Introduction

Trigeminal neuralgia (TN) is characterized by recurrent, intense, and electric shock-like pain episodes on one side of the face, lasting briefly. These episodes can severely disrupt daily activities, causing a significant decline in the overall quality of life. Epidemiological studies highlight the profound impact of TN, leading to increased anxiety, depression, and a higher risk of suicide. Early diagnosis, proper investigations, and prompt treatment are crucial to address the debilitating effects of this condition. [1]

Trigeminal neuralgia (TN) is estimated to affect 0.16%–0.3% of the population throughout their lifetime, with an annual incidence varying from 4 to 29 cases per 100,000 person-years. Women are more commonly affected, with a ratio of 3 to 2 compared to men. The incidence of TN tends to rise with age, and it typically emerges in individuals between 53 and 57 years old, although cases have been reported across a wide age range from 24 to 93 years in adults. TN is not exclusive to adults and can also occur in children, as evidenced by cases found in children aged between 9.5 and 16.5 years in recent studies. [1]

Classification Of Trigeminal Neuralgia

Trigeminal Neuralgia (TN) can be classified into three main types -

* Type I, also known as typical TN, is characterized by severe, unilateral, and brief paroxysms of sharp pain in the trigeminal nerve's distribution. These attacks are often triggered by non painful stimuli, such as cold air, brushing teeth, chewing, or talking. [2]

* Type II TN includes continuous or near-continuous pain in addition to the sharp attacks seen in Type I TN. Both Type I and Type II can be classified as idiopathic TN if no vascular compression is found on imaging, or classic TN if neurovascular compression is present. [2]

* Secondary TN is pain in the trigeminal distribution caused by other neurological diseases, such as inflammatory/demyelinating conditions, tumors, vascular lesions, connective tissue disorders, congenital diseases, or systemic conditions affecting the trigeminal nerve.[2]

Pathophysiology

Trigeminal neuralgia is characterized by chronic nerve compression, resulting in demyelination and degeneration of nerve fibers, leading to heightened sensory inputs through ephaptic transmission. Structural and biochemical changes occur in the trigeminal nerve root and Gasserian ganglion, accompanied by nerve atrophy. Brain imaging reveals reduced volume in pain-related brain regions and altered functional connectivity, but the exact relationship with TN requires further research for better management.[3]

Clinical Presentation [3,4]

*  Unilateral facial pain: Trigeminal neuralgia typically presents with severe, unilateral facial pain.

* Electric shock-like pain: The pain is often described as sudden, intense electric shock-like sensations.

* Trigeminal distribution: The pain follows the distribution of one or more branches of the trigeminal nerve (forehead, cheek, jaw).

* Brief duration: Pain episodes last for a very short duration, usually a few seconds to a couple of minutes.

* Triggered by non painful stimuli: Attacks can be triggered by activities like talking, chewing, brushing teeth, or exposure to cold air.

* Refractory periods: Between episodes, there are periods of relief when previous triggers no longer provoke pain.

* Weight loss and dehydration: Avoidance of triggers may lead to weight loss and dehydration in severe cases.

Diagnosis Of Trigeminal Neuralgia [3,4]

* Clinical evaluation: TN is primarily diagnosed based on clinical presentation and history of severe, unilateral electric shock-like facial pain.

* Subtle sensory abnormalities: Quantitative sensory testing may reveal subtle sensory abnormalities that may not be evident in routine clinical examination.

* MRI imaging: Magnetic Resonance Imaging (MRI) is used to detect changes in the trigeminal root and rule out secondary pathology.

* Trigeminal root changes: Diffusion Tensor Imaging (DTI) can detect changes in the trigeminal root, including increased apparent diffusion coefficient and decreased fraction of anisotropy.

* Vascular conflict detection: 3D FIESTA and contrast-enhanced 3D Time-of-Flight (TOF) Magnetic Resonance Angiography (MRA) can help identify vascular conflicts with the trigeminal nerve.

* Image fusion technology: 3D high-resolution MRI and image fusion technology provide detailed anatomical relationships between neural and vascular structures, aiding in the diagnosis of neurovascular compression.

* 3T MRI: In cases of equivocal findings with 1.5-T MRI, 3-T MRI can be valuable for preoperative assessment of compressing vessels.

