Neuro pathophysiology

Patho neuro wiki notes



The nervous system consists of the brain, spinal cord and nerves.
Neurological alterations can occur due to structural defects, infectious processes, or injury. These may be congenital or acquired.

*Remember the cranium's volume is 80% brain tissue, 10% CSF and 10% blood.
If this delicate balance is not maintained problems occur.

*Children with fontanels and sutures can compensate to a degree, this swelling results in hydrocephalus.

*After age 12, sutures are fused and will not open so compensation of this nature cannot occur, resulting in increased intracranial pressure!

Diagnostics often used to detect pathology include:
Computed axial tomography (CT)
Magnetic Resonance Imagery (MRI)
Electroencephalogram (EEG)

Central nervous system (CNS)
Peripheral nervous system (PNS)

Meninges
A set of three tough membranes which encase the spinal cord
Dura mater – outer
Arachnoid middle layer spider web like vascular system
Pia mater – inner most layer rest on brain and spinal cord

Cerebrospinal fluid
Plasma like liquid that fills the space between the arachnoid and pia layers
Choroid plexus cells in the ventricles continuously produce

Blood brain barrier
Protective mechanism provided by relatively impermeable capillaries in the brain. This barrier limits the passage of potentially damaging materials into the brain and controls the balance of electrolytes, glucose and proteins.

There is a similar Blood CSF barrier at the choroid plexus.

Cerebral hemispheres
Longitudinal fissure separates the right and left brain hemispheres
Left brain – logical thinking, analytical, communication
Right brain – appreciation of art, music, behavioral changes

Each hemisphere has 4 major lobes – frontal, parietal, occipital and temporal

Frontal –
Intellectual function and personality
Skilled movements
Voluntary movements
Speech

Parietal –
Sensation

Occipital –
Vision

Temporal –
Hearing
Smell

Diencephalon
Central portion of brain
Contains the thalamus and hypothalamus

Thalamus
Relays sensory information from spinal cord to the cerebral cortex
Interprets sensory messages such as pain, temperature, pressure

Hypothalamus
Autonomic nervous system, respiration, heartbeat
Link with endocrine system, directs hormone secretions of the pituitary
Controls homeostatic functions, body temperature, fluid balance
Centers for thirst, hunger

Cerebral cortex
Receives sensory information from skin, muscles, glands, organs
Messages to move skeletal muscle
Integrates incoming and outgoing nerve impulses
Performs associative activities, thinking, learning, remembering

Basal nuclei
Plays a role in slow sustained movements
Suppress useless patterns of movement

Brain stem
Pons/midbrain/medulla
Pons nerves regulate sleeping and breathing
Midbrain relay for visual and auditory information
Medulla conduction pathway for all ascending and descending nerve tracts so…
Transmits impulses between brain and spinal cord
Regulates heart rate, peripheral vascular resistance (BP)
Breathing, swallowing, coughing, vomiting, Origin of many cranial nerves
Reflex center for movements of eyes, head and trunk
Role in consciousness
Of the 12 cranial nerves, 10 exit from the brain stem

Cerebellum
Communicates with other regions of the brain
Coordinates subconscious movements of skeletal muscles
Contributes to muscle tone, posture, balance, equilibrium

Basal nuclei
Coordination and control of body movement

Reticular activating system
Neurons scattered in brain stem that controls arousal or awareness… in other words this system decides which incoming brain signals to ignore or notice

Limbic system
Nuclei and connecting fibers in the cerebral hemispheres that encircle the superiour part of the brain stem. Responsible for emotional responses so it has connections all over the brain…Part of the hypothalamus is involved with the limbic system…so blood pressure and heart can respond to fear or pain. Any cognitive decision made has emotion attached to it…

Corpus callosum
A wide, flat bundle of neural fibers beneath the cortex at the longitudinal fissure. It connects the left and right cerebral hemispheres and facilitates communication.

Blood supply to brain
Via internal carotid arteries and the vertebral arteries, the internal carotids have baroreceptors, which facilitate BP, Ph and O2 changes. Blood flow constant b/c the brain cells use O2 and glucose and there is no reserve.

Cranial nerves
12 pairs of cranial nerves

Spinal cord
Protected by vertebral column, meninges and CSF. Cord continuous with medulla oblongata. Ends at first lumbar, then just nerve roots, so lumbar puncture usually performed at L3/L4, so no damage.

