Neuro Radiology Flashcards
What is going on in this patient’s noncontrast CT?
This is also subarachnoid hemorrhage, it is just at a lower level!
Don’t let them trick you by giving you an out-of-frame view of a subarachnoid hemorrhage
What is going on in this patient’s noncontrast CT?
To be honest this is tricky, it looks a lot like a single calcified mass.
But this particular patient has an intraventricular hemorrhage. These occur due to tearing of subependymal veins.
The best place to look for intraventricular hemorrhage is in the occipital horns of the lateral ventricles. Commonly associated with injury to the corpus callosum. It should be noted that the choroid plexus often calcifies and thus can look quite dense, and should not be mistaken for intraventricular hemorrhage.
What is going on in this patient’s noncontrast CT?
This patient has intraparenchymal hemorrhage
It can be due to trauma as well as other causes such as hypertensive hemorrhage, a hemorrhagic stroke, a ruptured AVM, or a hemorrhagic neoplasm.
Major causes of the five main types of head bleed (epidural, subdural, subarachnoid, intraventricular, intraparenchymal)
- Epidural: Middle meningeal artery tear
- Subdural: Bridging vein tear
- Subarachnoid: Ruptured aneurysm
- Intraventruclar: Subependymal vein tear
- Intraparenchymal: No specific vessel, often in setting of trauma
Note that of all of these, only epidural and subarachnoid are arterial bleeds
What is going on in this C-spine CT?
Spinous process facture, aka Clay Shoveler’s fracture
An avulsion of the spinous process due to pulling from the trapezius muscle. Treatment consists of pain medication and physical therapy.
Five low-risk criteria for C-spine imaging
- C-spine imaging is required in all blunt trauma cases unless the patient meets all of these criteria:
- Absence of posterior midline cervical-spine tenderness
- No evidence of intoxication
- Normal level of alertness
- Absence of focal neurological deficit
- No clinically apparent painful injuries that might distract from pain of a cervical spine injury
Why is it subarachnoid hemorrhage specifically that can cause vasospasm?
Because subarachnoid hemorrhage surrounds cerebral blood vessels.
This is usually seen in the setting of diffuse subarachnoid hemorrhage secondary to ruptured aneurysm rather than trauma, and typically manifests several days after the subarachnoid hemorrhage has occurred
What is going on in this MRI?
Diffuse axonal injury with blurring of the gray-white junction and small foci of petechial hemorrhage in white matter tracts
CT is not very sensitive for detecting DAI – MRI is required for diagnosis.
What is going on in this noncontrast CT?
Acute subdural hemorrhage
You can tell it is acute because the blood is bright
What is going on in this noncontrast CT?
Chronic subdural hemorrhage
You can tell by the color of the coagulated and fibrosing blood. This bleed has been maturing for at least 3 weeks to obtain this apperance.
What is going on in this noncontrast CT?
This one is really tough. Based on the ventricles, you can tell that there is a mass lesion, but it is almost impossible to differentiate from the gray matter of the cortex.
This is a subacute subdural hemorrhage. In the process of maturation, from ~3 days - 3 weeks, this is how a subdural hemorrhage will appear – isodense with gray matter.
Often your clinical suspicion for subacute SDH should be triggered when there is evidence of mass effect and altered mental status, but the CT generally looks normal except that the gray matter looks too thick.
Major brain fissures and sulci
Normal saggital T1 weighted midline brain MRI
For orientation purposes, anterior is to your left (A). The corpus callosum (CC) is located superiorly. The pituitary gland (P) sits in the sella turcica and connects to the hypothalamus via the pituitary stalk or infundibulum ( dotted white arrow ). The mammillary bodies (M) are located anterior to the brainstem. The cerebral aqueduct ( solid white arrow ) is superior to the midbrain. The brainstem is composed of the midbrain (Mi), the pons (Po), and the medulla (Me). The fourth ventricle (4) communicates with the cerebral aqueduct and lies between the cerebellum (Ce) and the brainstem.
Axial MRI T1/T2 of deep gray structures in the brain
Axial T1-weighted (A) and T2-weighted (B) images of the brain demonstrate that CSF in the lateral ventricles is dark on T1 and bright on T2 ( solid black arrows ).
Gray matter, which contains the neuronal cell bodies, is actually gray on T1-weighted images ( open white arrow ) and white matter, which contains myelinated axon tracts, is whiter ( white circle ). The caudate nuclei ( solid white arrows ) and lentiform nucleus ( dotted white arrows ) together form the basal ganglia. The thalamus ( dotted black arrows ) is located posterior to the basal ganglia.
Lentiform nucleus
The lentiform nucleus is composed of the putamen (laterally) and globus pallidus (medially).
