Familial trigeminal neuralgia: case reports and review of the literature

Prevalence of Trigeminal Neuralgia and Persistent Idiopathic Facial Pain in Afyonkarahisar, Türkiye

BACKGROUND

Population-based studies examining the prevalence of trigeminal neuralgia (TN) and persistent idiopathic facial pain (PIFP) are rare, and data on TN prevalence in Türkiye are very limited, with the prevalence of PIFP being unknown. This study aimed to determine the prevalence of TN and PIFP in Türkiye.

MATERIALS AND METHODS

This population-based epidemiological study has a cross-sectional and descriptive design, and it was carried out in Afyonkarahisar, Türkiye. Participants aged 18 years and older were screened by using a self-assessment form to determine potential patients with TN or PIFP.

RESULTS

A total of 19,237 individuals were included in this study, of which 17,223 responded to the survey questions. TN was diagnosed in 17 individuals, and the prevalence of TN was calculated as 98.5 per 100,000. PIFP was diagnosed in 35 patients, and the prevalence of PIFP was calculated as 202 per 100,000. The mean age of the patients with TN was 54.29 ± 12.98 years, the mean age of patients with PIFP was 49.80 ± 16.10 years, and the female-to-male ratio was 1.13/1 for TN and 2.18/1 for PIFP.

CONCLUSION

The prevalence of PIFP in Türkiye has been reported for the first time by this study. Additionally, a much higher prevalence of TN was found when compared to previous study.

A Preliminary Study of the Efficacy of Transcranial Direct Current Stimulation in Trigeminal Neuralgia

The purpose of this study is to assess the efficacy of transcranial direct current stimulation (tDCS) in patients with treatment-refractory trigeminal neuralgia (TN) and examine the utility of neuroimaging methods in identifying markers of such efficacy. Six patients with classical TN refractory to maximal medical treatment, underwent tDCS (three cases inhibitory/cathodic and three cases excitatory/anodic stimulation). All patients underwent pre- and posttreatment functional magnetic resonance imaging (fMRI) during block-design tasks (i.e., Pain, Pain + tDCS, tDCS) as well as single-shell diffusion MRI (dMRI) acquisition. The precise locations of tDCS electrodes were identified by neuronavigation. Five therapeutic tDCS sessions were carried out for each patient with either anodic or cathodic applications. The Numeric Rating Scale of pain (NRS) and the Headache Disability Index (HDI) were used to score the subjective efficacy of treatment. Altered activity of regional sites was identified by fMRI and associated changes in the spinothalamocortical sensory tract (STCT) were measured by the dMRI indices of fractional anisotropy (FA) and mean diffusivity (MD). Fiber counts of the bilateral trigeminal root entry zone (REZ) were performed as an added measure of fiber loss or recovery. All patients experienced a significant reduction in pain scores with a substantial decline in HDI (P value < 0.01). Following a course of anodic tDCS, the ipsilateral caudate, globus pallidus, somatosensory cortex, and the contralateral globus pallidus showed a significantly attenuated activation whereas cathodic tDCS treatment resulted in attenuation of the thalamus and globus pallidus bilaterally, and the somatosensory cortex and anterior cingulate gyrus contralaterally. dMRI analysis identified a substantial increase (>50%) in the number of contralateral sensory fibers in the STCT with either anodic or cathodic tDCS treatment in four of the six patients. A significant reduction in FA (>40%) was observed in the ipsilateral REZ in the posttreatment phase in five of the six patients. Preliminary evidence suggests that navigated tDCS presents a promising method for alleviating the pain of TN. Different patterns of activation manifested by anodic and cathodic stimulation require further elaboration to understand their implication. Activation and attenuation of responses at various sites may provide further avenues for condition treatment.

