intracranial pathology ch27 Flashcards
On CT, fourth ventricle appears as
an inverted U-shaped structure. It has fluid so it is black.
Posterior to the fourth ventricle are the ____;
anteriorly lies the ___ and ___.
Posterior to the fourth ventricle are the cerebellar hemispheres;
anteriorly lies the pons and medulla oblongata.
The ____ seperates the infratentorial components of the posterior fossa (cerebellum and fourth ventricle) from the supratentorial comnpartment.
tentorium cerebelli
The interpeduncular cistern lies in ___ and separates the ____.
lies in the midbrain and separate the paired cerebral peduncles (which emerge from the superior surface of the pons).
The suprasellar cister is ___ to the interpeduncular cistern and usually has a five- or six-point star like ppereane.
anterior
The ____ are bilaterally symmetric and contain CSF. They seperate the temproal from the frontal and parietal lobes.
The sylvian fissures are bilaterally symmetric and contain CSF. They seperate the temproal from the frontal and parietal lobes.
The lentiform nucleusis composed of the ____ (laterally) and ___ (medially).
The lentiform nucleusis composed of the putamen (laterally) and globus pallidus (medially).
The ___ ventricle is slit-like and midline.
The third ventricle is slit-like and midline.,
At the posterior aspect of the third ventricle is the ___. Farther posterior is the _______.
pineal gland.
quadrigeminal plate cistern
____ connects the right and left cerebral hemisphers and forms the roof of lateral ventricle. The anterior end is called the ___ and the posterior end is called the ____.
corpus callosum connects the right and left cerebral hemisphers and forms the roof of the lateral ventricle. The anterior end is called the genu and the posterior end is called the splenium.
The basal ganglia are represented by the ____ and the ___, ____, ____ and ____.
The basal ganglia are represented by the subthalamic nucelus and the substantia nigra, globus pallidus, putamen and caudate nucleus.
The frontal (also known as anterior horns) of the ____ hug the head of the caudate nucleus.
lateral ventricles
The two frontal horns of lateral ventricles are separated by the midline ____.
septum pellucidum
The temporal horns, which are normally very small, are more inferior and contained in the ____ .
temporal lobes
Posterior horns (occipital horns) of the lateral ventricle lie in the ___.
occipital lobes
The most superior portion of the ventricular system is _____.
the bodies of the lateral ventricles
The falx cerebri lies in the ____
interhemispheric fissure
On an unenhanced CT scan of the brain, anything that appears “white” will generally be either __ density or __, in the absence of a metallic body.
bone(calcium)
blood.
Calcifications that may be seen on CT of the brain that are nonpathologic are:
pineal gland
basal ganglia
choroid plexus
falx and tentorium
Normal structures that can enhance after administration of iodinated IV contrast:
venous sinuses
choroid plexus
pituitary gland and stalk
Hypodense (Dark) AKA Hypointense tissues on CT
Fat, Air, Water, Chronic subdural hematomas
Isodense tissues on CT
Normal brain
Some forms of protein (e.g. subacute subdural hematoma)
HYperdense (Bright) AKA Hyperintense tissues on CT
MEtal (aneurysm clips, bullet)
Iodine
Calcium
HEmorrhage (high protein)
What is the study of choice for detecting and staging intracranial and spinal cord abnormalities
MRI
What is more sensitive for detecting calcification in lesions or in evealuation cortical bone? CT or MRI
CT
Initial CT evaluation of the brain in the emergency setting focuses on whether there is
1.
2.
- mass effect
2. blood
How do we determine if there is mass effect
We look for displacement or compression of key structures from their normal positions by analyzing the location and appearance of the ventricles, basal cisterns and sulci.
Skull fractures can be described as ___, ___ or ___.
linear, depressed or basilar.
What skull fractures are the most common
linear skull fractures
What are the most serious fractures of the skull.
basilar fractures are the most serious and sonsist of a linear fracture at the base of the skull.
What fractures can be associated with tears in the dura?
Basilar structures can be associated with tears in the dura mater with subsequent CSF leak, which lan lead to CSFrhinorrhea and otorrhea.
