The most important initial investigation is computed tomography of the brain, which is very sensitive for subarachnoid hemorrhage. If this is normal, a lumbar puncture is performed, as a small proportion of SAH is missed on CT and can still be detected as xanthochromia.

If both investigations are normal, the specific description of the headache and the presence of other abnormalities may prompt further tests, usually involving magnetic resonance imaging (MRI). Magnetic resonance angiography (MRA) may be useful in identifying problems with the arteries (such as dissection), and magnetic resonance venography (MRV) identifies venous thrombosis. It is not usually necessary to proceed to cerebral angiography, a more precise but invasive investigation of the brain's blood vessels, if MRA and MRV are normal.

A lumbar puncture is a procedure in which cerebral spinal fluid is removed from the spine with a needle. A lumbar puncture is necessary to look for infection or blood in the spinal fluid. A lumbar puncture can also evaluate the pressure in the spinal column, which can be useful for people with idiopathic intracranial hypertension (usually young, obese women who have increased intracranial pressure), or other causes of increased intracranial pressure. In most cases, a CT scan should be done first.

All people who present with red flags indicating a dangerous secondary headache should receive neuroimaging. The best form of neuroimaging for these headaches is controversial. Non-contrast computerized tomography (CT) scan is usually the first step in head imaging as it is readily available in Emergency Departments and hospitals and is cheaper than MRI. Non-contrast CT is best for identifying an acute head bleed. Magnetic Resonance Imaging (MRI) is best for brain tumors and problems in the posterior fossa, or back of the brain. MRI is more sensitive for identifying intracranial problems, however it can pick up brain abnormalities that are not relevant to the person's headaches.

The American College of Radiology recommends the following imaging tests for different specific situations:

Cluster headaches are often misdiagnosed, mismanaged, or undiagnosed for many years; they may be confused with migraine, "cluster-like" headache (or mimics), CH subtypes, other TACs ( trigeminal autonomic cephalalgias), or other types of primary or secondary headache syndrome. Cluster-like head pain may be diagnosed as secondary headache rather than cluster headache.

A detailed oral history aids practitioners in correct differential diagnosis, as there are no confirmatory tests for CH. A headache diary can be useful in tracking when and where pain occurs, how severe it is, and how long the pain lasts. A record of coping strategies used may help distinguish between headache type; data on frequency, severity and duration of headache attacks are a necessary tool for initial and correct differential diagnosis in headache conditions.

Correct diagnosis presents a challenge as the first CH attack may present where staff are not trained in the diagnosis of rare or complex chronic disease. Although experienced ER staff are sometimes trained to detect headache types, CH attacks themselves are not directly life-threatening, they are linked to an increased risk of suicide.

Individuals with CH typically experience diagnostic delay before correct diagnosis. People are often misdiagnosed due to reported neck, tooth, jaw, and sinus symptoms and may unnecessarily endure many years of referral to ear, nose and throat (ENT) specialists for investigation of sinuses; dentists for tooth assessment; chiropractors and manipulative therapists for treatment; or psychiatrists, psychologists and other medical disciplines before their headaches are correctly diagnosed. Under-recognition of CH by health care professionals is reflected in consistent findings in Europe and the United States that the average time to diagnosis is around seven years. Medical students receive little training in differential diagnoses and management of headaches.

Cluster headache may be misdiagnosed as migraine or sinusitis. Other types of headache are sometimes mistaken for, or may mimic closely, CH. Incorrect terms like "cluster migraine" confuse headache types, confound differential diagnosis and are often the cause of unnecessary diagnostic delay, ultimately delaying appropriate specialist treatment.

Headaches that may be confused with CH include:

- Chronic paroxysmal hemicrania (CPH) is a unilateral headache condition, without the male predominance usually seen in CH. Paroxysmal hemicrania may also be episodic but the episodes of pain seen in CPH are usually shorter than those seen with cluster headaches. CPH typically responds "absolutely" to treatment with the anti-inflammatory drug indomethacin where in most cases CH typically shows no positive indomethacin response, making "Indomethacin response" an important diagnostic tool for specialist practitioners seeking correct differential diagnosis between the conditions.

- Short-lasting unilateral neuralgiform headache with conjunctival injection and tearing (SUNCT) is a headache syndrome belonging to the group of TACs.

- Trigeminal neuralgia is a unilateral headache syndrome, or "cluster-like" headache.

