Meningitis Differential Diagnoses

Author: Raymund R Razonable, MD; Chief Editor: Burke A Cunha, MD more...

Updated: Jul 7, 2011

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Diagnostic Considerations

Diagnoses to consider aside from meningitis include the following:

Noninfectious meningitis, including medication-induced meningeal inflammation
Meningeal carcinomatosis
CNS vasculitis
Stroke
Encephalitis
All causes of altered mental status and coma
Leptospirosis
Subdural empyema

Differential Diagnoses

Proceed to Workup

Contributor Information and Disclosures

Author

Raymund R Razonable, MD Consultant, Division of Infectious Diseases, Mayo Clinic of Rochester; Associate Professor of Medicine, Mayo Clinic College of Medicine

Raymund R Razonable, MD is a member of the following medical societies: American Medical Association, American Society for Microbiology, Infectious Diseases Society of America, and International Immunocompromised Host Society

Disclosure: Nothing to disclose.

Coauthor(s)

Robert Cavaliere, MD Assistant Professor of Neurology, Neurosurgery and Medicine, Ohio State University College of Medicine

Disclosure: Nothing to disclose.

Francisco de Assis Aquino Gondim, MD, MSc, PhD Associate Professor of Neurology, Department of Neurology and Psychiatry, St Louis University School of Medicine

Francisco de Assis Aquino Gondim, MD, MSc, PhD is a member of the following medical societies: American Academy of Neurology, American Association of Neuromuscular and Electrodiagnostic Medicine, and Movement Disorders Society

Disclosure: Nothing to disclose.

Alan Greenberg, MD Director, Associate Professor, Department of Internal Medicine, Jersey City Medical Center, Seton Hall University

Alan Greenberg, MD is a member of the following medical societies: Alpha Omega Alpha and American College of Physicians

Disclosure: Nothing to disclose.

Ronald A Greenfield, MD Professor, Department of Internal Medicine, University of Oklahoma College of Medicine

Ronald A Greenfield, MD is a member of the following medical societies: American College of Physicians, American Federation for Medical Research, American Society for Microbiology, Central Society for Clinical Research, Infectious Diseases Society of America, Medical Mycology Society of the Americas, Phi Beta Kappa, Southern Society for Clinical Investigation, and Southwestern Association of Clinical Microbiology

Disclosure: Pfizer Honoraria Speaking and teaching; Gilead Honoraria Speaking and teaching; Ortho McNeil Honoraria Speaking and teaching; Abbott Honoraria Speaking and teaching; Astellas Honoraria Speaking and teaching; Cubist Honoraria Speaking and teaching; Forest Pharmaceuticals Speaking and teaching

J Stephen Huff, MD Associate Professor of Emergency Medicine and Neurology, Department of Emergency Medicine, University of Virginia School of Medicine

J Stephen Huff, MD is a member of the following medical societies: American Academy of Emergency Medicine, American Academy of Neurology, American College of Emergency Physicians, and Society for Academic Emergency Medicine

Disclosure: Nothing to disclose.

Lutfi Incesu, MD Professor, Department of Radiology, Ondokuz Mayis University School of Medicine; Chief, Neuroradiology and MR Unit, Department of Radiology, Ondokuz Mayis University Hospital, Turkey

Lutfi Incesu, MD is a member of the following medical societies: American Society of Neuroradiology and Radiological Society of North America

Disclosure: Nothing to disclose.

Michael R Keating, MD Associate Professor of Medicine, Chair, Division of Infectious Diseases, Department of Medicine, Mayo Clinic College of Medicine

Michael R Keating, MD is a member of the following medical societies: American College of Physicians, American Medical Association, American Society for Microbiology, American Society of Transplantation, Infectious Diseases Society of America, and International Immunocompromised Host Society

Disclosure: Nothing to disclose.

Anil Khosla, MBBS, MD Assistant Professor, Department of Radiology, St Louis University School of Medicine, Veterans Affairs Medical Center of St Louis

Anil Khosla, MBBS, MD is a member of the following medical societies: American College of Radiology, American Roentgen Ray Society, American Society of Neuroradiology, North American Spine Society, and Radiological Society of North America

Disclosure: Nothing to disclose.

