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acute brain disorder (Central Nervous System Infection (Factors…
acute brain disorder
Central Nervous System Infection
Infections of the CNS include meningitis, encephalitis,abscesses
Factors contributing to infections include
Debilitation
poor nutrition
immunocompromised status
radiation therapy
steroid therapy
contact with vectors
Meningitis and cerebral abscess →bacterial
The combination of headache, fever, stiff neck, and signs of cerebral dysfunction (confusion, delirium),seizures.
Cranial nerve involvement is also common and is most often seen as ocular palsies, facial weakness and/or deafness, and vertigo.
Encephalitis → viral
can be caused by a variety of agents including viruses, bacteria, fungi, and parasites
Herpesviruses are by far the most common viral cause
herpes simplex virus type 1 (HSV-1)
Pathogenesis
HSV-1 encephalitis occurs in healthy and immunocompromised adults
HSV-2 can be transmitted to neonates during vaginal delivery
Brain Abscess
Pyogenic (pus-producing) pathogens reach the brain
penetrating wounds
bloodborne dissemination from a distant infected site (lung)
direct extension or retrograde thrombophlebitis of an infected neighboring structure(sinusitis)
Most brain abscesses are bacterial
streptococci, staphylococci, and anaerobes
Traumatic Brain Injury(TBI)
Traumatic brain injury (TBI) refers to injuries of brain tissues sustained as a consequence of trauma
Early rescue from the trauma scene and immediate emergency management are important in the effort to reduce morbidity and mortality after TBI
Primary injury: Local injury to the brain can result in specific neurologic symptoms, depending on the site.
motor cortex →contralateral weakness of the face and arm
frontal lobe → apraxia ,impulsive behavior, and poor judgment.
localized hemorrhages or significant edema → increased ICP, brain shifting, herniation.
Secondary Injury
Often the damage done by secondary mechanisms > primary trauma
hemorrhage can lead to hypovolemia and hypotension
Brain swelling from both cytotoxic and vasogenic edema may increase
Ruptured vessels may rebleed or spasm, and CSF drainage can become clogged
Structure and Function of the Nervous System
The nervous system is a complex network of neurons
The nervous system is composed
Neurons →which generate and transmit nerve impulses
by the neurotransmitters they secrete
glial cells → which provide supportive functions to neurons but do not transmit action potentials.
There are approximately 10 glial cells per neuron and about 100 billion neurons in the CNS
Astrocytes
contact the brain capillaries and help maintain the integrity of the blood brain barrier
Microglia
from the monocyte-macrophage cell type
provide phagocytic functions within the CNS
Ependymal cells
producing CSF and maintaining the CSF brain barrier
Neuronal Communication
Neurons communicate primarily through the release of neurotransmitters into the synapses adjacent to target neurons.
Postsynaptic neurons have receptors for these neurotransmitters and respond by changing the flow of ions through channels in the cell membrane.
Increased Intracranial Pressure
Increased Brain Tissue Volume
Obstructive hydrocephalus
Nonobstructive hydrocephalus
Pseudotumor cerebri
Increased Cerebrospinal Fluid Volume
Increased right atrial pressure
High arterial Paco2
Dural sinus thrombosis
Acidosis
Increased Blood Volume
Tumor
Infection
Hemorrhage
Cytotoxic edema
Vasogenic edema
Ischemia and necrosis
Cerebrovascular Disease and Stroke
Ischemic Stroke
Thrombotic strokes
Emboli
TIAs are important warning signs of thrombotic disease and carry a significant risk for subsequent stroke
treatment
ischemic strokes of embolic origin → Usually the source is the heart control of dysrhythmias, impleanticoagulation therapy,and antiplatelet drugs such as aspirin.
prevention for thrombotic stroke → lifestyle modifications
TIAs are important warning signs of thrombotic disease and carry a significant risk for subsequent stroke
Place stents, in the area of plaque removal may be helpful in preventing reocclusion
Hemorrhagic Stroke
hemorrhage within the brain parenchyma
oftenlong-standing hypertension
Cause subarachnoid hemorrhage
Most intracerebral hemorrhagic strokes occur in the basal ganglia or thalamus
If the hemorrhage is large, it may significantly increase ICP, which can lead to herniation and death.
Stroke Sequelae
Sensory Deficits
A lack of sensory information from the paralyzed side contributes to the phenomenon of neglect
Neglect is associated with a high risk for falls and other injuries.
Motor
decrease in or absence of muscle tone in the affected extremities
motor paralysis is contralateral to the side of the brain
Structural Organization of Brain
primary injury
Head trauma
Brain tissue necrosis
Cessation of blood flow - Stroke
Cytotoxic edema
Irreversibly damaged
secondary injury
preventing secondary damage have remained elusive
mortality and morbidity ↑
progress over days or weeks
Mechanism of Brain Injury
Ischemia and Hypoxia
Cellular Energy Failure
Neurons dependent on glucose for production of ATP
about 5 to 10 minutes of complete occlusion
Glycolysis → producing pyruvate → lactate → releases H+ → cellular acidosis
Reperfusion Injury
face new dangers with the return of blood flow
Oxygen → oxygen free radical formation
flow of blood → invade inflammatory cells
capillary endothelial cells are injured
interleukin-1 (IL-1), interleukin-6 (IL-6), tumor necrosis factor (TNF)
increase neutrophils⇒contribute to brain inflammation
Excitatory Amino Acids
Abnormal Autoregulation
blood flow through brain tissue is controlled primarily by autoregulation
Cerebral perfusion pressure (CPP)
Blood flow is maintained rate
(MAP) from about 50 to 150 mm Hg
Increased Intracranial Pressure
Malformation
the two most common causes of subarachnoid hemorrhage
arteriovenous malformations (AVMs)
AVMs are the second most common cause of spontaneous subarachnoid hemorrhage
Exposure of the high-capacitance venous system to the high pressure
treatment
gamma knife or stereotactic radiosurgery
surgically removed
Cerebral aneurysms
An aneurysm is a lesion of an artery that results in dilation and ballooning of a segment of the vessel.
Saccular aneurysms (berry aneurysms) are round
Warning leaks may occur before an aneurysm ruptures
often produce severe headache
nausea/vomiting
photophobia (visual sensitivity to light)
the worst headache I have ever had.
stiff neck