Chapter 16: Disorders of Brain Function
Copyright © 2019 Wolters Kluwer · All Rights Reserved
1
Common Pathways of Brain Damage
The effects of ischemia
Excitatory amino acid injury
Cerebral edema
Injury due to increased intracranial pressure (ICP)
Copyright © 2019 Wolters Kluwer · All Rights Reserved
2
Conditions Causing Injury to the Brain
Trauma
Tumors
Stroke
Metabolic derangements
Degenerative disorders
Copyright © 2019 Wolters Kluwer · All Rights Reserved
3
Manifestations of Global Brain Injury
Alterations in sensory and motor function
Changes in the level of consciousness
Rostral-to-caudal stepwise progression
As the diencephalon, midbrain, pons, and medulla are affected, additional respiratory, pupillary, and eye movement reflexes and motor signs become evident.
Copyright © 2019 Wolters Kluwer · All Rights Reserved
4
Classifications of Skull Fractures
Simple or Linear
A break in the continuity of bone
Comminuted
A splintered or multiple fracture line.
Depressed
When bone fragments are embedded into the brain tissue, the fracture is said to be depressed.
Basilar
A fracture of the bones that form the base of the skull
Copyright © 2019 Wolters Kluwer · All Rights Reserved
5
Levels of Consciousness
Confusion
Delirium
Obtundation
Stupor
Coma
Copyright © 2019 Wolters Kluwer · All Rights Reserved
6
Injury from Excitatory Amino Acids
Definition
Injury to neurons caused by overstimulation of receptors for specific amino acids that act as excitatory neurotransmitters
Causes
Stroke
Hypoglycemic injury
Trauma to chronic degenerative disorders such as Huntington disease and Alzheimer dementia
Copyright © 2019 Wolters Kluwer · All Rights Reserved
7
Signs of Diminution in Level of Consciousness
Earliest Signs
Inattention, mild confusion, disorientation, and blunted responsiveness
With further deterioration
The person becomes markedly inattentive and variably lethargic or agitated.
The person may progress to become obtunded and may respond only to vigorous or noxious stimuli.
Copyright © 2019 Wolters Kluwer · All Rights Reserved
8
Medical Documentation of Brain Death
Cause and irreversibility of the condition
Absence of brain stem reflexes and motor responses to pain
Absence of respiration with a PCO2 of 60 mm Hg or more
The justification for use of confirmatory tests and their results
Copyright © 2019 Wolters Kluwer · All Rights Reserved
9
Criteria for Diagnosis of Vegetative State #1
Absence of awareness of self and environment
An inability to interact with others
Absence of sustained or reproducible voluntary behavioral responses
Lack of language comprehension
Hypothalamic and brain stem function to maintain life
Copyright © 2019 Wolters Kluwer · All Rights Reserved
10
Criteria for Diagnosis of Vegetative State #2
Bowel and bladder incontinence.
Variably preserved cranial nerve and spinal cord reflexes.
The condition has continued for at least 1 month.
Copyright © 2019 Wolters Kluwer · All Rights Reserved
11
Hypoxia and Ischemia
Hypoxia
A deprivation of oxygen with maintained blood flow
Ischemia
Reduced or interrupted blood flow
Focal cerebral ischemia—stroke
Global cerebral ischemia—MI
Copyright © 2019 Wolters Kluwer · All Rights Reserved
12
Question #1
Which of the following is not a common cause of neural injury?
Recreational drug use
Ischemia
Excitatory amino acids
Cerebral edema
Increased intracranial pressure (ICP)
Copyright © 2019 Wolters Kluwer · All Rights Reserved
13
Answer #1
A. Recreational drug use
Rationale: Recreational drug use can cause damage, but it is not a common cause.
Copyright © 2019 Wolters Kluwer · All Rights Reserved
Intracranial Pressure
Increased ICP is a common pathway for brain injury.
