The patient was a 41-year-old man with a diagnosis of squamous cell carcinoma of the tongue on the left side (T₄N₀M₀). The patient underwent subtotal glossectomy and reconstruction with a rectus abdominis musculocutaneous flap at Kindai University Hospital, Osaka in 2008. Table 1 lists the details of the surgical procedure. With regard to preservation of the suprahyoid muscles, the patient retained the unilateral posterior mylohyoid and unilateral stylohyoid muscles (Table 1). Hyoid bone suspension was not performed (Table 1). Postoperatively,

the patient did not receive chemotherapy or radiation therapy.

1) Postoperative flap structure

We evaluated the structure of the flap both 1 month and 1 year after surgery. The flap could be classified as protuberant, semiprotuberant, flat, or depressed [5] .

2) Video fluorography

Swallowing function was evaluated with video fluorography before surgery, 1 month after surgery, and 1 year after surgery. In the test, the following items were evaluated with a 10 mL of liquid: a) holding the liquid in the oral cavity, b) epiglottis turnover, c) aspiration, d) hyoid bone movement, and e) maximum width of the esophageal entrance.

To examine the extent of hyoid bone movement (Figure 1, and Figure 2) and the maximal widening of the esophageal entrance (Figure 3), the method of Matsunaga et al. [4] [6] was used. Points A and B represented the lower and upper borders of the fourth cervical vertebra, respectively. Points C and C¢represented the hyoid bone at rest and at the highest elevation, respectively. Then the distance from point A to point C (line AC) and the distance from point A to point C¢ (line AC¢) were measured (relative to the height of the third cervical vertebra, which on a lateral image was set as 10.0). Angles BAC and BAC¢ represented the angles when the hyoid bone angle was at rest and at the highest elevation, respectively (Figure 1). Figure 2 shows the method of assessing the extent of hyoid bone movement. The Y-axis was parallel to the line from point A

to point B (line AB), and the X-axis was perpendicular to line AB (Figure 2). Line CC’ represented the distance between the position of the hyoid bone at rest and its position at the highest elevation in relation to the height of the third cervical vertebra set, as 10.0 (Figure 2). Angle C’CX was the angle of hyoid bone movement (Line CX was a line parallel to the X-axis) (Figure 2).

Figure 3 shows the method of assessing the maximum width of the esophageal entrance [4] [6] [7] . The maximum width of the esophageal entrance was measured during swallowing in relation to the height of the third cervical vertebra (Figure 3).

After subtotal glossectomy, it is important to reconstruct the large defect with an appropriate flap to improve or maintain postoperative swallowing function. We previously reported that for good postoperative swallowing after subtotal glossectomy, it is necessary to perform reconstruction with a flap that has sufficient volume [4] . Kimata et al. [5] suggested that protuberant and semiprotuberant flaps demonstrated better postoperative swallowing function than did flat or depressed flaps; therefore, the large tongue defect should be reconstructed with the wider and thicker flaps. Chang et al. [8] suggested that defects after subtotal or total glossectomy should be reconstructed with a thicker and bulkier flap to optimize postoperative speech and swallowing function. The patient in this study, who had undergone reconstruction of a flap with sufficient volume, demonstrated good ability to hold liquid in the oral cavity after surgery, and flow of liquid into the pharynx was not observed after surgery. These findings demonstrate the necessity of reconstruction of a protuberant flap for good postoperative swallowing after subtotal glossectomy. Some authors [8] [9] have suggested that functional reconstruction of a flap with both sensory and motor innervation can result in better postoperative swallowing outcomes after subtotal glossectomy. In the future, we hope to examine functional reconstruction of tongue defect with innervated flaps.

With regard to the association between resection of the suprahyoid muscles and hyoid bone movement during swallowing, Fujimoto et al. [10] suggested that the hyoid bone movement deceased significantly after resection of the suprahyoid muscles. We reported that after bilateral resection of the anterior and posterior bellies of the digastric, mylohyoid, geniohyoid, and hyoglossus muscles, the forward and upward movement of the hyoid bone was impeded [11] . However, the degree of the hyoid bone movement during swallowing had not been quantitatively evaluated. Therefore, we evaluated postoperative swallowing function in patents who underwent subtotal glossectomy and reconstruction with a rectus abdominis musculocutaneous flap [7] . We found that in patients who have undergone subtotal glossectomy and bilateral neck dissection-, the extent of hyoid bone muvement was definitely smaller than that in patients after only unilateral neck dissection [4] [6] . However, we had not quantitatively evaluated changes in hyoid bone movement before and after surgery. In this study, we evaluated change in hyoid bone movement and width of the esophageal entrance in a patient who underwent subtotal glossectomy and bilateral neck dissection. The positions of the hyoid bone at rest were lower after surgery than before surgery because almost all of the bilateral suprahyoid muscles had been resected without hyoid bone suspension. Furthermore, hyoid bone movement and width of the esophageal entrance decreased after surgery; however, they demonstrated gradual recovery, which may have been a result of strengthening of the retained suprahyoid muscles and compensatory reinforcement of the infrahyoid muscles.

The limitation of this study is that it is a case report; more cases like this should be studied. Furthermore, a comparative study analyzing swallowing function based on hyoid bone suspension in patients who have undergone subtotal glossectomy is needed.