What is your threshold for pursuing a lumbar puncture in an older hospitalized patient with acute altered mental status when the initial workup — including labs, imaging, and urinalysis — is unrevealing?

My threshold for lumbar puncture in an older hospitalized patient with acute altered mental status is high. In my practice, I will not pursue an LP in a patient over 65 solely because an otherwise routine evaluation for delirium is unrevealing. A negative workup alone does not sufficiently increase ...