Mastoiditis: This is an infection of the mastoid bone, which is located behind the ear. It often presents with pain over the mastoid area, fever, and can be a complication of untreated or inadequately treated otitis media. The proximity of the mastoid bone to the middle ear and its role in the structure of the ear make mastoiditis a common cause of pain in this area.

Otitis Media: An infection of the middle ear, which can cause referred pain to the mastoid area due to the shared innervation. It's a common condition, especially in children, and can lead to mastoiditis if not properly treated.
Temporal Arteritis: Inflammation of the temporal artery, which can cause pain in the temporal and mastoid regions. It's more common in older adults and can lead to serious complications like vision loss if not treated promptly.
Tension Headache: A common type of headache that can cause pain on one or both sides of the head, including the mastoid area. The pain is usually described as a band or a squeezing sensation around the forehead, back of the neck, or both.

Meningitis: An infection of the protective membranes covering the brain and spinal cord, known as the meninges. It can present with headache, fever, and neck stiffness. Meningitis is a medical emergency and requires immediate treatment.
Subarachnoid Hemorrhage: Bleeding into the space between the brain and the tissue that covers it (the subarachnoid space). It can cause a sudden, severe headache, often described as "the worst headache" ever experienced. This condition is life-threatening and requires immediate medical attention.
Cavernous Sinus Thrombosis: A blood clot in the cavernous sinus, a group of veins located behind the eye. It's a rare but potentially life-threatening condition that can cause headache, among other symptoms.

Mastoid Osteoma: A benign bone tumor that can occur in the mastoid part of the temporal bone. It's rare and usually asymptomatic but can cause pain if it presses on surrounding structures.
Eagle Syndrome: A condition caused by an elongated or calcified styloid process (a bone at the base of the skull) that can cause pain in the face and ear, including the mastoid area. It's relatively rare and often diagnosed after other causes of pain have been ruled out.
Giant Cell Arteritis (involving the occipital artery): While more commonly associated with the temporal artery, giant cell arteritis can involve other arteries, including the occipital artery, which supplies the back of the head and could potentially cause pain in the mastoid area.