Differential Diagnosis

The differential diagnosis for the given conditions can be organized into the following categories:

• Single Most Likely Diagnosis:

  • Subarachnoid hemorrhage (SAH) - This is often considered the most critical diagnosis to rule out due to its high morbidity and mortality if not promptly treated. SAH typically presents with a sudden, severe headache (often described as "the worst headache of my life"), which can be accompanied by nausea, vomiting, and altered mental status.

• Other Likely Diagnoses:

  • Meningitis - Infection of the meninges can present with headache, fever, neck stiffness, and altered mental status. The severity and rapid onset can sometimes mimic SAH.
  • Trigeminal neuralgia - Characterized by sudden, severe, shock-like or stabbing pain in parts of the face, which can be mistaken for a headache. However, the pain is typically unilateral and limited to the distribution of the trigeminal nerve.
  • Giant cell arteritis - This condition, more common in older adults, can cause headaches due to inflammation of the blood vessels, particularly those in the head. It often presents with temporal headache, jaw claudication, and visual disturbances.

• Do Not Miss Diagnoses:

  • Subarachnoid hemorrhage (SAH) - Again, due to its high risk of severe morbidity and mortality, SAH must be ruled out promptly, even if the initial presentation seems atypical.
  • Meningitis - Especially bacterial meningitis, which requires immediate antibiotic treatment to prevent serious complications and death.
  • Giant cell arteritis - If left untreated, it can lead to blindness and other serious complications.

• Rare Diagnoses:

  • Cerebral venous sinus thrombosis - A rare cause of headache that can mimic other conditions, characterized by thrombosis of the cerebral venous sinuses.
  • Primary thunderclap headache - A rare condition characterized by a very severe headache that reaches its maximum intensity within a minute, often without an identifiable cause.
  • Pituitary apoplexy - A rare but potentially life-threatening condition caused by hemorrhage or infarction of the pituitary gland, presenting with sudden, severe headache, visual disturbances, and altered mental status.

Each of these diagnoses has distinct features, but overlapping symptoms can make differential diagnosis challenging. A thorough history, physical examination, and appropriate diagnostic tests (such as imaging studies and lumbar puncture) are crucial for accurate diagnosis and timely management.