Subtotal glossectomy preserving half the tongue base prevents taste disorder in patients with tongue cancer

Abstract

Most patients diagnosed with tongue carcinoma undergo surgical resection and reconstructive surgery to preserve tongue mobility and swallowing functions. Twenty-four patients who underwent a total or subtotal glossectomy and surgical reconstruction were evaluated for residual taste sensation. The graded filter paper test for all four tastes (sweet, salt, sour, and bitter) was performed on the posterior wall of the oropharynx and on tongue remnants if they were visible from the mouth. Eleven of the 24 patients were aware of their taste disorder after surgery. Four patients with more than 1/2 residual tongue base had no taste complaints, whereas seven of 14 patients with less than 1/3 residual tongue base reported taste abnormalities. Patients who could only tolerate a poor diet or tube feeding tended to have taste complaints ( P = 0.017). The taste test showed that the taste threshold of the residual tongue was significantly lower compared to controls. The taste threshold was significantly correlated with the remaining volume of tongue base. Patients with >1/2 the tongue base remaining had good taste sensation, whereas those with <1/3 residual tissue had impaired taste. This study suggests that glossectomy strategies aimed at preserving at least half the tongue base may substantially reduce dysgeusia in the patients.

Tongue cancer is currently the most common malignancy of the oral cavity, accounting for 25–40% of all cases of oral squamous cell carcinoma. Although head and neck squamous cell carcinoma (HNSCC) is generally diagnosed around the age of 60 years, the incidence of highly malignant tongue carcinoma in young adults (aged <40 years) is increasing rapidly. Recent advances in multimodal treatments have been unsuccessful in improving the prognosis of these patients, because this highly vascularized organ, which is rich in lymphatic networks, is predisposed to malignancy. Large cohort studies estimate an overall 5-year survival rate of 42–65% for patients with tongue cancer, depending on the stage. Therefore, the most successful treatment remains extensive glossectomy and bilateral lymphadenectomy to remove lymph node metastases undetected by modern imaging techniques.

Since the tongue is essential for food bolus formation and deglutition, most cancer patients undergo reconstructive surgery to restore tongue mobility and swallowing function. Treatments such as glossectomy, chemotherapy, and radiotherapy, as well as flavour disorders and secondary zinc deficiency due to eating disorders, can cause taste disorders in patients with tongue carcinoma. Many studies have reported taste disorders due to chemotherapy and radiotherapy. Altered taste has been found to occur consistently within 3–5 days after starting chemotherapy. Taste sensation generally returns within 3 weeks, although there have been reports of persistence of symptoms for more than 6 months. In contrast, altered taste has been reported to be measurably impaired by the fifth week after radiation therapy. Some previous studies have shown complete recovery of taste function in patients at 1–3 months after treatment, but other studies have not substantiated this observation.

Only a few studies have evaluated the impact of glossectomy on taste. Taste buds exist not only in the tongue but also in the epiglottis, pharynx, larynx, soft palate, and uvula. Patients are therefore not expected to lose their sense of taste after glossectomy. Two reports have evaluated test sensation after subtotal glossectomy. Urade et al. reported the case of a patient who underwent deltopectoral flap reconstruction after 30-Gy irradiation, in which most of the midportion of the tongue base remained. Shibahara et al. studied 12 patients who underwent reconstruction using a free forearm flap over a postoperative period of 3–5 years. They found that taste thresholds were low in both the chorda tympani and glossopharyngeal nerve regions, but details regarding the remaining tongue volume were not given. In our experience, most patients have no change in taste after subtotal glossectomy, but some do experience taste disorders. Therefore, the capacity of patients to recover taste and tongue function after aggressive glossectomy and reconstructive surgery for tongue carcinoma remains controversial and may depend on the extent of tissue excision. Specific information on this subject may lead to improvements in surgical strategies and optimize the quality of life of these patients.

The present study investigated taste in patients with tongue carcinoma who underwent total or subtotal glossectomy and reconstruction. The multidisciplinary approach combined a detailed questionnaire with quantitative analysis of taste in the tongue and oropharynx using four taste solutions (sweet, salt, sour, and bitter).

Materials and methods

Patient selection

The study subjects were 24 patients who underwent total or subtotal glossectomy and reconstruction with flaps ( Table 1 ). Informed consent was obtained from all patients. We excluded patients who had undergone radiotherapy and those undergoing chemotherapy at the time of the study. The patients included 21 men and three women aged 37–79 years (average age 57.8 years). All patients had undergone preoperative chemotherapy and neck dissection (bilateral, 21 cases; unilateral, four cases).

Table 1
Clinical characteristics of the patients.
Parameters Values
Sex
Male 21
Female 3
Age, years
Mean ± SD 57.8 ± 11.3, range 37–79
Postoperative interval (months)
Mean ± SD 30.5 ± 39.6, range 2–158
Chemotherapy 24
CDDP + 5-FU 21
CDDP + 5-FU + MTX 1
CDDP + 5-FU + TS-1 1
CDDP + TS-1 1

SD, standard deviation; CDDP, cisplatin; 5-FU, fluorouracil; MTX, methotrexate; TS-1, tegafur–gimeracil–oteracil potassium.

