20.1 Introduction

The use of botulinum neurotoxin (BoNT) for head and neck disorders can also be extended to the sequelae resulting from the treatment for head and neck cancer (HNC). These complications include chronic and neuropathic pain following neck dissection, muscle spasms after radiation therapy, and radiation-induced trismus and fibrosis. ¹ In fact, pain affects 45% of patients in the years following treatment, with a quarter of those patients describing severe pain. ² With long-term survival becoming more common, the pain impacts quality of life (QOL) and can result in major depression, anxiety, and reduced recreation. ^{2 ,​ 3} This is concerning because this may lead to the use of opioid-containing medications that may place one at the risk of misuse. Patients with a HNC diagnosis are more likely to be prescribed opioids, as opposed to those with other cancer diagnoses such as lung cancer and colon cancer. ⁴ While the analgesic effects of BoNT are still unclear, there is evidence to suggest that its use can play an important role in helping to mitigate the physical sequelae following treatment for HNC. ^{1 ,​ 5 ,​ 6 ,​ 7 ,​ 8} Furthermore, the use of BoNT as an adjunctive treatment was recently recommended in the Head and Neck Cancer Survivorship Guidelines for both cervical dystonia (CD) and the pain associated with trismus. ³

Radiation fibrosis syndrome (RFS) is a term that has been used to describe the complications following radiation therapy and defines complications into two general categories, including muscle spasm and neuropathic pain. Muscle spasm incorporates CD and trismus, while neuropathic pain incorporates trigeminal neuralgia, cervical plexus neuralgia, and migraine. ¹ Using RFS as a framework, this chapter will discuss each of the following conditions in turn, referencing back to previous chapters, as well as highlighting the important issues as they relate to the HNC patient ¹ :

• 
  

  Muscle spasm:

  
  
  
  
  • 
    

    Cervical dystonia.

    
    
  • 
    

    Trismus.

  
  
• 
  

  Neuropathic pain:

  
  
  
  
  • 
    

    Trigeminal neuralgia.

    
    
  • 
    

    Cervical plexus neuralgia.

    
    
  • 
    

    Migraine.

20.2 Workup

The patient should have a complete history and examination performed by their treating physician/surgeon in order to rule out the possibility that their symptoms could be attributed to a recurrent or new malignancy. If there is a suspicion, then an appropriate evaluation including imaging of the area should be undertaken. If there is no recurrent or new malignancy and the patient has failed treatment with standard conservative and medical management, then they can be considered a candidate for BoNT injection into the affected areas. Conservative management may include physical therapy for myofascial release, range of movement training, and lymphedema management. Medical management may include the use of analgesics such as acetaminophen, ibuprofen, opioids, topical lidocaine, as well as nerve stabilizing agents such as gabapentin and amitriptyline. How many medical treatments the patient must fail prior to starting treatment with BoNT is unknown, but one study does suggest a failure of at least two. ⁵ Important metrics to consider pre- and postinjection include a visual analog scale (VAS) for pain and the QOL scale that is most pertinent to the patient.