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920 - Biting Back at Pain: Incobotulinumtoxin-A Injections for the Management of First Bite Syndrome

Thursday, February 27, 2025

5:00 PM - 6:30 PM MST

Presenting Author(s)

AB

Abigail E. Brown, MS

OMS-IV
WVSOM
LEWISBURG, West Virginia, United States

Co-Author(s)

CP

Cynthia Pham, MD

Resident Physician
Atrium Health Carolinas Rehabilitation
fort mill, South Carolina, United States
CM

Charles Mitchell, DO

Assistant Professor
Carolinas Rehabilitation
Charlotte, North Carolina, United States

Case Diagnosis: First Bite Syndrome (FBS)

Case Description: A 56-year-old male with a history of oral hemangioma underwent lip-split mandibulotomy for tumor resection. Postoperatively, he developed severe unilateral preauricular pain with the first bite of solid food that improved with subsequent bites, leading to a diagnosis of FBS. Gabapentin, oxycodone, and NSAIDs provided no relief. Fifty units of incobotulinumtoxin-A were injected into the left parotid gland in two locations under ultrasound guidance. At six weeks, he reported mild pain with greater than 50% reduction in pain severity. Four months post-procedure, he underwent repeat biopsy of a posterior pharyngeal mass causing return of the initial pain. At this time, a second round of incobotulinumtoxin-A was injected yielding 100% pain relief with small bites; however, he was referred to physical therapy for mild pain with large bites to evaluate a potential multifactorial explanation for the residual symptoms.

Discussions: FBS is characterized by severe orofacial pain with salivation upon initial bites of food. This can cause food aversion and weight loss. Risk factors include parapharyngeal space surgery, sympathetic chain sacrifice, and parotid resection. Symptoms are potentially caused by sympathetic denervation of the parotid and subsequent hypersensitivity to parasympathetic stimulation resulting in painful myoepithelial contraction during secretion of salivary fluid. Currently no standard treatment for FBS exists; however, attempted methods include dietary modification, analgesics, neuropathic agents, anticonvulsants, antidepressants, acupuncture, and neurectomy.

Conclusions: FBS is a postsurgical complication that can significantly decrease quality of life. Its unique pathophysiology leads to challenges in diagnosis and treatment. There is a lack of controlled studies and established protocol guidelines for the use of botulinum-toxin injections in the management of FBS. This case of FBS refractory to oral medication, provides evidence of successful management with incobotulinumtoxin-A injections, highlighting the efficacy of this treatment and the role of the rehabilitation physician in addressing this rare syndrome.