Diagnostic accuracy of trigeminal reflex testing in trigeminal neuralgia

The blink reflex and its modulation - Part 2: Pathophysiology and clinical utility

The blink reflex (BR) is integrated at the brainstem; however, it is modulated by inputs from various structures such as the striatum, globus pallidus, substantia nigra, and nucleus raphe magnus but also from afferent input from the peripheral nervous system. Therefore, it provides information about the pathophysiology of numerous peripheral and central nervous system disorders. The BR is a valuable tool for studying the integrity of the trigemino-facial system, the relevant brainstem nuclei, and circuits. At the same time, some neurophysiological techniques applying the BR may indicate abnormalities involving structures rostral to the brainstem that modulate or control the BR circuits. This is a state-of-the-art review of the clinical application of BR modulation; physiology is reviewed in part 1. In this review, we aim to present the role of the BR and techniques related to its modulation in understanding pathophysiological mechanisms of motor control and pain disorders, in which these techniques are diagnostically helpful. Furthermore, some BR techniques may have a predictive value or serve as a basis for follow-up evaluation. BR testing may benefit in the diagnosis of hemifacial spasm, dystonia, functional movement disorders, migraine, orofacial pain, and psychiatric disorders. Although the abnormalities in the integrity of the BR pathway itself may provide information about trigeminal or facial nerve disorders, alterations in BR excitability are found in several disease conditions. BR excitability studies are suitable for understanding the common pathophysiological mechanisms behind various clinical entities, elucidating alterations in top-down inhibitory systems, and allowing for follow-up and quantitation of many neurological syndromes.

Headache and Other Pain Syndromes in Multiple Sclerosis: A Narrative Review

Multiple sclerosis is a chronic and progressive neurological disease, with an important socio-economic burden. Over time, an increased incidence of headaches like migraines and tension headaches has been observed among these patients. Headaches have not been considered as multiple sclerosis-related symptoms, even representing a red flag for multiple sclerosis diagnosis. It is uncertain whether the headache-multiple sclerosis association could be explained by the presence of common triggers or a common physiopathological mechanism (involvement of tertiary B-cell follicles). An important differential diagnosis is between multiple sclerosis attacks and migraines with aura, which can also be associated with neurological deficits. Another important aspect is the occurrence or exacerbation of the cephalalgic syndrome after the initiation of therapy for multiple sclerosis (DMTs), or the improvement of headache after the initiation of certain DMT drugs. In addition to headaches, individuals diagnosed with multiple sclerosis often report experiencing diverse pain syndromes, contributing to an additional decline in their overall quality of life. These syndromes are frequently neglected, the focus being on slowing down the progression of neurological deficits. This review aims to evaluate the characteristics of multiple-sclerosis-related headaches (frequency, possible correlation with attacks, and disease-modifying therapies) and the key distinctions in imaging characteristics between demyelinating lesions in multiple sclerosis and those observed in cases of primary headaches.

Effectiveness of gamma knife radiosurgery in the management of trigeminal neuralgia associated with multiple sclerosis: a systematic review and meta-analysis

BACKGROUND

Trigeminal neuralgia (TN) is a chronic condition characterized by intense facial pain akin to electric shocks, often associated with the trigeminal nerve. It can be either idiopathic or secondary, with multiple sclerosis (Ms) being a significant contributing factor. Non-responsive patients may opt for minimally invasive procedures, such as gamma knife radiosurgery (GKRS), which offers precise, non-invasive treatment and is frequently chosen as a primary approach. This meta-analysis evaluates the long-term efficacy of GKRS in TN management in Ms patients.

METHODS

We conducted a focused search across various databases. Inclusion criteria encompassed studies with ≥ 30 patients using GKRS for TN in Ms, reporting pertinent clinical outcomes. Primary outcomes assessed GKRS efficacy through Barrow Neurological Institute Pain scores. Secondary outcomes encompassed bothersome numbness, facial numbness, and recurrence. Data analysis employed OpenMeta, random effect models, and odds ratios with 95% confidence intervals. Heterogeneity was assessed using I2 statistics.

RESULTS

Fourteen studies with 752 cases of GKRS for TN were included. Regarding the outcomes, 83% of patients experienced a positive initial pain response, while the overall treatment success rate was 51%. Additionally, 19.6% of patients reported facial numbness, 4.1% experienced bothersome numbness, and 40% faced recurrence. The odds ratio for positive initial pain response was 0.83 (95% CI, 0.76-0.89), while for treatment success, it was 0.51 (95% CI, 0.379-0.639). Facial numbness had an odds ratio of 0.196 (95% CI, 0.130-0.262), bothersome numbness had an odds ratio of 0.041 (95% CI, 0.013-0.069), and recurrence had an odds ratio of 0.403 (95% CI, 0.254-0.551).

