When should a separate diagnosis of headache be considered in a case of bodily distress disorder as per ICD-11 (International Classification of Diseases, 11th revision)?

When to Diagnose Headache Separately in Bodily Distress Disorder (ICD-11)

Diagnose headache as a separate condition when it meets full diagnostic criteria for a primary headache disorder (migraine, tension-type headache, or cluster headache) with specific frequency, duration, and characteristic features that warrant independent treatment, even in the presence of bodily distress disorder.

Understanding the Diagnostic Framework

The key distinction lies in whether the headache constitutes a diagnosable primary headache disorder versus being one of multiple somatic symptoms within bodily distress disorder. Bodily distress disorder encompasses patients with multiple functional somatic symptoms across different organ systems, with headache being one potential manifestation among many 1.

Criteria for Separate Headache Diagnosis

Migraine Without Aura

Assign a separate migraine diagnosis when the patient has:

• At least 5 attacks meeting specific criteria 2, 3
• Duration of 4-72 hours (untreated or unsuccessfully treated) 2, 3
• At least two of: unilateral location, pulsating quality, moderate-to-severe intensity, aggravation by routine physical activity 2, 3
• At least one of: nausea/vomiting OR both photophobia and phonophobia together 2, 3

Chronic Migraine

Warrant separate diagnosis when:

• Headache occurs ≥15 days/month for >3 months 2, 3
• On ≥8 days/month, headache meets migraine criteria or responds to triptan/ergot treatment 2, 3
• Prior history of at least 5 attacks meeting migraine without aura criteria 2, 3

This is critical because chronic migraine carries substantially greater disability and requires specific prophylactic treatment beyond what bodily distress disorder management would provide 4.

Tension-Type Headache

Consider separate diagnosis when:

• Bilateral location with pressing/tightening quality 4
• Mild to moderate intensity not aggravated by routine physical activity 4
• Lacks migraine-associated symptoms (no nausea, only one of photophobia/phonophobia) 4

Clinical Approach to Differentiation

Use Diagnostic Tools

• Implement headache diaries to document attack frequency, duration, intensity, associated symptoms, and medication use—this objective data is essential for distinguishing a primary headache disorder from diffuse somatic complaints 4, 2, 5
• Apply validated screening instruments such as ID-Migraine (sensitivity 0.81, specificity 0.75) or MS-Q (sensitivity 0.93, specificity 0.81) to identify patients likely meeting migraine criteria 4

Assess for Treatment-Relevant Features

The decision to diagnose separately should be influenced by whether the headache:

• Causes significant disability (inability to work, attend social functions, perform routine activities) that exceeds the general functional impairment from bodily distress disorder 4
• Requires migraine-specific treatment such as triptans for acute attacks or prophylactic medications (topiramate, which has proven efficacy in chronic migraine) 4
• Demonstrates clear episodic pattern with discrete attacks rather than continuous, vague head discomfort 4

Rule Out Secondary Causes First

Before assigning either diagnosis, exclude secondary headache disorders by evaluating for red flags 4, 6:

• Thunderclap headache, atypical aura, recent head trauma in history 4
• Unexplained fever, impaired memory, focal neurological symptoms on examination 4
• New-onset headache in patients >50 years (consider temporal arteritis, neoplasm, subdural hematoma) 7

Neuroimaging is indicated only when red flags are present, not for routine diagnosis 4.

Key Clinical Pitfalls

Frequency and Disability Matter More Than Severity

Frequent headache (>4 days/week) and frequent disability (>3 days/week with reduced activities) correlate strongly with depression, anxiety, and impaired quality of life, whereas reported severity alone does not 8. This means:

• A patient reporting "severe" headaches infrequently may not warrant separate diagnosis
• A patient with moderate but frequent headaches causing regular disability likely does warrant separate diagnosis and specific headache management 8

Bodily Distress Disorder Context

Research shows that patients with bodily distress disorder report a median of 5 functional somatic symptoms, with symptoms clustering into cardiopulmonary, musculoskeletal, and gastrointestinal groups 1. Headache in this context is often one manifestation of a broader pattern rather than a distinct primary headache disorder 1.

The "Probable Migraine" Category

When a patient has fewer than 5 qualifying attacks but otherwise meets criteria, use "probable migraine" coding and reassess during follow-up before committing to a separate diagnosis 5, 3.

Practical Algorithm

1. Document headache characteristics systematically using ICHD-3 criteria as a checklist 2, 5
2. Count qualifying attacks over the past 3 months using prospective diary data 4, 2
3. If ≥5 attacks meet full migraine criteria OR headache occurs ≥15 days/month with ≥8 migraine days, assign separate migraine diagnosis 2, 3
4. If headache is one of multiple somatic symptoms without meeting primary headache criteria, consider it part of bodily distress disorder 1
5. Reassess periodically, as chronic migraine is not static and patients may transition between episodic and chronic patterns 2

Treatment Implications Drive the Decision

The fundamental reason to diagnose separately is that primary headache disorders require specific interventions (triptans, prophylactic medications like topiramate) that differ from the stress management and psychological approaches central to bodily distress disorder treatment 4, 1. When headache meets criteria for a primary disorder and causes independent disability, it warrants both diagnostic recognition and targeted treatment.