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.

Neuropathic Orofacial Pain

Neuropathic pain of the orofacial region can cause much distress in individuals presenting with this condition. It may be easily mistaken for dental pain, and hence many individuals may undergo unnecessary dental work. Knowledge of the types of neuropathic orofacial pain may assist in timely diagnosis and improvement of a patient's quality of life.

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.

Evaluating the impact of trigeminal neuralgia

Patients with idiopathic trigeminal neuralgia (TN) were categorised into 3 subtypes (n = 225). Group 1 (n = 155, 68.9%) had TN without concomitant pain, group 2 (n = 32, 14.2%) had TN with intermittent concomitant pain, and group 3 (n = 39, 16.9%) had TN with autonomic symptoms. We tested 2 hypotheses: (1) that different pain profiles would be associated with the different groups; (2) that the severe pain associated with TN would impact negatively on activities of daily living and thereby result in disability as defined by the World Health Organisation. A different pain profile was found across the groups. We obtained unequivocal evidence that TN causes disability with up to 45% of patients being absent from usual daily activities 15 days or more in the past 6 months. On the Hospital Anxiety and Depression Scale, 35.7% patients had mild-to-severe depression and over 50% were anxious. The Pain Catastrophizing Scale showed that 78% of patients had considerable negative thoughts with scores >20 and a mean score of 36.4. Prior to referral, only 54% had been prescribed carbamazepine while opioids had been prescribed in 14.6% of the patients. Prior to referral, over 80% had already been to 1 specialist centre which had not provided appropriate management. Patients with TN report varied characteristics but all result in some degree of psychosocial disability especially before adequate therapy is attained.

Epicrania Fugax

Epicrania fugax (EF) is a primary headache of recent description. EF essentially consists of brief paroxysms of pain describing a linear or zigzag trajectory across the surface of one hemicranium, commencing and terminating in the territories of different nerves. The pain of forward EF originates in a particular area of the occipital, parietal or temporal regions and moves anteriorly, whereas the pain of backward EF originates in the frontal area, the eye or the nose and moves posteriorly. Some patients have ocular or nasal autonomic accompaniments, and some have triggers. Between attacks, many patients have continuous or intermittent pain and/or tenderness at the stemming area. Pain frequency is extremely variable and some patients have spontaneous remissions. Preventive therapy is required when the paroxysms are frequent and non-remitting. Neuromodulators, indomethacin, amitryptiline, nerve anesthetic blockades, and trochlear steroid injections have been used in different cases, with partial or complete response.

Facial epicrania fugax: A prospective series of eight new cases

Introduction

Epicrania fugax (EF) is a primary headache whose main feature is the dynamic character of the pain. EF pain typically moves across different dermatomes in a linear or zigzag trajectory. Recently, a facial variant of EF has been described, with the pain starting in the lower face and radiating upwards.

Aim

We report eight patients with an EF-type of pain of facial location and either upward or downward radiation.

Methods

For each patient, we recorded relevant demographic and clinical data. Magnetic resonance imaging (MRI) with fast imaging employing steady state acquisition (FIESTA) was obtained in all cases for the assessment of neurovascular compression of the trigeminal nerve.

Results

There were seven women and one man, and the mean age was 76.1 years (standard deviation, 11.3). Six patients had a paroxysmal pain starting at the lower face and moving upwards, while two patients had downward radiation. The pain always followed a fixed linear trajectory across different dermatomes. All cases had triggers, and pain intensity was consistently severe. Half of the patients had accompanying autonomic features. Neurovascular compression with imprinting over the trigeminal root on the symptomatic side was identified in three patients. All cases responded to antiepileptic drugs, and three had spontaneous remissions.

Conclusions

This series reinforces the facial variant of EF and extends the phenotype with cases of downward radiation. It also contributes to enriching the differential diagnosis of facial pain. Neurovascular compression of the trigeminal nerve may be found in some cases, although a possible pathogenic link needs further research.

Trigeminal neuralgia (part II): Factors affecting early pharmacotherapeutic outcome

Aims

We conducted a cohort study to examine demographic and clinical features associated with the pharmacotherapeutic outcome in classical trigeminal neuralgia (CTN) patients.

Methods

Patients with a clinical profile indicating a diagnosis of CTN, as per the International Headache Society’s published classification, were enrolled prospectively. Demographic and pain-related characteristics were carefully collected. For the purposes of the study, patients with features such as autonomic signs and longer attack duration were included. All patients were then initiated on a standardised and accepted stepped pharmacotherapeutic protocol for the management of CTN. Initial pain scores and prospectively collected pain scores from pain diaries were used to assess the treatment outcome, with a ≥50% reduction considered significant.

Results

A total of 86 patients were seen, of whom five had an underlying disorder that could account for the pain. The study cohort therefore consisted of 81 patients, and based on attack duration these were divided into short (≤2 minutes, n = 61) and long (>2 minutes, n = 20) groups, for further analysis. The features of these patients and a discussion on the differential diagnosis have been presented in part 1 of this report. Employing an accepted stepped pharmacotherapeutic protocol for the management of CTN, significant improvement was more frequent in the short (74%) than in the long attack group (50%, p = 0.05). In the short attack group there were statistically significant associations between a poor treatment response and longer disease duration, the presence of autonomic signs and atypical pain descriptors for pain quality ( p < 0.05).