Finding the caudate, thalamus, and lentiform nucleus
What is going on in this saggital MRI?
A pineal gland tumor is seen compressing the midbrain and other surrounding structures
Finding the pineal gland
It is easiest to find on saggital view, but can be found axially by finding the top of the cerebellum and looking just anteriorly
Occasionally there will be benign pineal calcifications
You’re not going to see a skull fracture unless you. . .
. . . put on the bone window
Blow-out fracture
Most common fracture of the orbit. Caused by direct eye trauma.
It is a fracture of the inferior orbital floor leading into the maxillary sinus, or the medial wall of the orbit leading into the ethmoid sinus. Sometimes this fracture produces inferior rectus entrapment syndrome (restriction of upward gaze, diplopia).
Helpful signs to suggest this fracture may include: orbital emphysema, apparent soft tissue/fat entrapment in the superior maxillary sinus, blood in the maxillary sinus.
Tripod fracture
Another common eye fracture. Usually the result of blunt force to the cheek
Involves separation of the zygoma from the remainder of the facial bones by separation of the frontozygomatic suture, fracture of the floor of the orbit, and fracture of the lateral wall of the ipsilateral maxillary sinus
Almost all epidural hematomas (>95%) have. . .
. . . an associated skull fracture
Often in the temporal bone
In contrast, subdural hematomas usually are not.
Vasogenic edema affects ___.
Cytotoxic edema affects ___.
Vasogenic edema affects primarily white matter. White-gray differentiation is preserved.
Cytotoxic edema affects white matter and gray matter. White-gray differentiation is often lost.
60% of hypertensive hemorrhagic strokes occur in . . .
. . . the basal ganglia
In the setting of SAH, how can you tell where the likely aneurysm was?
Where there is the most blood!
Beam hardening artifact
Bright/dark bands due to a hard surface
Partial volume averaging
Don’t be fooled into thinking these are bleeds! They will occur near the skull base
Happens when the computer averages bright bone with dull cortex.
What comes out of the suprasellar cistern laterally?
The MCA!
This is where you look for them
If hyper dense, “dense MCA sign”, this suggests a clot is present in the artery
What is going on in this noncontrast head CT?
Brain abscess
Note the vasogenic edema with clear gray-white differentiation
The fibrous walls of the abscess are the same density as the gray matter. They may be quite thin or quite thick, so don’t let their density fool you.
What is going on in this noncontrast CT?
Epidural hematoma with associated subgaleal hematoma on the skin side
The subgaleal can be really helpful in helping you localize!
What is going on in this noncontrast head CT?
Subdural hematoma just around the posterior falx
Remember that the subdural space continues along the falx
Falx asymmetry is a way to tell
Pseudosubarachnoid hemorrhage
Diffuse edema of the brain where the swollen brain tissue pushes up against the MCA can give the appearance of the subarachnoid hemorrhage “star”
With intra-axial bleeds, you will NOT see . . .
. . . mass effect
Not typically.
So, you will see a large area of white-out brain with minimal edema and no shift. If it was a tumor, you would see significant edema and shift.
MR spec in assessment of CNS pathology
-
Malignancy
- Increase in choline/creatinine ratio
- Decrease in N-acetyl-aspartate/creatinine ratio
-
Anaerobic metabolism (infection or necrotic tumor)
- Presence of a lipid/lactate peak
Normal MR spec
How many ACOMs are there? How many PCOMs are there?
There is only one ACOM that links the left and right ACAs
There are two PCOMs that link the PCAs to the MCAs
What four vessels come off of the tip of the basilar artery?
Both PCAs and both superior cerebellar arteries
Internal carotid artery branches
Insular ribbon sign
Can help diagnose stroke on CT prior to typical stroke changes
Loss of the ipsilateral insular ribbon due to swelling from the stroke
Vanishing basal ganglia sign
CT sign that suggests acute stroke
Asymmetry in the hyperintensity of the basal ganglia on one side
Differentiating MRI sequences
Main MRI sequences for neuroimaging
External carotid artery branches
- Mnemonic from inferior to superior, alternating anterior and posterior: Some anatomists like freaking out poor medical students
- Superior thyroid a.
- Ascending pharyngeal artery
- Lingual a.
- Facial a.
- Occipital a.
- Posterior auricular a.
- Maxillary a.
- Superficial temporal a.
Lenticulostriate territories
Pseudosubarachnoid sign
Looks like a subarachnoid sign, but is in fact the normal arteries against a hypointense background
This may seem tricky, but in reality you will see it in the context of diffuse cerebral edema, so you just need to know to ignore it in that case.
