Differential Diagnosis

The patient's presentation with severe headache, photo and phonophobia, left-sided numbness, and minimal weakness, which are improving, suggests a range of possible diagnoses. Here's a categorized differential diagnosis:

• Single Most Likely Diagnosis
  • Minor stroke or Transient Ischemic Attack (TIA): The patient's symptoms of severe headache, left-sided numbness, and minimal weakness, which are improving, align with a minor stroke or TIA. The improvement in symptoms and the absence of fever or significantly elevated WBC count support this diagnosis.
• Other Likely Diagnoses
  • Migraine with aura: The severe headache, photo and phonophobia, and the presence of neurological symptoms like numbness could suggest a migraine with aura, especially if the patient has a history of migraines.
  • Viral meningitis: Although less likely due to the absence of documented fever and normal WBC count, viral meningitis can present with headache, photophobia, and mild neurological symptoms. However, the improving nature of the symptoms makes this less likely.
• Do Not Miss Diagnoses
  • Bacterial meningitis: Despite the low likelihood due to the absence of fever, normal WBC count, and improving symptoms, bacterial meningitis is a "do not miss" diagnosis due to its high morbidity and mortality if not promptly treated. Urgent LP and antibiotics might be considered if there's a high index of suspicion, but the current presentation makes it less likely.
  • Encephalitis: Similar to bacterial meningitis, encephalitis (inflammation of the brain tissue) can present with headache, fever (which might not always be present), and neurological symptoms. Its severity and potential for serious outcomes make it a "do not miss" diagnosis.
• Rare Diagnoses
  • CNS vasculitis: A rare condition involving inflammation of the blood vessels in the brain, which can present with headache, neurological deficits, and might mimic other conditions like stroke or meningitis.
  • Multiple sclerosis (MS): An initial presentation of MS could involve neurological symptoms like numbness and weakness, but the acute onset and improvement of symptoms, along with the absence of other typical MS features (e.g., optic neuritis, spinal cord symptoms), make this less likely.

Given the patient's improving symptoms and the absence of clear indicators of infection (normal WBC count, no documented fever), starting urgent antibiotics and performing an LP might not be immediately necessary unless the clinical picture changes or there's a high suspicion of bacterial meningitis or another severe infection. However, close monitoring and further evaluation are crucial to rule out other serious conditions.