Rick Kulkarni, MD Attending Physician, Department of Emergency Medicine, Cambridge Health Alliance, Division of Emergency Medicine, Harvard Medical School

Rick Kulkarni, MD is a member of the following medical societies: Alpha Omega Alpha, American Academy of Emergency Medicine, American College of Emergency Physicians, American Medical Association, American Medical Informatics Association, Phi Beta Kappa, and Society for Academic Emergency Medicine

Disclosure: WebMD Salary Employment

Marjorie Lazoff, MD Editor-in-Chief, Medical Computing Review

Marjorie Lazoff, MD is a member of the following medical societies: Alpha Omega Alpha, American College of Emergency Physicians, American Medical Informatics Association, and Society for Academic Emergency Medicine

Disclosure: Nothing to disclose.

Glenn Lopate, MD Associate Professor, Department of Neurology, Division of Neuromuscular Diseases, Washington University School of Medicine; Director of Neurology Clinic, St Louis ConnectCare; Consulting Staff, Department of Neurology, Barnes-Jewish Hospital

Glenn Lopate, MD is a member of the following medical societies: American Academy of Neurology, American Association of Neuromuscular and Electrodiagnostic Medicine, and Phi Beta Kappa

Disclosure: Baxter Grant/research funds Other; Amgen Grant/research funds None

C Douglas Phillips, MD Director of Head and Neck Imaging, Division of Neuroradiology, New York Presbyterian Hospital, Weill Cornell Medical College

C Douglas Phillips, MD is a member of the following medical societies: American College of Radiology, American Medical Association, American Society of Head and Neck Radiology, American Society of Neuroradiology, Association of University Radiologists, and Radiological Society of North America

Disclosure: Nothing to disclose.

Tarakad S Ramachandran, MBBS, FRCP(C), FACP Professor of Neurology, Clinical Professor of Medicine, Clinical Professor of Family Medicine, Clinical Professor of Neurosurgery, State University of New York Upstate Medical University; Chair, Department of Neurology, Crouse Irving Memorial Hospital

Tarakad S Ramachandran, MBBS, FRCP(C), FACP is a member of the following medical societies: American Academy of Neurology, American Academy of Pain Medicine, American College of Forensic Examiners, American College of International Physicians, American College of Managed Care Medicine, American College of Physicians, American Heart Association, American Stroke Association, Royal College of Physicians, Royal College of Physicians and Surgeons of Canada, Royal College of Surgeons of England, and Royal Society of Medicine

Disclosure: Abbott Labs None None; Teva Marion None None; Boeringer-Ingelheim Honoraria Speaking and teaching

Norman C Reynolds Jr, MD Neurologist, Veterans Affairs Medical Center of Milwaukee; Clinical Professor, Medical College of Wisconsin

Norman C Reynolds Jr, MD is a member of the following medical societies: American Academy of Neurology, Association of Military Surgeons of the US, Movement Disorders Society, Sigma Xi, and Society for Neuroscience

Disclosure: Nothing to disclose.

Robert Stanley Rust Jr, MD, MA Thomas E Worrell Jr Professor of Epileptology and Neurology, Co-Director of FE Dreifuss Child Neurology and Epilepsy Clinics, Director, Child Neurology, University of Virginia School of Medicine; Chair-Elect, Child Neurology Section, American Academy of Neurology

Robert Stanley Rust Jr, MD, MA is a member of the following medical societies: American Academy of Neurology, American Epilepsy Society, American Headache Society, American Neurological Association, Child Neurology Society, International Child Neurology Association, and Society for Pediatric Research

Disclosure: Nothing to disclose.

Manish K Singh, MD Assistant Professor, Department of Neurology, Teaching Faculty for Pain Management and Neurology Residency Program, Hahnemann University Hospital, Drexel College of Medicine; Medical Director, Neurology and Pain Management, Jersey Institute of Neuroscience

Manish K Singh, MD is a member of the following medical societies: American Academy of Neurology, American Academy of Pain Medicine, American Association of Physicians of Indian Origin, American Headache Society, American Medical Association, and American Society of Regional Anesthesia and Pain Medicine

Disclosure: Nothing to disclose.

Niranjan N Singh, MD, DNB Assistant Professor of Neurology, University of Missouri-Columbia School of Medicine

Niranjan N Singh, MD, DNB is a member of the following medical societies: American Academy of Neurology

Disclosure: Nothing to disclose.

