From the Guidelines
Central nervous system (CNS) infection symptoms can indeed wax and wane, making diagnosis and management challenging. This fluctuation in symptom intensity is a characteristic of many CNS infections, including viral encephalitis, as described in the management guidelines by the Infectious Diseases Society of America 1. Patients may experience periods where symptoms like headache, fever, altered mental status, or neurological deficits temporarily improve before worsening again. The body's immune response, changes in intracranial pressure, intermittent inflammatory responses, or the pathogen's lifecycle and activity patterns can contribute to this pattern. Some key points to consider in the diagnosis of CNS infections include:
- The importance of cerebrospinal fluid (CSF) analysis, which can reveal a mild mononuclear pleocytosis, elevated protein concentration, and the presence of red blood cells or eosinophils, as noted in the guidelines 1
- The use of nucleic acid amplification tests, such as PCR, to diagnose infections like herpes simplex encephalitis, with reported sensitivities and specificities of 96%–98% and 95–99%, respectively, in adults 1
- The potential for false-negative results, particularly if hemoglobin or other inhibitors are present in CSF, highlighting the need for repeated testing in some cases 1 Healthcare providers should maintain a high index of suspicion for CNS infections, even when symptoms aren't consistently present, and consider the patient's clinical features, epidemiology, and results of diagnostic studies to guide management decisions.
From the Research
CNS Infection Symptoms
- CNS infection symptoms can be nonspecific and may include headache, fever, altered mental status, and behavioral changes 2
- In immunocompromised patients, even mild forms of these symptoms should initiate an evaluation for possible CNS infection 3
- Symptoms can be due to specific organisms or pathologic changes at the neuroanatomic site of infection, and may not be specific to a single causative agent 3
Waxing and Waning of Symptoms
- There is no direct evidence in the provided studies to suggest that CNS infection symptoms typically wax and wane
- However, it is noted that recurrence of symptoms can occur, and that patients who have had CNS infections should be reevaluated for the possibility of infection with a different opportunistic organism 3
- Additionally, some infections, such as toxoplasmosis or aspergillosis, may require chronic treatment, and the reintroduction of steroids for the treatment of an underlying cancer may reactivate previously treated disease 3
Importance of Early Diagnosis and Treatment
- Delaying therapy can negatively impact outcomes, particularly with bacterial meningitis and herpes simplex virus encephalitis 2
- Early use of CT or magnetic resonance angiography and venography can help exclude cerebrovascular complications 4
- Neuroimaging and CSF fluid analysis are crucial in confirming the diagnosis of CNS infection 2