What is the appropriate treatment for an 11-year-old patient with suspected meningitis, presenting with ataxia, nystagmus, hypertension, and abnormal cerebrospinal fluid (CSF) findings, including lymphocytic pleocytosis?

Immediate Empirical Treatment for Suspected Bacterial Meningitis with Atypical Features

This 11-year-old patient requires immediate empirical antibiotic therapy with vancomycin plus ceftriaxone, initiated within one hour of presentation, despite the minimal CSF pleocytosis, because bacterial meningitis can present with minimal or absent pleocytosis and the clinical features (fever, ataxia, nystagmus, cranial nerve enhancement, hypertension, bradycardia) strongly suggest CNS infection. 1

Critical Recognition: Bacterial Meningitis Without Pleocytosis

• Bacterial meningitis occurs in the absence of CSF pleocytosis in up to 20% of cases, particularly early in disease course or with short symptom duration 1, 2
• The mortality rate for bacterial meningitis without pleocytosis is 31%, making delayed treatment potentially fatal 2
• Do not dismiss bacterial meningitis based solely on low CSF white cell count (5 cells/μL), as this is a recognized presentation that leads to increased mortality when treatment is delayed 1, 2
• The CSF findings (lymphocytic predominance, normal glucose 69 mg/dL, mildly elevated protein 45 mg/dL) do not exclude bacterial meningitis, particularly partially treated disease or atypical organisms like Listeria monocytogenes 3, 4

Immediate Empirical Antibiotic Regimen

Start within one hour of presentation 1, 5:

• Ceftriaxone 100 mg/kg/day IV once daily (maximum 4 grams/day) 1, 6, 7
• Vancomycin 60 mg/kg/day IV divided every 6 hours to cover penicillin-resistant Streptococcus pneumoniae 1, 7
• Add Ampicillin 2g IV every 4 hours (or 300 mg/kg/day in divided doses for children) because the patient has risk factors for Listeria (lymphocytic predominance, cranial nerve involvement, subacute presentation) 3, 4, 7

Rationale for Triple Therapy

• The lymphocytic predominance raises concern for Listeria monocytogenes, which is resistant to cephalosporins and requires ampicillin 4, 7
• Listeria can present with lymphocytic pleocytosis in 50-70% of cases and commonly causes cranial nerve involvement 4
• The combination provides coverage for S. pneumoniae (including resistant strains), N. meningitidis, H. influenzae, and Listeria 1, 7

Adjunctive Dexamethasone Therapy

• Administer dexamethasone 0.15 mg/kg IV every 6 hours immediately, either shortly before or simultaneously with the first antibiotic dose 3, 1
• Continue for 2-4 days to reduce mortality and morbidity, particularly in pneumococcal meningitis 3, 1
• Dexamethasone reduces inflammation-mediated complications including cranial nerve damage 3

Clinical Features Supporting CNS Infection

The constellation of findings strongly suggests serious CNS pathology requiring immediate treatment:

• Cranial nerve involvement (bilateral VII and VIII nerve complex enhancement) indicates cranial neuritis, a recognized complication of bacterial meningitis that supports the diagnosis despite minimal pleocytosis 1
• Hypertension and bradycardia (heart rate 56-62/min) suggest increased intracranial pressure (Cushing's triad), a life-threatening complication requiring urgent management 5
• Ataxia and nystagmus indicate cerebellar or brainstem involvement, consistent with meningoencephalitis 3
• Pachymeningeal and leptomeningeal enhancement on MRI confirms meningeal inflammation 3

Additional Diagnostic Considerations While Treating

Tuberculosis Meningitis

• If cultures remain negative at 48-72 hours and clinical response is inadequate, strongly consider TB meningitis 1, 4
• The lymphocytic predominance, elevated protein, cranial nerve involvement, and subacute presentation (10 days of intermittent fever) are classic for TB meningitis 3, 4
• Initiate anti-tuberculous therapy empirically if TB cannot be excluded, as delays worsen outcomes 1

Viral Encephalitis

• Consider adding aciclovir 500 mg/m² IV every 8 hours if the patient deteriorates despite antibiotics or if HSV/VZV encephalitis cannot be excluded 3
• The MRI findings (leptomeningeal enhancement, cranial nerve involvement) and clinical features (ataxia, nystagmus) could suggest viral encephalitis 3
• Aciclovir should be started within 6 hours if viral encephalitis remains a possibility, as delays beyond 48 hours worsen outcomes 3

Autoimmune/Inflammatory Causes

• Consider neurosarcoidosis, autoimmune encephalitis (anti-NMDA receptor), or neuropsychiatric SLE if infectious workup is negative 4
• These conditions can present with lymphocytic pleocytosis, cranial nerve involvement, and meningeal enhancement 4, 8

Essential Monitoring and Investigations

• Obtain blood cultures immediately before antibiotics, as they are positive in 71% of cases of meningitis without CSF pleocytosis 2
• Monitor for signs of increased intracranial pressure given the hypertension and bradycardia 5
• Repeat lumbar puncture at 48-72 hours if no clinical improvement to reassess CSF parameters 7
• Send CSF for TB PCR, fungal culture, and viral PCR (HSV, VZV, enterovirus) 3, 4
• Consider HIV testing, autoimmune panel (ANA, ENA), and serum ACE if infectious workup is negative 4

Duration of Therapy

• Continue antibiotics for at least 10-14 days for pneumococcal meningitis if confirmed 3, 7
• Continue for 21 days for gram-negative bacillary meningitis or Listeria 9, 7
• Continue for 3 weeks for Listeria with gentamicin or cotrimoxazole 7
• Adjust based on culture results and clinical response at 48-72 hours 3, 7

Critical Pitfalls to Avoid

• Do not delay antibiotics for imaging or additional diagnostic procedures, as mortality increases with treatment delays 1, 5
• Do not use ceftriaxone monotherapy in this age group with suspected bacterial meningitis, as vancomycin must be added for pneumococcal coverage 1
• Do not omit ampicillin given the lymphocytic predominance and cranial nerve involvement suggesting possible Listeria 4, 7
• Do not assume viral meningitis based on lymphocytic predominance alone, as bacterial causes (especially Listeria and partially treated meningitis) can present identically 3, 4, 2