Effect of Single dose of Methylprednisolone Injection at Stylomandibular Ligament Insertion on Pain and Various Mandibular Movements Among Patients with Ernest Syndrome: A Pilot Study

Abstract

Insertion tendinosis of stylomandibular ligament or Ernest syndrome is a rarely encountered cause of orofacial pain. The pain in this disorder originates from the stylomandibular ligament insertion site and radiates to the temporomandibular joint (TMJ), neck, shoulder, and periauricular region. Ten subjects who had undergone surgery for mandible fractures diagnosed with Ernest syndrome were considered for the present study. The origins and insertions of the stylomandibular ligament were marked and palpated using fingertip and blunt probe. The Ernest syndrome was confirmed by injecting diagnostic local anesthesia injection. A single dose of 2 ml methylprednisolone (40 mg/ml) was injected at the insertion site of a stylomandibular ligament in each subject. The effect of methylprednisolone injection on pain and various jaw movements were assessed at 1-month and 6-months after the injection. The mean pain value ranks during rest & while mouth opening in the visual analogue scale (VAS) reduced significantly after single injection (P < 0.001). The mean mouth opening increased significantly from 23.3 ± 3.94 mm before the treatment to 36.1 ± 3.07 mm at 1-week and 35.4 ± 2.17 mm at 6-months after the treatment (P < 0.001). The mandible protrusive movement increased from 4.07 ± 0.74 mm before treatment to 5.06 ± 0.62 mm at 1-week and 4.94 ± 0.62 mm at 6-months after the injection, respectively. Single dose of methylprednisolone injection at the insertion site of the stylomandibular ligament was proved effective on pain and various mandibular movements among patients with Ernest syndrome.

Introduction

Insertion tendinosis of stylomandibular ligament or Ernest syndrome is a rarely encountered cause of orofacial pain. The pain in this disorder originates from the stylomandibular ligament insertion site and radiates to the temporomandibular joint (TMJ), neck, shoulder, and periauricular region [1]. Functional impairments of jaw movements and restricted mouth opening are the expected consequences of the syndrome. The pain often overlaps with numerous other orofacial pain like Eagle’s syndrome, hyoid bone syndrome, temporomandibular dysfunction (TMDs), and temporal tendinitis [2, 3]. The etiology of Ernest syndrome is multifactorial. Head injury, maxillofacial trauma, and difficult intubation are common causes. Extreme stretching of the ligament during external trauma or excessive mouth opening could also lead to Ernest syndrome. It could also be one of the post-traumatic complications of the maxillofacial injury. Precise examination and thoughtful understanding of the temporomandibular joint anatomy and its pathophysiology provide a better and safer diagnosis of this syndrome. A few reports in the literature describe the origin of Ernest syndrome following a mandibular fracture [4], but its post-operative presentation after open reduction and internal fixation is infrequent. Insertion Tendinosis of the stylomandibular ligament is a degeneration of the tendon’s collagen in response to chronic overuse; when overuse is continued without giving the tendon time to heal and rest, such as with repetitive strain injury results in tendinosis [5]. A wide variety of treatments are available for the management of Ernest syndrome, which includes local anesthesia injection, soft diet, alternate cold pack, rescue analgesics, steroid injection, ultrasound, cold laser, infrared light therapy, etc. The majority of the patients respond well to the various conservative treatments. However, there is very little information about the effect of steroid injection on pain and mandibular movements. Thus, the present study was conducted to evaluate the impact of a single dose of methylprednisolone injection at stylomandibular ligament insertion on pain and various mandibular movements among ten patients diagnosed with Ernest syndrome following the mandibular fracture.

Patients and Methods

A total of 10 subjects diagnosed with Ernest syndrome between October 2018 and June 2021 were considered for the present pilot study. The study was approved by institutional review board (T/IM-NF/Dentistry/21/43). Of 10 subjects, nine had undergone open reduction and internal fixation for the mandibular fracture. The intervention included the repositioning of the fracture fragment and osteosynthesis under general anesthesia. The intraoral vestibular approach was used to access the mandibular angle, body, and parasymphysis region; whereas, sub-condylar fracture fixation was done via an extraoral retromandibular approach. No surgical intervention was carried out for undisplaced ramus fracture. All the subjects received two weeks of temporary intermaxillary fixation using an arch bar and elastics to guide the occlusion. Post-operative antibiotics and analgesics were prescribed to all the subjects for five days. During the post-operative follow-up period, all the subjects complained of pain around the angle of the mandible, which radiated to the temporomandibular joint (TMJ) region, periauricular, and temporal region. Of 10 subjects, seven subjects had restricted mouth opening with difficulty in various mandibular movements. Post-operative surgical site infection was ruled out based on the characteristics of pain, clinical examination, and radiographic evaluation.

