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Emergency Neuroradiology
Last Updated: October 29, 2003
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Synonyms and related keywords: neuroimaging,
head trauma, cranial trauma, head injury, cranial injury, cranial imaging, computed
tomography, head CT, magnetic resonance imaging, head MRI, angiography
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AUTHOR INFORMATION
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Section 1 of 8  
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Author: Michael
Rothman, MD, Section Chief, Department of Radiology, Division of
Magnetic Resonance Imaging, Saint Luke's Hospital
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Editor(s): Dana
A Stearns, MD, Assistant Director of Undergraduate Education,
Assistant, Department of Emergency Medicine, Massachusetts General
Hospital; Francisco Talavera, PharmD, PhD, Senior Pharmacy Editor, Pharmacy, eMedicine; Gino A Farina, MD, Program Director,
Assistant Professor, Department of Emergency Medicine, Long Island Jewish
Medical Center, Einstein College of Medicine; John Halamka,
MD, Chief Information Officer, CareGroup
Healthcare System, Assistant Professor of Medicine, Department of Emergency
Medicine, Beth Israel Deaconess Medical Center; Assistant Professor of
Medicine, Harvard Medical School; and Barry Brenner, MD, PhD,
Chairman, Department of Emergency Medicine, Professor, Departments of
Emergency Medicine and Internal Medicine, University of Arkansas for
Medical Sciences
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INTRODUCTION
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Section 2 of 8 
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Trauma is the leading cause of death in
patients younger than 45 years. Cranial trauma accounts for a substantial
proportion of morbidity and mortality in all age groups and is the leading cause
of death in patients younger than 30 years. Accurate, rapid, noninvasive
assessment of people with cranial trauma is required for appropriate triage
and management. Computed tomography (CT) is the diagnostic procedure of
choice for acute injury, while magnetic resonance imaging (MRI) has great
value for evaluation in the subacute and long-term.
Closed head injury and penetrating
trauma account for the majority of cerebral trauma, although other processes,
such as acute cerebral infarction or subarachnoid
hemorrhage due to rupture of intracranial aneurysms, may mimic a traumatic
injury on presentation.
Acute cranial trauma affects all ages
and both sexes, with incidence of 0.25% annually. Penetrating injuries affect
young males disproportionately. The male-to-female ratio is 4:1 for fatal
injuries, predominantly penetrating trauma and assaults. Nonaccidental
trauma in children, ie, child abuse, accounts for
over 1 million cases annually.
The mortality from cranial injury alone
is 20% overall. Approximately 20% of survivors have permanent damage and
disability.
History
- Head trauma
- Motor vehicle accident
- Fall from height
- Penetrating injury
- Rhinorrhea/otorrhea - Cerebrospinal fluid leak
- Prolonged loss of consciousness
- Acute headache accompanied by abnormal neurologic examination, amnesia, depressed sensorium, or hypertension
- Hemiparesis, weakness, or neurologic
deficit
Physical
- Glasgow coma scale decrease of 3 points or
more
- Depressed skull fracture
- Penetrating head injury
- Focal neurologic
deficit
- Acute pupillary
inequality
- Unresponsiveness
- Depressed sensorium
- Intoxication
- Coagulation disorder/therapy
- Prolonged loss of consciousness
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DIFFERENTIAL DIAGNOSES
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Section 4 of
8
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Acute stroke
Cardiac syncope
Hypertensive hemorrhage/crisis
Intracranial hemorrhage due to rupture of arteriovenous
malformations or aneurysms
Intracranial tumor
Postictal state status postseizure
Meningitis/systemic infection
Toxic/metabolic disorders
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DIAGNOSTIC WORKUP
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Section 5 of 8
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Computed tomography scanning
CT is the imaging procedure of choice
in evaluation of acutely injured patients or patients with acute neurologic deficit. Quick, easy, reliable, and routinely available,
CT is valuable in making a firm diagnosis, as well as in excluding
alternative diagnoses or the sequelae of other
pathology, even in uncooperative patients. Patient monitoring is simple and
safe, and CT is compatible with patient stabilization devices. Identification
and localization of calvarial fractures and
bony/metallic fragments are easily achieved. Assessment for acute hemorrhage
and mass effect is optimal.
