Tension Headache: This is the most common type of headache and often presents with bilateral or unilateral pain, typically described as a band or a squeezing sensation around the forehead, back of the neck, or both. The pain is usually mild to moderate and can be exacerbated by stress, poor posture, or muscle tension.

Cervicogenic Headache: Originates from the cervical spine and is often referred to the back of the head, usually on one side. It can be triggered by specific movements or positions of the neck.
Migraine: Although migraines are typically unilateral and can be accompanied by other symptoms like nausea, vomiting, and sensitivity to light and sound, some individuals may experience migraine pain that is referred to the back of the head or neck.
Occipital Neuralgia: Involves the irritation of the occipital nerves, leading to sharp, stabbing, or electric shock-like pain in the back of the head and neck, often on one side.

Subarachnoid Hemorrhage: A life-threatening condition that requires immediate medical attention. Although it typically presents with a sudden, severe headache (often described as "the worst headache of my life"), it's crucial not to miss this diagnosis.
Stroke or Transient Ischemic Attack (TIA): Headache can be a symptom of stroke or TIA, especially if accompanied by other neurological deficits such as weakness, numbness, or difficulty with speech.
Temporal Arteritis (Giant Cell Arteritis): An inflammatory condition affecting the blood vessels, particularly those in the head. It can cause headache, usually on one side, and is associated with jaw claudication, visual disturbances, and polymyalgia rheumatica.

Chiari Malformation: A structural defect in the cerebellum that controls balance, can cause headaches that are often worse with coughing, sneezing, or straining, and may be accompanied by other neurological symptoms.
Atlantoaxial Subluxation: A condition where the first and second cervical vertebrae are out of place, potentially causing severe neck pain and headache, often accompanied by neurological symptoms due to spinal cord compression.
Eagle Syndrome: A rare condition caused by an elongated styloid process or calcified stylohyoid ligament, leading to sharp, stabbing pain in the side of the face and head, often exacerbated by swallowing.