CONCLUSIONS

In conclusion, treating trigeminal neuralgia in multiple sclerosis patients remains challenging. GKRS shows promise, but customized treatment approaches tailored to individual patient characteristics are urgently needed to address the unique challenges of this condition.

The Therapeutic Effect of Botulinum Toxin Type A on Trigeminal Neuralgia: Are There Any Differences between Type 1 versus Type 2 Trigeminal Neuralgia?

BACKGROUND

Botulinum toxin type A is an effective treatment for trigeminal neuralgia. Moreover, its efficacy in type 2 trigeminal neuralgia and comparative studies between type 1 and type 2 trigeminal neuralgia (TN) still need to be improved.

METHODS

We treated 40 TN patients with onabotulinumtoxinA; 18 had type 1 TN, and 22 had type 2 TN. We compared the baseline pain score with the Visual Analogue Scale (VAS) and paroxysm frequency (number per week) at the baseline with those obtained at 1-month and 3-month follow-ups. Nonetheless, we compared the baseline Penn Facial Pain Scale with the scores obtained at the 1-month follow-up.

RESULTS

BoNT/A effectively reduced pain intensity and frequency at the 1-month and 3-month follow-ups. Moreover, the type 1 TN and type 2 TN groups had baseline pain scores of 7.8 ± 1.65 and 8.4 ± 1.1, respectively. Pain significantly improved (p < 0.001) in both groups to 3.1 ± 2.3 (type 1 TN) and 3.5 ± 2.3 (type 2 TN) at the 1-month follow-up and to 3.2 ± 2.5 (type 1 TN) and 3.6 ± 2.5 (type 2 TN) at the 3-month follow-up. There was no difference between the two groups (p 0.345). The baseline paroxysm frequencies (number per week) were 86.7 ± 69.3 and 88.9 ± 62.2 for the type 1 and type 2 TN groups, respectively; they were significantly reduced in both groups at the 1-month and 3-month follow-ups without significant differences between the two groups (p 0.902). The Pain Facial Pain Scale improved at the 1-month follow-up, and no significant differences were found between the two groups. There was a strong correlation between background pain and paroxysm pain intensity (r 0.8, p < 0.001).

CONCLUSIONS

Botulinum toxin type A effectively reduced the pain, paroxysm frequency, and PFPS scores of type 1 and type 2 trigeminal neuralgia patients without statistically significant differences. Facial asymmetry was the only adverse event.

The Molecular Basis and Pathophysiology of Trigeminal Neuralgia

Trigeminal neuralgia (TN) is a complex orofacial pain syndrome characterized by the paroxysmal onset of pain attacks in the trigeminal distribution. The underlying mechanism for this debilitating condition is still not clearly understood. Decades of basic and clinical evidence support the demyelination hypothesis, where demyelination along the trigeminal afferent pathway is a major driver for TN pathogenesis and pathophysiology. Such pathological demyelination can be triggered by physical compression of the trigeminal ganglion or another primary demyelinating disease, such as multiple sclerosis. Further examination of TN patients and animal models has revealed significant molecular changes, channelopathies, and electrophysiological abnormalities in the affected trigeminal nerve. Interestingly, recent electrophysiological recordings and advanced functional neuroimaging data have shed new light on the global structural changes and the altered connectivity in the central pain-related circuits in TN patients. The current article aims to review the latest findings on the pathophysiology of TN and cross-examining them with the current surgical and pharmacologic management for TN patients. Understanding the underlying biology of TN could help scientists and clinicians to identify novel targets and improve treatments for this complex, debilitating disease.

[Neuropathic pain syndromes in patients with multiple sclerosis]

Among the numerous pain syndromes (PS) of various localizations and types, observed in patients with multiple sclerosis (MS), the greatest attention of researchers is attracted by neuropathic PS. Neuropathic PS are often present already in the early stage of MS, significantly reduce the quality of life, hinder the social adaptation of patients, poorly respond to therapy. Central neuropathic PS, which pathogenesis is closely related with plaques in the central nervous system, are most common in patients with MS. Diagnostics of neuropathic PS in MS is based mainly on typical clinical symptoms; MRI and neurophysiological methods data are of secondary importance. This review focuses on modern concepts of three main neuropathic PS in MS: ongoing extremity pain, trigeminal neuralgia and Lhermitte's sign. Clinical symptoms of neuropathic PS, current ideas about their pathogenetic mechanisms, MRI and neurophysiological techniques data and the existing approaches to conservative therapy and surgical treatment based on randomized trials data are presented.

The changing face of trigeminal neuralgia-A narrative review

OBJECTIVE

This narrative review aims to update the reader on the new classification of trigeminal neuralgia (TN), clinical signs, pathophysiologic evidence, and their implications on management. This review is based on the authors' collective experience and knowledge of the literature in addition to a literature search.

