patho exam 3
Unit 5 Chapter 44: Brain Injuries and Cerebrovascular Disease
Types of Brain Injuries - Primary Injury: Occurs immediately at the onset of the initial insult. - Secondary Injury: Refers to damage or physiological changes that occur subsequent to the primary injury. - Ischemia and Hypoxia: Result in reduced ATP production and mitochondrial failure. - Blood Pressure Influences: Hypotension predisposes the brain to ischemia, while Hypertension (HTN) leads to vascular damage and brain edema. - Carbon Dioxide () Levels: Increased results in vasodilation, while decreased results in vasoconstriction.
Ischemia and Hypoxia - Ischemia: Delivery of oxygenated blood is too low to meet the metabolic demands of brain tissue. This can function as both a primary and secondary injury mechanism. - Hypoxia: A deficiency of oxygen reaching the tissues, often the result of ischemia or hypoxemia (low blood oxygenation).
Intracranial Pressure (ICP) - Normal Range: . - Monro-Kellie Hypothesis: States that the cranium is a fixed-volume compartment containing brain tissue, blood, and CSF; an increase in one component must be compensated by a decrease in one or both of the other two. - Etiology of Elevation: - Vasogenic Edema: Increased capillary pressure; severe HTN may occur surrounding tumors. - Cytotoxic Edema: Ischemic tissue swells due to cellular energy failure. - Obstruction/Excessive Production: Related to Cerebrospinal Fluid (CSF). - Complications: Brain herniation and brain compression. - Clinical Manifestations (Early): Headache, nausea/vomiting (), restlessness, drowsiness, and blurry vision (papilledema). - Clinical Manifestations (Late): Decreased Level of Consciousness (LOC), sluggish pupil response, dilated pupils, and altered respiratory patterns. - Cushing’s Reflex: A late sign of high ICP involving widened pulse pressure, bradycardia, and irregular respirations.
Level of Consciousness (LOC) - Change in LOC is the earliest sign of increased ICP. - Manifestations include being drowsy, restless, or confused.
Glasgow Coma Scale (GCS) - A standardized tool for assessing LOC in Traumatic Brain Injury (TBI). - Evaluates three categories: Eye opening, verbal utterances, and motor reactions. - Scores: Best score is ; worst score is .
Cranial Nerve (CN) Reflexes - CN 3 (Oculomotor): Controls motor response to light; dysfunction leads to a dilated pupil. - Oculovestibular Reflex: Used primarily to identify brain death. - CN 8 (Vestibulocochlear): Transmits auditory info and inner ear vestibular info, interacting with CN 3 and 4 to control eye movements during head rotation. - Dolls Eye Test: If the brainstem is intact, eyes turn in the opposite direction of head rotation. If absent, eyes stay midline and do not turn. - Cold Calorics: Ice cold water is irrigated into a comatose patient’s ear. If brain function is present, the eyes will follow the irrigated ear; if absent, eyes remain forward. - Corneal Reflex: Testing the blink response (CN 5) with a Q-tip to the cornea. An absent response indicates impaired brain function.
Traumatic Brain Injury (TBI) Severity and Classification - Severity Scores (GCS): - Mild: - Moderate: - Severe: or below. - Primary Injury Types: - Focal (Coup): Localized to the site of impact. - Polar (Coup Contracoup): Acceleration-deceleration injury affecting opposite poles of the brain. - Diffuse: Widespread injury involving stretching and shearing of axonal white matter (e.g., Shaken Baby Syndrome).
Basilar Skull Fracture - Evaluation is mandatory for head injury patients with clear fluid draining from the ears or nose. - CSF Identification: High glucose content; separates into layers forming a "halo" sign on dressings. - Physical Signs: Black eyes (raccoon sign) and bruising under the ear (Battle sign). - Risk: High risk of Central Nervous System (CNS) infection.
Intracranial Hematomas - General Patho: Hemorrhage increases ICP. Diagnosis via CT, MRI, or CT Angiogram. - Subdural Hematoma: - Collection of blood between the dura and arachnoid membrane; involves shearing of bridging veins. - Acute: Symptoms appear within hours. - Subacute: ICP increases days later. - Chronic: Prone to rebleeding. - Epidural Hematoma: - Typically involves a fractured temporal bone disrupting the middle meningeal artery. - Blood collects between the dura and the skull; involves arterial injury with rapid symptom onset. - Lucid Interval: Patient loses consciousness upon impact, awakens and is Alert and Oriented (), then rapidly declines in LOC.
Ischemic Stroke - Patho: Sudden occlusion of a cerebral artery. - Clinical Manifestations: Contralateral hemiplegia, hemisensory loss, and visual field blindness. - Risk Factors: Age , being male, African American, smoking, HTN, Atrial Fibrillation (Afib), previous stroke, Diabetes Mellitus (DM), hyperlipidemia, and family history.
