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Clinical Evaluation, Etiological Diagnosis, and Contemporary Pharmacotherapy of Primary and Secondary Headache Disorders

Headache represents one of the most prevalent clinical complaints in outpatient medicine, possessing a 1-year prevalence of approximately 90% and a lifetime prevalence approaching 99% in the adult population. While the vast majority of cephalalgic presentations stem from benign primary headache syndromes, headache can also serve as the initial manifestation of severe, life-threatening intracranial or systemic pathologies. Accurate clinical classification and rapid diagnostic differentiation are therefore essential. The International Classification of Headache Disorders established by the International Headache Society (IHS) provides a standardized taxonomy dividing headache into primary disorders—those without an underlying structural, vascular, or metabolic etiology—and secondary disorders, which are symptomatic of an identifiable pathological condition.

Elucidating the neuroanatomical origins of cranial pain is crucial for etiological diagnosis. The brain parenchyma itself, as well as the arachnoid membrane, ependyma, and the majority of the dura mater, is entirely insensate to pain. Intracranial nociception is mediated exclusively by a circumscribed set of pain-sensitive structures: cranial nerves V (trigeminal), VII (facial), IX (glossopharyngeal), and X (vagus); the proximal segments of the internal carotid and cerebral arteries forming the circle of Willis; the dural venous sinus network; large meningeal arteries; and extracranial tissues including the scalp, pericranial muscles, cutaneous nerves, paranasal sinus mucosa, teeth, and upper cervical spinal nerves ($C_2$ and $C_3$).

Nociceptive signaling from supratentorial pain-sensitive structures is primarily transmitted via the ophthalmic division ($V_1$) of the trigeminal nerve, whereas infratentorial and posterior fossa structures send afferent signals through the upper cervical nerve roots. Both pathways converge within the trigeminocervical complex (TCC), which extends from the midpons down to the $C_3$ spinal cord segment. This central convergence accounts for the clinical phenomenon of referred headache pain, wherein posterior fossa lesions manifest as anterior frontotemporal pain, or cervical spine pathology presents as retro-orbital cephalalgia.

Differential Diagnosis of Primary Headache Disorders

Primary headache disorders constitute over 90% of cephalalgic presentations in clinical practice. The primary headache entities—migraine, tension-type headache, cluster headache and other trigeminal autonomic cephalalgias, and miscellaneous primary headache syndromes—exhibit distinct neurobiological mechanisms, temporal profiles, and clinical features.

Migraine Subtypes and Pathophysiology

Migraine is a chronic, neurovascular disorder characterized by recurrent, episodic headache attacks accompanied by sensory hypersensitivity and autonomic symptoms. Pathophysiologically, migraine reflects a neurogenetically altered threshold of central nervous system excitability. The aura phase, experienced by approximately 20% of migraineurs, is driven by cortical spreading depression (CSD)—a slow wave of neuronal and glial depolarization that propagates across the cerebral cortex at a rate of 2 to 6 mm/minute, inducing transient cortical hyperperfusion followed by prolonged hypoperfusion. Head pain generation results from activation of the trigeminovascular system, triggering the antidromic release of vasoactive neuropeptides, most notably calcitonin gene-related peptide (CGRP), substance P, and neurokinin A from peripheral trigeminal nerve endings. This neuropeptide release induces neurogenic inflammation, marked by meningeal vasodilation, plasma protein extravasation, and mast cell degranulation, leading to sensitization of peripheral meningeal nociceptors and central neurons within the TCC.

Clinically, migraine is divided into two primary subtypes: migraine without aura (formerly common migraine) and migraine with aura (formerly classic migraine). Diagnostic criteria for migraine without aura require at least five attacks lasting 4 to 72 hours (untreated or unsuccessfully treated) displaying at least two of the following features: unilateral location, pulsating quality, moderate-to-severe pain intensity, and aggravation by or avoidance of routine physical activity. The pain must also be accompanied by at least one associated symptom: nausea and/or vomiting, or photophobia and phonophobia.