Table 2 provides details of the surgical treatment of the 24 study patients. Six patients underwent a total glossectomy, whereas 18 underwent a subtotal glossectomy. Among patients with subtotal glossectomy, operative notes indicated that >2/3 of the tongue base remained in one patient, 1/2 remained in three patients, 1/3 remained in 11 patients, and <1/4 of the tongue base remained in three patients. In addition, 11 patients were able to see their remaining tongue from the mouth. Twenty-two patients underwent reconstruction by free rectus abdominis musculocutaneous flap, one by free anterior lateral thigh perforator fasciocutaneous flap, and one by pectoralis major myocutaneous flap. The timing of assessment ranged between 2 months and 158 months, with an average of 30.5 months after operation.

Table 2
Surgical treatments of the 24 patients.
Treatment Number of patients
Tongue resection
Total glossectomy 6
Subtotal glossectomy 18
Remaining tongue base
2/3 1
1/2 3
1/3 11
1/4 3
Body
Margin 2
Posterior margin 9
Not visible 7
Neck dissection
RND + FND 10
RND + SOND 10
RND alone 4
Reconstruction
RAM 17
RAM + FOC 3
RAM + rib 2
PMMC 1
ALT 1

RND, radial neck dissection; FND, functional neck dissection; SOND, supraomohyoid neck dissection; RAM, rectus abdominis musculocutaneous flap; FOC, fibular osteocutaneous flap; PMMC, pectoralis major myocutaneous flap; ALT, anterior lateral thigh perforator fasciocutaneous flap.

Interview on taste perception

Subjective symptoms were evaluated by medical interview alone. In particular, it was not considered to be a problem if the patient did not recognize that they had a taste disorder, even if their taste threshold was low. Patients were interviewed about diet, subjective symptoms of taste, and taste changes after surgery. Diet was classified into the following four grades : grade 1 was defined as good, i.e., a diet cooked and eaten in a regular manner, or a diet identical to that before surgery; grade 2 was acceptable, i.e., a softer diet consisting of rice gruel, stewed vegetables, and viscous foods for added thickness; grade 3 was poor, consisting of liquids or a diet prepared by blender and not normal in appearance; grade 4 was defined as an inability to take adequate food by mouth so that tubal feeding was required. Grades 1 and 2 resemble a normal diet, in which eating is a pleasure as well as nutritional support. The immediate sensory impression of the food is dominated by taste, smell, vision, and oral haptic perception, and these modalities interact with each other. Odorants may enhance or suppress taste and vice versa. Food texture affects taste and smell and vice versa. We therefore believe that diet is one of the important factors in taste perception after glossectomy.

Taste test protocol

A taste test by filter paper disc method, one of the few objective estimates of taste besides electrogustometry, was used to evaluate the taste threshold. This method is carried out using the four basic tastes divided into five concentration grades: 0.3%, 2.5%, 10%, 20%, and 80% sucrose (sweet); 0.3%, 1.25%, 5%, 10%, and 20% NaCl (salty); 0.02%, 0.2%, 2%, 4%, and 8% tartaric acid (sour); and 0.001%, 0.02%, 0.1%, 0.5%, and 4% quinine (bitter). Each solution has no smell. Differential thresholds were determined by testing increasing concentrations followed by rinsing with water, and there was an interval of more than 30 s before proceeding to the next taste. In accordance with the manufacturer’s instructions and the original study, the bitter taste was tested last, but the others were randomized so that the subjects would not anticipate the next taste. To prevent aspiration, we used a fine cotton swab instead of the original filter paper disc. Soaked cotton swabs were placed on the posterior wall of the oropharynx and the remaining tongue, if it was visible. The lowest concentration was designated as the threshold score for each taste. If grade 5, the highest concentration, was not identified, we assigned a score of 6. The same test was performed on the tongue of 15 healthy adults (nine male and six female; mean age 34.0 ± 8.1 years) as a control.

The study design and protocols were approved by the institutional ethics committee.

Results

The medical interview revealed taste complaints in 11 of the 24 patients ( Table 3 ), including 7/18 patients who underwent subtotal glossectomy and 4/6 who underwent total glossectomy. Of these 11 patients, three experienced a decrease in certain tastes, three experienced an absence of certain tastes, four experienced a strong sensation of certain tastes, and one experienced a persistent salty taste in the absence of external stimuli. There was no significant relationship between taste complaints and the type of glossectomy.

Jan 19, 2018 | Posted by in Oral and Maxillofacial Surgery | Comments Off on Subtotal glossectomy preserving half the tongue base prevents taste disorder in patients with tongue cancer
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