Nondermatomal somatosensory deficits in chronic pain are associated with cerebral grey matter changes.

OBJECTIVES: Widespread sensory deficits occur in 20-40% of chronic pain patients on the side of pain, independent of pain aetiology, and are known as nondermatomal sensory deficits (NDSDs). NDSDs can occur in absence of central or peripheral nervous system lesions. We hypothesised that NDSDs were associated with cerebral grey matter changes in the sensory system and in pain processing regions, detectable with voxel-based morphometry. METHODS: Twenty-five patients with NDSDs, 23 patients without NDSDs ("pain-only"), and 29 healthy controls were studied with high resolution structural MRI of the brain. A comprehensive clinical and psychiatric evaluation based on Diagnostic and Statistical Manual was performed in all patients. RESULTS: Patients with NDSDs and "pain-only" did not differ concerning demographic data and psychiatric diagnoses, although anxiety scores (HADS-A) were higher in patients with NDSDs. In patients with NDSDs, grey matter increases were found in the right primary sensory cortex, thalamus, and bilaterally in lateral temporal regions and the hippocampus/fusiform gyrus. "Pain-only" patients showed a bilateral grey matter increase in the posterior insula and less pronounced changes in sensorimotor cortex. CONCLUSIONS: Dysfunctional sensory processing in patients with NDSDs is associated with complex changes in grey matter volume, involving the somatosensory system and temporal regions.

Bilateral Sensory Changes and High Burden of Disease in Patients With Chronic Pain and Unilateral Nondermatomal Somatosensory Deficits: A Quantitative Sensory Testing and Clinical Study.

OBJECTIVES: Widespread sensory deficits resembling hemihypoesthesia occur in 20% to 40% of chronic pain patients on the side of pain, independent of pain etiology, and have been termed nondermatomal sensory deficits (NDSDs). Sensory profiles have rarely been investigated in NDSDs. MATERIALS AND METHODS: Quantitative sensory testing according to the protocol of the German Research Network on Neuropathic Pain (DFNS) was performed in the face, hand, and foot of the painful body side and in contralateral regions in chronic pain patients. Twenty-five patients with NDSDs and 23 without NDSDs (termed the pain-only group) were included after exclusion of neuropathic pain. Comprehensive clinical and psychiatric evaluations were carried out. RESULTS: NDSD in chronic pain was associated with high burden of disease and more widespread pain. Only in the NDSD group were significantly higher thresholds for mechanical and painful stimuli found in at least 2 of 3 regions ipsilateral to pain. In addition, we found a bilateral loss of function for temperature and vibration detection, and a gain of function for pressure pain in certain regions in patients with NDSD. Sensory loss and gain of function for pressure pain correlated with pain intensity in several regions. DISCUSSION: This may indicate a distinct sensory profile in chronic non-neuropathic pain and NDSD, probably attributable to altered central pain processing and sensitization. The presence of NDSD in chronic non-neuropathic pain may be regarded as a marker for higher burden of pain disease.