BACKGROUND

In recent years, the phenotype of TN has been intensively studied leading to discrete groups of patients. These include patients with TN with additional continuous pain, and patients with and without neurovascular compression of the trigeminal dorsal root entry zone. A number of associated clinical signs such as tearing and sensory changes need further research.

METHODS

The literature on TN was searched in PubMed with the aims of providing evidence for the recently published third edition of the International Classification of Headache Disorders (ICHD) and update the clinical phenotype and management of the TN subcategories.

RESULTS

The ICHD's new classification for TN is based on reliable clinical data, imaging, and neurophysiologic studies. The TN classification reflects current knowledge and has improved the possibility for clinicians to choose adequate management options. However, there is a lack of effective, safe drugs for the management of TN and sparse, robust data on neurosurgical options.

CONCLUSION

Research into all aspects of TN-diagnosis, pharmacotherapy, surgery, long-term management prognosis, and natural history-is needed. Research should adhere to the ICHD's schema for TN. Improved drugs are needed along with rigorous research into surgical options and their efficacy for different subtypes of TN.

Neurovascular contact plays no role in trigeminal neuralgia secondary to multiple sclerosis

INTRODUCTION

A demyelinating plaque and neurovascular contact with morphological changes have both been suggested to contribute to the etiology of trigeminal neuralgia secondary to multiple sclerosis (TN-MS). The aim of this study was to confirm or refute whether neurovascular contact with morphological changes is involved in the etiology of TN-MS.

METHODS

We prospectively enrolled consecutive TN-MS patients from the Danish Headache Center. Clinical characteristics were collected systematically. MRI scans were done using a 3.0 Tesla imager and were evaluated by the same experienced blinded neuroradiologist.

RESULTS

Sixty-three patients were included. Fifty-four patients were included in the MRI analysis. There was a low prevalence of neurovascular contact with morphological changes on both the symptomatic side (6 (14%)) and the asymptomatic side (4 (9%)), p = 0.157. Demyelinating brainstem plaques along the trigeminal afferents were more prevalent on the symptomatic side compared to the asymptomatic side (31 (58%) vs. 12 (22%), p < 0.001). A demyelinating plaque was highly associated with the symptomatic side (odds ratio = 10.6, p = 0.002).

CONCLUSION

The primary cause of TN-MS is demyelination along the intrapontine trigeminal afferents. As opposed to classical trigeminal neuralgia, neurovascular contact does not play a role in the etiology of TN-MS. Microvascular decompression should generally not be offered to patients with TN-MS.The study was registered at ClinicalTrials.gov (number NCT04371575).

Familial trigeminal neuralgia - a systematic clinical study with a genomic screen of the neuronal electrogenisome

Objective

This cross-sectional study examined, for the first time, a large cohort of patients with trigeminal neuralgia, to ascertain the occurrence of familial cases, providing a systematic description of clinical features of familial disease. Since there is evidence linking hyperexcitability of trigeminal ganglion neurons to trigeminal neuralgia, we also carried out an exploratory genetic analysis of the neuronal electrogenisome in these patients.

Methods

We recorded familial occurrence by systematically interviewing all patients with a definite diagnosis of classical or idiopathic trigeminal neuralgia. We found 12 occurrences of trigeminal neuralgia with positive family history out of 88 enrolled patients. Whole-exome sequencing was carried out in 11 patients. We concentrated on the genetic variants within a 173-gene panel, comprising channel genes encoding sodium, potassium, calcium, chloride, transient receptor potential channels, and gap junction channels. Gene expression profiles were based on published RNA sequencing datasets of rodent/human trigeminal ganglia tissues, with a focus on genes related to neuronal excitability.

Results

In patients with familial trigeminal neuralgia, pain was more often located in the right, second division. All patients reported triggers. Four patients experienced concomitant continuous pain. Whole-exome sequencing analysis within the trigeminal ganglion electrogenisome identified 41 rare variants in ion channels, consisting of variants in sodium channels (6), potassium channels (10), chloride channels (5), calcium channels (7), transient receptor potential channels (12), and gap junction channels (1). In one patient, a previously profiled gain-of-function mutation in SCN10A (Nav1.8 p.Ala1304Thr), previously reported in painful neuropathy, was found; this variant was not present in unaffected siblings.

Conclusions

Our results suggest that familial occurrence of trigeminal neuralgia is more common than previously considered. Although our results demonstrate variants in genes encoding voltage-gated ion channels and transient receptor potential channels within these patients, further study will be needed to determine their roles in the pathogenesis of trigeminal neuralgia.

Trigeminal neuralgia secondary to multiple sclerosis: from the clinical picture to the treatment options

BACKGROUND

Trigeminal neuralgia is one of the most characteristic and difficult to treat neuropathic pain conditions in patients with multiple sclerosis. The present narrative review addresses the current evidence on diagnostic tests and treatment of trigeminal neuralgia secondary to multiple sclerosis.

