Unit 5, 6, & 7 Neurology, Sensory, and Musculoskeletal Pathophysiology Study Guide

Comprehensive vocabulary terms and definitions covering Neurology, Brain Pathophysiology, Sensory Systems (Eyes/Ears), and Musculoskeletal disorders based on the lecture notes.

Ischemia

A state where oxygenated blood levels are lower than needed to meet the metabolic demands of brain tissue, eventually leading to cell death.

Hypoxia

A deficiency of oxygen at the cellular level resulting from lower blood flow or low blood oxygen.

Glutamate

The main CNS neurotransmitter that acts as an excitotoxin; during ischemia, its increased release overstimulates neurons, leading to calcium overload and cytotoxic edema.

Reperfusion

The process of restoring blood flow to the brain which can paradoxically cause additional cell death by generating free radicals and attracting immune cells.

Autoregulation

The brain's ability to maintain constant blood flow, normally functioning within a mean arterial blood pressure range of $60-140\,mmHg$.

Intracranial Pressure (ICP)

The pressure inside the skull, normally ranging from $0-15\,mmHg$, with values $>22\,mmHg$ for $>5\,\text{minutes}$ indicating brain impairment.

Monroe-Kellie Doctrine

The principle stating that the intracranial compartment is a fixed volume composed of the brain, cerebrospinal fluid, and blood; an increase in one component must be compensated by a decrease in another.

Vasogenic Edema (Interstitial Edema)

Swelling that occurs when fluid, electrolytes, and proteins are forced into intercellular spaces due to vessel damage or high pressure; often seen in strokes, HTN, and tumors.

Cytotoxic Edema (Intracellular Edema)

Generalized brain edema resulting from cellular energy failure and ATP depletion, causing $Na^+$ to accumulate in the cell and attract water.

Cushing Triad

A critical late sign of increased ICP characterized by a wide pulse pressure (hypertension), bradycardia (low heart rate), and fluctuating respirations.

Glasgow Coma Scale (GCS)

A standard tool for assessing level of consciousness based on Eye Opening (max $4$), Verbal Response (max $5$), and Motor Response (max $6$).

Doll's Eyes Test (Oculovestibular reflex)

A test where a normal response is eyes moving in the opposite direction of head movement; an absent response (eyes stay midline) suggests brainstem dysfunction.

Cold Calorics Test

A test involving cold water in the ear where a normal response is eyes deviating toward the cold water side; lack of movement is an absent response.

Polar Injury (Coup-countercoup)

A traumatic brain injury occurring at both the site of impact and the opposite side of the brain due to forward-backward movement.

Epidural Hematoma

A rapid arterial bleed located between the inner skull and the dura mater, often characterized by a patient feeling okay initially before deteriorating quickly.

Subdural Hematoma

A slower venous bleed located between the dura and outer arachnoid membrane, often caused by stretching and shearing of bridging veins.

Subarachnoid Hemorrhage

Bleeding between the outer arachnoid membrane and pia mater, commonly caused by trauma, aneurysms, or AVMs; blood may be found in the CSF via spinal tap.

Penumbra

The viable area of brain tissue surrounding an area of necrosis (infarction) that is supported by collateral circulation.

Lacunar Infarcts

Small occlusions of arterioles, often due to HTN or diabetes, that frequently affect motor and sensory functions.

Arteriovenous Malformation (AVM)

A congenital malformation where arterial blood is shunted directly into the venous system without a capillary bed, leading to high venous pressure and risk of rupture.

Status Epilepticus

A medical emergency consisting of repeated seizures without recovery time in between, which can lead to hypoxia and lactic acidosis.

Parkinson Disease

A neurodegenerative disorder caused by the loss of dopaminergic neurons in the substantia nigra, characterized by Lewy bodies and symptoms like bradykinesia and pill-rolling tremors.

Bell's Palsy

Idiopathic inflammation of Cranial Nerve VII (Facial nerve) resulting in unilateral facial weakness and decreased eye blink.

Trigeminal Neuralgia

Chronic compression of the trigeminal nerve causing demyelination and sudden, excruciating, shock-like facial pain.

Vertigo

A sensation of motion or aggravation of motion that is a cardinal symptom of vestibular system disorders.

