Disorders of Brain Function

Conditions Causing Injury to the Brain
Trauma
Tumors
Stroke
Metabolic derangements
Degenerative disorders
Common Pathways of Brain Damage
The effects of ischemia
Excitatory amino acid injury
Cerebral edema
Injury due to increased intracranial pressure (ICP)
Hypoxia and Ischemia
Hypoxia
A deprivation of oxygen with maintained blood flow
Ischemia
A situation of greatly reduced or interrupted blood flow
Interferes with delivery of oxygen and glucose as well as the removal of metabolic
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’s disease and Alzheimer’s dementia
Brain Herniation
Cingulate
Involves cerebral artery
Clinical sign: leg weakness
Central Transtentorial
Involves reticular activating system and corticospinal tract
Clinical signs: altered level of consciousness, decorticate posturing, rostral-caudal deterioration
Brain Herniation (cont.)
Uncal
Involves cerebral peduncle, oculomotor nerve, posterior cerebral artery, cerebellar tonsil, respiratory center
Clinical signs: hemiparesis, pupil dilation, visual field loss, respiratory arrest
Cerebral Edema
Vasogenic edema
Occurs with conditions that impair the function of the blood-brain barrier and allow transfer of water and protein from the vascular into the interstitial space
Cytotoxic edema
Involves an increase in intracellular fluid
Hydrocephalus
Definition
An abnormal increase in CSF volume in any part or all of the ventricular system
Enlargement of the CSF compartment occurs
Causes
Decreased absorption or overproduction of CSF
Types
Non-communicating and communicating

Head Injury
Definition
All structural damage to the head (brain injury)
Main causes
Road accidents, falls, and assaults
Types
Can involve both closed injuries and open wounds
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
Types of Brain Injuries
Primary or direct injuries
Damage is caused by impact
Include diffuse axonal injury and the focal lesions of laceration, contusion, and hemorrhage
Secondary injuries
Damage results from the subsequent brain swelling, infection, cerebral hypoxia
Often diffuse or multi-focal, including concussion, infection, and hypoxic brain injury
Types of Hematomas
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)
Types of Hematomas (cont.)
Traumatic Intracerebral Hematoma
May be single or multiple
Occur in any lobe of the brain but are most common in the frontal or temporal lobes
Manifestations of Global Brain Injury
Alterations in sensory and motor function
Changes in the level of consciousness
Levels of Consciousness
Confusion
Delirium
Obtundation
Stupor
Coma
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
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
Criteria for Diagnosis of Vegetative State
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

Criteria for Diagnosis of Vegetative State (cont.)
Bowel and bladder incontinence
Variably preserved cranial nerve and spinal cord reflexes
Condition has continued for at least 1 month
Structures Supplying Blood Flow to the Brain
Two internal carotid arteries anteriorly
Vertebral arteries posteriorly
Metabolic Factors Affecting Cerebral Blood Flow
Carbon dioxide
Hydrogen ion
Oxygen concentration
Two Main Types of Strokes
Ischemic strokes
Caused by an interruption of blood flow in a cerebral vessel and are the most common type of stroke, 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
Risk Factors for 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
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

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
Classifications of Infections of the CNS
By structure
Meninges: meningitis
Brain parenchyma: encephalitis
Spinal cord, myelitis
Brain and spinal cord: encephalomyelitis
By type of invading organism
Bacterial, viral, or other
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
Types of Brain Tumors
Ependymomas
Meningiomas
Primary CNS Lymphomas
Treatment Methods for Brain Tumors
Surgery
Irradiation
Chemotherapy
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 which 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
Types of Seizures
Partial Seizures
Simple partial seizures
Complex partial seizures
Partial seizures evolving to secondarily generalized seizures
Unclassified seizures
Inadequate or incomplete data
Types of Seizures (cont.)
Generalized seizures
Absence seizures
Atonic seizures
Myclonic seizures
Tonic seizures
Tonic-clonic seizures