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what are focal effects?
- Focal= Local
- signs related to the specific area of the brain or SC in which the lesion is located.
- Examples: paralysis of the right arm resulting from damagge to a section of the left frontal lobe
___ lesions occur in the cerebral hemispheres above the tentorium cerebelli.
A lesion in this location leads to a specific dysfunction in a discrete area, perhaps numbness in a hand.
cerebral hemispheres above the tentorium cerebelli
a ___ lesion must become very large before it affects consciousness.
An ___ lesion is located in the brain stem, or below the tentorium.
a relatively small lesion in this location may affect many motor and sensory fibers, resulting in widespread impairment, because nerves are bundled together when passing through the brain stem.
Respiratory and circulatory function and the LOC may be impaired by a small lesion in this area
reticular activating systemarea of the brain for arousal or awareness
one of the early changes noted in those with acute brain disorders is a decreasing ___ or responsiveness
a small lesion of this kind can affect the RAS
causes for decrease in LOC
- extensive supratentorial lesions
- small supratentorial lesions
- space-occupying masses in the cerebellum leading to compressions of the brain stem and RAS
- systemic disorders such as acidosis or hypoglycemia can depress the CNS
levels of reduced LOC
- memory loss
- unresponsiveness to verabl stimuli
- difficulty in arousal
- loss of consciousness or coma: some reflexes present
terminal stage of reduced LOC
markers of deep coma
- loss of all reflexes
- fixed dilated pupils
- slow and irregular pulse and respirations
A ___ is a loss of awareness and mental capabilities, resulting from diffuse brain damage.
loss of awareness and mental capabilities where the brain stem function continues, supporting respiratory, cardiovascular, and autonomic functions
- refers to a conditions in which an individual with brain damage is aware and capable of thinking but is paralyzed and cannot communicate.
- some can move their eyes in yes/no response
this diagnosis is ofeten required to terminate medical intervention, because individuals can be maintained artificially on cardiopulomnary support systems.
criteria for brain death
- cessation of brain function, including function of the cortex and brain stem (flat or inactive EEG)
- Abscence of brain stem reflexes or responses
- abscence of spontaneous respirations when ventilator assistance is withdrawn
- establishment of the certainty of irreversible brain damage by confirmation of the cause of the dysfunction
why is a longer time period and additional testing required before brain death can be confirmed in cases of drug overdose or hypothermia
these cases can cause loss of brain activity temporarily
Damage to the cranial nerves or their nuclei or to the assigned area of the brain may interfere with vision or other ___
vision, hearing, taste, and smell
The ___ ___ in the ___ ___ ,which receives and localies basic sensory input from the body, is mapped to correspond to receptors in the skin and skeletal mm of various body regions
- somatosensory cortex
- parietal lobe
___ or convulsions are caused by spontaneous excessive discharge of neurons in the brain.
Because the brain is encased in the rigid non-exapadable skull, any increase in fluid, such as blood or inflammatory exudate, or any additional mass such as a tumor causes an increased ___
___ → less arterial blood can enter high pressure area→ compression of brain tissue→ decrease function of neurons locally and generally→___
how does the body attempt to compensate for ICP
- shifting more CSF to the spinal cavity
- increasing venous return from the brain
hypoxia resulting from initial ICP compensation→___→ adds to the fluid volume inside the skull and is also effective for a short time
arterial vasodilation in the brain through local autoregulatory reflexes
Why is ICP significantly elevated before signs become apparent
because of the initial compensatory mechanisms
first indication of increased ICP
decreased LOC or lethargy
Early indications of ICP
- severe headache: from stretching of the dura and walls of the large BVs
- vomiting: often projectile vomiting that is not associated with food intake, resulting from pressure stimulating the emetic center in the medulla
- Papilledema: caused by increased ICP and swelling of optic disc
- swelling of the optic disc (where the optic nerve enters the eyeball);
- usually associated with an increase in intraocular pressure
- reflects the effects of increased ICP in the brain
Vital Signs of Increased ICP
- Increasing BP with increase pulse pressure
- slow heart rate
rationale for vital signs of increased ICP:
- Increased BP and Pulse Pressure: Cushing's reflex; response to cerebal ischemia causes sytemic vasoconstriction. More blood to brain to relieve ischemia
- Slow heart rate: response to increasing BP
The ___ is a nervous system response to increased intracranial pressure. It results in Cushing's triad of widening pulse pressure, irregular breathing, and bradycardia. It is usually seen in the terminal stages of acute head injury and may indicate imminent brain herniation.
Visual signs of increased ICP
- pupil ipsilateral to lesion becomes fixed and dilated, as pressure increases the other pupil becomes fixed and dilated
Rationale for signs of ICP affecting vision
- Papilledema: increased pressure of CSF causes swelling around the optic disc
- Fixed dilated pupils: pressure on the CNIII
cranial nerve III oculomotor
when a mass, such as a blood clot or tumor, becomes large enough, it may displace brain tissue, leading to ___
types of herniations
- cerebellar/tonsillar (infratentorial)
in ___ herniation, the cerebral hemispheres, diencephalon, and midbrain are displaced downward.
The resulting pressure affects the flow of blood and CSF, the RAS, and respiration.
___ herniation occurs when the uncus of the temporal lobe is diplaced downward past the tentorium cerebelli, creating pressure on the third cranial never, the posterior cerebral arty, and the RAS.
___ herniation develops when the cerebellar tonsils are pushed downward through the foramen magnum leading to compression of the ___ and ___ ___ and causes ___.
- brain stem
- vital centers
space occupying lesion
What are the best examples of SOLs that lead to ICP?
Benign brain tumors as well as malignant can be ife-threatening, unless they are in an accessible superficial location where they can be removed.
___ form the largest categories of primary malignant tumors
___ ___ tumors rarely metastasize outside the CNS, nut multiple tumors may be present within the CNS.
___ ___ tumors are quite common, usually metastasizing from breast or lung tumors, and they cause effects similar to those of primary brain tumors.
tumors of the ___ or ___ ___ cause similar neurologic effects that result from pressure on the brain.
- meningis (meningioma)
- pituitary gland (adenoma)
___ ___ and ___ tumors are common in young children.
SS of brain tumors
- specific site of tumor determines the focal signs
- morning headaches that in time increase in severity and frequency
- lethargy and irritability
- personality and behavioral changes
in brain stem or cerebellar: CNs are affeted leading to unilateral facial paralysis
SS of pituitary adenomas
- endocrinologic signs
- headaches and visual signs
- visual disturbances