What are Headaches?

Headaches are a very common problem, with as much as 15% of the U.S. population suffering from recurring headaches. Headaches are described as a pain above the shoulders, in the upper neck, the base of the skull, the head, or face. This pain may be generalized in these regions or it may affect a specific area. Severe headaches may also be associated with other physiological symptoms, ranging from nausea to light-sensitivity. Recurring, or chronic, headaches cause ongoing pain and discomfort, sometimes beginning with an extremely sharp, stabbing, acute pain that may begin suddenly. Some headaches may be episodic, occurring consistently at certain times, while others are difficult to predict.

Although headaches often feel as though they are originating from deep within the brain, the brain itself does not contain any pain receptors. This means that the pain is not physically originating from inside the brain. The source of the pain is some form of damage to the surrounding structures, such as the skull, blood vessels, subcutaneous tissues, muscles, nerves, cavities (such as sinuses), or sensory organs such as the eyes or ears. This could result from an injury, disease, or inflammation of these tissues. When the nerve cells that sense pain receive this information, the brain interprets the pain as being within the brain. Headaches can range from an annoyance or distraction to a debilitating pain that interferes with daily activity and quality of life.

Must Watch Video – What are Headaches?

Headaches are classified by a number of factors. Headaches without an underlying cause (e.g., trauma or physical damage) are referred to as primary headaches.

Migraine Headaches

Migraine headaches are the most common form of primary headache. They typically have a single source or cause, although the root cause is not always readily identifiable. Although anyone can get migraine headaches, women are at a three-fold higher risk than men. This is primarily due to chronic migraine pain associated with the menstrual cycle. For women with this type of migraine, the cause is known and the onset may be predictable.

Migraine headaches are often recurring and associated with severe, intense, throbbing pain. This pain is often felt near the eyes, primarily concentrated on one side, but it may also spread to the face or head. Associated symptoms include sensory sensitivity, particularly with regard to light, sounds, and scents. The intense pain may be associated with nausea and vomiting.

The symptoms associated with migraine headaches may pass within a few hours or can persist for several days, depending on the individual and on treatment. Typically, there is a progression of these symptoms through four characterized phases.

  1. The first phase is the prodrome phase. This phase precedes the pain and can be associated with mental and emotional changes, food cravings, drowsiness, frequent urges to use the restroom, thirst, or irritability.
  2. The second phase is the aura phase. This phase is associated with neurological symptoms or an aura shortly before the onset of pain. Not all migraine sufferers experience auras, which can range from the appearance of lights to blind spots or tunnel vision.
  3. The third phase is the attack phase. This is the phase most strongly associated with pain as well as the symptoms mentioned above. Depending on treatment, this phase may last from a few hours up to three days.
  4. The fourth and final phase is the postdrome phase. This phase occurs after the previous migraine symptoms have subsided. The feelings associated with this phase vary greatly between individuals, with some people reporting feelings of fatigue and others reporting mild euphoria.

Migraine pain is not typically indicative of a more serious disease or illness, but it is still important to monitor your symptoms. In the event of sudden increases in severity, it may be necessary to consult a physician.

Cluster-Type Headaches

The pain associated with cluster headaches is similar to the pain of migraines in that it is often felt near the eyes, concentrated on one side of the head. However, each individual headache of a cluster headache typically resolves much faster than migraines, with symptoms often lasting no more than a couple of hours at a time. Despite this, they can occur up to eight times a day and patients report the pain as being the most intense they have experienced. Associated symptoms include light sensitivity, nasal congestion, and watery eyes. This type of headache affects approximately 0.01% of individuals.

Tension-Type Headaches

The pain associated with tension-type headaches is typically felt near the front or back of the head. They are often more regular in occurrence, with the onset and resolution occurring at certain times of the day. They may be chronic in nature, sometimes occurring for several days at a time. The pain of a tension headache is often described as extreme pressure around the head, and they may be associated with sensory sensitivities, particularly to light and sound.