The most common orbital fracture is ____, which is produced by ___.
blow-out fracture
direct impact on the orbit
How to recognize blow-out fracture of the orbit
- orbital emphysema
- fracture (medial wall or floor of orbit)
- entrapment of fat and/or extraocular muscle
- fluid (blood) in maxiallry sinus
what is tripod fracture
result of blunt force to the cheek, another relatively common facial fracture
- involves separation of the zygoma from the remainedr 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
What are 4 types of intracranial hemorrhages that may be associated with head trauma
- epidural hematoma
- subdural hematoma
- intracerebral hemorrhage
4- subarachnoid hemorrhage
almost all ___ hematomas have an associated skull fracture, frequently in the temporal lobe
epidural
How to recognize epidural hematoma
- they appear as a high density, extra-axial, biconvex, lens shaped “mass”, most often found in the temporoparietal region of the brain
- it is impossible for them to cross suture lines (subdural can)
- epidural hematomas can cross tentorium but subdural cannot
subdural hematomas are most commonly a result of ___
deceleration injuries (motorbike) or secondary to fails (elderly)
How to recognize an acute subdural hematoma
on CT acute subdural hematomas are crescent-shaped, extra-cerebral bands of high attenuatoin that may cross suture lines and enter the interhemispheric fissure. They do not cross the midline.
- typicall concave inward toward the brain
- as they become subacute, they become isodense
- after one week it could demonstrate a fluid-fluid level
How to recognize chornic subdural hematoma
those that are present more than 3 weeks after injury
- low-density compared with the remainder of the brain
Coup injuries are most often due to ___
shearing of small intracerebral vessels
Contrecoup injuries are due to ___
acceleration-decceleratio injuries that occur when the brain is propelled in the opposite direction, striking the inner surface of the skull
Hemorrhagic contusions are___
hemorrhages with associated edema usually found in the inferior frontal lobes and anterior temporal lobes on or near the surface of the brain
How to recognize intracerebrbal hemorrhage on CT
- mutliple small, well-demarcated areas od high attenuation within the brain parenchyma
- surrounded by hypodense rim from edema
- intraventricular blood may be present
- mass effect is common which can produce compression of the ventricles and displacements of the third ventricle and septum pellucidum to the opposite side
In subfalcine herniation…
the supratentorial brain, along with the lateral ventricle and septum pellucidum, herniates beneath the falx and shifts across the midline toward the opposite side
In transtentorial herniation…
Usually the cerebral hemisphers are displaced downward through the incisura beneath the tentorium compressing the ispilateral temporal horn and causing dilatation of the contralateral temporal horn
in foramen magnum/tonsilar herniation
infratentorial brain is displaced downward through foramen magnum
in sphenoid herniation
supratentorial brain slides over the sphenmoid bone either anteriorly or posteriorly
in extracranial herniation
displacement of brain through a defect in cranium
_____ injury is responsible for the prolonged coma following head trauma
diffuse axonal injury
How to recognize diffuse axonal injury on MRI
- small petechial hemorrhages may be bright on T1 weighted images
- multiple bright areas on T2 weighted images at the temporal or parietal cervicomedullary junction
- gradient susceptibility MRI sequences have the highest sensitivity to detect petechial hemorrhages, which will appear as punctate dark areas
What are some of the clinical signs of ICP
papilledema, headache, diplopia
Cerebral edema is divided into two major types:
vasogenic edema
cytotoxic edema
what is vasogenic edema
extracellular accumulation of fluid and is the type that is associated with malignancy and infection
what is cytotoxic edema
represents cellular edema and is associated with cerebral ischemia. it is due to cell death
Most strokes are ___ in origin.
embolic
Emoboli in stroke arises from .,…
internal carotid artery or the common carotid bifurction; can also arise in the heart and aortic arch
Other than embolus, common cause of stroke is …
thrombosis, representing in situ occlusion of the carotid, vertebrobasilar or intracerebral circulations from atheromatous lesions. Thrombosis of the middle cerebral artery is particulary common.
Strokes are divided into 2 large groups:
- ischemic (more common)
2. hemorrhagic
What are vascular watershed areas
Vascular wathershed areas are the distal arterial territories that represent the junctions between areas served by the major intracerebral vessels, such as the region between the anterior cerebral artery distribution and the middle cerebral artery distribution.
Reduction in blood flow, for whatever reason, affects these sensitive and susceptible wathershed areas the most.
How to recognize ischemic stroke
on CT the findings depend on the amount of time that has elapsed:
- 12-24hours: indistinct area of low attenuation in a vascular distribution
- > 24 hours: better circumscribed lesion with mass effect that peaks at 3-5 days and usually disappears by 2-4wks
- 72 hours: althought contrast is rarely used in the setting of acute stroke, contrast enhancement typically occurs when the mass effect is waning or has disappeared.
