44.1 Introduction

The oral cavity serves as an important conduit for important functions such as speech and oral intake. Cancers arising in the oral cavity are typically initially managed with surgical resection leading to alteration of structure and function. In this chapter, we will review functional changes to speech and swallowing associated with treatment for oral cavity cancer, how to best evaluate the functional impact of oncologic treatments, and rehabilitative treatments that may be employed to manage them.

44.2 Epidemiology of Dysphagia in Oral Cavity Cancer

Description of the epidemiology of dysphagia in patients following treatment for oral cavity cancer is challenging due to the heterogeneous nature of this population. Surgical resection may be simple or complex and may include primary closure, locoregional or flap reconstruction. Further, some patients will require adjuvant treatment following surgical resection. Hence, there is great variability of functional outcomes in this population. A systematic review completed by Kao et al (2016) ¹ provides some composite information regarding patients treated surgically for oral cavity and oropharyngeal cancers. Their report cites a posttreatment aspiration prevalence of 15.22%, gastrostomy tube (G-tube) dependence rate of 8%, and tracheostomy dependency in less than 1% of patients treated for oral and oropharyngeal squamous cell cancers. Patients requiring postoperative radiation/chemoradiation were at elevated risk for posttreatment dysphagia. In addition, radiation toxicities such as fibrosis, edema, trismus, and xerostomia further impacted patients’ perceived swallowing quality of life. In general, higher tumor stages are associated with poorer functional outcomes. ² While these trends provide an important starting point in the understanding of dysphagia following oral cavity cancer treatment, consideration of particular regions of resection may help provide more insight and expectations of posttreatment function.

44.3 Clinical Presentation

Functional ramifications of oral cavity cancer treatment can be divided into three categories: anatomic, physiologic, and a combination of the two. Changes in the oral cavity, as a result of surgical and adjuvant treatment, will potentially impact the muscles and nerves as well as the vascular and lymphatic systems. Anatomic changes are more commonly associated with surgical resection while physiologic changes are commonly associated with nonoperative treatment modalities; however in the era of combined modality treatment, most patients will experience both anatomic and physiologic changes that may influence speech and swallowing outcomes. It is important to consider each of these types of changes as each may require different interventions. While many patients may present with intelligible speech after oral cavity resection, it is important to acknowledge that atypical speech characteristics may persist, which may draw attention to the speaker and influence communication in a variety of settings. ³

Specific functional deficits are strongly correlated with tumor site and extent of the surgical procedure. In addition, regions of the oral cavity resected may provide some prediction of functional outcomes. Schache and colleagues described the “oral subsites concept” in their 2009 publication. ⁴ They divided oral cavity defects as lateral, central, anterior, and oropharyngeal, and concluded that resections leading to central defects were more likely to yield poor functional outcomes. Each specific anatomic structure and region will be considered individually throughout this chapter, though in reality, surgical resections are commonly more complex and involve more than one structure.

44.4 Glossectomies

When considering the impact of glossectomy on speech and swallowing, it is important to consider not only the extent (partial [ < 50%], hemi [50%], subtotal [ > 50% but < 90%], or total [ > 90%] of oral and tongue base), but also the region of the tongue resected. The major functional regions of the tongue include the tongue tip, tongue body, and tongue base.

The tongue serves as the primary articulator of both vowel and consonants. Resections of different regions of the tongue will lead to variable alteration in sound production. ⁵ From a speech perspective, surgeries involving the tongue tip are likely to impact articulatory precision and speech clarity. Sounds frequently impacted by tongue tip resection include t, d, n, l, r, s, z, and “th.” Resection of the lateral tongue will frequently impact intelligibility to a lesser degree; however, particular sounds such as s, z, and “sh” tend to be problematic for patients. If surgery extends to the tongue base, issues with production of velar plosives (k, g) may be observed. In considering relative intelligibility by extent of resection, Fletcher reported near 100% of word/syllable intelligibility in a patient with 10% tongue volume reduction, 30 to 50% intelligibility in an individual with ~40% tongue resection, and 15 to 40% intelligibility for an individual with ~75% tongue resection. ⁶

From a swallowing perspective, different regions of resection may be associated with predicted swallowing difficulties as well. Surgeries involving the tongue tip are likely to result in oral stage difficulties with bolus containment, mastication, and oral clearance while surgeries including the body of the tongue will result in issues with bolus containment and posterior propulsion. Resection of the lateral tongue is likely to result in difficulty with bolus lateralization for mastication as well as clearance of the oral cavity on the resected side. Aspiration is a common finding following subtotal and total glossectomy due to reduced bolus clearance and reduced hyolaryngeal excursion due to removal of the suprahyoid muscles. ⁷ Aspiration rates have been reported as high as 40% one year following surgical resection including the oral tongue. ² Gastrostomy dependency at 12 months post total glossectomy with free flap reconstruction is estimated at 24% based on a systematic review of the literature. ⁸

