Recognise and Manage Trigeminal Neuralgia in General Practice

Dr Carolina Venda Nova and Professor Joanna M. Zakrzewska Discuss Current Guidance on Trigeminal Neuralgia, Covering Diagnosis, Referral, and Shared Care

Trigeminal neuralgia (TN) is a rare disorder in which a person feels brief attacks of severe pain in their face. It is usually first seen in either general practice or primary dental practice, occurs most frequently in people over 50 years of age, and is more prevalent in women than men.¹

TN is a complex, long-term condition requiring a multidisciplinary approach. However, patients with symptoms of TN may be referred to a wide variety of specialists, and it can take several years before they see a specialist who follows current guidance. 

TN is associated with serious pain and uncertainty, and can have a significant impact on a person's quality of life (QOL) and mood, especially if it is poorly managed.^1–5 Studies have shown that patients with TN are at increased risk of anxiety, depression, and poor sleep;¹ in turn, these factors increase their risk of suicide.²

Specialists rely on GPs for shared care.^1,4 Therefore, it is important that primary care clinicians are aware of the condition and able to identify, manage, and refer patients with suspected TN appropriately. This article will describe the main features of TN, and explain how national guidelines can be used to ensure its optimal treatment by specialists and GPs on a shared-care basis.

Key Features and Diagnosis

TN is a unilateral, episodic condition that presents with severe attacks of facial pain usually lasting from a few seconds to a few minutes.^4,6 These attacks can be spontaneous, but may also be triggered by light touches to the face, such as from eating, showering, or cold wind.^4,5,7 The first attack of pain is often memorable, as it tends to be sudden and severe.⁴ 

It is the severity of the pain that prompts a person to see their GP, but—as the pain is often felt inside the mouth—they may instead see a dentist, who will inevitably look for a dental cause.^4,8 Many patients will therefore undergo multiple, irreversible dental treatments before receiving a diagnosis, such as filling replacements, root canal therapy, or tooth extractions, none of which will resolve the issue.⁸

Initially, patients can experience anything from one to 50 attacks per day, many of which are of high intensity.¹ Sometimes, the attacks will abate after a few weeks, but usually they continue until some form of medication is provided.^1,4,5 Even if a period of remission occurs, the pain usually returns after several weeks or months, or occasionally years.^1,4,9

Diagnosing TN

A diagnosis of TN is made based on a detailed clinical history and clinical examination, but it can be more challenging to make in primary care—especially at first presentation—as the patient's pain history tends to be shorter.^4,5 However, with time, patients usually go into remission,^4,9 and this feature may aid a clinician in diagnosis. 

Table 1 includes a few key questions to ask when considering a diagnosis of TN. It is best practice for any case of TN to be assessed and confirmed by a specialist.^3–6,9

Table 1: Key Diagnostic Questions, Corresponding to the ICHD Diagnostic Criteria^3–6,9

Secondary Causes and Differential Diagnoses

When assessing suspected TN, it is crucial to determine whether there could be a secondary cause.^3,5 Secondary causes include multiple sclerosis (MS) and brain tumours.^1,3,4,10 

TN can be the first presenting symptom of MS, and in some patients may be associated with sensory loss.¹⁰ A brain tumour, often a benign tumour such as a meningioma or a schwannoma, can also present with hearing loss and TN.^11,12 A history of malignancy or the existence of other systemic symptoms, such as fever and weight loss, should prompt early referral to the appropriate specialist services, as should the following 'red flags':⁴ 

• sensory or motor deficits
• deafness or other ear problems
• optic neuritis
• bilateral TN pain
• presentation in a person aged under 30 years.

Dental problems can mimic the symptoms of TN, so it is useful for patients to be seen by a dental professional.^4,8 In particular, cracked teeth and unilateral temporomandibular disorders (TMDs) are conditions commonly seen by dentists, and should feature in the differential diagnosis.^4,5 Patients with TN can also have TMD as a comorbidity,¹³ which could be caused by uneven use of their jaw.

Guidelines on TN

International guidelines for the management of TN have been in existence since 2008, and an updated version of European guidance was published in 2019.³ These guidelines did not involve patients or other relevant stakeholders. 

