module 9: neurological disorders Flashcards
Define consciousness. What two components comprise consciousness?
consciousness = the state of awareness of self and the environment, and of being able to orient to new stimuli
2 components:
- arousal (wakefulness)
- content and cognition
What parts of the brain are required for a normal state of arousal (wakefulness)?
reticular activating system (RAS)
what parts of the brain consists of the RAS?
- brainstem
- medulla and thalamus
- functioning cerebral cortex
What must be damaged for loss of arousal to occur?
- direct injury to the RAS
OR
- both cerebral hemispheres (at the same time)
What is included in “awareness”?
- selective attention
- ability to select specific information
- memory
- exercutive attention
- maintain sustained attention
Describe the levels of consciousness
- coma - not arounseable
- stupor - arouseable only to pain
- obtundation - lower level of arousal, sleepy
- delirium - restlessness, hallucinations, delusions
- confusion - disorientation, fuzzy thinking, poor response to current stimuli
Name and describe the scale used to commonly assess level of consciousness
glasglow coma scale
- categories
- eye opening
- verbal responses
- motor response
- higher the score, the better
Define brain death. How is it determined?
brain death = no recovery possible and brain cannot maintain internal homeostasis (everything done by machine)
determined by:
- well established underlying pathology
- deep unresponsive coma and absence of motor reflexes
- absent brainstem reflexes
- requires mechanical ventilation- “apnea test”
- lack of other causes (only the brain is the problem)
must be verified by multiple physicians
describe cerebral death
irreversible come
- brain stem may continue to maintain homeostasis
- individual will never be able to response in any significant way to the environment
describe persisitent vegetative state
- complete unawreness of self or surrounding environment
- sleep-wake cycles are present
- brain stem reflexes are intact
- bowel and bladder incontinence
describe minimally conscious state
- individuals may follow simple commands, manipulate objects, gesture, have intelligible speech
describe locked-in-syndrome
- complete paralysis of voluntary muscles with the exception of eye movement
- individual fully conscious with intact cognitive function, but cannot communicate through speech or body movements
Describe Cheyne-Stokes breathing, inclusind the possible location of brain damage that would cause these two patterns of breathing
- higher brain injury (ex: cerebral hemisphere)
- alternating periods of apnea (no breathing) and tachypnea (hyperventilation).. no in between
describe neurogenic hyperventilation, including the possible location of brain damage that would cause these two patterns fo breathing
- injury to midbrain
- > 40 beaths per minute
- stimunlating both extreme inhalation and exhalation
What alterations can occur with pupillary response and what information can this yield?
pupillary changes
- pupils can range from combinations of fixed, dilated, pinpoint, and unequal when exposed to light
- can help determine location/extent of brain damage
ex: severe hypoxia = dilated, fixed pupils (damage to oculomotor nerve)
What is the normal oculomotor “doll’s eye” response in a comatose patient? What are two abnormal oculomotor responses?
- doll’s eye response = the oculocephalic reflex is movement opposite from head movement
- abnormal:
- following head movement
- independent movement
assessable only in comatose patients
describe decorticate posture and the location of brain damage it indicates
- upper extremities flexed at the elbows and held close to the body
- lower extremities that are internally rotated and extended
- may occur with severe cerebral hemisphere damage
describe decerebrate posture and the location of brain damage it indicates
- increased tone in extensor muscles and trunk muscles (stretched right out)
- clenched jaw
- extended neck
- head in neutral position, all four limbs rigidly extended
- occurs with brain stem lesions
Define seizure. What are some causes of seizures?
a sudden, explosive, disorderly discharge of cerebral neurons that produces a temporary change in brain function
causes:
- cerebral lesions
- biochemical disorders
- cerebral trauma
- epilepsy
Differentiate between a seizure and a convulsion
- seizure = electrical disturbance in brain
- convulsions = jerky, muscle contraction - relaxation cycles
what is agnosia?
failure to recognize the form.nature of objects
- usually only affects once sense
- ex: can recognize a safety pin by touching it, but not when looking at it
- caused by any damage to a specific part of the brain
what is hemineglect?
inability to attend to and react to stimuli coming from the contralateral side of space
- won’t visually track, orient or reach to the neglected side
- may not use those limbs, or take care of them
what is dysphasia?
understanding (receptive) and use (expressive) of symbols is disturbed or lost
- ex: cannot find words, or uses words, but are meaningless
- caused by dysfunction in left cerebral hemisphere (stroke, cancer, trauma, etc.)
what is aphasia?
inability to communicate
what is broca’s aphasia?
a result of damage to the centre of the brain responsible for the production of language
what is wernike’s aphasia?
a result of damage to the centre of the brain responsible for the comprehension of language
what are the 4 data processing deficits?
