Differentials
Chronic primary headache disorder
SIGNS / SYMPTOMS
Chronic headache that does not fulfil all the diagnostic criteria for MOH as set out in the 2018 International Classification of Headache Disorders (ICHD-3):[1]
Headache on ≥15 days per month on a background of a pre-existing primary headache disorder.
Regular overuse for >3 months of acute treatments (at any dose) for the pre-existing headache disorder. Overuse is defined by: use of simple analgesics on ≥15 days per month (paracetamol, aspirin, or other non-steroidal anti-inflammatory drug [NSAID], alone or in any combination); or use of a triptan, opioid, or ergot derivative on ≥10 days per month; or use of a combination of analgesics from different classes on ≥10 days per month.
No other ICHD-3 headache diagnosis better accounts for the symptoms.
Note that a diagnosis of chronic migraine or chronic tension-type headache (TTH) also requires headache on ≥15 days per month.[1] If the patient also meets the criteria for MOH, both diagnoses should be given in the first instance. After withdrawal of the overused drug, the diagnosis of the chronic primary headache disorder is only retained if the headache fails to revert to an episodic pattern.[1]
INVESTIGATIONS
Diagnosis is clinical. A headache diary is key for distinguishing different ICHD-3 headache disorders.
Idiopathic intracranial hypertension (pseudotumor cerebri)
SIGNS / SYMPTOMS
Headache type varies substantially between patients but in most cases has a migraine phenotype. Transient visual obscuration, pulsatile tinnitus, or horizontal diplopia. Papilloedema may be present on ophthalmological examination.[46]
INVESTIGATIONS
Brain MRI/magnetic resonance venogram (MRV): usually show transverse sinus stenosis, empty sella, posterior globe flattening, distended optic nerve sheath.
Lumbar puncture at spinal L3/L4: indicates an opening pressure of ≥25 cm H₂O.[47]
Spontaneous intracranial hypotension and/or cerebrospinal fluid (CSF) leak
SIGNS / SYMPTOMS
Orthostatic headache that is relieved by lying down. May have neurological symptoms.
Sphenoid sinusitis
SIGNS / SYMPTOMS
Non-specific frontal/vertex headache.
INVESTIGATIONS
CT sinus: diffuse mucosal thickening, opacification of the affected sinus(es).
Cervicogenic headache
SIGNS / SYMPTOMS
Cervical joint tenderness or reduced range of motion are common but not specific. Cervical flexion rotation can be limited.[49]
Persistent headache attributed to traumatic brain injury/whiplash
SIGNS / SYMPTOMS
Trauma in the history.
INVESTIGATIONS
Diagnosis is usually clinical, based on ICHD-3 criteria.
Brain MRI: may or may not show structural lesion.
Cerebral venous sinus thrombosis
Space-occupying lesion in the brain
SIGNS / SYMPTOMS
Visual change, seizure, cognitive/behaviour change, focal weakness/numbness.[40]
INVESTIGATIONS
MRI brain: shows enhancing or non-enhancing mass with or without perifocal oedema.
Chronic meningitis
SIGNS / SYMPTOMS
Photophobia, meningismus, cranial nerve palsy.
INVESTIGATIONS
Cerebrospinal fluid (CSF) chemistry: shows elevated protein, decreased glucose, elevated white blood cell counts, and positive microbiology/virology test.[53]
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