As of 2013 tension headaches affect about 1.6 billion people (20.8% of the population) and are more common in women than men (23% to 18% respectively). Despite its benign character, tension-type headache, especially in its chronic form, can impart significant disability on patients as well as burden on society at large.

Although NDPH is classified as a primary headache syndrome, it must be remembered that a number of important conditions can present with a new-onset persisting headache, and these must be excluded prior to making a diagnosis of a primary headache disorder.

The diagnosis is one of excluding the many secondary types or NDPH mimics, which is especially critical early in the course of the disease when a secondary etiology is more likely. NDPH mimics include but are not limited to:

- neoplasms

- 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

- cerebral venous thrombosis

- Chiari malformation

- NDPH with medication overuse headache

Many doctors state that the condition is best viewed as a syndrome rather than a diagnosis. Once a diagnosis of NDPH is made, clinicians argue that patients are best managed according to the more detailed pathophysiology-based diagnosis than lumped together into a single group, since a single disorder is unlikely to exist.

NDPH It is classified as a Primary Headache Disorder by the ICHD-2 classification system (by the IHS) using number 4.8. It is one of the types of primary headache syndromes that present as a chronic daily headache, which is a headache present for more than 15 days a month for more than 3 months.

The importance of severe headaches in the diagnosis of subarachnoid hemorrhage has been known since the 1920s, when London neurologist Charles Symonds described the clinical syndrome. The term "thunderclap headache" was introduced in 1986 in a report by John Day and Neil Raskin, neurologists at the University of California, San Francisco, in a report of a 42-year-old woman who had experienced several sudden headaches and was found to have an aneurysm that had not ruptured.

Most patients have persistent headaches, although about 15% will remit, and 8% will have a relapsing-remitting type. It is not infrequent for NDPH to be an intractable headache disorder that is unresponsive to standard headache therapies.

Tension headaches that do not occur as a symptom of another condition may be painful, but are not harmful. It is usually possible to receive relief through treatment. Tension headaches that occur as a symptom of another condition are usually relieved when the underlying condition is treated. Frequent use of pain medications in patients with tension-type headache may lead to the development of medication overuse headache or rebound headache.

Though outwardly similar to cluster headaches, chronic paroxysmal hemicrania is rather different, and the two headaches are not a subset of one or the other. Key differences include:

- Different gender distributions – CPH is more common in women than men, with opposite occurring with cluster headaches.

- CPH attacks occur more frequently, but are shorter.

- Individuals with CPH are far more responsive to indomethacin than individuals with cluster headaches.

- CPH attacks can be provoked by neck movement.

- In a study conducted by Sjaastad, heating a patient's body will cause the painful side of the forehead to sweat more in CPH patients, while there will be less sweating on that side for those suffering from cluster headaches.

A ten-patient study conducted by Pareja et al. found that all patients diagnosed with CPH were responsive to indomethacin and were able to completely control their symptoms. Doses of the drug ranged from 25 mg per day to 150 mg per day with a median dose of 75 mg per 24-hour period.

Almost all cases of CPH respond positively and effectively to indometacin, but as much as 25 percent of patients discontinued use of the drug due to adverse side effects, namely complications in the gastrointestinal tract.

According to a case study by Milanlioglu et al., 100mg of lamotrigine, an antiepileptic drug, administered twice daily alleviated all painful symptoms. No side effects were noted after two months of treatment. Dosage of lamotrigine was decreased to 50mg a day after the first two months, and no symptoms or side-effects were recorded after a three-month followup.

Use of topiramate has also been found to be an effective treatment for CPH, but cluster headache medications have been found to have little effect.

Long term prognosis in people with migraines is variable. Most people with migraines have periods of lost productivity due to their disease; however typically the condition is fairly benign and is not associated with an increased risk of death. There are four main patterns to the disease: symptoms can resolve completely, symptoms can continue but become gradually less with time, symptoms may continue at the same frequency and severity, or attacks may become worse and more frequent.

Migraines with aura appear to be a risk factor for ischemic stroke doubling the risk. Being a young adult, being female, using hormonal birth control, and smoking further increases this risk. There also appears to be an association with cervical artery dissection. Migraines without aura do not appear to be a factor. The relationship with heart problems is inconclusive with a single study supporting an association. Overall however migraines do not appear to increase the risk of death from stroke or heart disease. Preventative therapy of migraines in those with migraines with auras may prevent associated strokes. People with migraines, particularly women, may develop higher than average numbers of white matter brain lesions of unclear significance.