- > 4 weeks, mass effect disappears, there is now a well-cicrumscribed low attenuation lesion wih no contrast enhancement
What stroke is connected with higher morbidity and mortality
hemorrhage stroke
About 60% of hypertensive hemorrhages (stroke) occur in the ____.
basal ganglia
How to recognize intracerebral hemorrhage :
Freshly extravasated whole blood with a normal hematocrit will be visible as increased density on nonenhanced CT scans of the brain immediately after the event. This is due to the protein in the blood (mostly Hgb)
- dissection of blood into the ventricular system can occur in hypertensive intracerebral blled
- as the clot begins to form, the blood becomes denser for a bout 3 days because of dehydration of the clot
- after the third day, the clot decreases in density and becomes invisible over the next several weeks. The clos loses density from the outside in so that it appears to shrink
- after about 2 months, only a small hypodensity may remain
The most frequent CNS aneurysm is ____,which develops from a ____, usually at the ____.
The most frequent CNS aneurysm is berry aneurysm , which develops from a congenital weakening in the arterial wall, usually at the Circle of Willis.
What is the critical size for supture of aneurysm
10 mm
When aneurysm rupture, the blood usually enter …. (where)
subarachnoid space
What is the most common nontraumatic cause of a subarachnoid hemorrhage
rupture of aneurysm
most aneurysms are detected by … or …
CT angiography or MR angiography
How to recognize subarachnoid hemorrhage from a ruptured aneurysm
On CT acute blood is hyperdense and may be visualized within the sulci and basal cisterns
- the region of the falx may become hyperdense, widened, and irregularly marginated
- generally the greates concetration og blood indicated the most likely location of the tuptured aneurysm
HYdrocephalus may be caused by several factors:
- underabsorption of CSF (communicating hydrocephalus)
- restriction of the outflow of CSF from the ventricles (noncommunicating hydrocephalus)
- overproduction of cerebrospinal fluid
compare cerebral atrophy and hydrocephalus
cerebral atrophy: both ventricles and sulci proportionally enlarged
hydrocephalus: ventricles disproportionally enlarged
what structure becomes visible in hydrocephalus
temporal horns (greater than 2mm in size)
Obstructive hydrocephalus is divided into two major categories:
- communicating (extraventricular obstruction)
2. noncommunicating (intraventricular obstruction)
Clasically, the fourth ventricle is ___ in communicating hydrocephalus and ___ in noncommunicating hydrocephalus.
Clasically, the fourth ventricle is dilated in communicating hydrocephalus and normal in noncommunicating hydrocephalus.
What is normal pressure hydrocephalus
normal pressure hydrocephalus is a form of communicating hydrocephalus characterized by a classical triad of clinical symptoms: abnormalities of gait, dementia and urinary incontinence.
What are gliomas
Gliomas are a common, primary supratentorial intraaxial mass in an adult that accounts for 30% of all brain tumors
What glioma has the worst prognosis
glioblastoma multiforme
how to recognize glioblastoma multiforme
- because of its aggressive growth, glioblastoma multiforme frequently demonstrates necrosis within the tumor
- the tumor infiltrates the surrounding brain tissue, frequently crossing the white matter tracts of the corpus callosum to the opposite cerebral hemisphere, producing a pattern called butterfly glioma
- it tends to produce considerable caogenic edema and mass effect and enhances with contrast
metastases account for ___ % of all intracranial neoplasms
40
What are most common primary malignancies to produce brain metastases
lung, breast, melanoma
How to recognize metastases to the brain?
metastases to the brain are frequently well-defined round masses near the gray-white junction
- they are usually multiple, but can be soitary
- they are typically hypodense or isodense on non-enhanced CT
- with IV contrast, they can enhance, sometimes with a pattern of ring-enhancement
- most evoke some vasogenic edema, frequently disproportionately large to the size of the mass
What are the most common priamry brain tumor (benign and malignant)
meningioma
How to recognize mengiom on CT scan of the brain
- on unenhanced CT over half are hyperdense to normal brain and about 20% contain calcification
- on contrast-enhanced studies, meningiomas enhance markedly
- they may induce vasogenic edema in the adjecent brain parenchyma
How to recognize MS
MRI is the study of choice so that we can visualize plaques
- the lesions produce discrete globular foci of high-signal intensity (white) on T2-weighted images
- on T1 weighted nonenhanced images, they are isotense to hypoisotense , but in acute MS, the lesions enhance with gadolinium on T1 weighted images
- the lesions tend to be oriented with their long axes perpendicular to ventriucla walls