The orthopantomogram (OPG) was advised to assess any associated elongation of the styloid process or stylomandibular ligament calcification. The OPG revealed no evidence of local inflammation, malunion, or degenerative bony changes in any subject. The occlusion was satisfactory in all the patients. Based on the clinical and radiological findings, a provisional diagnosis of Ernest syndrome was made. Then, the origins and insertions of the stylomandibular ligament were marked following palpation of the ligament’s full course using fingertip and blunt probe. There was no trigger zone during the palpation of masticatory muscles; however, tenderness was noted at the stylomandibular ligament insertion site. The injection of local anesthesia (2% lignocaine hydrochloride with 1:80,000 adrenaline) at the stylomandibular ligament insertion site eliminated the pain, and the diagnosis of Ernest syndrome was confirmed. Infiltration with corticosteroids is considered highly successful in treating patients with Ernest syndrome [6].

All the subjects received a single dose of 2ml methylprednisolone injection (40 mg/ml) at the stylomandibular ligament insertion site in the posteromedial surface of the mandible angle (Fig. 1). Subjects were asked to avoid forcing the jaw open and prescribed a soft diet for the 15-days following treatment. All the subjects were followed for a period of 6-months. Written informed consent was obtained from each subject before the injection of methylprednisolone, and the study was conducted as per the principles stated in the Declaration of Helsinki.

Fig. 1.

Methylprednisolone Injection at the insertion of the stylomandibular ligament

The effect of methylprednisolone injection on facial pain was evaluated using the visual analog scale (VAS), having a scale from 0 to 10 (0 = No pain and 10 = Maximum pain) [7]. Various mandibular movements like mouth opening (MO), right lateral (RLM), left lateral (LLM), and protrusive movements (PM) were recorded using a divider and metal scale. A standard proforma was used to record the pain and various mandibular movements. All the subjects were followed at a regular interval of 1-month and the data were collected at 1-week and 6-months following the methylprednisolone injection.

Statistical Analysis

The statistical analysis was carried out using SPSS software (Statistical Packages for the Social Sciences, Chicago, IL, version-16.0). Descriptive statistics were used. The Friedman’s test and Wilcoxon signed-rank test were used to evaluating the VAS Scores, and the Analysis of Variance (ANOVA) with post-hoc (Tukey test) tests used to assess the details of the mandibular movements. The P-value of 0.05 was considered as the level of significance.

Results

The mean age of the subjects was 30.2 ± 7.33 years (range, 30–39 years), and the mean duration of symptoms at the time of diagnosis following their mandibular surgery was 5.9 ± 2.5 months (range, 3–11 months). Of 10 subjects, 7 had fracture mandible following a road traffic accident, 2 had assault, and 1 had fall. Five subjects had angle fracture, three had a sub-condylar fracture, and one each had ramus and body of mandible fractures (Table-1).

Table 1.

Patient Demographic, Etiology, Site of fracture and Associated injury

Age/Sex	Etiology	Duration from the time of injury (Months)	Fracture site (Mandible)	Associated injury
26/M	RTA	4	Angle(Ipsilateral)	Zygomatic complex
32/M	FALL	9	Angle(Contralateral)	Nil
30/M	RTA	7	Body (Ipsilateral)	Parasymphysis
21/M	ASSAULT	5	Angle (Ipsilateral)	Nil
20/F	ASSAULT	6	Sub condylar(Contralateral)	Zygomatic complex
26/M	RTA	3	Sub condylar(Ipsilateral)	Neck of the condyle (Contralateral) and Symphysis
43/F	RTA	6	Angle(Ipsilateral)	Symphysis
31/F	RTA	4	Angle (Ipsilateral)	Lefort 1
39/F	RTA	4	Ramus(Ipsilateral)	Nil
34/M	RTA	11	Sub condylar (Ipsilateral)	Parasymphysis

