Neuropathology, Trauma, Radiology, & Tests Flashcards
List the types of brain herniation
Cingulate/Subfalcine
Uncal/Transtentorial
Tonsillar
Cingulate/Subfalcine herniation
• Superior unilateral mass pushes ipsi cingulate gyrus under falx
Uncal/Transtentorial herniation
- Ipsi uncus forced into tentorial notch
- Commonly with mass of temporal lobe
- May impinge oculomotor nerve = causes dilation of ipsi pupil (due to parasympathetics to ciliary body)
- May compress contra cerebral peduncle into tentorial notch → ipsi hemiparesis
- May compress ipsi posterior cerebral artery → infarct
Tonsillar herniation
- Cerebellar tonsils protrude into foramen magnum
* Most commonly with mass in posterior fossa
Causes of brain herniation
Mass lesion (focal):
• Hemorrhage
• Tumor
• Infarct
Mass lesion (generalized) • Edema
Coup vs. Contrecoup
Coup = to injury at impact site
• Seen in trauma to stationary heads or those in motion
• Often at frontal, temporal, or occipital lobes
Contrecoup injury = occurrs remote from the impact focus
• Most commonly seen in abrupt deceleration of heads in motion.
Concussion
- Transient diffuse cerebral cortical dysfunction (ex: confusion) with or without loss of consciousness
- Other symptoms: headache, nausea
- Usually resolves in seconds to hours
- Historical definition = transient, but instant loss of neural function, followed by “recovery.”
- This definition = problematic
- Often have post-concussion syndrome (variable duration, headaches, subtle cognitive abnormalities, emotional dysregulation)
- This is unaccompanied by visible antemortem acute pathologic findings upon brain imaging.
- Actual structural changes include mitochondrial, membrane, and cytoskeletal abnormalities. Fiber injury may be present (DIA), with delayed axotomy, and continued pathology (i.e. CTE)
Chronic traumatic encephalopathy
Chronic progressive neurodenerative disease due to repetitive “mild” cranial trauma
• Delayed dementia
• Patients = athletes & military veterans.
Clinical features vary with pathologic stage:
• Early (I-II) include emotional explosivity, headache, and changes in short-term memory, concentration, & depression.
• Late (III-IV) include executive dysfunction, cognitive impairment, dementia and aggression (+/- motor issues)
Pathology:
• Gross includes:
o Atrophy, cavum septum pellucidum, pallor of pigmented nuclei, thalamic and mammillary atrophy.
Microscopic features:
o pTau intraneuronal and intraglial neurofibrillary inclusions, neuroaxonal loss, astrocytic tangles, and TDP-43 (transcriptional inhibitor) positive staining in effected areas.
o Tau = normally part of microtubules
o Tau becomes neurotoxic by being abnormally processed (phosphorylated, misfolded, cleaved).
o Interneuronal spreading of toxic Tau may occur by prion-like mechanism.
Cerebral Contusion
- May occur without fracture
* Variable amounts of hemorrhage
Cerebral laceration
- Generally accompanied by fracture or penetrating injury (not always)
- Variable amounts of hemorrhage
Isolated epidural hemorrhage
- Frequently = due to temporal head impact and laceration of middle meningeal artery
- Bleeding under high pressure
- The resultant ARTERIAL bleeding may enlarge rapidly = constitutes a medical emergency
A lucid interval may follow the time of trauma
• Initial concussion clears rapidly
• Followed by progressive diminishing arousal over minutes to hours
• Arterial bleeding → increased intracranial pressures
• Precedes recognition of clinical symptoms.
Imaging: o Lenticular shaped o Can cross midline o Does not cross sutures o Associated with fractures and intracranial air
Isolated adult subdural hemorrhage
- Most commonly = due to rupture of bridging VEINS from abrupt cranial deceleration
- Bleeding under low pressure
Risk factors:
• Risk for falls
• Coagulopathies
• Atrophic brain diseases (stretches bridging veins)
• SDH in an infant = a marker for possible inflicted trauma (“shaking”).
• SDH may be acute, subacute, or chronic.
Imaging: o Crescent shaped o Follows dural reflection o Does not cross midline o Crosses sutures
Non-adult abusive head trauma
• In infants and toddlers suffering shaking and/or impact cranial injury.
Pathology
• Acute subdural hemorrhage
• Ocular retinal hemorrhage
• Intracranial mass effect
Cellular pathology
• Axonal shearing injury with preference to centrum semiovale, dorsolateral brainstem, and corpus callosum with variable mass effect
Describe Computed tomography imaging
Based on same principle as x-ray
• Radiation passes successively through tissue from multiple directions
• Computers integrate information and construct image
Contrast: iodine-based (bright on CT)
Indications • Trauma: fractures, hemorrhage • Stroke: initial evaluation • Hydrocephalus • Mass effect/midline shift
Advantages:
• Quick, readily available
• Excellent for visualizing bones
• Able to assess presence of calcification
Disadvantages
• Radiation
• Not as good as MR at evaluating soft tissues
When to order:
• Acute setting
• Situation where hemorrhage is on differential
• Initial screening test
Describe MRI
Based on magnets (not radiation)
• H+ atoms randomly arranged in body
• With magnetic field → H+ atoms line up
• Radiofrequency energy excites atoms
• H+ atoms relax/fall back to normal energy state → emit signal
• Relax at different rates depending on type of tissue
Contrast: Gadolinium-based (bright on T1-weighted images)
Indications
• Tumors, stroke, epilepsy, demyelination, infection, cranial nerve palsy
Advantages
• Broader palette of tissue contrast → greater anatomic detail, more comprehensive analysis of pathology
• Excellent for evaluating brain parenchyma
• No ionizing radiation
• Direct multi-planar imaging
Disadvantages • Higher cost, limited access • Takes longer • Difficult for unstable patients • Claustrophobia • Absolute contraindications (ex: pacemakers) • Not as good at evaluating bones
When to order:
• Characterize an abnormality initially seen on CT
• Characterize disease processes typically occult on CT
• Problem solving