Conductive Hearing Loss

Hearing loss occurring when sound cannot travel through the outer or middle ear due to issues like cerumen impaction or ossicle stiffness.

Sensorineural Hearing Loss

Hearing loss resulting from dysfunction of hair cells in the cochlea or neural pathways, often caused by loud noise exposure ($>85\,\text{decibels}$) or ototoxic drugs.

Otosclerosis

A condition where healthy bone is replaced by weak spongy bone in the middle ear ossicles, most frequently the stapes, leading to conductive hearing loss.

Presbycusis

Gradual, bilateral sensorineural hearing loss common in older adults, characterized by difficulty hearing high-pitched sounds.

Meniere Disease

A chronic inner ear disease involving increased endolymphatic fluid, characterized by the triad of vertigo, tinnitus, and unilateral sensorineural hearing loss.

Otitis Media

Inflammation of the middle ear often resulting from eustachian tube dysfunction; chronic cases are defined as lasting longer than $12\,\text{weeks}$.

Myopia

Nearsightedness caused by an elongated eye where images fall in front of the retina; corrected with concave lenses.

Hyperopia

Farsightedness caused by a shorter eye where images fall behind the retina; corrected with convex lenses.

Cataracts

A condition where the lens clouds and loses opacity due to oxidative stress, leading to blurred vision and altered color perception.

Retinal Detachment

The separation of the retina from the retinal pigment epithelium; symptoms include sudden onset of floating spots and curtain-like vision loss.

Diabetic Retinopathy

Damage to retinal vessels caused by hyperglycemia, classified as nonproliferative (microaneurysms) or proliferative (neovascularization).

Macular Degeneration

Age-related degeneration of the retinal epithelium causing central vision loss; straight lines appearing wavy is a hallmark of the 'wet' type.

Glaucoma

Increased intraocular pressure leading to optic nerve damage; open-angle involves progressive peripheral vision loss, while closed-angle is a sudden surgical emergency.

Compartment Syndrome

A dangerous complication where swelling within a restrictive fascia increases pressure, leading to tissue ischemia and necrosis; characterized by pain, pallor, and paresthesias.

Comminuted Fracture

A fracture pattern consisting of more than one fracture line and more than two bone fragments.

Greenstick Fracture

An incomplete break where the bone cracks but does not go all the way across, most commonly seen in children.

Osteonecrosis (Avascular Necrosis)

Bone death resulting from impaired circulation, often related to a fracture that occludes blood vessels.

Osteomyelitis

Infection of the bone, most commonly caused by Staphylococcus aureus reaching the bone via the bloodstream (hematogenous), adjacent tissue, or direct introduction.

Fat Embolism Syndrome

A complication of pelvic or long bone fractures where fat particles lodge in the lungs, occurring $24-72\,\text{hours}$ after injury.

Scoliosis

A lateral curvature of the spine of $\ge 10^\circ$, classified as structural (vertebral rotation present) or nonstructural (no rotation, curve resolves with bending).

Osteoporosis

A metabolic bone disorder where bone resorption by osteoclasts exceeds bone building by osteoblasts, leading to porous bones prone to fracture.

Osteomalacia

A condition in adults characterized by soft, weak bones due to vitamin D deficiency; known as Rickets in children.

Paget Disease

A disorder of excessive bone resorption followed by disorganized, fragile bone formation, often affecting the skull, spine, and pelvis.

Multiple Myeloma

The most common primary malignant bone tumor; it is a slow-growing marrow malignancy involving plasma cells.

Osteosarcoma

The second most common malignant bone tumor, characterized by rapid bone formation by tumor cells and frequent metastasis to the lungs.

Duchenne Muscular Dystrophy

A severe, X-linked genetic disorder where muscles lack the protein dystrophin, leading to muscle fiber necrosis and calf hypertrophy.

Osteoarthritis

A local, non-inflammatory degenerative joint disorder associated with aging and 'wear and tear', characterized by loss of articular cartilage and formation of bone spurs (osteophytes).

Heberden's Nodes

Bony enlargements at the proximal finger joints associated with osteoarthritis.

Gout

A disorder of uric acid metabolism resulting in the deposition of urate crystals in joints; acute attacks are often triggered by high-purine foods like meats and alcohol.