In 2021, a UK national guideline was published with the support of the Faculty of Dental Surgery of the Royal College of Surgeons of England. It was developed with input from major stakeholders in primary and secondary care, as well as from patients.⁴

Initial Management 

Imaging

At diagnosis, all patients should undergo imaging, preferably magnetic resonance imaging (MRI), to identify any underlying pathology or neurovascular compression.^3,4 Ideally, this would be performed in a specialist centre.^3,4 If MRI is not possible, computed tomography can be used instead to exclude an underlying pathology.^3,4

Optimising Treatment

As a wide range of treatments is available for TN, it is helpful to use patient-related outcome measures to guide management.^4,14 The most important outcomes of TN management, as identified by patients and experts, include pain relief, pain interference, side effects of treatment, health-related QOL, satisfaction with treatment, and the ability to participate in social roles and activities.¹⁵ Patients should be encouraged to keep pain diaries, as they can help to gauge the effectiveness of treatment and inform medication adjustments and treatment escalation.⁴ 

Providing Information to Patients

When providing information to a patient about TN and its management, a clinician may wish to show them the national guideline, which includes a lay summary.⁴ It may also be useful to give patients separate written information about TN as well, covering both pharmacological and surgical options.⁴ The Brain and Spine Foundation, for example, offers a booklet covering all forms of facial pain, in particular TN—bit.ly/3CEpgos.¹⁶

Pharmacological Management

Carbamazepine and oxcarbazepine

Carbamazepine is seen as the gold standard for initial pharmacological management, and is recommended for TN in NICE guidance on the management of neuropathic pain in nonspecialist care.^3,17 However, the NICE guideline does not provide any guidance on prescribing.¹⁷ With carbamazepine, it is important to start with low doses¹⁰—the British National Formulary (BNF) recommends 100 mg one to two times per day, to be increased gradually according to response to a usual dose of 200 mg three to four times a day, up to a maximum of 1.6 g daily (if necessary).¹⁸ 

If carbamazepine cannot reach the therapeutic dose owing to intolerable side effects, if it fails to provide adequate pain relief, or if there is an absolute contraindication due to a drug interaction, oxcarbazepine can be prescribed, with a therapeutic range that is usually between 1200 and 1800 mg/day, separated into four doses.⁴ Oxcarbazepine is likely to be more effective than gabapentin or pregabalin. GPs can prescribe oxcarbazepine, although its use for TN is off licence; NICE guidance states that, if initial treatment with carbamazepine is unsuccessful, advice should be sought from a specialist.¹⁷

In the initial stages, carbamazepine can be considered a diagnostic drug, with many cases of TN responding quickly and effectively.³ However, side effects are common.^3,4,18 Moreover, as carbamazepine is eliminated by the cytochrome P450 system, drug interactions with it are also common¹⁹—clinicians should be mindful of this, and be sure to check the BNF when prescribing.

When considering a carbamazepine or oxcarbazepine prescription, testing for the presence of the HLA-B*1502 allele is recommended in individuals of Han Chinese or Thai origin, as there is an increased risk of carbamazepine-induced Stevens–Johnson syndrome in this group.^4,18,20,21

Alternative Drugs

Even though the pain from TN can be very severe, use of opioids is not recommended as they are ineffective for the management of TN.^3,4 Other drugs, such as amitriptyline, gabapentin, and pregabalin, are alternatives to carbamazepine, but are much less likely to be effective in the early stages and should only be initiated by specialists.⁴ Some patients may also need to take more than one anti-epileptic drug.⁴ In any case, if treatment has failed with carbamazepine monotherapy, patients should be referred to specialist centres for further guidance and treatment.^4,17 

Table 2 provides details of the main drugs indicated for TN.^{4,5,7,18,21–27} When prescribing, all healthcare professionals should consult the relevant BNF pages and summaries of product characteristics, particularly when considering off-licence use, and should provide patients and carers with written information and a dosage schedule.⁴ Specialists should also share information on medication schedules with a patient's GP, as they are often asked to continue drugs on prescription and arrange blood tests for monitoring. 

There is some flexibility around dosage escalation should a flare-up occur suddenly.⁴ Adjuvant medications can be prescribed for acute attacks (see Relapses and Acute Therapy, below).^4,5

Table 2: Drug Therapy for TN^{4,5,7,18,21–27}

Relapses and Acute Therapy

There is little available evidence on the natural history of TN, including on the length of remission and relapse periods. It is therefore difficult to provide a prognosis. Nevertheless, the national guideline recommends that patients slowly reduce and stop their medication when they are in a period of remission—that is, more than 4 weeks with no attacks.⁴ Some patients will be fearful of doing this, and may prefer to remain on a low dose of their medication.⁴

Relapses can start suddenly, and therefore require prompt action, often by a GP. Usually, it is best practice to restart the patient's last-used medication.⁴ If this is not effective, particularly for an acute exacerbation of pain, other drugs may need to be offered.^3,4 Occasionally, it will be necessary to combine two drugs.^3,4