METHODS

We searched for relevant papers within PubMed, EMBASE and the Cochrane Database of Systematic Reviews, taking into account publications up to December 2018.

RESULTS

Trigeminal neuralgia secondary to multiple sclerosis manifests with facial paroxysmal pain triggered by typical manoeuvres; neurophysiological investigations and MRI support the diagnosis, providing the definite evidence of trigeminal pathway damage. A dedicated MRI is required to identify pontine demyelinating plaques. In many patients with multiple sclerosis, neuroimaging and surgical evidence suggests that neurovascular compression might act in concert with the pontine plaque through a double-crush mechanism. Although no placebo-controlled trials have been conducted in these patients, according to expert opinion the first-line therapy for trigeminal neuralgia secondary to multiple sclerosis relies on sodium-channel blockers, i.e. carbamazepine and oxcarbazepine. The sedative and motor side effects of these drugs frequently warrant an early consideration for neurosurgery. Surgical procedures include Gasserian ganglion percutaneous techniques, gamma knife radiosurgery and microvascular decompression in the posterior fossa.

CONCLUSIONS

The relatively poor tolerability of the centrally-acting drugs carbamazepine and oxcarbazepine highlights the need to develop new selective and better-tolerated sodium-channel blockers. Prospective studies based on more advanced neuroimaging techniques should focus on how trigeminal anatomical abnormalities may be able to predict the efficacy of microvascular decompression.

Guidelines for radiographic imaging of cranial neuropathies

Disruption of the complex pathways of the 12 cranial nerves can occur at any site along their course, and many, varied pathologic processes may initially manifest as dysfunction and neuropathy. Radiographic imaging (computed topography or magnetic resonance imaging) is frequently used to evaluate cranial neuropathies; however, indications for imaging and imaging method of choice vary considerably between the cranial nerves. The purpose of this review is to provide an analysis of the diagnostic yield and the most clinically appropriate means to evaluate cranial neuropathies using radiographic imaging. Using the PubMed MEDLINE NCBI database, a total of 49,079 articles' results were retrieved on September 20, 2014. Scholarly articles that discuss the etiology, incidence, and use of imaging in the context of evaluation and diagnostic yield of the 12 cranial nerves were evaluated for the purposes of this review. We combined primary research, guidelines, and best practice recommendations to create a practical framework for the radiographic evaluation of cranial neuropathies.

Trigeminal Neuralgia

PURPOSE OF REVIEW

Although trigeminal neuralgia is well known to neurologists, recent developments in classification and clinical diagnosis, new MRI methods, and a debate about surgical options necessitate an update on the topic.

RECENT FINDINGS

Currently, a worldwide controversy exists regarding the classification, diagnostic process, and surgical treatment of trigeminal neuralgia. This controversy has been caused on one side by the recognition that some 50% of patients with trigeminal neuralgia, apart from characteristic paroxysmal attacks, also have continuous pain in the same territory, which results in greater diagnostic difficulties and is associated with a lower response to medical and surgical treatments. In contrast, recent developments in MRI methods allow differentiation between a mere neurovascular contact and an effective compression of the trigeminal root by an anomalous vessel, which implies more difficulties in the choice of surgical treatment, with the indication for microvascular decompression becoming more restricted.

SUMMARY

This article proposes that the diagnosis of trigeminal neuralgia, with or without concomitant continuous pain, must rely on clinical grounds only. Diagnostic tests are necessary to distinguish three etiologic categories: idiopathic trigeminal neuralgia (nothing is found), classic trigeminal neuralgia (an anomalous vessel produces morphologic changes of the trigeminal root near its entry into the pons), and secondary trigeminal neuralgia (due to major neurologic disease, such as multiple sclerosis or tumors at the cerebellopontine angle). Carbamazepine and oxcarbazepine (ie, voltage-gated, frequency-dependent sodium channel blockers) are still the first-choice medical treatment, although many patients experience significant side effects, and those with concomitant continuous pain respond less well to treatment. The development of sodium channel blockers that are selective for the sodium channel 1.7 (Nav1.7) receptor will hopefully help. Although all the surgical interventions (percutaneous ganglion lesions, gamma knife radiosurgery, and microvascular decompression) are very efficacious, precise MRI criteria for differentiating a real neurovascular compression from an irrelevant contact will be of benefit in better selecting patients for microvascular decompression.

Trigeminal neuralgia (TN): A descriptive literature analysis on the diagnosis and management modalities

OBJECTIVE

The primary objective of this review is to explore the different aspects of the diagnosis and management of Trigeminal neuralgia (TN). We look at the role of radiological imaging in the work-up of this condition, and based on the findings in the literature, we report data on the medical and surgical management of TN.

