Topiramate is a medication that has been approved by the Food and Drug Administration (FDA) for the treatment of patients with seizures. The trade name for this drug is Topamax®. Topiramate has not been approved by the FDA for the treatment of cluster headache and is experimental for the purposes of this research study. If a subject participates in this study, he/she will increase his/her dose of topiramate rapidly in the first few weeks to try to stop the cluster attacks and then will continue on a maintenance dose of topiramate in order to determine if it can prevent attacks from occurring during that cluster period. We believe that this will lead not only to a faster but a more complete remission of the cluster period.

Inclusion Criteria:

• Subjects between the ages of 18 and 65 with a diagnosis of cluster headache (episodic or chronic) as defined by the International Classification of Headache Disorders (2nd edition)
• Subjects must have a lifetime prevalence of at least 2 prior cluster cycles.
• Subjects must experience one or more attacks/ day during baseline period
• Subjects must have a typical cluster period lasting at least 8 weeks. Subjects must present in active cluster period and the expected remaining duration of the cluster cycle must be at least 8 weeks from Baseline visit.
• Subjects with other headache types are eligible provided the subject is able to differentiate these headaches from cluster headaches.
• Subject is using or agrees to use for the duration of participation a medically acceptable form of contraception (as determined by investigator), if female of child-bearing potential
• Subject has negative urine pregnancy test prior to study entry, if female of child-bearing potential
• Subject is able to understand and comply with all study requirements
• Subject provides written informed consent prior to any screening procedures being conducted

Exclusion Criteria:

• Women who are pregnant or lactating
• Subjects who, in the investigators opinion, have a history or have evidence of a medical or psychiatric condition that would expose them to an increased risk of a significant adverse event or would interfere with the assessments of efficacy and tolerability during this trial
• Subjects who require a change in medication or existing regimen of medication for the prophylaxis of cluster in the 4 weeks prior to Baseline visit and for the duration of the trial
• Subjects who have cluster headaches that typically exceed 4 hours
• Subjects who have used the following medications/ treatments from four weeks prior to Baseline visit: corticosteroids and nerve blocks.
• Subjects using any drug which might interact adversely with, or interfere with the action of, the study medication (e.g., carbonic anhydrase inhibitors)
• Subjects who have failed an adequate trial of topiramate for cluster headaches due to lack of efficacy or adverse events, as determined by the investigator
• Subjects with a history of nephrolithiasis.
• Subjects who are allergic to or have shown hypersensitivity topiramate or agents similar to topiramate
• Subjects who abuse opioids as determined by investigator
• Subjects with a history of significant drug or alcohol abuse within the past year
• Subjects who have participated in an investigational drug trial in the 30 days prior to the screening visit