Familial occurrence of classical and idiopathic trigeminal neuralgia

Trigeminal neuralgia (TN) is a severe facial pain disease with unknown pathogenesis. It has been thought that the familial form of TN is rare with a prevalence of about 1-2% among affected individuals, but emerging evidence suggests a role of genetic factors. This study examined the occurrence of familial TN among patients with classical or idiopathic TN. Patients with TN recruited from a hospital registry received an informed consent form with a questionnaire, and individuals reporting other family members with TN underwent a structured phone-interview. For affected family members, type of TN, available clinical, imaging, management results and available hospital patient records were studied. Pedigrees for all affected families were established. This study included 268 patients with either classical or idiopathic TN. The familial form of TN was present in 41/268 (15.3%) patients, that is, 37/244 (15.2%) patients with classical TN and in 4/24 (16.7%) with idiopathic TN. Total 38 families were identified, with two affected members in 32/38 families (84.2%), three affected family members in 5/38 (13.2%) and four family members in 1/38 (2.6%) families. Comparing the 41 familial TN cases with the 227 sporadic TN patients showed significantly earlier onset of TN and a significantly higher occurrence of right-sided pain in familial cases, while there was no difference in gender distribution, occurrence of arterial hypertension or trigeminal branch involved. Among patients with classical or idiopathic TN, the occurrence of the familial form of the disease is more frequent than traditionally assumed.

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.

Cranial Neuralgias

PURPOSE OF REVIEW

This article discusses the differential diagnosis, evaluation, and management of trigeminal neuralgia and reviews other neuralgias of the head and neck, including those that contribute to neuralgic ear pain.

RECENT FINDINGS

Most cases of trigeminal neuralgia are related to vascular compression, a demyelinating plaque, or a compressive mass affecting the trigeminal nerve. However, recent studies have shown that up to 11% of patients have a family history of trigeminal neuralgia, suggesting that some patients may have a genetic predisposition to demyelination or nerve hyperexcitability. In these patients, trigeminal neuralgia may occur at a younger age, on both sides of the face, or in combination with other neuralgias.

SUMMARY

When a patient presents with neuralgic pain, the diagnosis is made by careful history and neurologic examination, with attention to the dermatome involved, the triggers, and the presence of any associated sensory deficit. All patients with new neuralgia or neuropathic facial pain warrant a careful evaluation for a secondary cause. The presence of sensory deficit on bedside examination is particularly concerning for an underlying secondary etiology.

Trigeminal neuralgia and genetics: A systematic review

Trigeminal neuralgia (TN) is a severe facial pain disease of unknown cause and unclear genetic background. To examine the existing knowledge about genetics in TN, we performed a systematic study asking about the prevalence of familial trigeminal neuralgia, and which genes that have been identified in human TN studies and in animal models of trigeminal pain. MedLine, Embase, Cochrane Library and Web of Science were searched from inception to January 2021. 71 studies were included in the systematic review. Currently, few studies provide information about the prevalence of familial TN; the available evidence indicates that about 1–2% of TN cases have the familial form. The available human studies propose the following genes to be possible contributors to development of TN: CACNA1A, CACNA1H, CACNA1F, KCNK1, TRAK1, SCN9A, SCN8A, SCN3A, SCN10A, SCN5A, NTRK1, GABRG1, MPZ gene, MAOA gene and SLC6A4. Their role in familial TN still needs to be addressed. The experimental animal studies suggest an emerging role of genetics in trigeminal pain, though the animal models may be more relevant for trigeminal neuropathic pain than TN per se. In summary, this systematic review suggests a more important role of genetic factors in TN pathogenesis than previously assumed.

Molecular mechanisms of trigeminal neuralgia: A systematic review

OBJECTIVE

To conduct a systematic review of the available literature for primary research articles identifying potential gene mutations, polymorphisms and other molecular regulatory mechanisms related to trigeminal neuralgia in order to identify the genetic and molecular models of primary trigeminal neuralgia currently being investigated.

METHODS

PubMed and Web of Science were systematically searched to identify primary research articles discussing genetic predictors of trigeminal neuralgia and neuropathic pain that were published prior to July 2020. This review was conducted according to PRISMA guidelines.

RESULTS

Out of the 333 articles originally identified, a total of 14 papers were selected for study inclusion. These articles included 5 human studies, 6 mouse studies and 3 rat studies. Four articles investigated sodium channels, 1 investigated a sodium channel and nerve growth factor receptor, 2 investigated potassium channels, 1 investigated calcium channels, 1 investigated the downstream regulatory element antagonist modulator protein, 1 investigated the dynorphin-kappa opioid receptor system, 1 investigated TRPA1, 1 investigated the Nrg1/ErbB3/ErbB2 signaling complex, 1 investigated a serotonin transporter and 1 investigated potassium channels, sodium channels, calcium channels, chloride channels, TRP channels and gap junctions.

