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PHYSIOLOGY PRACTICAL - I: COMPLETE CASE HISTORY ANSWERS

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CASE 1 (Page 1) - HEMOPHILIA

Case Summary

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Symptom Analysis & Differential Diagnosis Reasoning

• Von Willebrand Disease - ruled out: vWD prolongs both bleeding time AND coagulation time (since vWF assists platelet adhesion). Here bleeding time is normal.
• Thrombocytopenia (ITP) - ruled out: platelet count is normal; ITP causes petechiae and prolonged bleeding time.
• Vitamin K deficiency - ruled out: this prolongs PT (extrinsic + final common pathway). Here PT is normal.
• Liver disease - ruled out: liver disease prolongs PT and multiple clotting factors; PT is normal here.
• DIC - ruled out: DIC consumes platelets; platelet count is normal.

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Answers

• Males are hemizygous (XY): if they inherit the defective X, they have no second X to compensate → disease manifests.
• Females are heterozygous carriers (X^H X): the normal X chromosome produces enough Factor VIII to prevent bleeding. They are carriers but clinically unaffected.
• For a female to be affected, she would need to be homozygous (X^H X^H), which is extremely rare (would require a carrier mother AND hemophiliac father).

• Each daughter has a 50% chance of being a carrier (X^H X) and 50% chance of being normal (X X).
• Therefore, the probability of the boy's sister being a carrier = 50% (1 in 2).

• Hemophilia A: Infusion of Factor VIII concentrate (recombinant or plasma-derived). Fresh frozen plasma (FFP) or cryoprecipitate (rich in Factor VIII, vWF, fibrinogen) can also be used.
• Hemophilia B: Infusion of Factor IX concentrate or FFP.
• Physiological basis: Replacing the deficient factor restores the intrinsic coagulation cascade, allowing thrombin generation, fibrin clot formation, and arrest of bleeding.
• Adjunct: Desmopressin (DDAVP) in mild Hemophilia A - stimulates release of stored vWF and Factor VIII from endothelium.

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CASE 2 (Page 2) - IRON DEFICIENCY ANEMIA

Case Summary

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Symptom Analysis & Differential Diagnosis Reasoning

• Hb 6 g% (normal ~12-14 in women) → severe anemia
• MCV 60 µ³ (normal 80-100) → microcytic
• MCHC 28 pg (normal 27-33 pg per cell, but MCHC normal 32-36 g/dL) → hypochromic
• Together: Microcytic hypochromic anemia
• Eosinophilia → parasitic infestation (hookworm = tissue invasion → eosinophilia)

• Thalassemia - also microcytic/hypochromic but: family history present, target cells on smear, normal/elevated ferritin, HbA2 elevated on electrophoresis. No hookworm.
• Anemia of chronic disease - normocytic usually; serum ferritin elevated, TIBC low. No hookworm.
• Sideroblastic anemia - ring sideroblasts on bone marrow; different cause.
• B12/Folate deficiency - megaloblastic (macrocytic, MCV >100), hypersegmented neutrophils. Not microcytic.

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Answers

• MCV 60 µ³ = microcytic (cells are smaller than normal)
• MCHC 28 pg = hypochromic (cells have less hemoglobin, appear pale)
• This is the most common type of anemia worldwide.

• Each hookworm attaches to the intestinal mucosa and ingests blood (0.2-0.5 mL/worm/day).
• Massive infestation leads to significant chronic iron loss.
• Iron is required for heme synthesis (protoporphyrin + Fe²⁺ + globin → hemoglobin). Deficiency → reduced Hb production → smaller, paler red cells.
• Additionally, hookworm larvae penetrate skin, migrate through lungs (causing eosinophilia), and settle in the gut, causing protein malnutrition as well.

1. Iron replacement: Oral ferrous sulfate (most common) - replenishes iron stores and allows resumption of hemoglobin synthesis. Parenteral iron (iron sucrose, ferric carboxymaltose) if oral not tolerated.
2. Anti-helminthic therapy: Albendazole or Mebendazole to eliminate hookworm - removes the cause of chronic blood loss.
3. Dietary advice: High-iron diet (leafy vegetables, meat, pulses), Vitamin C (enhances non-heme iron absorption by reducing Fe³⁺ → Fe²⁺), avoid tea/coffee with meals (tannins inhibit iron absorption).

