What are Headaches?
Headaches Explained by Las Vegas, Summerlin, and Henderson Nevada’s Top Pain Doctors
Headaches are a very common ailment. They are most often described as pain in the head or upper neck, and can be felt in specific areas of the head or face, or at the base of the skull. Headaches can be chronic, a constant source of pain and discomfort, or acute, with a sudden onset, causing sharp, stabbing pains. Some types of headache occur consistently at certain times of day (“episodic” headaches). It is estimated that 45 million people in the U.S. suffer from recurrent headaches. Acute headaches are classified as pain or discomfort experienced anywhere within the head or neck that has a very sudden onset, and rapidly gets worse afterwards.
Many types of headache may feel as though they are coming from, or are driving deep into, the brain. However, the brain itself does not actually feel pain (i.e. it does not have the specific biological receptors for pain). Headaches are caused by an irritation (chemical or physical damage) of the many structures surrounding the brain, including the skull, muscles, nerves, arteries, veins, subcutaneous tissue, eyes, ears, sinuses, and mucous membranes. This is usually the result of inflammation, injury, or disease. Certain major nerves transmit this information, i.e. the fact that something is causing pain, back into the brain, which is the basis of this effect.
Headaches can be a source of distraction and irritability at best, and at worst a source of serious pain that can significantly impact normal daily life. Headaches do cause a significant cost to healthcare systems. They are also a leading reason for over-the-counter pain medication (i.e. mild analgesics such as pseudoephedrine and acetaminophen) consumption. Chronic or episodic headache is often resistant to this method of treatment, however. Headaches can cause a significant decrease in concentration, cognition, and the capacity to function normally.
Classification of Headaches
Some common types of headaches are considered separate conditions in their own right. They are referred to as primary headaches if there is no underlying condition or illness causing them.
Migraine headaches are common. They are considered the most common of all primary (i.e. arising from a singular condition or explanation) headaches by researchers. The number of new cases per year is reported to be as high as 12% of the U.S. population. Women are three times more likely to experience migraine pain across the course of their lifetime than men. Some experience chronic migraine pain associated with their menstrual cycle. Migraine headaches are considered a recurrent, episodic disorder and are typically characterized by intense episodes of severe, throbbing pain within the head. Migraines are usually felt just behind or above one eye. Over time, the pain may spread to other areas of the face, especially if left untreated. They may also be accompanied by sensitivity to light, sound, or odors, as well as nausea or vomiting.
Migraine symptoms can last from several hours to several days. Furthermore, some have described the symptoms associated with migraines as progressing through four separate stages:
- The prodromal phase, occurring up to 24 hours prior to the onset of acute migraine pain. During this phase, individuals may notice a change in energy levels or mood, irritability, excessive thirst, unusual food cravings, frequent yawning, feelings of drowsiness, and frequent urges to use the restroom.
- The aura phase, in which many individuals will experience neurological symptoms, or an aura, which are linked to an imminent migraine episode. These symptoms typically occur twenty minutes to an hour before the pain of the migraine begins. Not all migraine sufferers report auras prior to the onset of a migraine episode.
- The attack phase is the point at which individuals may experience intense and severe symptoms as described above, possibly accompanied by light-headedness and even fainting. Without treatment, this phase typically lasts four to 72 hours.
- The postdrome phase occurs after the migraine episode has passed. Individuals in this phase report feeling fatigued and drained. Some individuals have reported mild feelings of euphoria. While most episodes of migraine pain are not related to a more serious disease or illness it is important that you monitor your symptoms closely, especially in cases of sudden exacerbation or increased intensity of pain.
Cluster headaches are typically experienced as severe, migraine-like pain over an eye and/or the temple, again often on just one side of the head. This type of headache frequently occurs at night and is reported to frequently wake the individual up from sleep. The pain may last between thirty minutes and two hours. They can also be characterized as a succession of headaches, occurring as often as eight times in one day. This type of headache can be accompanied by light sensitivity, watering of the eyes, and nasal congestion.
Cluster headaches are most common in men of between 20 and 40 years of age. They are thought to affect 0.01% of the world’s population. Based on patient reports, they are regarded as the worst pain a human can experience.
Tension-type headaches are experienced in the forehead or the back of the head. They usually follow a regular pattern, so that they may regularly begin in the late afternoon, remit by evening, and can occur every day. Tension headaches can also be chronic, i.e. experienced chronically for most of the day or even several days on end.
