Term
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Definition
• Plain films
• Computed tomography
- With or without contrast
• MRI |
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Term
| Why Do We Image the Head? |
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Definition
- Trauma
• Blunt
• Penetrating
• Foreign bodies
- Infection
- Brain hemorrhage
• Stroke vs. intraparenchymal
- Neurologic changes |
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Term
| General Considerations and Notes for head imaging |
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Definition
• Routine radiography of the skull (X-ray) is nearly obsolete
• Plain skull X-rays only show bony structures
- CT or MRI may be a better choice depending on interest
• Order series based on area of interest |
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Term
| Approach to Radiographs of the head |
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Definition
• Systematic evaluation of the brain, skull, and maxillofacial structures:
- Bone density
- Evidence of
• Fracture
• Asymmetry
• Air-fluid level
• Obliteration of normal structure
• Tumor or lesion
• Foreign body
• Destruction
• Soft tissue evaluation |
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Term
| Another Way to Remember approach to head radiographs |
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Definition
• A: anatomic appearance and alignment
• B: bony mineralization and texture abnormalities
• C: calcifications
• S: soft tissue abnormalities |
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Term
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Definition
• Relies on the different attenuation of X-rays by tissue of various densities
• A three-dimensional image volume of image data is collected, then displayed as sagittal, axial, or coronal slices |
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Term
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Definition
- CT of the head has become an integral part of the emergency evaluation of a wide variety of conditions and chief complaints
• Trauma, stroke, seizure, altered mental status, headache, and fever
- Good to diagnose • Acute hemorrhages • Pneumocephalus
• Foreign bodies
• Bony abnormalities
• Edema
• Mass effects |
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Term
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Definition
• Radiation
• Frequency of scans
• Repeated scans
• Trauma patients |
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Term
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Definition
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Term
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Definition
- Provides information about
• Hemorrhage
• Mass-effect
• Ventricular abnormalities such as hydrocephalus, cerebral edema
• Sinus abnormalities • Fluid opacification
• Bone abnormalities • Fractures or lytic lesions |
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Term
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Definition
- Usually performed after the noncontrast CT
• Evaluation for: • Infection (meningeal enhancement, abscess) • Tumor (mets)
• Contrast head CT is significantly inferior to MRI for these indications • The only exception is CT angiogram of the head for evaluation of aneurysm, thrombosis, or dissection |
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Term
| Hounsfield Units and Windows |
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Definition
-Brain windows allow inspection of soft tissues, brain, hemorrhage, and CSF spaces. Bone is obscured, but some gross fractures may be seen. CSF and air appear black.
-Bone windows give detailed information about fractures but obscure soft tissue.
[image] |
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Term
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Definition
- Distortion of the size or position of normal brain structures when they are displaced by an abnormal structure or volume
• Due to tumor, hemorrhage, edema, or obstruction of CSF fluid flow
- “Midline shift”
• Measure of severity of distortion
• Linked to probability of death after traumatic brain injury |
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Term
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Definition
• Motion
• Metallic streak artifact
- May make it difficult to impossible to identify pathology in the region |
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Term
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Definition
| This photograph here, these are lesions right here. This is somebody with multiple myeloma. These are the punched out lesions that you see in the skull or in the ribs or in other bones due to the multiple myeloma due to that malignancy of the plasma cells in the blood |
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Term
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Definition
| So let me show you an example here. A is a brain window. You can see all the brain. You can see the soft tissue. You can actually see the bleed there, the hematoma. This side is a bone window. Now, this is the same patient. Remember I highlighted out where the bleed was there, the hemorrhage? Look what it's due to. There's a fracture right there. So bone windows versus brain windows. |
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Term
| radiation exposure from ct |
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Definition
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Term
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Definition
Now, mass effect can also be noted, and this will cause distortion of the size or the position of normal brain structures. Normally, as you can see in this first photo right here, this is normal. Everything's midline. You can almost cut it right down the middle, which they've done, and you see the same image. You could almost fold that image over on it, and it would be exact duplicate. Everything is midline. Everything is fine.
