Neurology 1

how much % of body weight is the brain?

how much % of body weight is the brain?

2%

how much % does the brain consume of total body oxygen?

20%

how much % of CO per minute does the brain receive?

15%

750ml of 5L CO

Does the brain store store energy?

No

• so it requires constant 02 and glucose supply

does the brain store oxygen?

No

does the brain store nutrition (ex. glycogen, glucose)?

No

does the brain recover nervous tissue injury?

No

• no centrioles in CNS neurons (crucial in mitosis division, therefore CNS neurons cannot be replicated or replaced)

how long can the brain survive without oxygen?

for 10 seconds

how long does it take for apoptosis (cell death) to occur when the brain is not getting oxygen?

after 4-6 minutes

what is brain plasticity?

the ability of the NS to change its activity by rewriting itself/modify its connections

what allows the brain to develop to adulthood?

brain plasticity

what allows the brain to recover from brain injury?

brain plasticity

what does consciousness depend on?

cerebral cortex and reticular formation

what is the reticular activating system responsible for?

• wakefullness

• activates higher centers of the cerebral cortex

what does the reticular formation do?

serves as a filter, relaying only important information/stimuli to the brain

what does low RAS activity lead to?

low awareness and wakefulness (sleep)

what is low RAS activity pathology?

decreased perfusion, altered metabolic state (metabolic acidosis- buildup of acid in body) and lead to altered consciousness/LOC

what is an example of low RAS activity pathology?

decreased oxygenation leads to decreased function of brainstems resp. centers and decreased sensitivity to increased CO2 and irregular respirations and apnea.

what is LOCx4?

• person

• place

• time

• situation

what is the min and max of the glasgow coma scale?

• Min 3

• Max 15

what does the glasgow coma scale measure?

EVM

• eye response (out of 4) (spontaneous, speech, to pain, no response)

• verbal response (out of 5) (A&Ox3, confused, inappropriate works, sounds, no response)

• motor response (out of 6) (obeys command, moves to localized pain, withdraws towards center of body away from pain, abnormal/decorticate flexion to pain (does not have to do with pain stimulus), extension response to pain (decerebrate), no response to pain)

what is brain injury caused by?

caused by pathology and subsequent sequelae

what is pathology of brain injury?

disease or injury

• ex. storke/CVA/cerebrovascular accident, infection, tumor, trauma

what is sequelae of a brain injury?

aftereffect (pathological condition) of a disease, condition or injury

• ex. ischemia, cerebral edema, metabolic acidosis, increased ICP, bleeding, inflammation/infection

what is focal injury/deficit?

affects a specific location within the brain, may include speech, vision and hearing problems

• ex. loss of hearing due to occipital lobe tumor

what is global injury/deficit?

not specific to a certain area of the brain, may include general loss of consciousness or emotional problem

• ex. stupor, coma, altered VS, declining autoregulation (loss of protective reflexes - blink, urination, defecation) → urination and defecation reflex allow stool+urine to pass

what is autoregulation?

intrinsic ability of an organ to maintain blood flow at a constant rate, despite changes in arterial perfusion pressure

what is brain death?

irreversible (permanent) cessation of all functions of the brain, legally dead

what is the criteria for brain death?

persistent coma, absence of brainstem reflexes, lack of ability to breathe independently

what are the brainstem reflexes?

gag, cough, dolls eyes/oculocephalic

what is a gag reflex?

reflex with posterior tongue stimulation

what is a cough reflex?

reflex can be stimulated by inhaling a citric fume

what is a present/normal/positive doll’s eye/oculocephalic reflex?

if eyes move opposite to head movement (like doll eyes) ie eyes want to remain focused on a point directly in front

what is a negative/abnormal doll’s eye/occulocephalic?

is eyes do not move at all

what do the eyes look like in brain death?

eyes are dilated, but what is most essential to declare brain death is no response to light

what happens in brain death?

no motor response, no brainstem reflexes, apnea

• note: some spinal reflexes may be present, however, when looking for lack of motor response, an example would be no response to noxious stimuli applied to the sternum

what is a vegetative state?

the patient is awake but not showing any signs of awareness

• may be a possibility of recovery

• does not meet brain death criteria

where in the brain is damaged in a vegetative state?

damage to gray and white matter

what is maintained in a vegetative state?

