Differential Diagnosis

The patient presents with a severe headache, and given the information provided, the differential diagnosis can be categorized as follows:

• Single Most Likely Diagnosis

  • Sinusitis: The patient's CT scan shows bilateral sinus mucosal disease, including nearly complete opacification of the right frontal sinus. This, combined with the patient's symptoms of a severe headache, suggests sinusitis as the most likely diagnosis. The increased white blood cell count with a mild left shift also supports an infectious process.

• Other Likely Diagnoses

  • Tension Headache: Although the headache is described as really bad, tension headaches can sometimes present with significant severity and could be considered, especially if the sinusitis is not found to be the cause of the headache.
  • Migraine: Given the severity of the headache, migraine could be a consideration, though typically migraines are associated with other symptoms such as photophobia, phonophobia, or aura, which are not mentioned in this case.
  • Hypertension-related Headache: Although the patient's blood pressure is not markedly elevated at the time of presentation, fluctuations in blood pressure could potentially cause headaches.

• Do Not Miss Diagnoses

  • Subarachnoid Hemorrhage (SAH): Despite the CT scan showing no evidence of acute intracranial abnormality, SAH is a diagnosis that must be considered in any patient presenting with a severe headache, especially given the patient's use of anticoagulation for atrial fibrillation. A lumbar puncture may be necessary if clinical suspicion remains high.
  • Intracranial Hemorrhage: Similar to SAH, any form of intracranial hemorrhage (e.g., intraparenchymal, subdural, epidural) is a critical diagnosis to consider, especially in a patient on anticoagulation. The initial CT may have missed a small hemorrhage, or the hemorrhage could have evolved since the scan was performed.
  • Temporal Arteritis (Giant Cell Arteritis): This condition can present with headache and is more common in older adults. It's a diagnosis that could explain the headache and would require prompt treatment to prevent complications such as vision loss.

• Rare Diagnoses

  • Cervicogenic Headache: These are headaches referred from the cervical spine and could be a consideration, though they are less common and typically associated with neck pain or movement.
  • Trigeminal Neuralgia: While this condition can cause severe facial pain, it's less likely given the description of the headache and the absence of specific triggers or radiation patterns typical of trigeminal neuralgia.
  • Venous Sinus Thrombosis: This is a rare condition that could present with headache and is more concerning in patients with hypercoagulable states or on anticoagulation, though the CT findings do not directly suggest this diagnosis.

Next Steps

Given the differential diagnosis, the next steps should include:

• Further evaluation of the sinusitis, potentially with antibiotics if deemed bacterial in nature.
• Consideration of a lumbar puncture if there is a high suspicion for SAH or other intracranial processes not visible on the initial CT scan.
• Review of the patient's anticoagulation regimen and consideration of its implications in the current clinical context.
• Monitoring of the patient's blood pressure and further evaluation if hypertension is suspected as a cause of the headache.
• Consideration of temporal arteritis with appropriate laboratory tests (e.g., ESR, CRP) and potentially a temporal artery biopsy if clinical suspicion is high.