Patients often describe tension-type headaches as extreme pressure around the forehead or head. They can also be associated with throbbing, stabbing, or grinding pain in the facial muscles. Sufferers may also experience light and sound sensitivities. Episodic tension headaches can last from half an hour to several days. They occur for up to fifteen days a month. More frequent pain episodes are termed chronic tension-type headaches.
Tension headaches are the most common type of headache, affecting approximately 3% of the total population. They may be milder than other types, such as migraines, but they can be disruptive and distressing nonetheless. They are associated with a loss of concentration, irritability, and increased sensitivity to external stimuli, which can act as triggers of tension headaches.
A secondary headache can take the form of any of the headache types described above, but as a symptom of an underlying condition or a side-effect of a medical treatment. Secondary headaches can be caused by conditions such as arthritis and fibromyalgia. Generally, the source of secondary headache pain is not serious or life threatening. In fact, patients who have had a headache in the past and who do not also meet any of the following criteria are considered at a low risk for a serious underlying problem. It is important to monitor symptoms closely however, and to make an appointment with your physician’s office to rule out any more severe conditions. However, if you experience symptoms such as very unusual headache pain or a much more severe headache than usual, for example, this may be a cause for concern.
If the headache is accompanied by a heretofore-unexperienced aura (described as visual disturbances such as metallic lines within one’s field of vision, or unusual sensory, motor, or speech disturbances), it may be a sign of a serious underlying condition. If it is triggered by coughing, exertion, or while engaged in sexual intercourse, this may indicate a vascular condition such as an embolism or stroke. Pain along with a change in personality or mental status, or with loss of consciousness, should also be taken seriously. A headache also accompanied by stiffness in the neck, a fever, or rash may be a symptom of meningitis. A headache accompanied by tenderness in or around the temples is also a sign of possible serious illness, such as an aneurysm. If alarming symptoms occur, please consider seeking immediate medical attention. It may be a false alarm, but it is better to be safe than sorry.
Causes and Pathophysiology of Headaches
Headache pain is transmitted by nerves in the membranes inside the skull, or major nerves radiating out of the brain. These nerves may have incurred injuries or damage from inflammation or irritation. This is mostly linked to headaches that are chronic or recurrent. Headaches are divided into primary and secondary categories. Secondary headaches result from damage to nerves or other tissues anywhere in the body as a result of another condition or illness, whereas primary headaches are a condition caused by direct damage to the nerves in the brain or skull. Some headaches arise for no diagnosable reason at all, however. These are called idiopathic headaches.
Headaches centered at the base of the skull or top of the neck can be traced to the occipital nerve. Migraine headaches can be attributed to a number of important nerves in a network called the trigemino-cervical complex. Other migraine symptoms, such as photophobia (aversion to light), sonophobia (aversion to sound), and extreme episodic pain can originate from this complex. Episodic migraines are associated with damage to the trigeminal nerve, a major nerve in the brain. Some cluster headaches can also be traced to this nerve, though they are thought to result from a different mechanism of damage to that associated with migraines. Other cluster headaches can also be attributed to a group of nerve endings in the skull called the sphenopalatine ganglion (SPG). Some headaches in or around the nasal area (often called sinus headaches) can also be traced to the SPG.
Tension headaches are associated with physiological factors such as eyestrain, stress, anxiety, and hunger. They are also known to be a side-effect of sleep deprivation. Tension headaches are also associated with jaw problems, such as teeth grinding or clenching. Unlike migraine and other types of pain, tension headaches are not (currently) strongly associated with one specific major nerve group. It is associated more with extreme muscle strain in the jaws or temples, transmitted to the brain by a variety of nerves in the skull or brain. These include the SPG, occipital, and trigeminal nerves.
As mentioned above, tension headaches are often a result of stress, and other physiologically detrimental factors such as sleep loss and eye-strain (pain or damage to the eyes is transmitted by many major nerves, including the trigeminal nerve). Stress is associated with inflammation. Other disorders that may cause inflammation in the nerves associated with headaches are autoimmune disorders, such as arthritis.
Another disease that may cause nerve damage is cancer; tumors may press on a certain nerve, causing headaches. Cancer treatments may result in the same type of damage themselves. Radio- or chemotherapy may damage many types of normal tissue in the vicinity of a cancer in the course of administration, resulting in acute or chronic pain.
Some other factors that are associated with headache are dehydration or hunger. Headaches can also be a side-effect of many drugs, even common ones such as caffeine. Headaches as a result of the overuse of medication are a common diagnosis. Another condition commonly associated with headaches is depression. It is not clear if depression causes headaches, or if chronic, intractable migraine or cluster headaches may in fact set off depressive symptoms.