Prenatal screening is not typically done for FHM, however it may be performed if requested. As penetrance is high, individuals found to carry mutations should be expected to develop signs of FHM at some point in life.

MAV is not recognized as a distinct diagnostic entity. Lembert and Neuhauser propose criteria for definite and probable migraine-associated vertigo.

A diagnosis of "definite migraine-associated vertigo" includes a case history of:

- episodic vestibular symptoms of at least moderate severity;

- current or previous history of migraine according to the 2004 "International Classification of Headache Disorders";

- one of the following migrainous symptoms during two or more attacks of vertigo: migrainous headache, photophobia, phonophobia, visual or other auras; and

- other causes ruled out by appropriate investigations.

A diagnosis of "probable migraine-associated vertigo" includes a case history of episodic vestibular symptoms of at least moderate severity and one of the following:

- current or previous history of migraine according to the 2004 "International Classification of Headache Disorders";

- migrainous symptoms during vestibular symptoms;

- migraine precipitants of vertigo in more than 50% of attacks, such as food triggers, sleep irregularities, or hormonal change;

- response to migraine medications in more than 50% of attacks; and

- other causes ruled out by appropriate investigations.

Note that, in both of the above criteria, headache is not required to make the diagnosis of migraine-associated vertigo.

They add that, in patients with a clear-cut history, no vestibular tests are required. Other historical criteria which are helpful in making the diagnosis of migraine-associated vertigo are vertiginous symptoms throughout the patient’s entire life, a long history of motion intolerance, sensitivity to environmental stimuli, illusions of motion of the environment, and vertigo that awakens the patient.

Treatment of migraine-associated vertigo is the same as the treatment for migraine in general.

As diagnostic criteria have been indecisive and its pathophysiology remains unclear, no permanent cure is available. Antiepileptic medications (membrane-stabilizing drugs) such as pregabalin, gabapentin, topiramate, and lamotrigine improve symptoms, but there is no effective permanent or long-term treatment for SUNCT.

However, a few short-term treatments are available and can relieve and possibly prevent some symptoms of attacks.

Lamotrigine exhibits some long-term prevention and reduction in many patients; however, titration of dose is difficult due to adverse skin reactions.

Topiramate also has preventive effects but it is accompanied by a high risk of severe side-effects for patients with a history of kidney stones, glaucoma, depression, or low body weight.

Intravenous lidocaine can abolish symptoms during its administration, or reduce frequency and duration of attacks. However, administration of intravenous lidocaine requires careful monitoring of ECG and blood pressure.

Methylprednisolone therapy shows some promise in short-term prevention of attacks, even though its mechanism of action is yet to be discovered.

The calcium channel blocker verapamil is reported to be useful in alleviating symptoms (lower frequency and duration of attacks), even though some patients experience worsened symptoms.

Various medications that are often used in other headache syndromes such as nonsteroidal anti-inflammatory drugs, acetaminophen, tricyclic antidepressants, calcium channel antagonists do not relieve the symptoms of SUNCT.

There have been attempts to alter oxygen supply during attacks to alleviate the symptoms since some of the headaches are caused by decreased oxygen supply; however, elevated blood oxygen level did not affect the symptoms.

Researchers now focus on the administration of various combination of medications and therapies to treat symptoms of SUNCT.

"See the equivalent section in the main migraine article."

People with FHM are encouraged to avoid activities that may trigger their attacks. Minor head trauma is a common attack precipitant, so FHM sufferers should avoid contact sports. Acetazolamide or standard drugs are often used to treat attacks, though those leading to vasoconstriction should be avoided due to the risk of stroke.

SUNCT must be properly distinguished from cluster headaches, since cluster headaches also occur several times per day with separate attacks, and share some common symptoms. However, cluster headaches usually last longer (up to three hours), occur less often (three to five attacks per day), and do not accompany cranial autonomic symptoms. IHS standard criteria for the diagnosis of SUNCT specifically includes pain in the trigeminal division of the face, especially in the orbital region, often with cranial autonomic symptoms which last for relatively short periods of time (from five seconds to several minutes) up to 100 times per day. SUNCT is a major subset of SUNA, which does not accompany cranial symptoms; complete separation between the two is inappropriate since SUNCT does not necessarily always accompany cranial autonomic signs. Exact statistical data is not available due to common mis-diagnosis, and setting up diagnostic criteria is important.