Lidocaine

Lidocaine can be helpful for relieving acute exacerbations, and can be bought over the counter or given via prescription as a spray or an ointment.^4,5,28 Lidocaine is most useful for intraoral use if there is an intraoral trigger, and can be particularly helpful for patients who have difficulty eating and brushing their teeth.⁴ 

A dentist, oral surgeon, or TN specialist could also give a patient a local anaesthetic injection (lidocaine, with or without adrenaline) into the trigger-point area, which can be combined with a longer-acting agent such as bupivacaine.⁴ This would only provide a few hours of pain relief, but can be repeated daily until systemic drugs have reached their effective dose.⁴ 

In severe flare-ups, especially when associated with dehydration, patients should be admitted for treatment, ideally to a setting where a neurology team is available.^3,4 These patients may require emergency surgery or intravenous medication.^3,4

Surgery

TN is one of the few chronic pain conditions in which surgical options can result in better outcomes than medical management.^4,14 Surgery is a common choice for people with TN; in fact, a recent study conducted at a large teaching hospital found that over 50% of its patients with TN underwent surgery.¹⁴ However, surgery is irreversible, is associated with complications, and is not always fully effective—in the study, of those who underwent surgery, 55% of patients were free of pain and no longer taking medication, meaning that almost half of patients who underwent surgery were still affected by TN.¹⁴ Careful diagnosis is therefore imperative.

Patients should discuss surgical options early and while they are stable,^3,4 so that they can think through their options in a rational way. It can be useful to give patients a decision aid such as the Ottawa Personal Decision Guide,²⁹ which can help them in discussions with other patients, family members, and healthcare professionals.^4,14

There is no strong evidence concerning the best time for surgery, but the following need to be considered:^3–5

• use of multiple medications with diminishing efficacy
• poor tolerability of medication
• significant impact on mood and QOL.

Of all the available procedures, only microvascular decompression (MVD)—a major neurosurgical procedure—aims at preserving the trigeminal nerve and removing one of the possible causes of the condition, a large vessel pressing on the nerve.^3–5 All other procedures are termed ablative or destructive, as they aim to damage pain fibres, and can result in sensory loss.^3–5 

Complications After Surgery 

Cerebrospinal Fluid Leak

Patients may develop a cerebrospinal fluid leak 7–10 days after MVD, which can manifest itself as a leak through the wound, ear, or nose, and must be dealt with promptly by the neurosurgeon who carried out the procedure.^4,14

Sensory loss

The most significant long-term complication of surgery is sensory loss.^4,5 This can vary in severity and distribution, and needs to be addressed and managed appropriately. The most severe form is anaesthesia dolorosa,^3,5 a condition in which the patient feels complete numbness in the area innervated by the trigeminal nerve with an added continuous sharp pain. Some patients tolerate mild sensory changes, but in others they can lead to continued use of neuropathic drugs and a significant impact on mood and QOL.^3,4 

Patients who have lost their corneal reflex need to be given precise instructions on eye care and encouraged to wear glasses with side plates when going out in windy conditions.⁴ Hearing loss can be temporary, but in some will be permanent; unfortunately, little can be done about this.¹⁴

Relapse

As surgical procedures are not curative, relapses are likely to occur. In some cases, these can be managed with drug therapy; in others, repeat surgery can be performed.¹ 

Other Support

It is now recognised that the pain, unpredictability, and reduced ability to carry out daily activities associated with TN are likely to have significant effects on a person's mental health, resulting in depression and anxiety.^1,3,4 Therefore, patients will benefit from access to pain-management programmes,^1,4 which can help them to improve their QOL.^3,4,17

Specialist centres will often have clinical nurse specialists (CNSs), who are independent prescribers and can therefore arrange telephone consultations and advise patients on managing their medication.⁴ CNSs can also discuss the adjustment of drug dosages and prescriptions with GPs.⁴

Outside of healthcare services, people with TN may benefit from talking to other people with the condition.^1,4 Trigeminal Neuralgia Association UK (TNA UK) is a charity offering help and support to people with TN, and offers a dedicated helpline run by volunteers.^4,30 TNA UK also organises webinars, local support groups, and an annual conference. The charity is supported by a medical advisory board.

Summary

TN is a condition of unilateral, severe, episodic, facial pain that is provoked by light touch. Initially, it is usually well controlled with carbamazepine. National guidance provides details for both primary and secondary care practitioners on diagnosis, investigation, and management, which can be both pharmacological and surgical.