Neuro

Physiology of consciousness

Physiology of consciousness

State of arousal and awareness of oneself and their environment

What is arousal?

being awake or reactive to stimuli

What is awareness?

encompasses all cognitive functions

Clinical assessment for arousal and awareness

LOC, Pattern of breathing, pupillary changes and eye responses, motor responses, yawning/hiccups

What is delirium

an acute delusional state that is a transient disorder of awareness that results from cerebral dysfunction

What can cause delirium

PINCH ME

Pain

Infection

Nutrition

Constipation

Hydration

Medication

Electrolytes

Coma is

no signs of wakefulness and awareness lasting for less than 2-4 weeks (doesn’t respond to pain, voices, environment)

vegetative state is when

the person is awake but not aware, doesn’t show responses or emotions, is in the state doe a long time 4 weeks (continuing vegatative state) greater than 6 months (Non- TBI permanent) to greater than 12 months (TBI permanent)

What is brain death

brain can no longer maintain internal homeostasis

Unresponsive coma with bilateral absence of motor responses, no apnea, no brainstem functions, need to establish an etiology in absence of reversible conditions

What is cerebral death

death of cerebral hemispheres exclusive of brainstem and cerebellum with no responses, survivors remain in coma, emerge into a vegetative state and progress into a minimally conscious state

Pathophysiology of seizures

sudden, transient, excessive electric activity within the brain (neuron firing), jerky (rapid and repeated) contract-relax body movements,

Types of seizures (SPAM)

Sensory, psychic, autonomic, or motor,

partial or generalized and lead to loss of consciousness

What is an aura

perceptions experienced a few sec/hrs before seizure (or migraine) begins

Etiologic factors for seizures

Epilepsy: more then 2 unprovoked seizures, CNS lesions: Meningitis, MS, Tetanus, Trauma, Biochemical disorders: elevated bilirubin in kids, hypoglycemia, fever, lead poisioning

Data processing deficits

Agnosia, Dysphasia, Aphasia,

What is agnosia

inability to process sensory information (tactrile, visual, auditory)

What is dysphasia

Reduced ability to speak or write

What is Aphasia

Complete loss of comprehension or production of language

Types of cognitive functions

Attention, memory, language, perception, decision making, problem solving

Types of cognitive impairment

Mild cognitive impairment, dementia

What is dementia

progressive failure of cerebral functions that is not caused by an impaired level of consciousness

What do you lose with dementia

orientation, memory, language, judgement, decision making

3 causes of dementia

Alzheimer disease, vascular dementia, dementia with lewy bodies (DLB)

Pathophysiology of dementia

Neuron degeneration, brain tissue compression, atherosclerosis, brain trauma

Pathophysiology of Alzheimer’s disease

Premature neuron death + cellular changes:

Amyloid plaque (senile plaque) accumulates in extracellular spaces

neurofibrillary tangles intracellularly (twisted filament bundles)

Intracellular vacuoles, cell swelling & death which shrinks the brain

What is alzheimer’s disease

Structural changes in the brain leading to dramatic decline in intellectual functions

3 theories about the cause of alzheimer’s

Mutation in gene coding amyloid precursor protein, alteration in apolipoprotein E, Impairment in choline acetyltransferase

Clinical manifestations of alzheimer’s disease

Forgetfulness, emotional upset, disorientation, confusion, lack of concentration, decline in abstraction, problem solving, and judgement

What is the circle of willis made of?

Internal carotid artery, middle cerebral artery, basilar artery

Cerebral blood flow is

affected by metabolic activity of the brain. arterial gas tensions, cardiac output and is controlled by constant adjustments in perfusion pressure and cerebrovascular resistance

What is cerebral perfusion pressure

(CPP = Mean Arterial Pressure - Intracranial Pressure)

MAP: Cardiac output x Systemic vascular resistance

stages of Increased intracranial pressure

Stage 1: minimal increase

Stage 2: systemic arteriolar vasoconstriction to increase MAP and Cerebral perfusion pressure to maintain neuronal oxygenation

Stage 3: Sustained increased ICP approaching MAP. reduces perfusion greatly

Clinical manifestations of increased intracranial pressure

headache, eye changes, confusion, shallow breathing, increased blood pressure, n/v

What is the normal intercranial pressure

5 to 15mm Hg

what is cerebral edema

Increase in the fluid (intracellular or extracellular) within the brain

Pathophysiology and types of cerebral edema

Vasogenic: disruption of BBB, intravascular proteins/fluid escape to brain parenchyma

Cytotoxic: BBB is intact, toxins impair cellular metabolism

Interstitial: Disruption of Blood-CSF barrier, CSF flows to interstitial space

What is hydrocephalus

Abnormal accumulation of CSF in the ventricles and subarachnoid space within the brain.

