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
Progression of ischemic stroke
• Interrupt blood flow → rapid (within minutes) breakdown of energy metabolism and ion exchange pumps
Result: massive shift of water from extra- to intracellular compartment = cytotoxic edema
• Intracellular water accumulation due to Na/K pump failure
• Pattern involves cortex and white matter
• Both gray and white matter are supplied by blocked vessel in embolic infarction
• Usually develops as response to ischemia or hypoxia
Produces high-intensity area on DWI (Cytotoxic edema)
• See cellular swelling
• Gray-white matter margin lost
Vasogenic edema
- Increased capillary permeability
- White matter mostly affected
- Allows movement of proteins from IV space → EC space
- Response to trauma, tumors, focal inflammation, and late stages of cerebral ischemia
Types of astrocytomas
Circumscribed = Pilocytic astrocytomas
o Cyst with enhancing mural nodule
o Optic nerves/chiasm (NF1)
o Pediatric patient population
Diffuse/infiltrating astrocytomas Grade II • T2 hyperintense • No enhancement Grade III = anaplastic • Demographic: 30-40’s • Can evolve from grade II • Can de-differentiate into GBM (time to progression = 2 years) Grade IV = glioblastoma multiforme • Variable surrounding T2 change • Hemorrhage, necrosis • Heterogeneous enhancement • Daughter lesions
Name indications for lumbar puncture.
- Subarachnoid hemorrhage
- Meningitis & Encephalitis
- Acute inflammatory demyelinating polyradiculoneuropathy
- Multiple sclerosis
- Some cancers metastasized to CSF (carcinomatous meningitis)
Lumbar puncture for Subarachnoid hemorrhage
o Collect fluid in multiple tubes
o Helps distinguish bleeding from blood released during “traumatic tap” (from puncturing venous plexus around dura)
o If amount of collected blood clears = traumatic tap
o If stays constant = hemorrhage; also see xanthochromia (yellow tinge from centrifuged CSF due to RBC breakdown)
Lumbar puncture for Meningitis & Encephalitis
o Bacterial cause: elevated WBCs (neutrophils predominant), low glucose concentration, elevated protein concentration
o Viral cause: elevated WBC (lymphocytes predominant), normal glucose, elevated protein (less than bacterial meningitis)
o Fungal cause: elevated WBC (lymphocytes predominant), normal glucose, elevated protein (less than bacterial meningitis)
Lumbar puncture for Acute inflammatory demyelinating polyradiculoneuropathy
o Elevated lymphocytes with normal protein (albuminocytologic dissociation)
Lumbar puncture for Multiple sclerosis
o Elevated immunoglobulin amount (due to autoantibody production in CNS)
o Oligoclonal bands on protein electrophoresis
Lumbar puncture for some cancers metastasized to CSF
o Collect, stain, and examine cells
Describe the function and indications for the electroencephalogram
Function:
o Uses scalp electrodes to record average electrical activity of cerebral cortical neurons
o Produces low voltage, random waveforms
Indications:
1) Monitor for seizures:
• Increased and synchronous neuronal firing → abnormal, higher voltage waves
• May see non-specific focal slowing
• Epileptiform discharges = waveforms that resemble brief moments of seizures
2) Delirium and other conditions = see diffuse slowing
3) Multiple sclerosis
• Use evoked potentials to assess response to certain visual stimuli
• If subclinical optic neuritis = may cause delayed potential due to demyelinated optic nerve conducting more slowly
List the indications and results of electromyography.
o Insert needle electrodes into muscles and assess electrical activity
o Demyelination = usually normal, may see decreased amount of contraction
Axonal loss (denervation):
• Fibrillation potentials (spontaneous APs from myocytes at rest)
• Smaller amplitudes (loss and/or atrophy of motor units)
• Abnormal recruitment pattern (larger motor units due to remaining axons sprouting new terminals to denervated myocytes)
Myopathy
• Similar changes as axonal loss EXCEPT:
• Motor unit size not increased
• Nerve conduction studies = normal
List the indications and results of nerve conduction studies
o Administer electricity to nerves or skin and record response
o Axonal loss = decreased amplitude
o Demyelination = slower action potential and/or conduction block
o Polyneuropathy = diffuse and distal changes
o Focal nerve or spinal nerve root dysfunction = changes at area of dysfunction and degenerated distal portions of axons
o Myasthenia gravis = decremental muscle response with repetitive stimulation
Explain when biopsy is indicated for neurological syndromes.
Brain tumors
Autoimmune vascultis if involves CNS
o Meningeal or brain biopsy
Giant cell arteritis
o Temporal artery biopsy
Unusual polyneuropathies
o Sural nerve biopsy (sensory nerve of leg)
Myopathies
o Skeletal muscle biopsy (usually of quadriceps)
