pediatric neuroradiology essentials

PEDIATRIC NEURO-RADIOLOGYESSENTIALS

Guided by Dr. N. bajaj

Dr. jyoti prajapati

INTRODUCTION

• Several complimentary modalities are currently available in neuroradiology.

• The invention of CT revolutionized imaging of the brain and the spine.

• MRI further improved our diagnostic ability and accuracy of CNS disorders.

• Knowledge in neuro-anatomy is essential for correct diagnosis.

MODALITIES

• Plain Film

• CT

• US

• MRI

• Interventional– Angiography

– Myelography

– Biopsy

• Nuclear Medicine-SPECT,PET SCAN,PET CT

PLAIN RADIOGRAPHS• Plain X-ray is essential modality for initial assessment

of the spine.

• Good display of bony details

• Limited value in evolution of head trauma since it may not reflect underlying CNS damage.

• Skull radiograph helps in classification of skull fractures and its extent and therefore further management.

• Intracranial calcification, suture separation

Use of x ray in Neuro-radiology

• Intracranial calcification

• Raised ICT

• intracranial tumors

• Head trauma

The radiological signs of raised intracranial pressure

• I. Suture diastasis-1ST & most important sign in infants & children

• 2. Sellar erosion- more useful in adults, chronic raised ICT

• 3. Pineal displacement- in adults

• 4. Increased convolutional markings(not much informative)

Suture separation

Sellar erosionNormal sella

Increased convolutional markings

SIGNS OF INTRACRANIAL TUMOR

• Intracranial calcification

• Skull erosion

• Hyperostosis

• Abnormal vascular markings

• Penial displacement

Causes of intracranial calcification• 1. Neoplasms• Craniopharyngioma

• Glioma

• Meningioma

• Ependymoma

• Papilloma of the choroid plexus

• Pinealoma

• Chordoma

• Dermoid, epidermoid, and teratoma

• Hamartoma

• Lipoma

• Metastasis (rarely)

2. Vascular

• Atheroma

• Aneurysm

• Angioma

• Subdural haematoma

• Intracranial haematoma

3. Infections and infestations

• Toxoplasmosis• Cytomegalic inclusion body disease• Herpes• Rubella• Tuberculosis• Pyogenic abscess• Cysticercosis• Hydatid cyst• Porogonimus abscesses• Trichinosis• Torulosis• Coccidioides

INTRACRANIAL CALCIFICATION PATTERN

• Infection – TORCH Toxoplasmosis often scattered, irregular, flaky

• Rubella is massive or punctate

• CMV often curvilinear and paraventricular

• Herpes - involves entire brain

toxoplasmosis

Calcified basal exudate above the sella in a patient withhealed tuberculous meningitis (arrowheads).

Cysticercosis. There are multiple small calcified lesions2-3 mm in diameter (arrowheads).

sturge weber syndrome

Tuberous sclerosis

Metastasis(multiple lytic lesion)

Bilateral hypertrophy of the middle meningeal vascular markings in a patient with a large angiomatous malformation.

Computerized TomographyCT

• Readily available fast modality for evaluation of intracranial structures.

• Rapid acquisition of axial images.

• The procedure of choice for evaluation of patients with head trauma and stroke patients.

• Provides fine details of the bony structures.

• Can be used in emergency and in pt with pacemaker

Indication

• Subarachnoid heamorrage

• Fractures

• Headtrauma

• Detection of calcification in lision

• Bony spinal stenosis

• When MRI is contraindicated

How to read CT

Overall go from the outside of the skull to the the insideMake two passes through the study:

on the first one look at every structure on every slice from the outside to the inside,

on the second looking at one structure at a time, look at every sliceCheck the soft tissues of skullCheck the bony calvariumCheck the cortical sulciCheck the basal gangliaCheck the ventricular size/shape/position

Normal CT of brain

Ventricles are normal sized,

the grey versus white

distinction

is clear.

Midline is straight.

Sulci are symmetrical on both

sides.

Skull is intact with no

scalp edema.

NEONATAL BRAIN• The neonatal brain In CT images the density

of the brain is dependent on the stage of maturation

• At full term the cortex shows convolutions ,the cerebral sulci are well defined, and the cortex and white matter are differentiated.

• In premature infants before 30 weeks the brain is homogeneously low in attenuation with the cortex appearing as a thin denser ring without sulci.

• The sylvian fissures are shallow and wide and the ventricles appear relatively large.-smaller with maturity and at term appear as narrow slits.

• During the same period there is progressive differentiation between white and grey matter, and the sulci and convolutions become defined.

• Contrast between cortex and medulla increases as myelination progresses.