Mark S Slabinski, MD, FACEP, FAAEM Vice President, EMP Medical Group

Mark S Slabinski, MD, FACEP, FAAEM is a member of the following medical societies: Alpha Omega Alpha, American Academy of Emergency Medicine, American College of Emergency Physicians, American Medical Association, and Ohio State Medical Association

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James G Smirniotopoulos, MD Professor of Radiology, Neurology, and Biomedical Informatics, Program Director, Diagnostic Imaging Program, Center for Neuroscience and Regenerative Medicine (CNRM), Uniformed Services University of the Health Sciences

James G Smirniotopoulos, MD is a member of the following medical societies: American College of Radiology, American Roentgen Ray Society, American Society of Head and Neck Radiology, American Society of Neuroradiology, American Society of Pediatric Neuroradiology, Association of University Radiologists, and Radiological Society of North America

Disclosure: Nothing to disclose.

Florian P Thomas, MD, MA, PhD, Drmed Director, Spinal Cord Injury Unit, St Louis Veterans Affairs Medical Center; Director, National MS Society Multiple Sclerosis Center; Director, Neuropathy Association Center of Excellence, Professor, Department of Neurology and Psychiatry, Associate Professor, Institute for Molecular Virology, and Department of Molecular Microbiology and Immunology, St Louis University School of Medicine

Florian P Thomas, MD, MA, PhD, Drmed is a member of the following medical societies: American Academy of Neurology, American Neurological Association, American Paraplegia Society, Consortium of Multiple Sclerosis Centers, and National Multiple Sclerosis Society

Disclosure: Nothing to disclose.

Frederick M Vincent Sr, MD Clinical Professor, Department of Neurology and Ophthalmology, Michigan State University Colleges of Human and Osteopathic Medicine

Frederick M Vincent Sr, MD is a member of the following medical societies: Alpha Omega Alpha, American Academy of Neurology, American Association of Neuromuscular and Electrodiagnostic Medicine, American College of Forensic Examiners, American College of Legal Medicine, American College of Physicians, and Michigan State Medical Society

Disclosure: Nothing to disclose.

Amir Vokshoor, MD Staff Neurosurgeon, Department of Neurosurgery, Spine Surgeon, Diagnostic and Interventional Spinal Care, St John's Health Center

Amir Vokshoor, MD is a member of the following medical societies: Alpha Omega Alpha, American Association of Neurological Surgeons, American Medical Association, and North American Spine Society

Disclosure: Nothing to disclose.

Cordia Wan, MD Adult Neurologist, Kaiser Permanente Hawaii, Kaiser Permanente Southern California

Cordia Wan, MD is a member of the following medical societies: American Academy of Neurology

Disclosure: Nothing to disclose.

Eric L Weiss, MD, DTM&H Medical Director, Office of Service Continuity and Disaster Planning, Fellowship Director, Stanford University Medical Center Disaster Medicine Fellowship, Chairman, SUMC and LPCH Bioterrorism and Emergency Preparedness Task Force, Clinical Associate Progressor, Department of Surgery (Emergency Medicine), Stanford University Medical Center

Eric L Weiss, MD, DTM&H is a member of the following medical societies: American College of Emergency Physicians, American College of Occupational and Environmental Medicine, American Medical Association, American Society of Tropical Medicine and Hygiene, Physicians for Social Responsibility, Southeastern Surgical Congress, Southern Association for Oncology, Southern Clinical Neurological Society, and Wilderness Medical Society

Disclosure: Nothing to disclose.

Lawrence A Zumo, MD Neurologist, Private Practice

Lawrence A Zumo, MD is a member of the following medical societies: American Academy of Neurology, American College of Physicians, American Medical Association, and Southern Medical Association

Disclosure: Nothing to disclose.

Specialty Editor Board

Joseph Richard Masci, MD Professor of Medicine, Professor of Preventive Medicine, Mount Sinai School of Medicine; Director of Medicine, Elmhurst Hospital Center

Joseph Richard Masci, MD is a member of the following medical societies: Alpha Omega Alpha, American College of Physicians, Association of Professors of Medicine, and Royal Society of Medicine

Disclosure: Nothing to disclose.

Francisco Talavera, PharmD, PhD Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Medscape Salary Employment

John W King, MD Professor of Medicine, Chief, Section of Infectious Diseases, Director, Viral Therapeutics Clinics for Hepatitis, Louisiana State University Health Sciences Center; Consultant in Infectious Diseases, Overton Brooks Veterans Affairs Medical Center

John W King, MD is a member of the following medical societies: American Association for the Advancement of Science, American College of Physicians, American Federation for Medical Research, American Society for Microbiology, Association of Subspecialty Professors, Infectious Diseases Society of America, and Sigma Xi

Disclosure: emedicine $50.00 Author of chapter; MERCK None Other

Karen L Roos, MD John and Nancy Nelson Professor of Neurology, Professor of Neurological Surgery, Department of Neurology, Indiana University School of Medicine

Karen L Roos, MD is a member of the following medical societies: American Academy of Neurology and American Neurological Association

Disclosure: Nothing to disclose.

