44 Acute Disorders of Brain Function Flashcards
Mechanisms of Brain Injury
1 Ischemia + Hypoxia 2 Cellular Energy Failure 3 Excitatory Amino Acids 4 Reperfusion Injury 5 Incr Intracranial Pressure [ICP] 6 Brain Compression + Herniation
Ischemia
- decr. blood flow
- results in immediate neurologic dysfunction
- —-due to inability of neurons to generate ATP needed for energy-requiring processes
ischemia + hypoxia
- usually occurs together
- isch is decr bf
- hypox is decr O2 ay cell lvl
Neuronal Tissue
- highly sensitive to O2 deprivation
- has great ATP requirement
- has limited capacity for anaerobic metab during ischemia
Cellular Energy Failure
after 5-10min w/o O2: irreversible brain damage
—bc neuronal tissue is dependent on glucose for ATP production + stores v little glycogen
Cellular Energy Failure
2 mechanisms
1 anaerobic metabolism
2 deterioration of ion gradient
glutamate is an…
excitotoxin aka excitatory amino acid neurotransmitter
—important in learning/memory
Excitatory Amino Acids
brain injury
excessive glutamate may be released bc of impaired membrane integrity
-reuptake mechanism fail to remove excess glutamate bc they are energy-dependant process
excess glutamate/excitatory amino acid
effect
excess stimulates nearby neurons that then take up large amounts of injurious Ca ions
-causes Ca overload injury
Ca overload injury
cytotoxic edema + swelling
–due to excess glutamate
Reperfusion Injury
when O2 re-enters cells, can produce reactive O2 products that act as free radicals
free radical examples
hydroxyl radicals
superoxide
peroxide
in brain cell injury, ischemia leads to…
1 hypoxia>mitochondrial failure>decr ATP>Ca overload>free radical>cell death
2 reperfusion injury>immune cells> cell death
3 glutamate release> open NMDA channels> Ca overload> free rad> cell death
Volume of Cranium
3 components
1 brain tissue
2 cerebrospinal fluid [CSF]
3 blood
NORMAL Intracranial Pressure [ICP]
0-15 mmHg
Increased ICP can occur w…
1 space-occupying lesions
2 vasogenic or cytotoxic edema
3 obstruction of CSF
4 excessive production of CSF
3 types of Increased ICP causes
1 INCR brain tissue vol
2 INCR CSF vol
3 INCR blood vol
papilledema
edema of optic disk
-may occur due to INCR ICP
Increased ICP
s/s
- headache
- altered lvl of consciousness/drowsiness
- vomit
- blurry vision
- papilledema
as ICP rises…
- compression of neural tissue + blood vessels
- DECR lvl of consciousness
- IMPAIRED pupil responsiveness to light
- altered resp patterns
- unresponsive to stimuli
- unable to move, verbalize, or open eyes
Herniation
protrusion of brain tissue thry an opening in the supporting dura of the brain
–deadly
Level of Consciousness [LOC]
state of alertness + attentiveness to one’s enviro + situation
-change in LOC is most sensitive indicator of altered brain function
most sensitive indicator of altered brain function
LOC
-may fluctuate so important to monitor + treat changes
Coma
complete loss of consciousness
Glasgow Coma Scale
standardized tool for assessing LOC in acutely brain-injured persons
-numeric scores given to arousal-directed responses of eye opening, verbal utterance, + motor rxn
Glasgow Coma Scale
mild, moderate, severe
mild: >12
mod: 9-12
sevr: <8
Glasgow Coma Scale
motor responses
-most powerful predictor of patient outcome based on: -decorticate posturing -abnormal flexor -decerebrate posturing -abnormal extension
Pupil Reflex
indicates function of brainstem + CN II + III
-change in size, shape, + reactivity of pupil is early indicator of ICP + possible brain herniation
Oculovestibular Reflex
- doll’s eyes maneuver entails rotating the patients head fr side to side
- —NORMALLY eyes turn in the opposite direction of head rotation
- impaired reflex implies brainstem dysfunction
leading cause of death + disability in U.S.
traumatic brain injury [TBI]
how are most head injuries incurred?
- transportation-related accidents
- falls
- fire
- arms
- sports accidents
Types of Traumatic Brain Injuries [TBI]
1 PRIMARY INJURY
—focal, polar, diffuse
2 INTRACRANIAL HEMATOMAS
—epidural, subdural, subarachnoid
Primary Injury
type of TBI fr initial truma/injury on brain cells
3 types: focal, polar, diffuse
Focal Primary Injury
coup: localized to sire of impact
Polar Primary Injury
coup contracoup
- due to acceleration-deceleration mvmt of brain w/in skull
- –results in double injury (usually opposite focal injury)
Diffuse Primary Injury
due to mvmt of brain w/in skull
-widespread axonal injury
Primary Injury
mechanisms
-CONCUSSION
-CONTUSION
INTRACRANIAL HEMATOMA
Concussion
- mild traumatic brain injury
- alteration/loss of LOC (<30min)
- —-but no evidence of brain damage on CT
Concussion
s/s
- headache
- n/v
- dizziness
- fatigue
- blurred vision
- cognitiv + emo disturbances
most common military/athlete injury?