Although often milder than other types of headaches, episodic tension headaches may be equally disruptive due to their frequency. Episodic tension headaches may last anywhere from 30 minutes up to 15 days. They are often associated with irritability, loss of focus or concentration, and heightened sensitivities to stimuli, which may also serve as a trigger for this type of headache. Approximately 3% of individuals experience tension headaches.

Secondary Headaches

Any of the types of headaches listed can occur as a secondary headache. Secondary headaches are characterized as symptoms of an underlying condition or they could be a side effect resulting from some form of treatment. Medical conditions such as fibromyalgia and arthritis can be causes of secondary headaches. Secondary headaches are typically not caused by serious or life-threatening conditions. If a patient has experienced similar headaches in the past, then the risk of underlying problems is low. However, as with any condition, they should be closely monitored and any changes may need to be assessed by a physician. In particular, pain that is much more severe than usual or unusual in any way may be cause for concern. If this is the case, your physician may need to rule out any potentially severe conditions.

The onset of a headache associated aura, in a patient typically not experiencing auras, may be indicative of a more serious underlying condition. Auras may appear visually as lines across the field of vision or as various disturbances to speech, sensory perception, or motor skills. If the headache seems to be the result of any form of exertion (coughing, heavy lifting, or sexual intercourse), then it could be related to a vascular condition such as stroke or embolism. Any pain associated with a change in personality or mental state should be carefully monitored and followed up by a physician. If the pain is associated with soreness or tenderness around the temples, it could be a symptom of an aneurysm. If the pain is concurrent with a sore or stiff neck and a fever or rash, it could be a sign of meningitis. While many of these symptoms may occur without any underlying complications, these combinations may be signs that there is a more serious underlying condition and should be assessed by your physician.

The leading driver for over-the-counter pain medication, including acetaminophen and NSAIDs (e.g., aspirin and ibuprofen), is headaches. However, certain types of headaches are resistant to over-the-counter medications, such as chronic and episodic headaches. Regardless of treatment method, whether treated at home or by a physician, the healthcare cost of headaches is significant.

Causes And Pathophysiology Of Headaches

The pain associated with headaches is transmitted by the nerves radiating out of the brain through the membranes in the skull. Sometimes this pain may result from inflammation or irritation of the nerves or from some form of injury. This sort of damage may cause chronic or recurring headaches. As mentioned above, headaches can be divided into two categories, primary and secondary. Primary headaches result from direct damage to the nerves in the head, while secondary headaches are caused by damage elsewhere in the body or by some other causative injury or illness. Certain headaches, referred to as idiopathic headaches, do not have any clear distinguishable cause.

Headaches originating from the occipital nerve may occur at the top of the neck or base of the skull. The trigemino-cervical complex is a network of nerves that is responsible for many migraine headaches. It can also be the origin of other migraine symptoms such as an aversion to sound (sonophobia) or an aversion to light (photophobia) as well as extreme episodic pain. In particular, episodic migraines can be associated with damage to this nerve. Although the mechanism of damage is often different, cluster headaches can also be traced to the trigemino-cervical nerve complex.

Another possible source of headaches, particularly cluster headaches, may be attributed to the sphenopalatine ganglion, a group of nerve endings in the skull. The pain associated with this cluster of nerves is often referred to as sinus headaches, due to the pain being localized to the nasal area.

Eyestrain, anxiety, stress, and hunger are common factors associated with tension headaches. Other physiological factors that can contribute to tension headaches include sleep deprivation and jaw problems, such as teeth grinding or clenching. As such, tension headaches are not associated with a specific cluster of nerves and it could be linked to the trigeminal, occipital, or sphenopalatine nerves. The associated nerve cluster for tension headaches depends on the muscle group undergoing extreme strain leading to the headache.

Risk Factors

Many of the symptoms associated with headaches may also be risk factors that lead to the development of the headache. Tension headaches, for example, can result from stress, eye strain or other visual stresses, or sleep loss. Inflammation may also lead to physical stress or damage to tissue and nerves. Many other factors can also lead to inflammation-related injury, such as autoimmune disorders and illness.

