Phenotyping Pain in Patients With Fibrous Dysplasia/McCune-Albright Syndrome.

CONTEXT: Pain is a poorly managed aspect in fibrous dysplasia/McCune-Albright syndrome (FD/MAS) because of uncertainties regarding the clinical, behavioral, and neurobiological underpinnings that contribute to pain in these patients. OBJECTIVE: Identify neuropsychological and neurobiological factors associated with pain severity in FD/MAS. DESIGN: Prospective, single-site study. PATIENTS: Twenty patients with FD/MAS and 16 age-sex matched healthy controls. INTERVENTION: Assessments of pain severity, neuropathic pain, pain catastrophizing (pain rumination, magnification, and helplessness), emotional health, and pain sensitivity with thermal quantitative sensory testing. Central nervous system (CNS) properties were measured with diffusion tensor imaging, structural magnetic resonance imaging, and functional magnetic resonance imaging. MAIN OUTCOME MEASURES: Questionnaire responses, detection thresholds and tolerances to thermal stimuli, and structural and functional CNS properties. RESULTS: Pain severity in patients with FD/MAS was associated with more neuropathic pain quality, higher levels of pain catastrophizing, and depression. Quantitative sensory testing revealed normal detection of nonnoxious stimuli in patients. Individuals with FD/MAS had higher pain tolerances relative to healthy controls. From neuroimaging studies, greater pain severity, neuropathic pain quality, and psychological status of the patient were associated with reduced structural integrity of white matter pathways (superior thalamic radiation and uncinate fasciculus), reduced gray matter thickness (pre-/paracentral gyri), and heightened responses to pain (precentral, temporal, and frontal gyri). Thus, properties of CNS circuits involved in processing sensorimotor and emotional aspects of pain were altered in FD/MAS. CONCLUSION: These results offer insights into pain mechanisms in FD/MAS, while providing a basis for implementation of comprehensive pain management treatment approaches that addresses neuropsychological aspects of pain.