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CASE 3 (Page 3) - MYASTHENIA GRAVIS

Case Summary

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Symptom Analysis & Differential Diagnosis Reasoning

• Lambert-Eaton Syndrome - paraneoplastic (usually lung cancer); weakness improves with repetition (opposite pattern); affects proximal limbs not ocular/bulbar muscles primarily. Anti-VGCC antibodies (pre-synaptic).
• Multiple Sclerosis - CNS demyelination; neurological examination would be abnormal; no fatigability pattern.
• Botulism - blocks ACh release (pre-synaptic); descending paralysis; no response to neostigmine (because the problem is no ACh being released, not reduced receptors).
• ALS (Motor Neuron Disease) - upper AND lower motor neuron signs; progressive; no response to neostigmine.
• Muscular Dystrophy - primary muscle disease; not fatigable; no response to neostigmine.

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Answers

• In ~85% of cases: Anti-AChR antibodies (IgG) bind to and destroy or block nAChR → fewer functional receptors → insufficient end-plate potential → muscle cannot reach action potential threshold.
• In ~5%: Anti-MuSK antibodies (muscle-specific kinase - essential for clustering AChR).
• Associated with thymic abnormalities: thymoma (~15%) or thymic hyperplasia (~65%).
• The antibodies are formed by autoreactive B cells; T-cell mediated mechanisms also contribute.
• Because acetylcholine is released normally but fewer receptors are available, with sustained activity, the EPP falls below threshold → fatigue.

• Normally, after ACh is released into the synapse, acetylcholinesterase (AChE) rapidly breaks it down into choline + acetate.
• In MG, since fewer receptors are available, even normal ACh release is insufficient.
• Neostigmine inhibits AChE → ACh is NOT broken down → accumulates in the synapse → remains available longer → has more chances to bind the remaining functional receptors → End-plate potential reaches threshold → muscle contracts.
• This does NOT cure MG but compensates for the receptor deficiency by increasing available ACh.
• Pyridostigmine (longer-acting, oral) is the mainstay symptomatic treatment.

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CASE 4 (Pages 4-5) - Clinical Charts (Not case histories)

• a. Name the clinical condition: Based on characteristic lines - likely Cheyne-Stokes respiration or pulsus paradoxus - requires viewing the actual chart.
• The question structure (characteristic lines, causes, 2 lab tests) suggests it may be a Spirometry chart for obstructive/restrictive lung disease.

• a. Waves A, B, C, D = Alpha (α), Beta (β), Theta (θ), Delta (δ) waves
• b. Alpha recorded best: posterior occipital region at rest with eyes closed. Beta: frontal lobes. Theta: temporal/frontal in drowsiness. Delta: deep sleep, recorded over all scalp.
• c. Features: Alpha 8-13 Hz; Beta 13-30 Hz; Theta 4-7 Hz; Delta 0.5-4 Hz.
• d. Clinical uses: Epilepsy diagnosis, sleep disorders, coma grading, brain death, encephalopathy, monitoring anesthesia depth.

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CASE 8 (Page 8) - HYPERTHYROIDISM (GRAVES' DISEASE)

Case Summary

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Symptom Analysis & Differential Diagnosis Reasoning

• Anxiety disorder/panic disorder - tachycardia and nervousness overlap, but no weight loss, no raised BMR, no eye signs, TSH normal.
• Phaeochromocytoma - also sweating, tachycardia, hypertension but episodic; BMR mildly elevated; urine catecholamines elevated; TSH normal.
• Diabetes - weight loss + increased appetite but no tachycardia, no tremors, no eye signs; blood glucose elevated.

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Answers

• BMR +40%: Significantly elevated (normal is ±15%). This indicates a hypermetabolic state. Thyroid hormones increase the rate of oxidative phosphorylation in all cells by increasing expression of mitochondrial enzymes and Na⁺/K⁺-ATPase. Every 1% rise in BMR correlates with approximately 1% increase in oxygen consumption. +40% is markedly hypermetabolic, consistent with severe hyperthyroidism.
• Basal pulse rate 120/min: Significantly elevated (normal 60-100/min). Persistent resting tachycardia reflects increased cardiac sympathetic tone due to thyroid hormone-induced upregulation of β-adrenergic receptors. This explains palpitations and dyspnea.