Now, in A, you can see this midline-- and B, you can see it, as well. You see this midline shift. So once again, this person has this bleeding here, and this pressure has caused everything to shift over. So these ventricles that are right here and right here have now gone way over here. So this is called the midline shift, and it can be very serious. It tells you about the severity of the disease. And it's linked to probability of death after traumatic brain injury. The more the shift, the worse off it is.
And here's a case where here's the bleed on this side, and now it's shifted everything over. And they've drawn the lines in there, the little white-dashed lines. Those are where the midline should be. So you can do a pretty good job of picking up mass effect. |
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Term
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Definition
The thing we do worry about, though, with CT scans is artifact, whether the patient is moving or especially metal. If somebody has a metal earring on or ear piercing, that can really distort.
And you see all these lines coming out, these white lines? That's all the distortion from the metal. So you need to make sure that if you're going to do a CT scan, that there's no metal around, because it will cause these distortions. |
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Term
Approaching the Head CT
• Mnemonic: |
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Definition
• A: Air-filled spaces
- Infections, fractures
• B: Bones
• B: Blood
- SAH, epidural, subdural, intraparenchymal
• B: Brain
- Infarction, edema, masses, shift
• C: CSF spaces
- ICP, atrophy, hydrocephalus, edema |
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Term
|
Definition
- Appearance
• Normally air filled and black with no air fluid levels
- Significance:
• Air-fluid levels or opacification in the setting of trauma
may indicate fracture
• In the absence of trauma, air-fluid levels or mucosal thickening may be too sensitive • Should not be equated with bacterial sinusitis in the absence of clinical evidence
• Mastoid opacification without trauma indicates mastoiditis |
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Term
|
Definition
Normal air-filled spaces in brain window: A—maxillary sinuses
B—mastoid air cells
C—ethmoid sinuses
D—sphenoid sinuses E—frontal sinuses |
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Term
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Definition
• In the setting of trauma, inspect for fracture • “Rings” break at two or more points
• Pneumocephalus (more later) |
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Term
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Definition
Now, when it comes to bones in the setting of trauma, make sure you inspect these for a fracture. And remember, this is a ring and rings break in two or more points. You don't-- as I talked about earlier, if you try to break a Lifesaver, you cannot just break one part of the Lifesaver. You always break somewhere else. And also look for pneumocephalus. We'll talk more about that later, but that's air in the brain and that can happen with a fracture.
So a couple of things I want to point out here. We'll blow these up a little bit. Here you can see the fracture there and the fracture there. So you've got your two fractures. Let's move over.
Here's more of a sinus or an orbital film. You've got a disruption of bone cortex there and bone cortex there. I'm going to erase those to make it a little clearer. See where that arrow is, that one right there? That little pouching down that's right there? That's actual tissue going into the sinus from the fracture.
And then this one-- let's go to this last one. You've got a fracture of the bone there and you've got a fracture of the bone there. So it's very good, if you do the bone windows, at picking up fractures. The other also can pick up some fractures. But if you're really worried about fractures, you need to get bone film. |
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Term
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Definition
| Now, this one is kind of interesting. You've got both here. You've got a brain window and a bone window. You can see the trauma right there and right there. See this pathway right here? That's a projectile. That's a gunshot. And you can see all of the fragments of the bullet spread throughout the brain. So point of entry was here. It actually went all the way through and caused another fracture on the other side. Doesn't look like the bone actually exited, but it did go through to cause another fracture. |
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Term
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Definition
• Hemorrhage can occur in any of several spaces within or around the brain
• The shape and density of blood collections on CT depend on a number of factors • Age of the blood products • Anatomic location
• Recent hemorrhage appears as a bright white color on non-contrast CT
- As time elapses, blood changes to a darker color • Indicating lower density
- This is likely due to a number of factors • Absorption of water by hematoma |
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Term
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Definition
- Blood in the subarachnoid space
• Including the sulci, Sylvian fissure, ventricles, cisterns
- Appearance: white on brain windows
• CT is most sensitive for blood in the first 12 hours after
the event (95%)
- Location: localized or diffuse
• Assumes shape of its surroundings
• Suspect increased ICP and look for signs of diffuse edema |
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Term
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Definition
Diffuse Subarachnoid Hemorrhage
Blood appears bright white and fills the sulci as well as the cisterns, Sylvian fissures, and lateral ventricles.
