Trigeminal Autonomic Cephalalgias
Definition
Trigeminal autonomic cephalalgias (TACs) are a group of primary headache disorders characterized by:
- Unilateral trigeminal distribution pain (V1 ± V2)
- Prominent ipsilateral cranial autonomic features
- Short-lasting, severe attacks (except hemicrania continua)
Core Pathophysiology
1. Trigeminal–Autonomic Reflex
- Activation of trigeminal nociceptive pathways (V1)
- Reflex activation of parasympathetic outflow via facial nerve (CN VII)
- Through:
- Superior salivatory nucleus
- Sphenopalatine (pterygopalatine) ganglion
👉 Leads to:
- Lacrimation
- Conjunctival injection
- Nasal congestion
2. Hypothalamic Dysfunction
- Functional imaging → activation of posterior hypothalamus
- Explains:
- Circadian periodicity (cluster headache)
- Chronobiology of attacks
Classification (ICHD-3)
|
Disorder |
Key Feature |
|
Cluster headache |
Most common TAC |
|
Paroxysmal hemicrania |
Absolute indomethacin response |
|
SUNCT / SUNA |
Ultra-short attacks |
|
Hemicrania continua |
Continuous unilateral headache |
1. Cluster Headache
Key Features
- Severe, unilateral orbital/supraorbital pain
- Duration: 15–180 min
- Frequency: 1 every other day → 8/day
Autonomic Features (ipsilateral)
- Lacrimation
- Conjunctival injection
- Nasal congestion
- Ptosis/miosis (partial Horner’s)
Behavioral Feature
- Restlessness/agitation (pacing) → exam differentiator from migraine
Periodicity
- Occurs in clusters (weeks–months)
- Strong circadian pattern
Treatment
Acute
- 100% oxygen (12–15 L/min NRBM)
- Subcutaneous sumatriptan (first-line)
Preventive
- Verapamil (1st-line)
- Lithium (chronic cluster)
- CGRP monoclonals (e.g., galcanezumab)
2. Paroxysmal Hemicrania
- Severe unilateral pain (similar to cluster)
- Duration: 2–30 min
- Frequency: >5/day (often 10–40/day)
Diagnostic Hallmark👉 Complete response to indomethacin
Treatment
- Indomethacin = diagnostic + therapeutic
- Alternatives (rare): topiramate, celecoxib
3. SUNCT / SUNA
Definitions
- SUNCT = Short-lasting Unilateral Neuralgiform headache with Conjunctival injection and Tearing
- SUNA = Same but autonomic features may vary
Features
- Duration: 1–600 seconds
- Frequency: up to 100s/day
- Pain: stabbing, electric (trigeminal neuralgia-like)
Key Differentiator
- Prominent autonomic features (vs trigeminal neuralgia)
Treatment
- Lamotrigine (1st-line)
- Others:
- Topiramate
- Carbamazepine (less effective)
4. Hemicrania Continua
Key Features
- Continuous unilateral headache
- Superimposed exacerbations
- Autonomic features during exacerbations
Diagnostic Hallmark👉 Absolute response to indomethacin
Investigations
- Diagnosis is clinical (ICHD-3)
- MRI brain indicated if:
- Atypical features
- Neurological deficit
- Suspicion of secondary TAC
Secondary causes:
- Pituitary tumors
- Posterior fossa lesions
Comparison Table
|
Feature |
Cluster |
Paroxysmal Hemicrania |
SUNCT/SUNA |
Hemicrania Continua |
|
Duration |
15–180 min |
2–30 min |
1–600 sec |
Continuous |
|
Frequency |
1–8/day |
>5/day |
Up to 100s/day |
Continuous |
|
Severity |
Very severe |
Very severe |
Severe |
Moderate–severe |
|
Autonomic |
+++ |
+++ |
+++ |
+ (during flare) |
|
Restlessness |
Present |
Sometimes |
No |
No |
|
Indomethacin |
No |
Yes |
No |
Yes |
|
Sex |
M>F |
F>M |
Equal |
Equal |
Differentials to Know
|
Condition |
Key Difference |
|
Migraine |
Longer duration, prefers rest |
|
Trigeminal neuralgia |
No autonomic features |
|
Sinusitis |
Less severe, not paroxysmal |
|
Temporal arteritis |
Older age, ESR ↑ |
Exam Pearls
- Cluster headache = restless patient + circadian periodicity
- Indomethacin-responsive headaches = PH + hemicrania continua
- SUNCT = seconds + conjunctival injection + tearing
- Always unilateral + autonomic features = think TACs
- Oxygen is first-line acute therapy in cluster headache
- Posterior hypothalamus = key structure