From the Guidelines
A head CT scan should only be obtained before performing a lumbar puncture (LP) if there are clinical signs suggestive of a shift of brain compartments, such as focal neurological signs and a reduced Glasgow Coma Scale (GCS) score, specifically a GCS of ≤12 1.
Indications for Head CT Scan Before LP
- Focal neurological signs
- Reduced GCS score (≤12)
Importance of Prompt LP
Performing a CT scan before LP can lead to delays in administering antibiotics, which can increase mortality 1.
Management Approach
If a CT scan is indicated, it should be performed promptly, and if no contraindication is found, the LP should be done as soon as possible afterwards 1.
Empiric Antibiotic Therapy
If there is a high clinical suspicion for meningitis and a CT scan is not immediately available, empiric antibiotic therapy should be initiated without delay, with typical regimens including ceftriaxone and vancomycin 1.
Prioritizing Patient Outcomes
The primary goal is to minimize delays in treatment and prevent potentially life-threatening complications, prioritizing morbidity, mortality, and quality of life as the outcome 1.
From the Research
Indications for Head Computed Tomography (CT) Scan Before Lumbar Puncture (LP)
- A head CT scan is indicated before performing a lumbar puncture (LP) in certain situations, including:
- Suspected subarachnoid hemorrhage, especially if the headache occurred more than 6 hours prior to patient presentation 2
- Adults with suspected meningitis who have certain clinical features, such as an age of at least 60 years, immunocompromise, a history of central nervous system disease, and a history of seizure within one week before presentation, as well as neurologic abnormalities 3
- Patients with suspected bacterial meningitis who are at risk for intracranial mass effect lesions, based on decision rules or clinical gestalt 4
- The decision to perform a head CT scan before LP should be based on individual patient risk factors and clinical presentation, rather than routine practice 5, 4, 6
- Clinical features that can be used to identify patients who are unlikely to have abnormal findings on CT of the head include a normal level of consciousness, no history of central nervous system disease, and no neurologic abnormalities 3
- The use of decision rules to selectively perform CT on only those individuals most likely to have intracranial mass effect lesions has not undergone validation, and physicians should exercise caution when interpreting these rules 4
Clinical Features and CT Scan Results
- The presence of certain clinical features, such as an abnormal level of consciousness, gaze palsy, and facial palsy, can increase the likelihood of abnormal findings on CT of the head 3
- A normal CT scan does not completely rule out the possibility of subarachnoid hemorrhage or other intracranial abnormalities, and clinical judgment should be used to determine the need for further evaluation 2, 3
- The negative predictive value of a normal CT scan can be high, especially in patients with no clinical signs or symptoms of intracranial abnormalities 5
Timing and Antibiotic Therapy
- In patients with suspected bacterial meningitis, antibiotic therapy should be initiated promptly, and the decision to perform a head CT scan should not delay antibiotic administration 4
- The timing of LP and CT scan should be individualized based on patient risk factors and clinical presentation, and the potential benefits and risks of each procedure should be carefully considered 6