Differential Diagnosis for Headache Disorder Unresponsive to Oxcarbazepine and Gabapentin

Diagnostic Considerations

The American Academy of Neurology suggests that chronic migraine should be the leading diagnosis if a patient experiences ≥15 headache days per month for >3 months, with ≥8 days per month meeting migraine criteria or responding to triptan/ergot treatment 1, 2, 3
The International Headache Society recommends documenting headache frequency, with headaches occurring ≥15 days/month for >3 months 1, 2
The American Headache Society suggests that migraine characteristics on ≥8 days/month should include unilateral location, pulsating quality, moderate-to-severe intensity, and aggravation by routine physical activity 1, 3

The American Academy of Neurology recommends actively screening for medication-overuse headache, which occurs in patients with ≥15 headache days/month who regularly overuse acute medications for >3 months 1, 4
The International Headache Society suggests that triptans, ergots, combination analgesics, and simple analgesics (NSAIDs, acetaminophen) should be assessed for overuse thresholds 1, 4

The American Headache Society recommends implementing a headache diary to document attack frequency, duration, intensity, associated symptoms, and acute medication use over 4 weeks 1, 3, 5
The American Academy of Neurology suggests applying validated screening instruments such as ID-Migraine to identify patients meeting migraine criteria 3

The American Headache Society recommends initiating CGRP monoclonal antibodies (erenumab, fremanezumab, or galcanezumab) as first-line preventive treatment for chronic migraine, which reduce migraine days by 2-4.8 days per month with favorable tolerability 4
The American Academy of Neurology suggests that topiramate is a second-line option with specific evidence in chronic migraine, titrated from 25 mg daily to 100-200 mg daily 4, 5
The International Headache Society recommends withdrawing the overused medication first if medication-overuse headache is present, as preventive therapy will not be effective until overuse is addressed 1, 4

In adults experiencing headaches on ≥15 days per month for more than 3 months, clinicians should first exclude medication‑overuse headache and then confirm chronic migraine before starting preventive therapy【6】【7】.
Chronic migraine is defined by headache on ≥15 days per month for >3 months【6】【7】.
On ≥8 days per month, the headache must fulfill migraine features (unilateral, pulsating, moderate‑to‑severe intensity, aggravated by physical activity, with nausea/vomiting or photophobia/phonophobia) or show a positive response to a triptan/ergot acute treatment【6】【7】.
The patient must have a prior history of at least five attacks that meet migraine‑without‑aura criteria【6】.

MOH is diagnosed when a patient uses triptans, ergot derivatives, or combination analgesics on ≥10 days per month for ≥3 months【6】【7】.
Use of simple analgesics (e.g., NSAIDs, acetaminophen) on ≥15 days per month for ≥3 months also meets criteria for MOH【6】【7】.

To avoid recurrence of MOH, triptans/ergots should be limited to fewer than 10 days per month and simple analgesics to fewer than 15 days per month【6】【7】.
Maintaining optimized acute therapy while adhering to these limits is essential when patients are also on preventive medication【7】.

Chronic migraine is a dynamic condition; patients may revert to episodic migraine but can also transition back to chronic migraine, necessitating ongoing monitoring【6】【7】.
Clinicians should maintain stability of effective treatments and regularly assess for changes that require therapeutic adjustment【7】.
Referral to a headache specialist is recommended for cases that are refractory to standard preventive and acute strategies【7】.

Adults must experience headache on ≥15 days per month for more than 3 consecutive months to meet the definition of chronic migraine. 8
On ≥8 of those days per month, the headache must display migraine‑typical features (unilateral, pulsating, moderate‑to‑severe intensity, aggravated by routine physical activity, accompanied by nausea/vomiting or photophobia/phonophobia) or the attacks must respond positively to triptans or ergot derivatives. 8
The patient should have a prior history of at least five attacks that fulfill the criteria for migraine without aura. 8

MOH is diagnosed when a patient uses triptans, ergot derivatives, or combination analgesics on ≥10 days per month for ≥3 months. 8
MOH is also diagnosed when simple analgesics (e.g., NSAIDs, acetaminophen) are taken on ≥15 days per month for ≥3 months. 8

The target outcome for preventive therapy is a ≥50 % reduction in monthly migraine days compared with baseline. 8

Chronic migraine is a dynamic condition; patients may revert to episodic migraine or re‑transform into chronic migraine, necessitating continuous monitoring and possible treatment adjustments. 8