Diagnostic Methods for Headaches
Specific primary headaches, such as migraine, can be diagnosed by a physician by having the patient describe their symptoms. There are a range of rating systems for headache types. It is also possible to diagnose a headache by brain imaging techniques such as MRI.
If a specific nerve is suspected to be the source of a headache, its signals can be blocked to see if this will stop the pain. This is achieved by delivering anesthetic medications by injection through the skin (which will be treated with local anesthetics beforehand) directly to the location of the nerve. For example, an injection at the location of the occipital nerve (at the base of the skull) may result in the inhibition of pain. These injections, containing anesthetics such as lidocaine, and steroids that treat inflammation, are called nerve blocks.
Treatments for Headaches
Nerve blocks, if successful, are also effective medium-term treatments for headaches. Occipital, trigeminal, and SPG blocks are often indicated for cluster and chronic migraine headaches. They can achieve pain relief lasting from weeks to months between treatments. Trigemino-cervical blocks are applied to the upper neck. SPG blocks must be applied by inserting a thin needle into the nasal or oral passages, and onward into its location in the skull. The anesthetic will then be injected through this needle.
Other Direct Nerve Treatments
If headaches prove resistant to this treatment, the next step is often radiofrequency ablation (RFA) of the affected nerves. In this procedure, thin probes are inserted at the desired location. These probes then deliver radiofrequency waves (heat) to the nerve to disrupt it and thus prevent it from sending pain signals to the brain. SPG ablation has been shown to be effective in treating chronic nasal or sinus headaches, and occipital RFA was found to be as effective as blocks in alleviating pain.
Another method of headache relief is spinal cord stimulation (SCS), in which wire-like implants are placed along the spine, near nerves that are the source of pain (e.g. parts of the trigemino-cervical complex). These implants are inserted through the skin, and attached to leads, through which a mild electrical impulse can be delivered with a controller. These impulses will interfere with pain signaling, so it cannot reach the brain. Spinal cord stimulation is effective in controlling migraine-related pain.
Alternative or Complementary Treatments
Different options work better for different types of headaches. Tension headaches respond better to treatments such as acupuncture and biofeedback. In biofeedback, the patient is shown measurements of various relevant vital signs recorded during a headache. These can include brain activity, measured by electroencephalograms (EEG), and muscle tension, visualized by electromyography and sweat production (galvanic skin response). These readings can be affected by stress and tension. By seeing these graphs, patients can better understand the physiological changes associated with their headaches, and learn to control them through relaxation. Biofeedback may need to be practiced in a health center at first, but over time patients can implement the technique themselves, with or without viewing the measurements. Biofeedback may help a patient anticipate tension headache triggers, and either avoid them or apply relaxation techniques in response to them.
Physical or chiropractic therapy can also be helpful in treating tension headaches. As they are associated with strain in muscle groups of the skull, massage or manipulation is effective in tension headache relief. Manipulation is thought to dispel the tension or pain in the muscle groups affected. Massage also removes tension, and may also help to alleviate the stress that contributes to tension-type headaches.
The first line of treatment for all types of headache is, as you might expect, oral medication. As headache pain is associated with inflammation, drugs that prevent this are used in migraine, cluster, and tension headache treatment. Non-steroid anti-inflammatory drugs (NSAIDs, e.g. naproxen or aspirin) are a common first-line treatment, but they are most effective in people with episodic migraines who experience headaches on ten days of every month or less. Acetominaphen (paracetamol) in high doses is also effective in treating mild episodes of migraine. Opioids, prescribed to patients with severe migraine, are drugs that activate receptors in the spinal cord to inhibit pain signals. Common examples of opioids include morphine, codeine, and fentanyl. Carbamezapine, gabapentin, and topiramate are anticonvulsants often prescribed for episodic migraine.
Side Effects and Risk Factors of Treatment
NSAIDs increase the risk of organ failure if they are taken constantly over a prolonged period. As it is common medical advice to increase a dose of medication in response to the onset of migraine, this risk is magnified in these patients. Acetaminophen may also cause liver failure if taken regularly over time, or taken in excess.
Opioids are associated with the risk of addiction and drug tolerance. Patients taking opioids for migraine may find their symptoms are much worse if they suddenly stop using them. Carbamezapine can have severe side effects. These include skin irritation, toxic epidermal necrolysis, and allergic reactions. These reactions damage the skin and organs, and are more prevalent in individuals of Asian descent.