Can obstruct cerebral blood flow, destroy brain cells, displace brain tissue, and damage delicate brain structures
Cranial cavity
10% blood, 80% brain tissue, 10% CSF
Normal ICP 0 to 15 mm Hg
Monro-Kellie hypothesis of normalization of ICP
Copyright © 2019 Wolters Kluwer · All Rights Reserved
15
Brain Herniation #1
Cingulate
Involves cerebral artery
Clinical sign: leg weakness
Central Transtentorial
Involves the reticular activating system and corticospinal tract
Clinical signs: altered level of consciousness, decorticate posturing, rostral–caudal deterioration
Copyright © 2019 Wolters Kluwer · All Rights Reserved
16
Brain Herniation #2
Uncal
Involves the cerebral peduncle, oculomotor nerve, posterior cerebral artery, cerebellar tonsil, respiratory center
Clinical signs: hemiparesis, pupil dilation, visual field loss, respiratory arrest
Copyright © 2019 Wolters Kluwer · All Rights Reserved
17
Hydrocephalus
Definition
An abnormal increase in CSF volume in any part or all of the ventricular system
Enlargement of the CSF compartment occurs.
Types
Communicating
Decreased absorption of CSF
Noncommunicating
Overproduction of CSF
Copyright © 2019 Wolters Kluwer · All Rights Reserved
18
Cerebral Edema
Vasogenic Edema
Occurs with conditions that impair the function of the blood–brain barrier and that allow transfer of water and protein from the vascular into the interstitial space
Cytotoxic Edema
Involves an increase in intracellular fluid
Interstitial Cerebral Edema
Edema of the central white matter as in hydrocephalus affecting the brain
Copyright © 2019 Wolters Kluwer · All Rights Reserved
19
Types of Brain Injuries
Primary or Direct Injuries
Damage is caused by an impact.
Include diffuse axonal injury and the focal lesions of laceration, contusion, and hemorrhage
Secondary Injuries
Damage results from the subsequent brain swelling, infection, and cerebral hypoxia.
Often diffuse or multifocal, including concussion, infection, and hypoxic brain injury
Copyright © 2019 Wolters Kluwer · All Rights Reserved
20
Types of Hematomas
Brain injuries can be categorized as traumatic (i.e., epidural hematoma, subdural hematoma, concussion, contusion, or diffuse axonal injury) or nontraumatic brain injury (i.e., stroke, infection, tumor, or seizure).
Epidural hematomas, subdural hematoma, and traumatic intracerebral hematomas
Copyright © 2019 Wolters Kluwer · All Rights Reserved
Focal and Diffuse Brain Injuries
Primary brain injuries include focal (e.g., contusion, laceration, hemorrhage) and diffuse (e.g., concussion, diffuse axonal injury) injuries.
Secondary brain injuries are often diffuse or multifocal, including edema, infection, and hypoxic brain damage.
Copyright © 2019 Wolters Kluwer · All Rights Reserved
Coup–Contrecoup
The brain floats freely in the CSF; blunt force to the head accelerates the brain within the skull, and then the brain decelerates abruptly on hitting the inner skull surfaces.
Coup—direct contusion of the brain at the site of external force
Contrecoup—rebound injury on the opposite side of the brain
Copyright © 2019 Wolters Kluwer · All Rights Reserved
23
Question #2
Rotational acceleration of the head may result in which type of injury?
Coup
Contrecoup
Copyright © 2019 Wolters Kluwer · All Rights Reserved
24
Answer #2
B. Contrecoup
Rationale: Contrecoup is the rebound injury on the opposite side of the brain.
Copyright © 2019 Wolters Kluwer · All Rights Reserved
25
Postconcussion Syndrome
Concussion refers to “an immediate and transient loss of consciousness accompanied by a brief period of amnesia after a blow to the head.”
Recovery usually takes place in 24 hours.