• Young woman (most common in females 20-40 years)
• Diffuse features (not nodular)
• Eyelid retraction (sympathetic manifestation)
• Classic constellation of symptoms

1. Serum TSH (Thyroid Stimulating Hormone): Will be extremely LOW (suppressed) in hyperthyroidism due to negative feedback on anterior pituitary. This is the most sensitive screening test.
2. Serum Free T3 and Free T4 levels: Will be markedly elevated - directly confirms hyperthyroidism.
3. Thyroid Antibodies: Anti-TSH Receptor antibodies (TRAb/TSHR-Ab) - positive in Graves' disease (stimulating antibodies activate TSH receptors). Also anti-TPO and anti-thyroglobulin antibodies.
4. Radioactive Iodine Uptake (RAIU) scan: Diffusely elevated uptake in Graves'; focal uptake in toxic nodule.
5. Thyroid ultrasound: Diffuse enlargement with increased vascularity in Graves' disease.

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CASE 9 (Page 9) - DIABETES MELLITUS TYPE 2

Case Summary

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Symptom Analysis & Differential Diagnosis Reasoning

• Diabetes Insipidus - polyuria + polydipsia but NO glycosuria, NO elevated blood glucose. Urine is very dilute (low osmolarity). Due to ADH deficiency (central DI) or resistance (nephrogenic DI).
• Type 1 DM - would have ketone bodies in urine (absolute insulin deficiency → unrestrained lipolysis → ketogenesis). Middle age, gradual onset, and absence of ketones suggests Type 2.
• LADA (Latent Autoimmune Diabetes of Adults) - possible but less likely without autoantibody testing.

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Answers

• Classic triad: polyuria, polydipsia, polyphagia
• Weight loss and poor wound healing
• Glucosuria (sugar in urine)
• Fasting blood glucose 160 mg/dl (>126 mg/dl = DM)
• Absence of ketone bodies - key finding suggesting Type 2, not Type 1

• Hyperglycemia impairs neutrophil and macrophage function (chemotaxis, phagocytosis)
• Glycosylation of proteins (advanced glycation end-products) damages blood vessel walls → microangiopathy → reduced local blood flow to wounds
• Reduced collagen synthesis and cross-linking
• Peripheral neuropathy (in chronic DM) reduces sensation → injuries go unnoticed

• In Type 1 DM, there is absolute insulin deficiency. Without any insulin, adipose tissue undergoes unrestrained lipolysis → large amounts of free fatty acids flood the liver → beta-oxidation overwhelms the TCA cycle → acetyl-CoA is diverted to ketone body synthesis (acetoacetate, beta-hydroxybutyrate, acetone) → ketonuria and diabetic ketoacidosis (DKA).
• In Type 2 DM, there is relative insulin deficiency or insulin resistance. Even small amounts of residual insulin are sufficient to suppress lipolysis in adipose tissue → free fatty acid flux to liver is NOT excessive → ketone body synthesis is not significantly elevated → urine is ketone-free.
• This is also why Type 2 DM rarely develops DKA spontaneously (though it can in extreme stress).

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CASE 10 (Page 10) - PEPTIC ULCER (DUODENAL)

Case Summary

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Symptom Analysis & Differential Diagnosis Reasoning

• Normal basal secretion: 0-5 mEq/hr (this patient = 6 mEq/L - elevated)
• Augmented histamine test (maximal acid output): normal = 20-30 mEq/hr (this patient = 35 mEq/L - significantly elevated)

• Gastric ulcer - pain worsened or not relieved by food; often in older patients; weight loss from food aversion.
• Gastric carcinoma - progressive, not relieved by food, weight loss, older age, endoscopy would show mass.
• GERD - burning retrosternal, worse after meals and lying down; not relieved by food per se.
• Pancreatitis - epigastric pain radiating to back, not relieved by food; elevated amylase/lipase.

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Answers

• Pain in the upper abdomen (epigastric), relieved by food, is classic for duodenal ulcer
• Elevated basal and stimulated HCl secretion supports hyperacidity
• Age and presentation (business executive - stress is a contributing factor) fits

• Normal Maximal Acid Output (MAO) in the augmented histamine test = 20-30 mEq/hour (some sources state up to 25 mEq/hr)
• The test involves subcutaneous injection of histamine (0.04 mg/kg body weight) after antihistamine pre-medication (to block systemic effects but not gastric H2 receptors)
• This patient's 35 mEq/L is above normal, indicating hyperchlorhydria (excess acid secretion), characteristic of duodenal ulcer

1. Pentagastrin (synthetic gastrin analogue) - now the preferred agent as it is safer than histamine (no systemic side effects). Dose: 6 µg/kg subcutaneously.
2. Insulin (Hollander insulin test) - causes hypoglycemia → stimulates vagus nerve → stimulates gastric HCl secretion. Used to test completeness of vagotomy.
3. Caffeine - stimulates gastric acid secretion via CNS and directly.

