The inability to extend the tongue is called tongue extension difficulty. Possible causes include abnormal tongue development, tongue cancer and post-surgical reaction to tongue cancer, systemic amyloidosis, systemic lupus erythematosus, and so on. 1. Abnormal tongue development: If the tongue tie is too short, it may lead to tongue extension difficulty. 2. Tongue cancer and postoperative reaction of tongue cancer: the growth of tumor tissue compresses the hypoglossal nerve, or the hypoglossal nerve is damaged during operation, which may cause difficulty in tongue extension. 3. Systemic amyloidosis: the tongue body may be enlarged and stiff due to the deposition of amyloid material, which may cause tongue extension difficulty. 4. Systemic lupus erythematosus: autoantibodies and inflammatory mediators mediated inflammatory response can cause central nervous system lesions, resulting in tongue extension difficulties. There may be other reasons for tongue extension difficulties, and it is recommended to go to the hospital in time to receive targeted treatment.