MATERIALS AND METHODS

A literature review was conducted using PubMed and Cochrane search engines in order to explore the data available on the diagnosis and management of TN. Clinical features and various treatment modalities were analyzed by the authors. The identified studies were evaluated and data was reported on the different aspects of the condition in order to provide an evidence-based update on the topic.

DISCUSSION

The diagnosis of TN is based on the patient's clinical history and radiological imaging. The commonest cause of TN is a micro-vascular compression by a looping blood vessel. Radiological evaluation is critical in the work-up of the disorder and in order to eliminate other possible causes. Management of the disorder can be medical or surgical, with micro-vascular decompression having the highest remission rate.

CONCLUSION

Patients with TN present paroxysmal pain attacks in the territories innervated by the trigeminal nerve. Diagnostic investigations must allow precise anatomical evaluation of the CPA, and MR imaging is the gold-standard radiological investigation for this purpose. Management of TN can be medical or surgical, with micro-vascular decompression having the highest success rate.

Trigeminal neuralgia - diagnosis and treatment

Introduction Trigeminal neuralgia (TN) is characterized by touch-evoked unilateral brief shock-like paroxysmal pain in one or more divisions of the trigeminal nerve. In addition to the paroxysmal pain, some patients also have continuous pain. TN is divided into classical TN (CTN) and secondary TN (STN). Etiology and pathophysiology Demyelination of primary sensory trigeminal afferents in the root entry zone is the predominant pathophysiological mechanism. Most likely, demyelination paves the way for generation of ectopic impulses and ephaptic crosstalk. In a significant proportion of the patients, the demyelination is caused by a neurovascular conflict with morphological changes such as compression of the trigeminal root. However, there are also other unknown etiological factors, as only half of the CTN patients have morphological changes. STN is caused by multiple sclerosis or a space-occupying lesion affecting the trigeminal nerve. Differential diagnosis and treatment Important differential diagnoses include trigeminal autonomic cephalalgias, posttraumatic or postherpetic pain and other facial pains. First line treatment is prophylactic medication with sodium channel blockers, and second line treatment is neurosurgical intervention. Future perspectives Future studies should focus on genetics, unexplored etiological factors, sensory function, the neurosurgical outcome and complications, combination and neuromodulation treatment as well as development of new drugs with better tolerability.

Microstructural abnormalities of the trigeminal nerve by diffusion-tensor imaging in trigeminal neuralgia without neurovascular compression

Microstructural changes of the trigeminal nerve in trigeminal neuralgia due to neurovascular compression have been reported by using diffusion tensor imaging. Other aetiologies such as primary demyelinating lesions, brain stem infarction and nerve root infiltration by tumour affecting the trigeminal pathway may also present as trigeminal neuralgia. The aim of this study was to evaluate the microstructural tissue abnormalities in the trigeminal nerve in symptomatic trigeminal neuralgia not related to neurovascular compression using diffusion tensor imaging. Mean values of the quantitative diffusion parameters of trigeminal nerve, fractional anisotropy and apparent diffusion coefficient, were measured in a group of four symptomatic trigeminal neuralgia patients without neurovascular compression who showed focal non-enhancing T2-hyperintense lesions in the pontine trigeminal pathway. These diffusion parameters were compared between the affected and unaffected sides in the same patient and with four age-matched healthy controls. Cranial magnetic resonance imaging revealed hyperintense lesions in the dorsolateral part of the pons along the central trigeminal pathway on T2-fluid-attenuated inversion recovery sequences. The mean fractional anisotropy value on the affected side was significantly decreased (P = 0.001) compared to the unaffected side and healthy controls. Similarly, the mean apparent diffusion coefficient value was significantly higher (P = 0.001) on the affected side compared to the unaffected side and healthy controls. The cause of trigeminal neuralgia in our patients was abnormal pontine lesions affecting the central trigeminal pathway. The diffusion tensor imaging results suggest that microstructural tissue abnormalities of the trigeminal nerve also exist even in non-neurovascular compression-related trigeminal neuralgia.

Novel High-Frequency Peripheral Nerve Stimulator Treatment of Refractory Postherpetic Neuralgia: A Brief Technical Note

OBJECTIVES

The study aims to describe an ultrasound (US)-guided peripheral nerve stimulation implant technique and describe the effect of high-frequency peripheral nerve stimulation on refractory postherpetic neuralgia.

MATERIALS AND METHODS

Following a cadaver pilot trial using US and confirmatory fluoroscopic guidance, a 52-year-old man with refractory left supraorbital neuralgia underwent combined US and fluoroscopic-guided supraorbital peripheral nerve stimulator trial. The patient was subsequently implanted with a percutaneous lead over the left supraorbital and supratrochlear nerve utilizing a high-frequency stimulation paradigm.

