TACs (Trigeminal Autonomic Cephalalgias) Ottawa Program

You may have TAC rather than migraine if your attacks:

• Are side-locked: always occurring exclusively in the same side of the head

• Are very severe and short-lasting

• Occur multiple times per day

• Cause eye redness, tearing, or nasal symptoms

• Make you feel restless or unable to lie down

The diagnosis is primarily made on clinical history (i.e., there is no investigation that proves someone has or does not have a TAC)

The diagnosis is based primarily on:

• An expertly taken history

• Presence of autonomic symptoms

• Presence of agitation/restlessness

• Exclusion of secondary headache disorders

• Response to condition-specific treatments (i.e., indomethacin)

Imaging may be selectively used to exclude secondary causes when appropriate.

In selected cases, a structured indomethacin trial is used as a diagnostic tool.

Indomethacin is a unique anti-inflammatory that is useful in headache medicine because:

• Some TACs respond specifically and dramatically

• A clear response helps confirm the diagnosis

• Lack of response helps exclude certain TACs

To diagnose or exclude hemicrania continua and paroxysmal hemicrania, an indomethacin trial is typically done.

Refer to our indomethacin trial guide for more information.

Both SUNCT/SUNA and trigeminal neuralgia can present with severe one-sided brief neuralgic attacks, and it may be difficult to distinguish one from the other.

In general, the following principles apply to help differentiate SUNCT/SUNA from trigeminal neuralgia:

• SUNCT/SUNA typically affects the ocular region more (i.e., the first branch of the trigeminal nerve)

• SUNCT/SUNA typically has more prominent autonomic symptoms (e.g., tearing)

• Trigeminal neuralgia tends to affect more the middle and lower parts of the face (i.e., second and third branches of the trigeminal nerve)

• While trigeminal neuralgia must be triggerable by innocuous stimuli (e.g., triggered by touch, cold air, water), SUNCT/SUNA tends to be less triggerable

Lamotrigine is an antiseizure medication is commonly used in epilepsy and mood disorders, but it is also used in certain headache and neuralgiform pain conditions. It is the first-line preventive for SUNCT/SUNA

Lamotrigine is not a painkiller and does not work immediately.

Lamotrigine works by:

• Stabilizing electrical activity in nerve cells

• Reducing abnormal nerve firing

• Dampening pain pathways involved in neuralgiform headache attacks

This mechanism is particularly relevant for very short, frequent attacks, such as those seen in SUNCT/SUNA.

Lamotrigine is typically started at a low dose and gradually titrated. The dosing schedule is individualized.

• Taken by mouth

• Must be started at a very low dose

• Dose is increased slowly over weeks

A common dosing schedule involves:

• Lamotrigine 25 mg orally daily for 2 weeks

• If the headache attacks persist and the medication is well-tolerated, it can be increased by 25 mg every two weeks to a maximum of 100 mg)

• If side effects arise, then medical attention is warranted and  lamotrigine is either discontinued or its dose lowered (depending on the side effects)

Common side effects

Many people tolerate lamotrigine well.

Possible side effects include:

• Dizziness

• Headache

• Nausea

• Fatigue

• Sleep disturbance

These are often mild and improve with time or dose adjustment.

Important side effects

Lamotrigine can rarely cause serious skin reactions.

You should seek medical advice urgently if you develop:

• A new rash

• Rash with fever

• Mouth sores

• Skin peeling

Starting low and increasing slowly dramatically reduces this risk.