Differential Diagnosis for Unilateral Headache

When considering a unilateral headache, it's crucial to approach the diagnosis systematically to ensure that no critical conditions are overlooked. The differential diagnosis can be categorized as follows:

• Single Most Likely Diagnosis

  • Migraine: This is often the most common cause of unilateral headaches. Migraines are characterized by recurrent episodes of severe headaches, often accompanied by sensitivity to light, sound, or nausea, and can be unilateral in nature.

• Other Likely Diagnoses

  • Cluster Headache: Known for their severe, unilateral pain, typically centered around one eye, cluster headaches occur in cyclical patterns or clusters.
  • Tension-Type Headache: Although often bilateral, tension-type headaches can occasionally present unilaterally, characterized by a pressing or tightening sensation.
  • Temporomandibular Joint (TMJ) Disorder: Pain from TMJ disorders can radiate to one side of the face, mimicking a unilateral headache.
  • Sinusitis: Inflammation of the sinuses can cause pain on one side of the face, depending on which sinuses are affected.

• Do Not Miss Diagnoses

  • Subarachnoid Hemorrhage: A life-threatening condition caused by bleeding into the space surrounding the brain, often presenting with a sudden, severe headache (sometimes unilateral).
  • Temporal Arteritis: An inflammation of the blood vessels in the temple, which can cause unilateral headache, especially in older adults, and can lead to blindness if not treated promptly.
  • Acute Angle-Closure Glaucoma: A medical emergency that can cause severe, unilateral eye pain and headache, along with blurred vision and nausea.
  • Cervicogenic Headache: Originating from the cervical spine, these headaches can be unilateral and are often associated with neck movement or pressure.

• Rare Diagnoses

  • Trigeminal Neuralgia: Characterized by intense, shock-like or stabbing pain in parts of the face, which can be mistaken for a unilateral headache.
  • Occipital Neuralgia: Involves inflammation of the occipital nerves, leading to severe, unilateral pain in the back and side of the head.
  • Hemicrania Continua: A rare form of headache disorder that causes continuous, unilateral pain, often accompanied by autonomic symptoms like nasal congestion or eye watering.
  • Primary Thunderclap Headache: A very severe headache that reaches its maximum intensity within a minute, often described as the worst headache of a person's life, and can be unilateral.

Each of these diagnoses has distinct characteristics and accompanying symptoms that can help guide the differential diagnosis. A thorough history and physical examination, along with appropriate diagnostic tests when necessary, are crucial for accurately diagnosing the cause of a unilateral headache.