The routine cranial CT protocol should
include contiguous sections, 5-10 mm thick, from the skull base through the
vertex, displayed at 3 window/level settings, as follows:
- Bone: W-3000, L-800
- Brain: W-90, L-40
- Subdural or intermediate: W-200, L-50
Contrast infusion is rarely indicated
in the search for mass lesions or vascular pathology, except in patients with
a history of human immunodeficiency virus infection and neurological
examination abnormalities.
Magnetic resource imaging
MRI is valuable in the subacute setting following initial resuscitation (eg, child abuse, shearing injuries), as well as for
identifying subtle abnormalities (eg, posterior fossa and brainstem injury, cortical contusions, shearing
injury) and as a method to date the injury (eg,
child abuse, parenchymal hemorrhage). Appropriate
patient monitoring, however, is difficult and unreliable due to strong
magnetic fields, time-varying magnetic gradients, and restricted access to
the patient. Patient motion, due to the extended imaging time, reduces the
chances of obtaining studies adequate to achieve final diagnosis. Faster
machines and sequences, as well as MRI units that are more open and
comfortable for unstable or acutely injured patients, are expected to improve
the imaging process in the future.
The routine MRI protocol varies
considerably based on strength of the unit's field, machine capabilities, and
suspected diagnosis. Most centers perform sagittal
T1-weighted and axial T1- and T2-weighted sequences of the brain routinely,
with the addition of specific additional sequences depending on the clinical
indications. T2-weighted gradient echo sequences are more sensitive for subacute/chronic parenchymal
hemorrhage/shearing injuries, while fluid-attenuated inversion recovery
(FLAIR) sequences have been shown to be more sensitive for subtle subarachnoid blood. Magnetic resonance angiography and venography, diffusion and perfusion imaging, and
spectroscopy may all be valuable in selected circumstances.
Conventional catheter angiography
Depending on practice patterns at
individual centers, consider conventional catheter angiography in patients
with penetrating trauma, subarachnoid and parenchymal hemorrhage, or stroke, both as a diagnostic
test and as a treatment option.
Conventional radiography
Conventional radiography has no role in
the evaluation of the patient with acute head injury. In any case where skull
radiographs may be requested, keep in mind that CT is significantly more
sensitive for soft tissue injury and is superior for spatial localization and
assessment of bony alterations.
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TYPES OF INJURY
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Section 6 of 8
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Epidural hematoma
The dura
mater is composed of 2 layers closely invested with each other: the visceral
or meningeal layer, which lines the intracranial
space; and the parietal layer, which functions as the periosteum
of the calvarium. The dura,
therefore, adheres tightly to the cranial sutures.
A skull fracture that crosses an
arterial branch may bleed into the closed space between the calvarium and the periosteal
layer, forming a homogeneously high-density lens-shaped or biconvex
collection, termed epidural hematoma (see Images 1-2).
Because of the transmitted arterial pressure, epidural hematomas
tend to continue to enlarge, with resultant increasing mass effect (ie, lucent interval). Since the dura
splits to encase the major venous sinuses and form the falx
cerebri and tentorium cerebelli, inward displacement of the superior sagittal or transverse sinus indicates an epidural
process. Venous epidural hematomas occur when the
fracture disrupts one of the sinuses and occur more commonly in the posterior
fossa (see Images 3-4).
Subdural hematoma
The subdural
space is bound externally by the meningeal layer of
the dura and internally by the arachnoid
mater. Hematomas are confined by the reflected dura of the tentorium and falx but easily spread into the intervening potential
space to form crescentic or convex-out/concave-in
collections called subdural hematomas
(see Image
5). Tearing of the bridging cortical veins that traverse this space
accounts for most subdural hematomas,
usually from abrupt acceleration/deceleration injury. This is more likely to
occur in elderly patients and other patients with atrophy, where the subdural space is enlarged.