A—blood in basilar cistern
B—blood in Sylvian fissure
C—blood in posterior horns of lateral ventricles
D—blood in sulci
E—calcified choroid plexus, not an uncommon finding
-look for fluid levels- remember pt horizontal |
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Term
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Definition
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Term
|
Definition
• Blood located outside the dura mater
• Rapid enlargement may occur, leading to mass effect and possible herniation
- Middle meningeal artery
- Look for mass effect
- Look for skull fracture
• Usually located temporally
• Has a biconvex disc or lens shape |
|
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Term
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Definition
Epidural hematoma-- this is blood located outside the dura. Rapid enlargement may occur, resulting in the mass effect and possible herniation. This is usually a rupture of the middle meningeal artery. You want to look for mass effect again. You can actually see it and I'll show you that in a second, usually located temporally. And they have a biconcave disc or lens shape appearance.
So let me blow this up. Here's the epidural hematoma right there. And you can see some mass effect as it's starting to move some things over just a little bit. But there's that nice biconcave disc. |
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Term
|
Definition
A—temporal bone fracture B—suture lines
C—mass effect
D—“swirl” sign, indicating
active bleeding E—small ventricle F—no visible sulci
E and F indicate increased intracranial pressure
We've got another example of it for you here. So here we have a temporal bone fracture due to the trauma. There's the hematoma outlined right there. So there's the mass effect. The dotted white line should be the midline, and look at the ventricles have been pushed over. And they're much smaller than they should be.
Now, you see this thing called the swirl sign inside here. It's pointed out as D. Let me get rid of that. That actually-- and it kind of looks like there's change in colors there, like there's a swirling. There's dark, there's white, there's all these. That swirl sign-- and I wouldn't be too excited if you couldn't pick that up routinely. That indicates active bleeding. So this person is still bleeding into that site.
An epidural hematoma develops, usually, from rupture. Again, in summary, the middle meningeal artery can bleed. There's the blood formation there. And it can cause some abnormalities on eye exam with dilation of one eye. And once again, the test of choice is the CT scan. |
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Term
|
Definition
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Term
|
Definition
• Accumulation of blood in the subdural space caused by venous bleeding
• Cause is head injury with latency between the event and the symptoms
- Headache, confusion, stupor, coma, delirium, hemiparesis, epilepsy
• Usually due to trauma to bridging veins
• Although slower to develop in size, they can lead to mass effect and herniation like EDH
• Have a variable appearance • White to gray
• Have variable location
[image] |
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Term
|
Definition
A—crosses suture lines B—mass effect C—small ventricles D—no visible sulci
And you can see here, there's the subdural bleed in that subdural space. And once again, this would be diagnosed best by a CT scan. So this is usually due to trauma, usually slower to develop in size. They can lead to some mass effect, herniation, like an epidural hematoma. But the appearance can be variable. And what you get is you get this-- instead of a concave, you get this kind of convex-- let me erase that. You get kind of a convex, but this is your hematoma right there.
Once again, you can see the mass effect. The dotted line is midline. And look at those ventricles are being shifted over. |
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Term
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Definition
| So here's another one with a subdural hematoma. First is acute. There's your bleed right there. It's kind of got this convex appearance. Then you get an isodense subdural, and then some people can develop chronic subdurals. What I really want you to notice here-- look how white the bleeding is here. And over time it's lost the water and it becomes darker over time. |
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Term
|
Definition
• Occurs within the substance of the brain matter
• May occur from trauma or spontaneously from HTN
• Usually appears as bright white
• Has a variable location
• May be round or irregular in shape
• May cause mass effect or herniation
- Look for midline shift |
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Term
|
Definition
Now, you can also have an intracranial hemorrhage. This occurs within substances of brain matter, can occur from trauma, can occur spontaneously from poorly controlled hypertension. And this usually appears as bright white. And you can see it right there.
