A cross-sectional study was conducted using the medical records of 60 adult patients with Trigeminal Neuralgia who attended the Neurology outpatient department at Travancore Medical College, Kollam between June 2015 and June 2020. This study was approved by Institutional Ethics committee Review Board (TMC/069/20).

Inclusion criteria and Exclusion criteria:

Patients diagnosed with trigeminal neuralgia as per the Criteria of the International Headache Society (ICHD 3), were included in the study [5]. Patients were excluded if: (a) with atypical facial pain (as per ICHD3); (b) not fulfilling the criteria for trigeminal neuralgia; (c) patients with prior history of neurosurgery procedure; (d) patients with prior history of trauma; (e) patients whose work up is incomplete/MRI is not done; (f) associated connective tissue disorder.

The following variables were studied: (a) Age; (b) Gender; (c) Dental treatment/tooth extraction; (d) Severity of pain based on Numeric Pain Rating scale {0-No Pain, 1 to 3- Mild Pain, 4 to 6- Moderate Pain and 7 to 10- Severe Pain}; (e) Trigger factors- chewing, touch, brushing teeth, eating, talking, breeze; (f) Side- left/right/bilateral; (g) Area involved V1/V2/V3/V1+V2/V2+V3/V1+V2+V3; (j) Sensory abnormalities: hypoesthesia, hyperesthesia, allodynia, hypoalgesia; (h) MRI.

MRI Brain of the 60 patients in the study was conducted with 1.5T Siemens unit system. The protocols used were: axial T1, T2, FLAIR, 3D CISS, postcontrast T1 series in case of suspicious lesions. Neurovascular compression with atrophy or displacement in the trigeminal nerve root, structural lesion, infarct, demyelinating plaque, space occupying lesion was assessed.

Based on the subtypes of trigeminal neuralgia (Classical, Secondary and Idiopathic), various clinical features were analysed.

Recurrent paroxysms of unilateral facial pain in the distribution(s) of one or more divisions of the trigeminal nerve, with no radiation beyond, and fulfilling criteria B and C

Data was analysed with SPSS statistical software. (SPSS, version 20.0, Chicago, IL, USA). Categorical variables were presented in number and percentage and were compared using Chi-square test. A p<0.05 was considered statistically significant.

Among the 60 patients studied with trigeminal neuralgia, 26 (43.3%) were males and 34 (56.7%) were females. About 25 had maxillary nerve division distribution (41.7%), 57 patients experienced shock/lancinating pain (95%), touch and breeze as common trigger factors in 54 (90%). The median age among males was 52.4 years and females were 56.5 years [Table/Fig-1].

About 26 patients (43.3%) were in the age group 55-64 years. Of the total 34 females in the study group, 15 (44.1%) were in 55-64 year age group [Table/Fig-2].

[Table/Fig-2]:

Age-sex distribution.

Based on the MRI findings 31 patients (51.7%) showed neurovascular compression with atrophy or displacement in the trigeminal nerve root (Classical trigeminal Neuralgia). MRI of five patients (8.4%) revealed- Schwannoma (1), Meningioma (1), Demyelination (2) and Infarct (1) (Secondary trigeminal neuralgia). About 24 (39.9%) had normal MRI findings (Idiopathic trigeminal neuralgia). In the study, hypoesthesia was the only sensory examination finding found in all the five patients of secondary trigeminal neuralgia. 90% of patients had trigger factors; the most common of which were touch (86.6%) and breeze (70%). Involvement of dual divisions (V2 and V3), absence of trigger factors and evidence of hypoesthesia were found in all patients of Secondary Trigeminal neuralgia (p<0.001) [Table/Fig-3].

Trigeminal neuralgia, though uncommon is a disturbing and disabling pain disorder. Despite a typical clinical presentation, it can sometimes be missed in an outpatient setting.