One disease that can lead to nerve damage is cancer. A growing tumor can put pressure on various nerves and nerve bundles, causing headaches. Cancer treatments can also be very damaging to surrounding tissues, leading to additional stress or damage to nerves. This damage may also lead to acute or chronic pain such as headaches, depending on the area being treated.

There are several other common factors that can lead to headaches. Many people experience headaches as a result of hunger or as a symptom of dehydration. Many drugs may also lead to headaches, including caffeine or other drugs following overuse. Psychological factors can lead to migraines as well, such as depression. Headaches associated with depression may not always be directly resulting from the depression itself, as the stress and anxiety resulting from chronic migraines may also lead to depression in some patients.

Diagnostic Methods For Headaches

Primary headaches, including migraines, can be diagnosed based on a description of the symptoms by the patient and a careful analysis by a physician. The physician can then rate the symptoms to diagnose the headache or even use imaging, such as MRI, to better characterize the headache.

If the headache is found to have originated at a specific nerve or nerve cluster, it may be possible to treat the pain at its source. Such anesthetic medications may be administered by numbing the area with a topical anesthetic followed by a needle injection into the problem tissue. These treatments, referred to as nerve blocks, may be performed using a variety of anesthetic medications, including anti-inflammatory steroids or local anesthetics such as lidocaine.

Direct Nerve Treatments

Some headaches do not respond to initial treatments such as those mentioned above. In this case, radiofrequency ablation (RFA) is another treatment option for the affected nerves. In RFA therapy, very narrow probes are inserted near the location of the affected nerve. The radiofrequency applied to the area generates heat to disrupt the nerve activity and block the pain signals that it had been sending to the brain. Sphenopalatine ganglion or SPG ablation is another treatment option for chronic sinus headaches, while RFA may be as effective as nerve blocks for certain types of headaches, such as those affecting the occipital nerve.

Another treatment option involves small, wire-like implants placed along the spine to target the nerves associated with the pain, such as the nerves that make up the trigemino-cervical complex. This type of treatment is referred to as spinal cord stimulation, or SCS. The implants are attached to wires that deliver a small electrical stimulation via a controller. The electrical stimulation interferes with the nerve signaling, preventing the brain from receiving the pain signals. SCS treatment is primarily effective for migraine-related pain.

Alternative Or Complementary Treatments

Depending on the type of headache, the optimal therapy will vary. For example, tension headaches can be treated with acupuncture or biofeedback, in which a patient sees the vital signs and brain activity occurring during the headache. Many specialized pieces of equipment are used to obtain these measurements to allow a patient to visualize the effects of stress and tension. Brain activity is displayed by electroencephalogram (EEG) while muscle tension is viewed by electromyography and sweat production is measured with a galvanic skin response (GSR). By viewing a representation of these events, a patient can better learn to relax and control the triggers leading to their headaches.

Although biofeedback is often initially performed under medical care, over time, patients can learn to use these techniques independently, even without the instrumentation. As a patient learns to better control the triggers of their headaches, they may also learn to use relaxation techniques to alleviate the triggers and prevent the onset of a headache.

Because tension headaches are associated with muscle strain, physical therapy and chiropractic therapy may also be effective treatments. Such treatments involve manipulation or massage of the strained muscles in the head or skull. Such techniques can relax the affected muscle groups to relieve the tension associated with the headache. These techniques may also help to relieve stress that may be causative for tension headaches.

Pharmacological Treatment

Many over-the-counter medications are first line treatments for headaches. These medications are typically oral anti-inflammatory medications used in many types of headaches, including cluster, tension, and migraine headaches. For people suffering from episodic headaches for no more than ten days per month, NSAIDs (non-steroidal anti-inflammatory drugs) are often effective treatment options. Additionally, high doses of acetaminophen are effective against mild migraines, and opioids may be effective for more severe migraines. Opioids block pain signals in the spinal cord, preventing the pain signals from reaching the brain. Opioids used for this purpose include fentanyl, morphine, and codeine. Anticonvulsants, including topiramate, carbamezapine, and gabapentin may also be used to treat migraine headaches.