- agnosia
- hemineglect
- dysphasia
- aphasia
What does IICP stand for and what does it mean?
increased intracranial pressure
- may result from anything that takes up volume in the brain
- increased pressure in cranium
what can cause IICP?
- tumour
- edems
- excess CSF (cerebral spinal fluid)
- hemorrhage
What 3 things can be adjusted to compensate for changes in IICP? In what order are these adjusted, if needed?
3 things:
- blood volume
- CSF volume
- tissue volume
- initial loss of CSF since it is the most easily decreased in response to increased intracranial pressure (can reabsorb CSF quickly)
- cerebral blood volume
- tissue volume
what is the Monro-Kellie hypothesis?
stages of how body compensates with increased pressure
describe stage 1 of intracranial hypertension
- CSF is displaced in to spinal subarachnoid pace = increase reabsorption
- external compression of the venous system occurs to decrease ICP
- may be asymptomatic
- blood is limited in hoe much it can buffer the increased pressure due to increased levels of co2 = vasodilation = hyperventilation sometimes used to decrease ICP
describe stage 2 of intracranial hypertension
more pressure still appplied after removing CSF = decrease cerebral blood flow = vasocontriction to force blood into brain
- too much volume = decrease in brain tissue perfusion and oxygenation is compromised
- results in confusion, restlessness, drowsiness due to low o2
- neurons in vasomotor causes systemic vasoconstriction to increase systemic blood pressure
- to overcome decreased flow in brain
AKA Crushing’s reflex
describe stage 3 of intracranial hypertension
pressure in cranium starts to match systemic blood pressure = no blood up to brain = rapid decrease in functioning (hypoxia and hypercapnia of brain tissue occur)
- at this point, all compensatory mechanisms have been used, so there can now be a dramatic rise in ICP over a very short period of time
describe stage 4 of intracranial hypertension
- brain tissue shifts from the compartment of greater pressure to a compartment of elsser pressure
- the increased pressure in the lower pressure compartment also impairs its blood supply
as tissue starts to move, it adds pressure to other regions
Describe cerebral edema (definition, be familiar with causes and effects)
- an increase in the fluid content, causing increase in brain tissue volume
- causes:
- trauma
- incfection
- hemorrhage
- tumour
- ischemia
- infarct
- hypoxia
- effects
- distorts blood vessels
- displaces brain tissues
- causes herniation
Name and describe the mechanism of the two types of cerebral edema
vasogenic edema:
- start at blood vessel
- increased permeability of blood brain barrier
- plasma proteins leak out of capillaries = water drawn to them = increased water content of tissue
- occurs maining in the white matter
cytotoxic edema:
- toxins, hypoxia, etc. cause failure of transport mechanism of cells
- more sodium inside cell = ore water inside cell
- occurs mainly in the gray matter
What is hydrocephalus and what is its cause?
- excess fluid in ventricles, subarachnoid space, or both
- cause:
- too high production of CSF
- too loe reabsorption of CSF
Name and describe the two types of hydrocephalus and give an example of each
- noncommunicating (obstructive) = obstruction prevents CSF from reaching arachnoid villi and being reabsorbed
-
communicating = failure of reapsorption due to too few, or scarring of arachnoid villi
- adenomas of choriod plexus can also cause overproduction of CSF (less common)
- adenomas of choriod plexus can also cause overproduction of CSF (less common)
Name 3 general alterations that can occur if the neuromotor function of the nervous system is affected.
- alterations in muscle tone
- alterations in movement
- alterations in complex motor performance
What is muscle tone and what does it do? How is it controlled?
- muscle tone = the normal state of muscle tension which allows for controlled movement and maintenance of posture
- controlled by stretch reflex
What changes in muscle tone are brought about by injuries to the upper motor neurons vs the lower motor neurons?
- upper motor neuron injury = increased tone as the inhibitory effect of the brain on the spinal cord reflexes is removed
- lower motor neuron injury = decreased tone