Section 5.4: Headache Syndromes & Cranial Nerve Disorders

PANCE Clinical Significance

Primary headache syndromes (tension, migraine, cluster) and facial nerve disorders (Bell's palsy) are frequent clinical encounters. On the PANCE, candidates must differentiate these conditions based on key features (such as pain distribution, associated autonomic symptoms, or the ability to wrinkle the forehead) and select appropriate abortive and prophylactic therapies while recognizing critical contraindications.

Tension Headaches

• Pathophysiology: The most common type of primary headache. The pathophysiology is multifactorial, involving pericranial muscle tenderness, stress, and muscle strain, though the exact mechanism remains unclear.
• Clinical Presentation:
  • Bilateral, non-pulsatile pain often described as a band-like pressure or tightening around the head.
  • Mild-to-moderate intensity.
  • Not worsened by routine physical activity (e.g., walking, climbing stairs).
  • No nausea or vomiting; may have mild photophobia OR phonophobia, but not both.
• Management:
  • Abortive: First-line treatment consists of NSAIDs (Ibuprofen, Naproxen) or Acetaminophen. Aspirin/Acetaminophen/Caffeine combinations (e.g., Excedrin) are also effective.
  • Prophylaxis: Indicated for chronic tension headaches (>15 days/month). Amitriptyline (Tricyclic Antidepressant - TCA) is the first-line preventive therapy.

Migraine Headaches

• Pathophysiology: A neurovascular disorder. Pathophysiology involves cortical spreading depression (a wave of neuronal depolarization that correlates with the migraine aura), leading to the activation of the trigeminal nerve afferents. This triggers the release of vasoactive neuropeptides, such as Calcitonin Gene-Related Peptide (CGRP) and substance P, causing neurogenic inflammation, vasodilation of dural blood vessels, and pain sensitization.
• Clinical Presentation:
  • Typically unilateral, pulsating (throbbing) pain of moderate-to-severe intensity.
  • Worsened by routine physical activity.
  • Associated with nausea and/or vomiting, photophobia, and phonophobia.
  • Migraine with Aura (20% of cases): Preceded by transient, reversible neurological deficits (most commonly visual, such as scintillating scotomas or fortification spectra) lasting 5–60 minutes before the headache begins.
• Management:
  • Abortive (Mild-to-Moderate): NSAIDs or Acetaminophen.
  • Abortive (Moderate-to-Severe or unresponsive to NSAIDs): Triptans (e.g., Sumatriptan) are first-line. They are 5-HT 1B/1D receptor agonists that cause vasoconstriction of cranial vessels and inhibit the release of pro-inflammatory neuropeptides.
    • Triptan Contraindications: Coronary Artery Disease (CAD), history of myocardial infarction, Printzmetal's variant angina, uncontrolled hypertension, history of stroke/TIA, peripheral vascular disease, and pregnancy due to risk of vasospastic events.
  • Prophylaxis (Indicated if >= 4 attacks/month or highly disabling):
    • Beta-blockers: Propranolol is first-line.
    • Anticonvulsants: Topiramate (associated with weight loss, kidney stones, cognitive slowing, and acute angle-closure glaucoma) or Valproic acid.
    • TCAs: Amitriptyline.
    • CGRP Antagonists: Monoclonal antibodies (e.g., Erenumab).

Cluster Headaches

• Pathophysiology: Part of a group of disorders known as Trigeminal Autonomic Cephalgias (TACs). Pathophysiology involves hypothalamic activation and activation of the trigeminal-parasympathetic reflex, leading to severe unilateral orbital pain and cranial autonomic signs.
• Clinical Presentation:
  • Unilateral, excruciating, sharp, boring, or burning pain localized in the orbital, supraorbital, or temporal region.
  • Brief duration (15–180 minutes) but occurs in clusters (e.g., daily at the same time of day or night, often waking the patient from sleep, for weeks or months, followed by periods of remission).
  • Associated with at least one ipsilateral cranial autonomic symptom: lacrimation (tearing), rhinorrhea (runny nose), nasal congestion, miosis and ptosis (Horner's syndrome features), and facial sweating.
  • Unlike migraine patients who lie still in a dark room, cluster headache patients are typically agitated, pacing the room or rocking.
• Management:
  • Abortive: First-line therapy is 100% high-flow oxygen (12–15 L/min via a non-rebreather mask for 15 minutes) or subcutaneous/nasal Sumatriptan. Oral therapies are ineffective due to slow onset.
  • Prophylaxis: Verapamil (calcium channel blocker) is the first-line preventive agent. Short-course oral prednisone or suboccipital nerve blocks can be used as transitional therapy while verapamil is titrated.

Bell's Palsy

• Pathophysiology: Acute, idiopathic lower motor neuron paresis or paralysis of the facial nerve (Cranial Nerve VII). It is thought to be caused by viral-induced inflammation and swelling of the facial nerve (most commonly attributed to Herpes Simplex Virus - HSV-1 reactivation) within the narrow facial canal.
• Clinical Presentation:
  • Acute onset (typically < 72 hours) of unilateral facial paralysis.
  • Forehead involvement (Key Feature): Inability to wrinkle the forehead, close the eye, or smile on the affected side.
  • Drooling, loss of taste on the anterior two-thirds of the tongue, hyperacusis (increased sensitivity to sound due to paralysis of the stapedius muscle), and decreased lacrimation leading to a dry eye.
• Clinical Differentiation from Stroke:
  • Bell's Palsy (Lower Motor Neuron): Affects the entire half of the face, including the forehead. The patient cannot wrinkle the forehead on the affected side.
  • Ischemic Stroke (Upper Motor Neuron): Spares the forehead. The patient can wrinkle the forehead bilaterally due to bilateral cortical representation of the upper facial muscles.
• Management:
  • First-line Pharmacotherapy: Oral Prednisone (corticosteroid) 60–80 mg daily for 7 days, initiated within 72 hours of symptom onset. This reduces facial nerve edema.
  • Antivirals: The addition of Valacyclovir or Acyclovir is beneficial in severe cases (House-Brackmann grade IV or higher).
  • Eye Protection (Critical Non-pharmacologic Care): Because the patient cannot close their eye, they are at high risk for corneal exposure keratitis, abrasions, and ulceration. Instruct the patient to use artificial tears during the day, apply lubricating ointment at night, and tape the eye shut during sleep.

Classic PANCE Traps & Clinical Pearls

• The Forehead Sparing Trap: If a patient presents with unilateral facial weakness but can wrinkle their forehead bilaterally, do not diagnose Bell's palsy. This is an upper motor neuron lesion (e.g., Stroke) that spares the forehead because of bilateral cortical representation. Immediate stroke protocol should be activated.
• The Triptan Contraindication Trap: Never prescribe sumatriptan to patients with cardiovascular risk factors (angina, history of myocardial infarction, or peripheral vascular disease) or uncontrolled hypertension. Triptans are vasoconstrictors and can cause acute coronary spasm or cerebral ischemia.
• The Cluster Headache Oral Treatment Trap: Do not treat an acute cluster headache with oral medications (like oral sumatriptan). The pain reaches its peak within minutes and the headache is short-lived, so oral absorption is too slow. Use 100% oxygen or subcutaneous sumatriptan instead.