• In a duodenal ulcer, the ulcer is in the duodenum, just distal to the pylorus. Gastric acid pours into the duodenum and irritates the exposed mucosal surface (where the ulcer is) → pain.
• When food is ingested: Food enters the stomach → acts as a physical and chemical buffer for HCl in the stomach. Proteins in food have strong acid-buffering capacity (amino acid side chains act as buffers).
• Additionally, food in the stomach stimulates pyloric closure and duodenal hormones (secretin, CCK) which temporarily reduce gastric emptying and reduce acid delivery to the duodenum.
• Result: Less free acid reaching the duodenal ulcer → temporary relief of pain.
• Note: Pain returns 2-3 hours after eating once food is digested and buffering capacity is exhausted (this is why duodenal ulcer causes "hunger pain" or "pain at night" - called Moynihan's rhythmicity).

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CASE 11 (Page 11) - OBSTRUCTIVE JAUNDICE

Case Summary

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Symptom Analysis & Differential Diagnosis Reasoning

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Answers

• Direct bilirubin elevation (Van den Bergh direct+): Conjugated bilirubin dams back into blood (it is water-soluble → enters urine)
• Absent stercobilinogen in stool: No bile reaching intestine → no urobilinogen/stercobilinogen produced → clay-colored stool
• Bilirubin in urine (bilirubinuria): Water-soluble conjugated bilirubin filtered by kidneys
• Pruritus: Bile salts deposited in skin stimulate cutaneous nerve endings
• Bradycardia: Bile acids accumulated in blood have a direct negative chronotropic effect on the SA node
• Prolonged coagulation: Bile is essential for absorption of fat-soluble vitamins (A, D, E, K). Obstruction → no bile in gut → Vitamin K malabsorption → reduced synthesis of clotting factors II, VII, IX, X → prolonged PT/coagulation time
• Bulky, foul-smelling stool: Fat malabsorption (steatorrhea) - bile acids needed for fat micelle formation; without bile, fat passes undigested → bulky, greasy, foul stools
• Low serum albumin: Prolonged obstruction → liver damage → reduced albumin synthesis
• Elevated liver enzymes: Backpressure of bile damages hepatocytes → enzyme release

• Pale/clay color: Normally, conjugated bilirubin enters the duodenum via bile duct → intestinal bacteria convert it to urobilinogen → further reduced to stercobilinogen → oxidized to stercobilin → gives stool its normal brown color. In obstruction, NO bile reaches the intestine → NO stercobilinogen → NO stercobilin → stool is pale/clay-colored.
• Bulky: Bile salts are essential for emulsification and absorption of dietary fats. Without bile, fats pass undigested → steatorrhea (fat-laden bulky stools).
• Foul smelling: Undigested and putrefied fat in the intestine undergoes bacterial action → fermentation of unabsorbed organic compounds → offensive odor.

• The Van den Bergh test detects bilirubin in serum using diazo reagent (Ehrlich's diazo reagent).
• Conjugated (direct) bilirubin is water-soluble and reacts immediately and directly with the diazo reagent → DIRECT positive.
• Unconjugated (indirect) bilirubin is lipid-soluble and bound to albumin; it requires alcohol to first dissolve it before reacting → gives only indirect positive.
• In obstructive jaundice: Bile duct obstruction → conjugated bilirubin (already processed by liver) cannot be excreted → dams back into hepatic sinusoids → regurgitates into blood → elevated serum conjugated bilirubin → Van den Bergh DIRECT positive.
• Serum bilirubin is 6 mg/dl (normal <1 mg/dl), predominantly direct (conjugated).

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CASE 12 (Page 12) - CIRCULATORY SHOCK (HYPOVOLEMIC)

Case Summary

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Symptom Analysis & Differential Diagnosis Reasoning

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Answers

• Vasoconstriction of skin and splanchnic vessels (α1 receptors) → skin becomes pale and cold
• Activation of sweat glands (cholinergic sympathetic fibers) → clammy skin

1. Arrest the bleeding (if external): Direct pressure, tourniquet if limb hemorrhage.
2. Airway, Breathing, Circulation (ABC): Secure airway, administer 100% O₂.
3. IV access: Two large-bore (14-16G) peripheral IV cannulas immediately.
4. IV fluid resuscitation:
   • Initial bolus: Crystalloids - Normal saline or Ringer's Lactate - 1-2 liters rapidly
   • For hemorrhagic shock: Blood transfusion - Packed RBCs (type-matched or O-negative emergency)
   • Colloids (albumin, hetastarch) for plasma volume expansion
5. Position: Trendelenburg position (legs elevated 15-20°) to improve venous return.
6. Monitor: Heart rate, BP, urine output (Foley catheter), CVP, oxygen saturation continuously.
7. Vasopressors (only after adequate volume replacement): Noradrenaline (norepinephrine) or dopamine if hypotension persists.
8. Treat underlying cause: Emergency surgery if internal hemorrhage.