RESULTS

At 9 months follow-up, the pain intensity had declined from a weekly average of 8/10 to 1/10 on the pain visual analog scale (VAS). After implant, both nerve conduction and blink reflex studies were performed, which demonstrated herpetic nerve damage and frequency-specific peripheral nerve stimulation effects. The patient preferred analgesia in the supraorbital nerve distribution accomplished with high-frequency paresthesia-free stimulation (HFS) at an amplitude of 6.2 mA, a frequency of 100-1200 Hz, and a pulse width of 130 μsec, to paresthesia-mediated pain relief associated with low-frequency stimulation.

CONCLUSION

We report the implant of a supraorbital peripheral nerve stimulating electrode that utilizes a high-frequency program resulting in sustained suppression of intractable postherpetic neuralgia.

Advances in diagnosis and treatment of trigeminal neuralgia

Various drugs and surgical procedures have been utilized for the treatment of trigeminal neuralgia (TN). Despite numerous available approaches, the results are not completely satisfying. The need for more contemporaneous drugs to control the pain attacks is a common experience. Moreover, a number of patients become drug resistant, needing a surgical procedure to treat the neuralgia. Nonetheless, pain recurrence after one or more surgical operations is also frequently seen. These facts reflect the lack of the precise understanding of the TN pathogenesis. Classically, it has been related to a neurovascular compression at the trigeminal nerve root entry-zone in the prepontine cistern. However, it has been evidenced that in the pain onset and recurrence, various neurophysiological mechanisms other than the neurovascular conflict are involved. Recently, the introduction of new magnetic resonance techniques, such as voxel-based morphometry, diffusion tensor imaging, three-dimensional time-of-flight magnetic resonance angiography, and fluid attenuated inversion recovery sequences, has provided new insight about the TN pathogenesis. Some of these new sequences have also been used to better preoperatively evidence the neurovascular conflict in the surgical planning of microvascular decompression. Moreover, the endoscopy (during microvascular decompression) and the intraoperative computed tomography with integrated neuronavigation (during percutaneous procedures) have been recently introduced in the challenging cases. In the last few years, efforts have been made in order to better define the optimal target when performing the gamma knife radiosurgery. Moreover, some authors have also evidenced that neurostimulation might represent an opportunity in TN refractory to other surgical treatments. The aim of this work was to review the recent literature about the pathogenesis, diagnosis, and medical and surgical treatments, and discuss the significant advances in all these fields.

Diagnosis and management of neuropathic pain

A recent revision in the definition of neuropathic pain has highlighted this condition as a distinct disease entity. More accurate search for a lesion in the somatosensory nervous system as the pain-generating mechanism will help target the treatment by pharmacological agents. A multidisciplinary approach is recommended, with pharmacotherapy supplemented by psychological therapy and physical rehabilitation, and appropriate interventional treatment for selected refractory cases.

Primary headaches and trigeminal neuralgia: neuropathic pain yes or not? Evidences from neurophysiological procedures

Despite the fact that neurophysiological evaluation is not useful for primary headache diagnosis, the nociceptive system exploration through reflexes and evoked potentials procedures may give an aid in understanding the pathophysiological mechanism subtending pain. Neuropathic pain is caused by a lesion or disease of the somatosensory nervous system, which is supported by clinical evaluation and instrumental assessment by trigeminal and nociceptive reflexes and laser evoked potentials. The same methods, applied to migraine and cluster headache, together with evidences coming from structural and functional neuroimaging, excluded the neuropathic origin of pain, which is attaining to symptomatic and idiopathic trigeminal neuralgia, but confirmed a complex dysfunction of pain processing. Tension-type headache fits with a model of non-nociceptive and non-neuropathic pain, subtended by a complex interaction of peripheral muscular and central neuronal factors. The presence of altered modulation of pain concurs with migraine and tension-type headache, and should be taken into account for the choice of the best therapeutic approach.

Prevalence of trigeminal neuralgia and persistent idiopathic facial pain: a population-based study

OBJECTIVE

To estimate the lifetime prevalence of trigeminal neuralgia (TN) and persistent idiopathic facial pain (PIFP) in a population-based sample in Germany.

METHODS

A total of 3336 responders of 6000 contacted inhabitants of the city of Essen in Germany were screened using a self-assessment questionnaire. 327 individuals, who reported recurrent facial pain and randomly selected 150 (5% of 3009) screening negative subjects, received a phone interview by one of six neurologists and if necessary a face-to-face examination. Those with suspected TN or PIFP following the phone interview underwent neurological examination by two neurologists who were unaware of the presumed diagnosis. A random group of 25 (10% of 247) phone interview negative subjects was examined face-to-face. All suspected cases of PIFP received otorhinolaryngological examination and diagnostic cranial magnetic resonance imaging (MRI). In TN patients the number of vessel-nerve contacts was determined by thin-slice cranial MRI.