The mean pain value (VAS) at rest was 6.5 before treatment, and it reduced significantly to 3.4 and 1 at 1-week and 6-months, respectively, following the single dose of methylprednisolone injection (P < 0.001). The mean pain value during mouth opening was 7.9,5.5,1.3 before,1-week, and 6-months after the methylprednisolone injection, respectively, and the difference was statistically significant (P < 0.001). The mean pain value during various lateral excursions was 8.2 before treatment, and it was decreased significantly to 5.6 and 1.5 after 1-week and 6-months of methylprednisolone injection, respectively (P < 0.001) (Table-2), (Fig. 2).

Table 2.

Mean pain value ranks (VAS) during jaw movement at different time interval

Pain (VAS)	Before injection (T0)	Post injection (1-week) (T1)	Post injection (6-months) (T2)	χ2 value	P value	Between the group comparison (P value) T0-T1 T0-T2 T1-T2
Pain at rest	6.5	3.4	1	20	< 0.001	0.005	0.005	0.004
Pain on mouth opening	7.9	5.5	1.3	20	< 0.001	0.005	0.005	0.005
Pain during lateral excursions	8.2	5.6	1.5	19.538	< 0.001	0.007	0.005	0.005

Fig. 2.

Bar diagram showing the mean rank value of pain perception before and after treatment at various time intervals

The details of various mandibular movements at different time intervals of observation are mentioned in table-3. The mean mouth opening increased significantly from 23.33 ± 3.94 mm at T0 to 36.12 ± 3.07 mm at T1 and 35.43 ± 2.17 mm at T2, and the difference among them was statistically significant (P < 0.001). At T0, the mean right lateral excursion was 6.1 ± 0.63 mm, and it increased to 9.73 ± 0.52 mm and 9.38 ± 0.68 mm at 1-week and 6-months following injection of methylprednisolone (P < 0.001). In the left lateral excursion, the mean mandibular movement increased significantly from a T0 value of 5.96 ± 0.65 mm to 8.91 ± 0.98 mm and 8.81 ± 1.04 mm 1-week 6-months after the treatment, respectively (P < 0.001). The mandible protrusive movement increased from 4.07 ± 0.74 mm before treatment to 5.06 ± 0.62 mm at 1-week (P = 0.259) and 4.94 ± 0.62 mm at 6-months (P < 0.05) after the treatment, respectively (Fig. 3).

Table 3.

Mean jaw movement (mm) at different time interval

Parameter	Before injection (T0)	Post injection (1-week) (T1)	Post injection (6-months) (T2)	F value	P value	Between the group comparison (P value) T0-T1 T0-T2 T1-T2
Mouth opening (mm)	23.3 ± 3.94	36.1 ± 3.07	35.4 ± 2.17	52.294	0.000	0.000	0.000	0.002
Right lateral excursion (mm)	6.1 ± 0.63	9.73 ± 0.52	9.38 ± 0.68	106.169	0.000	0.003	0.000	0.000
Left lateral excursion (mm)	5.96 ± 0.66	8.91 ± 0.98	8.81 ± 1.04	33.908	0.000	0.003	0.000	0.005
Protrusion (mm)	4.07 ± 0.74	5.06 ± 0.62	4.94 ± 0.62	6.618	0.005	0.259	0.010	0.273

Fig. 3.

Bar diagram showing the effect of methylprednisolone injection on various jaw movements at a different time interval of observation

Discussion

Insertion tendinitis or Ernest syndrome is an unusual presentation of facial pain. It is often missed or misdiagnosed as Eagle syndrome, which presents a painful alteration of the stylohyoid process in patients. Unlike Ernest syndrome, which only affects the stylomandibular ligament, especially at the mandibular insertion, Eagle syndrome is usually bilateral [2].

The etiopathogenesis of Ernest syndrome is not completely clear; it could be related to trauma caused by blows to the jaw, cranial trauma, or whiplash injury caused by traffic accidents [8, 9]. An excessive stretch of the stylomandibular ligament to more than 25 to 30 mm may cause cervical and pharyngeal pain and pain when swallowing, speaking, and opening the mouth, perception of a foreign body in the oropharynx, and pain radiating to the ear [10, 11]. It has been suggested that prolonged dental procedures may lengthen and strain the stylomandibular ligament, thereby causing painful symptoms [2, 4].