Migraine with aura involves fully reversible focal neurological symptoms that typically develop gradually over 5 minutes or more and last between 5 and 60 minutes. Visual auras represent the most common modality (99% of aura cases), presenting as positive phenomena (scintillating scotomas, fortification spectra/teichopsia) or negative phenomena (visual field deficits). Sensory paresthesias and dysphasic speech disturbances represent secondary aura manifestations.

Specific migraine variants warrant clinical differentiation due to their ability to mimic acute cerebrovascular events:

• Familial Hemiplegic Migraine (FHM): A rare autosomal dominant subtype (associated with CACNA1A, ATP1A2, or SCN1A gene mutations) featuring motor weakness as a component of the aura, often accompanied by confusion or altered consciousness.
• Brainstem Aura Migraine (formerly Basilar-Type Migraine): Characterized by aura symptoms originating from the brainstem or bilateral occipital lobes—including dysarthria, vertigo, tinnitus, hypacusia, diplopia, ataxia, and bilateral paresthesias—without motor weakness, followed by severe occipital cephalalgia.
• Acephalgic Migraine (Migraine Aura Without Headache): Isolated neurological aura symptoms occurring without subsequent headache, observed predominantly in older adults as late-life migraine accompaniments.
• Retinal Migraine: Monocular visual disturbance (scotoma or amaurosis) accompanying headache, requiring strict exclusion of anterior circulation transient ischemic attacks (TIAs).

Up to 45% of migraine patients display cranial autonomic symptoms—such as lacrimation, conjunctival injection, nasal congestion, or rhinorrhea—secondary to parasympathetic reflex activation via the sphenopalatine ganglion. This autonomic involvement leads to the clinical misdiagnosis of migraine as "sinus headache" in over 40% of affected individuals.

Tension-Type Headache

Tension-type headache (TTH) represents the most common headache disorder, possessing a lifetime prevalence of 78%. In contrast to migraine, TTH pain is typically bilateral, non-pulsating (described as a tight band, pressure, or weight around the head), of mild-to-moderate intensity, and is not exacerbated by routine physical activity. Nausea and vomiting are absent, though mild anorexia, photophobia, or phonophobia may occur (though not photophobia and phonophobia simultaneously).

TTH is categorized as episodic TTH (<15 headache days per month) or chronic TTH ($\ge 15$ days per month for at least 6 months). While peripheral myofascial nociception from pericranial muscle tenderness drives episodic TTH, central sensitization at the level of the spinal cord or brainstem plays a dominant role in the development of chronic TTH.

Cluster Headache and Other Trigeminal Autonomic Cephalalgias

Cluster headache is the most prevalent trigeminal autonomic cephalalgia, exhibiting a male-to-female ratio of 5:1 and a typical age of onset between 20 and 40 years. Unlike migraine or TTH, cluster headache features excruciating, strictly unilateral, boring, stabbing, or burning orbital, retro-orbital, or frontotemporal pain lasting 15 to 180 minutes if untreated. Attacks exhibit high circadian periodicity, occurring from 1 to 8 times daily, often awakening the patient from sleep, during active cluster periods lasting 4 to 8 weeks, followed by variable remission periods.

Cluster attacks are accompanied by prominent ipsilateral cranial autonomic features, including conjunctival injection, lacrimation, nasal congestion, rhinorrhea, forehead sweating, and partial Horner's syndrome (miosis and ptosis). During an acute attack, patients exhibit marked motor restlessness and agitation, pacing or rocking, which contrasts with the quiet immobility sought by patients during a migraine attack.

Chronic Daily Headache and Medication-Overuse Headache

Chronic Daily Headache (CDH) is an overarching construct defined as headache occurring $\ge 15$ days per month for longer than 3 consecutive months. CDH encompasses four major primary headache disorders: chronic/transformed migraine, chronic tension-type headache, hemicrania continua (a continuous unilateral pain exquisitely responsive to indomethacin), and new daily persistent headache (NDPH, characterized by unremitting daily pain starting abruptly without prior headache history).