Nerve blocks, RFA, and spinal cord stimulation can also have side effects. The main risk associated with nerve blocks is an adverse reaction to the anesthetics injected, which range from nausea to respiratory depression, as well as nervous desensitization and damage. Steroids can cause weight gain, arthritis, and immune system depression. Other risks of these procedures are nerve damage, inadvertent injection of a blood vessel or the wrong area of the spine, which can cause numbness, discomfort, respiratory depression, and paralysis in severe cases. Temporary neurological complications such as nausea and chest numbness can also occur. The most common risks of RFA are bleeding and infections at the insertion site, and discomfort resulting from the procedure. There is also a low incidence of motor nerve damage resulting from ablation. There are risks associated with cervical spinal cord stimulation, including insertion-site infections, inadvertent amplification of pain rather than the opposite, and unwanted movement of the implant, which can cause tissue and nerve damage.
New and Upcoming Developments in Headache Treatment
In addition to these increasingly common and effective treatments for headache, there are other options currently being developed and evaluated for use in pain relief for these conditions. As with spinal cord stimulation, many of these are based on applications that will disrupt or interfere with the pain signals being transmitted by the nerve or nerve group affected. Many of these are based on neuromodulation, the use of impulses or waves of energy to dampen certain signals in the brain, and/or stimulating other neural circuits that will inhibit them.
Deep brain stimulation is an example of this. This technique employs electrodes implanted into the regions of the brain that override the signals coming from damaged nerves, or correct them by promoting more “normal” signaling. Tension- or cluster-type headaches have been treated with deep brain implants, stimulating regions of the brain connected to the hypothalamus to inhibit or re-modulate pain signals. The hypothalamus is an important structure of the brain at the center of control over sleep and consciousness. Therefore, success of this treatment option would further support the theory that these types of headaches are associated with sleep deficits and disorders. Research and clinical trials into deep brain stimulation as a headache treatment are still in progress.
In a similar vein, neuromodulation of the SPG, to correct cluster and nasal headaches associated with this group of nerves, is also possible. A microstimulator device implanted into the SPG has been shown to relieve pain in 68% of a test group of patients in a clinical trial of this method. Microstimulators, which work on demand in the same manner as spinal cord stimulators, have shown positive and significant results, but there is still some uncertainty about the duration of pain relief, and of the working life of the implant in this case. SPG implants would also carry the risks of sensory disturbances and loss of sensation. This is also a more invasive procedure and as such may cause infection and tissue damage in the course of implantation. Occipital nerve stimulation, via a microstimulator or techniques similar to spinal cord stimulation, has also been shown to be effective in migraine, cluster, or tension-type headaches in recent research.
Transcranial stimulation is a non-invasive method of neuromodulation. In this procedure, pads or a cap that delivers the stimulation are applied to the scalp, and impulses or waves travel through the skull to the nerve(s) targeted. There are a number of types of transcranial applications, such as transcutaneous electrical nerve stimulation (TENS), transcranial direct current stimulation, and transcranial magnetic stimulation. The vagus nerve, another major cranial nerve that emits analgesic (pain-blocking) signals to regulate other signals from damaged nerves or tissues, is a viable target for TENS. Electrical stimulation of the vagus nerve (tVNS) has shown promising results in small-scale trials in migraine and cluster headache treatment. The side-effects of tVNS are relatively mild, including temporary muscle cramps and pain in the skull.
Transcranial direct current stimulation (tDCS) may have potential in treating chronic migraine, particularly at the onset of an attack. A study of 42 migraine sufferers receiving either tDCS or an identical but sham treatment resulted in significant pain relief in the real tDCS group only. In another trial, thirteen patients with chronic migraine were treated with tDCS and then with a sham treatment. The real treatment achieved a significant reduction in pain and in the duration of attacks. The side-effects of tDCS include itching, stinging, or burning sensations in the area under the electrode, skin redness, nausea, and seeing flashing lights at the beginning of the treatment. Another drawback is that certain drugs, including carbamezapine, prevent tDCS from taking effect.
Transcranial magnetic stimulation (TMS) may be a treatment option for episodic migraines. A trial of TMS in six patients compared with five on an identical dummy treatment showed that the real treatment achieved significant reduction in headache severity and frequency. It also improved normal function in the patients, and reduced their intake of oral medications. These transcranial treatments may have a great deal of potential, as they are non-invasive, relatively simple and convenient, and are already developed as relevant medical equipment for other conditions similar to headache. However, there is still a need for large-scale clinical research into their application as a headache treatment before they can be made available for this purpose.
