Right-Sided Head Pain in NMOSD
Yes, right-sided head pain can be an initial presenting symptom of NMOSD, and clinicians should maintain a high index of suspicion for NMOSD when evaluating patients with unilateral headache, particularly when accompanied by visual symptoms or other neurological findings. 1
Clinical Evidence for Headache as NMOSD Presentation
Headache can precede classic NMOSD manifestations by weeks to months. A documented case demonstrated right-sided periorbital headache preceding visual field disturbances by 2 months in a patient ultimately diagnosed with aquaporin-4 antibody-positive NMOSD. 1 This case specifically involved headache around the right upper eyelid that was followed by diminished light reflex and inferior horizontal hemianopsia in the right eye. 1
Another case report documented NMOSD being initially misdiagnosed as cervicogenic headache, highlighting the diagnostic challenge when headache is the predominant symptom. 2
Mechanism of Headache in NMOSD
The headache in NMOSD likely relates to:
- Optic nerve inflammation and swelling, which can cause periorbital pain through involvement of the trigeminal nerve pathways that innervate the ocular surface and periorbital structures 3
- Area postrema involvement, which is a classic NMOSD presentation that can manifest with intractable vomiting and hiccoughs, potentially accompanied by headache 4, 5
Red Flags Suggesting NMOSD Rather Than Primary Headache
When evaluating unilateral headache, consider NMOSD if any of the following are present:
- Periorbital location with subsequent visual symptoms (diminished light reflex, visual field defects, color desaturation) 1, 6
- MRI findings showing optic nerve enlargement, T2 hyperintensity in the superior optic nerve, or enhancement 1
- Brain lesions in characteristic NMOSD locations: corpus callosum (cloud-like, poorly marginated), diencephalic regions, or area postrema 7
- Bilateral simultaneous optic nerve involvement or posterior optic nerve/chiasm involvement 6, 7
- Longitudinally extensive spinal cord lesions (≥3 vertebral segments) if myelitis symptoms develop 8, 7
Diagnostic Approach When Headache Raises NMOSD Concern
Immediately obtain MRI of orbits and brain with contrast to evaluate for optic nerve inflammation and characteristic brain lesions. 6 The imaging should specifically assess for:
- Optic nerve T2 hyperintensity, swelling, and gadolinium enhancement 6
- Long optic nerve lesions (>6/12 segments or involving ≥4/5 segments) 3
- Brain lesions nondiagnostic for MS but suggestive of NMOSD 7
Test serum for AQP4-IgG and MOG-IgG antibodies in parallel when atypical presentations occur, as these have significant therapeutic consequences. 6 AQP4-IgG is 76% sensitive and 94% specific for NMOSD. 7
Critical Clinical Pitfall
Do not dismiss unilateral periorbital headache as benign primary headache or cervicogenic headache without considering NMOSD, especially if the headache is persistent despite treatment or accompanied by any visual symptoms. 2, 1 Early diagnosis is essential because untreated NMOSD leads to severe disability—approximately 50% of patients become wheelchair users and blind, with one-third dying within 5 years of first attack. 4