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CASE 13 (Page 13) - RIGHT-SIDED HEART FAILURE (COR PULMONALE / RHF)

Case Summary

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Symptom Analysis & Differential Diagnosis Reasoning

• Left heart failure: primarily causes pulmonary congestion → dyspnea, orthopnea, pulmonary edema, pink frothy sputum, cardiomegaly (left side), S3 gallop. JVP not elevated (right side is not backing up).
• This patient has no pulmonary symptoms but has systemic venous congestion → Right heart failure.

• Cirrhosis: ascites prominent, spider angiomas, caput medusae, splenomegaly, low albumin, elevated liver enzymes. JVP is NOT raised. X-ray normal.
• This patient: JVP raised, RV hypertrophy on X-ray → cardiac cause confirmed.

• Nephrotic: massive proteinuria (>3.5g/day), hypoalbuminemia, hypercholesterolemia. JVP normal. No hepatomegaly. No RV hypertrophy.
• This patient has only trace albumin in urine (secondary to congestion) and RV hypertrophy.

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Answers

• Dependent pitting edema (worse in evening - gravitational)
• Raised JVP (systemic venous hypertension)
• Hepatomegaly (congestive hepatopathy - "nutmeg liver")
• Oliguria + nocturia
• X-ray: RV hypertrophy
• ECG: Elevated P wave (P pulmonale)

• Right heart failure → right ventricle cannot pump all blood forward → blood accumulates in the right atrium and systemic veins
• Systemic venous pressure rises → increased hydrostatic pressure in peripheral capillaries (especially in legs/ankles due to gravity)
• Starling forces: Normally, hydrostatic pressure pushes fluid out of capillaries, and oncotic pressure pulls it in. When hydrostatic pressure rises chronically, net filtration exceeds lymphatic drainage → fluid accumulates in interstitial spaces → pitting edema.
• It worsens toward evening because the patient has been upright all day (gravity accumulates fluid in dependent areas). It improves in the morning after lying down overnight (fluid redistributes).
• Simultaneously, secondary hyperaldosteronism (RAAS activation due to low cardiac output) causes Na⁺ and water retention → further worsens edema.
• Low albumin (from hepatic congestion) reduces oncotic pressure → less fluid pull-back → exacerbates edema.

• The liver is drained by the hepatic veins which drain into the inferior vena cava (IVC) → right atrium.
• In RHF, right atrial pressure rises → IVC pressure rises → hepatic venous pressure rises → blood cannot drain from the liver sinusoids → sinusoidal congestion.
• Liver becomes engorged with blood → enlarged, soft, and tender (the stretching of Glisson's capsule causes tenderness).
• Chronic congestion leads to hepatocyte hypoxia (especially centrilobular - zone 3 furthest from portal blood supply) → nutmeg liver pattern on histology → eventually cardiac cirrhosis if untreated.

• In Right Heart Failure (especially Cor Pulmonale), there is pulmonary hypertension → right ventricle works against high resistance → right ventricle hypertrophies → pressure is transmitted back to the right atrium → right atrial hypertrophy/enlargement → the right atrium must generate a stronger depolarization wave to empty against elevated RV pressure.
• This produces P pulmonale: Tall, peaked P wave (>2.5 mm in lead II) in ECG.
• Normally the P wave is <2.5 mm tall. Right atrial enlargement produces taller, narrower (peaked) P waves, especially visible in leads II, III, and aVF.
• This is distinct from P mitrale (bifid, broad P wave in left atrial enlargement, seen in mitral stenosis).