Transient Ischemic Attack (TIA) - Patho: Transient symptoms that resolve completely within hours without evidence of a permanent infarct. - Significance: Serves as a major risk factor for subsequent strokes.
Hemorrhagic Stroke - Patho: Hemorrhage within brain parenchyma (basal ganglia or thalamus), usually secondary to severe chronic HTN. - Clinical Manifestations: Signs of increased ICP and brain herniation.
Stroke Sequelae - Motor/Sensory: Deficits occur contralateral to the side of the stroke. - Right-sided Stroke: Blindness in the left visual field; disturbances in visual-spatial relations. - Language Deficits (Aphasia): Usually involves the dominant (Left) hemisphere. - Broca Aphasia: Verbal motor/expressive deficit; poor articulation. - Wernicke Aphasia: Secondary/acoustic/receptive deficit; impaired comprehension (speech is fluent but nonsensical).
Cerebral Aneurysm and Arteriovenous Malformation (AVM) - Aneurysm: Congenital defect in the medial layer of the arterial wall leading to dilation/ballooning. Common in the Circle of Willis at bifurcations. Rupture causes subarachnoid hemorrhage (severe headache, photophobia, stiff neck). - AVM: Capillary system fails to develop, shunting blood directly into the venous system under high pressure, leading to rupture, seizures, and neurological dysfunction.
Unit 5 Chapter 45: Neurological Disorders
Seizures - Patho: Excess cortical electrical discharges; neurons are hyperactive/hypersensitive (epileptogenic focus). - Generalized Seizures (Whole Brain): - Absence: Staring spells in children. - Myoclonic: Sudden jerks. - Atonic: Drop attacks. - Tonic-Clonic: "Hulk phase" followed by jerking. - Status Epilepticus: Continuous seizures without recovery; risks include oxygen lack, dysrhythmias, and lactic acid build-up. - Partial Seizures (One Hemisphere): - Simple: No change in LOC. - Complex: Starts with consciousness, then leads to altered LOC.
Parkinson’s Disease - Patho: Degeneration of dopaminergic neurons in the substantia nigra; presence of Lewy body plaques. - Clinical Manifestations: Pill rolling, shuffled gait, drooling, akinesia, bradykinesia, infrequent blinking, tremors, muscle rigidity.
Bell’s Palsy and Trigeminal Neuralgia - Bell’s Palsy: Idiopathic neuropathy of CN 7; nerve is demyelinated leading to unilateral facial paralysis and decreased lacrimation. Rapid onset within hours. - Trigeminal Neuralgia: Pain in CN 5 caused by nerve demyelination or compressed vessels. Presents as sharp electrical pains with periods of remission.
Unit 6 Chapter 46: Hearing, Balance, and Vision
Hearing Impairment - Conductive Hearing Loss: Sounds cannot reach the cochlea due to dysfunction in the external or middle ear (cerumen impaction, foreign bodies). - Otosclerosis: Resorption of bone followed by spongy bone formation in the middle ear. Family history; common in middle-aged Caucasian women. Tinnitus is common. - Sensorineural Hearing Loss: Disturbance in inner ear (cochlea) or CN 8; often irreversible. - Ototoxicity: Caused by medications like Aminoglycoside antibiotics, Salicylates, Quinine, Furosemide, and Cytotoxic antineoplastic drugs.
Trauma and Age-Related Hearing - Noise Trauma: Repeated exposure above . Includes Temporary Threshold Shift (sensitivity returns) and Permanent Threshold Shift (irreversible). - Presbycusis: Hearing loss in elderly (). Includes Sensory (hair cell atrophy), Neural (neuron loss), Metabolic (cochlea wall atrophy), and Mechanical types.
Meniere’s Disease - Patho: Accumulation of endolymph in the labyrinth; distention and rupture of the scala media. - Clinical Manifestations: Triad of fluctuating hearing loss, tinnitus, and Vertigo (classic sign). Nystagmus (CN 6 involvement) occurs during acute attacks.
Vision Disorders - Myopia: Elongated eye; nearsighted; focus is in front of the retina. - Hyperopia: Shortening of eye; farsighted; focus is behind the retina. - Presbyopia: Loss of accommodation; inability to see close objects in middle age. - Astigmatism: Irregular curvature of the lens; distorted image. - Strabismus: Ocular misalignment (cross-eyedness). Risk factors include low birth weight and cigarette smoking during pregnancy. - Amblyopia: Altered visual development despite normal pathways; most common cause of vision loss. - Cataracts: Opacity (cloudy lens) causing gradual, painless visual loss.
Retinal and Glaucoma Disorders - Retinal Detachment: Sudden appearance of floaters and flashes; "curtain being pulled over eye." - Diabetic Retinopathy: Tissue