Risk Factors And Side Effects Of Treatment

Prolonged use of NSAIDs may lead to an increased risk of organ failure, while high doses of acetaminophen carry a risk of liver damage and failure. These risks are especially important for migraine sufferers, as they may seek increasing doses to alleviate the pain. Opioids carry their own risk, due to the chance of drug addiction or decreased effectiveness resulting from drug tolerance. Suddenly stopping a treatment may lead to worsening migraine symptoms, as is often the case with opioid therapies. The anticonvulsant carbamezapine has its own side effects that can cause damage to skin and internal organs. Specifically, it may cause allergic reactions, skin irritation, and toxic epidermal necrolysis.

Anesthetics and associated treatments carry their own risk of severe side effects. Anesthetics associated with nerve blocks may cause nausea, respiratory depression, or even nerve desensitization and damage. Prolonged use of steroids can suppress the immune system and lead to arthritis and weight gain. Other risks of spinal cord stimulation, nerve blocks, and RFA can result from treatment affecting adjacent areas, as a result of an improper injection to the wrong area of the spine or a blood vessel. These risks include numbness, discomfort, respiratory depression, or even paralysis. Chest numbness or nausea may also be present as neurological symptoms.

Any procedure with an injection carries risks of soreness, discomfort, bleeding, or infections at the injection site. Although the risk is low, motor nerve damage may also occur as a result of ablation treatments. Occasionally, accidental movement of implants from cervical spinal cord stimulation may cause nerve and tissue damage. In rare cases, the pain may be accentuated instead of attenuated.

New And Novel Developments In Treatments Of Headaches


Although the currently available treatments are widespread and generally effective, new and alternative treatments are currently under development. It is hoped that these treatments will offer additional options for pain relief in headache sufferers. Many of these new procedures are based on methods designed to inhibit, interfere with, or disrupt the pain signals being transmitted from the nerve cells to the brain. Impulses or waves of energy to the affected nerves can be used to lessen the signals in the brain or affect other neural circuitry intended to inhibit the signals being sent to the brain.

One such method of neuromodulation is deep brain stimulation. Deep brain stimulation involves electrodes implanted directly into the brain that are used to override the signaling from damaged nerves. It may also be used to alter the signaling and restore it to normal. This treatment option has been used to treat tension and cluster headaches by stimulating the parts of the brain in the region of the hypothalamus or by inhibiting the pain signals. The effectiveness of this treatment has implications in the link between sleep disorders and headaches, because the hypothalamus is the region of the brain that controls sleep and consciousness. Deep brain stimulation trials are ongoing and will provide further information regarding any potential linkage between headaches and sleep deficits and disorders.

Other nerve clusters and regions of the brain are also candidates for neuromodulation. Because the sphenopalatine ganglion (SPG) is associated with certain cluster and sinus headaches, this group of nerves may be targeted to help resolve or prevent these types of headaches. In clinical trials, 68% of patients in a test group were found to experience pain relief after a microstimulator device was implanted into the SPG. These devices work in a manner similar to spinal cord stimulation, which has significant positive results.

Although successful, much is still unknown about the longevity of these devices as well as the duration of the pain relief resulting from their use. Additional risks of SPG implants are perturbations to senses or a loss of sensation. The procedure is also somewhat invasive, bringing with it the associated risks such as infection and tissue damage. Similarly, microstimulators can be used to stimulate the occipital nerve, which has recently been shown to relieve pain associated with cluster, migraine, and tension headaches.

