The exact cause of cluster headaches is not known. Many experts believe that cluster headaches and migraine headaches have a common cause that begins in the trigeminal nerve, a

nerve that carries sensations from the head to the brain and that ends in the blood vessels that surround the brain. Other experts link cluster headaches to the hypothalamus, an

area of the brain. Either explanation would account for the periodic nature of the headache.

Brain Tumors
Many people with brain tumors have headaches. Their pain may be worse in the morning as a result of pressure buildup in the brain after lying flat all night. It usually

increases with coughing or straining, and is often accompanied by nausea and vomiting. CT (computer tomography) scans or MRI (magnetic resonance imaging) scans can help

differentiate between cluster headaches and those caused by brain tumors.

Infections
Meningitis, an infection of the coverings of the brain, or brain abscess, a collection of infected tissue in the brain, also can lead to headaches. Such patients may have a

stiff neck, fever, abnormal laboratory test or neurological examination results. CT scans, MRIs or a spinal tap, a procedure in which cerebrospinal spinal fluid is drawn for

examination, may be necessary for a differential diagnosis.

Other infections that can cause headaches are sinusitis (sinus infection), ear infections, dental disease and infections of the eye.

Cerebral Aneurysm
An aneurysm is a widening of a blood vessel wall that can rupture, leading to bleeding in the brain, known as subarachnoid hemorrhage. The pain this causes has often been

described as the worst headache of one's life. CT scans and MRI scans are used to make a differential diagnosis. Other tests include angiography (procedure in which a catheter

is threaded upward through successive arteries to the neck and brain, where a contrast dye is injected into the blood to facilitate x-ray images) and spinal tap, which can

disclose the presence of blood in the cerebrospinal spinal fluid.

Temporal Arteritis
An inflammation of an artery, this disorder usually occurs in older persons, and is associated with headache, muscular and joint aches, weight loss, malaise, fever and sometimes

jaw pain. Its most worrisome symptom is transient visual loss, which may lead to permanent blindness if the disorder goes undiagnosed.

Patients typically complain of tenderness when the scalp or sides of the head are touched. Laboratory studies may show an elevation of the patient's ESR (erythrocyte

sedimentation or "sed" rate), indicating inflammation. Some patients with temporal arteritis also have low blood iron levels (anemia). Most patients with suspected temporal

arteritis are sent for a biopsy, in which a surgeon removes a small piece of the inflamed artery for microscopic examination to ensure correct diagnosis. Treatment involves

steroids, mainly prednisone, often for an extended period to control the inflammation and prevent blindness.

Trigeminal Neuralgia
This pain, also known as tic douloureux, involves the nerves of the face and usually occurs on one side of the face only. Its pain is intermittent and severe, often describes as

electric shock-like or stabbing. Talking, eating, or even by something as seemingly innocuous as wind blowing against the cheeks may trigger pain. Where many attacks occur in a

short period, the face may be sore constantly. People often lose weight and sleep from frequent attacks.

Trigeminal neuralgia is most common in people over 40. The disorder may have many causes. Multiple sclerosis, tumors and blood vessel abnormalities may be responsible for a few

cases, but in most instances the cause remains obscure.

One of the more commonly prescribed drugs used to treat trigeminal neuralgia is carbamazepine (Tegretol, Carbatrol). Three-quarters of all patients respond favorably to its use.

Other medications that may be beneficial include gabapentin (Neurontin), tramadol (Ultram) and phenytoin (Dilantin). Pain medications also may be necessary during prolonged

attacks.