Subclinical sensory abnormalities in trigeminal neuralgia

Trigeminal neuralgia is considered as a paroxysmal single nerve phenomenon. Abnormal sensory perception has been previously described in 15-25% of patients with clinical examination. Quantitative sensory testing (QST) was used to evaluate sensory perception in patients with idiopathic trigeminal neuralgia (ITN). Nine patients and 10 normal control subjects were evaluated in all six trigeminal branches. QST abnormalities were found in the symptomatic division and in the other two branches on the same side. Minor contralateral changes were also found. Differences consisted of cold and warm hypoaesthesia and higher cold and heat pain thresholds in patients. All differences proved statistically significant. Our findings suggest that trigeminal neuralgia is not only a paroxysmal single nerve disorder, but also that other higher structures may be involved.     

Idiopathic trigeminal pain associated with gustatory stimuli

We present a unique case of a patient with facial pain evoked by gustatory stimuli. Pain was typically evoked by application of sucrose to the ipsilateral anterior 2/3 of the tongue, but not to the contralateral aspect. Pain was referred to the maxillary tuberosity area and, when stronger, to the infraorbital and supraorbital regions. Sucrose was most effective in eliciting pain, whilst saline, citric acid and water had a minimal effect. Spatial or temporal summation of gustatory stimuli was associated with stronger pain of longer duration and shorter latency. Some of the pain characteristics were similar to those of idiopathic trigeminal neuralgia. Thus, pain was elicited by innocuous ipsilateral stimuli, referred out of the stimulus zone, persisted beyond the period of stimulation and could be controlled with carbamazepine. We proposed a central neural mechanism for pain induction with convergence between gustatory stimuli afferents and pain pathways in the trigeminal system.     

Sumatriptan alleviates pain in patients with trigeminal neuralgia

OBJECTIVES: Arterial compression of the trigeminal root may lead to trigeminal neuralgia. 5-HT1B/1D receptor agonists may inhibit vasodilation and inflammation near the irritated trigeminal root. A recent study showed attenuation of mechanical allodynia by a 5-HT1A receptor agonist in a rat model of trigeminal neuralgia. The present study examined the effectiveness of a 5-HT1A/1B/1D receptor agonist, sumatriptan, on pain relief in patients with trigeminal neuralgia. METHODS: The study was conducted in 15 patients with idiopathic trigeminal neuralgia. The patients had been suffering from painful paroxysms for at least 1 month. Each patient was injected with 1 mL of saline subcutaneously (placebo), followed 15 minutes later with subcutaneous sumatriptan (3 mg in 1 mL saline). This was followed the next day by oral sumatriptan (50 mg twice daily) for 1 week. RESULTS: The visual analog scale did not change after saline, but significantly decreased after subcutaneous sumatriptan. Both 1 week after oral sumatriptan and 1 week after discontinuation of the drug, visual analog scale scores resulted in a significant decrease from the baseline. Adverse events after subcutaneous sumatriptan occurred in 4 patients: fatigue in 4 and nausea in 2. Side effects from the oral medication appeared in 4 patients: fatigue in 2, nausea in 1 and chest discomfort in 1. These side effects subsided soon after discontinuation of sumatriptan. CONCLUSIONS: Our results indicate that subcutaneous injection followed by oral administration of sumatriptan produces prompt and continuous analgesia in patients with trigeminal neuralgia.     

Dental trigeminal neuralgia

INTRODUCTION: Although the majority of patients with recurrent hyperalgesia of the nervus trigeminus may benefit from drug treatment or invasive (thermocoagulation) and other surgical interventions, a minority of patients does not respond to these strategies. Hence, unusual etiologies must be taken into consideration. CASE REPORT: Mrs F., a 74-year-old women suffered from acute left-side trigeminalgia ten days after receiving a new dental prosthesis (upper jaw). Intensive pain attacks occurred spontaneously when she was speaking and could also be evoked by gentle exogenous pressure at the upper lip. INTERVENTION: The painful area has been identified by careful clinical evaluation. Local administration of antibiotics combined with laser coagulation successfully cured the trigeminalgia after 4 weeks which did not recur in the follow-up period over 2 months. CONCLUSION: Since patients longer history revealed pain attacks of minor severity we suggest that local inflammation at the gingiva might have stimulated quiescent nociceptors over time. The local pressure to this area evoked by the new prosthesis seems to be definitive trigger factor to intensify the nociceptor response resulting in higher number of trigeminalgia attacks of marked severity. We therefore conclude that differential diagnosis of symptomatic trigeminalgia should include dental gingival mechanisms at least in a case exhibiting resistances to other treatment.     