Spinal nerves:
31 pairs of spinal nerves.
8 cervical nerves
12 thoracic
5 lumbar
5 sacral
1 coccygeal

Reflexes
Automatic rapid involuntary responses to a stimulus

Neurons
Nerve cells

Conduction of impulses

Synapses/chemical neurotransmitters
Release of chemical neurotransmitters which may stimulate or inhibit conduction of the impulse.

Many neurotransmitters –
Acetylcholine (Ach)
Catecholamines – norepinephrine (SNS), epinephrine (SNS), dopamine
Other transmitters –serotonin, histamine, gamma-aminobutyric acid (GABA)

Transmitters studied with depression- norepinephrine, dopamine excitatory

Autonomic nervous system:

Sympathetic (SNS) – fight or flight

Parasympathetic (PNS) – rest and digest





Effects of neuro dysfunction:
Broad range of symptoms depending on area of dysfunction
Increased intracranial pressure
Level of consciousness changes (LOC)
Motor dysfunction
Sensory deficits
Visual loss
Language disorders –
Aphasia inability to understand or express language
Expressive, motor aphasia – inability to speak or write
Receptive, sensory aphasia – inability to read or understand spoken work
Global aphasia – combination
Fluent (normal pace, made up words) non fluent – (slow, labored speech)
Dysarthria- words not articulated clearly
Agraphia – impaired writing
Alexia – impaired reading
Agnosia – loss of recognition or association

Increased intracranial pressure:
80/10/10 volume
Non expandable skull
Addition of fluid as blood, exudate, swelling, or a mass = brain compression/death

Body attempts to compensate so may have been going on awhile before noticed

Initial S&S:
LOC changes – depressed –lethargy
Severe headache – stretching of dura and walls of vessels
Vomiting – pressure on emetic center in medulla
Papilledema – looking through pupil into window into brain

Vital signs –
Systemic vasoconstriction to increase blood to brain in response to ischemia = ^BP
Increased pulse pressure (diff. between systolic and diastolic BP)
V respiratory rate to correct low carbon dioxide levels
V heart rate
Pressure on the oculomotor nerve affects size and response of pupils

*Herniation or pressing down on brain stem can occur

Seizures:
Caused by uncontrolled electrical activity in the brain
Can be partial, generalized or unclassified
Simple or complex

Causes:
Fevers
Infections
Cardiac anomolies
Trauma
Hypoxia
Breath holding spells
Gastroesophageal reflux
Epilepsy
Genetic factor
Idiopathic causes

Infant seizures can be due to congenital defect, birth injury, endocrine dysfunction, CNS infection, hypoglycemia
Older children trauma or infection, changes in diet, hydration status

Febrile seizures
Brief, clonic, tonic/clonic, simple or complex
Usually develop after a high fever but can be as low as 100 F
Simple - <15 min., few seconds, don't recur in 24 hours
Complex - >15 min., focal attributes, can reoccur on the same day
Rarely occur before 9 months or after 5 years

Unprovoked first seizure
without cause
<50% will have a second
Family history, developmental history, labs,

Epileptic seizures:
Presence of more than one unprovoked seizure
Childhood epilepsy may be a sign of CNS immaturity
More than 1/3 will be off medication and no longer have seizures by 23 years
Poorer prognosis if develop in infancy or adolescence, difficulty in management, cerebral palsy

Pathophysiology:
Electrical discharge of hyperexcited brain cells in epileptogenic focus
triggered by environmental or physiological stimuli (emotional stress, anxiety, fatigue, infection, metabolic diff)
Small area of brain = focal seizure

Status epilepticus = prolonged or a series of convulsions which occurs for a prolonged period and does not allow the child to regain consciousness before another begins. This is an emergency which can cause exhaustion, respiratory failure and death.
Refractory seizures last for more than 60 minutes

Clinical manifestations:
Simple Partial
Partial - small area of brain, simple - do not lose consciousness
Starts at any age and can have a variable number of seizures a day
Last <30 seconds, with no loss of consciousness, no automatisms, and no postictal impairment or confusion
localized motor symptoms
Somatosensory, psychic, autonomic symptoms
Aura, may be the sole manifestation
movements may involve one extremity
abnormal brain discharges unilateral
Aversive seizure - turn away from the side of focus
Rolandic (Sylvan) tonic-clonic involving face and mouth during sleep
Jacksonian march or Jacksonian seizure, rare in children
Simple partial with sensory signs may include parathesia, numbness, tingling, visual sensations or images, motor phenomena