A major factor in headache chronification is Medication-Overuse Headache (MOH). MOH develops when individuals with an underlying primary headache disorder overused acute symptomatic medications. Criteria for defining medication overuse include:

• Simple analgesics (acetaminophen, NSAIDs): $\ge 15$ days per month for $>3$ months.
• Triptans, opioids, ergotamines, or combination analgesics (containing caffeine, butalbital, or codeine): $\ge 10$ days per month for $>3$ months.

Continuous exposure to acute analgesics induces downregulation of central serotonergic pathways, upregulation of pro-nociceptive neuropeptides, and central sensitization, maintaining a refractory daily headache state that fails to respond to preventive therapies until the offending agent is withdrawn.

Diagnostic Evaluation and Etiological Identification of Secondary Headaches

Secondary headaches arise from underlying structural, vascular, infectious, neoplastic, or metabolic pathologies. Clinicians must systematically screen for secondary etiologies using validated red-flag diagnostic framework criteria, such as the SNOOP mnemonic (Systemic symptoms, Neurological deficits, Onset sudden/thunderclap, Older age at onset, Pattern change/Progressive).

Critical Secondary Headache Entities

Subarachnoid hemorrhage (SAH) presents classically as a thunderclap headache—a severe headache reaching maximum intensity within 60 seconds of onset. Ruptured intracranial saccular aneurysms account for over 80% of non-traumatic SAH cases. SAH cephalalgia is sudden, agonizing ("worst headache of life"), and frequently associated with nausea, emesis, neck stiffness (meningismus), focal neurological deficits, or transient loss of consciousness. Unruptured aneurysms, cerebral venous sinus thrombosis, carotid or vertebral artery dissections, reversible cerebral vasoconstriction syndrome (RCVS), and pituitary apoplexy must also be considered in the differential diagnosis of thunderclap headache.

Temporal (giant cell) arteritis (TA) is a systemic granulomatous panarteritis affecting medium and large arteries, occurring almost exclusively in individuals over 50 years of age (mean age 70). TA represents an ophthalmological emergency due to the risk of irreversible visual loss from anterior ischemic optic neuropathy. Headaches occur in 60% to 90% of TA cases, presenting as temporal or bifrontal throbbing, dull, or sharp pain, often worse at night. Key diagnostic findings include jaw claudication (occurring in 38% of cases), scalp tenderness, tender or pulseless superficial temporal arteries, and co-existing polymyalgia rheumatica (in 50% of cases).

Idiopathic intracranial hypertension (pseudotumor cerebri) primarily affects young, obese women of childbearing age. Patients present with daily continuous, pulsatile headaches, visual obscurations (transient darkening of vision with postural changes), pulsatile tinnitus ("roaring" noises), and horizontal diplopia secondary to cranial nerve VI (abducens) paresis. Funduscopic examination demonstrates bilateral papilledema in over 95% of cases. Uncontrolled elevation of intracranial pressure leads to progressive, permanent optic nerve atrophy and visual field constriction.

Headache is present in 30% to 70% of intracranial neoplasm cases at diagnosis. Tumor-related headaches are typically dull, steady, and non-throbbing, worsening with maneuvers that transiently raise intracranial pressure (coughing, straining, bending forward). Classic morning headaches exacerbated upon awakening occur in less than 20% of cases. Indications for neuro-oncological evaluation include new-onset headache in a patient with known systemic malignancy, progressive headache frequency or severity, focal neurological deficits, cognitive alterations, or new-onset seizures.

Acute bacterial paranasal sinusitis produces localized, dull, aching pain localized over the involved sinus cavity: maxillary (cheek, upper teeth), frontal (forehead), ethmoid (retro-orbital, nasal bridge), or sphenoid (vertex, occiput, or deep retro-orbital). Pain is typically accompanied by purulent nasal drainage, nasal congestion, fever, and local facial tenderness. Sphenoid sinusitis can be clinically silent regarding nasal symptoms, presenting solely as a severe, progressive headache that risks rapid complication by cavernous sinus thrombosis or bacterial meningitis.

