Speed of mental operations in fibromyalgia: a selective naming speed deficit

Abnormal processing of information in fibromyalgia may hold clues to brain abnormalities in this illness. The purpose of this study is to examine the speed of mental operations in people with the fibromyalgia syndrome (FMS) under the pressure of time. The central question addresses whether FMS is associated with processing speed deficits across a spectrum of speeded tasks.

Sixty-seven patients with fibromyalgia with a history of memory complaints and 51 controls presenting with complaints of memory loss completed 10 timed cognitive measures of processing speed. Controls were patients with memory complaints who did not have FMS.

The majority of FMS patients (>70%) performed within 1 standard deviation of the norm on 7 or more of 10 speeded measures. However, more than 49% of FMS patients tested as impaired (>1.67 SD below normative mean) on 2 specific validated speed tasks (reading words and naming colors). Compared with controls, the number of FMS patients showing impairment was 2.0 times greater for reading speed, and 1.6 times greater for color naming speed. A mean time delay of 203 milliseconds was recorded for reading words and 285 milliseconds for naming colors in the FMS impaired sample. A 203 milliseconds delay in reading words represents a 48% (203/417) time increase over the normal time for reading the same stimulus word.

Abnormalities in naming speed are an unappreciated feature of FMS. Selective deficits in naming speed in association with otherwise well preserved global processing speed set patients with FMS apart from controls with memory complaints. Clinicians would be wise to specifically request adding a rapid naming test such as the Stroop Test to the cognitive battery; to document cognitive dysfunction in FMS patients who otherwise appear to test normally, despite often intense complaints of memory and concentration difficulties that can affect job performance and increase disability.