Background Fibromyalgia (FM) is characterized by chronic widespread pain. Patients are more sensitive to sensory stimulation regardless of type and modality, suggesting generalized dysfunction in sensory processing. Mismatch Negativity (MMN) is an event-related potential measuring pre-attentive auditory processing.

Objectives The present study aimed to explore pre-attentive auditory processing, which might be affected as a part of generalized sensory processing dysfunction in FM by measuring MMN in FM patients and healthy controls (HC). Also we tried to find an association between MMN parameters and pain sensitivity in FM patients.

Methods Auditory evoked fields were recorded using magnetoencephalography in 18 right-handed female FM patients and 21 age-, sex- and education-matched right handed HC during a duration-deviant auditory oddball paradigm (50-ms standard and 100-ms deviant tones). The magnetic counterpart of the MMN (MMNm) was obtained by subtracting the response to standard stimuli from the response to deviant stimuli. Peak latencies, amplitudes and directional asymmetry coefficient (AC) of the MMNm source were compared between two groups. Pressure pain threshold over the thenar and trapezius muscle was assessed for measuring pain sensitivity.

Results FM patients exhibited reduced MMNm amplitude in the right hemisphere. Rightward asymmetry of MMNm was altered in FM patients indexed by lower AC values. Also, smaller right MMNm amplitude was associated with lower pressure pain threshold of thenar muscle in FM patients.

Conclusions Pre-attentive auditory processing was compromised in FM indexed by reduced MMNm amplitude. This result suggests likelihood of generalized sensory processing dysfunction in FM.

Disclosure of Interest : None declared

DOI 10.1136/annrheumdis-2014-eular.4728