imaging in head trauma

Dr. Sunil Kumar SharmaSenior Resident

Dept. of NeurologyGMC Kota

Aim

To understand Indications and select the appropriate imaging modality

To identify common traumatic emergency abnormalities of brain.

To determine an immediate life threatening abnormality on a CNS imaging

INTRODUCTION

Head trauma is the leading cause of death in people under the age of 30.

Males have 2-3 x frequency of brain injury than females

Due mainly to motor vehicle accidents and assaults

OUTLINEClassification of traumatic brain injuryClinical indications for imagingImaging techniqueExtraaxial hemorrhageIntraaxial injuryBrain herniations

Classification of traumatic brain injury

Traumatic Brain Injury

Classification -Primary & Secondary

Mechanism of injury-Penetrating, Blunt

Location-Intraaxial, Extraaxial

Clinical severity, GCS -Mild, Moderate, severe

Classification of TBIPrimary

Injury to scalp, skull fracture

Surface contusion/laceration

Intracranial hematoma

Diffuse axonal injury, diffuse vascular injury

Contd..Secondary

Hypoxia-ischemia

swelling/edema

raised intracranial pressure

Meningitis/abscess

Imaging ModalitiesPlain Radiography

Ultrasound

CT

MRI

Radionuclide studies

Angiography

Conventional X-raysUses a form of Ionizing radiation

Good in evaluating air containing structures, bones and calcifications

Limitations No depth information

Low soft tissue contrast

Radiation

Computed Tomography

Uses Ionizing radiation.Cross-sectional imagePrinciple based on differential x-ray beam

attenuation by tissue Image contrast, displayed as Gray scale –

Density/attenuation Low attenuation-Darker High Attenuation-Whiter

APPROACH TO CT BRAINLook at the scout film: ? Fracture of upper

cervical spine or skullLook at bone windows to see fracturesLook for brain asymmetryLook at sulci, Sylvian fissure and cisterns

to exclude subarachnoid hemorrhageLook for subdural collectionDetermine if mass is intraaxial (in the

brain) or extraaxial (outside)

Advantages of CT

High sensitivity for calcificationEasier and faster to perform.Most sensitive for detection of acute

hemorrhage Increasing availability No contraindications to emergency patient

scanningQuickest & most efficient screening

technique in acute traumatic setting

Disadvantages of CT

High radiation dose per examination

Children are more sensitive to radiation induced cancers than adults

Bone marrow, thyroid, breast, and lung are at greatest risk

Contrast related side effects

Factors to Consider When Determining Need of CT in Patients with Head InjuryIndications for urgent CT scan include:Evidence of skull fracture—basal,

depressed, or open

Abnormal results of neurologic examination

Seizure

Vomiting >1 time

High-risk mechanism (e.g., ejection from vehicle; pedestrian or cyclist versus automobile)

Decreasing GCS score or persistently decreased GCS score of <15.

Indications for lower threshold for CT scan include:Age >60 yr

Persistent anterograde amnesia

Retrograde amnesia >30 min

Coagulopathy

Fall >5 stairs or >3 feet

Cont..Intoxication (examination unreliable)

LOC >30 min

Mechanism and location of injury

Social factors (e.g., abusive situation at home, language barriers preclude accurate history)

Magnetic Resonance Imaging

Advantages of MRIUses non ionizing radiation

Less invasive technique

Multiplanar capability

Excellent soft tissue contrast

Ability to depict flowing blood without the need of IV contrast administration

Disadvantages of MRI

Cost

Limited Availability

Length of the examination time

Physiological motion artifacts

Acoustic noise

Contraindications of MRI

Ferrous object: Oxygen tanks, wheelchairs in the scan room is extremely dangerous

Pts. who have electrically &/or magnetically activated implants: Cardiac pace makers, Implanted defibrillators

Pts. with intracranial aneurysm clipsMetal within the eyeSome decorative tattoos

Indications for CT, MRI Scanning of BrainGeneral rules in brain imaging-Acute neurological illness-Start with CT Sub acute/ ChronicStart with MRIMRI is the imaging study of choice in

evaluating most brain abnormalitiesHead CT is the 1st line modality for brain

emergency

Cont…

General rule in Spine imaging -Bony spine-CT, Conventional radiograph Marrow replacing diseases-MRI Intervertebral Disc-MRI, CT MyelographyContents : Spinal cord, nerve roots, ligaments- MRI

Extraaxial Injury

Skull fracture

Epidural hematoma

Subdural hematoma

Subarachnoid hemorrhage

Skull Fracture

Not predictive of intracranial injury

Absence does not exclude intracranial injury

Types-Linear, depressed, basal, comminuted

Risk of brain injury increases with the depth of depression

Skull x-ray findings-

Linear fracture-• Lucent sharply

defined line without sclerotic margin

Mimics-Vascular groove , sutures

Depressed fracture –

• Increased or double density on x-ray

• Best evaluated by CT

• >5mm, elevation indicated

Epidural Hematoma

Blood collection within potential space between skull

inner table & dura mater75 % at the temporal region Usually (99%)at the coup side Majority have Skull fracture 85-95% ; In

children often absent Mostly arterial bleed ,Due to laceration of the

middle meningeal artery or dural veinsExpands and present rapidly -Tense distension

Radiological signs

Biconvex with a sharply defined margin Does not cross suture line unless there is

fracture/diastasisMass effect +/-brain herniationDisplacement of sinus, falx from the skull Adjacent skull fracture

MANAGEMENT OF EDH

EDH > 30 cm3 should be evacuated.

