1. CNS INFECTIONS

2. 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.

3. This axial nonenhanced
computed tomography
scan shows mild
ventriculomegaly and
sulcal effacement
Acute bacterial meningitis.
This axial T2-weighted
magnetic resonance image
shows only mild
ventriculomegaly.
This contrastenhanced, axial T1weighted magnetic
resonance image shows
leptomeningeal
enhancement (arrows).

4. Viral Meningitis and
Meningoencephalitis
Viral Meningitis
• The diagnosis is made clinically and imaging
has no contribution.

5. Viral Encephalitis
•
•
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
same patient
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.

6. 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).

7. Cytomegalovirus encephalitis
Cytomegalovirus encephalitis. Characteristic enhancement in
ependyma around lateral ventricles

8. Togavirus (Japanese Encephalitis)
Deep-seated structures characteristically involved: subcortical white matter
(top arrow), thalami (middle arrow), and substantia nigra (bottom arrow)

9. HIV infection of CNS
• Characteristic abnormalities are brain atrophy and diffuse
white matter attenuation

10. JCV infection- PMLE
•
Progressive Multifocal Leuco Encephalopathy
•
Typical multifocal and confluent subcortical nonenhancing white matter hyperintensities extending
to the cortical gray matter
.

11. Acute disseminated or post infectious
encephalomyelitis after virus infection
•
Subcortical white matter lesions (short arrow) involving subcortical U fibers with
tangential lesions (long arrow).

12. 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

13. Subdual And epidural Empyemas.
• Empyema is a "closed space infection" occurring inside a
body cavity or space
Epidural Empyema CT
Subdural Empyema CT

14. Subdural Empyema
Axial T1WI shows
hypointense subdural
fluid collection along the
right fronto-parietal
convexity (small arrows)
with minimal air-fluid
level (arrowhead).
The right subdural
fluid collection is
hyperintense in
axial T2WI (arrows).
Axial post-contrast
T1WI shows ring
enhancement of the
right subdural fluid
collection (arrow)
with associated
meningeal
enhancement
Axial diffusion
weighted images shows
increased signal of the
right subdural fluid
collection (arrow) with
low apparent diffusion
coefficient.

15. Brain Abscess
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
fossa.
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.

16. 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
restriction.

17. Cerebritis
CECT
Brain : poorly
defined hypodense and
non-enhancing
area of cerebritis in the
right parietal lobe.
Multiple areas of
dilated
perivascular spaces
with restricted
Contrast-enhanced
On T2-weighted MRI
diffusion
image (TR/TE2500/90) T1-weighted image
(arrows), suggestin
(TR/TE/flip°
the lesion is
20/2.1/35°) shows no g development of
hyperintense.
multiple
enhancement.
parenchymal foci
of cerebritis.

18. TB Meningitis
Contrast-enhanced computed
tomography (CT) scan in a
patient with tuberculous
meningitis demonstrating
marked enhancement in the
basal cistern and
meninges, with dilatation of
the ventricles.
Contrast-enhanced computed
tomography (CT) scan of a child
with tuberculous meningitis
demonstrating acute
hydrocephalus and meningeal
enhancement.

19. MRI is more sensitive than CT scanning in determining the
extent of meningeal and parenchymal involvement
T2-weighted magnetic
resonance image of a biopsyproven, right parietal
tuberculoma. Note the low–
signal-intensity rim of the
lesion and the surrounding
hyperintense vasogenic
edema.
T1-weighted gadoliniumenhanced magnetic
resonance image in a
patient with multiple
enhancing tuberculomas
in both cerebellar
hemispheres.
T1-weighted
gadolinium-enhanced
magnetic resonance
image in a child with a
tuberculous abscess in
the left parietal region.
Note the enhancing
thick-walled abscess.

20. 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
enhancement.
T2-weighted magnetic resonance
image of the thoracic spinal cord of
a patient with 2 hyperintense
intramedullary tuberculomas.

21. CNS Toxoplasmosis
• CT- The typical lesion is an hypodense focal
area with ring contrast-enhancement and
edema

22. 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.

23. 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.

24. Neurocysticercosis
Four types
•
•
•
•
Meningeal
Parenchymal (Single or Multiple)
Intraventricular
Mixed

25. Nonenhanced CT scan of
the brain demonstrates
the multiple calcified
lesions of inactive
parenchymal
neurocysticercosis
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.

26. 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

27. 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.

28. MRI
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).

29. 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).

30. Fungal Infections
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
bilaterally.
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
cortex

31. Hydatid Cyst Brain