RESULTS

Lifetime prevalence of TN was estimated to be 0.3% [10 of 3336; 95% CI 0.1-0.5%], of PIFP 0.03% [1 of 3336; 95% CI < 0.08%]. Thin-slice cranial MRI detected five vessel-nerve contacts and no symptomatic lesions in the 10 TN patients.

CONCLUSIONS

This large population-based study revealed that TN and PIFP are rare facial pain disorders.

NeuPSIG guidelines on neuropathic pain assessment

This is a revision of guidelines, originally published in 2004, for the assessment of patients with neuropathic pain. Neuropathic pain is defined as pain arising as a direct consequence of a lesion or disease affecting the somatosensory system either at peripheral or central level. Screening questionnaires are suitable for identifying potential patients with neuropathic pain, but further validation of them is needed for epidemiological purposes. Clinical examination, including accurate sensory examination, is the basis of neuropathic pain diagnosis. For more accurate sensory profiling, quantitative sensory testing is recommended for selected cases in clinic, including the diagnosis of small fiber neuropathies and for research purposes. Measurement of trigeminal reflexes mediated by A-beta fibers can be used to differentiate symptomatic trigeminal neuralgia from classical trigeminal neuralgia. Measurement of laser-evoked potentials is useful for assessing function of the A-delta fiber pathways in patients with neuropathic pain. Functional brain imaging is not currently useful for individual patients in clinical practice, but is an interesting research tool. Skin biopsy to measure the intraepidermal nerve fiber density should be performed in patients with clinical signs of small fiber dysfunction. The intensity of pain and treatment effect (both in clinic and trials) should be assessed with numerical rating scale or visual analog scale. For future neuropathic pain trials, pain relief scales, patient and clinician global impression of change, the proportion of responders (50% and 30% pain relief), validated neuropathic pain quality measures and assessment of sleep, mood, functional capacity and quality of life are recommended.

Percutaneous radiofrequency thermocoagulation for the treatment of different types of trigeminal neuralgia: evaluation of quality of life and outcomes

Radiofrequency thermocoagulation (RFT) of the gasserian ganglion is a routine and effective technique for the treatment of classical trigeminal neuralgia (CTN). In this study we compared its efficacy in patients with CTN and atypically symptomatic or mixed trigeminal neuralgia (MTN). Fifty-seven patients were treated with RFT for trigeminal neuralgia from June 2006 to February 2009. Thirty patients had CTN, and 27 had MTN. Outcomes were measured by using the visual analog pain scale (VAS) and patients' reports of quality of life (QOL), medication usage, and complications over a follow-up period of up to 3 years. Our results showed that the patients with MTN were younger, tended to have bilaterial involvement of the first division, and were unresponsive to treatment. All surgeries were completed smoothly. About 86.7% CTN patients and 48.1% MTN patients responded immediately to RFT. The VAS scores were significantly higher in the CTN group than in MTN group (P<0.05). Kaplan-Meier curves showed that 1-year, 2-year, and 3-year pain relief rates were 76.7%, 73.3%, and 73.3% in the CTN group and 46.6%, 41.4%, and 41.4% in the MTN group, respectively. The rates of pain relief for both groups leveled off at 2 years. Complications included numbness, dysesthesia, and anesthesia dolorosa. RFT did not cause any deaths and complications were low. The treatment was very effective for CTN and, to some degrees, effective for MTN. If numbness, dysesthesia, and anesthesia dolorosa are limited to the trigger area, QOL will be greatly improved.

Evaluation of the pathophysiology of classical trigeminal neuralgia by blink reflex study and current perception threshold testing

We recruited 49 patients with classical trigeminal neuralgia (TN) according to the latest guidelines of the International Classification of Headache Disorders, and divided them into an acute (≤30 days onset; 13 patients) and a chronic (>30 days onset; 36 patients) group. We used blink reflex study and current perception threshold (CPT) testing to evaluate the painful facial areas and contralateral non-painful areas of patients with classical TN. CPT 5 Hz examinations, which correlate with unmyelinated fiber function, showed significantly decreased CPTs in the acute stage (11.62 ± 6.99 vs. 18.69 ± 9.66, P = 0.025), but significantly increased CPTs in the chronic stage (26.67 ± 18.65 vs. 19.69 ± 13.70, P = 0.010) on the painful side when compared with the contralateral non-painful side. However, CPTs at 250 Hz (Aδ) and 2000 Hz (Aβ) examinations did not show significant differences between the painful and non-painful sides. In contrast, only three (3/49) patients showed an abnormal trigeminal nerve stimulation on the ipsilateral painful side by blink reflex study. The findings suggest that classical TN is not a simple large-myelinated nerve fiber dysfunction but a more complex process with a main dysfunction of unmyelinated nerve fibers.