Mild symptoms may persist for months:
Headache
Irritability
Insomnia
Poor concentration and memory
Copyright © 2019 Wolters Kluwer · All Rights Reserved
26
Types of Hematomas #1
Epidural Hematoma
Usually caused by head injury in which the skull is fractured
Develops between the inner table of the bones of the skull and the dura
Subdural Hematoma
Usually is the result of a tear in the small bridging veins that connect veins on the surface of the cortex to dural sinuses
Develops in the area between the dura and the arachnoid (subdural space)
Copyright © 2019 Wolters Kluwer · All Rights Reserved
27
Types of Hematomas #2
Traumatic Intracerebral Hematomas
May be single or multiple
Occur in any lobe of the brain but are most common in the frontal or temporal lobes
Copyright © 2019 Wolters Kluwer · All Rights Reserved
28
Structures Supplying Blood Flow to the Brain
Two internal carotid arteries anteriorly
Ophthalmic, posterior communicating, anterior choroidal, anterior cerebral, and middle cerebral
Vertebral arteries posteriorly
Internal carotid and vertebral arteries communicate at the base of the brain through the circle of Willis.
Copyright © 2019 Wolters Kluwer · All Rights Reserved
29
Cerebral Blood Flow
Autoregulation
Sympathetic stimulation
Metabolic factors
Carbon dioxide
Hydrogen ion
Oxygen concentration
Copyright © 2019 Wolters Kluwer · All Rights Reserved
Risk Factors and Deficits of Stroke
Age, sex, race
Family history
Hypertension
Smoking
Diabetes mellitus
Asymptomatic carotid stenosis
Sickle cell disease
Hyperlipidemia
Atrial fibrillation
Stroke-Related Deficits
Motor deficits
Dysarthria and aphasia
Cognitive and other deficits
Copyright © 2019 Wolters Kluwer · All Rights Reserved
Two Main Types of Strokes (Brain Attack)
Ischemic Strokes
Caused by an interruption of blood flow in a cerebral vessel and are the most common type of strokes, accounting for 70% to 80% of all strokes.
Hemorrhagic Strokes
Caused by bleeding into brain tissue usually from a blood vessel rupture caused by hypertension, aneurysms, arteriovenous malformations, head injury, or blood dyscrasias
Copyright © 2019 Wolters Kluwer · All Rights Reserved
32
Warning Signs and Danger Zones
Ischemic penumbra in evolving stroke
Transient ischemic stroke
Brain angina
Watershed zone
Copyright © 2019 Wolters Kluwer · All Rights Reserved
33
Signs and Symptoms of Cerebral Aneurysms
Most small aneurysms are asymptomatic.
Large aneurysms may cause chronic headache, neurologic deficits, or both.
Other manifestations include signs of meningeal irritation, cranial nerve deficits, stroke syndrome, cerebral edema and increased ICP, and pituitary dysfunction.
Hypertension and cardiac dysrhythmias result from massive release of catecholamines triggered by the subarachnoid hemorrhage.
Copyright © 2019 Wolters Kluwer · All Rights Reserved
34
Aneurysmal Subarachnoid Hemorrhage
Bleeding into the subarachnoid space
Causes
Congenital defect
Acute increases in ICP
Cigarette smoking
Hypertension
Excessive alcohol intake
Copyright © 2019 Wolters Kluwer · All Rights Reserved
35
Hemodynamic Effects of Arteriovenous Malformations
First, blood is shunted from the high-pressure arterial system to the low-pressure venous system without the buffering advantage of the capillary network.
The draining venous channels are exposed to high levels of pressure, predisposing them to rupture and hemorrhage.
Second, the elevated arterial and venous pressures divert blood away from the surrounding tissue, impairing tissue perfusion.
Copyright © 2019 Wolters Kluwer · All Rights Reserved
36
Question #3
Which type of stroke is the result of a ruptured blood vessel?
Ischemic
TIA
Arteriovenous malformation
Hemorrhagic
Copyright © 2019 Wolters Kluwer · All Rights Reserved
37
Answer #3
D. Hemorrhagic
Rationale: Hemorrhagic strokes are caused by the rupturing of a major vessel in the brain.
Copyright © 2019 Wolters Kluwer · All Rights Reserved
38
Typical Problems Arising from Stroke
Motor deficits are most common, followed by deficits of language, sensation, and cognition.