Acute hemorrhage is dense on the brain
windows, assuming normal hematocrit. As blood ages,
it becomes less dense, so that by about 7-10 days, it approximates the same
density as adjacent brain tissue. At this stage, the isodense
subdural hematoma (see Image 6)
is described. Careful inspection of the subdural or
intermediate windows usually shows inward displacement of the cortical
gray/white matter junction and mass effect, otherwise unexplained by the
imaging findings. Contrast enhancement of the bridging veins may define the
collection (see Image 7).
Homogeneous density within a subdural collection
generally represents interval hemorrhage into a preexisting chronic subdural hematoma.
Subarachnoid hemorrhage
The subarachnoid
space extends between the subdural space and the
cortical/pia mater surface of the brain. Hemorrhage
into this space interdigitates with the sulci and gyri of the brain
(see Image
8). Focal dense clot often signifies the location of hemorrhage,
particularly in patients with aneurysm rupture. More subtle or diffuse
bleeding is often due to cortical contusion, dilution from a focal
collection, or intraventricular hemorrhage due to
delayed presentation. Catheter angiography is usually indicated on an
emergency basis to identify cerebral aneurysms and define their anatomy prior
to surgical intervention (see Image 9).
Parenchymal lesions
Focal cortical hemorrhage is common as
a sequela of head trauma and may be multifocal, as in coup and contrecoup
injuries, or diffuse. Focally dense gyri with
subjacent edema, particularly those adjacent to the inner calvarial
structures (ie, orbit roof-frontal pole, petrous
ridge, and sphenoid wing-temporal pole) represent contusions (see Images
10-11).
Diffuse axonal injury, caused by
shearing of the white matter, is due to the differing density or fixation
between two structures and the differing response to rotation and
deceleration. The lobar white matter, brainstem, and corpus callosum are most often affected, with focal ovoid or
elongated regions of decreased density.
Cerebral edema may result from loss of
normal autoregulation and hyperemia or diffuse
edema from other causes. Diffuse loss of normal sulci
and cisterns with small ventricles is noted (see Image
12-13). MRI is more sensitive than CT scanning for subtle injuries of
these types, especially in the subacute or chronic
phases. Children are most commonly affected; they have a 50% mortality rate,
3 times that of adults.
Parenchymal hemorrhage
Focal parenchymal
hematomas occurring in regions of end-arteries,
such as the basal ganglia, thalamus, brainstem, and cerebellar hemispheres, occur most frequently in
patients with chronic hypertension or hypertensive crisis, probably due to
spontaneous rupture of these tiny vessels. Less than 1% of such patients have
a radiographically definable lesion; thus,
angiography is rarely indicated. (See Image 14.)
Focal lobar parenchymal
hematomas, by contrast, are far more likely to be
secondary to a structural lesion, often an arteriovenous
malformation (AVM), vasculitis, or mass lesion (see
Image
15). If an appropriate clinical history has been obtained, angiography
(AVM) or contrast-enhanced MRI is the diagnostic procedure of choice prior to
surgical intervention, unless secondary mass effect is life threatening and
patient management decisions dictate otherwise (see Image 16).
Stroke
Patients with strokes in the emergency
setting may present a different course for decision-making. Acute occlusion of one or more large vessels results in focal,
wedge-shaped peripheral areas of loss of grey/white matter differentiation
involving the cortex and contiguous white matter, or simply as a focal mass
effect (see Image 17).
Anoxia or hypotension results in diffuse loss of gyral/cortical
markings and diffuse mass effect (see Image 18).
Such changes are exceedingly difficult
to appreciate on CT studies obtained acutely (<6-12 h from ictus). One
exception is the dense middle cerebral artery (MCA) sign, which represents
acute clot within the horizontal portion of the middle cerebral artery (see Image 19).
Patients with resolved neurologic deficits (ie,
transient ischemic attacks) rarely demonstrate acute pathology on CT
examinations without having sustained acute trauma. New MRI techniques allow
rapid identification and diagnosis in as little as 30 minutes from initial
insult. Recent brain injury protocols have shown excellent results in
treating such patients with intravenous or intraarterial
thrombolytic agents.