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CASE 14 (Page 14) - ANGINA PECTORIS (STABLE)

Case Summary

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Symptom Analysis & Differential Diagnosis Reasoning

• Location: Retrosternal (behind sternum) - the heart is in the mediastinum
• Character: Constricting/squeezing - from ischemic myocardium
• Radiation: Along the inner (ulnar) border of the left arm - via T1-T4 dermatomes (same spinal segments as cardiac sympathetic afferents) - referred pain
• Trigger: Exertion - increased myocardial O₂ demand exceeds supply through narrowed coronary arteries
• Relief: Rest (reduces demand), or nitrates (vasodilate coronary vessels)

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Answers

• Retrosternal constricting chest pain
• Radiation to left arm (ulnar border) - referred pain via T1-T4 dermatomes
• Proportional to exertion (demand ischemia)
• (Implied) relief with rest

• Angina occurs during exertion, not at rest. The coronary arteries are narrowed (stenosed) by atherosclerotic plaque, but not completely occluded. At rest, blood flow through the narrowed vessel is still adequate to meet the low myocardial oxygen demand → no ischemia → no ECG changes.
• ECG changes in angina occur only during ischemia (exercise/stress): During ischemia, ventricular repolarization is altered → ST depression (or elevation in variant/Prinzmetal angina), T-wave inversion appear. These changes are transient and revert with cessation of ischemia.
• In MI (complete occlusion, permanent ischemia), ECG changes are permanent: ST elevation (STEMI), Q waves, T-wave inversion.
• Chest X-ray is normal: Stable angina does not cause heart enlargement (unlike chronic heart failure). The coronary vessels are not visible on plain chest X-ray. There is no pulmonary congestion at rest.
• To "unmask" the ECG changes in angina: Stress ECG (Exercise Tolerance Test / TMT - Treadmill Test) is performed. When the patient exercises to 85% of maximum heart rate, demand exceeds supply → ischemia → >1 mm ST depression in ECG = positive test = confirms coronary artery disease.

• Sublingual nitroglycerine (GTN): To be taken immediately when pain occurs - dilates coronary arteries and systemic veins (reduces preload and afterload → reduces myocardial oxygen demand). Carry at all times.

1. Stop smoking - smoking accelerates atherosclerosis and causes coronary vasospasm.
2. Dietary changes: Low saturated fat, low cholesterol diet to slow atherosclerosis progression.
3. Regular moderate exercise: Paradoxically, regular graded exercise training increases collateral coronary circulation over time and improves exercise tolerance.
4. Weight reduction if overweight - reduces cardiac work.
5. Control blood pressure - hypertension accelerates coronary disease.
6. Stress management: Emotional stress can trigger angina (catecholamine surge increases HR and BP → demand ↑).

• Beta-blockers (atenolol, metoprolol): Reduce heart rate and contractility → reduce myocardial O₂ demand → prevent angina.
• Long-acting nitrates (isosorbide mononitrate): Prophylaxis.
• Calcium channel blockers (amlodipine): Coronary vasodilation.
• Aspirin (75-150 mg/day): Antiplatelet - prevents thrombus formation on plaques.
• Statins (atorvastatin): Reduce LDL cholesterol and stabilize atherosclerotic plaques.

• Treadmill test / Stress ECG: To assess severity and document ischemia.
• Coronary angiography: To visualize the extent and location of stenosis - guides decision for angioplasty (PTCA) or bypass surgery (CABG).

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Sources: Guyton and Hall Textbook of Medical Physiology | Ganong's Review of Medical Physiology | Robbins & Kumar Basic Pathology | Costanzo Physiology 7th Edition | Medical Physiology (Boron & Boulpaep) | Basic Medical Biochemistry (Harvey)

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CASE 4 - CLINICAL CHART: CUSHING'S SYNDROME

What the Chart Shows

• Round, puffy, flushed face (moon face) - pointer line at the face
• Central/truncal obesity (protruberant abdomen) - pointer line at the abdomen
• Abdominal striae (purple stretch marks on the abdomen)
• Thin limbs (wasted arms and legs compared to the trunk)
• Skin changes/bruising on the lower leg - pointer line at the shin
• The overall body shape: fat trunk with slim extremities

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a. Name the Clinical Condition

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b. Characteristic Features Indicated by the Pointer Lines

• Hypertension (cortisol has mineralocorticoid-like effects → Na⁺ retention)
• Hypertrichosis/hirsutism in women (adrenal androgens co-secreted)
• Acne (androgenic effect)
• Osteoporosis (cortisol inhibits osteoblasts, reduces Ca²⁺ absorption)
• Poor wound healing
• Glucose intolerance / secondary diabetes (cortisol is a counter-regulatory hormone - promotes gluconeogenesis, inhibits peripheral glucose uptake)
• Psychological disturbances (depression, anxiety, euphoria)
• Amenorrhea in women

