Sensory components facilitating jaw-closing muscle activities in the rabbit

Summary The role of oral and facial sensory receptors in the control of masticatory muscle activities was assessed from the effect of acute deafferentiation on cortically induced rhythmic jaw movements (CRJMs) in anesthetized rabbits. When a thin polyurethane-foam strip (1.5, 2.5 or 3.5 mm thick) was placed between opposing molars during CRJMs, masseteric activities were facilitated in association with an increase in the medial excursion of the mandible during the power phase. The effects varied with the pattern of CRJMs, and the rate of facilitation was greater for small circular movements than for the crescent-shaped movements. Furthermore, the response of the masseter muscle was greater in the anterior half of the muscle, where muscle spindles are most dense, than in its posterior half. It was also demonstrated that the response increased with an increase in the thickness of the test strip. In contrast, the activities of the jaw-opening muscle were not affected significantly. The duration of masseteric bursts increased during application of the test strip and the chewing rhythm tended to slow down. However, the latter effect was not significant. After locally anesthetizing the maxillary and inferior alveolar nerves, the facultative responses of the masseter muscle to the test strip was greatly reduced but not completely abolished. Lesioning of the mesencephalic trigeminal nucleus (Mes V) where the primary ganglion cells of muscle spindle afferents from jaw-closing muscles and some periodontal afferents are located, also reduced the facilitative effects. Similar results were obtained in the animals with the kainic acid injections into the Mes V 1 week before electrical lesioning of this nucleus. In these animals the effects of electrical lesioning of the Mes V could be attributed to the loss of muscle receptor afferents since the neurons in the vicinity of the Mes V were destroyed and replaced by glial cells, whereas the Mes V neurons are resistant to kainic acid. When electrical lesioning of the Mes V and sectioning of the maxillary and inferior alveolar nerves were combined in animals with a kainic acid injection into the Mes V, the response of the masseter muscle to application of the strip was almost completely abolished. From these findings, we conclude that both periodontal receptors and muscle spindles are primarily responsible for the facilitation of jaw-closing muscle activities. Furthermore, it is suggested that the transcortical loop may not be the only path producing this facilitation since similar effects were induced in animals with ablation of the cortical masticatory area (CMA), when the test strip was placed between the molars during rhythmic jaw movements induced by pyramidal tract stimulation.     

Converging patterns of inputs from oral structures in the postcentral somatosensory cortex of conscious macaque monkeys

Single neuronal activities were recorded in the oral region of the postcentral gyrus in conscious Japanese monkeys. Among 5,756 neurons isolated, receptive fields (RFs) and submodalities were identified in 1,502 neurons in area 3b, 970 in area 1, and 1,461 in area 2. The relative incidence of neurons that had bilateral RFs increased gradually upon moving caudally from area 3b to area 2 (bilateral integration). A total of 276 neurons had bimaxillary RFs covering both the maxillary and mandibular divisions of the trigeminal nerve, such as the upper and lower lips, upper and lower teeth, palate and tongue, or combinations thereof. There was also a tendency for the relative incidence of neurons with bimaxillary RFs to increase across the postcentral gyrus but with an abrupt change in area 2 (bimaxillary integration). A total of 382 neurons had composite RFs covering more than one of five oral structures: lip, cheek mucosa, teeth/gingiva, tongue, and palate. The relative incidence of neurons with composite RFs was significantly higher in area 2 than in areas 3b and 1 (interstructural integration). These results indicate that the convergence of inputs from oral structures proceeds in a hierarchical manner across the postcentral gyrus, but chiefly in area 2 for the bimaxillary and interstructural integrations. The relative incidence of neurons with composite RFs was higher among neurons associated with the teeth/gingiva or palate than among neurons associated with the tongue or lip in all three areas. We interpret this to mean that anatomical or functional differences between oral structures might be reflected in the converging patterns in the oral representation.     

Trigeminal neuropathy and partial nose destruction

Summary Two cases of trigeminal neuropathy with tissue loss are described, one in a Spillane-Wells syndrome, the other in a Riley-Day syndrome. Although the etiology was different, nose-picking led in both cases to a typical punchedout lesion of the skin and cartilage of nose tip, columella and alae nasi. Reconstruction was performed only in the first case, after resolution of the neuropathy. Reconstruction should not be considered for cases with persistant anaesthesia.Head: M. Lejour     

局部药物注射与口服药治疗三叉神经痛的疗效对比

目的：观察局部注射药物与口服药治疗三叉神经痛的疗效差异。方法：选择门诊三叉神经痛的患者,并随机分成两组,即口服药物组给予卡马西平100mg1-2次/天,若不能止痛每天增加100mg ,直到控制疼痛为止,将最小有剂量作为维持量,一般为600-800mg/d,共36例。局部药物注射组以4%氢羟强的松龙0.5ml加2%利多卡因1.5ml混合后准确地注射到罹患神经通过的骨孔处,共32例。结果：口服药物组6个月有效27例,有效率75%,局部药物注射组6个月有效30例,有效率94%。结论：局部药物注射组的疗效明显优于口服药物组。     

