Diagnosis

Since NDPH is a diagnosis of exclusion, it is important to rule out any other potential causes of persistent headache. This can usually be accomplished by running a fairly standard set of tests and looking at the patient history and exam. If all of these are unremarkable, NDPH is the likely diagnosis.

Diagnosis Criteria

According to the International Classification of Headache Disorders, NDPH "must not be accounted for by another ICHD-3 diagnosis," including chronic migraine, chronic tension headache, or hemicrania continua. The criteria for an NDPH diagnosis are:

Persistent headache, daily from its onset, which is clearly remembered. The pain lacks characteristic features, and may be migraine-like or tension-type-like, or have elements of both.

Persistent headache fulfilling criteria B and C
Distinct and clearly-remembered onset, with pain becoming continuous and unremitting within 24 hours
Present for >3 months
Not better accounted for by another ICHD-3 diagnosis

Tests you should have

MRI of head and cervical spine (with and without contrast)
MRA of head and neck
MRV of head
CT of head
Lumbar puncture/spinal tap
Blood tests (CBC, metabolic panel, thyroid)
Allergy testing
EEG
Doppler of carotid arteries
Sleep study
Sinus x-rays and CT

Doctors to visit to rule out other causes

Primary care doctor/internist
Ear, nose, & throat specialist (ENT)
Dentist/TMJ specialist
Sleep specialist
Ophthalmologist
Neurologist
Psychologist

NDPH Mimics

The list of conditions that can potentially mimic NDPH is obviously too long to list here, but here is a non-exhaustive list of other conditions that can seem like NDPH but aren't. These should be thoroughly investigated and ruled out before making a final NDPH diagnosis:

Chronic migraine
Chronic tension-type headache
Hemicrania continua (responds to indomethacin, with dosing up to 200 mg/day)
Cervicogenic headache/ post-traumatic headache
Medication overuse headache
Occipital neuralgia
Trigeminal neuralgia
Nummular headache
Intranasal contact point headache (see here)
Reversible cerebral vasoconstriction syndrome (RCVS)
Sphenoid sinusitis
Giant cell arteritis
Carotid artery dissection
Brain tumor (especially pituitary, which can refer pain to the top of the head)
Cerebral spinal fluid (CSF) leak
Idiopathic intracranial hypertension/hypotension (CSF pressure issues)
Normal pressure hydrocephalus
Cerebral venous thrombosis
Arteriovenous malformation (AVM)
Unremitting head and neck pain (UHNP) (see here)
Chronic meningitis
Parasite infection

Click here to go to the Causes page under "Other Causes" to learn about other odder, unexpected causes of NDPH.