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