Researchers at the University of São Paulo, Brazil have pinpointed some characteristics of headaches that indicate a CVT - the formation of a blood clot in a vein of the brain. While most clots occur in arteries (which carry blood from the heart to the rest of the body) blood clots in a vein (which carries blood to the heart) is an infrequent condition.

CVT is often difficult to diagnose because individuals may experience a wide range of symptoms including headaches, seizures or visual impairments. Symptoms can occur suddenly or progress for weeks.

"It is particularly important to recognize this condition early before the clot may spread in the cerebral venous system leading to other neurological complications such as - seizures, visual or motor deficits and increase of intracranial pressure," says lead researcher Érica C.S. de Camargo, M.D.

Headache is frequently the first symptom reported by patients arriving in emergency rooms. The Brazilian study aimed to identify the specific characteristics of CVT-related headache to help differentiate CVT from other conditions.

Thirty-nine patients (69 percent female, average age 35 years) were evaluated from March 1996 to June 2000. They were confirmed to have CVT by magnetic resonance imaging and/or angiography. Pertinent headache information such as location, severity and duration was recorded on a standardized form.

Seventy-four percent of patients with headaches also had weakness, sensory deficits, visual impairments or nausea. Most of the headaches were limited to one side of the head (63 percent) and pulsated (49 percent). Pain worsened with head movement (31 percent), physical activity (23 percent) and coughing or sneezing (20 percent).

Headache onset occurred within 48 hours before seeking medical treatment in 26 percent of patients, while 54 percent of patients reported having chronic headaches for more than 30 days.

Headache was the most common symptom (84.6 percent) given for seeking medical care among those studied. But almost half those individuals had experienced headaches before, which may have delayed a correct diagnosis.

Another finding was the presence of "thunderclap" headaches – described as very severe and sudden headaches – in 11.4 percent of patients and higher cerebrospinal fluid pressures in these patients as compared to those with severe, but not thunderclap, headaches.

The researchers found that in some CVT patients headaches may be sudden and severe mimicking subarachnoid hemorrhage -- a type of stroke characterized by a blood vessel bleeding into the small space between the membranes surrounding the brain -- or chronic migraine.

In individuals with prior headaches, changes in the characteristics of the headache as well as the presence of neurological signs are important clues to diagnosis, researchers say.

"An accurate diagnosis means patients can receive optimal treatment, including prompt anticoagulant therapy to manage the blood clot, which improves outcomes," says Camargo.

Camargo acknowledges that the small sample size of this study and lack of a control group make the results less generalizable, but believes CVT is underecognized and should be included in the diagnosis of headache in the emergency room. A larger ongoing international study is underway.

Other researchers include Ayrton R. Massaro, M.D., Ph.D.; Luiz A. Bacheschi, M.D., Ph.D.; Marcelo Calderaro, M.D.; Luis O.S.P. Caboclo, M.D.; Fabio I. Yamamoto, M.D. and Milberto Scaff, M.D., Ph.D.

Note: If no author is given, the source is cited instead.

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