Pathophysiology 16

Seizures

represent abnormal, excessive hypersynchronous discharges of cerebral neurons with transient alterations in brain function.

Arousal
Awareness

What are the two components of consciousness?

diffuse bilateral cortical dysfunction
bilateral subcortical (reticular formation, brainstem) dysfunction,
or localized hemispheric dysfunction

A decreased level of arousal can be caused by...

Alteration in breathing pattern
Level of coma

What reflects the level of brain dysfunction?

Level of brainstem function,
Drug action,
Response to hypoxia and ischemia

Pupillary changes reflect changes in what?

nystagmus (rapid, involuntary, oscillatory motion of the eyeball)
divergent gaze

Alterations in brainstem function are reflected by...

Generalized motor responses or no responses

Level of brain function is indicated by...

location-related,
generalized,
undetermined

There are three categories of epileptic syndrome

Aphasia

Loss of language comprehension or production

Dysphasia

An impairment of comprehension or production of language

Wernicke Dysphasia

A disturbance in understanding all language�verbal and reading comprehension

Conductive dysphasias

Result from disruption of temporal lobe fibers, with a failure to repeat words but an ability to initiate speech, writing, and reading aloud.

Anomic Dysphasia

An inability to name objects, people, or qualities

Transcortical Dysphasias

Involve an ability to repeat and recite

Broca Aphasia

An expressive dysphasia of speech and writing but with retention of comprehension.

Global Aphasia

Involves anterior and posterior speech areas, with expressive and receptive aphasia.

Agnosias

A defect of pattern recognition and may be tactile, visual, or auditory. Caused by dysfunction in the primary sensory area or the interpretive areas of the cerebral cortex.

Stage 1

Alteration of cerebral blood volume - vasoconstriction and external compression of venous system represents which stage of intracranial hypertension?

Stage 4

When the brain shifts from the compartment of greater pressure to a compartment of lesser pressure, this is which stage of intracranial hypertension?

Stage 3

Which stage of intracranial hypertension is when auto regulation of blood vessels is lost - hypostatic blood (cranial pressure is so high that blood cannot get through), increased volume, increased intracranial pressure.

Stage 2

Systemic arterial vasoconstriction to elevate blood pressure to overcome intracranial pressure occurs in which stage of intracranial hypertension?

Central Transtentorial Herniation

Occurs when the diencephalons shift directly downward through the tentorial notch.

Uncal Herniation

Shifting of the uncus and/or the hippocampal gyrus from the middle fossa through the tentorial notch into the posterior fossa.

Uncal Herniation

Compresses the ipsilateral third cranial nerve impairing parasympathetic function, contralateral third cranial nerve, and then the mesencephalon, inducing coma.

Uncal Herniation

Decreasing level of consciousness
Poor concentration
Sluggish pupils before fixation and dilation

Central Transtentorial Herniation

Miotic pupils
Drowsiness
Rapid transition into unconsciousness
Small reactive pupils to dialated and fixed

Vasogenic

A type of cerebral edema where increased permeability of capillary endothelium after injury to vascular structure. Disruption of the blood/brain barrier.

Cytotoxic (metabolic)

A type of cerebral edema where toxins cause the failure of the cellular active transport system. Cells lose K+, gain Na+ and swell.

Ischemic Edema

A type of cerebral edema which follows infarction or the loss of blood flow to an area of the brain.

Interstitial Edema

A type of cerebral edema which involves the transependimal movement of CSF from ventricles into extracellular spaces

Hydrocephalus

Excess fluid within the cranial vault, subarachnoid space, or both.

noncommunicating (internal)

A type of Hydrocephalus which may result from congenital abnormalities or mass lesions (tumor) or from impaired absorption of CSF from the subarachnoid space.

communicating (extra ventricular)

A type of Hydrocephalus which is most commonly caused by subarachnoid hemorrhage, developmental malformation, head injury, or neoplasm.

� cognitive systems
� sensory systems
� motor systems

Functional competence involves three neural systems:

consciousness

Awareness of oneself and the environment

content of thought

All cognitive functions that employ awareness

Level of arousal

The state of awareness

cerebral cortex

The outer layer of the cerebrum, composed of six cell layers of deeply folded and ridged gray matter. where intellect and awareness are found.

cerebrum

The largest and most complex portion of the brain. It controls thought, learning, and many other complex activities.

cerebellum

The part of the brain below the back of the cerebrum. It regulates balance, posture, movement, and muscle coordination.

extracerebral

Outside cerebrum

supratentorial

Upper brain - cerebral cortex where intellect and awareness are found

infratentorial

Below tentorium

Damage to the lower brain stem

If you observe irregular and unpredictable patterns of breathing in a patient with a head injury, what might you assume?

Brain Death

A neurological manifestation where the cerebellum and brain stem are destroyed and can no longer maintain homeostasis and there is no potential for recovery.

Cerebral Death

Death of the cerebral hemispheres of the brain, exclusive of the brain stem and cerebellum. Internal homeostasis and respiratory functions may be maintained, but the individual is unable to respond behaviorally to the environment.

