First bite syndrome: What every general dental practitioner should know

12 February, 2019 / clinical
 Donal P. McAuley, Robert S. D. Smyth, Martin D. Paley  

Donal P. McAuley1, Robert S. D. Smyth2, Martin D. Paley3

1MB BCh, BDS, MRCSEd, MFDS RCSEd, Specialist Registrar in Oral and Maxillofacial Surgery, St. John’s Hospital, Livingston

2BDS, MFDS RCPSG, MFDS RCSEd, Core Trainee in Oral and Maxillofacial Surgery, St. John’s Hospital, Livingston

3MB ChB, BDS, FFD RCSI, FRCSEd (OMFS), Consultant in Oral and Maxillofacial Surgery, St. John’s Hospital, Livingston


Abstract

First bite syndrome is an uncommon complication following surgery involving the infratemporal fossa and the parapharyngeal space or deep lobe of parotid. We report a case of first bite syndrome that was referred to our unit in an effort to make GDPs aware of the presentation of and to highlight the management of this potentially debilitating chronic pain syndrome.

CPD/Clinical relevance: This paper describes how first bite syndrome may present as a complication following surgery; general dental practitioners should be aware that it may represent the initial presentation of an underlying neoplastic process of the parotid gland or parapharyngeal space.

Objective: The reader should understand the presentation and management of first bite syndrome. The role of a GDP is important in management and potential diagnosis.


Concise precis

General dental practitioners (GDPs) should be aware of the typical clinical presentation of first bite syndrome and refer appropriately to oral and maxillofacial surgery.

Introduction

First bite syndrome is an uncommon complication following surgery involving the infratemporal fossa and the parapharyngeal space or deep lobe of parotid 1. Patients typically experience pain in the parotid region on the same side as the surgery at the first bite of each meal. It characteristically lasts for a few seconds and gradually improves with subsequent mastication, but returns at the first bite of the next meal 2.Symptoms range from mild to severe, and can significantly affect the patient’s quality of life 3.

The actual cause of first bite syndrome is unknown. Most cases occur as a postoperative complication, but it has also been reported preoperatively 3,4,5, and even spontaneously, without any obvious cause 6. Most theories on the pathology of first bite syndrome are based on the concept of sympathetic denervation of the parotid gland either through cervical sympathectomy or ligation of vascular structures alongside which sympathetic nerves travel 3. This results in subsequent hypersensitivity of myoepithelial cells to parasympathetic neurotransmitters and elicits a supramaximal contraction of myoepithelial cells during the first bite of a meal and subsequently subsides with continued mastication 7. We report a case of first bite syndrome which was referred to our unit in an effort to make GDPs aware of the presentation of and to highlight the management of this potentially debilitating chronic pain syndrome.

Figure 1: Surgical scar left side of neck from previous neck surgery

Case Report

A 50-year-old female initially presented to the ear, nose and throat team with a left-sided level II neck mass, which had slowly increased in size over a six-year period. Medically she was fit and well, and a non-smoker. Three years previously she had undergone a mandibular advancement osteotomy with insertion of a chin prosthesis for a high angle Class II Div I malocclusion and had made an uneventful post-operative recovery.

Magnetic resonance imaging (MRI) and ultrasound guided fine needle aspiration cytology were suggestive of a benign neuroma most probably arising from the vagus nerve. She proceeded to have surgical excision of the lesion, which was histologically confirmed as a Schwannoma, most likely arising from the ansa cervicalis. At a subsequent review appointment two months after her surgery she complained of pain over the left side of her face around her temporomandibular joint (TMJ) and she was noted to have mild Horner’s syndrome on the left side.

The patient was referred to oral and maxillofacial surgery querying TMJ dysfunction. She complained of severe shooting pains over the left side of her upper neck, angle of her jaw and around her TMJ on the left. Pain was reportedly worse on biting and eating, especially with the first bite of a meal. She did not complain of any background pain and felt she could relate the onset to her previous neck surgery.

Clinical examination revealed a scar over the left side of her neck in keeping with her previous neck surgery (Figure 1). She was tender over the left TMJ to palpation, it had a full range of movement which was pain free. There was also some tenderness noted over the muscles of mastication on the left side. Intra oral examination revealed no obvious source for her symptoms and although she had amalgam restorations in her upper and lower molars on the left (Figure 2) none of her teeth were tender to percuss or elicited an abnormal response to sensitivity testing. Orthopantomogram revealed thin condyles only with no obvious dentoalveolar pathology. A computed tomography scan showed mild thinning of the condyles with no evidence of pathological deterioration. A diagnosis of TMJ dysfunction was made and it was felt this may have been a complication of her previous mandibular advancement surgery three years previously. Initial management was conservative with advice on analgesia, soft diet, warm compress and myotherapy of the muscles of mastication.