The locations are variable. It really depends on where the bleeding occurred. Can be round, be irregular. May cause some mass effect. If we look here, this one is. It's shifted part over. So once again, look for mass effect. Look for herniation. Not so much you can look for herniation, you can see it on your patient. If they herniate their brain, they pull their brainstem down into their spinal canal where it doesn't have the room it needs, and that can lead to decreased respiratory function. |
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Term
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Definition
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Term
Brain
• Abnormalities include |
|
Definition
• Neoplastic masses
• Abscesses
• Infarction
• Vasogenic edema
• Global edema
• Diffuse axonal injury |
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Term
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Definition
• Best delineated on contrast CT or MRI
• Vasogenic edema often seen on noncontrast CT
• Due to immature vessels
• Caused by neoplasm secretion of vascular endothelial growth factor |
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Term
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Definition
| Now, masses-- these are best delineated out on contrast CT or MRI. Now, vasogenic edema often is seen in noncontrast CT, due to immature vessels, and caused by neoplasm excretion of these endothelial growth factors. And you can see here you've got a lesion, and you've got some edema that surrounds it. So massive facts-- once again, contrast CT or MRI are probably the best. |
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Term
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Definition
• May appear on noncontrast CT as hypodense region, possibly with air
• “Ring enhancement” |
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Term
|
Definition
When it comes to abscesses, they may appear on noncontrast CT as these hypodense regions, possibly with air, with ring enhancing. And what I want to show you here-- blow these up-- you can see this ring around this abscess, that white ring. That's the ring enhancing. And you can see it here, as well. That's the ring enhancing that you can see.
Now, that can be seen with abscesses, but you can also see it with some cases of lymphoma that go to the brain. You can see this ring enhancing. One of the infectious agents that can cause this quite often is an organism called toxoplasmosis, that we often see. It's found in cat litter. Cats carry it. And we find it a lot in patients who are HIV positive or have AIDS. |
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Term
| Ischemic Stroke and Infarction |
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Definition
• At the initial onset no abnormal findings on CCT
• Early ischemic changes can be seen within 3 hours of
stroke onset (85% of strokes)
• Ischemic brain looks hypodense (darker) than normal brain in the same anatomic region |
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Term
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Definition
Now, ischemic stroke and infarct-- at the initial onset, you may not see any initial abnormal findings on a CT scan. And that's OK, OK? This is something, then, we're going to do serial CT scans of the brain maybe once a day or after a couple of days.
But early ischemic changes can occur within three hours of the stroke onset. And this we see in about 85% of stroke. And I've got them highlighted there for you in circles and black. The ischemic brain looks hypodense, or darker, than the normal brain in the same anatomical location. And you can see all of these show darker pigmentation or more hypodense areas than the other brain. This would be an ischemic stroke, or infarct. |
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Term
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Definition
The progression of ischemic hypodensity may progress, with the amount depending on the degree of ischemia and collateral circulation
Now, you can get the progression of this ischemic hypodensity may progress with the amount depending on the degree of ischemia and collateral circulation. So this is the same person. See here, on day two, the density area. Now look on day four. It's spread a little bit, and it's even become more dense. So there's probably been some continued bleeding into that area. |
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Term
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Definition
- Many pathologies
• Trauma, anoxic brain injury, CO poisoning, electrolyte
abnormalities
- Two types of cerebral edema
• Vasogenic—extracellular accumulation of fluid • Associated with malignancy and infection
• Cytotoxic—represents cellular edema • Associated with cerebral ischemia
• As the brain swells, several changes occur
- Cerebrospinal fluid spaces collapse
- Lateral ventricles become slit-like
- Sulci become effaced