Complex partial seizures
Partial - small part of the brain, complex - complicated because they lose consciousness!
Period of altered behavior with no recollection of the event
Inability to respond to the environment
More complicated because there is impaired consciousness
Postictal impairment and mental disorientation, Drowsiness, confused
Rarely more than 2 a day, usually >60 seconds
Aura, deja vu, abdominal pain, taste, odor, visual changes
Stops activity and begins staring or nonpurposeful actions (automatisms)

Generalized
Diffuse electrical activity, involve both hemispheres of the brain
Always lose consciousness!
No aura but prodrome of vague symptoms
Under age 4 associated with developmental delays, learning disabilities,
Uncontrolled motor involvement with movements and spasms, bilateral and symmetrical

*4 types - tonic/clonic, myoclonic, absence or akinetic

Tonic/Clonic (formally known as grand mal) Tonic phase 10-20 seconds, clonic 30 seconds but can last to a half an hour, occur without warning, postictal state, no remembrance of event.

Causes:
Fevers
Infections
Cardiac anomolies
Trauma
Hypoxia
Breath holding spells
Gastroesophageal reflux
Epilepsy
Genetic factor
Idiopathic causes
Stroke


Brain Tumors
Space occupying can ^ ICP
*Benign or malignant they occupy space violating the 80/10/10
Gliomas largest category of malignant brain tumor, further differentiated
Tumors based on sites – meningioma, adenoma (pituitary)
Poor margins, destruction of tissue, obstruction of CSF

Signs and Symptoms:
No symptoms until begin to brain compression or CSF obstruction
Symptoms dependent on location
Headache on awaking
Vomiting
Neuromuscular changes
Behavioral changes
Cranial nerve neuropathy head tilt, visual changes
Vital sign changes
Seizures
Bulging fontanelle
Nuchal rigidity
MRI, CT, angiography, EEG diagnostic
Lumber puncture but must be careful

Treatment:
Surgery
Radiation
Chemotherapy water-soluble drugs can pass the blood brain barrier

Neuroblastoma:
Most common malignant tumor in children
Silent, discovered 70% of time after metastasis
Staged form I-IV
The younger child generally fairs better


TIA

Temporary localized reduction in blood flow to the brain
Attacks last a few minutes, rarely longer than 1-2 hours

Causes:
Atherosclerosis
Vasospasm
Small embolus

Signs and symptoms:
Location of ischemia
Consciousness maintained
Muscle weakness
Visual disturbances
Numbness or parasthesia

Stroke

In US ~ one stroke every 45 seconds
Infarction of brain tissue
Consequence of ischemia from atheroma, embolus or ruptured vessel
5 minutes or less irreversible brain cell damage

Effects vary with cause:
Occlusion due to atheroma
Embolus
Intracerebral hemorrhage
Cerebral edema and increasing area of infarction first 24-72 hours

*Inflammation and pressure must be minimized to increase perfusion

Complications:
Immobility
Aspiration
Constipation
Paralysis, contractures
Behavioral changes:
Speech difficulty etc

Treatment:
‘Clot busting agents’ tissue plasminogen (tPA)
Glucocorticoids

The Brain, A stroke of insight





Stroke

























CVA

Aneurysms
Localized dilation in artery
Asymptomatic
Hypertension may increase size, symptoms
Rupture (irritation) causes inflammation, vasospasm, ICP

S&S:
Nuchal rigidity – stiff, extended neck, escaped blood irritates spinal nerve roots
Photophobia
Headache
Confusion
Severity increases with size of bleed
Blinding headache, vomiting, seizures, coma…

Treatment:
35% die during initial rupture
Treat surgically, optimally prior to rupture


Meningitis - Bacterial and viral

Infection affecting the meninges caused by bacteria such as meningococci, pneumococci, and Haemophilus, viral agents or tuberculosis.

Bacterial Meningitis is an infection of the meninges and the CSF.
The Haemophilus vaccine (Act-Hib, Pedvax) and the pneumococcal (Prevnar, PCV 13) have decreased bacterial cases.
These two bacteria along with Neisseria meningitis (meningococcus) cause 95% of cases older than 2 months of age.
The meningococcal vaccine (Menactra) is available for ages 11-55 years old.

