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CT of the brain

2nd year BSc students
by

Victor Micallef

on 30 May 2014

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Transcript of CT of the brain

CT of the BRAIN
Indications
Shunt check
Neurological deficit

Drug toxicity
Fits
Syncope
Diagnostic Task
detect blood collections
identify brain masses
detect brain oedema or ischemia
detect calcifications
evaluate fractures of skull
detect IC air

Key Elements
Patient Positioning

Sequential vs Helical

Use of Contrast

Radiation
Tube current modulation may be of little use
Supine / Head first into gantry
Head in Head holder with immobilization straps
Table height: External Auditory Canal in centre
Scan Angle parallel to base of skull
avoid exposure to occular lens
Scan range
From top of C1
To top of calvarium
•Infections and abscesses
•Tumours (primary or metastatic)
CT angiography
• Aneurysm
• Thrombosis
• dissection
the decision of axial vs helical is influenced by
the patient
indication
scanner capabilities
image quality requirements
CT Anatomy
A. Orbit
G. Cerebellar Hemisphere
A. Frontal Lobe
F. Cerebellum
I. Occipital Lobe
G. Straight Sinus
G. Superior Sagittal Sinus
D. Superior Sagittal Sinus
HEAD INJURY
45%
26%
17%
Skull Fractures
linear
depressed
dura mater
2 layers of dense fibrous tissue
outer layer instead of periosteum (inner skull)
inner layer provides a protective covering for brain and spinal cord
the two layers are closely adherent except where the inner layer sweeps inwards between the
cerebral hemispheres (falx cerebri
between cerebrum and cerebellum (tentorium cerebelli)
results from injury of small arteries of veins on the surface of the brain
ruptured blood vessels bleed into the space between pia and arachnoid
Subarachnoid haemorrage
appears as high density in sulci or fissures
most common cause is trauma
2nd most common cause - rupture of aneurysm
may need CTA to determine
Acute subdural
Deceleration and acceleration or rotational forces that tear bridging veins can cause an acute subdural hematoma.
The blood collects in the space between the arachnoid mater and the dura mater.
The haematoma on CT has the following characteristics:
•Crescent shaped
•Hyperdense, may contain hypodense foci due to serum, CSF or active bleeding
•Does not cross dura
Subacute Subdural Hematoma
A subacute SDH should be suspected when you identify shift of midline structures without an obvious mass.
Subacute SDH may be difficult to visualize by CT because as the haemorrhage is reabsorbed it becomes isodense to normal grey matter.

