NICE encourages further research on transcutaneous stimulation of the cervical branch of the vagus nerve for cluster headache and migraine. Studies should describe whether the procedure is used for treatment or prevention, and whether it is used for cluster headache or migraine. Clinicians should clearly document details of patient selection and the treatment regimen. Outcome measures should include changes in the number and severity of cluster headache or migraine episodes, medication use, quality of life in the short and long term, side effects, acceptability, and device durability. NICE may update this guidance on publication of further evidence.