Trigeminal neuralgia is characterized by paroxysmal, brief (lasting fractions of a second up to 2 minutes), severe, sharp, shooting, or electric shock-like pain confined to the distribution of one or more branches of the trigeminal nerve (most commonly $V_2$ or $V_3$). Pain is triggered by non-painful mechanical stimulation of cutaneous or mucosal trigger zones during activities such as chewing, talking, washing the face, or exposure to cold air. Over 80% of classic trigeminal neuralgia cases stem from neurovascular compression of the trigeminal root entry zone by an aberrant arterial loop (typically the superior cerebellar artery). Postherpetic neuralgia (PHN) involves persistent neuropathic pain lasting longer than 1 month following the acute dermatomal vesicular eruption of herpes zoster, with ophthalmic ($V_1$) involvement carrying a high risk of chronic burning pain, lancinating paroxysms, and tactile allodynia.

Systematic Diagnostic Approach

Establishing the etiological diagnosis of headache relies on a clinical pathway incorporating history, physical and neurological examinations, neuroimaging, laboratory biomarkers, and lumbar puncture. When screening for red flags, clinicians evaluate systemic signs, neurological deficits, onset characteristics, age factors, and pattern progression to dictate the appropriate diagnostic trajectory. In the absence of red flags, evaluation proceeds using standard IHS clinical criteria for primary headache disorders. When red flag features are identified, target-directed diagnostic testing protocols are initiated.

Magnetic Resonance Imaging (MRI) of the brain with intravenous gadolinium contrast is the imaging modality of choice for evaluating headache, possessing superior soft-tissue resolution compared to Computed Tomography (CT). MRI is required to evaluate suspected brain tumors, posterior fossa lesions, craniocervical junction malformations (e.g., Chiari I), pituitary apoplexy, cerebral venous sinus thrombosis, low or high CSF pressure states, meningeal carcinomatosis, and parenchymal inflammatory or infectious processes.

Non-contrast CT of the head is preferred in acute head trauma and hyperacute thunderclap headache to rule out subarachnoid hemorrhage. Non-contrast head CT detects subarachnoid blood with $>95\%$ sensitivity within the first 24 hours of aneurysm rupture, though sensitivity drops to 74% by day 3 and 50% by 1 week. CT of the paranasal sinuses in the coronal plane is the optimal imaging study for evaluating bony anatomy and mucosal disease in suspected sinusitis.

Lumbar Puncture (LP) is indicated following a negative brain CT or MRI scan when specific pathologies remain suspected:

• Exclusion of SAH: In patients presenting with thunderclap headache and a negative head CT, LP is mandatory to measure CSF opening pressure and evaluate CSF for red blood cells and xanthochromia (spectrophotometric breakdown of hemoglobin to bilirubin, differentiating true subarachnoid blood from a traumatic tap).
• Infectious/Inflammatory Meningoencephalitis: LP measures elevated protein, reduced glucose, and pleocytosis, enabling microbiological staining and PCR testing.
• Intracranial Pressure Alterations: Measuring CSF opening pressure is diagnostic for Idiopathic Intracranial Hypertension ($>250\text{ mm H}_2\text{O}$) and spontaneous intracranial hypotension ($<60\text{ mm H}_2\text{O}$).

Serological testing plays a targeted role in etiological headache evaluation. Erythrocyte Sedimentation Rate (ESR) and C-Reactive Protein (CRP) are mandatory in all patients $>50$ years of age presenting with new-onset or altered headache to screen for Temporal Arteritis. Westergren ESR is typically elevated ($>70\text{--}80\text{ mm/hr}$), though normal ESR occurs in up to 20% of cases; combining ESR and CRP provides a diagnostic specificity of 97% for TA. Complete Blood Count and metabolic panels rule out systemic etiologies such as severe anemia, hypoxemia, renal failure, or hypercalcemia. Electroencephalography (EEG) has no utility in the routine evaluation of headache disorders and is indicated only when clinical features suggest co-existing seizure activity or transient alteration of consciousness.

Contemporary Pharmacotherapy of Headache Disorders

The therapeutic management of headache encompasses acute (abortive) interventions designed to terminate individual attacks and preventive (prophylactic) regimens aimed at reducing attack frequency, severity, and chronification risk.