Accurate diagnosis is the key to being able to provide proper treatment and improve quality of life. An article by Edwin A. Ernest described two cases having an ultimate diagnosis of Ernest Syndrome resulting from motor vehicle trauma but was inappropriately operated for TMJ arthroplasty [12]. Ernest syndrome symptoms are usually seen in the preauricular area and mandibular angle. Pain is seen radiating to the neck, shoulder, eye on the same side and on palpation of the stylo-mandibular ligament (gentle pressing) and is usually not self-limiting [4]. Several factors can be associated with post-operative pain in the maxillofacial skeleton, including fracture malunion, associated nerve injury, occlusion derangement, surgical site infection, etc. Inadequate reduction and fixation of fracture fragment result in delayed union, nonunion, and malunion. The incidence of traumatic cranial nerve injury is approximately 5 to 23% of individuals. Injury to peripheral branches of trigeminal nerves can cause significant neurosensory deficits and facial pain. Complete clinical and post-operative radiographic evaluation was done for all the patients included in the present study. The course of the stylomandibular ligament was palpated following the marking using fingertip and blunt probe. Upon administering local anesthesia using 2% lignocaine with 1:80,000 adrenalines at the stylomandibular ligament insertion, the pain was relieved, and the diagnosis of Ernest syndrome was confirmed.

The degree of chronic pain is strongly associated with a worse perception of the quality of life [13]. The therapeutic goal is to alleviate the disease progression, thus to reduce pain, improve mandibular function, and quality of life. There are many nonsurgical or surgical approaches to treat Ernest syndrome. Although various conservative therapies are recommended in the literature, no established guidelines are available to manage Ernest syndrome. Multiple studies show the effectiveness of steroids in insertion tendinitis by minimizing the inflammatory response [12, 14]. According to Shankland et al., among 68 patients with Ernest syndrome, 77.94% were treated successfully via nonsurgical management with the injection of local anesthetic blocking of the insertion of the affected stylomandibular ligament(s), localized injection of 1ml of betamethasone sodium phosphate, and placing the patient on a soft diet [2]. A retrospective observational study by Peñarrocha-Oltra D et al. showed that the injection of 40 mg triamcinolone acetonide at the mandibular insertion of the stylomandibular ligament in 6 patients was adequate for the elimination of pain for 12 months. However, in our study, one dose of methylprednisolone was effective in the complete elimination of pain for a minimum period of 6-months. All the patients achieved complete symptom remission with the treatment.

If necessary, surgical management is performed by using a technique called radiofrequency thermoneurolysis [1, 15]. This procedure involved placing a radiofrequency needle into the insertion of the stylomandibular ligament and creating an elliptical lesion, which apparently deinnervates the pain fibers of the injured insertion of the ligament.

In the present study, most of the patients reported pain and restricted jaw movements, which were subsequently improved after a single steroid dose. Pain with or without jaw movements subsided significantly after 1-week and 6-months, respectively. This suggested that pain associated with the disorder might play a significant role during the functional movement of the jaw.

Though it was an established fact that maxillofacial trauma can lead to injury to the associated ligament structures, identifying its origin was tricky. The practitioner should have full knowledge of the local anatomy, and extra precautions should be taken before injection. The injection should be peritendinous, and injection into the tendon substance must be avoided. To avoid iatrogenic injury to the ligament proper, the needle should be placed in the near approximation of the bony surface of the mandible during the injection.

The present study involved only ten subjects with Ernest syndrome and were followed for a period of 6-months. Although the current study results were promising, further studies considering more subjects are necessary to confirm the fact. The subjects can also be followed for a longer duration to evaluate the efficacy of a single dose of methylprednisolone in the treatment of Ernest syndrome.

Conclusion

However, it is established that injury to the associated ligament structures can develop after a maxillofacial injury; clinicians should differentiate the presence of Ernest syndrome from other causes of orofacial pain. A single dose of methylprednisolone proved effective in reducing pain and improving restricted jaw movements in the treatment of Ernest syndrome.

Declarations

Conflict of Interest

All the author has declared no conflict of interest.

Ethical Approval

All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.

Informed Consent

Informed consent was obtained from all individual participants included in the study.