Transcranial Stimulation

While microstimulators are an invasive procedure, transcranial stimulation is a method of neuromodulation that is non-invasive. This method involves electrodes attached to pads or a cap applied to the scalp. Impulses are transmitted through the skull to the target nerves. Several different methods exist for this type of treatment, including transcranial magnetic stimulation, transcutaneous electrical nerve stimulation (TENS), and transcranial direct current stimulation. One viable target for TENS is the vagus nerve. The vagus nerve is a major cranial nerve that regulates signals from damaged nerves and emits pain-blocking signals. Transcranial vagus nerve stimulation (tVNS) has been shown to be effective in cluster and migraine headache treatment. This type of treatment carries mild and minimal side effects, such as mild pain and muscle cramps in the skull.

Chronic migraines, particularly at the time of onset, may be treatable by transcranial direct current stimulation (tDCS). Clinical trials involving 42 migraine sufferers receiving either tDCS or sham treatment showed promising results with significant pain relief only in the patients receiving tDCS treatment. An additional trial of 13 patients offered tDCS followed by sham treatment and showed a significant reduction in pain when patients received tDCS. Certain drugs, such as carbamezapine, block the effects of tDCS, limiting the patients who can receive this treatment. tDCS side-effects are minor, but may include discomfort around the electrode such as stinging, itching or burning sensations in addition to nausea, redness, and flashing lights at the start of treatment.

Another treatment option for episodic migraines may be transcranial magnetic stimulation (TMS). Clinical trials demonstrated significant reductions in both headache frequency and severity in six patients receiving TMS treatment, over five patients receiving sham treatment. The TMS patients also experienced other improvements, such as reduced intake of oral medications and improvement of normal functions. The convenience, simplicity, and effectiveness of this non-invasive treatment make it a tempting treatment option. Additionally, the equipment necessary for TMS is already in use for other medical conditions. Despite the equipment already being available, additional clinical trials will be needed on their use for treatment of headaches before TMS becomes a widely accepted therapeutic option.

New And Alternative Pharmacological Treatments

Other pharmacotherapeuticals for headache are still being evaluated and tested as potential treatments. One such treatment that has been in use is botulinum toxin type-A, which is marketed under the trade name Botulinum®. Although it is known historically as a neurotoxin that causes fatal respiratory depression, Botulinum has been used as a cosmetic treatment to smooth out wrinkles in the face by decreasing muscle activity. The mechanism of action has allowed this compound to be effective in treating headaches when it is injected around strained muscles, such as in the forehead, during a headache. It is thought that the anesthetic pain-blocking effect results from the disruption of the nerves and their associated muscles.

Through clinical trials with Allergan, botulinum toxin has recently been approved as a treatment for tension headaches and chronic migraines. Despite these successes and its use as a headache treatment, independent trials have demonstrated only modest effectiveness. Specifically, this treatment has reduced effectiveness in headaches resulting from medication, and its effectiveness is limited to treating migraines associated with facial pain.

Various other drugs are used for the treatment of headaches, including triptans delivered via inhalers or nasal sprays. These are particularly effective in treating sphenopalatine ganglion (SPG)-associated cluster headaches. A vasodilator used to treat hypertension or angina, verapamil, is effective in treating sleep disturbance-related headaches, cluster headaches, and chronic migraines. Unfortunately, verapamil may also cause headaches as a side effect, potentially limiting its use. An anticonvulsant medication, Valproate, has also been used as an effective migraine treatment.

As mentioned before, some antidepressants may also be effective at treating headaches. However, it is not clear whether the effectiveness is limited to headaches associated with depression. Such medications that have been used to relieve pain associated with tension and migraine headaches include venlafaxine and amitryptyline. Lithium, although no longer considered a modern treatment for depression, has been used as an effective treatment for sleep-related headaches.