concussion
Contusion
CT or MRI reveals area of brain tissue damage
–necrosis, laceration, bruising
Intracranial Hematoma
localized collection of blood w/in cranium
-disruption of vasculature can result in intracranial hemorrhage
3 types: epidural, subdural, or subarachnoid
Epidural Intracranial Hematoma
collection of blood bw DURA + SKULL
- typically involved ARTERIAL INJURY
- –thus RAPID ONSET OF SYMPTOMS
Subdural Hematoma
collection of blood bw DURA + OUTER LAYER OF ARACHNOID MEMBRANE
- typically involves BRIDGING VEINS
- -slower onset of symptoms
-may be acute or subacute
Subdural Hematoma
acute vs subacute
ACUTE: symptoms w/in 24hrs of injury
SUBACUTE: incr ICP (headache, vomit, blurred vision)
—-2-10 days later
Subarachnoid Hematoma
collection of blood bw ARACHNOID MEMBRANE + PIA MATER
-due to rupture of bridging veins that pass the arachnoid space
- more commonly assoc w rupture of cerebral aneurysms or arteriovenous malformations
- –arterial origin
Traumatic Brain Injury [TBI]
treatments
1 CardioPulmonary Stabilization
2 maintnc of norm body temp/mild hypothermia, norm PaCO2, norm serum glucose lvl, + norm intravasc vol
TBI - base skull fracture
halo test: CSF can seep out as clear fluid fr ears/nose
racoon sign: bilateral perioorbital hematomas: black eyes
battle’s sign: bruising under ear
treatment for open head injury
prophylatctic antibiotics
stroke
sudden onset of neurologic dysfunction due to cardiovascular disease that results in an area of brain infarction
-3rd leading cause of death
most common form of stroke
ischemic stroke
cerebrovascular disease + stroke cause…
abnormalities of cerebral perfusion
- transient ischemic attacks (TIA), ischemic stroke, + hemorrhagic stroke
Ischemic Stroke
results fr sudden occlusion of cerebral artery secondary to thrombus formation or emboli
Thrombotic Strokes
type of ischemic stroke
*assoc w atherosclerosis + coagulopathies
Embolic Strokes
type of ischemic stroke
*assoc w cardiac dysfunction or dysrhythmias (atrial fibrillation)
Ischemic Stroke
s/s
- **ALL CONTRALATERAL
- hemiplegia
- hemisensory loss
- visual field blindness
in an ischemic stroke, is a neurologic deficits completely resolve…
a Transient Ischemic Attack [TIA] occurs
Transient Ischemic Attack [TIA]
occurs when a neurologic deficit completely resolves in an ischemic stroke
Transient Ischemic Attack [TIA]
s/s
- neurologic symptoms typically last only minutes but they may last as long as 24 hours
- symptoms resolve completely w/o evidence of neurologic dysfunction
Ischemic Stroke
treatment
aimed at minimizing infarct size + preserving neurologic function 1 thrombolytics 2 anticoagulant 3 antiplatelet 4 endarterectomy 5 angioplasty 6 stents
Motor Deficits
initially motor deficits occur as flaccidity or paralysis
-recovery of motor function occurs w onset of spasticity
Sensory Deficits
sensory disturbances occur in same locations as motor paralysis + may involve neglect or visual impairment
- loss of visual field on paralyzed side also contributes to neglect
- homonymous hemianopsia
- assess fall risk
homonymous hemianopsia
contralateral field blindness
- same side of retina in each eye is blinded
- occurs in sensory deficits
Language Deficits
aphasia occurs w brain damage to the dominant cerebral hemisphere + can involve all language modalities
2 types of Aphasia/Language Deficit
1 Broca Aphasia
2 Wernicke Aphasia
Broca Aphasia
verbal motor/expressive
-poor articulation + sparse vocab
Wernicke Aphasia
sensory, acoustic, + receptive
-impaired auditory comprehension + speech
Types of Stroke Sequelae
- cognitive deficit
- language deficit
- motor deficit
- sensory deficit/diisturbances
most common causes of SubArachnoid Hemorrhage
Cerebral Aneurysm + Arteriovenous Malformation [AVMs]
Cerebral Aneurysm
lesion of an artery that results in dilation + ballooning of a segment of the vessel
-60% will either die or suffer permanent disability
-high blood pressure, acute alcohol intoxication, + recreational use (esp cocaine) implicated
Central Nervous System Infection
organisms may gain access to the CNS via 1 1 bloodstream
2 direct extension fr primary site
3 peripheral + cranial nerves
4 maternal-fetal exchange
…commonly assoc w bacterial infections
meningitis, cerebral abscess
…commonly assoc w viral infections
encephalitis
Meningitis
- streptococcus pneumoniae
- bacteria invade leptomeninges; accum of inflammatory exudate can result in obstructive hydrocephalus
Meningitis
s/s
- headache
- fever
- meningismus
- cerebral dysfunction
- —-confusion, delirium
meningismus
stiff neck fr meningitis
Meningitis
diagnosis
lumbar puncture
Meningitis
prevention
vaccination for Hib + N. meningitidis