The Analysis Of Trigeminal Somatosensory Evoked Potentials In Patients With Trigeminal Neuralgia

Objective:Trigeminal nerve is one of the main nerve to manipulate the feelings and movement of the maxillofacial region.TN refers to the lightening pain in the distribution of the trigeminal nerve, this kind of pain last for a few seconds or a few minutes and without any symptom during intermission, the pain course can be periodical attack, the attack may be spontaneously stimulated or can be triggered by the trigger point. There can be positive signs in the neurologic examination. Trigeminal somatosensory evoked potential (TSEP) refers to the nerve impulse produced by stimulating the trigeminal nerve distribution area of the skin and mucous membrane receptors, we can record the potential arising from the trigeminal nerve branches in cortex, it can reflect in or around the branches of the trigeminal nerve lesions by recording the P1, N1, P2, N2, P3, N3, P4, N4, P5, N5 ten positive and negative waves. Now when we diagnosed TN in clinic, mostly depend on the main complaint by the patient. There is still no quantitive indexes to diagnose TN and this brings too much difficulties to the clinic, this research aims to study the characteristic of the somatosensory of the TN and the effects of the operation or medicine on the TSEP in order to offer some kind of evidence in clinic.Methods:We selected several cases from the patients who are diagnosed with TN during the year 2009 to 2010, including 21 men and 37 women, aged 29～83 years old, The average age was 60.8±5.6 years old, All of these patients are in accordance with the following conditions:①No medically contributory select;②Without the trigeminal nerve and facial nerve injury history;③Without major diseases;④No surgical or traumatic history on skull or maxilla and mandible. The machine is DISA-2000M oculomusclar electromyogram made by Danmark, A comparision should be made with the normal values of TSEP in healthy people. We divided the third branch of TN into two groups:the elderly group(≥60)21 cases and the mid-aged group(36～59) 15 cases according to age. We divided the healthy people into the elderly control group (≥60) 21 cases and the mid-aged control group (36～59) 15 cases. The comparison should be made between the unaffected side and the affected side in the elderly group of TN, so was in the mid-aged group of TN. The comparision should also be made between the elderly group of TN and the elderly group in the control group, also between the mid-aged group of TN and the mid-aged group in the control group. There was a statistical significance when P<0.05 occurred.Results:(1)TSEPs in TN patients of the unaffected sides showed the same waveform as those on healthy people, But TSEPs on TN patients of the affected sides showed the latency prolongation or lost and the peak waveform forward.(2) There was a significant difference between the unaffected side and affected side in latency P1(P=0.037),N1(P=0.005) and N3P4 Amp (P=0.049) in senior patients. There was a significant difference between the unaffected side and affected side in latency P3 (P=0.05) in mid-aged patients.(3) P1(P=0.018), P3 (P=0.023),P1N1 (P=0.008),P2N2 (P=0.033),N2P3 P=(0.043),N3P4 P=(0.043),P5N5 (P=0.031) have shown the great significance between the healthy people and the TN patients in senior group. In midlife group, only P3 and P3N3 Amp showed the significant difference.(4) The waveform of TSEPs in the patients who undergo the avulsion of the mandibular nerve few months ago have been showed two kinds of characterristics of the waveforms, one of which is the disappear of the waveforms and the other is the irregular of the TSEP.(5) The TSEP in patients who have been taken Carbamazepine to ease the pain attack before the examination could also showed the different characteristic with that of the patients who have taken nothing before the test, the TSEP waveform of these people become unstable. The TSEP in patient who have a taken medicine history but take no medicine before the test show the same characteristic as that of TN.Conclusion:This research can be very valuable to clinician in the diagnoses of the trigeminal neuralgia. P1,N1 in elderly group with TN could be delayed or could be lost in some cases.The peak of the waveform could also be forward. P3 could be delayed in mid-aged group with TN, The peak of the waveform could also be forward. The characteristic of the unaffected side is the same of that in normal people. TSEP on unaffected sides could be used as a normal standard to compares with that on affected sides. In clinical practice we should take age,symptoms and other factors into consideration when diagnose whether a disease is TN or not.