Chief Editor

Burke A Cunha, MD Professor of Medicine, State University of New York School of Medicine at Stony Brook; Chief, Infectious Disease Division, Winthrop-University Hospital

Burke A Cunha, MD is a member of the following medical societies: American College of Chest Physicians, American College of Physicians, and Infectious Diseases Society of America

Disclosure: Nothing to disclose.

Additional Contributors

The authors and editors of eMedicine gratefully acknowledge the contributions of previous authors Sidney E Croul, MD, Timothy Brannan, MD, Pieter R Kark, MD, Suur Biliciler, MD, Prem C Shukla, MD, and Uma Iyer, MD, to the development and writing of the source articles.

References

Mann K, Jackson MA. Meningitis. Pediatr Rev. Dec 2008;29(12):417-29; quiz 430. [Medline].
Ginsberg L, Kidd D. Chronic and recurrent meningitis. Pract Neurol. Dec 2008;8(6):348-61. [Medline].
Berkhout B. Infectious diseases of the nervous system: pathogenesis and worldwide impact. IDrugs. Nov 2008;11(11):791-5. [Medline].
Nkoumou MO, Clevenbergh P, Betha G, Kombila M. Bacterial meningitis in HIV positive compared to HIV negative patients in an internal medicine ward of Librevile, Gabon. . Int Conf AIDS: International Conference on AIDS. Jul 7-12 2002;abstract no. ThPeB7368.
Scheld WM, Koedel U, Nathan B, Pfister HW. Pathophysiology of bacterial meningitis: mechanism(s) of neuronal injury. J Infect Dis. Dec 1 2002;186 Suppl 2:S225-33. [Medline].
Thigpen, M, Rosenstein, NE, Whitney, CG. Bacterial meningitis in the United States --1998-2003. Presented at the 43rd Annual Meeting of the Infectious Diseases Society of America, San Francisco, CA. October 2005;65.
Thigpen MC, Whitney CG, Messonnier NE, et al. Bacterial meningitis in the United States, 1998-2007. N Engl J Med. May 26 2011;364(21):2016-25. [Medline].
van de Beek D, de Gans J, Tunkel AR, Wijdicks EF. Community-acquired bacterial meningitis in adults. N Engl J Med. Jan 5 2006;354(1):44-53. [Medline].
Moses S. Meningitis: acute bacterial meningitis. Accessed February 8, 2011. Available at http://www.fpnotebook.com/neuro/ID/Mngts.htm.
Worsoe L, Caye-Thomasen P, Brandt CT, Thomsen J, Ostergaard C. Factors associated with the occurrence of hearing loss after pneumococcal meningitis. Clin Infect Dis. Oct 15 2010;51(8):917-24. [Medline].
[Best Evidence] Dubos F, Korczowski B, Aygun DA, Martinot A, Prat C, Galetto-Lacour A, et al. Serum procalcitonin level and other biological markers to distinguish between bacterial and aseptic meningitis in children: a European multicenter case cohort study. Arch Pediatr Adolesc Med. Dec 2008;162(12):1157-63. [Medline].
Gilbert DN, Moellering RC Jr, Sande MA. Antimicrobial Therapy. In: Sanford Guide to Antimicrobial Therapy. 33^rd ed. March 15, 2003.
van de Beek D, de Gans J, McIntyre P, Prasad K. Steroids in adults with acute bacterial meningitis: a systematic review. Lancet Infect Dis. Mar 2004;4(3):139-43. [Medline].
van de Beek D, de Gans J. Dexamethasone and pneumococcal meningitis. Ann Intern Med. Aug 17 2004;141(4):327. [Medline].
Peltola H, Roine I. Improving the outcomes in children with bacterial meningitis. Curr Opin Infect Dis. Jun 2009;22(3):250-5. [Medline].
[Best Evidence] Sloan D, Dlamini S, Paul N, Dedicoat M. Treatment of acute cryptococcal meningitis in HIV infected adults, with an emphasis on resource-limited settings. Cochrane Database Syst Rev. Oct 8 2008;CD005647. [Medline].
Report from the Advisory Committee on Immunization Practices (ACIP): decision not to recommend routine vaccination of all children aged 2-10 years with quadrivalent meningococcal conjugate vaccine (MCV4). MMWR Morb Mortal Wkly Rep. May 2 2008;57(17):462-5. [Medline].
[Guideline] Centers for Disease Control and Prevention (CDC). Updated recommendations for use of meningococcal conjugate vaccines --- Advisory Committee on Immunization Practices (ACIP), 2010. MMWR Morb Mortal Wkly Rep. Jan 28 2011;60(3):72-6. [Medline]. [Full Text].
Seupaul RA. Evidence-based emergency medicine/rational clinical examination abstract. How do I perform a lumbar puncture and analyze the results to diagnose bacterial meningitis?. Ann Emerg Med. Jul 2007;50(1):85-7. [Medline].