• Low attenuation of the white matter is a normal finding in neonates and usually resolves in the first 2 or 3 months.

Myelination begins in the brainstem and extends into the internal capsules and optic radiations by 6 months of life, forceps major and minor by 1 year, and into the gyral convolutions as in the adult by a year and a half.

1 day 1 year 2 years

mri

3D CT

CT Terminology

• What we can see

– The brain is grey

• White matter is usually dark grey

• Grey matter is usually light grey

• CSF is black

• Things that are brite on CT(hyperdense)

– Bone or calcification

– Contrast agents

– Hemorrhage (Acute)

– Hypercellular masses

– Metallic foreign bodies

NORMAL CT

• Contrast within the image varies from white (high attenuation) to black (low attenuation) with the type of tissue within the voxel:– Bone(white)

– Soft tissue(white)• Gray matter

• White matter

– Water(csf)-(black)

– Fat(black)

– Air(black)

• Pathological processes are identified by alterations in anatomy and attenuation.

• Pathological processes typically increase the water content in tissue it makes them hypodense.

• Intravenous X-ray contrast dye has higher attenuation than soft tissue.

• Due to the blood brain barrier, injecting X-ray contrast normally only brightens blood vessels and tissues without a blood brain barrier like the choroid plexus.

• Pathological processes typically disturb the blood brain barrier allowing contrast to enter.

• Proton Density - the pixel intensity is primarily dependent on the density of protons within the voxel.

• T1 weighting - pixel brightness dependent on proton density and weighted towards those protons that quickly retransmit rf energy decaying to their baseline unexcited state.

• T2 weighting - pixel brightness dependent on proton density and the behavior of neighboring protons.

• T1 weighted images - cortical anatomy

• Proton density weighted images - brainstem and basal ganglia

• T2 weighted images - Ventricles, cisterns and vasculature, edema

T1 weighting

• Tissue contrast•dense bone - dark (few hydrogen protons)•air - dark (few hydrogen protons)•water (CSF) – dark( black)•brain - anatomical–Gray matter - gray–White matter - whiter

T2 WIGHTING• dense bone - dark (few hydrogen

protons)• air - dark (few hydrogen protons)• water (CSF) – bright(hyperdense)• brain

–Gray matter - gray–White matter - darker than gray

–Proton Density - intermediate between T1 and T2 signals• Gray matter - gray• White matter - darker than gray

axial sections showingnormal anatomy. (A) T,-weighted section shows CSF black and clear

differentiation between white and grey matter. (B-G)T2-weighted sections in another patient show CSF white and white matter

dark while grey matter remains grey.

MRI

T1 T2

MRI

• When protons are placed in a magnetic field they become capable of receiving and transmitting radiofrequency(rf) electromagnetic waves.

• After receiving rf energy the protons retransmit rf energy proportional to the density of protons.

• A pixel within an MRI image represents the amplitude of the radio frequency signal coming from the hydrogen nuclei (protons) in the water and fat within the voxel.

• The timing of the rf pulses and gradients are altered in different sequences to change the relative weighting between the proton density and factors in the microenvironment.

MRI indication• Neoplasm- asessment of size,extent & effect

on normal brain.

• developmental anomalies of the brain.

• Neurodegenerative/ demylinating disorders

• vascular anomalies of the head (aneurysm )

• stroke

• trauma patients (after 24 hr).

Cont.

• disease in the pituitary gland.

• Inflammatory & infectious deseases (most sensitive for detection for demylinating plaque)

• Headache

• Chronic encephalopathies

• Cyst & hydrocephalous

• Myelopathy & degenerative disorders of spinal cord

• MRI is less sensitive than CT in detection subarachnoid heamorrage ,bony abnormalities, calcification, and can not be performed in pt with pacemaker & mettalicprosthesis

Normal MRI

MR-T1 MR-T2 xray-CT

dense bone Dark Dark Bright

Air Dark Dark Dark

Fat Bright Bright Dark

Water Dark Bright Dark

Brain anatomical interm. interm.

Normal tissue

MR-T1 MR-T2 CTenhancement

infarct dark bright Dark subacute

bleed Bright bright Bright no

tumor Dark bright dark Yes

MS plaque Dark Bright dark acute

Abnormal tissue

CT MRI

Time taken for

complete scan:

Usually completed within 5

minutes

Scanning typically run

for about 30 -40min

Details of bony

structures:

Provides good details

about bony structures

Less detailed compared

to CT scan

Effects on the

body:

More less

Principle used for

emaging

X-ray Uses large external field,RF pulse

Details of soft

tissues:

Less tissue contrast Much higher detail in

the soft tissues

Radiation

exposure:

Moderate to high radiation None

COST medium high

d/b gray & white

matter

good excelent

awailability Easily awailable less

CT ANGIOGRAPHY

INDICATION- arteriovenous malformation

• Old cases of stroke

• Aneurism

• Cerebral thromboembolism

• Vascular tumor

Normal carotid angiogram

Arteriovenous malformation

Vertebral arteriogram showing dissecting aneurysm of a posterior

interior cerebellar artery (MR study).