In the study, among the 60 patients studied with trigeminal neuralgia, 56.7% were females. The median age among males was 52.4 years and females were 56.5 years. Most common age group was between 55-65 years. In the study by Rai A et al., 55% were males, with average age of 58.97 years for males and 59.96 years for females [8]. Maarbjerg S et al., did a prospective systematic study of clinical characteristics in 158 patients. The prevalence of women (60%) was significantly higher than that of men with average age of onset 52.9 years [9]. In the study by Katheriya G et al., peak age of onset was between the 5^th and the 6^th decades of life. Females (59.2%) were more predilected for neuralgia than males [10]. These studies results were in agreement with present study results.

In the present study, right side of the face was more commonly involved than the left. Both sides were equally affected in the study by Rai A et al., [8]. In most of the studies, it has been observed that the right side of the face was affected more frequently than the left side [9,10].

Regarding the division of trigeminal nerve involved, it was found that maxillary (V2) and mandibular (V3) divisions were involved in 25 (41.7%) and 19 (31.7%) patients, respectively, while in remaining 16 (26.6%) patients, both V2 and V3 nerves were involved. The result was in consistent with the study by Rai A et al., [8]. Mandibular nerve was more commonly involved in the study by Katheriya G et al., [10]. However, all these studies had same observation that the combinations of V2+V3 were less common as similar to present study.

The diagnosis of trigeminal neuralgia is highly dependent on the character, duration and severity of the pain. In the study, the most commonly described character was shock like/lancinating (95%) with a severity of 4-6 (66.7%) on the Numerical pating pain scale. The most common pain descriptor was shock like pain in Rai A et al., study, stabbing pain in Maarbjerg S et al., study and sharp pain in Jainkittivong A et al., study [8,9,11].

Sensory findings (hypoesthesia) were observed in 8.4% patients. The most common trigger factors in the study were touch and breeze. In the study by Maarbjerg S et al., chewing and touch were the most common trigger factors and significant proportion of surgery naïve patients had sensory abnormalities [9].

The pain of trigeminal neuralgia is sometimes falsely attributed to dental origin [12]. In the study, previous dental treatment/procedure was undertaken by 63.3% of patients. In the study by Rai A et al., 13.33% underwent dental treatment [8]. Furthermore, Jainkittivong A et al., described that many patients with trigeminal neuralgia have lost teeth because of unnecessary extractions; odontogenic pain being a common misdiagnosis [11]. Thus, serious caution should be taken in cases where it may be perceived initially as an episodic toothache.

In the present study based on MRI correlation, Classical trigeminal neuralgia was the most common sub type that showed neurovascular compression with atrophy or displacement of trigeminal nerve root [Table/Fig-4]. In the study by Masur H et al., about 33.3% of patients had no neurovascular contact in MRI [13]. In a study by Nevan G et al., 62% had vessels seen abutting, or immediately adjacent to the trigeminal nerve on the side of their symptoms [14]. Analysis by Antonini G et al., showed that trigeminal root entry zone neurovascular contact was detected in 76% of symptomatic nerves [15].

[Table/Fig-4]:

MRI 3D-CISS axial image showing neurovascular impingement of right trigeminal nerve.

In present study, when the clinical features were compared between the various three subtypes, division of trigeminal nerve, trigger factors and no sensory findings were found to be statistically significant. Involvement of dual divisions (V2 and V3), absence of trigger factors and evidence of sensory finding were suggestive of Secondary Trigeminal neuralgia.

The greatest limitation of the study was the retrospective design and the conclusions were based on observation from a single study centre. Also, the sample size was relatively low. Thus, a prospective multicentre study is required.

Trigeminal neuralgia though uncommon is a treatable cephalalgia which can have a major impact on the quality of life. The study determined the general clinical characteristics and MRI findings among trigeminal neuralgia patients. The common demographic and clinical features include female pre-ponderance, right side presentation, maxillary nerve division distribution, shock/lancinating pain with touch and breeze as common trigger factors. As some of them had a previous dental treatment or procedure, dentists need to be aware of this entity. Classical trigeminal neuralgia was the most common subtype. Involvement of dual divisions (V2 and V3), absence of trigger factors and evidence of sensory finding were more suggestive of Secondary Trigeminal neuralgia.