Petrous angle and trigeminal neuralgia

The angle of the petrous portion of the temporal bone was measured at the site where it is crossed by the trigeminal nerve. Measurement was facilitated by using the impression techniques of dentistry to produce a plaster model of the bone, and the model was then sawn across to show the angle clearly. Considerable variation was found. Certain bone irregularities were observed and these could also conceivably be factors in the causation of trigeminal neuralgia. An attempt to reveal the angle of the petrous bone by radiology was successful in some cases but not in others. Further investigation along these lines might be of value in patients suffering from idiopathic trigeminal neuralgia.     

McGill疼痛问卷在三叉神经痛诊断和治疗中的应用

目的:通过采用McGill疼痛问卷(McGill pain questionnaire,MPQ)鉴别三叉神经痛,并观察射频热凝术的疗效,研究MPQ在面痛诊断上的重要性。方法:本研究共观察159例三叉神经痛患者,其中136例患有典型三叉神经痛(CTN),23例患有混合型三叉神经痛(MTN)。采用MPQ评估患者的疼痛,并观察其中124例术后患者疼痛的缓解情况。结果:CTN组的平均现有疼痛强度(PPI)值为4.20±0.34,MTN组的平均PPI值为3.50±0.57,明显低于CTN组(P0.001);与MTN患者相比,CTN患者在疼痛分级指数(PRI)-感觉项上报告了更高的强度(P0.001);两组间PRI-情感和PRI-评价项上有明显区别,CTN组的得分更高(P0.001);RFT术后CTN患者显示了高的立即疼痛缓解率,达到93.6%。MTN患者的结果没有CTN组的好,只有58.8%的患者疼痛明显缓解。结论:MPQ可以很好鉴别不同类型的三叉神经痛,鉴于射频热凝治疗两种三叉神经痛疗效的差异,使用MPQ在面痛诊断中有重要意义。     

Effect of adrenergic receptor activation on post-herpetic neuralgia pain and sensory disturbances

Patients with acute herpes zoster, and to a lesser extent post-herpetic neuralgia (PHN), have been reported to respond to local anesthetic blockade of the sympathetic nervous system. In animal models of nerve injury, local injection of adrenergic agonists after nerve injury, but not before, excites nociceptors. In some patients with chronic neuropathic pain, local application of norepinephrine evokes pain. In 15 subjects with PHN, the role of adrenergic receptors in PHN pain was assessed in a two-session double blind study comparing the response to cutaneous infiltration of epinephrine or phenylephrine (30 μg in 3 ml) with the response to normal saline in both the painfully affected skin and mirror-image normal skin. Two adjacent sites were studied on each side of the body, one site for injection and the other for measuring sensory effects of the injection. In the morning part of each session, mirror-image normal skin was injected. In the afternoon portion of each session, skin in the most painful area affected by PHN was injected. Injection of saline or the adrenergic agonist in normal skin produced mild and transient pain without development of allodynia and without affecting overall PHN pain intensity. In PHN skin, injection of saline and the adrenergic agonist produced an equivalent degree of transient pain that was slightly greater than injection into mirror-image normal skin. After injection of the adrenergic agonist into PHN skin, both overall PHN pain and allodynia severity were significantly greater than after saline injection, peaking at 10–15 min post-injection. Even when PHN has been present for years, adrenergic receptor stimulation in PHN skin increases pain, most likely through direct activation of C-nociceptors in the painful skin. Increased allodynia is most likely mediated centrally and driven by the increase in C-nociceptor input.     