Cranial neuralgias

After a description of the anatomical-functional organization of the human trigeminal system, this chapter discusses the diagnostic and therapeutic options for trigeminal neuralgia (TN). In about 15% of patients who present with the clinical picture of typical TN, this is secondary to a major neurological disease, i.e., benign tumors of the cerebellopontine angle or multiple sclerosis. Some clinical criteria that were used to distinguish between classic and symptomatic TN, such as age at onset, involvement of the ophthalmic division, and responsiveness to medical treatment, are no longer considered reliable. It is recommended that all patients undergo magnetic resonance imaging (MRI) or trigeminal reflex recording. Carbamazepine (CBZ) and oxcarbazepine (OXC) are the first-choice medical treatments. Although other drugs may be effective, these are indicated when the patient cannot reach the therapeutic dosage of CBZ/OXC because of adverse events. Patients unresponsive to CBZ/OXC should be made aware of the available surgical interventions. Surgical procedures (including percutaneous lesions to the ganglion/root, microvascular decompression (MVD) in the posterior fossa, and gamma knife radiosurgery) are extremely efficacious with relatively few complications: each procedure has some advantage and disadvantage with respect to the other. Only MVD is a non-destructive procedure. This chapter also describes management of glossopharyngeal neuralgia, which is often misdiagnosed, and some other chronic pain conditions mediated by the trigeminal system, such as ophthalmic postherpetic neuralgia (PHN).

What do general neurologists need to know about neuropathic pain?

Neuropathic pain (NP) is defined as pain caused by lesion or dysfunction of the somatosensory system, as a result of abnormal activation of the nociceptive pathway (small fibers and spinothalamic tracts). The most common causes of this syndrome are the following: diabetes, post-herpetic neuralgia, trigeminal neuralgia, stroke, multiple sclerosis, spinal cord injury, HIV infection, cancer. In the last few years, the NP has been receiving special attention for two main reasons: (1) therapeutical refractoriness of a variety of pain syndromes with predominant neuropathic characteristics and (2) the development of diagnostic tools for neuropathic pain complaints. The present review article provides relevant information on the understanding and recognition of NP, as well as evidence-based therapeutic approaches.

Trigeminal neuralgia and pain related to multiple sclerosis

Although many patients with multiple sclerosis (MS) complain of trigeminal neuralgia (TN), its cause and mechanisms are still debatable. In a multicentre controlled study, we collected 130 patients with MS: 50 patients with TN, 30 patients with trigeminal sensory disturbances other than TN (ongoing pain, dysaesthesia, or hypoesthesia), and 50 control patients. All patients underwent pain assessment, trigeminal reflex testing, and dedicated MRI scans. The MRI scans were imported and normalised into a voxel-based, 3D brainstem model that allows spatial statistical analysis. The onset ages of MS and trigeminal symptoms were significantly older in the TN group. The frequency histogram of onset age for the TN group showed that many patients fell in the age range of classic TN. Most patients in TN and non-TN groups had abnormal trigeminal reflexes. In the TN group, 3D brainstem analysis showed an area of strong probability of lesion (P<0.0001) centred on the intrapontine trigeminal primary afferents. In the non-TN group, brainstem lesions were more scattered, with the highest probability for lesions (P<0.001) in a region involving the subnucleus oralis of the spinal trigeminal complex. We conclude that the most likely cause of MS-related TN is a pontine plaque damaging the primary afferents. Nevertheless, in some patients a neurovascular contact may act as a concurring mechanism. The other sensory disturbances, including ongoing pain and dysaesthesia, may arise from damage to the second-order neurons in the spinal trigeminal complex.

AAN-EFNS guidelines on trigeminal neuralgia management

Several issues regarding diagnosis, pharmacological treatment, and surgical treatment of trigeminal neuralgia (TN) are still unsettled. The American Academy of Neurology and the European Federation of Neurological Societies launched a joint Task Force to prepare general guidelines for the management of this condition. After systematic review of the literature the Task Force came to a series of evidence-based recommendations. In patients with TN MRI may be considered to identify patients with structural causes. The presence of trigeminal sensory deficits, bilateral involvement, and abnormal trigeminal reflexes should be considered useful to disclose symptomatic TN, whereas younger age of onset, involvement of the first division, unresponsiveness to treatment and abnormal trigeminal evoked potentials are not useful in distinguishing symptomatic from classic TN. Carbamazepine (stronger evidence) or oxcarbazepine (better tolerability) should be offered as first-line treatment for pain control. For patients with TN refractory to medical therapy early surgical therapy may be considered. Gasserian ganglion percutaneous techniques, gamma knife and microvascular decompression may be considered. Microvascular decompression may be considered over other surgical techniques to provide the longest duration of pain freedom. The role of surgery versus pharmacotherapy in the management of TN in patients with multiple sclerosis remains uncertain.