Indications for Lumbar Puncture in Ocular VZV
Lumbar puncture should be performed in patients with ocular VZV when there are any signs or symptoms suggesting CNS involvement, including headache, altered mental status, fever, meningismus, focal neurological deficits, or unexplained cognitive changes, as VZV meningoencephalitis can occur even in immunocompetent patients and requires prompt diagnosis for appropriate intravenous antiviral therapy.
Primary Indications for LP in Ocular VZV
Neurological Symptoms or Signs
- Perform LP immediately if the patient develops headache, fever, altered consciousness, or meningeal signs in the context of ocular VZV, as these suggest possible VZV meningoencephalitis requiring CSF PCR confirmation 1, 2.
- Consider LP for persistent or severe headache that is poorly responsive to standard analgesia, even without fever or rash, as VZV meningitis can present atypically 3.
- Focal neurological deficits warrant urgent LP, including peripheral facial paralysis (present in 19.4% of VZV CNS cases), encephalopathy, or myelitis 2.
- Cognitive difficulties, fatigue, or unexplained neurological symptoms persisting beyond typical ocular VZV should prompt LP, as VZV can cause delayed or subtle CNS involvement 1.
Immunocompromised Status
- LP should have a lower threshold in immunocompromised patients with ocular VZV, as they have higher risk of CNS dissemination, though VZV CNS infection increasingly occurs in immunocompetent individuals 4, 2.
Disease Progression Despite Treatment
- Perform LP if neurological symptoms develop or progress despite oral antiviral therapy, as progression to meningitis can occur even when antivirals are initiated within 48 hours of symptom onset 5.
Contraindications to Immediate LP
Before proceeding with LP, assess for the following contraindications that require CT imaging first:
Absolute Contraindications Requiring CT First
- Moderate to severe impairment of consciousness (GCS <13) or fall in GCS >2 points indicates potential raised intracranial pressure 6, 7.
- Focal neurological signs including unequal, dilated, or poorly responsive pupils suggest space-occupying lesion 6, 7.
- Papilloedema is a direct indicator of raised intracranial pressure 6, 7.
- Abnormal posturing or posture suggests brainstem compromise 6.
Hematologic and Coagulation Contraindications
- Platelet count <100 × 10⁹/L is a contraindication, though LP may be considered with platelet count ≥50 × 10⁹/L with hematology consultation 6, 7.
- Coagulation results outside normal range or anticoagulant therapy require reversal before LP 6, 7.
- Patients on warfarin should be switched to heparin, which is stopped before LP 6.
Other Contraindications
- Local infection at the LP site prevents safe puncture 6, 7.
- Systemic shock or clinical instability contraindicates immediate LP 6, 7.
Clinical Algorithm
Step 1: Clinical Assessment
- Evaluate for contraindications to immediate LP using clinical examination rather than relying on CT as the primary determinant 7.
- If no contraindications exist, proceed directly to LP without delay for CT imaging 7.
Step 2: If Contraindications Present
- Obtain CT scan as soon as possible to assess for brain shift, tight basal cisterns, or raised ICP 7.
- If CT shows significant abnormalities, defer LP and manage raised ICP first 7.
- If CT is normal but clinical contraindications persist, consider LP on a case-by-case basis, as the diagnostic information is essential 6.
Step 3: CSF Analysis
- Collect at least 10 mL of CSF to avoid repeat procedures 7.
- Send CSF for VZV PCR, which is the gold standard for diagnosis 1, 2.
- Note that 5-10% of VZV encephalitis cases may have normal initial CSF findings, so repeat LP may be necessary if clinical suspicion persists 6, 7.
Important Clinical Pearls
Atypical Presentations
- VZV CNS infection can occur without rash or fever in immunocompetent patients, so maintain high clinical suspicion 3.
- Symptoms may persist for weeks to months before diagnosis if LP is delayed, emphasizing the importance of early consideration 1.
Diagnostic Considerations
- VZV DNA may be present in saliva in 80% of VZV meningoencephalitis cases, though this is not a substitute for CSF PCR 4.
- CSF typically shows pleocytosis (average 196.60 × 10⁶/L WBC), elevated protein (average 1.35 g/L), and elevated opening pressure (28.1% of cases) 2.