Migraine headache
Tension headache
Cluster headache
Meningitis/encephalitis
Neoplastic meningitis
Myocardial ischemia
Retropharyngeal abscess
Intracranial Hemorrhage (ICH)
SAH / sentinel bleed
Acute obstructive hydrocephalus
Space occupying lesions
CVA
Carbon monoxide poisoning
Basilar artery dissection
Preeclampsia
Cerebral venous thrombosis
Hypertensive emergency
Depression
Neoplastic meningitis
SAH / sentinel bleed
Giant cell arteritis of temporal artery (temporal arteritis)
Idiopathic intracranial hypertension (Pseudotumor Cerebri)
Acute Glaucoma
Acute sinusitis
Cavernous sinus thrombosis or cerebral sinus thrombosis
Carotid artery dissection<unk> 
TMJ pain
Post-lumbar puncture headache
Dehydration
Analgesia abuse
Various ocular and dental problems
Herpes zoster ophthalmicus
Herpes zoster oticus
Cryptococcosis
Febrile headache (e.g. pyelonephritis, nonspecific viral infection)
Ophthalmoplegic migraine
Superior Vena Cava Syndrome
Viral
Varicella
Herpes
Enterovirus
West Nile
Tuberculosis
Lyme disease
Syphilis
Leptospirosis
Fungal (AIDS, transplant, chemotherapy, chronic steroid use)
Noninfectious
Sarcoidosis
Vasculitis
Connective tissue disease
Drug induced aseptic meningitis
Varicella
Herpes
Enterovirus
West Nile
Sarcoidosis
Vasculitis
Connective tissue disease
Drug induced aseptic meningitis
Bell's palsy
CVA<unk> 
Tick paralysis
Lyme disease
Herpes zoster oticus (Ramsay Hunt syndrome)
CNS tumor
Acoustic neuroma or other cerebellopontine angle lesions
Meningioma
Cerebellar pontine angle
Facial nerve schwannoma
Parotid
Sarcoma
Anesthesia nerve blocks
Cerebral Aneurysms (vertebral, basilar, or carotid)
Lyme disease
Acoustic neuroma or other cerebellopontine angle lesions
Meningioma
Cerebellar pontine angle
Facial nerve schwannoma
Parotid
Sarcoma
Trigeminal neuralgia
Migraine headache
Tension headache
Cluster headache
Meningitis/encephalitis
Post-lumbar puncture headache
Neoplastic meningitis
Heat syncope