- Cisterns surrounding the brainstem become compressed and the risk of herniation increases
• As intracranial pressure rises, cerebral perfusion pressure falls, and global brain ischemia occurs |
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Term
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Definition
| So here's somebody who's just got cerebral edema. You can see over the different cuts here-- normally, these ventricles are much larger; and don't even see a ventricle on that side. Everything is kind of pushing in, and you get that diffuse changes that you would expect to see, this edema throughout the brain. |
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Term
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Definition
[image]
So here's a better example, a little more specific of vasogenic edema, the closed white arrow. This person has a glioma actually, a brain tumor. And you can see. And that's all what this is all through here. OK? And you can see the shifting of the substances of the ventricles. And then the other side is the cytotoxic edema, or once again, the open white arrow, in a person with ischemic infarct. Both of these show increased intracranial pressure with the dotted lines, because everything is shifting over. |
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Term
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Definition
• Result of deceleration injuries
- Especially in high-speed motor vehicle collisions
• Most frequent cause of persistent vegetative state following trauma
• Result of rotational shear injuries that most often occur at the gray-white matter junction
- Extent of injury is usually worse than that depicted by imaging
• Brainstem function is typically unaffected
• 50–89% of patients with DAI may have a normal CT scan on presentation
• Small petechial hemorrhages
- Gray-white matter junction and corpus callosum
- Occur in only about 20%
• Small focal areas of decreased attenuation secondary to edema |
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Term
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Definition
| So here's a case of diffuse axonal injury. 50% to 89% of patients with diffuse axonal injury may have a normal CT scan. But you can see throughout here some small petechial hemorrhaging at the white-gray matter junctions; occur in only about 20%. And then you get these focal areas of increased-- or decreased attenuation secondary to edema. So you can just see, throughout this entire brain here, there's issues. That's diffuse axonal. You don't see that nice, sharp separation between white and gray matter that you would see with a normal CT. |
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Term
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Definition
• Presence of air or gas within the cranial cavity
• It is usually associated with disruption of the skull
- After head and facial trauma
- Tumors of the skull base
- After surgery |
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Term
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Definition
| Now you can also get pneumocephalus. This is air or gas within the cranial cavity. And there shouldn't be any. If you see this, somewhere there's a disruption in the skull, OK? So there's been head trauma or facial trauma, a tumor, or after surgery. Let me blow these up. All this black right there-- that's all air. All of these are all air. In this photo, this is all air. And that's not something you want to see. |
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Term
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Definition
• Calcified choroid plexus
- Do not confuse with
hemorrhage
- Have a typical location |
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Term
|
Definition
• This is critical when other pathology is found
• Sulci (CSF spaces between the gyri) should
appear black
- Normal sulci are visible but not prominent, with a thin ribbon of CSF outlining the entire brain
• The size of the ventricles should be noted
- Increased volume
• Brain volume should be noted
- Decreased volume |
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Term
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Definition
[image]
Now, CSF spaces-- this is critical when other pathology is found. You've got to look at the sulci, which is the CSF spaces between the folds in the brain. These should appear black. The sides of the ventricle should be noted, the normal volume. And the brain volume should be noted, because sometimes you'll see atrophy of brain.
And let me show you an example of that. So the top photo is normal brain, and the bottom is atrophy. And you can see the actual brain tissue-- well, actually, it might be easier to outline. All what's in black-- that's all expansion into normal brain tissue. So you can see the amount of black that we would normally see in a normal brain above is now much different. This is all atrophy. The brain structure itself, the brain tissue, is actually decreasing in size and being filled in with these other spaces.
