Pathophysiology Unit 13 The Neurologic System Part 1

Brain

*Three structures protect the brain: the skull, meninges, and cerebral spinal fluid
*The skull is comprised of bone with various thicknesses. Sutures in the adult are remnants of neonatal life and are immovable joints of the facial bones and skull
*The me

Cerebral spinal fluid (CSF)

�Is a clear and colorless liquid that cushions the brain and spinal cord
�It is formed from the choroid plexuses in the ventricles (500-800ml/day)
�CSF flow: into the subarachnoid space->into the arachnoid Villi->into the venous blood stream

Cerebral hemispheres

Each hemisphere is divided into four different lobes (frontal, occipital, temporal, and parietal)

Diencephalon

Is the center of the brain and is surrounded by the hemispheres. It contains the thalamus and hypothalamus

Brainstem

Connects the brain to the spinal cord

Cerebellum

Is below the occipital lobe and acts to coordinate equilibrium, maintain posture and coordinate movements

Hemiparetic gait

Vary depending on area of the body affected and the severity of hemiparesis (weakness on one side of the body, such as CVA-cerebral vascular accident/stroke)

Ataxic gait

Legs are spread wide apart to compensate for an imbalance when standing or walking. Often a staggering gait. Usually results from lesions of cerebellum (cerebral palsy)

Steppage gait

High stepping or slapping walk (muscular dystrophy, foot drop, etc..)

Gait

is the pattern of movement of the limbs

Shuffling gait

Short steps to the point that little forward movement is noted. Walk somewhat stopped with arms and legs slightly flexed (Parkinson's)

Dysphasia

The impairment of comprehension or production of language. Lack of coordination in speech, and failure to arrange words in an understandable way

Dysphonia

Difficulty or pain in speaking. Can vary in sincerity from hoarse voice to an absent voice where the patients is unable to speak

Dysarthria

The inability to articulate spoken words. Due to emotional stress, paralysis, brain injury, in coordination, or spasticity of the muscle used for speaking

Memory

The ability to recall prior input

Orientation

Person place and time

Intelligence

The ability to apply prior information to new situation and to use reason to solve problems (i.e. vocabulary, serial calculation, judgment, abstraction)

Sensory systems

Part of the nervous system consisting of sensory receptors that receive stimuli from internal and external environments, and neural pathways that conduct this info to the brain and parts of the brain that process this info

Dermatomal Patterns

�Areas of the skin that is mainly supplied by a single spinal nerve, and each of these nerves relay sensation (pain) to the brain
�(8 cervical nerves, 12 thoracic nerves, 5 lumbar nerves, and 5 sacral nerves)

Tactile sensation

Sensation produced by pressure receptors in the skin (touch of silk, greasy feeling)

Proprioception

�"one's own" or "individual" self
�Is the sense of the relative position of neighboring parts of the body and strength of effort being employed in movement
�Even with the eyes closed we know where our own body parts are, if we are moving them, and with wh

Specificity Theory

Pain regarded as a separate sensory modality

Pattern Theory

Pain receptors share pathways with other sensory modalities

Gate control Theory

�A modification of the specificity theory in response to pattern theory challenges
�Internucial neurons activated by large diameter touch fivers disrupts transmission of pain through small diameter myelinated and unmyelinated nerves

Neuromatrix Theory

Is revision to the gate control theory. Postulates that a multifaceted and widely distributed neural network that is individual to the person and influenced by genetics and sensory influences sets the parameters from the personal pain response

Pain mechanisms and pathways

�Nocieceptors respond to several types of stimulation such as mechanical, thermal and chemical
�Fast conduction fivers in the neospinothalmic tract are mainly responsible for sharp fast pain conduction
�Brain center connections in the thalamus and cortex

Cutaneous Pain

Sharp burning pain that has origin in skin or subcutaneous tissues (paper cut)

Deep somatic pain

More defuse and throbbing pain that originates in structures such as muscles, bones, and tendons, and radiates to surrounding tissues

Visceral pain

Defused and poorly defined pain that results from stretching distension, or ischemia of tissues in a body organ (renal colic)

Referred pain

Pain that originates at a visceral site that is perceived as originating in part of the body wall that is innervated by neurons entering the same segment of the nervous system

Acute pain

Usually results from tissue damage and is characterized by autonomic nervous system responses (pain lasting less than 6 months)

Chronic pain

Persistent pain accompanied by loss of appetite, sleep disturbances, depression, and other debilitating responses (pain lasting more than 6 months)