Aneurism in MR angiography

Cantrst enhanced MR Angiography

CT angio of giant unruptured MCA aneurysm

PET SCAN• Positron emission tomography (PET) is a non-invasive

diagnostic imaging procedure that assesses the level of metabolic activity and perfusion in various organ systems of the human body.

• A positron camera (tomograph) is used to produce cross-sectional tomographic images, which are obtained from positron emitting radioactive tracer substances (radiopharmaceuticals) such as 2-[F-18] fluoro-d-glucose (FDG) that are administered intravenously to the pt.

• Most common indication is for diagnosis and staging for cancers.

PET- SCAN

• Positron emission tomography (PET) proving usefulness in certain aspects of brain deseases by showing differences in local brain metabolism but is expensive and is only available at special centres.

Pet scan indication

• Most common indication is for diagnosis and staging for cancers.

• Refractory epilepsy

• Parkinsonism

• Dementia

• Neurodegenerative disoder

• Brain & spinal cord tumor

• Neuroendocrine tumors

Acadeny of medicine singapur

• Epilepsy• Between seizures, a PET scan displays

decreased metabolism in the area of the seizure and increased metabolism in the same area during a seizure.

CRANIAL USG

• CUS helps in demonstration of cerebral pathologies in premature and sick newborn babies like hemorrhage, ischemia and ventricular dilatation.

• Also, knowledge of cerebral pathology aids in predicting neurological outcome according to the grade of injury.

What are the indications of doing CUS in a neonate?

• a. Screening CUS in a premature baby

• b. Clinical suspicion of intracranial hemorrhage

• c. Neonatal seizures

• d. Evaluation of large or rapidly enlarging head

• e. Serial follow up of post hemorrhagic hydrocephalus

• f. Hypoxic Ischemic encephalopathy

how to read

In the coronal images, check the size, contents, and position of the lateral ventricles, looking for ventricular dilation, intraventricular hemorrhage, and midline shift.

Look for parenchymal lesions such as hemorrhage or infarct.

• In the sagittal images check the caudothalamic grooves for signs of hemorrhage, check the midline for the corpus callosum and the cerebellum

Pattern of injury in TF-USGThe following pathologies may be detected by careful ultrasound examination in a

term baby with encephalopathy

• a. Basal ganglia injury may be evident as echodense(hemorrhagic necrosis) or as echolucent lesions (non-hemorrhagic necrosis).

• b. Focal ischemic lesion may be evident as echodensity in an area of vascular distribution associated with loss of pulsations in the affected vessel.

• c. Periventricular Injury, like in a premature baby, may show up periventricular flare, cyst formation and progressive ventricular dilatation.

CT MRI are not indicated routinely in nicuthough being extremely sensitive bcs of risk of radiation and it takes time and baby can not be monitored during procedure.

Currently, data available from class II studies do not provide sufficient evidence that routine MRI should be performed on all very low birth weight (VLBW) infants for whom results of screening cranial US are abnormal.

Coronal Midline sagittal

Angled para sagittal

Tangential parasaggital

frontal Ant horn of 3rd

ventricle

trigone

Occipital

Cranial usg

Sagital view

Cranial usg coronal view frontal lobe

Early periventricularleucomalacia:ultrasonography shows increased

echogenicity in B/L frontal and left parietal region

Grading of neonatal intracranial haemorrhage

• Several grading systems have been used for IVH .Commonly used is the one proposed by Burstein and Papile et.al, which is a sonographic grading system

• grade I– restricted to subependymal region / germinal matrix which is seen in

thecaudothalamic groove– overall good prognosis

• grade II– extension into normal sized ventricles and typically fills less than 50 % of the

volume of the ventricle– overall good prognosis

• grade III– extension into dilated ventricles– ~ 20 % mortality

• grade IV– grade III with parenchymal haemorrhage– 90 % mortality– it should be noted that it is now thought that grade IV bleeds are not simply

extensions of germinal matrix haemorrhage into adjacent brain, but rather represent sequelae of venous infarction

B/L grade III germinal matrix and intraventricular hemorrhage with

hydrocephalus

Cranial Usg in metabolic disorder

Coronal view

Hemiparetic CP

BRAIN ABSCES

necrotic, supprative center encapsulated by a peripheral rim of hyperemic granulation tissue.