Alternative and Novel Pharmacological Treatments
There are also some other pharmacotherapy options for headache currently under evaluation and testing. One of these is botulinum toxin type-A, also known as onabotulinumtoxin A, BTX-A, or BOTOX™. This name may be familiar as a cosmetic treatment that “freezes” muscles causing wrinkles in the face. The BOTOX formulation is a neurotoxin, but at sufficiently low concentrations to prevent its normal function; that of causing fatal respiratory depression. In the last few years, BTX-A was also found to be effective in treating headaches when injected near the nerves and/or in the muscles under strain, in the course of an attack. It is thought to have a direct pain-blocking effect (similar to anesthetics), and also combat headaches by temporarily destroying the connections between nerves and muscles. BTX-A has recently been approved as a treatment for chronic migraine and tension headaches, as a result of Allergan’s PREEMPT program of clinical trials. However, the effects of the toxin on these types of pain have been shown to be modest at best in independent testing. It is more effective in treating migraines that are accompanied by facial pain, and headaches that are caused by medication overuse or abuse.
Other novel applications of drug administration include triptan (an older medication still prescribed for headache) inhalers or nasal sprays. These have been shown to be effective in treating cluster headaches associated with the SPG. Verapamil, a vasodilator usually associated with angina or hypertension treatment, has been found to be effective in treating cluster headaches, chronic migraine, and headaches associated with sleep disturbances. Ironically, it may cause headaches as a side-effect. Valproate, another anticonvulsant, has also shown efficacy in treating migraine.
There is also evidence that some antidepressant medications may treat headache pain. In particular, amitryptyline and venlafaxine have been associated with relief from migraine and tension-type headaches. Whether they treat all types of headache, or only those associated with depressive disorders, is not clear, however. The classic and now outmoded depression treatment, lithium, has also been reported as effective in treating headaches related to sleep deprivation.
Alternative Theories of Pathophysiology and Treatment
Altered Pain Perception
Another main advance in headache research involves the cause of headaches and how they manifest. The main theories of pain arising from specific nerve damage are still relevant and consistently upheld in the literature. In addition, new possible sources of primary headaches are being considered and tested. For example, the origins of tension-type headaches are still not completely understood, and are thus put down to the range of external factors that they are commonly observed to be linked with, as discussed earlier. There are newer theories that they may be related to malfunctioning “pain processing” centers in the brain that continually send any kind of signals from the face or skull as noxious. This may be backed up by observations that patients with chronic tension headaches are more sensitive to pain than normal counterparts, and have a reduced ability to control pain signals. If this theory is further proven, it may be a basis for the application of TENS to the treatment of these types of headache. Electrical stimulation may be able to correct this abnormal pain processing, as described above.
The Cervicogenic Hypothesis
Another new theory being investigated is the cervicogenic headache concept. This is the idea that more headaches, particularly migraines and cluster headaches, may be related to neck problems or injury than previously thought. This may be supported by the fact that the occipital nerve and trigemino-cervical complex (which as outlined above is often a target of migraine therapy) are located in this region. Given that both occipital blocks and stimulation are effective therapies for many types of headache, this theory may have yet more weight. If proven, it would mean a reclassification of some cluster and migraine headaches as conditions secondary to neck disorders, rather than primary as is the current trend.
As many elderly people have neck problems, relating to inflammation, bone loss, and poor posture, this theory is being increasingly used to explain headaches in this age group. The posture deficits seen in office workers, i.e. over-flexing of some muscles in the neck or shoulders, and under-use of some others, are also linked to headaches. Manual therapy or massage may be of some therapeutic value in cervicogenic headaches, in addition to nerve blocks or stimulation, or ablation in severe cases. Another interesting, recently acknowledged cause of headache is post-traumatic stress disorder. The exact reasons for this are still not completely understood, although in some cases it may obviously be due to trauma such as head or neck injury.
Headache is a common medical problem affecting nearly 50 million people in the U.S. It is a term for pain experienced in the head or upper neck area that can be acute, chronic, or episodic. Different types of headache can be attributed to different nerves in the head or the spine. Headaches can be the result of inflammation or injury to the nerves in question, or a side-effect of an even more serious condition. Newer theories may suggest that some headaches originate from damage to or disorders of the neck.
Acute headaches are sudden onset headaches in which pain is located anywhere in the head and neck, and severity worsens rapidly. There are two types of headaches: primary and secondary. Primary headaches result from a disturbance in the pain-sensing tissue within the head and neck. Secondary headaches are associated with other medical conditions within the body. A number of treatment options are available and are determined based on the specific characteristics of the headache. It is recommended that you speak with your physician to develop an appropriate course of treatment.
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