Child abuse
Child abuse merits specific mention
because of the severe morbidity and mortality of cranial injuries inflicted
in abusive settings and because of the possibility of intervention to spare
other household members further trauma. The key to diagnosis of child abuse
is repeated injury, which is present in the majority of victims. Presence of
hemorrhages of various ages and locations is pathognomonic
(see Images
20-22). Retinal hemorrhages, rib and long bone fractures, burns, and
other skin lesions are common. MRI is ideal for the evaluation of such
patients because of its superior sensitivity and ability to date the injuries
with accuracy. It further offers the benefit of not using ionizing radiation.
Penetrating trauma
CT is the diagnostic procedure of
choice for patients with gunshot wounds and other penetrating trauma. The
course of the projectile may be identified, and location of foreign bodies
can be noted. Hematomas and mass effect are easily
assessed. (See Images
23-27.)
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Caption: Picture 1. Emergency
neuroradiology. Axial CT scan, bone window, shows linear
skull fracture through the temporal squamosa
(arrow).
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Picture
Type: CT
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Caption: Picture 2. Emergency
neuroradiology. Axial CT scan, brain window, at the same
level as Image 1, shows left frontal epidural hematoma
(arrow) displacing the falx and brain posteriorly and to the right.
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Picture
Type: CT
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Caption: Picture 3. Emergency
neuroradiology. Axial CT scan through the posterior fossa shows a linear skull fracture of the occipital
bone (arrow), near the sigmoid sinus.
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Picture
Type: CT
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Caption: Picture 4. Emergency
neuroradiology. Axial CT scan at the same level as Image 3,
brain window, shows venous epidural hematoma
(arrow).
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Picture
Type: CT
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Caption: Picture 5. Emergency
neuroradiology. Axial CT scan though the level of the lateral
ventricles shows right-sided subdural hematoma along the convexity (red arrow) and falx (green arrow), with severe midline shift from
right to left.
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Picture
Type: CT
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Caption: Picture 6. Emergency
neuroradiology. Axial CT scan above the lateral ventricles
shows extra-axial material (arrow) of approximately the same density as brain
parenchyma, displacing the grey-white matter interface internally. Mild
midline shift is seen.
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Picture
Type: CT
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Caption: Picture 7. Emergency
neuroradiology. Axial CT scan with intravenous contrast
infusion, obtained at the same level as Picture 6, demonstrates the right isodense subdural hematoma (red arrow), enhancing veins (green arrow),
and enhancement of the membrane (blue arrow).
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Picture
Type: CT
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Caption: Picture 8. Emergency
neuroradiology. Axial CT scan at the level of the mesencephalic cistern shows subarachnoid
hemorrhage in the left sylvian fissure (green arrow)
and the ambient cistern (red arrow). At least part of the density in the
ambient cistern represents the aneurysm itself.
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Picture
Type: CT
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Caption: Picture 9. Emergency
neuroradiology. Cerebral angiogram, anteroposterior
projection, of a left vertebral artery injection demonstrates an aneurysm
of the tip of the basilar artery (arrow).
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Picture
Type: X-RAY
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Caption: Picture 10. Emergency
neuroradiology. Lateral scout image from a CT brain
examination shows linear lucency representing a
right posterior frontal skull fracture (arrow).
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Picture
Type: X-RAY
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Caption: Picture 11. Emergency
neuroradiology. Axial CT scan of the brain shows a right
frontal cortical gyriform contusion, with a small
amount of subarachnoid hemorrhage. Right scalp
soft tissue swelling is also present (coup lesion).
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Picture
Type: CT
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Caption: Picture 12. Emergency
neuroradiology. Axial CT scan, brain window, shows diffuse
low density and loss of grey-white matter differentiation throughout the cerebral
hemispheres (arrows), consistent with diffuse edema and swelling.
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Picture
Type: CT
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Caption: Picture 13. Emergency
neuroradiology. Axial CT scan, 24-hour follow-up postictus, demonstrates progression of swelling and
diffuse edema.
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Picture
Type: CT
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Caption: Picture 14. Emergency
neuroradiology. Axial CT scan shows sharply defined oval hyperdensity in the right lentiform
nucleus (arrow) representing an acute hypertensive-type hemorrhage. Minimal
edema is present in this acute setting.
