Differential Diagnosis for 1.5 Year History of Dull Headache and Occasional Unilateral Pupils Dilation

• Single Most Likely Diagnosis
  • Migraine: This condition is a common cause of dull headaches and can sometimes be accompanied by neurological symptoms such as unilateral pupillary dilation due to its effects on the autonomic nervous system. The long duration of symptoms also fits with a chronic condition like migraine.
• Other Likely Diagnoses
  • Cluster Headaches: These are severe headaches that occur in cycles or clusters, often accompanied by autonomic symptoms like pupillary dilation on the same side as the headache. While they are typically more severe and shorter-lived than described, variations can occur.
  • Tension-Type Headaches: Although less likely to cause pupillary dilation, tension-type headaches are very common and can have a long duration, fitting the 1.5-year history. The pupillary dilation could be an unrelated or secondary symptom.
• Do Not Miss Diagnoses
  • Brain Tumor: A tumor in the brain could cause increased intracranial pressure leading to headaches and, depending on its location, could affect the autonomic nervous system, causing pupillary dilation. This diagnosis is critical to rule out due to its severe implications.
  • Aneurysm or Arteriovenous Malformation (AVM): These vascular abnormalities can cause headaches and, if they press on nearby nerves, could lead to pupillary dilation. They are potentially life-threatening if they rupture.
  • Third Cranial Nerve (Oculomotor Nerve) Palsy: This condition can cause pupillary dilation and, if due to an aneurysm or other compressive lesion, is a medical emergency.
• Rare Diagnoses
  • Syphilis: In its tertiary stage, syphilis can cause a wide range of neurological symptoms, including headaches and pupillary abnormalities. However, this would be an uncommon presentation.
  • Multiple Sclerosis: This autoimmune disease can cause a variety of neurological symptoms, including vision problems and headaches. While pupillary dilation is not a common symptom, the disease's unpredictability means it cannot be entirely ruled out without further investigation.
  • Autonomic Dysfunction: Certain conditions affecting the autonomic nervous system, like dysautonomia, can cause pupillary dilation among other symptoms. These conditions are less common and might not fully explain the headache component without additional symptoms.