In addition to considering the extent of resection, we also must consider the surgical approach and type of reconstruction after completion of the ablative procedure. Patients requiring mandibulotomy have higher risk of functional deficits than patients whose tumors can be approached transorally. ⁹ The primary functional purpose of reconstruction following glossectomy is to provide bulk within the oral cavity to assist with speech and swallowing function. Contact between the palate and the remnant tongue/reconstruction provides benefit in regards to both speech and swallowing. ¹⁰ If the degree of resection is limited, the surgical field is typically closed through primary closure. Research has demonstrated functional superiority of primary closure compared to tissue transfer when the extent of surgical resection is limited to less than 25% of the tongue. ¹¹ More extensive excisions may require reconstruction using skin grafts or tissue transfer. Skin flaps involve transportation of skin and underlying subcutaneous tissue from one region to another while maintaining a pedicle to the original site. Myocutaneous flaps also include underlying muscle and are used for more extensive reconstructions. Examples of myocutaneous flaps include the pectoralis major flap and the platysma flap. Microvascular advances permit the transfer of muscle and tissue from a remote area of the body to the surgical site by ability anastomosis of distant and regional blood supplies to maintain the viability of the tissue. A primary advantage of this type of flap is the ability to be more selective about the amount of tissue harvested/transplanted. This prevents both inadequate and excessive bulk, both of which may negatively impact speech and swallowing outcomes. In addition, anastomosis of nerves in the graft to regional nerves may allow for sensory innervation of flaps. There is evidence that patients undergoing hemi- and subtotal glossectomy have more favorable swallowing outcomes if they receive innervated flaps. ¹² These “free flaps” are commonly utilized for reconstruction of larger tongue resections. Examples of free flaps include the radial forearm free flap and the anterolateral thigh flap. There is no clear evidence of superiority of the different types of free flaps on swallow or speech function.

44.5 Diagnosis and Evaluation of Speech and Dysphagia in Patients with Oral Cavity Cancer

Assessment of speech after oral cavity resection may include measures of articulator mobility and strength, specific sound generation, communicative intelligibility, and patient perceived communication function. While there are no “gold standard” tests to assess speech outcomes, many clinical tools have been validated for use in this population. Lazarus and colleagues ¹⁴ described a range of motion measurement scale to be used to quantify restriction in tongue mobility as a way to predict function. This tool has been shown to correlate with speech and swallowing outcomes, performance status, and patient-rated quality of life. Maintenance of tongue strength has also been associated with more favorable patient reported outcomes with 30 kPa reflecting a predictive cutoff for anticipating outcomes. ¹⁵ Precision of consonant and vowel production can be estimated by a skilled speech language pathologist (SLP) both in isolation and in variable phonetic contexts. Similarly, intelligibility can be rated at the single word, passage, and conversation level using tests such as the Speech Intelligibility Test, ¹⁶ the Assessment of Intelligibility of Dysarthric Speech, ¹⁷ and the Frenchay Dysarthria Assessment. ¹⁸ Patient-reported quality of life measures that may be used to quantify speech-related disability include the Speech Handicap Index ¹⁹ and the speech domains of the Performance Status Scale, Head and Neck. ²⁰

The measurement of dysphagia is a multidimensional construct and there is limited consensus in the literature about the most appropriate measures to quantify and describe dysphagia in the head and neck population. Diagnosis of dysphagia in head and neck cancer patients should consider anatomic and physiologic changes as measured during instrumental swallowing assessments, impact on oral diet, tube feeding reliance, and patient-perceived swallowing function/quality of life. This global assessment will provide the most comprehensive picture of how the patient is experiencing swallowing.

Due to the elevated risk of silent dysphagia in head and neck cancer, instrumental assessment is essential following oral cavity resection, particularly for those individuals who are at highest risk for dysfunction. ²¹ A recent investigation of the ability of clinical evaluations to predict aspiration following head and neck cancer surgery demonstrated poor predictive value of clinical findings such as tongue weakness, tongue immobility, and wet voice. ²² These findings suggest the importance of instrumental assessment for detection of dysphagia and aspiration following surgical resection. Untreated dysphagia may lead to adverse outcomes such as aspiration pneumonia, dehydration, and malnutrition. Such events may compromise healing following surgical procedures, oncologic outcomes due to treatment breaks, and may place the patient at elevated risk for long-term health consequences including death. Determining aspiration risk following treatment may assist in ensuring optimal intervention by the SLP through application of compensatory maneuvers, dietary modifications, and rehabilitative interventions.

Instrumental swallowing evaluation can be accomplished through videofluoroscopic swallowing studies (VFSS) or fiberoptic endoscopic evaluation of swallowing (FEES). These tools are complimentary and both play a valuable role in the assessment of dysphagia in patients with head and neck cancer. VFSS is generally considered the gold standard for assessment of oropharyngeal disorders due to its ability to provide visualization of the coordinated stages of swallowing as well as specific physiology (Video 44.1). In addition, use of VFSS allows for evaluation of the oral and esophageal aspects of swallowing which are not visualized on endoscopic examination. In contrast, FEES provides the benefits of avoiding radiation exposure, a flexible service delivery model, and direct visualization of relevant anatomy (Video 44.2). Investigation of the comparability of these tools has revealed high levels of agreement, sensitivity, specificity, and positive and negative predictive values. ²³ A thorough FEES evaluation conducted by an experienced SLP can provide anatomic and physiologic information, assessment of swallowing safety/efficiency across viscosities and textures, and implementation of compensatory postures and strategies when dysfunction is identified. It can be implemented in the early recovery period to establish safety to initiate first oral intake. Despite the fact that both tools have high levels of utility, in the oral cancer population, VFSS is typically the preferred method for assessing swallow function as it allows for full visualization of the oral cavity and the transition between the oral and pharyngeal phases of swallowing. Based upon a systematic review of the literature, Mylnarek and colleagues ²⁴ proposed that instrumental swallowing evaluation, assessment of speech intelligibility, supplemental speech evaluation when indicated, and patient reported swallowing outcomes should be measured prior to, during, and following treatment for oral and oropharyngeal cancers.