Chronic pain common after strokes caused by clots

One in 10 people who have a stroke caused by a clot blocking blood to the brain go on to develop chronic pain, according to a new study.

Researchers found that just over 10 percent of about 16,000 study participants developed chronic pain after their strokes, and that was also linked to a greater risk of physical and mental decline.

While pain has been known to follow strokes, there has been confusion about how many people experience it and whether it causes other health problems.

"It can be confusing for patients, and it can be confusing for clinicians. There can be a disconnect between when you develop the pain and when you had the stroke," said Dr. Martin O'Donnell, the study's lead author from the HRB Clinical Research Facility at the National University of Ireland in Galway.

Estimates for the proportion of people who develop chronic pain after their strokes have ranged from 8 percent to 55 percent. But those numbers were from small studies that used different definitions of pain, O'Donnell and his colleagues write in the journal Stroke.

For the new study, they analyzed data from a large drug trial that tracked over 20,000 stroke patients in 35 countries over 34 months.

Their goals were to determine how common chronic pain is after strokes, to find who is most at risk for it and whether the pain has other long-term consequences.

The new study was funded by drugmaker Boehringer Ingelheim, and four of the authors reported accepting grants from several pharmaceutical companies.

After excluding patients who died, dropped out of the study or reported pain before their stroke, the researchers found that 1,665 of 15,754 remaining stroke patients developed chronic pain.

The most common type of pain reported is known as central post-stroke pain, which leaves people overly sensitive to pain or touch. Usually, it's accompanied by a loss of sensation.

"Weeks or months after the stroke, as the brain heals and develops scar tissue, you can develop pain syndrome exactly where the sensation was lost," O'Donnell said.

Overall, the researchers found that people with more severe strokes, women, users of alcohol or statin drugs, people who were depressed before their strokes and people with diabetes or peripheral artery disease were more likely to report pain.

The researchers note that while many of these traits have been known risk factors for chronic pain after a stroke, it's hard to know why those patients would be more likely to develop the condition and the study did not set out to answer those questions.

People who reported chronic pain also did worse physically and mentally over the study period than those who did not develop pain.

The researchers found that 19 percent of people who developed pain experienced a noticeable decline in mental abilities, compared to 15 percent of those without pain.