The International Headache Classification established by the International Headache Society criteria for diagnosing SUNCT for therapeutic purposes is:

Symptoms of SUNCT often lead to misdiagnosis as paroxysmal hemicrania, which is also categorized in the same group. Inefficiency of indomethacin usually indicates SUNCT over paroxysmal hemicrania.

Misdiagnosis and indecisive diagnosis in the past has made it difficult to obtain accurate statistics about SUNCT. Proper diagnosis will broaden data availability and facilitate discovery of new treatment options and useful statistics.

Preventive treatments of migraines include medications, nutritional supplements, lifestyle alterations, and surgery. Prevention is recommended in those who have headaches more than two days a week, cannot tolerate the medications used to treat acute attacks, or those with severe attacks that are not easily controlled.

The goal is to reduce the frequency, painfulness, and/or duration of migraines, and to increase the effectiveness of abortive therapy. Another reason for prevention is to avoid medication overuse headache. This is a common problem and can result in chronic daily headache.

A vascular headache is an outdated term to describe certain types of headache which were thought to be related to blood vessel swelling and hyperemia as cause of pain.

There is no doubt that "some" headaches are caused by vascular effects. However, it is no longer a recognized term and not mentioned in the Headache classification of the International Headache society (IHS), although it is still used by some physicians and still mentioned in some medical classification systems. There are many types of vascular headaches. Other types of vascular headaches include headaches produced by fever, cluster headaches, and headaches from a rise in blood pressure (OSU Wexner Medical Center, 2012).

Headaches that were described as being vascular headaches include:

- Cluster headache

- Migraine

- Toxic headache

Hemicrania continua generally responds only to indomethacin 25–300 mg daily, which must be continued long term. Unfortunately, gastrointestinal side effects are a common problem with indomethacin, which may require additional acid-suppression therapy to control.

In patients who are unable to tolerate indomethacin, the use of celecoxib 400–800 mg per day (Celebrex) and rofecoxib 50 mg per day (Vioxx - no longer available) have both been shown to be effective and are likely to be associated with fewer GI side effects. There have also been reports of two patients who were successfully managed with topiramate 100–200 mg per day (Topamax) although side effects with this treatment can also prove problematic.

Greater Occipital Nerve [GON] block comprising 40 mg Depomedrone and 10mls of 1% Lignocaine injected into the affected nerve is effective, up to a period of approximately three months. Changing the 'cocktail' to include [for example] 10mls of .5% Marcaine and changing to 2% Lignocaine, whilst in theory should increase the longevity, renders the injection completely ineffective. See 4.2 Posology and method of administration [flocculation]

Occipital nerve stimulation may be highly effective when other treatments fail to relieve the intractable pain.

The prevention and treatment of acephalgic migraine is broadly the same as for classical migraine, but the symptoms are usually less severe than those of classic migraine, so treatment is less likely to be required.

The following diagnostic criteria are given for hemicrania continua:

1. Headache for more than 3 months fulfilling other 3 criteria:

2. All of the following characteristics:

- Unilateral pain without side-shift

- Daily and continuous, without pain-free periods

- Moderate intensity, but with exacerbations of severe pain

3. At least one of the following autonomic features occurs during exacerbations and ipsilateral to the side of pain:

- Conjunctival injection and/or lacrimation

- Nasal congestion and/or rhinorrhea

- Ptosis and/or miosis

4. Complete response to therapeutic doses of indomethacin, although cases of hemicrania continua that do not resolve with indomethacin treatment have been documented.

A variant on hemicrania continua has also been described, in which the attacks may shift sides, although meeting the above criteria in all other respects.

Main features differentiating CPH from cluster headaches (migrainous neuralgia, above) are the higher frequency and shorter duration of attacks, higher incidence in women, and the response to treatment with indomethacin. CPH is not associated with cranial nerve palsies.

The clinician should first rule out conditions with similar symptoms, such as subarachnoid hemorrhage, ischemic stroke, pituitary apoplexy, cerebral artery dissection, meningitis, and spontaneous cerebrospinal fluid leak. This may involve a CT scan, lumbar puncture, MRI, and other tests. Posterior reversible encephalopathy syndrome has a similar presentation, and is found in 10–38% of RCVS patients.

RCVS is diagnosed by detecting diffuse reversible cerebral vasoconstriction. Catheter angiography is ideal, but computed tomography angiography and magnetic resonance angiography can identify about 70% of cases. Multiple angiographies may be necessary. Because other diseases (such as atherosclerosis) have similar angiographic presentations, it can only be conclusively diagnosed if vasoconstriction resolves within 12 weeks.