Alternative Theories Of Pathophysiology And Treatment

Altered Pain Perception

Other advancements in headache research involve the cause, onset, and progression of headaches. In addition to primary theories that have been upheld by evidence involving the origination of pain from nerve damage, the possibility of new primary sources of headaches and associated pain are being explored and tested. Due to the poor understanding of the origins of tension headaches, the only known connections are with the associated factors discussed above, such as stress and muscle tension. It has also been theorized the malfunctioning processing of signals in the brain may be responsible for the perceived pain. Various observations support this theory, such as a heightened sense of pain in sufferers of tension headaches. Such patients also appear to have a diminished ability to properly regulate pain signals as compared to their counterparts who do not suffer from the same condition. If this theory is upheld, then it would support the use of TENS as a potential treatment for tension headaches. The electrical stimulation from TENS may serve to fix the abnormal processing of pain that may be occurring in these patients.

The Cervicogenic Hypothesis

The cervicogenic hypothesis is another concept for the cause of headaches. This concept points to neck injuries and problems as a primary causative factor for cluster headaches and migraines. A foundation of this idea is based on the fact that the nerve complexes associated with these types of headaches, the trigemino-cervical complex and occipital nerve, are located in the neck and base of the skull. This theory is further supported by the fact that treatments targeting these nerves are effective for these types of headaches. If this theory holds true, then some of these types of headaches would be reclassified as secondary headaches, since they would originate from neck injuries.

This theory could also explain headaches in the elderly, as neck problems are more common in that age group. This is due to a number of factors, including inflammation, bone loss, and poor posture. Poor posture is also problematic in many office workers or in occupations involving large amounts of strain to the neck and shoulders. Headaches originating from these issues may be alleviated by therapy, massage, nerve blocks, stimulation, or, in extreme cases, ablation.

Post-traumatic stress disorder has also been acknowledged as a cause of headaches, although how this occurs is not well understood, except in cases involving a head or neck injury.


With nearly 50 million people from the U.S. affected, headaches are a widespread medical problem, resulting in diminished quality of life and lost productivity. Headaches are characterized by pain, either acute, chronic, or episodic, that occurs in the upper neck or head area. Depending on the nerves associated with the pain, there are different classifications of headaches. They may result from a number of causes, including inflammation, acute or sustained injury, or may be related to a more serious condition. It is also possible that headaches are a secondary result of neck disorders or injury.

Headaches fall into two broad categories, primary and secondary. A disruption to pain-sensing nerves in the head or neck causes primary headaches. Other medical conditions that originate elsewhere in the body lead to secondary headaches. Each type of headache has a number of treatment options, and more are currently being investigated. Speak with your physician if you experience any sudden change in symptoms or are seeking a new course of treatment.


