6.2 intracranial pathology

types of neuroimaging used for pathologies

- MRI is study of choice in most pts, can use CT

- can use US in infants

on non-contrasted CT of the head, how do the structures appear

- bone or blood = white (arrows = blood)

- air, water, CSF = dark

- metal causes streak artifact

some _____ which show up white, can be normal in the brain as the incr w age

calcifications (circles)

CT vs MRI of the brain/skull

- MRI = better for detecting and staging intracranial + spainal cord abnormalities. Has superior contrast and soft-tissue resoltuon

- CT = better for calcifications or evaluating bone

the study of choice for acute head trauma

non contrasted CT

goal of noncontrasted CT for head trauma

look for mass effect and blood

mass effect- look for

displacement of normal structures

blood on head trauma CT will appear how

bright and settle in crevices or dependent structures

where are skull fx usually located

at point of impact

skull fx typically imply what?

additional intracranial injury

kinds of skull fx

- linear

- depressed

- basilar

to look for fx on CT you need to use

Bone windows

fractures of the cranial vault most likely occur where?

the temporal and parietal bones

most common type of skull fracture

linear skull fracture

clinical importance of linear skull fx

not much clinical importance, need to note any underlying injury

depressed skull fractures result from

high-energy blow to small area of skull (ex hammer)

depressed skull fx have high risk for

underlying brain injury > may require surgical eval

depressed skull fx are usually where?

frontoparietal region and comminuted

what does this picture show

- comminuted fx of right remporal bone (solid white arrows)

- fluid in the mastoid air cells (circle)

- air in the brain = pneumocephalus (dotted white arrow)

most serious skull fx

basilar skull fx

basilar skull fx consist of

linear fx at the base of the skull

basilar skull fx can be assoc w

tears in the dura mater w subsequent CSF leak > rhinorrhea and otorrhea

when to suspect basilar skull fx

1. air seen in the brain

2. fluid in the mastoid air cells

3. air-fluid level in sphenoid sinus

study of choice for facial fx

CT

when ordering a CT for facial fx, you must remember to

look at several contiguoius images as to ensure visualization of the entire fx

most common orbital fracture

blow-out fx

from direct impact to the orbit, ex: ball hitting eye

blow-out fx leads to

fx of the inferior orbital floor (into maxillary sinus) or the medial wall of the orbit (into ethmoid sinus)

tripod fracture is caused by

blunt force to the cheek

tripod fx

separation of the zygoma from the remainder of the facial bones

how is the zygoma separated from the remainder of the facial bones in a tripod fx?

- separation of the fronotzygomatic suture

- fx of the orbital floor

- fx of the lateral wall of the ipsilateral maxillary sinus

4 types of intracranial hemorrhage

- epidural hematoma

- subdural hematoma

- intracerebral hemorrhage

- subarachnoid hemorrhage

where is an epidural hematoma

b/w dura mater and the skull

epidural hematoma is usually from

blunt head trauma from an MVA

almost all epidural hematomas have an assoc _________ fx

temporal bone fx

how do epidural hematomas appear

- high density, biconvex, lens-shaped "mass"

- most often found in the temporoparietal region

epidural hematomas DO NOT CROSS

suture lines

recall the meninges

- dura mater = outside layer

- arachnoid = avascular middle, separated by subdural space

- pia mater = closley applied to brain and spina cord, carries blood vessels for both. Separated by subarachnoid space

SDH is more common than epidural BUT is not assoc with

skull fracture typically

SDH usually occur with

deceleration injuries or falls

SDH causes hemorrhage into

space b/w dura mater and the arachnoid

SDH is assoc with

higher mortality rate

SDH can cross ____ but cannot cross _____

can cross suture lines but cannot cross the midline

SDH freq signal severe _____

parenchymal brain injury and incr ICP

how do SDH appear on CT

- crescent-shaped

- extra cerebral bands of high attenuation that may cross suture lines and enter the interhemispheric fissure

- do not cross the midline (but can cause mass effect)

As time passes what happens to how SDH appear on imaging

- may appear isodense to the remainder of brain

- look for compressed or absent sulci, or sulci dispalced away from the inner side of the skull (white arrow)

Subarachnoid hemorrhage is usually from

ruptured blood vessel

subarachnoid hemorrage occurs where?

b/w arachnoid and pia mater

subarachnoid hemorrhage can cause

intraventricular hemorrhage

numerous causes for intracerebral hematoma

- trauam/shearing injury

- vascular disease or rupture

- amyloid deposits

CT findings of intracerebral hematomas over time

change over time and may not be immediately evident on the initial scan

intracerebral hematoma can manifest by

multiple areas of high attenuation hemorrhage w/in brain parenchyma on CT

where is intracerebral hematoma usually found?