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c. Causes of Cushing's Syndrome

ACTH-Dependent (more common, ~80%):

1. Cushing's Disease (most common endogenous cause, ~70% of all cases):
   • Pituitary adenoma (usually a microadenoma) secreting excess ACTH
   • ACTH stimulates bilateral adrenal cortex → bilateral adrenal hyperplasia → excess cortisol
   • Named "Cushing's Disease" specifically when it is pituitary in origin
2. Ectopic ACTH Syndrome (~10%):
   • Non-pituitary tumors secrete ACTH ectopically
   • Most common: Small cell carcinoma of the lung (oat cell carcinoma)
   • Others: Carcinoid tumors of bronchus, pancreas, thymus; medullary thyroid carcinoma; phaeochromocytoma
   • Tends to be more severe and rapid in onset

ACTH-Independent (~20%):

1. Adrenal Adenoma (unilateral benign tumor of adrenal cortex secreting cortisol independently)
2. Adrenal Carcinoma (rare, aggressive; may produce very high cortisol levels)
3. Adrenal Hyperplasia (ACTH-independent macronodular or micronodular)

Exogenous (most common cause overall):

1. Iatrogenic Cushing's Syndrome - Chronic therapeutic use of corticosteroids (prednisolone, dexamethasone, hydrocortisone) for conditions like asthma, rheumatoid arthritis, organ transplant. This is the single most common cause globally.

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d. Two Laboratory Tests to Confirm Diagnosis

Step 1 - Confirm excess cortisol (Screening/Confirmatory Tests):

• The patient is given 1 mg dexamethasone at 11 PM. At 8 AM next morning, serum cortisol is measured.
• Normal: Cortisol is suppressed to <50 nmol/L (1.8 µg/dl) - negative feedback intact.
• In Cushing's Syndrome: Cortisol is NOT suppressed (remains elevated >50 nmol/L) - the negative feedback axis is overridden.
• This is the most widely used screening test.

• Collect all urine over 24 hours and measure free (unbound) cortisol excreted.
• Normal: <100 µg/24 hours (280 nmol/24 hours).
• In Cushing's Syndrome: Markedly elevated (>3-4x normal = highly specific).
• Measures integrated cortisol production over the whole day - avoids the normal diurnal variation confound.
• Two elevated results on separate days confirm the diagnosis.

Step 2 - Find the source (once hypercortisolism is confirmed):

• ACTH elevated or normal: ACTH-dependent cause (pituitary adenoma or ectopic tumor) → do MRI pituitary and/or high-dose dexamethasone test.
• ACTH very low/undetectable: ACTH-independent cause (adrenal adenoma/carcinoma) → do CT/MRI adrenal glands.

• Normally cortisol is lowest at midnight. In Cushing's, the normal diurnal rhythm is lost.
• Elevated midnight salivary cortisol (>145 ng/dl) = highly sensitive and specific screening test. Convenient and non-invasive.

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Summary Table

Sources: Schwartz's Principles of Surgery 11e | Kaplan & Sadock's Comprehensive Textbook of Psychiatry | Swanson's Family Medicine Review - via Medical Textbook Library

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CASE 5 - CLINICAL CHART: EEG (ELECTROENCEPHALOGRAM) WAVES

The Chart

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a. Name the Waves Depicted in the Graph A, B, C, and D

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b. Location Where Each Wave is Recorded Best

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c. Features of the Waves

Alpha (α) Waves - 8 to 13 Hz

• Frequency: 8-13 cycles/second (Hz)
• Amplitude (voltage): ~50 µV
• Character: Rhythmical, synchronous, regular sinusoidal pattern
• State: Awake, resting, eyes closed, relaxed mental state
• Location: Occipital (best), parietal, frontal
• Significance: Hallmark of the alert-relaxed waking brain. Disappear during:
  • Deep sleep
  • Opening of eyes (visual input breaks synchrony)
  • Mental concentration (alpha blocking)
• Abnormal: Absent or slowed alpha indicates diffuse cerebral dysfunction

Beta (β) Waves - 14 to 80 Hz

• Frequency: 14-80 Hz (commonly 18-30 Hz)
• Amplitude: Low, <20 µV (desynchronized)
• Character: Irregular, fast, low voltage, asynchronous
• State: Active thinking, mental concentration, eyes open, anxiety, REM sleep
• Location: Frontal and parietal lobes (specific cortical activation areas)
• Significance: Reflects active cortical processing. "Desynchronized" EEG = the cortex is busy and neurons are firing independently rather than in synchrony
• Abnormal: Excessive beta seen with benzodiazepines, barbiturates