  1. Clinch CR. Evaluation of acute headaches in adults. Am Fam Physician. 2001;63(4):685-92.
  2. Hainer BL, Matheson EM. Approach to acute headache in adults. Am Fam Physician. 2013;87(10):682-7.
  3. Mathew NT. The prophylactic treatment of chronic daily headache. 2006;46(10):1552-64.
  4. Rabbie R, Derry S, Moore RA. Ibuprofen with our without an antiemetic for acute migraine headaches in adults. Cochrane Database Syst Rev. 2013;4.
  5. Rapoport AM. Acute treatment of migraine: Established and emerging therapies. 2012;52(Suppl2):60-4.
  6. Rapoport AM. The therapeutic future in headache. Neurol Sci. 2012;33(Suppl 1):S119-25.
  7. Cooper RJ. Over-the-counter medicine abuse – a review of the literature. Journal of substance use. 2013;18(2):82-107.
  8. Rodman R, Dutton J. Endoscopic neural blockade for rhinogenic headache and facial pain: 2011 update. International forum of allergy & rhinology. 2012;2(4):325-330.
  9. Martelletti P, Jensen RH, Antal A, et al. Neuromodulation of chronic headaches: position statement from the European Headache Federation. The journal of headache and pain. 2013;14(1):86.
  10. Gabrhelik T, Michalek P, Adamus M. Pulsed radiofrequency therapy versus greater occipital nerve block in the management of refractory cervicogenic headache – a pilot study. Prague medical report. 2011;112(4):279-287.
  11. Levin M. Nerve blocks in the treatment of headache. Neurotherapeutics : the journal of the American Society for Experimental NeuroTherapeutics. 2010;7(2):197-203.
  12. Bayer E, Racz GB, Miles D, Heavner J. Sphenopalatine ganglion pulsed radiofrequency treatment in 30 patients suffering from chronic face and head pain. Pain practice : the official journal of World Institute of Pain. 2005;5(3):223-227.
  13. Oomen KP, van Wijck AJ, Hordijk GJ, de Ru JA. Effects of radiofrequency thermocoagulation of the sphenopalatine ganglion on headache and facial pain: correlation with diagnosis. Journal of orofacial pain. 2012;26(1):59-64.
  14. Sacco S, Ricci S, Carolei A. Migraine and vascular diseases: A review of the evidence and potential implications for management. 2012;32(10):785-95.
  15. Shapiro RE. Preventive Treatment of Migraine. Headache. 2012;52(Suppl 2):65-9.
  16. Silberstein SD. Treatment recommendations for migraine. Nat Clin Pract Neurol. 2008;4(9):482-9.
  17. Silberstein SD, Holland S, Freitag F, Dodick DW, Argoff C, Ashman E, Quality Standards Subcommittee of the American Academy of Neurology and the American Headache Society. Evidence-based guideline update: Pharmacologic treatment for episodic migraine prevention in adults: Report of the Quality Standards Subcommittee of the American Academy of Neurology and the American Headache Society. 2012;78(17):1337-45.
  18. McMurtray AM, Saito EK, Diaz N, Mehta B, Nakamoto B. Greater frequency of depression associated with chronic primary headaches than chronic post-traumatic headaches. International journal of psychiatry in medicine. 2013;45(3):227-236.
  19. Freitag F. Managing and treating tension-type headache. The Medical clinics of North America. 2013;97(2):281-292.
  20. Krusz JC. Tension-type headaches: what they are and how to treat them. Primary care. 2004;31(2):293-311, vi.
  21. Alves AC, Alchieri JC, Barbosa GA. Bruxism. Masticatory implications and anxiety. Acta odontologica latinoamericana : AOL. 2013;26(1):15-22.
  22. Castien R, Blankenstein A, van der Windt D, Heymans MW, Dekker J. The working mechanism of manual therapy in participants with chronic tension-type headache. The Journal of orthopaedic and sports physical therapy. 2013;43(10):693-699.
  23. Singh NN, Sahota P. Sleep-related headache and its management. Current treatment options in neurology. 2013;15(6):704-722.
  24. Manaka S. [Application of acupuncture as a headache management tool]. Rinsho shinkeigaku = Clinical neurology. 2012;52(11):1299-1302.
  25. Bendtsen L, Evers S, Linde M, Mitsikostas DD, Sandrini G, Schoenen J. EFNS guideline on the treatment of tension-type headache – report of an EFNS task force. European journal of neurology : the official journal of the European Federation of Neurological Societies. 2010;17(11):1318-1325.
  26. Bendtsen L, Jensen R. Treating tension-type headache — an expert opinion. Expert opinion on pharmacotherapy. 2011;12(7):1099-1109.