What causes hydrocephalus

Congenital & Acquired: bleeding in CSF spaces, trauma, infection, cancer, surgery etc.

Pathophysiology of hydrocephalus

Interference in CSF flow, Increased intracranial pressure

Clinical manifestations of hydrocephalus

enlarged head, irritability, vomiting, impaired cognitive functions

What are Nociceptors

Receptors for pain that are free nerve endings in skin, muscle, joints, arteries, viscera.

They can also detect chemical, mechanical and thermal stimuli

What is the pathway of pain

spinothalamic tract

what is transduction of pain

activation of nociceptors

what is transmission of pain

conduction to dorsal horn and up via spinal cord

What is perception

awareness of pain

what is modulation

facilitation or inhibition of transmission before during or after perception

Types of neuromodulators

excitatory: substance P, glutamate

Inhibitory: GABA, glycine, serotonin, norepinephrine, endorphin

what are endogenous opioids

short sequences of amino acids that bind to opioid receptors and produce similar effects to opiates (morphine)

What are types of opioids

Endorphins: block transmission of pain signal, produce euphoria

Enkephalins

Dynorphins

Endomorphins

What is pain threshold

point at which the stimulus is perceived as pain

What is perceptual dominance

pain in one location causes an increased threshold in another location

what is pain tolerance

duration of time or the intensity of pain that a person will endure before initiation of pain responses

What is Psychogenic pain

physical pain that is caused, increased, or prolonged by mental, emotional, or behavioural factors

What is referred pain

Pain in an area distant from its point of origin but is supplied from the same spinal segment

Types of acute pain

Acute somatic - arises from skin, joints, muscle. A delta fibres: pain is sharp and localized

CFibres: dull, aching and poorly localized

Acute visceral - pain in the internal organs and linings of body cavities, transmitted by c fibres: poorly localized with aching, throbbing or intermittent cramping, often radiating or referred

what is Chronic pain

persistent or intermittent pain lasting 3-6 months minimum with varied patterns. Produces significant behaviour and psychologic changes, with no physiological signs

Types of chronic pain

Chronic postoperative pain, Cancer pain, Neuropathic pain (trauma or nerve disease affecting peripheral or central nervous systems)

How does age affect temperature production

pediatrics produce heat but cannot conserve it, aging: slow blood circulation and vasoconstrictive response and decreased metabolism, sweating, shivering and perception of heat and cold

Heat loss includes

oRadiation

oConduction

oConvection

oVasodilation

oDecreased muscle tone

oEvaporation

oIncreased respirations

oVoluntary measures

oAdaptation to warmer climates

Heat production includes

oChemical reactions in metabolism

oSkeletal muscle contraction

oChemical thermogenesis

oVasoconstriction

oVoluntary mechanisms

What is a fever

high temp to reset the hypothalamic thermostat including pyrogens: exogenous and endogenous

Benefit to fevers

kills organisms, promotes lysosomal breakdown and destruction of cells, increases lymphocytic transformation, Promotes antiviral interferon production and phagocytosis

What is hyperthermia

not mediated by pyrogens, 41*C is when nerve damage produces convulsions*,* 43*C is death

What is malignant hyperthermia

complication of inherited muscular disorders precipitated by inhaled anesthetics and neuromuscular blocking agents.

Pathophysiology of malignant hyperthermia

Impaired calcium release/uptake during muscle contraction, increased oxygen consumption and lactic acid production

Clinical manifestations of malignant hyperthermia

sustained muscle contractions, absent reflexes, fixed pupils, apnea, flat ecg

Different types of hyperthermia

heat cramps, heat exhaustion, heatstroke

What are heat cramps

severe spasmodic cramps in abdomen and extremities following exercise in hot weather.

prolonged sweating and associated sodium loss

What is heat exhaustion

a result of prolonged high core or environmental temperatures resulting in prolonged vasodilation and profuse sweating

Clinical manifestations of heat exhaustion

Dehydration, depressed plasma volumes, hypotension, decreased cardiac output, tachycardia, dizziness, confusion, weakness, nausea, syncope