Copyright © 2019 Wolters Kluwer · All Rights Reserved
Classifications of Infections of the CNS Type of Invading Organism
By structure
Meninges: meningitis
Brain parenchyma: encephalitis
Spinal cord, myelitis
Brain and spinal cord: encephalomyelitis
By type of invading organism
Bacterial, viral, or other
Copyright © 2019 Wolters Kluwer · All Rights Reserved
Meningitis
Inflammation of the pia mater, the arachnoid, and the CSF-filled subarachnoid space
Fever and chills; headache; stiff neck; back, abdominal, and extremity pains; and nausea and vomiting
Acute lymphocytic meningitis
Acute purulent meningitis
Bacterial meningitis
Pneumococcus
Meningococcus
Viral meningitis
Copyright © 2019 Wolters Kluwer · All Rights Reserved
41
Encephalitis
Infection of the parenchyma of the brain or spinal cord
Local necrotizing hemorrhage
Progressive degeneration of nerve cell bodies
Prominent edema
Transmission
Ingestion
Mosquito
Rabid animal
Types
Viral
Herpes simplex virus, West Nile virus
Bacteria
Fungi
Copyright © 2019 Wolters Kluwer · All Rights Reserved
42
Classification of Brain Tumors
Primary intracranial tumors of neuroepithelial tissue
Neurons, neuroglia
Primary intracranial tumors that originate in the skull cavity but are not derived from the brain tissue itself
Meninges, pituitary gland, pineal gland, primary CNS lymphoma
Metastatic tumors
Benign versus malignant
Copyright © 2019 Wolters Kluwer · All Rights Reserved
43
Types and Symptoms of Brain Tumors
Ependymomas
Meningiomas
Primary CNS lymphomas
Increased ICP
Focal disturbances in brain function
Edema
Disturbances in blood flow
Tumor infiltration
Brain compression
Copyright © 2019 Wolters Kluwer · All Rights Reserved
44
Treatment and Evaluation Methods for Brain Tumors
Surgery
Irradiation
Chemotherapy
MRI
CT scans
Electroencephalogram
Visual field and funduscopic examination
Include physical and neurologic examinations
Copyright © 2019 Wolters Kluwer · All Rights Reserved
45
Epilepsy
Syndromes of associated seizure types
EEG patterns
Exam findings
Hereditary patterns
Precipitating factors
Copyright © 2019 Wolters Kluwer · All Rights Reserved
46
Seizures and Convulsions
Seizure
The abnormal behavior caused by an electrical discharge from neurons in the cerebral cortex
A discrete clinical event with associated signs and symptoms that vary according to the site of neuronal discharge in the brain
Manifestations generally include sensory, motor, autonomic, or psychic phenomenon
Convulsion
Specific seizure type of a motor seizure involving the entire body
Copyright © 2019 Wolters Kluwer · All Rights Reserved
47
Causes of Epilepsy #1
Seizures may be caused by alterations in cell membrane permeability or distribution of ions across the neuronal cell membranes.
Another cause may be decreased inhibition of cortical or thalamic neuronal activity or structural changes that alter the excitability of neurons.
Neurotransmitter imbalances such as an acetylcholine excess or γ-aminobutyric acid (GABA, an inhibitory neurotransmitter) deficiency have been proposed as causes.
Copyright © 2019 Wolters Kluwer · All Rights Reserved
Causes of Epilepsy #2
Certain epilepsy syndromes have been linked to specific genetic mutations causing ion channel defects.
Copyright © 2019 Wolters Kluwer · All Rights Reserved
Types of Seizures #1
Partial Seizures
Simple partial seizures
Complex partial seizures
Partial seizures evolving to secondarily generalized seizures
Unclassified Seizures
Inadequate or incomplete data
Copyright © 2019 Wolters Kluwer · All Rights Reserved
50
Types of Seizures #2
Generalized Seizures
Absence seizures
Atonic seizures
Myoclonic seizures
Tonic seizures
Tonic–clonic seizures
Copyright © 2019 Wolters Kluwer · All Rights Reserved
51
Status Epilepticus
Continual seizures
Do not stop spontaneously
Many types
If untreated or not stopped can lead to death due to respiratory failure
Copyright © 2019 Wolters Kluwer · All Rights Reserved
52

Get help from top-rated tutors in any subject.
Efficiently complete your homework and academic assignments by getting help from the experts at homeworkarchive.com