brainstem reflexes are maintained, sleep-wake cycle, hypothalamic function adequate to meet basic demands (ex. temperature regulation)

• may open their eyes, wake and fall at regular intervals and have basic reflexes

what happens to awareness in a vegetative state?

no awareness of self or surroundings, inability to voluntarily interact, inability to reproduce behavioral responses

• if some self awareness: minimally conscious state

what is a minimal conscious state?

severely altered consciousness in which minimal but definite periods of awareness is demonstrated

can a patient in a minimal conscious state communicate?

may communicate or respond to commands (ex. yes/no responses, move finger, purposeful emotional responses)

what is a coma?

a state of profound unresponsiveness/unconsciousness with minimal brain activity. alive but cannot be woken up.

what is hypoxia?

low levels of oxygen in your body tissues

• deficient delivery of oxygen to the tissue

what happens to the brain when hypoxia occurs?

ALL brain tissues, leads to agitation, decreased LOC, seizures

• depends on severity and suddenness of onset

what is hypoxia usually caused by?

• hypoxemia

• ischemia

what is hypoxemia?

below normal level of oxygen in blood

• ex. anemia, toxicity

what is anemic hypoxia?

occurs when oxygen carrying ability of blood decreases, thus allowing less hemoglobin oxygen binding sites to be available

what is ischemia?

restricted blood flow within a tissue

• can be focal or global

what can ischemia cause?

lack of oxygen/removal of waste within a tissue

what is an example of focal ischemia?

CVA (stroke)

• deficit depends on area affected

what is and example of global ischemia?

Affects all brain tissue

• metabolic acidosis (d/t severe asthma attack, ketoacidosis or d/t loss of CO from severe arrhythmia/MI

What happens when there is global ischemia?

no nutrient and O2 delivery leads to depleted resources within 5 minutes and subsequent brain injury

what are 4 compounding issues with global ischemia?

• cerebral edema

• electrolyte imbalances

• watershed infarcts

• reperfusion injury

how do electrolyte imbalances affect the brain? two ways

• Ex:  electrolyte dysfunction: excess intracellular calcium => calcium cascade: protein breakdown, DNA injury, free radical formation, lipid peroxidation, mitochondrial injury = cell death

• Ex:  electrolyte dysfunction => abnormal neurotransmitter secretion/recycling => accumulation of neurotransmitters or depletion of neurotransmitters

what is watershed infarcts?

heightened focal damage to lowered-flow regions (e.g. hippocampus)

what is reperfusion injury?

injury due to belated reperfusion, caused by inflammatory mediators/toxic byproducts/catecholamines/nitric oxide

• reperfusion injury compounds original injury

what is catecholamines?

A type of neurohormone (a chemical that is made by nerve cells and used to send signals to other cells). Catecholamines are important in stress responses. High levels cause high blood pressure which can lead to headaches, sweating, pounding of the heart, pain in the chest, and anxiety.

what are the 3 cranial cavity contents?

• Brain tissue (80%)

• Blood (10%)

• CSF (10%)

what is the Monroe-Kellie hypothesis?

states that the sum of volumes of brain, cerebrospinal fluid (CSF) and intracerebral blood is constant. An increase in one should cause a reciprocal decrease in either one or both of the remaining two.

what is normal ICP?

0-15 mmHg

how to calculate CPP?

CCP= MAP-ICP

what is CPP?

pressure gradient between internal carotid artery & subarachnoid veins

• pressure required to perfuse the brain

what is Min CPP?

45 mmHg (usually 55-60)

• profound ischemia at <40 mmHg

what happens when there is an increased ICP?

• S&S, life threatening: Cushing’s triad

• maximum impact: brain herniation

what is cushing’s triad?

hypertension & wide PP (high systolic, low diastolic), bradycardia, irr. resps

• sympathetic NS triggers HTN to try and increase O2, parasympathetic NS in baroreceptors triggers bradycardia, brainstem malfunctions with increased pressure, causing irregular respirations

• The body tries to compensate and uses every last bit of their epinephrine to compensate for the changes. Eventually, there will be no more supply of the epinephrine and thus, the bradycardia.

what is brain herniation?

brain tissue displacement d/t pressure (usually to sides and down)

what are common causes of a brain injury?

