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The correct answer is Medication induced delirium (G).
This was a difficult case, but with the information provided the most likely answer should be clear. It’s an important topic, as this is a commonly-encountered clinical scenario that may be difficult to tease out of a patient’s presentation. Let’s rule out the wrong answers:
Subdural hematoma (A) is unlikely, as there is no history of trauma and the patient’s CT scan was normal. VZV encephalitis (B) is less likely, given the patient’s history and the fact that the patient was being treated with acyclovir. The patient does not have fever or significant neurologic findings associated with Meningitis (C) and the CSF analysis, though slightly abnormal, does not suggest this diagnosis. A Stroke (D), though not excluded with a normal CT scan, usually does not present with acute changes in mental status without focal neurologic findings. CNS vasculitis (E) is rare, even in patients with microscopic polyangiitis; additionally, the patient’s inflammatory markers would be expected to be elevated*. Major depression with psychosis (F) cannot be excluded on initial workup, but must be a diagnosis of exclusion in the context of this patient’s acute presentation and while taking centrally-acting/psychoactive medications.
The diagnosis is especially important in this case as the initial management with additional benzodiazepenes and anti-psychotics likely worsened the patient’s condition. Withdrawal of the offending medications led to an improvement in the patient’s mental status.
The Beers Criteria for Potentially Inappropriate Medication Use in Older Adults (or simply Beers List) was created in the 1990s to help caution providers when prescribing medications with risk profiles that may potentially outweigh the benefits in the elderly. The list was recently updated in 2012, and with the growing popularity of the topic, other lists and screening tools have been developed.
*The patient’s CRP, which is an acute phase reactant, should be elevated in sync with an inflammatory process. The ESR is an inflammatory marker that may lag, but is also directly correlated to one’s age – the normal range is 0-20, but a general rule of thumb for older individuals is: (Patient’s age + 20 / 2) = Corrected upper limit of normal. For this patient, the acceptable limit would be 50.
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