Certain Cognitive-Function Deficits May Raise Risk for Chronic Pain

Patients with deficits in attention, memory, or executive function might be at greater risk of developing chronic pain after surgery or another pain-related event.

So suggests a study published online January 17 in Brain, led by Nadine Attal, M.D., Ph.D., of the Center for the Evaluation and Treatment of Pain at Hospital Ambroise Pare in Boulogne-Billancourt, France.

The study cohort included 189 subjects aged 18 to 85 who were about to undergo either knee replacement because of osteoarthritis or breast cancer surgery. Both procedures are common, and for each there is a risk of postsurgical pain. The scientists measured attention, memory, and executive function in the subjects before surgery, then at a one-year follow-up.

In the knee replacement group, 84 percent had clinically meaningful pain before surgery, but only 39 percent and 38 percent had it at six and 12 months after surgery, respectively. In the breast cancer surgery group, none had clinically meaningful pain before surgery, but 20 percent and 18 percent, respectively, had it six and 12 months after surgery.

Impairment in attention, memory, or executive function before surgery significantly predicted clinically meaningful pain six or 12 months after surgery in both groups of patients, even when the presence of anxiety, depression, or pain before surgery was considered.

The researchers were not surprised to find such an association, they indicated, since fMRI imaging findings have shown that brain regions involved in attention, memory, and executive function—notably the prefrontal cortex and anterior cingulate cortex—are also involved in pain modulation. And “interestingly,” they noted, “these areas have also been implicated in mood and anxiety disorders, both of which are frequently comorbid with chronic pain.”

“Our findings suggest that patients with deficits of executive function or memory as a result of brain conditions, such as Parkinson’s disease, brain trauma, Alzheimer’s disease, or mild cognitive impairment, would be at higher risk of developing chronic pain after a painful event, such as surgery,” Attal and colleagues concluded.

“This is an interesting study,” Michael Clark, M.D., an associate professor of psychiatry and director of the Pain Treatment Program at Johns Hopkins Medical Institutions, said in an interview with Psychiatric News. “I think that the determination of risk factors that predict the development of chronic pain is an important area. . . . [The results] highlight the need to take extra care in the management of acute pain for individuals with existing neurological disorders to decrease the risk of persistent pain after surgery. In addition, given that chronic pain management often focuses on improving coping skills, these results support the use of cognitive training to facilitate the development of more effective therapies for reaching functional goals in rehabilitation programs.”

“While exploratory, these results suggest that impaired neuropsychological functioning, often associated with aging, may be a marker of risk for prolonged postsurgical pain,” Jordan Karp, M.D., an associate professor of psychiatry, anesthesiology, and clinical and translational science at the University of Pittsburgh, told Psychiatric News. “Impaired mental flexibility and memory may indicate increased risk for central sensitization, which can be understood as plastic changes in the brain and spinal cord that lead to abnormal modulation of descending inhibition and worsened experience of pain. The results possibly suggest that worse executive functioning and memory problems may put patients at greater risk—perhaps because of impaired problem-solving skills or trouble remembering post-op instructions—of poor acute pain control, reduced effort at rehabilitation, and impaired pain self-management, all of which may increase the risk of converting an acute pain experience into a chronic pain problem.”

The study was funded by the French Society of Pain-Janssen-Cilag. ■

An abstract of “Does Cognitive Functioning Predict Chronic Pain? Results From a Prospective Surgical Cohort” is posted at http://brain.oxfordjournals.org/content/early/2014/01/17/brain.awt354.abstract.