Primary headache disorders include tension-type headache and migraine. These headache types can be differentiated based on strict clinical definitions that depend on the patient's signs and symptoms. However, some of the clinical features can overlap, and in addition, the same comorbid conditions can occur in both headache types. Distinction between these headache types on occasion can be difficult due to comorbid conditions such as temporomandibular joint disorders and myofascial pain with forward head posturing, which may be present in both headache disorders, and thus result in similar features in both conditions. Furthermore, chronification, particularly of migraine, leads to a decrease in the associated symptoms of migraine, such as nausea, photophobia, and phonophobia, so that these headaches more closely resemble tension-type headache. Finally, in some patients, both tension-type headache and migraine may occur at different times.