Efficacy of Botox Injection of the Masticatory Muscles in Head &Neck Cancer Patients with Trismus After Radiotherapy

Inclusion Criteria: 1. Aged over 18 years old; 2. Head and neck cancer patients must have completed radiotherapy for at least 3 months; 3. Those whose mouth-opening distance is less than or equal to 3.5 cm (the functional cut-off point of trismus) and who have tightness or pain in the masticatory muscles; 4. Medical condition is stable; Exclusion Criteria: 1. Those who have undergone surgery on their masticatory muscles; 2. Patients with obvious muscle atrophy or complete fibrosis of masticatory muscles ; 3. Those with tumor recurrence at the time of admission; 4. Those whose vital signs are unstable due to acute illness.