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Picture
Type: CT
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Caption: Picture 15. Emergency
neuroradiology. Axial CT scan shows irregularly shaped
right frontoparietal acute parenchymal
hemorrhage (arrow).
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Picture
Type: CT
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Caption: Picture 16. Emergency
neuroradiology. Cerebral angiogram, lateral projection,
of a right internal carotid artery injection demonstrates a right frontoparietal arteriovenous malformation
(AVM), with prominent early draining veins (arrow) extending cephalad to the superior sagittal
sinus from the AVM nidus. (The patient is facing
to the left.)
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Picture
Type: X-RAY
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Caption: Picture 17. Emergency
neuroradiology. Axial CT scan shows a peripheral
wedge-shaped area of decreased density (arrow) involving the right caudate
head and lentiform nuclei, insula,
and frontal and temporal lobes, consistent with a subacute
right proximal middle cerebral artery occlusion and subsequent cerebrovascular infarction. A mild mass effect and
shift of the midline to the left is shown.
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Picture
Type: CT
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Caption: Picture 18. Emergency
neuroradiology. Stroke. Anoxia or hypotension results in
diffuse loss of gyral/cortical markings and
diffuse mass effect.
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Picture
Type: CT
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Caption: Picture 19. Emergency
neuroradiology. Axial CT scan at the level of the basal
cisterns shows the "hyperdense middle
cerebral artery (MCA) sign" (arrow) representing acute clot within the
right middle cerebral artery, accounting for the patient's clinical
symptoms.
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Picture
Type: CT
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Caption: Picture 20. Emergency
neuroradiology. Lateral scout image from a CT brain
examination shows linear lucency representing a
left parietal skull fracture
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Picture
Type: X-RAY
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Caption: Picture 21. Emergency
neuroradiology. Axial CT scan of the brain shows multiple
hemorrhages of multiple ages, pathognomonic for
child abuse. Hyperdense hemorrhage is seen in several
left-sided chronic subdural loculations
(red arrow). Right extraaxial fluid collection
exerts mass effect (green arrow) and indicates prior, chronic subdural hematoma/hygroma,
with acute hemorrhage dependently (blue arrow). Also, a small amount of interventricular blood is present in the atrium of the
right lateral ventricle.
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Picture
Type: CT
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Caption: Picture 22. Emergency
neuroradiology. Axial CT scan of the brain at a higher
level shows the left parietal skull fracture (arrow) seen on the 'scout'
image. Absence of bone anteriorly is the anterior
fontanel, with visualization of the posterior portion of the sagittal suture noted in the midline posteriorly.
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Picture
Type: CT
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Caption: Picture 23. Emergency
neuroradiology. Lateral scout image from a CT scan of the
brain shows a metal bullet overlying the expected location of the suprasellar cistern.
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Picture
Type: X-RAY
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Caption: Picture 24. Emergency
neuroradiology. Axial CT scan of the brain at the level of
the suprasellar cistern shows severe streak
artifact from the hyperdense metal bullet (arrow).
The bullet entered from a right temporal location (right temporalis muscle swelling) and traveled to the midline
(linear horizontal hyperdensity).
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Picture
Type: CT
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Caption: Picture 25. Emergency
neuroradiology. Lateral scout image from a CT scan of the
brain shows linear metal ice pick (arrow at ice pick point in the suprasellar cistern) overlying the anterior cranial fossa.
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Picture
Type: CT
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Caption: Picture 26. Emergency
neuroradiology. Axial CT scan of the brain at the level of
the suprasellar cistern shows the path of the
distal portion of the ice pick (arrow), extending the suprasellar
cistern in the midline. This is the expected location for the internal
carotid artery bifurcation.
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Picture
Type: CT
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Caption: Picture 27. Emergency
neuroradiology. Anteroposterior
projection of a right common carotid artery angiogram shows the close proximity
of the ice pick (arrow) and the internal carotid artery bifurcation into
the anterior and middle cerebral arteries.
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Picture
Type: X-RAY
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BIBLIOGRAPHY
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Section 8 of 8
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