Trigeminal neuralgia (TN), a neuropathic pain syndrome, is defined by the International Association for the Study of Pain as “a sudden and usually unilateral severe brief stabbing recurrent pain in the distribution of one or more branches of the trigeminal nerve 1).
Also known as prosopalgia, or Fothergill's disease.
It has been described as among the most painful conditions known to mankind.
Trigeminal neuralgia is a relatively common neurosurgical pathology
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). 2)
In a majority of cases, TN symptoms begin appearing more frequently over the age of 50, although there have been cases with patients being as young as three years of age. It is more common in females than males.
One, two, or all three branches of the nerve may be affected.
10-12% of cases are bilateral (occurring on both the left and right sides of the face). Trigeminal neuralgia most commonly involves the middle branch (the maxillary nerve or V2) and lower branch (mandibular nerve or V3) of the trigeminal nerve, but the pain may be felt in the ear, eye, lips, nose, scalp, forehead, cheeks, teeth, or jaw and side of the face.
Trigeminal neuralgia can be subdivided according to the Burchiel scheme into trigeminal neuralgia types 1, 2a, and 2b. Such classification is important because it is predictive of surgical success.
Patients with type 1 TN experience a memorable onset of symptoms often described as a “lightning-bolt of pain that came out of nowhere.” The pain, while severe, tends to last for only seconds at a time and may occur many times per day. Even though attacks become more frequent, the pain is always shock-like and never constant or dull. Although attacks often occur spontaneously, patients with type 1 TN usually report certain triggering factors such as cold wind, eating, drinking, or using a washcloth. Additionally, patients with type 1 TN tend to have spontaneous remissions of symptoms lasting days to weeks early in the course of the disease with these pain-free intervals becoming shorter and less frequent as time passes. Patients with type 1 TN have the most favorable outcomes following any treatment modality.
In contrast, patients with type 2b trigeminal neuralgia have a more insidious onset of pain. Rather than experiencing a “lightning bolt out of nowhere,” patients may initially believe that they have a tooth or sinus ache for many months before the pain is determined to be neurologic. The pain is often described as being dull, boring, constant, aching, or throbbing. Like type 1 trigeminal neuralgia, the symptoms are extremely disabling. The prognosis following surgical treatment of patients with type 2b trigeminal neuralgia is less favorable than in patients with type 1 trigeminal neuralgia. However, patients who respond favorably to anticonvulsant medication may still benefit from an operation.
Type 2a trigeminal neuralgia is the diagnosis applied to patients who have type 1 symptoms early in the disease course and transition, over time, to a more constant pain consistent with type 2b trigeminal neuralgia. The outcomes of these patients following a surgical treatment is thought to be more favorable than in patients with type 2b trigeminal neuralgia but less favorable than in patients with type 1 trigeminal neuralgia.
The Visual Analog Scale (VAS) and the Barrow Neurological Institute Pain Scale (BNI-PS) are 2 of the most frequently employed patient-reported outcome (PRO) tools used by clinicians to rate pain for patients with trigeminal neuralgia (TN).
Reinard et al., from the Department of Neurosurgery, Henry Ford Medical Group (HFMG), and the Wayne State University School of Medicine, Detroit, Michigan, identify racial and socioeconomic disparities in the diagnosis and treatment of trigeminal neuralgia (TN), this appeared to stem from outside HFMG from a difference in referral patterns to the neurologists and neurosurgeons 3).
Trigeminal Neuralgia can be a typical symptom in cerebellopontine angle tumours like epidermoid, especially in young patients, so all the patients with trigeminal neuralgia should be investigated for lesion in cerebellopontine region 4).
Magnetic resonance imaging (MRI) can be helpful in visualizing neurovascular conflict (NVC) of the trigeminal nerve, but the relationship between these two events is controversial.
Trigeminal neuralgia (TN) recurring after surgery can be difficult to treat. Treatment algorithms have not been standardized or universally accepted.