CONCLUSION

Researchers have identified multiple genetic and molecular targets involved with potential pathophysiologies that have a relationship to the creation of trigeminal neuralgia. At this time, there does not seem to be clear causal frontrunner, demonstrating the possibility that genetic predisposition to trigeminal neuralgia may involve multiple genes and/or downstream products, such as ion channels.

Small Posterior Cranial Fossa and Cerebellopontine Cistern Volumes Are Associated With Bilateral Trigeminal Neuralgia

Objective: To investigate whether small volumes of the posterior cranial fossa and cerebellopontine cisterns are associated with bilateral trigeminal neuralgia (BTN) and to provide further knowledge regarding the etiology and treatment of this rare disease.

Methods: We retrospectively analyzed clinical data and imaging examination results for 30 BTN patients between January 2009 and December 2019. Thirty age- and sex-matched healthy individuals and 30 patients with unilateral trigeminal neuralgia (UTN) were selected as two control groups. The volume of the posterior cranial fossa (VPCF) and volumes of the cerebellopontine cisterns were measured using ITK-SNAP 3.0, which considers the cerebrospinal fluid (CSF) volume based on the region of interest (ROI). Preoperative and postoperative statuses were based on visual analog scale (VAS) pain scores and Barrow Neurological Institute (BNI) scores.

Results: A total of 30 patients (11 males; 19 females) were included, and the age of the BTN participants ranged from 41 to 77 (59.93 ± 9.89) years. The duration of TN ranged from 1 to 20 (5.36 ± 3.92) years, and the interval between the two sides ranged from 0 to 3 (1.10 ± 0.79) years. Three patients (10%) in the BTN group had familial trigeminal neuralgia, with no other hereditary history of neurological disorders. In BTN patients, with 25 (83.3%) cases on the left side and 26 (86.7%) on the right side, veins were identified in the operative field and regarded as the individual or offending vessel. The mean VPCF was significantly lower in the patients with BTN than in the healthy controls (4,813 ± 1,155 mm³ vs. 5,127 ± 1,129 mm³, p = 0.008). The volumes of the cerebellopontine cisterns on both sides were significantly smaller in the BTN patients than in the healthy controls (477 ± 115 mm³ vs. 515 ± 112 mm³ on the left side, p = 0.001; and 481 ± 114 mm³ vs. 515 ± 110 mm³ on the right side, p = 0.007). There was no significant difference between the BTN group and the UTN group in terms of the VPCF (4,843 ± 1,184 mm³ vs. 4,813 ± 1,155 mm³, p = 0.402), and there was also no significant difference between the two groups in terms of preoperative VAS pain scores or BNI scores.

Conclusion: Overcrowding in the posterior fossa will lead to closer neurovascular relations and, a higher incidence of NVC, and ultimately may be more likely to lead to TN. Veins are the common offending vessels that cause BTN; they might be associated with abnormal vascular development leading to NVC. Microsurgical vascular decompression (MVD) is a safe and effective method for the treatment of BTN, similar to UTN.

Exome Sequencing Implicates Impaired GABA Signaling and Neuronal Ion Transport in Trigeminal Neuralgia

Trigeminal neuralgia (TN) is a common, debilitating neuropathic face pain syndrome often resistant to therapy. The familial clustering of TN cases suggests that genetic factors play a role in disease pathogenesis. However, no unbiased, large-scale genomic study of TN has been performed to date. Analysis of 290 whole exome-sequenced TN probands, including 20 multiplex kindreds and 70 parent-offspring trios, revealed enrichment of rare, damaging variants in GABA receptor-binding genes in cases. Mice engineered with a TN-associated de novo mutation (p.Cys188Trp) in the GABA_A receptor Cl⁻ channel γ-1 subunit (GABRG1) exhibited trigeminal mechanical allodynia and face pain behavior. Other TN probands harbored rare damaging variants in Na⁺ and Ca⁺ channels, including a significant variant burden in the α-1H subunit of the voltage-gated Ca²⁺ channel Ca_v3.2 (CACNA1H). These results provide exome-level insight into TN and implicate genetically encoded impairment of GABA signaling and neuronal ion transport in TN pathogenesis.