frontal or temporal lobes

what has the poorest prognosis of all head traumas

axonal injury

axonal injury

acceleration/deceleration forces diffusely injure axons deep to the cortex, producing unconsciousness from the moment of injury

axonal injury is responsible for

prolonged coma following head trauma

initial CT scan of axonal injury

may be normal or underestimate degree of injury

CT findings of axonal injury may be similar to

those described for intracerebral hemorrhage following head trauma

what is the study of choice for diffuse axonal injury

MRI: Gradient susceptibility MRI

Gradient susceptibility MRI is very sensitive to

bleeding at the gray/white matter junction and can detect v small lesions

how will axonal injury appear on imaging?

punctuate hemorrhages (dark spots)

incr ICP is caused by either ______ or ______

- cerebral edema = incr volume of the brain

- hydrocephalus = incr size of ventricles

most common cause of cerebral edema

HTN, masses

2 types of cerebral edema

- vasogenic = extracellular accumulation of fluid

- cytotoxic = cellular edema

vasogenic cerebral edema is assoc w

- malignancy and infx

- predominantly affects the white matter (inside)

cytotoxic cerebral edema is assoc with

- cerebral ischemia

- d/t cell death

- affects both gray and white matter

with cerebral edema, what can happen on imaging?

- compression or obliteration of the normal sulci

- ventricles may be compressed

reasons for imaging strokes

- determine if another cause of neurologic impairment

- identify presence of blood > distinguish ischemic from hemorrhagic

- identify the infarct and characterize it

most strokes are ______ in origin

thromboembolic

acute strokes are initially imaged by

noncontrast CT

when would CT findings of a stroke appear?

- hemorrhagic = immediate

- ischmeic = w/in hours after onset of sx

MRI of strokes is more senstive and specific for detecting early infarction- how early can it detect?

w/in 20-30 mins of onset of the event

the most common finding of an acute less than 24h non-hemorrhagic stroke is

normal CT scan

CT stroke findings: 12-24 hrs

indistinct area of low attenuation in a vascular distribution

CT stroke findings: >24 hrs

better circumscribed lesion w mass effect that peaks at 3-5 days and usually disappears by 2-4 weeks

TLDR: abnormality peaks w/in 1st week, and resolves w/in a few weeks

which type of stroke is assoc w higher morbidity and mortality?

hemorrhagic > ischemic

hemorrhage from stroke can occur into where?

brain parenchyma or subarachnoid space

ischemic stroke, if recognized early, can be tx w

intravenous-thrombolytics: tenectoplase (TNK) or mechanical thrombectomy

image-guided interventions for hemorrhagic strokes

CTA or MRA to pinpoint area and possibly coil or clip

most frequent CNS aneurysm is

berry aneurysm

berry aneurysm forms from

congenital weakening in the arterial wall, usually at the sites of vessel branching in the circle of Willis

what incr growth of berry aneurysms

HTN and aging

larger berry aneurysms do what?

bleed more freq

someone w a ruptured aneurysm may say

"the worst headache of my life"

upon aneurysm rupture where does blood usually enter?

subarachnoid space

most aneurysms are detected by

CTA or MRA

hydrocephalus

expansion of ventricular system causing an incr in volume of CSF

hydrocephalus can be d/t

- overproduction of CSF

- under absorption of CSF

- restriction in outflow of CSF

in hydrocephalus, compare the ventricles to the sulci

ventricles are usually disproportionally dilated compared w the sulci

in cerebral atrophy, compare the ventricles and sulci

both ventricles and sulci are proportionately enlarged

what is a form of communicating hydrocephalus

normal pressure hydrocephalus

normal pressure hydrocephalus has what classic triad of sx

1. gait

2. dementia

3. urinary incontinence

age of onset for normal pressure hydrocephalus

60-70 y/o

normal pressure hydrocephalus is easily treated w

ventriculoperitoneal shunt

image findings of normal pressure hydrocephalus

- enlarged ventricles with normal or flattened sulci

cerebral atrophy

loss of both gray and white matter

cerebral atrophy is assoc with

dementia ex: Alzheimer's disease

Alzheimer's disease

diffuse cortical atrophy, esp in the temporal lobes

ventricles dilate in both hydrocephalus and cerebral atrophy- what makes cerebral atrophy different?

ventricles dilate b/c loss of normal cerebral tissue. This vacant space is passively filled with CSF but CSF production and absorption are normal

image findings of cerebral atrophy

proportionate enlargement of both the ventricles and the sulci

gliomas

common intraaxial (w/in brain parenchyma) mass in an adult