Chronic or persistent pain is a common - and likely under-recognized - complication of ischemic strokes (caused by a blocked blood vessel) according to new research in the American Heart Association journal Stroke.

In a large trial of treatments to prevent a second stroke, researchers found that 10.6 percent of more than 15,000 stroke survivors developed chronic pain.

"Chronic pain syndromes are common, even following strokes of mild to moderate severity," said Martin J. O'Donnell, M.D., lead author and professor of translational medicine at the National University of Ireland in Galway and associate clinical professor at McMaster University in Hamilton, Ontario, Canada. "It is associated with greater decline in physical and cognitive function, making it an important medical complication after stroke."

Researchers examined data on 15,754 people who had survived mild to moderate strokes and were followed for an average 30 months in PRoFESS (Prevention Regimen for Effectively Avoiding Second Strokes), the largest study to determine the prevalence of chronic pain after ischemic stroke.

Of the 1,665 stroke survivors reporting chronic pain beginning after their stroke:

• 431 (2.7 percent) were classified as having central stroke pain, which is due to injury to the brain caused by stroke that can present as touch, temperature or other sensations being perceived as pain. Previous research has shown that central post-stroke pain may not manifest for many months after stroke has occurred, O'Donnell said.
• 238 (1.5 percent) had peripheral neuropathic pain, a tingling, burning or shooting pain due to damage to nerves outside the brain and spinal cord
• 208 (1.3 percent) reported pain from continuously tight or stiff muscles also called spasticity
• 136 (0.9 percent) experienced shoulder pain caused by stroke-related weakness or spasticity
• 86 (0.6 percent) said they had more than one type of pain
• 739 (4.7 percent) reported other causes of pain, or had unclassified pain syndromes.

Significant risk factors for post-stroke pain included increased severity of stroke; female gender; greater alcohol intake; recent symptoms of depression; diabetes and vascular disease of blood vessels supplying the lower limbs.

Patients who developed post-stroke chronic pain were more than twice as likely to become more dependent during the follow-up period, than those whose recovery wasn't complicated by pain. Patients with non-central causes of pain were more likely to experience cognitive decline.

"We suspect that some of the association between chronic pain and decline in cognitive test performance may be related to the use of medications to treat pain, but this was not evaluated in our study" said O'Donnell. "Our study emphasizes the importance of evaluating interventions to prevent post-stroke pain in high-risk individuals."