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Genomic analysis of trigeminal neuralgia (TN) using exome sequencing

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Rare mutations in GABA signaling and ion transport genes are enriched in TN cases

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Generation of a genetic TN mouse model engineered with a patient-specific mutation

Trigeminal Neuralgia: Basic and Clinical Aspects

The trigeminal nerve is the largest of all cranial nerves. It has three branches that provide the main sensory innervation of the anterior two-thirds of the head and face. Trigeminal neuralgia (TN) is characterized by sudden, severe, brief, and stabbing recurrent episodes of facial pain in one or more branches of the trigeminal nerve. Pain attacks can occur spontaneously or can be triggered by non-noxious stimuli, such as talking, eating, washing the face, brushing teeth, shaving, a light touch or even a cool breeze. In addition to pain attacks, a proportion of the patients also experience persistent background pain, which along with autonomic signs and prolonged disease duration, represent predictors of worse treatment outcomes. It is now widely accepted that the presence of a neurovascular compression at the trigeminal root entry zone is an anatomic abnormality with a high correlation with classical TN. However, TN may be related to other etiologies, thus presenting different and/or additional features. Since the 1960s, the anticonvulsant carbamazepine is the drug of choice for TN treatment. Although anti-epileptic drugs are commonly used to treat neuropathic pain in general, the efficacy of carbamazepine has been largely limited to TN. Carbamazepine, however, is associated with dose-limiting side-effects, particularly with prolonged usage. Thus, a better understanding and new treatment options are urgently warranted for this rare, but excruciating disease.

Recent advances in understanding/managing trigeminal neuralgia

Despite recent advances in understanding and treating trigeminal neuralgia, its management remains a considerable challenge. Better classification of different types of facial pain and the identification of prognostic factors for different treatment options lead the way toward better quality of life for the individual patient. Although the principles of treating trigeminal neuralgia remain basically the same, antiepileptic drugs, muscle relaxants, and neuroleptic agents are widely used medical treatment options. They were not originally developed for treating trigeminal neuralgia. Carbamazepine was studied in adequate placebo-controlled clinical trials in the 1960s and is still considered the most effective drug. Among emerging treatment options currently under clinical investigation are local botulinum neurotoxin type A injections and a novel sodium channel blocker (CNV1014802) that selectively blocks the Na _v1.7 sodium channel. Non-pharmacological treatment options are non-invasive electrical stimulation with either transcranial direct-current stimulation or repetitive transcranial magnetic stimulation which both require further evaluation in regard to applicability. Surgical options remain a valid choice for patients not responding to medical treatment and include Gasserian ganglion percutaneous techniques, gamma knife surgery, and microvascular decompression. There is continual effort to improve these techniques and predict the outcome for better patient selection.

Familial classic trigeminal neuralgia

INTRODUCTION

The classic form of trigeminal neuralgia is usually sporadic (no familial clustering). However, around 2% of all cases of trigeminal neuralgia may be familial. Describing this entity may be useful for diagnosing this process and may also be key to determining the underlying causes of sporadic classical trigeminal neuralgia. We report on cases in a series of 5 families with at least 2 members with classic trigeminal neuralgia, amounting to a total of 11 cases.

MATERIAL AND METHODS

We recorded cases of familial classical trigeminal neuralgia between March 2014 and March 2015 by systematically interviewing all patients with a diagnosis of trigeminal neuralgia who visited the neurology department on an outpatient basis.

RESULTS

In our sample, most patients with familial classic trigeminal neuralgia were women. Mean age at onset was 62.9±13.93 years, decreasing in subsequent generations. V2 was the most frequently affected branch. Most of our patients responded well to medical treatment, and surgery was not effective in all cases.

CONCLUSIONS

These family clusters support the hypothesis that classic trigeminal neuralgia may have a genetic origin. Several causes have been suggested, including inherited anatomical changes affecting the base of the skull which would promote compression of the trigeminal nerve by vascular structures, familial AHT (resulting in tortuous vessels that would compress the trigeminal nerve), and mutations in the gene coding for calcium channels leading to hyperexcitability. Classic trigeminal neuralgia may be an autosomal dominant disorder displaying genetic anticipation.