Conclusion

This report supports previous findings that prolonged disease duration and autonomic signs are negative prognostic indicators. The present study now adds long attack duration as a further negative prognostic sign.

Facial pain radiating upwards: could the pain of epicrania fugax start in the lower face?

BACKGROUND

Epicrania fugax (EF) is characterized by painful paroxysms starting in a particular area of the head, and rapidly radiating forwards or backwards through the territories of different nerves. In former clinical descriptions, the pain moved between the posterior scalp (C2) and the frontal or periorbital area (V1), either in forward or backward direction.

METHODS

We report 5 patients with a paroxysmal EF-type pain starting in the lower face (V2 or V3) and radiating upwards.

RESULTS

In each patient, the pain stemmed from the cheek (n = 1), the upper lip (n = 2) or the chin and mandibular area (n = 2), and then moved up to the forehead or the scalp with linear trajectory. Pain intensity was moderate (n = 1) or severe (n = 4), and pain quality was stabbing (n = 2) or electric (n = 3). The duration of attacks was very brief, lasting 1 to a few seconds. Three patients had ocular or nasal autonomic accompaniments, and 3 had triggers.

CONCLUSIONS

There seems to be a facial variant of EF. These observations could not only expand the clinical spectrum of EF but also enlarge the differential diagnosis of facial pain.

Multi-dimensionality of chronic pain of the oral cavity and face

Orofacial pain in its broadest definition can affect up to 7% of the population. Its diagnosis and initial management falls between dentists and doctors and in the secondary care sector among pain physicians, headache neurologists and oral physicians. Chronic facial pain is a long term condition and like all other chronic pain is associated with numerous co-morbidities and treatment outcomes are often related to the presenting co-morbidities such as depression, anxiety, catastrophising and presence of other chronic pain which must be addressed as part of management . The majority of orofacial pain is continuous so a history of episodic pain narrows down the differentials. There are specific oral conditions that rarely present extra orally such as atypical odontalgia and burning mouth syndrome whereas others will present in both areas. Musculoskeletal pain related to the muscles of mastication is very common and may also be associated with disc problems. Trigeminal neuralgia and the rarer glossopharyngeal neuralgia are specific diagnosis with defined care pathways. Other trigeminal neuropathic pain which can be associated with neuropathy is caused most frequently by trauma but secondary causes such as malignancy, infection and auto-immune causes need to be considered. Management is along the lines of other neuropathic pain using accepted pharmacotherapy with psychological support. If no other diagnostic criteria are fulfilled than a diagnosis of chronic or persistent idiopathic facial pain is made and often a combination of antidepressants and cognitive behaviour therapy is effective. Facial pain patients should be managed by a multidisciplinary team.

Diagnosis and management of trigeminal neuropathic pains

SUMMARY Trigeminal neuropathic pains have presented diagnostic and therapeutic challenges to providers. In addition, knowledge of pathophysiology, current classification systems, taxonomy and phenotyping of these conditions are incomplete. While trigeminal neuralgia is the most identifiable and studied, other conditions are being recognized and require distinct management approaches. Furthermore, other facial pain conditions such as atypical odontalgia and burning mouth syndrome are now considered to have neuropathic elements in their etiology. This article reviews current knowledge on the pathophysiology, diagnosis and management of neuropathic pain conditions involving the trigeminal nerve, to include: trigeminal neuralgia, trigeminal neuropathic pain (with traumatically induced neuralgia and atypical odontalgia) and burning mouth syndrome. Treatment modalities are reviewed based on current and best available evidence. Trigeminal neuralgia is managed with anticonvulsant drugs as the first line, with surgical options providing variable results. Trigeminal neuropathic pain is managed medically based on the guidelines for other neuropathic pain conditions. Burning mouth syndrome is also treated with a number of neuropathic medications, both topical and systemic. In all these conditions, patients need to be thoroughly educated about their condition, involved in its management, and be provided with supportive and adjunctive treatment resources.

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).

Trigeminal neuralgia during sleep

Pain paroxysms in trigeminal neuralgia (TN) are sudden and extremely intense. Nonetheless, many clinicians who treat TN report that patients are rarely if ever awakened at night by pain attacks. If true, this observation is important as it implies the presence of a powerful sleep protective mechanism. We queried TN patients and their habitual sleep partners about painful awakenings and discovered that such awakenings are in fact quite common. As during the day, pain paroxysms during sleep are typically induced by natural stimuli at TN trigger points. Brief attacks sometimes occur without frankly awakening the patient, but they appear nonetheless to be painful.

Management of neuropathic orofacial pain

Current management of painful trigeminal neuropathies relies on pharmacological (topical and systemic), surgical, and complementary modalities. There is, however, a lack of quality research relating to the effectiveness of these modalities. In this review we analyze the available data that relates to the therapy of trigeminal neuralgia, postherpetic neuralgia, and posttraumatic neuropathies and provide clinical guidelines. The review focuses on medical management, as well as surgical and other interventions for painful neuropathies.