阿霉素注射神经干治疗原发性三叉神经痛

对 6 8例原发性三叉神经痛患者施行阿霉素神经干注射治疗。全部病例均在术后 2周内三叉神经痛症状消失 ,其中 6 3.2 %在术后 2 4h内痛疼消失 ;2 8.9%在术后 1周内疼痛消失 ;7.9%在术后 2周内疼痛消失。随访结果显示 ,3年内复发率为 10 .3% ,3～ 5年复发率为 15 .4%。该方法具有复发率低、疗效肯定、安全、微创等特点。     

Endoscopic-assisted microvascular decompression for trigeminal neuralgia secondary to vertebrobasilar dolichoectasia: A case report

Introduction and importanceTrigeminal neuralgia (TN) secondary to vertebrobasilar dolichoectasia (VBD) was a rare condition. This paper reported a successful endoscopic-assisted microvascular decompression (MVD) for TN secondary to VBD.Case presentationA 53-year-old male with a history of myocardial infarction and heart failure complained of left refractory facial pain three years prior to admission. His pain was intermittent, electrical-like, severe, sharp, and radiated along the maxillary and mandibular branches. He used carbamazepine 600 mg daily. Brain magnetic resonance imaging revealed a neurovascular conflict between VBD and the left trigeminal nerve. The endoscopic-assisted MVD was indicated. The shredded neurosurgical sponges were interposed between VBD and trigeminal nerve. The 0° and 30° rigid rod-lens endoscope was used to explore and confirm the complete decompression. Postoperatively, TN was disappeared entirely. At a three-month postoperative, no facial pain and paraesthesia were found. The patient discontinued carbamazepine permanently.Clinical discussionMVD was still the most effective treatment. An inspection of root entry zone (REZ) and complete MVD with a solely operating microscope were challenging due to the massive diameter of VBD and multiple offending arteries behind the VBD. However, the wide viewing field and high-quality resolution of endoscopes allowed better visualization of REZ and neurovascular conflicts behind neural structures and least cerebellar retraction. This is essential in case of less potential space created by VBD.ConclusionEndoscope-assisted MVD allowed better visualization of REZ and neurovascular conflicts behind neural structures and least cerebellar retraction in management of trigeminal neuralgia secondary to VBD.     

Epileptiform activity in the somatosensory cortex of rats with trigeminal neuralgia

Laboratory of Pathophysiology of Pain, Research Institute of General Pathology and Pathological Physiology, Russian Academy of Medical Sciences, Moscow. Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 114, No. 8, pp. 126–128, August, 1992.     

CT在三叉神经瘤诊断中的价值

目的探讨CT在三叉神经瘤诊断中的价值。方法搜集经手术和病理学证实的三叉神经瘤12例,行CT平扫及静脉注射60％泛影葡胺或优维显增强扫描。结果12例中表现为特征性哑铃形3例,类哑铃形6例,类圆形3例。肿瘤呈混杂密度、均匀密度或等密度,均无钙化及水肿。结论CT对三叉神经瘤的定位、定性及岩骨和颅底骨的异常改变具有重要的诊断价值。     

Metformin use and the risks of herpes zoster and postherpetic neuralgia in patients with type 2 diabetes

Herpes zoster and postherpetic neuralgia cause substantial pain in patients. Persons with type 2 diabetes (T2D) are prone to zoster infection and postherpetic neuralgia due to compromised immunity. We conducted this study to evaluate the risks of herpes zoster and postherpetic neuralgia between metformin users and nonusers. Propensity score matching was utilized to select 47 472 pairs of metformin users and nonusers from Taiwan's National Health Insurance Research Database between January 1, 2000, and December 31, 2017. The Cox proportional hazards models were used for comparing the risks of herpes zoster and postherpetic neuralgia between metformin users and nonusers in patients with T2D. Compared with no-use of metformin, the adjusted hazard ratios (95% confidence interval) for metformin use in herpes zoster and postherpetic neuralgia were 0.70 (0.66, 0.75) and 0.510 (0.39, 0.68), respectively. A higher cumulative dose of metformin had further lower risks of herpes zoster and postherpetic neuralgia than metformin no-use. This nationwide cohort study demonstrated that metformin use was associated with a significantly lower risk of herpes zoster and postherpetic neuralgia than metformin no-use. Moreover, a higher cumulative dose of metformin was associated with further lower risks of these outcomes.