From the Guidelines
A lumbar puncture (LP) can be deferred to the inpatient setting for patients with suspected viral encephalitis who are clinically stable and have no signs of increased intracranial pressure, as the diagnosis and management of this condition do not require immediate intervention in the Emergency Room (ER) setting. This approach is supported by the guidelines for the management of suspected viral encephalitis in children, which suggest that a CT scan can be used to suggest alternative diagnoses and indicate the need for a LP 1. In patients with suspected encephalitis, an early CT scan can show suggestive abnormalities in about 80% of patients with herpes simplex virus (HSV) encephalitis, and a negative initial scan will have abnormalities on a second scan 1.
The decision to defer LP should be made after careful clinical assessment, including vital signs, mental status, and neurological examination. If there are any signs of increased intracranial pressure (severe headache, papilledema, altered mental status), neuroimaging should be performed before LP regardless of setting 1. The rationale for deferring certain LPs to inpatient care includes the ability to perform the procedure in a more controlled environment, with appropriate monitoring and immediate access to interventions if complications arise.
Some conditions that may not require an emergent LP in the ER setting include:
- Suspected subacute or chronic meningitis
- Normal pressure hydrocephalus
- Pseudotumor cerebri (idiopathic intracranial hypertension)
- Multiple sclerosis workup
- Chronic inflammatory demyelinating polyneuropathy These conditions typically develop over weeks to months rather than hours to days, allowing time for inpatient evaluation. In contrast, emergency LP is necessary for suspected bacterial meningitis, subarachnoid hemorrhage, or other acute neurological emergencies where immediate diagnosis affects treatment decisions.
It is essential to note that LP may be harmful in patients with coagulopathy, and the standard recommendation is to perform a lumbar puncture only when the patient does not have a coagulopathy and has a platelet count of 100 109/L or greater 1. A rapidly falling count is also a contraindication. Haemorrhage can occur in patients anticoagulated with heparin or warfarin, but in one large study, preoperative antiplatelet therapy with aspirin or nonsteroidal anti-inflammatory medications and subcutaneous heparin on the operative day were not risk factors for spinal haematoma in patients undergoing spinal or epidural anaesthesia 1.
From the Research
Clinical Presentation
The clinical presentation that does not require an emergent lumbar puncture (LP) in the Emergency Room (ER) but can be performed in an inpatient setting includes:
- Aseptic meningitis, which is most commonly caused by herpes simplex virus (HSV) 2
- Recurrent aseptic meningitis, also known as Mollaret's meningitis, which is a self-limiting condition that often requires no intervention or suppressive antivirals 2
- Acute aseptic meningitis in adults, which can be managed with supportive care and does not always require antibiotic or antiviral treatment 3
Diagnostic Considerations
When diagnosing meningitis, it is essential to consider the following:
- Lumbar puncture (LP) is a crucial diagnostic tool, but it may not always be necessary to perform it emergently in the ER 4
- Delayed LPs can still be diagnostic, especially if performed within 4 hours of starting antibiotics 4
- Molecular tests, such as PCR, can be useful in diagnosing viral meningitis, including HSV 5, 6, 2
Management
The management of meningitis depends on the underlying cause and severity of the disease. In some cases, such as aseptic meningitis, supportive care may be sufficient, while in other cases, antiviral or antibiotic treatment may be necessary 5, 6, 2, 3