Numbness of the tongue at night needs to be observed for concomitant symptoms.
If it is accompanied by confusion, numbness or hemiparesis in one limb, or voice disturbance, consider ischaemic cerebrovascular disease.
If it is accompanied by neck pain and impaired movement, consider cervical spondylosis.
If there are no accompanying symptoms and the numbness of the tongue is light in the morning and gets worse gradually, consider burning mouth syndrome.
Specific medical attention is required to confirm the diagnosis with further investigations.