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**Textbook:** Harrison’s Principles of Internal Medicine (21st Edition)  
**Chapter Number & Name:** Chapter 16 – Headache  
**Topics Covered:**  
- Classification: Primary vs. Secondary Headaches  
- Anatomy & Physiology of Headache  
- Clinical Evaluation of Acute Headache  
- Secondary Headache Causes (e.g., Meningitis, Hemorrhage, Tumor)  
- Chronic Daily Headache (CDH) & Medication Overuse  
- Brief Overview of Primary Headache Disorders  
**Page Numbers:** 180–200 (Approx.)

Headache

INTRODUCTION

  • Prevalence & Impact: Headache is a top cause of patient visits and disability worldwide.

  • Approach: Distinguish primary headache (headache is the disorder itself) from secondary headache (due to underlying pathology) using history, exam, and selective investigations.

HEADACHE BASICS

Anatomy & Physiology

  • Pain typically arises from pain-sensitive structures:

    • Scalp, dural sinuses, arteries, falx cerebri, large pial arteries.

  • Peripheral trigeminovascular system mediates intracranial pain signals → trigeminal nerve → central pain pathways.

  • Cranial autonomic symptoms (e.g., lacrimation, nasal congestion) occur via cranial parasympathetic outflow → seen in migraine, cluster headache.

Classification (International Headache Society)

  1. Primary Headaches (no exogenous cause)

    • Migraine

    • Tension-type headache

    • Trigeminal autonomic cephalalgias (e.g., cluster)

    • Others (idiopathic stabbing, exertional)

  2. Secondary Headaches (exogenous cause)

    • Infection, trauma, vascular disorder, raised/low CSF pressure, etc.

ACUTE NEW-ONSET HEADACHE

Red Flags / Alarming Features

  • “Worst headache of life,” thunderclap onset (seconds-minutes) → suspect subarachnoid hemorrhage.

  • Fever, stiff neck → suspect meningitis.

  • Progressive neurologic deficit or papilledema → possible tumor, abscess, increased intracranial pressure.

  • Elderly with new headache → consider temporal arteritis or structural lesion.

  • Severe headache triggered by cough/exertion → possible posterior fossa lesion or aneurysm.

Initial Evaluation

  • Neurologic exam is crucial.

  • Consider imaging (CT/MRI) ± lumbar puncture if suspicious of hemorrhage, infection, tumor, or structural abnormality.

  • Identify any emergent condition first.

SECONDARY HEADACHES

Meningitis

  • Severe headache, nuchal rigidity, fever, photophobia.

  • Diagnosis: Lumbar puncture.

  • Note: Meningitis can present with features mimicking migraine (throbbing pain, photophobia).

Intracranial Hemorrhage

  • Subarachnoid hemorrhage: sudden, severe “thunderclap headache” ± altered consciousness, neck stiffness.

  • Confirm with CT; if negative and high suspicion, do LP (xanthochromia).

Brain Tumor

  • Headache often dull, worse with exertion, can have nausea, vomiting.

  • Doesn’t typically present as an abrupt severe headache.

  • Imaging is diagnostic.

Temporal (Giant Cell) Arteritis

  • In elderly, new headache (temporal location), jaw claudication, visual disturbances → risk of blindness.

  • Elevated ESR, temporal artery biopsy confirms.

  • Immediate high-dose steroids (prednisone) if suspected.

Glaucoma

  • Severe eye pain + headache, possibly with N/V; eye is red, pupil mid-dilated and unreactive.

  • Measure intraocular pressure promptly.

PRIMARY HEADACHES

(Detailed coverage in Chap. 430)

  • Migraine: Recurrent throbbing headaches ± aura, photophobia, nausea.

  • Tension-Type: Bilateral, band-like, mild-moderate, no significant vomiting or photophobia.

  • Trigeminal Autonomic Cephalalgias: e.g., Cluster headache with unilateral severe orbital pain, autonomic features.

CHRONIC DAILY HEADACHE (CDH)

Overview

  • Headache ≥15 days/month; includes various primary & secondary causes:

    • Chronic migraine, chronic tension-type, hemicrania continua, new daily persistent headache (NDPH), medication-overuse.

Medication-Overuse Headache

  • Overuse of analgesics (opioids, barbiturates, combination analgesics, triptans) can worsen headache frequency or intensity.

  • Key step → reduce/stop overused medication → often improves headache frequency.

  • Initiate or optimize preventive medication (e.g., tricyclics, topiramate) only after or during withdrawal.

NEW DAILY PERSISTENT HEADACHE (NDPH)

  • Sudden onset (clearly recalled “day 1”) daily headache that persists.

  • Must rule out secondary causes:

    • Post-subarachnoid hemorrhage, low or high CSF pressure, meningitis, trauma, etc.

Types of Secondary NDPH

  • Low CSF volume headache: post-LP or spontaneous leak → postural headache (worse upright, better lying down).

    • MRI: diffuse meningeal enhancement.

    • Tx: bed rest, IV caffeine, epidural blood patch if indicated.

  • High CSF pressure headache: e.g., pseudotumor cerebri → daily morning headache, obesity, papilledema.

  • Posttraumatic: can follow TBI or infections; normal imaging, often with comorbid dizziness or memory issues.

Treatment

  • Focus on primary phenotype (migraine-like or tension-type) + address any secondary factor.

  • Tricyclics, anticonvulsants (e.g., topiramate, valproate), or other prophylactics are used.

HEADACHE MANAGEMENT IN PRIMARY CARE

  • Goal: Identify red flags for secondary headache. Otherwise, treat as primary headache (migraine, tension-type) with standard therapies.

  • If diagnostic uncertainty, atypical features, poor response to basic treatments, or complicated presentation → Refer to specialist (neurology, headache clinic).

REFERENCES (APA Style, Annotated)

  • Headache Classification Committee of IHS. (2018). The international classification of headache disorders (3rd ed.). Cephalalgia, 38(1), 1–211.

    — Standard framework for categorizing primary & secondary headaches.

  • Kernick, D., & Goadsby, P. J. (2008). Headache: A Practical Manual. Oxford University Press.

    — Clinical manual focusing on practical diagnosis and management.

  • Lance, J. W., & Goadsby, P. J. (2005). Mechanism and Management of Headache (7th ed.). Elsevier.

    — Classic reference detailing pathophysiology and treatment strategies.

  • Silberstein, S. D., et al. (2021). Wolff’s Headache and Other Head Pain (9th ed.). Oxford University Press.

    — Comprehensive textbook covering all aspects of headache disorders.

🔴 Exam Alert & Key Point:
- Always exclude secondary causes (meningitis, hemorrhage, tumor, temporal arteritis) in new or alarming headache.
- Chronic daily headaches often involve overuse of analgesics → stopping them is crucial.
- Primary headaches are common but can be disabling; confirm diagnosis & optimize treatment early.

[▶️ Video Placeholder: “Fundamental Headache Exam Techniques & Red Flags Demonstration”]

If additional details on specific headache syndromes or management strategies are required, see Chap. 430 on migraine and other primary headaches, or let me know!