Neurology Study Guide

📖 Core Concepts Neurology – medical specialty that diagnoses & treats disorders of the brain, spinal cord, and peripheral nerves. Neuroscience – basic science of the nervous system; provides the pathophysiologic basis for neurology. Neurologist – physician who evaluates, localizes, and manages neurological disease without surgery. Neurosurgery – surgical counterpart; deals with operative treatment of nervous‑system lesions. Clinical Localization – using exam findings (motor, sensory, reflex, gait) to pinpoint the anatomic level of a lesion (e.g., cortical, subcortical, brain‑stem, spinal). Neuroimaging – CT (quick, good for hemorrhage) and MRI (high‑resolution soft‑tissue, best for most lesions). Neurophysiology – EEG, EMG, NCS, evoked potentials; record electrical activity to diagnose functional disorders. 📌 Must Remember Neurology ≠ Neurosurgery – neurologists do nonsurgical management. CT → acute bleed / bone; MRI → demyelination, tumor, ischemia (subacute/chronic). EEG → brain cortical activity (seizures, encephalopathy). EMG/NCS → peripheral nerve & muscle disease (neuropathy, radiculopathy, myopathy). Lumbar puncture indications: suspected meningitis, subarachnoid hemorrhage (negative CT), inflammatory/autoimmune CNS disease, atypical neuro‑infection. Motor strength grading: 0‑5 (5 = normal, 0 = no contraction). Deep tendon reflexes (DTRs): hyper‑reflexia → upper motor neuron (UMN); hypo‑/absent → lower motor neuron (LMN). Common conditions: stroke, epilepsy, Parkinson’s, MS, migraine, Alzheimer’s, peripheral neuropathy, radiculopathy, sleep disorders. 🔄 Key Processes Neurological Physical Exam Mental status (orientation, memory, language, executive). Cranial nerve testing (CN I–XII: visual acuity, extra‑ocular movements, facial sensation, etc.). Motor exam – grade strength, observe bulk, look for pronator drift. Coordination – finger‑nose, heel‑shin, rapid alternating movements. Reflexes – test DTRs, plantar response (Babinski). Sensory – light touch, pinprick, vibration, proprioception. Gait – normal, ataxic, spastic, foot‑drop patterns. Lumbar Puncture (LP) Indications → infection, SAH, inflammatory CNS disease. Contraindications → increased ICP with mass effect, coagulopathy, skin infection at site. Steps: patient lateral decubitus → identify L3‑L4 (or L4‑L5) interspace → insert needle → obtain opening pressure → collect tubes (cell count, protein, glucose, cultures, special studies). Imaging Decision Tree Acute focal deficit → CT first (rule out hemorrhage). If CT negative & suspicion for ischemia, demyelination, tumor → MRI. Chronic progressive symptoms → MRI ± contrast; consider CT if MRI contraindicated. 🔍 Key Comparisons Neurology vs Neurosurgery – Neurology: diagnostic, medical therapy, no incision. Neurosurgery: operative interventions, hardware implantation, tumor resection. EEG vs EMG – EEG: records cortical brain activity → seizures, encephalopathy. EMG: records peripheral muscle electrical activity → neuropathy, myopathy. CT vs MRI – CT: fast, excellent for bone & acute bleed; MRI: superior soft‑tissue contrast, no radiation, longer scan time. Upper Motor Neuron (UMN) vs Lower Motor Neuron (LMN) signs – UMN: spasticity, hyperreflexia, Babinski, clonus. LMN: flaccidity, muscle atrophy, hyporeflexia, fasciculations. ⚠️ Common Misunderstandings “All seizures need EEG” – Not always; a clear clinical seizure without focal features may be diagnosed clinically. “Normal MRI rules out stroke” – Early ischemic changes can be invisible on MRI; clinical picture may still indicate stroke. “LP is always safe” – Can precipitate herniation in patients with mass effect; always assess opening pressure and imaging first. “Peripheral neuropathy = LMN lesion” – Some neuropathies produce mixed UMN‑LMN signs if central pathways are involved (e.g., ALS). 🧠 Mental Models / Intuition “Box‑and‑Arrow” localization – Visualize the nervous system as boxes (cortex, thalamus, brainstem, spinal cord) connected by arrows (tracts). Each exam finding narrows the box where the arrow is broken. “Rule of 3 for imaging” – 1️⃣ Acute bleed → CT, 2️⃣ Non‑hemorrhagic stroke/demyelination → MRI, 3️⃣ Contraindication to MRI → CT or contrast‑enhanced CT. 🚩 Exceptions & Edge Cases MRI contraindications – Pacemakers, certain metallic implants → use CT or “fast‑MRI” protocols. CSF glucose – Can be normal in bacterial meningitis if patient is hyperglycemic; interpret relative to serum glucose. EEG in sedated patients – Sedatives can mask epileptiform activity; may need drug‑free recording. 📍 When to Use Which Order CT when: (a) < 6 h from symptom onset, (b) suspicion for intracranial hemorrhage, (c) patient unstable for long scan. Order MRI when: (a) subacute/chronic focal deficit, (b) demyelinating disease suspected, (c) tumor evaluation needed. Choose EEG for: new‑onset seizure, unexplained altered mental status, encephalopathy work‑up. Choose EMG/NCS for: peripheral neuropathy, radiculopathy with atypical presentation, myopathy suspicion. 👀 Patterns to Recognize Isolated cranial nerve palsy + normal MRI → consider microvascular ischemia (e.g., CN III palsy in diabetes). Progressive spastic paresis + hyperreflexia → UMN lesion (e.g., MS plaque, spinal cord compression). Distal weakness + sensory loss + absent DTRs → LMN/peripheral neuropathy. Morning headaches + papilledema → increased intracranial pressure → CT first. 🗂️ Exam Traps “Normal CT = no stroke” – early ischemia may be invisible; look for clinical timing and consider MRI. “Absent Babinski = LMN lesion” – a normal plantar response can be present in early UMN lesions; assess other UMN signs. “All headaches need LP” – LP is reserved for red‑flag features (fever, neck stiffness, immunocompromise) after imaging excludes mass lesion. “Peripheral neuropathy always shows decreased reflexes – early diabetic neuropathy may have normal or hyperactive reflexes due to mixed fiber involvement. --- Use this guide to quickly scan key ideas, compare common pitfalls, and decide which test or imaging study fits each clinical vignette.