Pain management

�Assessment: careful and complete assessment of the nature, severity, location, and radiation of pain can assist the clinician in diagnosing, managing and relieving pain for the client
�Treatment: approaches to relieving chronic and acute pain differ

Pain sensitivity

Varies among individuals and under differing circumstances. Also varies according to the body part(s) involved

Neuropathic pain

Associated with peripheral or central nervous system pain that is unusual and or intractable sensory disturbances associated with disease or injury

Headache

Common and caused by a number of conditions

Pain in children and older adults

Frequently not recognized and not treated. A widely held false belief that children and older adults do not feel pain the same way as other patient populations confounds treatment

Pain threshold

Is closely associated with tissue damage and is defined as the point at which a stimulus is perceived as painful

Pain tolerance

Defined as the amount of pain a person is willing to endure before expecting an intervention

Consciousness

�A state of awareness of oneself and other environment and a set of responses to that environment
�Fully conscious individual respond to external stimuli with a wide array of responses
�Any decrease in the state of awareness and varied responses is a decr

Confused and disorganized

Confusion is a inability to think

Lethargy

May exhibit orientation to person, place and time, however, slow vocalization and decreased motor skills are present

Obtundation

�Awakening in response to stimulation /Continuous stimuli is needed for arousal
�Need continuous stimuli to maintain arousal, cannot be fully aroused

Stupor

�Vocalization only in response to vigorous stimuli/markedly decreased spontaneous movement in seen
�Vocalization to pain/decreased movement

Coma

�Displays no vocalization and no arousal to stimuli/brainstem is still intact
�Unresponsive cognitively

Arousal

Ability to maintain consciousness is a function of the RAS (Reticular activation system)

Glasgow test

Measures degree of arousal/highest level is alert and orientated/lowest level is comatose
*Eye opening
*Verbal response
*Best motor response

Cerebral Death

�Irreversible coma
�Death of the cerebral hemispheres exclusive of the brain stem and cerebellum
�The brain can maintain internal homeostasis (respiration, normal temp, normal GI, heart, etc)

Brain death

�Occurs when the brain is damaged so completely that it can never recover and cannot maintain the body's internal homeostasis
�Destruction includes the brain stem and cerebellum

Criteria for brain death

�Completion of all appropriate and therapeutic procedures
�Unresponsive coma no (motor reflex movements)
�Non spontaneous respiration
�Absent cephalic reflexes - no ocular responses to head turning or caloric stimulation, dilated fixed pupils
�Isoelectric

Delirium

�An acute confused state associated with over activity, typically develops over 2-3 days and is seen initially as difficulty in concentrating, restlessness, irritability, insomnia, tremulousness, and poor appetite (usually caused by medical issue or fever

Delusions

�False beliefs, no organic basis, treatable
�A false belief brought about without appropriate external stimulation and inconsistent with the individuals own knowledge and experience
�The most important delusions are those that cause people to harm themsel

Dementia

�Progressive disorder, over time
�Characterized by the loss of more than one cognitive (intellectual) function
�Declining intellectual ability, the person exhibits alterations in behavior
�May be decreased in orientation, general knowledge and information

Amnestic dementia

Affects the temporal lobe and the effect is the loss of recent memory

Cognitive dementia

Affects the cerebral cortex and the effect is the loss of remote memory

Intention dementia

Affects the frontal lobe and the effect is the loss of vigilance and executive function

Increased intracranial pressure (Increased ICP)

�Resulting from an increase in intracranial content (tumor, edema, excess CSF or hemorrhage)
�Rise in ICP form one component requires an equal reduction in volume of other components
�Most readily displaced content of the cranial vault is CSF

Stage 1 of ICP

Vasoconstriction and external compression of the venous system occur in an attempt to decrease further the ICP following CSF displacement

Stage 2 of ICP

With continued expansion of the intracranial content, the resulting increase in ICP may exceed the brains compensatory capacity to adjust to the increasing pressure

Stage 3 of ICP

Pressure in the intracranial vault begins to compromise neurotissues

Stage 4 of ICP

Herniation of brain tissue from one brain compartment to another

Brain Herniation

a deadly side effect of very high intracranial pressure that occurs when a part of the brain is squeezed across structures within the skull

Cingulate

�the most common type, the innermost part of the frontal lobe is scraped under part of the falx cerebri, the dura mater at the top of the head between the two hemispheres of the brain
�Involves the anterior cerebral artery. Key clinical sign is leg weakne

Central (transtentorial)

�This occurs when a downward shift or displacement, pushes the cerebral hemispheres, basal ganglia, diencephalons, mid-brain and finally the medulla through the tentorial incisura (notch).
�Structures involved are the reticular activation system and the c

