PONOS CLINIC · HEADACHE CENTRE
Trigeminal autonomic cephalalgias (TACs)
When a unilateral headache with autonomic symptoms requires a precise differential diagnosis.
What are TACs?
The trigeminal autonomic cephalalgias are primary headache disorders typically characterised by unilateral pain associated with cranial autonomic signs on the same side, such as tearing, eye redness, nasal congestion, a runny nose, eyelid swelling or ptosis.
Autonomic symptoms alone are not enough to establish a TAC diagnosis: the duration and frequency of attacks, pain location, laterality, behaviour during an attack and response to specific treatments are particularly important.
The main types
Cluster headache
Severe attacks, usually around the eye or temple, with a clearly defined side and autonomic symptoms.
Paroxysmal hemicrania
Brief, frequent unilateral attacks with autonomic features. A complete response to indometacin is a characteristic diagnostic feature.
SUNCT and SUNA
Very brief, neuralgiform attacks, often occurring many times a day, associated with conjunctival injection and tearing or other cranial autonomic symptoms.
Hemicrania continua
Strictly unilateral, continuous pain, with possible exacerbations and autonomic symptoms. A complete response to indometacin is central to the diagnostic assessment.
When a TAC can resemble migraine
Nausea, photophobia and phonophobia can also occur in TACs; conversely, some people with migraine may have cranial autonomic symptoms. Differential diagnosis therefore requires a careful reconstruction of the headache’s timing and pattern.
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The diagnostic pathway
- Establish duration, frequency, periodicity and laterality.
- Identify associated autonomic and migraine-like symptoms.
- Distinguish TACs, migraine and neuralgias.
- Exclude secondary causes when indicated.
- Assess specific diagnostic treatment responses, including indometacin in appropriate clinical presentations.
Standard treatment and the role of interventional pain management
TACs are not an automatic indication for interventional procedures. For cluster headache, for example, European guidelines recommend oxygen and sumatriptan for attacks, with verapamil as the main preventive option.
The role of interventional pain management may be considered for selected patients with a specific clinical question, after standard treatments have been reviewed.
- greater occipital nerve blocks in selected settings;
- assessment of the sphenopalatine ganglion (SPG) when the trigeminal-autonomic component is clinically relevant;
- transmucosal SPG testing when indicated;
- neuromodulation techniques only after individual patient selection.
Key references
McClendon D, Riechers RG. A Comprehensive Review of Trigeminal Autonomic Cephalalgias. 2025.
May A, et al. European Academy of Neurology guidelines on the treatment of cluster headache. 2023.
Giani L, Proietti Cecchini A, Leone M. Cluster headache and TACs: state of the art. 2020.