Botox [onabotulinumtoxinA] is a preventive treatment for chronic migraine — and the distinction between chronic and episodic is the whole story.
Who it is actually for
STRONG EVIDENCE, NARROW INDICATION
Botox is approved and evidenced for chronic migraine, defined as headache on 15 or more days a month, of which at least eight have migraine features, sustained for more than three months.
It is not a treatment for episodic migraine. The trials in patients with fewer than 15 headache days a month did not show benefit, and that is not a technicality — if you have migraine four times a month, Botox is unlikely to help you and there are better options. Counting your headache days honestly, on a calendar, is the single most useful thing you can do before this conversation.
It is also a preventive, not a rescue. It will not stop the attack you have today; for that see IV migraine therapy.
How it is given
The evidence rests on one specific injection protocol, and it is worth knowing that it is a fixed one rather than improvised. It uses 155 units across 31 sites spread over the forehead, temples, back of the head, neck and shoulders, repeated every 12 weeks. The needles are very fine and the whole appointment takes about fifteen minutes. There is no sedation and you drive yourself home.
Cosmetic Botox and migraine Botox are not the same treatment. The sites, the dose and the purpose are different, and a cosmetic pattern will not treat migraine.
Expectations, honestly
The effect builds. Most people who respond do not respond fully to the first round — the benefit typically accumulates over two to three cycles, which means roughly six months before you and I can say whether it works for you. It reduces headache days rather than abolishing them; a meaningful response is a substantial cut in frequency, not a cure.
Common effects are neck stiffness and soreness at the injection sites for a few days. Temporary eyelid or brow droop happens in a small minority and resolves. It is avoided in pregnancy and in some neuromuscular conditions.
Before Botox, rule out rebound
A great many people who meet the 15-day threshold are in a medication-overuse cycle, where daily acute treatment is sustaining the daily headache. Treating that first sometimes drops the frequency below the chronic threshold on its own. Starting Botox without addressing it means paying for an expensive preventive to fight a problem the medicine cabinet is creating.