Incidence
1 month and 5 years bacterial
school age and adolescents - meningococcal

Pathophysiology
This infection generally comes from vascular dissemination from another foci of infection.
Less frequently from the mastoid or paranasal sinuses.

*As in any infectious process exudate (pus) covers the brain and can clog the flow of CSF. Inflammation, edema and exudate add extra volume violating 80/10/10 =
increased intracranial pressure!

Diagnosis:
Diagnosis is made by a lumbar puncture.
Examination of CSF reveals elevated WBCs and protein, glucose is reduced, why?
Blood cultures
Nose and throat cultures.
Ct scan

Signs and symptoms:
Onset may mimic the flu and occur over a couple of days or it may be abrupt.
fever
headache
chills
seizures
irritability
agitation
vomiting
Photophobia
nuchal rigidity
delirium, stupor and coma may also occur...

Infants and young children have less specific signs and symptoms. Poor feeding, a bulging fontanel (due to increased intracranial pressure!), irritability, vomiting and seizures may be more typical of infants. A petechial rash can indicate a fulminating course of meningococcemia. This is a medical emergency.


Management includes:

Isolation
Antimicrobial therapy
Hydration
Maintanence of ventilation
Reduction of increased ICP
Management of septic shock
Control of seizures
Control of temperature
Treatment of complications
Appropriate antibiotic therapy
Dexamethasone helps with increased ICP but is not advised for viral meningitis
Cephalosporins are drug of choice

Complications include shock, disseminated intravascular coagulation syndrome (DIC), seizures, hearing loss, 10-15% fatal


*Aseptic or viral meningitis is self limiting, it must be differentiated from bacterial and care is supportive*


Reyes Syndrome:


Traumatic Brain Injuries (TBI)

*Remember the cranium's volume is 80% brain tissue, 10% CSF and 10% blood.


Concussion:
Most common head injury.
May not necessarily lose consciousness
Confusion and amnesia hallmark
Post concussion syndrome – last several days to several months, headaches, memory loss,
Second Impact Syndrome - returning to play before complete healing is dangerous!

Pathophysiology – tearing of nerve fibers, release of acetylcholine and decreased amounts of oxygen






Contusion/laceration
Visible bruising, tearing of cerebral tissue
Petechial hemorrhages at the site – coup
Hemorrhages remote from the site – contrecoup
Infant’s brains are very pliable, so is the skull

Shaken Baby Syndrome –
Profound neurological impairment
Retinal hemorrhages
Subarachnoid
Subdural hemorrhages
Unconsciousness
Scarring, paralysis…

http://dontshake.org/

Fractures
Young children > skull flexibility
However may still tear an artery producing hypovolemic hypotension
Linear fractures
Comminuted - multiple linear
Depressed fractures
Basilar - frontal, ethmoid, sphenoid, temporal, occipital 80% subcutaneour bleeding posterior neck area, raccoon eyes, hemotympanum bleeding behind tympanic membrane
Open –
Diastatic

Complications:
Hemorrhage, edema, infection, herniation, compression
Rapidly fatal or slow and insidious

Epidural hemorrhage
Arterial brain compression occurs rapidly
Uncommon in children under 4
*Bleeding violates the 80/10/10 so increased intracranial pressure!

Subarachnoid hemorrhage:
Bleeding from torn veins during an accident, slow diffuse spread of blood into CSF, generalized pressure.
*Bleeding violates 80/10/10 so increased intracranial pressure!

Subdural Hematoma:
Bleeding from torn bridge veins pours into area compressing brain.
*Bleeding violates 80/10/10 so increased intracranial pressure!





Spinal injuries



References:

Gould, B. E., & Dyer, R. M. (2011). Pathophysiology for the health professions (4 ed.). St. Louis, Missouri: Saunders Elsevier.


Story, L. (2012). Pathophysiology: A practical approach. Sudbury, MA: Jones & Bartlett Learning .

Videos:

Meet the brain
http://youtu.be/P0QE2--CIlw

The brain
http://youtu.be/hIo6ck75EZc

The Brain: A Stroke of insight
http://youtu.be/F4-twSim8l8

Traumatic brain injury
http://youtu.be/DMh_Uiiu6VU

Spinal cord injuries
http://youtu.be/zxpb1-okVi