Differential Diagnosis
- Single most likely diagnosis
- West Nile virus: The patient's symptoms, including fever, progressive confusion, lower extremity weakness, and a history of recent camping trip, are consistent with West Nile virus infection, particularly the neuroinvasive form. The presence of bilateral Babinski sign and the patient's inability to move his right lower extremity also suggest central nervous system involvement.
- Other Likely diagnoses
- Herpes simplex virus: Although less likely, herpes simplex virus encephalitis can present with fever, confusion, and focal neurological deficits. However, the absence of headache and the patient's recent camping trip make West Nile virus more likely.
- Streptococcus pneumoniae: Meningitis caused by Streptococcus pneumoniae can present with fever, confusion, and neurological deficits. However, the absence of nuchal rigidity and the normal CT scan of the head make this diagnosis less likely.
- Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
- Mycobacterium tuberculosis: Tuberculous meningitis can present with fever, confusion, and neurological deficits. Although less likely, it is a potentially deadly diagnosis that should not be missed, especially in immunocompromised patients.
- JC virus: Progressive multifocal leukoencephalopathy (PML) caused by JC virus can present with neurological deficits and confusion. However, PML typically occurs in immunocompromised patients, and the patient's history does not suggest immunocompromise.
- Rare diagnoses
- Eastern equine encephalitis virus: This virus can cause encephalitis with similar symptoms to West Nile virus, but it is much rarer and typically associated with more severe disease.
- Powassan virus: This virus can cause encephalitis with similar symptoms to West Nile virus, but it is rare and typically associated with a history of tick bite.