The records of 22 patients (13 M and 9 F) suffering recurrent TN after one (2 gamma knife surgery, 5 percutaneous radiofrequency rhizotomy, 6 percutaneous retrogasserian glycerol rhizotomy, 3 microvascular decompression) or more (6 patients) procedures were reviewed. Seven patients had TN related to multiple sclerosis (MS). Mean follow-up was 51.81 ± 26.63 months. 81.81 % of patients reported an acute pain relief. No major complication was observed after PBC. Eight patients (36.36 %) experienced pain recurrence and underwent one (five patients) or more (three patients) PBC. At the last follow-up, we obtained an excellent outcome (BNI I-II) in 16 patients out of 22 (72.72 %) and a good outcome (BNI III) in the remaining six. No patients had an uncontrolled pain. The lack of history of MS (p = 0.0174), the pear-like shape of the balloon at the operation (p = 0.0234) and a compression time <5 min (p < 0.05) were associated to higher pain-free survival. Considering these results PBC could be considered a useful technique for patients whose pain recurs after other procedures 5).
Although no procedure is best for all patients, posterior fossa exploration PFE gives the operating surgeon the option of performing either a nondestructive (microvascular decompression) or destructive (partial sensory rhizotomy) procedure and is associated with better facial pain outcomes for this difficult patient group 6).
The study of Montano et al., shows no differences in the short term results among different procedures for TN in MS patients. Each technique demonstrate advantages and limits in terms of long term pain, recurrence rate and complication rate. Each patient should be accurately informed on pros and cons of each procedure in order to be involved in the most appropriate choice 7).
Mortality rates for MVD (0.22%), rhizotomy (0.42%), and SRS (0.12%) were low 8).
Forty-three patients with trigeminal neuralgia were recruited, and diffusion tensor imaging was performed before radiofrequency rhizotomy. By selecting the cisternal segment of the trigeminal nerve manually, they measured the volume of trigeminal nerve, fractional anisotropy, apparent diffusion coefficient, axial diffusivity, and radial diffusivity. The apparent diffusion coefficient and mean value of fractional anisotropy, axial diffusivity, and radial diffusivity were compared between the affected and normal side in the same patient, and were correlated with pre-rhizotomy and post-rhizotomy visual analogue scale pain scores. The results showed the affected side had significantly decreased fractional anisotropy, increased apparent diffusion coefficient and radial diffusivity, and no significant change of axial diffusivity. The volume of the trigeminal nerve on affected side was also significantly smaller. There was a trend of fractional anisotropy reduction and visual analogue scale pain score reduction (P = 0.072). The results suggest that demyelination without axonal injury, and decreased size of the trigeminal nerve, are the microstructural abnormalities of the trigeminal nerve in patients with trigeminal neuralgia caused by neurovascular compression. The application of diffusion tensor imaging in understanding the pathophysiology of trigeminal neuralgia, and predicting the treatment effect has potential and warrants further study 9).
Between January 2003 and December 2013, 360 patients with idiopathic TN and 39 patients with tumor-related TN who had undergone microsurgery were retrospectively studied. Kaplan-Meier survival curves were generated and compared by Log-rank test, and the possible prognostic factors were analyzed by the Cox proportional-hazards regression.
Patients with tumor-related TN exhibited a younger age of pain onset (46.28 ± 18.18y vs. 53.03 ± 11.90y, p = .006), a briefer symptom duration (3.20 ± 4.38y vs. 7.01 ± 6.04y, p = .000), and much more preoperative neuropathic deficits (61.54 vs. 24.17, p = .000), as compared with patients with idiopathic TN. Using Kaplan-Meier analysis, we found microsurgery was effective in 72.3% of patients with idiopathic TN, and in 86.4% of cases with tumor-related TN at six years follow-up postoperatively. Prognostic analysis suggested that a clear-cut neurovascular compression in patients with idiopathic TN (HR = 3.098, 95%CI: 1.800-5.311; p = .000) and total tumor removal in patients with tumor secondary TN (HR = 7.662, 95%CI: 0.098-36.574; p = .044) were positively correlated with excellent long-term outcomes.
The occurrences of TN at younger age, a shorter duration and preponderance of preclinical neuropathic symptoms are the characteristics of TN patients secondary to intracranial tumor, in contrast to patients with TN caused by a compressed vessel. Microsurgery is an effective and safe treatment modality for TN regardless of the disease etiology, the involvement of a clear-cut vascular offender and total tumor resection are the most important predictors of excellent outcome for microsurgery in idiopathic and tumor-related TN patients, respectively 10)