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Inflammatory and infectious
intracranial cysts
• 20-brain abscess
• 21-cysticercosis
• 22-hydatid cyst.
• 23-amoebic abscess
Dr Ahmed Esawy
Brain Abscess
Dr Ahmed Esawy
Brain abscess..
poorly defined area of posterior parietal brain edema (arrows). Early cerebritis
may not outline a focal mass clearly Dr Ahmed Esawy
Brain abscess.
a poorly defined pattern of mass effect and low attenuation in the left temporal lobe.
Of early cerebritis
Dr Ahmed Esawy
Brain abscess.
An area of ring like enhancement (yellow arrow) is noted within a much larger pattern of
edema (white arrow). The central core of the abscess (black arrow) does not enhance
(central necrosis) Dr Ahmed Esawy
temporal lobe abscess, extracranial, subdural, and intracerebral abscesses
Dr Ahmed Esawy
Brain abscess.
depressed skull fracture. The left parietal cranial injury an abscess of the subgaleal
space (SGA) the epidural space (EDA) the left cerebral hemisphere (CA).
Dr Ahmed Esawy
Brain abscess. Axial T1 +C ,T2-weighted MRI in a patient with a right frontal abscess.
Dr Ahmed Esawy
The right frontal lobe of the
brain is shifted across the
midline (double arrow) by an
intracranial abscess (single
black arrow) that has extended
upward from the medial right
orbit and medial ethmoid air
cells (curved dotted arrow).
T1-contras Brain abscess T1-contras
the enhancement within the right ethmoid
sinuses from which the infection arose.
The medial superior right maxillary sinus
has been destroyed (yellow arrow).
T1-contras
An abscess is noted within the medial inferior right orbit. The right maxillary sinus
(double white arrows) contains infected secretions and mucus Dr Ahmed Esawy
Brain abscess. (FLAIR) MRI
in a patient with abscess of the
cerebellar vermis (black arrow).
T2- MRI abscess of the midline
cerebellum. the large area of
increased signal, both within the
abscess and within the surrounding
cerebellum (black arrow).
Dr Ahmed Esawy
Brain abscess. T1-enhanced
central zone of enhancement
within the abscess, with a zone of
decreased brightness (edema,
white arrow). Brain abscess. T1enhanced
enhanced mass within the right medial
cerebellum (yellow arrow). The thick-
walled cystic mass was opened.
Dr Ahmed Esawy
CEREBRAL ABSCESS ON DW MRI
On trace DWI abscesses are typically hyperintense, indicating decreased diffusion of water.
– This is secondary to increased viscosity of pus
which contains, in addition to cellular debris and bacteria, large molecules such as fibrinogen, which bind water molecules and add to the effect of restricted diffusion.
– This can be confirmed with an apparent diffusion coefficient (ADC) map where abscesses are of low signal ,markedly reduced ADC
Dr Ahmed Esawy
Diffusion-weighted Imaging
ADC maps are of great value in
distinguishing neoplasms in ADC maps is
more often have facilitated diffusion,
Dr Ahmed Esawy
CEREBRAL THALAMIC ABSCESS ON MRI
Post-Gd T1WI: WI2T DWI
Dr Ahmed Esawy
Left and right frontal abscesses:
35-year-old male.
DWI ADC WI2T WI1T
Dr Ahmed Esawy
Pyogenic Abscess
T2 T1 T1/Gd DWI
bright on DWI
Dr Ahmed Esawy
Abscess (purulent) ADC decreased
dark on ADC map Dr Ahmed Esawy
7. 8.
DD : tumour
central hypointensity on diffusion-weighted image and hyperintensity on ADC
map, consistent with the diagnosis of tumor.
Dr Ahmed Esawy
7. 8. DD : tumour
Central hypointensity is seen on the diffusion-weighted image and hyperintensity
on the ADC map, consistent with the diagnosis of tumor.
Dr Ahmed Esawy
Brain abscess primary and secondary (daughter
Fluid and necrotic tissue (bright area) . edema surrounds
the abscess cavities (black arrows).
surrounding the abscess does not enhance
(white arrows).
DWI T1/Gd
Dr Ahmed Esawy
Brain abscess (FLAIR)
left occipital-parietal brain abscess.
Dr Ahmed Esawy
MRI Brain
abscess
T1/Gd
T2
well-defined hypointense
capsule
DWI
Dr Ahmed Esawy
MR Spectroscopy
• .Typical MR spectroscopic features of brain
abscesses include
• elevated peaks of amino acid, lactate,
alanine, acetate, pyruvate, and succinate
• absent signals of NAA, creatine, and choline.
