral cortex
Cerebral aspergillosis in an
immunocompromised patient., Axial T2W MRI
shows multiple hyperintense lesions with
central hypointensity in the left cerebral white
matter, right parietal cortex, and occipital