Uncal

�Involves the cerebral peducle, occulomotor nerve, posterior cerebral artery, cerebral artery, cerebellar tonsils and respiratory center. Key clinical signs are hemiparesis, pupil dilatation, visual field loss and respiratory arrest
�This occurs when the

Cerebral Edema

�An increase in the fluid content of the brain tissue
�Results in increased extracellular or intracellular tissue volume
�Occurs after brain insult from trauma, infection, hemorrhage, tumor, ischemia, infarct or hypoxia
�Distorts the blood vessels, displa

Vasogenic Cerebral edema

�Clinically most important. Caused by increased permeability of capillary endothelium of the brain after injury to vascular structure
�BBB is disrupted->plasma protein leaks into extracellular spaces->they draw H2O to them->increases water content of the

Cytotoxic (metabolic)edema

�Toxic factors directly affect the neuronal, glial and endothelial cells
�Results in failure of active transport systems
�Cells lose K+ and gain larger amounts of Na+
�H2O follows by osmosis in the cells and cause the cells to swell

Ischemic edema

�Follows cerebral infarct (area of necrosis)
�Initially edema is confined to the intracellular compartment
�Later brain cells undergo necrosis and die
�Released lysosomes increase the BBB permeability by lyzing it

Interstitial edema

�Caused by movement of CSF from the ventricles into the extracellular spaces of the brain tissue
�Brain fluid volume mostly increases around the ventricles
�Increased pressure is in the white matter

Epidural hematoma

�Arterial bleed above the dura
�Incidence: 20-40 years old with major head trauma
�s/s: possible LOC, possible HA, vomiting, drowsy, confusion, seizure
�Rx: surgical intervention

Subdural hematoma

�Venous bleed below dura, may be acute or chronic
�Incidence: traumatic brain injury, elderly ETOH abusers
�s/s: HA, drowsiness, restlessness, agitation, confusion
�s/s: surgical intervention or noninvasive resolution

Intracerebral hematoma

�arterial or venous bleed within the brain tissue acts as an expanding mass
�incidence: increased with projectiles and debris or open trauma
�s/s: possible LOC, ICP changes, signs of Herniation
�Rx: may or may not be able to do surgical intervention

Subarachnoid hemorrhage

Blood escapes from a defective or injured vasculature into the subarachnoid space. Those at risk have intracranial aneurysms, intracranial malformations or hypertension

Focal Brain Injury

�Patho: injury causes small tears and therefore bleeding of brain tissue
�Incidence: peak 18-36 hrs post-injury
�s/s: change is affect, emotion, memory, behavior (related to area of brain involved)
�Rx: none except treatment of increased ICP or continued

Contusion

Type of focal brain injury
bruise on the brain, grossly observable trauma

Hemorrhage

Type of focal brain injury
epidural hematoma, subdural hematomas, intracerebral hematoma, and subarachnoid hemorrhage

Coup/Countrecoup

In head injury, a coup injury occurs under the site of impact with an object, and a countrecoup injury occurs on the side opposite the area that was impacted.

Diffuse Brain injury grades

�Grade 1-confusion, disoriented with momentary amnesia
�Grade 2-momentary confusion, retrograde amnesia 5-10 min
�Grade 3-confusion and retrograde amnesia from impact, antegrade amnesia

Concussion

Type of diffuse brain injury
�Resulting from force to the head, high levels of acceleration and deceleration
�Severity correlates with how much shearing force is applied to brain stem
�Refers to momentary interruption of brain function with or without LOC

Classic cerebral concussion

Patho: diffuse disruption of RAS (reticular activation system- a diffuse primitive system of interlacing nerve cells and fibers in the brain stem that receives input from multiple sensory pathways) producing neurologic dysfunction and immediate LOC for up

DIA (Diffuse Axonal injury)

�Type of diffuse brain injury
�Cerebral edema without visible trauma/shearing or tearing or neurons
�A primary injury with diffuse microscopic damage to axons in the cerebral hemisphere, corpus callosum, and brain stem
�It is responsible for most cases of

Mild DIA

Immediate LOC, may have posturing, prolonged stupor, or restlessness

Moderate DIA

Immediate LOC, with a Glasgow 4-6 initially and 6-8 by 24 hours, permanent deficits in memory, attention, abstraction, reasoning, language, mood, and vision/perception

Severe DIA

Immediate autonomic dysfunction that resolves over a few weeks, profound loss of coordination motor movements, verbal and written communication, inability to learn or reason, inability to control behaviors