At subsequent review appointments the patient reported a mild improvement in symptoms while following conservative measures. However, the history became clearer that the sharp pain she was having had occurred with the first bite of each meal and eased with subsequent bites. In addition the pain was worst with the first meal of the day. She also reported no background pain. A clinical diagnosis of first bite syndrome was made and was supported by the established association between this condition and Horner’s syndrome. It was felt that this was most likely a complication of her previous neck surgery for her schwannoma. An MRI was performed to exclude any other lesions which may give rise to first bite syndrome. She was initially treated with non-steroidal anti-inflammatory drugs (NSAIDS) and gabapentin. However, this failed to control her symptoms. Following a review of the literature she was commenced on carbamazepine and the dose titrated to effect 7. She was able to tolerate a dose of 400mg daily but was concerned that any higher dosage would make her feel overly drowsy. Her symptoms were less severe and better controlled on carbamazepine, the pain on first bite was not as extreme and settled much quicker with subsequent mastication. We discussed the injection of botulinum toxin into the left parotid gland as a treatment option8,9,10, but she declined this. The patient remains under outpatient follow-up, and feels that her symptoms are tolerable at present.

Figure 2: OPT showing heavily restored posterior molars bilaterally but no dentoalveolar cause for her symptoms.

Discussion

Surgery which involves extensive dissection in the parapharyngeal space is associated with multiple complications due to the complex neurovascular anatomy within this region 10. Complications such as vocal cord palsy, palatal weakness, and Horner’s syndrome may be expected due to essential sacrifice of nerves involved in the pathology. A less predictable complication of these surgeries is first bite syndrome. The proposed pathophysiology behind this was originally described by Netterville et al 11 in 1998. It is believed that sympathetic innervation to the parotid gland is either damaged or lost in the extended dissection of the external carotid artery where these fibres run. Loss of sympathetic input leads to hypersensitivity of sympathetic receptors on the myoepithelial cells of the parotid gland. Cross-stimulation of these receptors by parasympathetic release of acetylcholine is believed to cause a hyperintense contraction of these myoepithelial cells which results in the pain described by patients in the first few bites of their meals 10. This is the rationale for the treatment with intraparotid injections with botulinum toxin as it blocks acetylcholine, and this blockade of neurotransmitters decreases the intense myoepithelial contractions derived from the cross-stimulation of sympathetic receptors, in doing so relieving the pain experienced on initiation of mastication 9.

Most reported cases of first bite syndrome have been documented after surgery; however, in the absence of ipsilateral upper neck surgery it may be the first presenting symptom of a malignancy of the deep lobe of parotid, submandibular gland or ipsilateral parapharyngeal space 3,4,5,12. It has also been reported as idiopathic first bite syndrome in patients without a history of surgery or without any evidence of neoplasia 6, 13. General dental practitioners should be familiar with this chronic pain syndrome as patients may present to them in the first instance relating their pain to biting and attributing it to an underlying dental pathology.

The diagnosis can be made by taking a good history and by thorough clinical examination. It presents clinically as an intense, paroxysmal, electric shock, cramping or spastic pain arising in the region of the parotid gland or TMJ which rapidly spreads along the mandible 14. It is triggered by chewing, swallowing or even by simple contact with food, the trigger varies, it may be solid or liquid foods but is always acidic. The symptoms may be reproduced by stimulating salivary flow via intraoral lemon glycerin swabs 13. This pain only lasts for several seconds and tends to wane with subsequent swallows, but it recurs after pausing for several minutes or at the following meal. It is also reported to be most severe with the first meal of the day. Some patients find that manual compression of the painful region helps to relieve pain, leading them to press over the painful region preventively before taking the first bite 14. The onset of the pain may be preceded by ipsilateral upper neck surgery, parotid surgery or orthognathic surgery.

Careful extra oral examination may reveal a surgical scar in keeping with previous cervical neck (Figure 1) or parotid surgery. Deep palpation should be systematic and thorough to exclude any new neoplasia or neck mass presenting as first bite syndrome. Examination of the TMJ should be performed and would be expected to be unremarkable. Another extra oral sign that may arouse suspicion is evidence of Horner’s syndrome, pupil constriction (miosis), ptosis and ipsilateral loss of sweating (anhydrosis). This may be a post-surgical complication also, or arise suspicion of a new lesion of the superior cervical ganglion or sympathetic branches travelling along the internal carotid artery. As with any dental patient careful intra oral examination should be performed to exclude any dentoalveolar cause for the patient’s symptoms. The occlusion should be assessed carefully, especially if any recent restorative work has been carried out, heavily restored teeth should have percussion testing and sensitivity testing performed and where appropriate radiographs taken.