EDH < 30 cm3 and <15 mm thickness and < 5 mm

midline shift and GCS >8 may be managed nonoperatively with serial CT

SUBDURAL HEMATOMAOccurs between the dura and arachnoid

Can cross the sutures but not the dural reflections

Due to disruption of the bridging cortical veins

hyperdense(acute), isodense(subacute) Hypodense(chronic),

Radiological signsCrescent shape The most common locations are the frontal

and parietal convexities.Countercoup Unlike an EDH, its spread is not limited by

suture lines; it can spread over the whole convexity, but it almost never crosses the midline

Mass effect +/-brain herniationSkull fracture in < 50 %

SUBDURAL HEMATOMA

MANAGEMENT OF SDH

Acute SDH with thickness > 10 mm or midline shift > 5mm should be evacuated

Patient in coma with a decrease in GCS by >2 points with a SDH should undergo surgical evacuation.

SUBARACHNOID HEMORRAGECan originate from direct vessel injury, contused cortex

or intraventricular hemorrhage.In contrast to aneurysmal SAH, the blood is superficial

in the cortex and not present in the basal cisterns.Usually focal (but diffuse from aneurysm)In some instances, for example, if blood is found in the sylvian fissure, a vascular study (CTA,DSA) is needed to rule out an aneurysm rupture.Can lead to communicating hydrocephalus

Intraventricular hemorrhageMost commonly due to rupture of

subependymal vessels

Can occur from reflux of SAH or contiguous extension of an intracerebral hemorrhage

Look for blood-cerebrospinal fluid level in occipital horns

Intraaxial injury Surface

contusion/lacerationIntraparenchymal

hematomaWhite matter shearing

injury/diffuse axonal injury

Post-traumatic infarctionBrainstem injury

CONTUSION/LACERATIONSMost common source of traumatic SAHContusion: must involve the superficial

gray matterLaceration: contusion + tear of pia-

arachnoidAffects the crests of gyriHemorrhage present ½ cases and occur at

right angles to the cortical surfaceLocated near the irregular bony contours:

poles of frontal lobes, temporal lobes, inferior cerebellar hemispheres

Intraparenchymal hematomaFocal collections of blood that most

commonly arise from shear-strain injury to intraparenchymal vessels.

Usually located in the frontotemporal white matter or basal ganglia

DDx: DAI, hemorrhagic contusion

DIFFUSE AXONAL INJURYDIFFUSE AXONAL INJURY

Rarely detected on CT ( 20% of DAI lesions are hemorrhagic)

MRI: T1, T2, T2 GRE, DWI

DAIDue to acceleration/deceleration to whtie matter

+ hypoxia

Patients have severe LOC at impact

Grade 1: axonal damage in WM only -67%

Grade 2: WM + corpus callosum (posterior > anterior)

– 21%

Grade 3: WM + CC + brainstem

DTI

Traumatic cerebral infarctBest diagnosed by: Restricted diffusionLocation- Most commonly occur in PCA vascular distribution,

MCA, ACA, vertebrobasilar relatively common

Other: Lenticulostriate, thalamoperforating; cortical/subcortical; cerebellar

Traumatic cerebral infarct

SUBFALCIAL HERNIATIONSubfalcial: displacement of the cingulate gyrus

under the free edge of the falx along with the pericallosal arteries.

Can lead to anterior cerebral artery infarction

DESCENDING HERNIATION

Herniation:Ascending TranstentorialCranial shift of

vermis and parts of superomedial cerebellar hemisphere through tentorium incisura

Compressed superior cerebellar, vermian cisterns and forth ventricle

TONSILLAR HERNIATION

Inferior displacement of the cerebellar tonsils through the foramen magnum

Can lead to posterior cerebellar artery infarction

EXTERNAL HERNIATIONDue to a defect in the

skull in combination with elevated ICP

Venous obstruction can occur at the margins of the defect.

Conclusions

CT = primary modality for head trauma, enough for

most parts Skull x-rays still used in penetrating trauma, suspected child abuseMRI to help predicting prognosis by detection of subtle injuries i.e., contusion and DAI Primary vs secondary lesion. Often, secondary lesion more important

ConclusionsWhile checking the scan, make sure to think if the patient needs CTA or other CTs (C-spine, facial bones, etc) Coup-contrecoup mechanism helps confirm acute trauma nature and search for subtle lesions

Thank you

Thank you

References

Osborn Diagnostic Imaging Brain-2004

Bradley’s Neurology in Clinical Practice 6’th edition 2012

Slideshare.com

Radiopedia.com