Same thing here-- look at how these sulci, or the ventricles, and look at how much more there is. Even on the periphery here, you barely see the little black lines. Look how much these are indented here. So that's pretty severe brain atrophy. |
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Term
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Definition
[image]
And then this is just a case of hydrocephalus on top. Hydrocephalus is where you get increased spinal fluid production, and that fills the ventricles. And the ventricles become bigger. And there's our little calcified choroid plexus again; and then edema-- once again, diffuse edema throughout the brain all through here. |
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Term
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Definition
| The first one is a 72-year-old female. She fell three weeks ago. She's having progressive lethargy and confusion. And there's something wrong right there, causing this shift over. This person actually has an epidural hematoma. |
|
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Term
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Definition
| that's a 58-year-old with a 62-pack history of smoking-- so longtime smoker-- with a seizure six hours ago. And he has a mass, a brain tumor, probably metastatic. OK? He probably has lung cancer, and now that's spread to his brain. And it's this lesion right here that led to the seizure. |
|
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Term
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Definition
| And then here's just another case of somebody with really severe cerebral edema-- not too bad that it didn't cause much mid-line shift. |
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Term
| Sinus CT, facial CT, or orbital CT |
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Definition
- May provide more detail
• Providing thinner slices through the region of interest
• Changing the patient’s position in the scanner during image acquisition |
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Term
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Definition
| Now, here's a sinus CT scan. So let's go through some of those, or what they look like her. And we've looked at some of these other places. Anything black is all air-filled sinuses. So these are all normal. And we talked about these in a previous section when we talked about sinusitis and sinus infections. |
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Term
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Definition
| You can do a facial CT scan, where you can put all of this together and piece them all together, looking at structures of bones, and foreign bodies, and things like that. This is not something, once again, that's going to be routinely done in most community hospitals or routine hospitals. |
|
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Term
| Intraocular Foreign Bodies |
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Definition
• Projectile objects
- Hammering metal on metal
- High speed grinders
• Patient may not be aware of
injury
• Avoid MRI |
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Term
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Definition
And let's blow these up, and let me show you here. Here's the foreign body in there eye, and here's the foreign body in that eye.
Actually, an interesting thing-- this right here-- that-- that's actually the lens to the eye. And then this and this on the side-- I'll erase those. Those are actually the extraocular muscles that control the movement of our eye. |
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Term
• 29-year-old male
• Involved in altercation
• Complains of midface pain and ecchymosis under left eye
[image] |
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Definition
So we have a 29-year-old male who was involved in the altercation, now comes in complaining of midface pain and ecchymosis under the left eye. So one of the things you're thinking about is going to be, oh, my gosh, maybe there's an orbital fracture. Maybe he got punched in the eye, and now he has a periorbital fracture.
Well, what we did see when we scanned this guy is we found this soft-tissue mass. His orbits were fine, but what we found is this soft-tissue mass in the bottom of his mouth. And that got us a little bit nervous.
We took some other views at the same time, and we see that same mass right there. I guess I don't need to highlight it. It's already highlighted for you. And we had no idea what this was.
We actually got the radiology report, and it showed a high-attenuated mass measuring 18 millimeters in its greatest diameter posterior to tooth 22. And it measured on these units these units we use in CT scan. It measured 130, with blood being usually, around 100. So we weren't quite sure what this could be.
This was a trauma patient. So we actually went and talked to the patient. And lo and behold, when we examined and opened his mouth, we found a piece of Juicy Fruit gum. He had been chewing gum when he got hit. The gum lodged in the bottom of his mouth, next to his tooth. And that's what we had CT scanned.
So you never know what you're going to see. So examine the patient, and take a look before you start ordering all these massive tests. |
|
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Term
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Definition
| Cerebral angiography is most useful in evaluating carotid, cerebral, and vertebral arteries |
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Term
| Magnetic Resonance Imaging |
|
Definition
- Images by using radiofrequency pulses in a defined sequence through a magnetic field
• Causes protons to become “excited” then “relaxed”
• The change from excited to relaxed state releases energy • Received by the scanner and a computer-generated image is formed
- Each tissue releases its energy at two different relaxing rates (T1 or T2)
- Different tissue releases energy at different rates • Forming the basis for differences in contrast |
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Term
|
Definition
| better differentiation between gray and white matter as well as imaging in different planes |
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Term
|
Definition
So MRIs allow for better resolution and differentiation between gray matter and white matter. And you can image a bunch of planes. Now, we're not going to go through anything really in any detail related to MRI imaging. It's above what we'd typically expect to cover in a curriculum like this or in PA school. You'll get a chance to look at some of these on rotations.
But really, we want you to feel comfortable with looking at some of the things you see in CT scans of the brain more than MRIs. But I do want you to realize that MRIs are great for picking up differences in white and gray matter and looking for tumors. |
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Term
| MRI Protocols are designed to demonstrate certain abnormalities better than others |
|
Definition
- T1 weighted images
• Anatomic details and make distinctions between solid
and cystic structures
- T2 weighted images
• Display pathologic changes better |
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|
