Master Anatomy
for PMDC NLE Step 1

What the PMDC NLE Step 1 Tests in Anatomy

The PMDC NLE Step 1 Anatomy section tests applied anatomical knowledge in clinical contexts. Candidates must identify structures on cross-sectional imaging (CT, MRI), explain nerve injuries (e.g., radial nerve palsy causing wrist drop), and predict deficits from vascular occlusions (e.g., middle cerebral artery stroke). Questions frequently involve surface anatomy for procedures (e.g., lumbar puncture at L3-L4 interspace), embryological derivatives (e.g., Meckel's diverticulum from vitelline duct), and anatomical basis of common fractures (e.g., Colles' fracture with dinner fork deformity). You must apply knowledge to clinical scenarios: referred pain patterns (e.g., shoulder tip pain in splenic rupture), muscle actions and innervations (e.g., foot drop in common peroneal nerve injury), and anatomical spaces for infection spread (e.g., retropharyngeal abscess causing airway compromise).

High-Yield Concepts

• Brachial Plexus Injuries: Erb-Duchenne palsy (C5-C6) presents with waiter's tip deformity: loss of shoulder abduction (deltoid, C5), elbow flexion (biceps, C5-C6), and forearm supination. Klumpke's palsy (C8-T1) causes claw hand (ulnar nerve) and Horner's syndrome if T1 sympathetic chain is involved. First-line imaging: MRI brachial plexus; management includes physiotherapy and possible nerve graft.
• Circle of Willis and Stroke Syndromes: Anterior communicating artery aneurysm compresses optic chiasm causing bitemporal hemianopia. Middle cerebral artery (MCA) occlusion leads to contralateral hemiparesis (face and arm > leg) and global aphasia if dominant hemisphere. Posterior inferior cerebellar artery (PICA) occlusion causes lateral medullary syndrome (Wallenberg): ipsilateral Horner's, dysphagia, vertigo, and contralateral pain/temperature loss.
• Lumbar Puncture Landmarks: Perform at L3-L4 or L4-L5 interspace (spinal cord ends at L1-L2 in adults). Identify by drawing a line between the iliac crests (Tuffier's line). Contraindications: raised intracranial pressure (risk of tonsillar herniation), coagulopathy (INR >1.4, platelets <50,000). Normal CSF: opening pressure 10-20 cmH2O, glucose 2.2-3.9 mmol/L (60-80% of plasma), protein 0.15-0.45 g/L.
• Femoral Triangle and Hernias: Borders: inguinal ligament (superior), sartorius (lateral), adductor longus (medial). Femoral hernia emerges below and lateral to pubic tubercle (vs inguinal hernia above and medial). Strangulated femoral hernia is a surgical emergency; first-line repair via McVay or mesh. Contents: femoral nerve (lateral), artery (middle), vein (medial), and canal (medial).
• Cranial Nerves and Foramina: Optic nerve (CN II) passes through optic canal with ophthalmic artery. Trigeminal nerve (CN V): V1 (ophthalmic) through superior orbital fissure, V2 (maxillary) through foramen rotundum, V3 (mandibular) through foramen ovale. Jugular foramen syndrome (CN IX, X, XI) causes dysphagia, hoarseness, and trapezius weakness. First-line for trigeminal neuralgia: carbamazepine.
• Portal Hypertension and Portosystemic Anastomoses: Four main sites: oesophageal (varices → haematemesis), rectal (haemorrhoids), paraumbilical (caput medusae), retroperitoneal (splenorenal). Variceal bleeding managed with terlipressin, endoscopic band ligation, and prophylactic antibiotics (ceftriaxone). Child-Pugh score (bilirubin, albumin, INR, ascites, encephalopathy) stratifies prognosis: Class A (5-6 points) vs C (10-15 points).
• Anatomy of the Inguinal Canal: Deep inguinal ring (lateral to inferior epigastric vessels) and superficial ring (above pubic tubercle). Indirect hernia passes through deep ring (congenital, via processus vaginalis); direct hernia pushes through Hesselbach's triangle (medial to inferior epigastric vessels). In males, contents include spermatic cord (vas deferens, testicular artery, pampiniform plexus). Surgery: Lichtenstein tension-free mesh repair.
• Thoracic Outlet Syndrome: Compression of brachial plexus (lower trunk C8-T1) or subclavian vessels. Causes: cervical rib, scalenus anterior hypertrophy, or pectoralis minor tightness. Symptoms: ulnar nerve paraesthesia, hand weakness, Raynaud's phenomenon. Diagnosis: Adson's test (loss of radial pulse with head rotation). First-line: physiotherapy; surgery (first rib resection) if neurogenic or vascular compromise.

Common Traps in Anatomy Questions

• Confusing the femoral triangle boundaries: remember NAVEL (nerve, artery, vein, empty space, lymphatics) lateral to medial, but the femoral canal is the most medial structure.
• Thinking the spinal cord ends at L3 in adults: it terminates at L1-L2; lumbar puncture is safe at L3-L4 or below.
• Mixing up Erb-Duchenne (C5-C6) with Klumpke's (C8-T1): Erb affects shoulder and elbow, Klumpke affects hand and sympathetic chain.
• Assuming all hernias above the inguinal ligament are inguinal: femoral hernias are below and lateral to the pubic tubercle, often presenting as a groin lump below the ligament.
• Forgetting that the middle cerebral artery supplies the lateral surface of the brain, so stroke affects face and arm more than leg; anterior cerebral artery affects leg more.
• Believing the portal vein is formed by the union of superior mesenteric and splenic veins only: the inferior mesenteric vein drains into the splenic vein.

How to Revise Anatomy for the PMDC NLE Step 1

Focus on high-yield clinical anatomy: nerve injuries (brachial plexus, radial, ulnar, median, common peroneal), vascular territories (circle of Willis, coronary arteries), and anatomical spaces (axilla, femoral triangle, popliteal fossa). Questions are scenario-based, often with imaging (CT, MRI) or surface anatomy diagrams. Practise identifying structures on axial and coronal cross-sections. Emphasise embryology of common anomalies (e.g., patent ductus arteriosus, Meckel's diverticulum) and surgical approaches (e.g., appendicectomy incision at McBurney's point). Use Netter's atlas and question banks with clinical vignettes. Memorise key relations: e.g., the ureter crosses the pelvic brim at the bifurcation of the common iliac artery. For fractures, know the anatomical basis of displacement (e.g., Colles' fracture with dorsal angulation due to brachioradialis pull).

Practise it: MedLumen has 50 Anatomy questions for the PMDC NLE Step 1, each with a full explanation and references.