MRI of the central nervous system in MS patients with and without pain

BACKGROUND: Central pain (CP) is a common symptom in MS. Multiple theories are present about the mechanism of CP. Previous studies suggested that lesion of the spinothalamic tract is a necessary condition for development of CP. No previous study has in detail evaluated the association between the specific site of demyelinations and the presence of CP in MS. OBJECTIVE: The study aimed to evaluate the location of plaques in MS patients with CP including a group of MS patients without pain as a reference group. METHODS: All patients underwent a bedside sensory examination and MRI of the brain and spinal cord. MR imaging was acquired on an 1.5Tesla MR equipment. A trained neuroradiologist, blinded to pain status, evaluated the MRI. RESULTS: Thirteen MS patients with CP and 10 MS patients without pain were included. Allodynia and/or dysesthesia were more frequent in pain patients (11/13 vs. 1/10, P<0.01). No difference was found in the number of patients with plaques in spinothalamic tract, dorsal column-medial lemniscus, dorsolateral funiculus, grey substance, thalamus or capsula interna. A non-significantly lower number of pain patients had lesions in thalamo-cortical pathways (8/13 vs. 10/10, P=0.027). CONCLUSIONS: No association between CP and site of demyelinations was found, although a trend toward a higher prevalence of intact thalamo-cortical pathways was seen in pain patients. CP was associated with allodynia, suggesting central hyperexcitability.