In the absence of any clear dental pathology, and with a history that arouses suspicion of first bite syndrome, any dental treatment should be avoided, and the patient should be referred onwards to the closest maxillofacial surgical unit or ear, nose and throat department for further investigation and to initiate treatment. The dentist should be sympathetic and recognise that this chronic pain syndrome can have a considerable impact on the patient’s quality of life. The patient may become anxious even at the idea of having a meal and may modify his or her eating behaviour.

Multiple treatments have been attempted to control the pain of first bite syndrome, but few have been successful in completely resolving it. Treatments can be divided into four main categories: dietary modification, pharmacological treatment, radiation therapy and surgical treatment. Dietary modification has been found to be completely ineffective 10,11. First-line treatment often consists of NSAIDs used as analgesics in combination with anticonvulsants such as carbamazepine or calcium channel blockers, such as gabapentinoids, or tricyclic antidepressants with anticholinergic effects, such as amitriptyline 14. Although some pharmacological options have been reportedly effective, most notably carbamazepine and pregabalin 10, it appears that responses to all these medications varies between individuals 15. Radiation therapy has been proposed as a viable treatment for first bite syndrome in relation to oncology patients 16. The side-effects of radiotherapy, however, are numerous and the morbidity associated with it means it cannot be justified for the treatment of first bite syndrome alone when safer modalities exist.

Permanent solutions to first bite syndrome have been sought by surgical means, but these also come with a risk of morbidity. Total parotidectomy appears to be the most effective surgical intervention. However, it is also the most radical and is most notably associated with the risk of injury to the facial nerve. It has been associated with complete resolution in several cases 3,4,5. Less radical surgical interventions such as tympanic neurectomy have been reported as unsuccessful 18. Amin et al 2014 describe treating a case of first bite syndrome refractory to non surgical management with laser tympanic plexus ablation, they achieved resolution of her symptoms at three-week and two-month follow-up. Netterville et al 1998 reported auriculotemporal nerve resection to be effective initially but the long-term efficacy is unknown.

More recently many authors appear to favour the use of botulinum toxin injections into the parotid gland and have argued pharmacological measures should be skipped in favour of this as first-line treatment 10. Lee et al 2009 noted significant improvement but not total relief of symptoms using
33 units of botulinum toxin injected into the ipsilateral parotid gland. Ali et al 2008 and Sims and Suen 2013 reported complete resolution in three out of four patients treated with injection of 75 units of botulinum toxin into the ipsilateral parotid gland. The other patient had almost complete relief of symptoms with significant improvement in quality of life. The symptoms were found to begin to return gradually within three to five months and patients did not seek further injection until five to eight months
10. There were no side-effects of the injection treatment reported.

Conclusion

First bite syndrome may present as a complication following surgery to the parapharyngeal space or deep lobe of parotid. However, GDPs should be aware that it may represent the initial presentation of an underlying neoplastic process of the parotid gland or parapharyngeal space. It has also been reported as idiopathic without any cause found. Patients may attend their GDP in the first instance as they attribute the symptoms to underlying dental pathology. A thorough clinical history and examination is diagnostic and suspected cases should be referred appropriately. Treatment options have a variable effect and often only work in the short term. Further investigations into the pathophysiology of this chronic pain syndrome and pharmacological treatment for first bite syndrome are essential in order to improve understanding and manage this condition more effectively.


references

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2. Wong EHC, Farrier JN, Cooper DG. First-Bite Syndrome Complicating Carotid Endarterectomy: A case Report and Literature Review. Vascular and Endovascular Surgery 2011; 45: 459-461.

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4. Diercks GR, Roscow DE, Prasad M, Kuhel WI. A case of preoperative “first-bite syndrome” associated with mucoepidermoid carcinoma of the parotid gland. Laryngoscope 2011; 121: 760-762.

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6. Chang SH, Jun BS, Choi JO, Kim JJ, Jang Y. Successful Treatment of a Case of First Bite Syndrome without Any Cause. World Journal of Neuroscience 2015; 5: 331-333.

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13. Stoopler ET, Elmuradi S. Idiopathic First Bite Syndrome. Journal of Oral and Maxillofacial Surgery 2016; 74: 872-874.

14. Abdeldaoui A, Oker N, Duet M, Cunin G, Tran Ba Huy P. First Bite Syndrome: A little known complication of upper cervical surgery. European Annals of Otorhinolaryngology, Head and Neck diseases 2013; 130:123-129.

15. Amin N, Pelser A, Weighill J. First bite syndrome: our experience of laser tympanic plexus ablation. The Journal of Laryngology & Otology 2014; 128, 166-168.

16. Costa TP, de Araujo CE, Filipe J, Pereira AM. First-bite syndrome in oncologic patients. European Archieves of Oto-Rhino-Laryngology and Head & Neck 2011; 268:1241-1244.

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18. Chiu AG, Cohen JI, Burningham AR, Andersen PE, Davidson BJ. First bite syndrome: a complication of surgery involving the parapharyngeal space. Head & Neck 2002; 24:996-999.

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