Post-herpetic neuralgia: the relation of pain complaint, sensory disturbance, and skin temperature

Twelve otherwise healthy patients with longstanding postherpetic neuralgia (PHN) were prospectively studied using clinical examination, infrared thermography and response to local anesthetic skin infiltration. All had at least 2 of 3 possible components to their PHN pain: continuous, neuralgic, or allodynic. In patients with allodynia, maximal reported pain and the location of maximal allodynia on sensory examination were largely overlapping and were often warm thermographically. Areas of dense sensory loss and skin scarring without allodynia were usually cool thermographically. Local anesthetic skin infiltration produced substantial pain relief in all 9 patients (essentially complete relief in 7) with allodynia: the 3 patients with predominantly continuous pain were not relieved. In 7 of 8 skin infiltration responders, the same dose of lidocaine i.m. in the deltoid muscle also produced significant, though less complete pain relief. These results suggest that PHN patients can be divided into at least 2 clinical groups: those with predominantly continuous pain localized to a region of significant sensory loss and those in whom allodynia is the most prominent sensory disturbance. The latter group has pain localized to areas with relatively preserved sensation. The differences in clinical features and response to lidocaine suggest that there are at least 2 different mechanisms contributing to the pain of PHN.     

基于DTI的三叉神经痛脑白质结构异常及其与临床特征的相关性

目的 采用基于纤维束的空间统计方法（TBSS）探讨原发性三叉神经痛（PTN）患者脑白质微结构异常。方法 对38例PTN患者（PTN组）和38名年龄、性别匹配的健康志愿者（对照组）行全脑DTI扫描,并用FSL软件进行分析,寻找FA值、平均扩散系数（MD）、径向扩散系数（RD）和轴向扩散系数（AD）存在组间统计学差异的脑区,并与视觉模拟评分（VAS）进行相关分析。结果 与对照组相比,PTN组胼胝体、放射冠、左侧上纵束、左侧下纵束及下额枕束FA值降低;且PTN组双侧丘脑后辐射、双侧内囊、双侧外囊、穹窿、右侧上纵束同时存在MD值和RD值升高,而AD升高脑区仅局限于双侧内囊前支、左侧内囊后支、双侧上放射冠和双侧上纵束。PTN患者左侧上纵束FA值与VAS呈负相关（r=-0.502,P=0.001）,左侧上纵束MD值与VAS评分呈正相关（r=0.437,P=0.006）。结论 丘脑、内囊MD值和RD值同向升高而不伴FA值降低可能是PTN的相对特征性DTI表现;左侧上纵束FA值和MD值对评估PTN患者疼痛水平有参考价值。     

Diagnosis and treatment of trigeminal neuralgia

Trigeminal neuralgia is a disease affecting older individuals. The clinical hallmark of trigeminal neuralgia is a sudden, excruciating paroxysm of pain in the area of the trigeminal nerve. Drug therapy is considered the first line of treatment for trigeminal neuralgia. Anticonvulsant carbamazepine has been used. If relevant pharmacotherapy has been tried without any effect, other procedures are selected. These procedures are microvascular decompression(a radical technique), glycerol trigeminal rhizotomy, percutaneous trigeminal nerve decompression and nerve block. Nerve block with neurolytic solutions and radiofrequency thermocoagulation is a simple, less invasive therapy. In order to avoid hypesthesia and dysesthesia, nerve block using a high concentration of local anesthetics is recommended. In recent years, stereotactic radiosurgery for trigeminal neuralgia has emerged as a new therapeutic modality.     

Pharmacotherapy of trigeminal neuralgia.

The efficacy of the anticonvulsant drug carbamazepine in the management of trigeminal neuralgia is evidenced in several controlled trials, and the numbers needed to treat to obtain one patient with at least 50% pain relief (NNT) is 1.7. Single small trials have shown that baclofen alone provides pain relief (NNT = 1.4) and that lamotrigine has an additional effect in patients with insufficient relief using carbamazepine or phenytoin (NNT = 2.1). Uncontrolled observations and clinical practice indicate that phenytoin, clonazepam, sodium valproate, gabapentin, and lidocaine will also relieve trigeminal neuralgia. In case of lacking effect of a single drug, combination of two or more drugs may be used, but with the exception of the lamotrigine-carbamazepine combination, this is not evidence-based medicine. Acute exacerbation has successfully been treated with intravenous loading with phenytoin or lidocaine, but again these procedures have not been tested in controlled trials. In conclusion, carbamazepine is the mainstay of pharmacotherapy of trigeminal neuralgia, and secondary drug choices are baclofen, lamotrigine, oxcarbazepine, phenytoin, gabapentin, and sodium valproate. Controlled trials testing the effect of some of these drugs, new drugs, and drug combinations are needed.