It is normally located at the gray matter / white matter junction, and is surrounded by edema.

The granulation tissue shows ring enhancement with contrast.

Cerebral abscesses from endocarditis

DEMYLINATING DISORDERS

MS-axial T2-weighted image. Plaques are mainly periventricular, oval shaped with a major transverse axis, hyperintense with respect to normal parenchymaRING ENHANCEMENT FOLLOWINF GADOLLIUM INJECTION

INFARCTION

INFECTION & INFLAMATION

• The lesion is poorly defined, usually hypodense at CT and on MRI it is hypointense in T1 and hyperintense in T2.

• MeningitisBoth CT and MRI may show leptomeningeal enhancement and associated cortical or brain involvement.

abscess formation in a patient with bacterial meningitis. This contrast-enhanced, axial T1-weighted magnetic resonance image shows a right frontal parenchymal low intensity (edema), leptomeningitis(arrowheads), and a lentiform-shaped subdural empyema(arrows).

Bacterial meningitis. Axial Nonenhanced CT

scan shows mild ventriculomegaly and

sulcal effacement

Microbacteria and fungi produce abscesses and granulomas with or without meningeal involvement;

both CT and MRI are sensitive in demonstrating the lesions, particularly following contrast injection.

TBM may show enhancing liesion after contrast injection.

Parasitic infections

• The most common parasitic infections are cysticercosis and echinococcosis.

• In cysticercosis, both intraparenchymal and meningeal cysts are found which at different stages may include calcified nodules

• CT clearly demonstrates the calcification; frequent meningeal enhancement is encountered.

Hole with dot on CT

SWISS CHEES

MRI

TBM

• On CT scan, the most common finding in cranial tuberculous

• meningitis (TBM) is obliteration of the basal cisterns by isodense or mildly hyperdenseexudate.

• After the administration of contrast medium, there is dense homogeneous enhancement of the basal meninges.

TBM

• Contrast-enhanced computed tomography scan shows dense enhancement of

• the thickened inflamed basal meninges.

MILIARY TB

VentriculitisBRAIN STEM CEREBRITIS

Granulomatoustuberculousmeningitis,

ventriculitis, andspinal

arachnoiditis

Caseatingtuberculosis

granuloma involving the left

thalamus and causing obstructive

hydrocephalus in

Viral infections

• These may produce minimal changes at CT and be better seen at MRI with non-specific T2 hyperintensity both involving the cortex and the white matter.

• Herpes simplex encephalitis may have haemorrhagic components demonstrated by CT and occurs usually bilaterally in specific locations such as the temporal lobe, the hippocampus and the insula.

Herpes encephalitis

Bi-temporal distribution is typical.

Thought to occur by re-activation

of herpes virus much like “cold sores”

Except through different nerve

Distribution.

HSV ENCEPHALITIS

CONGENITAL ABNORMALITEIS

DANDY WALKER SYNDROME

PORENCEPHALY

Neurocutaneous syndrome

Tuberous sclerosis MRI

Sturge weber syndrome

Brain tumors

• High-grade or malignant gliomas appear as contrast-enhancing mass lesions, which arise in white matter and are surrounded by edema

• Multifocal malignant gliomas are seen in ~ 5% of patients.

• Low-grade gliomas typically are nonenhancinglesions that diffusely infiltrate brain tissue and may involve a large region of brain.

• Low-grade gliomas are usually best appreciated on T2-weighted MRI scans.

Brain tumor

T2

Stroke

• Intra parenchymal

• Subarachnoid heamorrhage

• Subdural heamatoma

• Epidural heamatoma

• Lacunar infarcts

• Ventricular bleed

MCA Stroke“Dense MCA”

Case 2

Epidural heamotoma

Subarachnoid heamorrhage

Subarachnoid Hemorrhage

Blood shows white on CT.

Anterior Communicating Artery

aneurysm has burst, flooding the

basal structures under the brain

outside the brain parenchyma, but

will occasionally empty into a

Ventricle as it has on the left here

(see fluid level). Note typical

“bat wing” shape just above the

mid-brain (green arrow).

Intraparenchymal bleed into ventricles

Intraventricular bleed

Radiation risk

• Relative values of CT exam exposure

– Background radiation is 3 mSv/year

• Water, food, air, solar

• In Denver (altitude 5280 ft.) 10 mSv/year

– CXR = 0.1 mSv

– CT head = 2 mSv

– CT Chest = 8 mSv

– CT Abdomen and Pelvis = 20 mSv-The equivalent of 200 CXR

Thanks for listening

References;-nelson

suttons radiology

neuroradiology –robert

caffeys

pediatric radiology donnelly

various websites