Vegetative state

A neurological manifestation where cerebral function is lost in this state, but sleep-wake cycles are present. The individual maintains blood pressure and breathing without support and brain stem reflexes are intact.

Locked-in syndrome

A neurological manifestation where both the content of thought and level of arousal are intact but the efferent pathways are disrupted. The individual cannot communicate but is fully conscious with intact cognitive function.

The reticular activating system
The function of higher brain centers in the cerebral cortex
Connections through the thalamus

In order to be fully conscious, what must be intact in the brain?

Epiloeptogenic focus

a group of neurons that evidence a paroxysmal depolarization shift and sudden changes in the usual membrane potential.

dysmnesia

An alteration in the content of thought. A disorder of the recent memory system defined as the loss of past memories coupled with an inability to form new memories despite intact attentional systems.

sensory inattentiveness

An alteration in the content of thought. A form of neglect syndrome where the sensory input from the dysfunctional side is ignored when timulated from both sides.

agnosia

A data processing deficit which presents a defect of pattern recognition, failure to recognize the form and nature of objects

dysphasia

A data processing deficit which presents impairment of comprehension or production of language. Comprehension or use of symbols either written or verbal language is disturbed or lost.

aphasia

A data processing deficit which presents loss of the comprehension or production of language

Acute confusional state

Result from cerebral dysfunction secondary to febrile illnesses, systemic diseases, anesthesia, postnatally, or with focal cerebral lesions

memory impairments
disorientation
compulsive behavior
frank delusions
distractibility
obsessions

What are some clinical manifestations of acute confusional state

Injury to nervous tissue
Action of toxin or chemical agents on neuronal cells
Disinhibition and over-activity of a previously depressed brain center

Acute confusional states may develop from

Dementia

Characterized by reduction in cognitive functions. Such as a decrease in orienting, recent memory, remote memory, language, executive attentional functions, and alterations in behavior. There is not a decrease in level of arousal.

Infarction

The obstruction of the blood supply to an organ or region of tissue, typically by a thrombus or embolus, causing local death of the tissue.

Hypermimesia

What term is used for pathologic laughter or crying.

Right Hemisphere

Pathologic laughter and the loss of emotional language is associated with which hemisphere of the brain?

Left Hemisphere

Pathologic crying is associated with which hemisphere of the brain?

Dystonia

The maintenance of abnormal posture through muscular contractions.

Hydrocephalus

What term is used to describe various conditions characterized by excess fluid in the cranial vault?

Ischemic Edema

A type of edema which follows a cerebral infarction. Soon after its onset brain cells begin to die and the released lysosomes increase the permeability of the blood brain barrier by lysing it.

Interstitial Edema

A type of edema caused by the movement of CSF from the ventricles into the extracellular spaces of brain tissues.

cognitive
sensory
motor

Functional adequacy is achieved through which major neural systems?

Reticular Activating System

The level of arousal is mediated by this system which extends from the medulla to the diencephalon. It provides arousal to the cerebral hemispheres.

Attentional
Memory
Language
Executive

Content of thought is mediated by which neural systems in the body?

Structural
Metabolic
Psychogenic

Arousal alterations which may cause Coma are classified into three major groups.

Chyne-Strokes Respiration

An abnormal rhythm of breathing which alternates between hyperventilation and apnea. Associated with bilateral dysfunction of deep cerebral or diencephalic structures.

Posthyperventilation apnea

A hemispheric breathing pattern where respirations stop after hyperventilation decreases the arterial cabon dioxide level below normal.

Mesencephalon Dysfunction

When a patient's roving eye movements cease and eyes become immobile and directed overhead. What type of brain damage does this imply?

Cortical Dysfunction or Dysfunction of Efferent pathways

A patient's eyes are fixed straight ahead, despite the movement of the head and conjugate, horizontal eye movements may be present. What type of brain damage does this imply?

Diffuse anoxic damage to the cortex

Ocular dipping occurs in a patient's eyes. That is downward movement followed by faster upward movement. What type of brain damage does this imply?

Vegetative State

A patient is in a wakeful unconscious state. His eyes sometimes open in response to stimulation. He also exhibits occasional responses to pain, such as posturing, tachycardia, and diaphoresis. The patient is considered to be in a....

Akinetic Mutism

A patient has a severe disturbance in behavioral drive. He opens his eyes and exhibits visual tracking, but there is no response to commands or spontaneous speech.

Locked-In Syndrom

Disruption of the efferent pathways by an injury to the ventral pons, leaving the content of thought and level of arousal intact.

95%

In a traumatic coma, if a patient's pupillary reflexes are absent for more than 6 hours, then what is the probability this patient will die?

91%

In a traumatic coma, if a patient's pupillary reflexes are absent for 24 hours, then what is the probability this patient will die?

Prodroma

Malaise, headache, or a sense of depression, that may occur hours to a few days before the onset of seizure.

Aura

A partial seizure experienced as a peculiar sensation preceding the onset of a generalized or complex partial seizure.

Dysmnesia

A loss of past memories (retrograde amnesia) combined with an inability to form new memories (anterograde amnesia), despite intact attentional networks.