Familial Trigeminal Neuralgia Treated with Stereotactic Radiosurgery: A Case Report and Literature Review

Background

Trigeminal neuralgia (TN) is a chronic pain condition characterized by brief episodes of lancinating pain in one or more distributions of the trigeminal nerve. Episodes of pain secondary to TN are triggered by certain stimuli, such as chewing, shaving, or touching the face. Although a common cause of TN is compression of the trigeminal nerve root entry zone by an artery or vein, many cases of TN are idiopathic. However, there have been limited reports in the literature of familial TN.

Case Presentation

A 31-year-old male presented with classic TN symptoms in the right V1/V2 distribution that recently progressed to the V3 distribution a case of familial TN. His father an brother both have TN. Carbamazepine, oxcarbazepine, and rhizotomy did not improve his symptoms. He was treated with stereotactic radiosurgery (SRS) with a dose of 85 Gy delivered to the proximal trigeminal root with improvement in his pain. We also review and summarize the over 160 cases of familial TN found in the literature.

Conclusions

This is the first reported case of familial TN treated with SRS. Patients with familial TN are more likely to have bilateral disease, to present with earlier onset, and to become refractory to medical therapy and may require more aggressive approaches. We propose that SRS is a good treatment approach for these patients.

Three common neuralgias

The pain experienced by patients with trigeminal, occipital, or postherpetic neuralgia is often severe, chronic, and difficult to treat. In this article, Drs Ashkenazi and Levin outline the pathologic mechanisms of pain in these common neuralgias and discuss individually tailored pharmacologic and surgical approaches to their treatment.

Trigeminal and glossopharyngeal neuralgia

Trigeminal neuralgia and glossopharyngeal neuralgia are two causes of paroxysmal craniofacial pain. Either can be debilitating in affected individuals. This article reviews the epidemiology, pathogenesis, diagnosis, and treatment options for these disorders.

Familial neuralgia of occipital and intermedius nerves in a Chinese family

Cranial nerve neuralgia usually occurs sporadically. Nonetheless, familial cases of trigeminal neuralgia are not uncommon with a reported incidence of 1-2%, suggestive of an autosomal dominant inheritance. In contrast, familial occipital neuralgia is rarely reported with only one report in the literature. We present a Chinese family with five cases of occipital and nervus intermedius neuralgia alone or in combination in three generations. All persons afflicted with occipital neuralgia have suffered from paroxysmal 'electric wave'-like pain for years. In the first generation, the father (index patient) was affected, in the second generation all his three daughters (with two sons spared) and in the third generation a daughter's male offspring is affected. This familial pattern suggests an X-linked dominant or an autosomal dominant inheritance mode.

Familial occipital and nervus intermedius neuralgia in a Swiss family

Familial trigeminal neuralgia has been reported in 1–2% of cases consistent with an autosomal dominant inheritance. We present a Swiss family with several members suffering from occipital and nervus intermedius neuralgia alone or in combination. We suggest that peripheral sensory anastomoses or central convergence of afferent pathways could explain neuralgia affecting two cranial nerves. The pedigree has two main characteristics: (1) affected individuals in two generations and (2) in the first generation the father is affected, in the second generation all women are affected, and none of the men. This is suggestive of an X-linked dominant or an autosomal dominant mode of inheritance.

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).

Update on trigeminal neuralgia

Trigeminal neuralgia leads to paroxysms of short-lasting but very severe pain. Between attacks, patients are usually asymptomatic, but a constant dull background pain may persist in some cases. The incidence of trigeminal neuralgia is 4.3 per 100,000 persons per year, with a slightly higher incidence for women (5.9 per 100,000) compared with men (3.4 per 100,000). There is a lack of certainty regarding the etiology and pathophysiology of trigeminal neuralgia. There are a wide range of medical and surgical treatments available. The preferred medical treatment for trigeminal neuralgia consists of anticonvulsant drugs, muscle relaxants and neuroleptic agents. Large-scaled placebo-controlled clinical trials are scarce. For patients refractory to medical therapy, Gasserian ganglion percutaneous techniques, gamma-knife surgery and microvascular decompression are the most promising invasive treatment options. Continuous scientific research works towards a better understanding of trigeminal neuralgia and has accomplished a greater insight into the underlying pathophysiological mechanisms.

