FUNCTIONAL MAGNETIC RESONANCE IMAGING OF THE SPINAL CORD IN PAINFUL DIABETIC NEUROPATHY

ABSTRACT Diabetic neuropathy, a secondary complication of diabetes mellitus, is often first characterized by allodynia, hyperalgesia, or spontaneous pain. The mechanism by which diabetes alters pain transmission is not well understood, but recent evidence suggests spinal cord involvement. Behavioural studies have shown that streptozotocin (STZ) induced diabetic rats exhibit hyperalgesia. Functional magnetic resonance imaging (fMRI) was used to compare activity in the spinal cord upon noxious electrical stimulation (15 V, 0.3 ms, 0.3 Hz) of the hind paw in STZ-induced diabetic and control rats (7-8 mA). Experiments were conducted on rats one month following STZ injection (n=4) and healthy age-matched controls (n=4). Diabetic rats were smaller, hyperglycaemic, and had lower blood pH than control animals. FMRI activity at the lumbar enlargement of the spinal cord was observed in both control and diabetic animals in the dorsal horn ipsilateral to stimulus. Control animals exhibited greater fMRI activity in the contralateral dorsal horn, and ipsilateral and contralateral ventral horn, and had a higher percentage signal change compared to diabetic rats. The results of this study are consistent with reports that primary afferent input to the spinal cord is diminished by diabetes, and suggest fMRI may be useful in early detection of diabetic neuropathy. iii ACKNOWLEDGMENT