CNS Trauma Flashcards
What components make up the blood brain barrier?
tight intercellular junctions
endothelium has low pinocytotic rate and basement membrane
dynamic interaction of endothelium with astrocytes and pericytes
What types of substances can cross the BBB?
small substances and small lipophilic molecules
What types of substances are unable to cross the BBB?
large substances and hydrophilic molecules (require active transport)
What is cerebral edema?
accumulation of excess fluid in intracellular or extracellular spaces of the brain
What is the major consequence of cerebral edema?
increased intracranial pressure
What is another name for vasogenic edema?
extracellular edema
What is vasogenic edema?
disruption (increased permeability) of BBB
results in shift of fluid from intravascular to the extravascular compartment
predominately involves white matter
What are the most common causes of vasogenic edema?
primary or secondary brain turmors
abscesses
contusions
intracerebral hematomas
What is another name for cytotoxic edema?
intracellular edema
What is cytotoxic edema?
occurs secondary to cellular energy failure
results in a shift of water from the extracellular to intracellular comparment
intracellular swelling-large amounts of Na enters cells, H2O follows
histologically brain tissue vacuolation
predominately in gray matter
What are the most common causes of cytotoxic edema?
ischemia/infarct meningitis trauma seizures hepatic encephalopathy
What can increased intracranial pressure lead to?
decreased perfusion and/or herniation syndromes
What is a subfalcine herniation?
cingulate gyrus herniates under the falx
may result in ACA compression, leading to infarct
What causes subfalcine herniation?
asymmetric expanding hemispheric lesions
What is a transtentorial uncal herniation?
medial temporal lobe displaced through tentorial opening because of asymmetric expanding lesion
What are complications of transtentorial uncal herniation?
ipsilateral CNIII nerve compression with pupillary dilation
contralateral peduncular compression (kernohan’s notch) causing ipsilateral hemiparesis
PCA compression (ipsi or bilateral)
duret hemorrhage
What is a duret hemorrhage?
fatal brainstem hemorrhage
secondary to progression of uncal herniation and resultant tearing of vessels in the midbrain/pons
What is cerebellar tonsillar herniation?
caudal cerebellar structures “tonsils” attempting to escape through the foramen magnum
What causes tonsillar herniation?
symmetric expansion of supratentorial contents into posterior fossa or expanding mass lesion in posterior fossa
What is a complication of cerebellar tonsillar herniation?
medullary compression resulting in cardiorespiratory arrest
What is hydrocephalus?
enlargement of ventricles associated with increase in CSF volume
What causes communicating/non obstructive hydrocephalus?
decreased absorption at arachnoid granulations
What causes non-communicating/obstructive hydrocephalus?
obstruction within ventricular system, preventing communication between the ventricles proximal and distal to the obstruction
(ie/tumor, congenital malformation, thick meninges at base of brain)
What are the two types of head trauma?
blunt/nonmissile (most common)
penetrating/missile
What is primary damage seen in head trauma?
immediate
scalp lac, skull fx, cerebral contusions, cerebral lacs, intracranial hem, DAI
What is secondary damage seen in head trauma?
delayed ischemia hypoxia cerebral swelling infection
What typically results from focal injury?
focal neurological deficits/epilepsy
What typically results from diffuse injury?
coma/vegetative state
Describe the 3 types of skull fractures
linear: single fracutre line, through entire thickness of skull
comminuted: multiple linear fractures radiate from point of impact
depressed: bone fragments displaced inward
What is a concussion?
pathophysiologic process induced by traumatic biomechanical forces (also called mild TBI)
constellation of physical, cognitive, emotional and or sleep-related sx that may or may not involve loss of consciousness
What is a contusion?
superficial bruise of the brain
usually at crests of gyri
occur overlying rough area of inner skull (ie/orbital and temporal regions)
How do acute contusions appear?
wedge shaped
superficial hemorrhage in cortex and meninges
How do old contusions appear?
gyri indented, cavitated, with brown/orange discoloration
What is the difference between a coup and contrecoup contusion?
coup contusions occur at the point of impact while contrecoup contusions occur directly opposite the point of impact
Describe diffuse axonal injury
occurs with deceleration/acceleration injury and/or angular accel
loss of consciousness at onset WITHOUT lucid interval
unconscious or disabled until death
What lesions are seen with DAI?
clusters of petechial hemorrhages and soft hemorrhagic foci acutely
hydrocephalus ex vacuo, thinned corpus callosum and gray discoloration of white matter chronically
What microscopic changes are seen with DAI? (needed to confirm DAI dx)
axons are disrupted, axonal transport continues and causes axonal swellings
acute: axonal swellings, positve for B amyloid protein and silver stains
subacute: microglia and axonal swellings
chronic: degeneration of involved fiber tracts
What commonly causes epidural hematomas?
skull fx & mca tear
slow accumulation because of adherence between skull and dura
What are the signs/symptoms of an epidural hematoma?
lucid interval
What are signs/symptoms of a subdural hematoma?
headache, confusion
What causes a subdural hematoma/
tearing of bridging veins extending from subarachnoid space to dura
more common in elderly w/brain atrophy
How does chronic subdural hematoma occur?
recurrent bleeds from friale vessels in granulation tissue, originally injury occurred months ago
What does a chrnoic subdural hematoma look like?
well organized membrane enclosing the hematoma
How do subarachnoid hemhorrages occur?
contusions, lacerations, skull base fractures, escape of blood from ventricular system
Why does post-traumatic hydrocephalus occur?
obstruction of CSF resorption due to subarachnoid space hemorrhage
What are sequelae of brain trauma?
post-traumatic hydrocephalus
post-traumatic epilepsy
chrnoic traumatic encephalopathy
What is chronic traumatic encephalopathy associated with?
mild repetitive traumatic brain injury
ie/in athletes and veterans
What are the signs/symptoms of chronic traumatic encephalopathy?
initially: impulsivity, aggression, depression, short-term memory loss
eventually: dementia, gait, speech abn, parkinsonism
What pathology is seen in chronic traumatic encephalopathy?
extensive deposition of tau in form of neurofibrillary and glial tangles and TDP-43 inclusions