Dr Ahmed Esawy
MR spectroscopy
• shed light on which organism is
responsible for the abscess
• because the presence of anaerobic
bacteria tends to cause elevated acetate
and succinate peaks.
Dr Ahmed Esawy
DD : NEOPLASM
• Elevation of choline and absence of signal from a variety of amino acids, acetate and succinate favours neoplastic process
Dr Ahmed Esawy
Dr Ahmed Esawy
Dr Ahmed Esawy
necrotic or cystic neoplasms Pyogenic brain abscesses
Elevated choline , decrease
NAA
elevated peaks of amino acid,
lactate, alanine, acetate,
pyruvate, and succinate
absent signals of NAA,
creatine, and choline
MRS
facilitate diffusion
dark
restricted diffusion
bright
DW
Bright on ADC map
The walls of necrotic or cystic
tumors have a lower ADC
value than of an abscess
markedly reduced ADC maps. ADC
wall of necrotic or cystic
neoplasms tends to have higher
rTBV
capsule of an abscess tends to
have lower rTBV
MR PERFUSION
Dr Ahmed Esawy
Signal volume MR spectra of
abscess
Short-echo MRS shows depression of the NAA, choline (Cho) and creatine (Cr) as well as elevation of the amino acid, lactate (Lac), acetate and succinate. Dr Ahmed Esawy
T2 T1+C
Single voxel MRS peaks representing
alanine, lactate and amino acids
DW hyperintense
signal in centre
ADC decrease signal
in centre
Brain abscess
Dr Ahmed Esawy
brain abscess
Dr Ahmed Esawy
Brain abscess in a 28-week gestation
preterm newborn
well-defined cystic structure with low-
level echoes (arrowheads) in the left
posterior parietal region
abscess has ring enhancement (arrowheads). Dr Ahmed Esawy
cysticercosis
Dr Ahmed Esawy
Cystercercus cellulosae - (3-20 mm)
regular round thin walled cyst,
produces only mild inflammation
larva in cyst
Dr Ahmed Esawy
Calcification in cysticercosis
• Calcification in burned out residues of cysticercosis
scattered throughout the brain in later stages Dr Ahmed Esawy
NEUROCYSTICERCOSIS
Multiple neurocysticercosis cysts of various sizes. Some contain visible scolices (arrows). MR image shows
T1 innumerable tiny low-signal-intensity
neurocyticercosis cysts in brain
parenchyma and subarachnoid spaces.
Most contain small “dot” that represents
the scolex (arrows Dr Ahmed Esawy
Intraparenchymal cysticercal cyst
Scolex within each cyst
Dr Ahmed Esawy
Differential Diagnosis
• abscess (T2-hypointense rim (
• Tuberculosis (profoundly hypointense on T2 ,meningitis)
• toxoplasmosis
• neoplasm primary or metastatic
• enlarged PVSs same appearance as CSF at all MR sequences and do not enhance)
• NEUROCYSTICERCOSIS characteristic “cyst with dot” appearance .
Dr Ahmed Esawy
multiloculated
amebic abscess
partially cystic mixed-signal-intensity
subcortical mass (arrow)T1 .
some enhancement around complex cystic
mass (arrow)T1+CONTRAST Dr Ahmed Esawy
Differential Diagnosis
• Complex conglomerated parasitic cysts of
any origin may mimic primary or
metastatic brain tumor .
Dr Ahmed Esawy
hydatid cyst
CT Unilocular cyst CSF density No edema no enhancement ± calcification
MRI low signal T1 , high signal T2 Dr Ahmed Esawy
hydatid cyst
T1+C
T1
T2
Dr Ahmed Esawy
HYDATID CYSTS
• 5 year child
very large nonenhancing cystic mass
without surrounding edema (arrows). Dr Ahmed Esawy
Differential Diagnosis
• arachnoid cyst
• epidermoid cyst
• neurocysticercosis
Dr Ahmed Esawy
Tuberculous abscesses
T1- multiple scattered ring-enhancing lesions
Dr Ahmed Esawy
MRS
• Tuberculous abscesses typically have high
lipid and lactate peaks.
• These abscesses have no peaks for amino
acids (leucine, isoleucine, and valine) at 0.9
ppm, succinate at 2.41 ppm, acetate at 1.92
ppm, and alanine at 1.48 ppm,
• in contrast to pyogenic abscesses, which
have peaks for all these metabolites.
Dr Ahmed Esawy
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