Acute Migraine Therapeutics

Acute therapeutic interventions must be instituted early in the attack phase when pain is mild to maximize therapeutic efficacy. Pharmacological selection follows a stratified care approach, matching drug potency to attack severity and disability.

For mild-to-moderate migraine attacks, non-prescription analgesics (acetaminophen) and NSAIDs (ibuprofen, naproxen sodium, aspirin, diclofenac) serve as initial agents. Fixed-dose oral combinations combining acetaminophen, aspirin, and caffeine demonstrate enhanced efficacy over single-agent analgesics.

Selective serotonin $5\text{-HT}_{1\text{B}/1\text{D}}$ receptor agonists (triptans)—including sumatriptan, zolmitriptan, rizatriptan, naratriptan, almotriptan, frovatriptan, and eletriptan—constitute first-line, migraine-specific abortive therapy for moderate-to-severe attacks. Triptans exert three complementary mechanisms: direct binding to vascular $5\text{-HT}_{1\text{B}}$ receptors mediating selective vasoconstriction of painful, distended cranial and meningeal arteries; activation of presynaptic $5\text{-HT}_{1\text{D}}$ receptors on peripheral trigeminal sensory nerve terminals, inhibiting neuropeptide release (CGRP, substance P); and central inhibition of nociceptive signal transmission across second-order neurons within the trigeminocervical complex.

For patients experiencing rapid onset, severe nausea, or early intra-attack gastroparesis, non-oral formulations (subcutaneous sumatriptan, intranasal sumatriptan, or intranasal zolmitriptan) bypass gastrointestinal absorption bottlenecks. Subcutaneous sumatriptan ($6\text{ mg}$) achieves rapid peak plasma concentrations, producing a 2-hour pain relief response in 79% of patients. Because $5\text{-HT}_{1\text{B}}$ receptors are expressed on human coronary vascular smooth muscle, all triptans can induce coronary vasoconstriction. Consequently, triptans are contraindicated in patients with established or suspected ischemic heart disease, prior myocardial infarction, Prinzmetal vasospastic angina, uncontrolled hypertension, peripheral vascular disease, or severe cerebrovascular disease.

Lasmiditan is a selective serotonin $5\text{-HT}_{1\text{F}}$ receptor agonist approved for acute migraine treatment. Unlike triptans, lasmiditan acts on peripheral and central neural structures without binding to vascular $5\text{-HT}_{1\text{B}}$ receptors, exerting no vasoconstrictive activity. It provides a safe abortive option for migraineurs with cardiovascular contraindications to triptans. Due to central nervous system penetration, common adverse effects include dizziness, sedation, somnolence, and paresthesias, necessitating a restriction on driving for 8 hours post-dose.

Oral small-molecule CGRP receptor antagonists (gepants)—including ubrogepant, rimegepant, and zavegepant (nasal spray)—represent a non-vasoconstrictive class of acute migraine therapeutics. Gepants competitively block the CGRP receptor, neutralizing CGRP-mediated nociception without inducing arterial constriction. Clinical trials demonstrate robust pain-freedom efficacy at 2 hours, minimal side effect burden, and negligible risk of inducing medication-overuse headache. Gepants are indicated for acute treatment in patients who exhibit incomplete responses or contraindications to triptans.

Migraine attacks persisting beyond 72 hours (status migrainosus) require parenteral therapeutic intervention:

• Rehydration with intravenous fluids to correct dehydration from persistent emesis.
• Intravenous Dihydroergotamine (DHE, $0.5\text{--}1.0\text{ mg}$), often combined with IV metoclopramide ($10\text{ mg}$) to prevent DHE-induced nausea (DHE and triptans must not be co-administered within 24 hours due to additive vasoconstriction).
• Intravenous neuroleptics: prochlorperazine ($10\text{ mg}$ IV) or chlorpromazine.
• Intravenous valproate sodium ($500\text{--}1000\text{ mg}$ IV infusion) or ketorolac ($30\text{--}60\text{ mg}$ IM/IV).
• High-dose parenteral corticosteroids (dexamethasone $4\text{--}10\text{ mg}$ IV) to interrupt central sensitization and mitigate attack recurrence.