Treatment for Trigeminal Neuralgia

Medical Treatment

Carbamazepine (CBZ) is the drug of choice for TN, but other anticonvulsant drugs like baclofen, lamotrigine, clonazepam, oxcarbazepine, topiramate, phenytoin, gabapentin, pregabalin, and sodium valproate can also be used.

* Combination of multiple drugs may be beneficial for patients unable to tolerate higher doses of CBZ.

* Intravenous infusion of magnesium and lidocaine combination can be effective in some cases.

*  Lidocaine plaster and capsaicin patch may be useful for certain individuals with TN.

* 5-HT R3 antagonists, neurokinin-1 antagonists, or mast cell stabilizers may have a role in treatment.

* A multidisciplinary approach using antidepressants and anti-anxiety drugs like amitriptyline and duloxetine is important for managing emotional status.

*  Botulinum toxin Type A injections can be considered before surgery or for those unwilling to undergo surgery, and in cases of failed drug treatment.

* Additional treatments such as tetracaine nerve block, acupuncture, and peripheral nerve stimulation may be used along with CBZ.

* Deep brain stimulation of the posterior hypothalamus can be considered as an adjunctive procedure for refractory TN of the first division, particularly in multiple sclerosis (MS).

* Motor cortex stimulation may be applicable for certain neuropathic or deafferentation pain.

Surgical Interventions [3,5]

Gamma Knife Radiosurgery (GKRS):
* Radiation blocks excessive sensory information responsible for triggering pain attacks. GKRS can be used in typical or atypical TN, with or without vascular compression, and in recurrence after other treatments. Initial pain relief is around 77%-96%, with long-lasting pain relief in more than 50% of cases.
Percutaneous Balloon Compression (PBC):
*  PBC is indicated for patients with significant medical comorbidities, multiple divisions involved, and in repeat cases.It provides about 90% temporary pain relief with some complications.
Glycerol Rhizotomy (GR):
* GR is indicated in patients unresponsive to pharmacotherapy, MS, unilateral and bilateral pain, and after failed MVD. Immediate success rate is about 95% with a recurrence rate of around 50% at 24 months follow-up.
Radiofrequency Thermocoagulation (RFTC):
* RFTC can be used in various cases, including bilateral pathology, elderly patients, and after failed MVD. Initial pain control rate is about 95%, but there can be a recurrence of about 25%.
Microvascular Decompression (MVD):
*  MVD is indicated in TN with neurovascular compression. It has an immediate success rate of about 90%-95%, but recurrence can be seen in about 18%-34% at long-term follow-up. Certain predictors like preoperative duration, age, and typical features can influence the outcome.
Frequently Asked Questions:
1. What are the common triggers for trigeminal neuralgia?
A: Triggers for trigeminal neuralgia can vary from person to person but often include activities such as brushing teeth, chewing, talking, or exposure to cold air. Even light touch or movement of certain areas on the face can trigger pain.
2. Is trigeminal neuralgia curable?
A: Trigeminal neuralgia is considered a chronic condition, and a complete cure is not always possible. However, with appropriate treatment, many patients experience significant pain relief and improved quality of life.
3. Can stress or anxiety trigger trigeminal neuralgia attacks?
A: Stress and anxiety are known to exacerbate trigeminal neuralgia symptoms in some individuals. Practicing stress-reduction techniques may help manage the condition better.
4. Can trigeminal neuralgia be hereditary?
A: Trigeminal neuralgia is generally not considered a hereditary condition. However, in rare cases, there may be a genetic predisposition.

References

1. Lambru, G., Zakrzewska, J., & Matharu, M. (2021). Trigeminal neuralgia: a practical guide. Practical Neurology, 21(5), 392–402.
2. Xu, R., Xie, M. E., & Jackson, C. M. (2021). Trigeminal neuralgia: Current approaches and emerging interventions. Journal of Pain Research, 14, 3437–3463.
3. Yadav, Y. R., Nishtha, Y., Sonjjay, P., Vijay, P., Shailendra, R., & Yatin, K. (2017). Trigeminal neuralgia. Asian Journal of Neurosurgery, 12(4), 585–597.
4. Trigeminal neuralgia. (n.d.). Aans.org. Retrieved August 12, 2023, from https://www.aans.org/Patients/Neurosurgical-Conditions-and-Treatments/Trigeminal-Neuralgia
5. Trigeminal neuralgia. (n.d.). National Institute of Neurological Disorders and Stroke. Retrieved August 12, 2023, from https://www.ninds.nih.gov/health-information/disorders/trigeminal-neuralgia