  27. Holle D, Obermann M. The role of neuroimaging in the diagnosis of headache disorders. Therapeutic advances in neurological disorders. 2013;6(6):369-374.
  28. Tfelt-Hansen PC, Jensen RH. Management of cluster headache. CNS drugs. 2012;26(7):571-580.
  29. Shimazu T. The recent pathophysiology of cluster headache (trigeminal autonomic cephalalgias; TACs). Rinsho shinkeigaku = Clinical neurology. 2013;53(11):1125-1127.
  30. Shimizu T. New treatments for cluster headache. Rinsho shinkeigaku = Clinical neurology. 2013;53(11):1131-1133.
  31. Lambru G, Abu Bakar N, Stahlhut L, et al. Greater occipital nerve blocks in chronic cluster headache: a prospective open-label study. European journal of neurology : the official journal of the European Federation of Neurological Societies. Dec 7 2013.
  32. Goyal A, Panchani R, Varma T, Bhalla S, Tripathi S. Adrenal incidentaloma: A case of pheochromocytoma with sub-clinical Cushing’s syndrome. Indian journal of endocrinology and metabolism. Oct 2013;17(Suppl 1):S246-248.
  33. Martelletti P, Jensen RH, Antal A, et al. Neuromodulation of chronic headaches: position statement from the European Headache Federation. The journal of headache and pain. 2013;14(1):86.
  34. Singh NN, Sahota P. Sleep-related headache and its management. Current treatment options in neurology. 2013;15(6):704-722.
  35. Clelland CD, Zheng Z, Kim W, Bari A, Pouratian N. Common cerebral networks associated with distinct deep brain stimulation targets for cluster headache. Cephalalgia : an international journal of headache. Oct 16 2013.
  36. Lin KH, Chen SP, Fuh JL, Wang YF, Wang SJ. Efficacy, safety, and predictors of response to botulinum toxin type A in refractory chronic migraine: A retrospective study. Journal of the Chinese Medical Association : JCMA. Oct 23 2013.
  37. Gady J, Ferneini EM. Botulinum toxin A and headache treatment. Connecticut medicine. 2013;77(3):165-166.
  38. Hu Y, Guan X, Fan L, et al. Therapeutic efficacy and safety of botulinum toxin type A in trigeminal neuralgia: a systematic review. The journal of headache and pain. 2013;14(1):72.
  39. Watanabe Y, Takashima R, Iwanami H, Suzuki S, Igarashi H, Hirata K. Management of chronic migraine in Japan. Rinsho shinkeigaku = Clinical neurology. 2013;53(11):1228-1230.
  40. Linde M, Mulleners WM, Chronicle EP, McCrory DC. Antiepileptics other than gabapentin, pregabalin, topiramate, and valproate for the prophylaxis of episodic migraine in adults. The Cochrane database of systematic reviews. 2013;6:Cd010608.
  41. Smitherman TA, Walters AB, Maizels M, Penzien DB. The use of antidepressants for headache prophylaxis. CNS neuroscience & therapeutics. 2011;17(5):462-469.
  42. Bezov D, Ashina S, Jensen R, Bendtsen L. Pain perception studies in tension-type headache. 2011;51(2):262-271.
  43. Chua NH, Suijlekom HV, Wilder-Smith OH, Vissers KC. Understanding cervicogenic headache. Anesthesiology and pain medicine. 2012;2(1):3-4.
  44. De Hertogh W, Vaes P, Versijpt J. Diagnostic work-up of an elderly patient with unilateral head and neck pain. A case report. Manual therapy. 2013;18(6):598-601.
  45. Huber J, Lisinski P, Polowczyk A. Reinvestigation of the dysfunction in neck and shoulder girdle muscles as the reason of cervicogenic headache among office workers. Disability and rehabilitation. 2013;35(10):793-802.
  46. Chaibi A, Russell MB. Manual therapies for cervicogenic headache: a systematic review. The journal of headache and pain. 2012;13(5):351-359.
  47. Carlson KF, Taylor BC, Hagel EM, Cutting A, Kerns R, Sayer NA. Headache Diagnoses Among Iraq and Afghanistan War Veterans Enrolled in VA: A Gender Comparison. 2013;53(10):1573-1582.
  48. Runnals JJ, Van Voorhees E, Robbins AT, et al. Self-Reported Pain Complaints among Afghanistan/Iraq Era Men and Women Veterans with Comorbid Posttraumatic Stress Disorder and Major Depressive Disorder. Pain medicine (Malden, Mass.). Aug 7 2013.
  49. Moeller DR. Evaluation of a Removable Intraoral Soft Stabilization Splint for the Reduction of Headaches and Nightmares in Military PTSD Patients: A Large Case Series. Journal of special operations medicine : a peer reviewed journal for SOF medical professionals. 2013;13(1):49-54.