Preventive Migraine Pharmacotherapy

Prophylactic therapy is indicated when migraines significantly impair quality of life despite optimized acute care, when acute medications are overused or contraindicated, in high attack frequencies ($\ge 4\text{--}6$ headache days per month), or in hemiplegic or brainstem aura variants.

Historically, migraine prophylaxis relied on repurposed oral medications from diverse drug classes:

• Beta-Blockers: Propranolol ($80\text{--}240\text{ mg/day}$), metoprolol ($50\text{--}200\text{ mg/day}$), and timolol reduce central sympathetic tone and elevate the threshold to cortical spreading depression. They are contraindicated in asthma, severe bradycardia, and peripheral arterial disease.
• Tricyclic Antidepressants (TCAs): Amitriptyline ($10\text{--}150\text{ mg}$ h.s.) and nortriptyline downregulate $5\text{-HT}_2$ receptors and inhibit norepinephrine/serotonin reuptake, proving effective for co-existing migraine, TTH, and insomnia. Adverse effects include anticholinergic symptoms (dry mouth, constipation), sedation, and weight gain. Venlafaxine (SNRI) offers similar prophylactic efficacy.
• Anticonvulsants: Topiramate ($50\text{--}100\text{ mg/day}$) blocks voltage-gated sodium/calcium channels, inhibits AMPA/kainate receptors, and enhances GABA activity. Divalproex sodium ($500\text{--}1000\text{ mg/day}$) elevates brain GABA levels. Topiramate causes paresthesias, cognitive slowing, anorexia, and nephrolithiasis. Valproate induces somnolence, tremor, weight gain, alopecia, and hepatotoxicity. Both are potent teratogens.

Prior to 2018, all migraine prophylactic drugs were repurposed agents burdened by poor tolerability, leading to high 1-year discontinuation rates ($>80\%$). The development of biologic and small-molecule inhibitors targeting CGRP marked the first disease-specific mechanism-driven preventive therapies. These target-directed agents fall into two classes: parenteral CGRP monoclonal antibodies (mAbs)—including Erenumab (receptor blocker), Fremanezumab, Galcanezumab, and Eptinezumab (ligand blockers)—and oral gepants formulated for prevention, such as Atogepant and Rimegepant.

In March 2024, the American Headache Society (AHS) published an updated consensus position statement on clinical practice guidance. Based on extensive clinical trial data and real-world evidence, the AHS formally elevated CGRP-targeting therapies (mAbs and gepants) to a first-line treatment option for migraine prevention, placing them alongside traditional oral preventives. Crucially, the AHS statement recommends that initiation of CGRP-targeting therapies should not require prior trial and failure of non-specific legacy oral medications (step-therapy edits). Clinical trials establish that CGRP-targeting agents demonstrate efficacy equal or superior to legacy oral options (achieving $\ge 50\%$ reduction in monthly migraine days in up to 70% of patients), maintain a favorable tolerability profile, produce rapid therapeutic onset, and lack major organ toxicity or drug-drug interactions.

Special Considerations: Pregnancy and Lactation

Managing migraine during pregnancy demands balancing maternal pain relief against fetal teratogenicity and microvascular disruption risks. Up to 70% of female migraineurs experience clinical improvement during the second and third trimesters due to stable elevated maternal estrogen levels. However, acute attacks occurring during the first trimester or postpartum require validated safety protocols.

Acetaminophen ($1000\text{ mg}$) is the preferred first-line analgesic throughout all trimesters. Short-term use of ibuprofen ($400\text{--}800\text{ mg}$) or diclofenac is acceptable during the first and second trimesters. However, NSAIDs are strictly contraindicated after 28 weeks of gestation (third trimester) due to the risks of premature closure of the fetal ductus arteriosus, impaired fetal renal function leading to oligohydramnios, and peripartum maternal hemorrhage. Metoclopramide is safe across all trimesters and serves as the antiemetic of choice. Subcutaneous sumatriptan may be deployed for severe refractory attacks when standard safe agents fail, as prospective registry data monitoring over 1,000 first-trimester sumatriptan exposures have shown no signal of teratogenic potential above background rates.

