Case of the Month #36: Facial pain by Dr Ameana Khan & Dr Shefali Kadambande

Pharmacological

The management of TN necessitates a thorough assessment, involving investigation of potential red flags through comprehensive history and examination. Addressing the underlying causative condition holds importance in the overall management strategy.

In the predominant instances of TN, the primary pharmacological intervention revolves around the use of carbamazepine, the only licensed medication demonstrating established efficacy (Number Needed to Treat, NNT: 1.9)^₁. Due to potential side effects associated with carbamazepine, such as hyponatremia, leukopenia, and thrombocytopenia, regular blood profile monitoring is important⁶. Additionally, the presence of the HLA-B 1502 allele in individuals of Han Chinese or Thai origin is strongly associated with an increased risk of Steven’s-Johnson syndrome⁶. Adhering to NICE guidelines, primary care practitioners are advised to consider specialty referral, particularly to a neurologist or specialised pain service, when carbamazepine is contraindicated, ineffective, or poorly tolerated².

Oxcarbazepine, a derivative of carbamazepine, emerges as a better-tolerated alternative with an improved side-effect profile while maintaining similar efficacy. In cases where carbamazepine is unsuitable, ineffective, or poorly tolerated, alternative agents like lamotrigine, baclofen, gabapentin, pregabalin, and amitriptyline may be considered, although their specific evidence supporting effectiveness in TN is limited^1,2. Vigilant blood monitoring is essential, particularly with high doses, to mitigate potential side effects such as bone marrow suppression and organ damage⁴. For acute flare-ups, there has been some success with phenytoin and lidocaine infusions, as well as local anaesthetic peripheral nerve blocks. These treatment options provide a diversified approach in managing TN, considering both the chronic symptoms and acute exacerbations.

Interventional

For individuals failing drug therapy or experiencing significant side effects, surgical intervention may be considered, falling into two main categories: open cranial surgery and lesioning procedures. The decision for open surgery is prompted by diagnostic imaging, especially MRI scans revealing pressure on the trigeminal nerve attributed to a nearby blood vessel.

Surgical

Open cranial surgery specifically Microvascular Decompression (MVD), entails the exposure of the trigeminal nerve root, identifying a potentially compressing blood vessel, and relocating the vessel away from the compression site⁴. This decompression procedure aims to alleviate sensitivity, promoting the recovery of the trigeminal nerve towards a more normal, pain-free state. MVD stands out with an initial success rate of 80–90%^7,8, offering the most sustained pain relief among available procedures. However, it's important to recognise that the relapse rate after a decade is approximately 30–40%^7,8.

Lesioning procedures

Stereotactic radio-surgery, administer a focused, single dose of ionising radiation precisely to the trigeminal nerve root. Over time, a lesion forms in the nerve, disrupting the transmission of pain signals to the brain. Although providing complete pain relief in up to 69%^7,8 of patients within the first year, the benefits may not be sustained. However, it is possible to repeat the procedure for recurrent TN if deemed appropriate.
Percutaneous interventions precisely target the gasserian ganglion to disrupt pain signals, using mechanical damage through balloon compression, chemical damage with agents like phenol, alcohol, and glycerol, and thermal damage via radio-frequency ablation. These procedures, involving Fluoroscopy-guided needle entry through the cheek into the foramen ovale, offer substantial pain relief, with approximately 50% of cases experiencing lasting effects for 4-5 years^7,8.
Both open and lesioning procedures carry risks of failure, ipsilateral deafness, dysaesthesia, jaw weakness, facial numbness, double vision, stroke, or death. Clinicians must evaluate patients based on their co-morbidities and their perception of the distinct risks associated with these procedures. Informed decision-making by patients involves a thorough understanding of the options, related risks, and likely outcomes^7,8.

Other

Furthermore, case studies have demonstrated favourable responses to various modalities, including transcutaneous electrical nerve stimulation, acupuncture, botulinum toxin A, and the application of 5% lidocaine patches^5,6,8.

Novel Treatments   

In certain medical centres, neuromodulation emerges as a prospective avenue for treatment, albeit with a limited evidence base. Noteworthy instances of positive outcomes in managing Trigeminal Neuralgia (TN) have surfaced in relation to Transcranial Magnetic Stimulation (TMS) a non-invasive technique that uses magnetic fields to change brain activity. A magnet is placed on the patient's head which converts electrical current into a magnetic field, targeting different brain areas. Low frequencies inhibit neurones, while high frequencies increase activity. Stimulation of specific brain regions such as the primary motor cortex can relieve pain, likely by activating certain brain fibres⁹. 

Psychological support 

Individuals diagnosed with TN exhibit a 2.8-fold higher likelihood of experiencing depressive disorder, anxiety, or sleep disorders⁹. Recognising this association highlights the necessity for an integrated approach to TN management. Implementation of therapeutic interventions, notably cognitive-behavioural therapy, holds considerable promise in addressing the impact of TN symptoms^10,11. Additionally, guiding patients towards informative resources and signposting connections within relevant support networks, such as the Trigeminal Neuralgia Association UK¹² and the Brain and Spine Foundation¹³, can enhance their understanding and coping mechanisms.