[Familial trigeminal neuralgia]

Trigeminal neuralgia in its classic form is usually an isolated disease that occurs in sporadic fashion, but familial cases have been described. We report the case of a 45-year-old man who presented with left V2 trigeminal neuralgia. The neurological examination was normal and imaging and laboratory investigations were non-contributive to the etiological work-up. Carbamazepine gave excellent symptomatic relief. During patient evaluation, we became aware of a clustering of trigeminal neuralgia in four other family members over three generations. Familial trigeminal neuralgia has been expounded on in fewer than 30 reports in the literature. Our cases and the literature review suggest an autosomal dominant transmission. The clinical features of familial trigeminal neuralgia are described and pathophysiological implications of this genetic clustering discussed.

Familial risks for nerve, nerve root and plexus disorders in siblings based on hospitalisations in Sweden

BACKGROUND

Nerve, nerve root and plexus disorders are common diseases, but little is known about familial clustering in these diseases. This is, to our knowledge, the first systematic family study carried out on these diseases.

METHODS

Familial risks for siblings who were hospitalised for nerve, nerve root and plexus disorders in Sweden were defined. A nationwide database for neurological diseases was constructed by linking the Multigeneration Register on 0-69-year-old siblings to the Hospital Discharge Register covering the years 1987-2001. Standardised risk ratios (SIRs) were calculated for affected sibling pairs by comparing them with those whose siblings had no neurological disease.

RESULTS

29,686 patients, 43% men and 57% women, were diagnosed at a mean age of 37.5 years. 191 siblings were hospitalised for these disorders, giving an overall SIR of 2.59 (95% CI 1.58 to 4.22), with no sex difference. Plantar nerve mononeuritis and carpal tunnel syndrome showed the highest familial risks: 4.82 (1.08 to 16.04) and 4.08 (2.07 to 7.84), respectively. Lateral poplitean and plantar nerve neuritis preferentially affected women, with SIRs of >8; disorders of the other cranial nerves affected only men, with an SIR of >10. Concordant trigeminal neuralgia, Bell's palsy and carpal tunnel syndrome showed familial risks, but, with the exception of Bell's palsy, they also showed correlation between spouses, implying environmental sharing of risk factors.

CONCLUSIONS

The results cannot distinguish between inheritable or shared environmental factors, or their interactions, but they clearly show familial clustering, suggestive of multifactorial aetiology and inviting for aetiological research.

Idiopathic familial trigeminal neuralgia: a case report

Trigeminal neuralgia (TN) is paroxysmal, lancinant pain often described as an "electric wave" by patients, with involvement of the divisions of the fifth cranial nerve. Demyelinating, compressive, ischaemic diseases are involved in the physiopathology of TN, but there are some cases without explanation. Familial TN (FTN) is a rare condition, about 1%-2% of all TN cases, while sporadic cases are the most common. To date, there have been about 126 reports of FTN. We describe the case of a 66-year-old man who had been complaining for 3 years of right-side paroxysmal lancinating pain in the second division of the fifth cranial nerve. A brain MRI with angiographic sequences did not show neurovascular conflicts or other pathological conditions. The patient had a family history of TN, which had been diagnosed in 3 other family members (father, sister and first cousin), who had undergone medical or surgical treatment for TN. There was no family history of hypertension, metabolic disorders, neurological or traumatic diseases. Animal studies have shown a probable involvement of genes codifying for calcium channels as the starting alterations in trigeminal excitability. Our FTN could be a good model to investigate the role of gene mutations in this condition.

Trigeminal neuralgia

Trigeminal Neuralgia (TN) is a well recognized syndrome characterized by lancinating attacks of severe facial pain. The diagnosis of TN is based on a history of characteristic pain attacks that are consistent with specific widely accepted criteria for the diagnosis. TN pain attacks may result from physiologic changes induced by a chronic partial injury to the brainstem trigeminal nerve root from a variety of causes. An early and accurate diagnosis of TN is important, because therapeutic interventions can reduce or eliminate pain attacks in the large majority of TN patients.