Numbered Pain Scales More Complicated for Patients With Migraine, Study Says

Some types of pain affect cognitive ability, including number sense, and yet some tools to assess pain use numerical scales. A recent study sought to determine if number sense is altered in patients with chronic and acute pain compared with healthy subjects.

If the impairment of number sense does impact pain assessment, the researchers hypothesized, the validity of using number-based tools to evaluate pain intensity would need to be re-evaluated.

Pain intensity is typically measured through verbal rating (VRS), numerical rating (NRS), and visual analog scales (VAS); these all require spatial cognition. Prior work has shown that chronic pain may lead to a deficit in memory and attention, the authors said. These skills are needed for number sense, they noted, calling it a “cognitive ability essential for spatial-numerical processing, such as the assessment of numerical value and measurements of scale sizes.”

Some reports indicate number sense may be impaired in patients with chronic pain.

In this study, researchers examined patients with migraines (the chronic pain group) with those with post-orthopedic pain (the acute pain group) and controls; 150 participants were divided equally into the 3 groups.

Characteristics included age, education, sex, and handedness (right or left). This study was conducted in Iran, and all subjects were recruited from Persian-speaking people who were fluent in Farsi. Those with migraine had had pain for at least 12 months and the acute pain group had undergone orthopedic surgery within the past 24 hours.

Pain intensity was measured with numeric and verbal rating scales as assessment tools. Number sense was assessed using number naming, number marking, and line bisection tasks. Researchers noted the deviation from correct answers for each task, and used 2 experiments methods to evaluate each participant.

One experiment included number marking and number naming tasks to measure abilities to transform abstract numbers into spatial representations on a direct line, similar to a VAS. The second, called a line-bisection task, measured the ability to accurately recognize spatial-numerical processes.

Number sense was evaluated by line bisection, number marking, and number naming tasks for all 3 groups.

Results showed that patients in the migraine, group had higher pain intensity scores than the acute pain group, as measured by the line bisection task. However, number naming or number marking was not significantly different compared with those with acute pain.

This suggests that these patients may use number-based pain assessment tools differently than other patients, the authors said.

Reference

Majedi H, Mohammadi M, Tafakhori A, Khazaeipour Z. The influence of chronic pain on number sense and numeric rating scale: A prospective cohort study. Anesth Pain Med. Published online May 5, 2020. doi: 10.5812/aapm.103532