Abstract: 【Abstract】 Objective To investigate the application value of the contact heat evoked potential (CHEP) for the trigeminal small-fiber dysfunction in patients with diabetes mellitus. Methods Heat stimuli was delivered to the skin above the eyebrow with a contact heat stimulator in 46 diabetic patients and 20 normal subjects. The peak latency of the negative component and the peak-to-peak amplitude of CHEP was recorded at the vertex (Cz). Blink reflex (BR) and direct electrical stimulation of the facial nerve were performed in the same side. The patients with diabetes mellitus were divided into the group with normal conduction (DMN group) and the group with abnormal conduction (DMA group) according to the results of the nerve conduction of the limbs. Results In DM group and the control group, the peak latency of the negative component of CHEP was (382.7±36.8) ms vs (342.2±20.8)ms (t=5.465, P=0.000), the common logarithm of the peak-to-peak amplitude of CHEP was (1.66±0.21) vs (1.84±0.24) (t=2.922, P=0.005). There were no statistical differences between two groups in the latencies of R1、R2、R2′ in BR and R/D ratio(the latency of R1/ the latency of direct electrical stimulation of the facial nerve); The peak latency of the negative component of CHEP in DMN group was longer than that of the control group. The common logarithm of the peak-to-peak amplitude of CHEP was lower in DMA group than that of DMN group. Conclusion Limb nerves may be involved in patients with diabetic neuropathy, the trigeminal nerve can also be involved coexistence of limb nerve injuries; The trigeminal small-fiber dysfunction may occur when BR or nerve conduction of the large myelinated nerve was normal, and becomes obvious when the former was abnormal. CHEP has potential clinical application value in the evaluation of the cranial nerve small-fiber function in patients with diabetes mellitus .

Key words: Diabetes mellitus, Trigeminal nerve, Evoked potentials, Blink reflex