Sleep disorders, including hypersomnia and obstructive sleep apnea syndrome, are associated with primary headache syndromes. There are no studies of NDPH and sleep apnea. [medscape.com]

Headache and painful lymphadenopathy in extracranial or systemic infection: Etiology of new daily persistent headaches. Intern Med 1993;32:530-3. [ PUBMED ] 25. Stewart WF, Scher AI, Lipton RB. [neurologyindia.com]

[…] has been suggested as a possible trigger for NDPH but a conclusive proof of its cause-to-effect relationship with NDPH is lacking. [21], [22] Other triggers like stressful life events, cervical joint hypermobility, head trauma, other infections like diarrhea [neurologyindia.com]

Reactive arthritis (ReA) is a post-infectious disease entity of synovium/joints with connective tissue membrane (synovial membrane of the joints) which provides a corollary. [en.wikipedia.org]

Some researchers have theorized that both psychiatric symptoms and head pain could be manifestations of a single disorder. [neurologyadvisor.com]

The spectrum of anxiety disorders, particularly panic disorder, should be considered in NDPH patients presenting with psychiatric symptoms. [en.wikipedia.org]

Fundus examination shows papilledema. Perimetry is more sensitive as it may show peripheral constriction of visual fields even before the appearance of papilledema. [neurologyindia.com]

It is however well recognised that papilledema may be absent and the headache may not have any features, raising the suspicion of raised intracranial pressure. [ncbi.nlm.nih.gov]

Coexistence of migraine and idiopathic intracranial hypertension without papilledema. Neurology 1996 ; 46 : 1226 –30. Rosenfeld WE. Topiramate: a review of the preclinical, pharmacokinetic, and clinical data. [jnnp.bmj.com]

[…] subarachnoid hemorrhage idiopathic intracranial hypertension temporal arteritis chronic subdural hematoma post-traumatic headaches sphenoid sinusitis hypertension spontaneous cerebrospinal fluid leak cervical artery dissections pseudotumor cerebri without papilledema [en.wikipedia.org]

The headache can be associated with other neurological signs such as papilledema, focal deficits, seizures, disorders of consciousness, or cranial nerve palsies. [headachejournal.onlinelibrary.wiley.com]

However, the majority of patients eventually develop other features like visual obscurations, seizures, limb weakness or alteration of consciousness. [neurologyindia.com]

"New Daily Persistent Headache As A Presenting Symptom Of Hashimoto's Encephalopathy". Webmed Central. Retrieved 22 December 2012. Neufeld, Miriam Y.; Treves, Therese A.; Chistik, Vladimir; Korczyn, Amos D. (1999). "Postmeningitis Headache". [en.wikipedia.org]

However, the majority of patients eventually develop other features like visual obscurations, seizures, limb weakness or alteration of consciousness. [neurologyindia.com]

[…] mechanisms of the relationship between obstructive sleep apnea and chronic daily headache are not fully understood, but may involve intracranial and arterial pressure fluctuations during snoring in an individual susceptible to pain progression, hypoxia, hypercapnia [medscape.com]