Ergot alkaloids (ergotamine tartrate, DHE) act as potent partial agonists at alpha-adrenergic receptors, inducing intense, prolonged vasoconstriction of uterine and placental blood vessels. This severely impairs uteroplacental blood flow, resulting in fetal hypoxia, vascular disruption anomalies (such as Möbius syndrome and neural tube defects), intrauterine growth restriction, spontaneous abortion, or fetal demise. Ergotamines also increase myometrial tone, triggering premature labor, and are absolutely contraindicated across all trimesters. Topiramate causes an increased incidence of oral cleft lip/palate, while divalproex sodium causes neural tube defects, craniofacial dysmorphism, cardiovascular anomalies, and long-term neurodevelopmental deficits (reduced childhood IQ). Both are contraindicated for migraine prophylaxis during pregnancy. ACE inhibitors and Angiotensin II Receptor Blockers (ARBs) cause fetal renal dysgenesis and skull hypoplasia. When preventive therapy is mandatory during pregnancy, proven beta-blockers (propranolol, metoprolol) or low-dose tricyclic antidepressants (amitriptyline) represent the safest options.

Management of Specific Primary Headache Entities

For acute cluster headache attacks, inhalation of 100% normobaric oxygen delivered at high flow rates ($10\text{--}15\text{ L/min}$) via a non-rebreathing face mask for 15 to 20 minutes terminates attacks in $>60\%$ of cases. Subcutaneous sumatriptan ($6\text{ mg}$) provides rapid relief in 75% of patients. Intranasal zolmitriptan or intranasal DHE represent secondary options. Transitional prevention using oral prednisone ($60\text{ mg/day}$ tapered over 2 weeks) or an ipsilateral greater occipital nerve block (injecting methylprednisolone and lidocaine) suppresses cluster paroxysms while long-term preventives are titrated. Verapamil is the drug of choice for long-term prophylaxis, given at daily doses ranging from $240\text{ mg}$ to $720\text{ mg/day}$ (requiring baseline and serial ECGs to monitor for PR interval prolongation and heart block). Secondary prophylactic agents include lithium carbonate ($300\text{--}900\text{ mg/day}$ with serum level monitoring), topiramate, and galcanezumab.

Carbamazepine ($200\text{--}1200\text{ mg/day}$) and Oxcarbazepine ($600\text{--}1800\text{ mg/day}$) represent first-line medical therapy for trigeminal neuralgia, stabilizing voltage-gated sodium channels in hyperexcitable trigeminal afferents. Complete blood count and liver function monitoring are required for carbamazepine due to risks of aplastic anemia and hyponatremia. Second-line agents include baclofen ($10\text{--}80\text{ mg/day}$), gabapentin ($90\text{--}2400\text{ mg/day}$), lamotrigine, or topiramate. For medically refractory trigeminal neuralgia, Microvascular Decompression (MVD)—a craniotomy isolating the trigeminal root from compressing arterial loops using a Teflon sponge—provides high rates of immediate and sustained pain relief. Percutaneous retrogasserian rhizotomy and stereotactic Gamma Knife radiosurgery offer effective minimally invasive alternatives.

Conclusions

The differential diagnosis and etiological identification of headache require a systematic clinical approach to distinguish primary headache syndromes from life-threatening secondary conditions. Diagnostic evaluation relies on screening for clinical red flags (SNOOP criteria), selective neuroimaging (contrast MRI), cerebrospinal fluid analysis via lumbar puncture, and targeted biomarkers (ESR/CRP). The pharmacological management of headache has undergone a paradigm shift, moving from empirical off-label oral drugs toward disease-specific mechanisms. The 2024 American Headache Society consensus statement elevating anti-CGRP therapies to first-line status for migraine prevention highlights this transformation, prioritizing targeted efficacy, rapid onset, and optimal tolerability. Concurrently, novel non-vasoconstrictive acute therapies (gepants and ditans) expand treatment options for patients with cardiovascular comorbidities, while management during pregnancy requires strict avoidance of vasoconstrictive ergotamines and teratogenic anticonvulsants to safeguard maternal and fetal health.