What is heatstroke

potentially lethal condition resulting of an overstressed thermoregulatory center when the brain cannot tolerate temperatures over 40.5*C

Clinical manifestations of heatstroke

Cerebral edema, degeneration of the CNS, Swollen dendrites, renal tubular necrosis, death

Pathophysiology of hypothermia

CNA and resp. depression, vasoconstriction and slow circulation, ice crystals form inside the cells causing them to rupture and die, slow rate of cellular metabolism, increased blood viscosity, coagulation and tissue damage

Types of hypothermia

Accidental hypothermia - sudden immersion in cold water or prolonged exposure to cold

Therapeutic hypothermia - used to slow metabolism and preserve ischemic tissue during surgery, may lead to v fib and cardiac arrest

How does CNS trauma lead to temperature change

Inflammation, increased ICP, intracranial bleeding

2 phases of sleep

REM sleep (20-25% of sleep) aka paradoxic sleep

Non-rapid eye movement sleep: 75-80% of sleep time

2 types of primary sleep disorders

Dyssomnias & parasomnias

what are Dyssomnias

Insomnia, obstructive sleep apnea, primary and secondary hypersomnia, disorders of sleep-wake cycle

What are parasomnias

Somnambulism, night terrors, restless legs syndrome, violent behaviours

What are secondary sleep disorders

alterations in the quality and or quantity of sleep caused by primary diseases such as depression, pain, sleep apnea syndromes, alterations in thyroid hormone secretions

pathophysiology of TBI

Brain hematoma: subdural, epidural, intracerebral

Focal or diffuse neuronal injury

What is a concussion

A TBI causing alterations in brain functions +/- Loss of consciousness

Clinical manifestations of a concussion

headache, sleep disturbances, n/v, blurred vision, impaired attention, reduced processing speed, drowsiness, emotion/behaviour changes

Pathophysiology of spinal cord injuries

Hemorrhage, edema in grey matter, white matter and meninges, microcirculation blocks lead to ischemia and necrosis, level of injury +2 Segments above and below, 24h regain circulation in white matter, grey matter takes longer, inflammation and healing start 36-48h, collagen repair occurs within 3-4 weeks

Spinal Cord injury causes

hyperextension, flexion, axial compression, flexion-rotation injury

Paraplegia injury occurs in the

thoracic, lumbar, or sacral regions and impairs the motor, sensory function in lower limbs

Quadriplegia injury occurs in the

C1-C7 and impairs the motor or sensory function of all limbs and the torso

What is spinal shock

Stopping of spinal cord activities at and below the level of injury resulting in complete loss of reflex function below level of lesion

Types of fractures of the spine

Simple fracture, compression fracture, comminuted fracture, Dislocation

Degenerative disorders of the spine

Spondylolysis, Herniated intervertebral disc, Spinal stenosis

What is spondyolysis

defect of the L5 in pars interarticularis that causes pain and reduced mobility and is commonly sports related. Can progress to spondylolisthesis (slipping of vertebra)

What is spinal stenosis

Abnormal narrowing of spinal canal mostly cervical and lumbar caused by herniated disc, trauma, or tumor

Clinical manifestations of spinal stenosis

Could be asymptomatic, discomfort/pain of the neck/lower back, numbness, tingling, weakness of upper/lower limb, bilateral symptoms

Pathophysiology of aneurysms

Localized blood filled bulge in the blood vessel wall, caused by weakened vessel wall. Can increase in size and rupture causing bleeding, subsequent hypovolemic shock and death

types of CVA (stroke)

Cerebral ischemia (thrombotic stroke & Embolic stroke) Cerebral hemorrhage

Pathophysiology of headaches

Traction/irritation of meninges and spasm/dilation of bv, stimulating nociceptors

pain originates from nearby pain-sensitive structures: periosteum, muscles, sub q tissues

Types of headaches

TMJ, Sinus, Cluster, Tension, Migraine, Neck

Infections of the CNS

Meningitis, Encephalitis, meningo-encephalitis, Abscess

What is encephalitis

inflammation of brain tissues caused by arthropod-borne viruses and herpes simplex virus

Types of abscess’s of the CNS

Brain abscess - early: low grade fever, headache, neck pain/stiffness, confusion, drowsiness, sensory/communication deficits

late: distractibility, memory deficits, visual impairment, ataxia, dementia

Spinal cord abscess - severe pain, spasms of the back muscles and limited movement, progressive compression symptoms, paralysis