Tension Headache: This is the most common type of headache and is often described as a band or a squeezing sensation around the forehead, usually accompanied by muscle tension in the neck and scalp. Its high prevalence and the common presentation of persistent headaches make it a likely candidate.

Migraine: Characterized by recurrent episodes of severe headaches, often unilateral and accompanied by nausea, vomiting, and sensitivity to light and sound. Migraines can be persistent and are a common cause of headache disorders.
Chronic Daily Headache: This includes a variety of headache disorders that occur 15 days or more per month, such as chronic tension-type headache, chronic migraine, and new daily persistent headache. The persistent nature of the headaches fits this category.
Sinusitis: Inflammation of the sinuses can cause headaches, typically facial pain and pressure, which can be persistent if the underlying infection or inflammation is not adequately treated.

Subarachnoid Hemorrhage: Although less common, this condition, often due to aneurysm rupture, can present with a sudden, severe headache (thunderclap headache) and is a medical emergency. Missing this diagnosis can be fatal.
Brain Tumor: Headaches due to brain tumors can be persistent and may worsen over time. They are often accompanied by other neurological symptoms such as seizures, confusion, and focal neurological deficits.
Temporal Arteritis: An inflammatory condition affecting the blood vessels, particularly in individuals over 50, which can cause persistent headaches, jaw claudication, and visual disturbances. If untreated, it can lead to blindness.
Idiopathic Intracranial Hypertension: Characterized by increased intracranial pressure without a detectable cause, leading to persistent headaches, often worse in the morning, and can be associated with vision changes and papilledema.

Trigeminal Neuralgia: A chronic pain condition that affects the trigeminal nerve, causing intense shock-like or stabbing pain in parts of the face. While not typically described as a headache, it can be confused with headache disorders due to its facial pain component.
Hemicrania Continua: A rare headache disorder characterized by a continuous, often unilateral headache with periods of exacerbation. It is highly responsive to indomethacin.
Cervicogenic Headache: Originates from the cervical spine and is often associated with neck movement or pressure on specific areas of the neck. It is less common but should be considered in the differential diagnosis of persistent headaches.