Theta (θ) Waves - 4 to 7 Hz

• Frequency: 4-7 Hz
• Amplitude: Medium, ~20-100 µV
• Character: Irregular, somewhat slow waves
• State:
  • Normal in children (up to adolescence) during wakefulness
  • Stage 1 sleep in adults (transition to sleep)
  • Emotional stress, frustration, disappointment in adults
  • Drowsiness
• Location: Temporal and parietal regions (children); frontal-temporal in adults
• Significance: Normal in children; if seen in awake adults = can indicate pathology (focal lesions, encephalopathy)

Delta (δ) Waves - 0.5 to 4 Hz

• Frequency: 0.5-4 Hz (very slow)
• Amplitude: Highest of all - 100-200 µV (large, rolling waves)
• Character: Large, slow, high-amplitude waves - the slowest EEG waves
• State:
  • Deep sleep (Stage 3 = 20-50% delta; Stage 4 = >50% delta) = "Slow Wave Sleep" or "NREM deep sleep"
  • Normal in infants and young children when awake
• Location: Diffuse over all scalp regions during sleep
• Significance:
  • Normal during deep sleep - restorative sleep; growth hormone secreted during delta sleep
  • PATHOLOGICAL in awake adults - indicates severe diffuse brain damage, metabolic encephalopathy, space-occupying lesions, brain tumor, or focal brain injury

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d. Clinical Conditions Where EEG is a Vital Tool

1. Epilepsy (Seizure Disorders) - MOST IMPORTANT use

• EEG detects characteristic patterns:
  • Grand mal (Tonic-clonic) seizures: High-voltage spikes followed by slow waves (spike-and-wave complexes)
  • Absence seizures (Petit mal): Classic 3 Hz spike-and-wave pattern (pathognomonic)
  • Partial seizures: Focal spike discharges over the affected lobe
  • Infantile spasms (West syndrome): Hypsarrhythmia pattern
• EEG helps classify seizure type, locate the epileptic focus, and monitor treatment

2. Brain Death Certification

• Electrocerebral silence (isoelectric/flat EEG) = absence of all brain electrical activity
• EEG is one of the confirmatory tests for brain death when clinical criteria are met
• Two flat EEGs taken 24 hours apart = confirmatory evidence of brain death (in many protocols)

3. Sleep Disorders

• Polysomnography (sleep study) uses EEG to identify:
  • Sleep stages (NREM stages 1-4, REM)
  • Narcolepsy: Sleep-onset REM episodes
  • Insomnia: Disrupted sleep architecture
  • Sleep apnea: Fragmented sleep with arousals
  • Parasomnias (sleep walking, night terrors): Occur during specific NREM stages

4. Coma Evaluation

• EEG characterizes the depth and type of coma
• Differentiates between:
  • Metabolic coma (diffuse slowing - theta/delta)
  • Structural coma (focal changes)
  • Psychogenic unresponsiveness (normal EEG)
  • Status epilepticus (continuous seizure activity - treated as an emergency)

5. Encephalitis and Encephalopathy

• Herpes simplex encephalitis: Periodic lateralized epileptiform discharges (PLEDs) over temporal lobes
• Hepatic encephalopathy: Triphasic waves
• Creutzfeldt-Jakob disease (CJD / prion disease): Periodic sharp wave complexes (PSWCs) - 1-2 Hz

6. Monitoring Depth of Anesthesia

• During surgery, EEG (or processed EEG like Bispectral Index / BIS monitor) monitors the depth of anesthesia to prevent awareness during surgery and avoid overdose

7. Neonatal/Pediatric Neurology

• Diagnosis of neonatal seizures (clinically subtle in neonates)
• Assessment of brain maturity in premature infants
• Detection of hypoxic-ischemic encephalopathy (HIE) after birth asphyxia

8. Dementia Workup

• Alzheimer's disease: Diffuse slowing in late stages
• CJD: Periodic complexes (highly specific)
• Helps differentiate dementia subtypes

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Summary Table

Sources: Guyton and Hall Textbook of Medical Physiology, Fig. 60.3 | Costanzo Physiology 7th Edition | Kaplan & Sadock's Comprehensive Textbook of Psychiatry