Weakness / paralysis of a limb or the entire body
Impaired hearing or vision
Loss / disturbance of sensation
Impairment or loss of speech
Fixed dystonia, unlike normal dystonia
Tremor, myoclonus, or other movement disorders
Gait problems
Functional neurological deficit can present with any motor or sensory symptom in the body including:
confusion
amnesia
loss of alertness
loss of orientation (self, time, or place)
defects in judgment or thought
poor regulation of emotions
disruptions in perception
psychomotor skills
behavior.
Change in mental status refers to general changes in brain function
Overbeaming is the excess dose per rotation that results if the penumbra falls outside the active detector area and does not contribute to the image
Over ranging is the increase in DLP due to the additional rotations at the beginning and at the end of a spiral scan
F. Cerebellar Hemisphere
E. Mastoid Air Cells
D. External Auditory Canal
C. Temporal Lobe
B. Sphenoid Sinus
A. Frontal Lobe
B. Frontal Bone (Superior Surface of Orbital Part)
C. Dorsum Sellae
D. Basilar Artery
E. Temporal Lobe
F. Mastoid Air Cells
G. Cerebellar Hemisphere
F. Fourth Ventricle
E. Midbrain
D. Suprasellar Cistern
C. Temporal Lobe
B. Sylvian Fissure
A. Falx Cerebri
B. Frontal Lobe
C. Anterior Horn of Lateral Ventricle
D. Third Ventricle
E. Quadrigeminal Plate Cistern
A. Anterior Horn of the Lateral Ventricle
B. Caudate Nucleus
C. Anterior Limb of the Internal Capsule
D. Putamen and Globus Pallidus
E. Posterior Limb of the Internal Capsule
F. Third Ventricle
G. Quadrigeminal Plate Cistern
H. Cerebellar Vermis
A. Genu of the Corpus Callosum
B. Anterior Horn of the Lateral Ventricle
C. Internal Capsule
D. Thalamus
E. Pineal Gland
F. Choroid Plexus
A. Falx Cerebri
B. Frontal Lobe
C. Body of the Lateral Ventricle
D. Splenium of the Corpus Callosum
E. Parietal Lobe
F. Occipital Lobe
A. Falx Cerebri
B. Sulcus
C. Gyrus
linear fractures are more common
fractures must be distinguished from sutures
a skull fracture is clinically significant if it involves the sinuses or skull base
bone window is important
sutures
a fibrous joint which only occurs in the skull
it is normal for sutures to remain unfused at birth
the premature fusion of sutures is known as craniosynostosis
1 per 1800/2200 births
bones of the cranium
parietal
joined by connective tissue at these sutures
3d CT shows combined coronal and sagittal synostosis. Vertex view shows a normal lambdoid suture with complete fusion of the sagittal and coronal sutures.
In the UK
1% of all deaths,
25% of all traumatic deaths and
50 % of road traffic accident deaths are due to head trauma
Indications for post trauma brain CT
A fractured skull increases considerably the risk of associated intracranial damage. Skull base fractures and compound fractures further increase the risks.
4. The patient is drowsy or in a coma.
3. The patient is in a persistent confused state.
2. The patient has abnormal neurological signs and symptoms.
1.A fracture is seen on the plain skull x-rays.
A CT is even more urgent if the symptoms are worsening.
CT's most important role is in classifying post head trauma patients into one of three categories which are patients with;
3. diffuse pattern of brain injury
2. focal intra-axial or extra-axial haematomas
1. normal intracranial structures
intra-axial - within the brain itself
Intra-axial hemorrhages are more dangerous and harder to treat than extra-axial bleeds.
intraventricular hemorrhage(bleeding within the brain's ventricles)
includes intraparenchymal hemorrhage (bleeding within the brain tissue)
Diffuse injuries include brain injury due to hypoxia, meningitis, and damage to blood vessels.
Unlike focal injuries, which are usually easy to detect using imaging, diffuse injuries may be difficult to detect and define; often, much of the damage is microscopic.
• Swelling, commonly seen after TBI, can lead to dangerous increases in intracranial pressure.
• Vascular injury usually causes death shortly after an injury.
• Ischemic brain injury resulting from an insufficient blood supply to the brain, is one of the leading causes of secondary brain damage after head trauma.
• widespread damage to the white matter of the brain that usually results from acceleration/deceleration types of injury.
4. Air in the subarachnoid space or ventricles. Air usually enters the cranium through the cribriform plate region in the event of a compound injury.
3. Fluid in the mastoid or sinuses. Fluid in the sphenoidal sinuses suggesting a skull base fracture.
2. Scalp swelling
1. Foreign bodies in the scalp or intracranially
A CT examination will also reveal other findings related with head injury. This may include;
The mechanism of contusion can be classified into coup and contra coup
Contusions
a bruise on the surface of the brain.
Coup contusion
This happens because the trauma makes the brain move in relation to the calvarium and decelerates violently against the skull on the opposite side.
Contra coup
This results in torn capillaries, petechial haemorrhages and mechanical damage to adjacent neurons.
occurs at the site underlying the area receiving the trauma.
occurs at the opposite side of the area of the initial impact.
bleeding into the subarachnoid space—the area between the arachnoid membrane and the pia mater surrounding the brain
Symptoms of SAH include a severe headache with a rapid onset ("thunderclap headache"), vomiting, confusion or a lowered level of consciousness, and sometimes seizures.
Often in chronic subdural haematoma the patient does not recall any trauma or only minor head trauma
The vascular nature of the dural component makes it a source of repeated episodes of rebleeding.
As a result of bleeding into the subdural space, a thick membrane develops on the dural side and a thinner membrane develops on the arachnoidal side of the clot.
Develop over a period of days to weeks, often after minor head trauma, though such a cause is not identifiable in 50% of patients.
Since these bleeds progress slowly, they present the chance of being stopped before they cause significant damage.
The bleeding from a chronic bleed is slow, probably from repeated minor bleeds, and usually stops by itself.
They may not be discovered until they present clinically months or even years after a head injury.
5. dorsum sella
4. sphenoidal sinus
3. ethmoidal sinus
2. nasal septum
1. globe
6 - occipital bone
5 - lambdoid suture
4 - MASTOID AIR CELLS
3 - squamosal suture
2 - frontal bone
1 - temporal bone
7 - posterior cranial fossa
the caudate nucleus has been implicated with voluntary movement, learning, memory, sleep, and social behavior
A massive layer (8–10 mm thick) of white matter separating the caudate nucleus and thalamus (medial) from the more laterally situated lentiform nucleus (globus pallidus and putamen).
Internal capsule
The globus pallidus is a structure in the brain involved in the regulation of voluntary movement.
It is part of the basal ganglia, which, among many other things, regulate movements that occur on the subconscious level.
The globus pallidus
If the globus pallidus is damaged, it can cause movement disorders.
The main function of the putamen is to regulate movements and influence various types of learning.