• CVA ( stroke)

• Hematomas – epidural, subdural, intracerebral

• Head injury like  concussions

• Infection

• Brain tumor

what can happened in a brain injury?

risk of cerebral edema → which increased ICP

• at first will be compensated by Monro-Kellie hypothesis

what is vasogenic cerebral edema?

BBB compromise (increased permeability) allows volume in brain to increase (inflammation) causing increased ICP

• extracellular accumulation of fluid

what is cytotoxic cerebral edema?

intracellular accumulation of fluid

• lack of oxygen (ischemia) means NaK pump cannot function, meaning an increased shift of H2O and Na into the cell causing increased ICP

• ischemia leading to electrolyte imbalance

• cells are hypoosmotic to brain, causing intracellular fluid shift

what is combination cerebral edema

complex head injury with both hemorrhage + ischemia

• TX. the underlying cause; decrease further injury

how to know if CVA is ischemia or hemorrhagic?

CT scan 1st

what is ischemic CVA?

blood clot/thrombus/embolus blocks a blood vessel (cerebral artery) in the brain

• leads to death of brain cells and permanent loss of certain functions

• 80% of all strokes

Risk Factors of Ischemic (thrombus/embolus) CVA?

htn, atherosclerosis, smoking, dyslipidemia, stenosis (narrowing), diabetes, atrial fib (embolus!), drug side effects, age, genetics

what is TIA (Transient Ischaemic Attack)?

temporary period of symptoms similar to a stroke, warning sign, sometimes known as mini stroke

• brief blockage of blood supply in cerebral artery, no permanent damage → temporarily reduced functions

CVA most common artery affected? what is the importance of this artery?

MCA (middle cerebral artery)

• impacts upper limb and face

monroe-kellie hypothesis example?

ex. reduction of venous blood flow/reduction in CSF content outside of scull → goal to maintain homeostasis of ICP

what can the BBB be compromised by?

• head injury

• CNS infection

• Hematoma → pool of mostly clotted blood

• Hemorrhage → active, ongoing bleeding

what is a CVA (cerebrovascular accident/stroke)?

loss of blood flow to a part of the brain

what does atrial fib mean?

means blood is not moving properly, and may pool within the heart, causing clots, which could then get pumped to the brain

how does ischemic (thrombus/embolus) CVAs happen?

Hypoxia => ischemia => injury to affected area

ischemic CVA tx in the hospital?

• thrombolytics (tPA)

• thrombectomy

  • catheter aspiration thrombectomy

  • mechanical thrombectomy

when do you use thrombolytics for ischemic CVA?

within 3 hours of onset to lyse clot

when do you use thrombectomy for ischemic CVA?

within 24 hours of onset

what is a catheter aspiration thrombectomy?

uses suction to draw out clot

what is a mechanical thrombectomy?

break clot into small pieces that are removed

what are associated tx. for ischemic CVA?

• carotid endarterectomy

• angioplasty

• antiplatelets, anticoagulants

• also tx. HTN, dyslipidemia etc. (risk factors)

what is carotid endarterectomy?

surgical procedure to remove build-up of fatty deposits in carotid artery (scrape out artery)

what is an angioplasty?

procedure to widen blocked arteries (may use a stent)

when will bruits be heard in CVAs?

bruits will be heard when blood flows through a narrowed artery

what are CVA deficits related to?

related to the area involved (brain tissue supplied by vessel)

what to consider in CVA deficits?

• consider also collateral circulation/back-up vessels and their adequacy

• presence of cerebral edema and increased ICP can also play a role

what is the FAST acronym?

face dropping, arm weakness, speech difficulty, time/call 911 right away

what does the left brain do?

Left is Logical

• controls reading, writing, calculations

→ difficulty understanding speech, verbal memory issues, impaired logic, sequencing difficulties

what does the right brain do?

is more visual and creative

• facial recognition, emotion, memory, attention

S&S of TIA (transient ischemic attack)?

absent stare, no memory of what happened, drop fork

• weakness, numbness, slurred speech, difficulty understanding, temp. blindness, vertigo, loss of balance

TIA (transient ischemic attack) TX.?

Anticoagulants and antiplatelets

• Apixaban

• dabigatran/pradaxa

• ASA → 81mg

• could also use tPA to lyse clot

what is apixaban

anticoagulant

• low molecular weight heparin inhibit mostly factor Xa and thrombin (IIa)

what is dabigatran/pradaxa?

anticoagulant

• blocks thrombin receptors