Diagnostic utility of deep tendon reflex responses in rectus femoris and triceps brachii in fibromyalgia: a clinical and electrophysiological study.

The aim of this study was to evaluate deep tendon reflex responses and associated electrophysiological parameters of the muscles in patients with fibromyalgia. This cross-sectional study included 38 patients with fibromyalgia and 32 age- and sex-matched controls. Deep tendon reflexes of the rectus femoris and triceps brachii were tested using a reflex hammer. Electromyographic (amplitude and duration of activation), inertial measurement unit (angular velocity, acceleration), and electromechanical (delay) analyses were performed using a surface electromyography (sEMG) device. Comparative analyses were carried out between patients and controls. Additionally, Receiver Operating Characteristic (ROC) analysis was performed to evaluate the ability of hyperreflexia in distinguishing fibromyalgia patients from controls. Hyperactive deep tendon reflexes in the right/left rectus femoris and/or triceps brachii were observed in more than 85% (ranging from 86.8 to 94.7%) of the fibromyalgia group. Patients with fibromyalgia exhibited significantly increased deep tendon reflex responses compared to controls (p < 0.001). Patients revealed significantly higher amplitude, longer duration of muscle activation, greater sagittal acceleration and angular velocity, and shorter electromechanical delay. Normalized muscle activation (right and left rectus femoris and right triceps brachii) in response to deep tendon reflex test showed acceptable ability in differentiating fibromyalgia patients from controls (Area under curve (AUC) = 0.890, 0.784 and 0.782, respectively). For the right rectus femoris, values ≤ 28.3 (clinically corresponding to normoactive/hypoactive deep tendon reflexes) appeared to rule-out fibromyalgia with 94.1% sensitivity and 61.3% specificity. Patients with fibromyalgia exhibit increased deep tendon reflex responses. Normal or decreased deep tendon reflex responses may probably be used as a rule-out criterion for fibromyalgia.