The putamen also plays a role in degenerative neurological disorders, such as Parkinson's disease.
Functionally, the vermis is associated with bodily posture and locomotion.
vermis
It connects the left and right cerebral hemispheres and facilitates interhemispheric communication.

It is the largest white matter structure in the brain
The corpus callosum (Latin: tough body) is a wide, flat bundle of neural fibers beneath the cortex in the brain at the longitudinal fissure.
corpus callosum
The thalamus surrounds the third ventricle.
Some of its functions are the relaying of sensory and motor signals to the cerebral cortex, and the regulation of consciousness, sleep, and alertness.
The thalamus is a midline symmetrical structure of two halves situated between the cerebral cortex and the midbrain.
thalamus
Its shape resembles a tiny pine cone (hence its name), and it is located near the centre of the brain, between the two hemispheres
It produces the serotonin derivative melatonin, a hormone that affects the modulation of wake/sleep patterns and seasonal functions.
The pineal gland is a small endocrine gland in the brain.
pineal gland
serotonin derivative melatonin
The choroid plexus is a structure in the ventricles of the brain where cerebrospinal fluid (CSF) is produced.

choroid plexus
CSF is recycled (flushed) 4 times per day in order to clean out metabolites and toxins.
Hence the choroid plexus must produce about 500 milliliters of CSF daily
corpus callosum
The rostrum is the part of the corpus callosum that projects posteriorly and inferiorly from the anteriormost genu
splenium
The rostrum is so named for its resemblance to a bird's beak.
The posterior portion of the corpus callosum is called the splenium
The anterior is called the genu (or "knee")
Between the two is the truncus, or "body", of the corpus callosum.
The part between the body and the splenium is often markedly thinned and thus referred to as the "isthmus".
They receive blood from internal and external veins of the brain, receive cerebrospinal fluid (CSF) from the subarachnoid space, and ultimately empty into the internal jugular vein.
The dural venous sinuses (also called dural sinuses, cerebral sinuses, or cranial sinuses) are venous channels found between layers of dura mater in the brain.
Lobe
Lobe
Ventricle
Lobe
Dystonia is a neurological movement disorder, in which sustained muscle contractions cause twisting and repetitive movements or abnormal postures.
Change in mental status
psychological disorders
Signs of increased ICP
Headaches
Trauma
Haemorrhage
hydrocephalus
Brain herniation
New Growth
Post Op
Hydrocephalus
an abnormal accumulation of CSF in the ventricles, or cavities, of the brain.
This may cause increased intracranial pressure and progressive enlargement of the head, convulsion, tunnel vision, and mental disability.
Although it does occur in older adults, it is more common in infants
Hydrocephalus
Herniation can be caused by a number of factors that cause a mass effect and increase intracranial pressure (ICP):
Brain herniation
brain tumor.
intracranial hemorrhage,
brain injury,
these include traumatic
Brain herniation occurs when a part of the brain is squeezed across structures within the skull.
The brain can shift across such structures such as the falx cerebri, the tentorium cerebelli, and even through the foramen magnum in the base of the skull.
1) Uncal
2) Central
3) Cingulate
4) Transcalvarial
5) Upward
6) Tonsillar
Types of brain herniation
occipital
temporal
frontal
sagittal
coronal
metopic
lambdoid
squamosal
extradural hematoma
subdural hematoma
(white arrows)
(black arrows).
acute
chronic
Epidural or extradural hematoma occurs between the dura mater and the skull.


Epidural
extradural hematoma
The lens-like shape of the hematoma causes the appearance of these bleeds to be "lentiform."
Thus they expand inward toward the brain rather than along the inside of the skull, as occurs in subdural hematoma.
On images produced by CT scans they usually appear convex in shape because their expansion stops at the skull's sutures, where the dura mater is tightly attached to the skull.
Approximate effective dose is of 2mSv
Equivalent to 8 months background radiation
Low cancer risk:
1 in 10,000 to 1 in 1000
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