Pneumococcal meningitis in a patient with alcoholism. Courtesy of the CDC/Dr. Edwin P. Ewing, Jr.

Acute bacterial meningitis. This axial nonenhanced computed tomography scan shows mild ventriculomegaly and sulcal effacement

Acute bacterial meningitis. This axial T2-weighted magnetic resonance image shows only mild ventriculomegaly.

Acute bacterial meningitis. This contrast-enhanced, axial T1-weighted magnetic resonance image shows leptomeningeal enhancement (arrows).

Chronic mastoiditis and epidural empyema in a patient with bacterial meningitis. This axial computed tomography scan shows sclerosis of the temporal bone (chronic mastoiditis), an adjacent epidural empyema with marked dural enhancement (arrow), and the absence of left mastoid air.

Subdural empyema and arterial infarct in a patient with bacterial meningitis. This contrast-enhanced axial computed tomography scan shows left-sided parenchymal hypoattenuation in the middle cerebral artery territory, with marked herniation and a prominent subdural empyema.

Table 1. Infectious Agents Causing Aseptic Meningitis Syndrome

Category	Agent
Bacteria	Partially-treated bacterial meningitis L monocytogenes Brucella species Rickettsia rickettsii Ehrlichia species Mycoplasma pneumoniae Borrelia burgdorferi Treponema pallidum Leptospira species Mycobacterium tuberculosis Nocardia species
Parasites	N fowleri Acanthamoeba species Balamuthia species Angiostrongylus cantonensis G spinigerum Baylisascaris procyonis S stercoralis Taenia solium (cysticercosis)
Fungi	Cryptococcus neoformans C immitis Blastomyces dermatitidis H capsulatum Candida species Aspergillus species
Viruses	Enterovirus Poliovirus Echovirus Coxsackievirus A Coxsackievirus B Enterovirus 68-71
	Herpesvirus HSV-1 and HSV-2 Varicella-zoster virus EBV CMV HHV*-6 HHV-7
	Paramyxovirus Mumps virus Measles virus
	Togavirus Rubella virus
	Flavivirus Japanese encephalitis virus St. Louis encephalitis virus
	Bunyavirus California encephalitis virus La Crosse encephalitis virus
	Alphavirus Eastern equine encephalitis virus Western equine encephalitis virus Venezuelan encephalitis virus
	Reovirus Colorado tick fever virus
	Arenavirus LCM virus**
	Rhabdovirus Rabies virus
	Retrovirus HIV***
Human herpes virus Lymphocytic choriomeningitis **Human immunodeficiency virus

Table 2. Causes of Chronic Meningitis

Category	Agent
Bacteria	M tuberculosis B burgdorferi T pallidum Brucella species Francisella tularensis Nocardia species Actinomyces species
Fungi	C neoformans C immitis B dermatitidis H capsulatum Candida albicans Aspergillus species Sporothrix schenckii
Parasites	Acanthamoeba species N fowleri Angiostrongylus cantonensis G spinigerum B procyonis Schistosoma species S stercoralis Echinococcus granulosus

Table 3. Changing Epidemiology of Acute Bacterial Meningitis in the United States*

Bacteria	1978-1981	1986	1995	1998-2007
H influenzae	48%	45%	7%	6.7%
Listeria monocytogenes	2%	3%	8%	3.4%
N meningitidis	20%	14%	25%	13.9%
S agalactiae	3%	6%	12%	18.1%
S pneumoniae	13%	18%	47%	58%
*Nosocomial meningitis is not included. These data include only the 5 major meningeal pathogens.

Table 4. The Most Common Bacterial Pathogens Based on Age and Predisposing Risks

Risk and/or Predisposing Factor	Bacterial Pathogen
Age 0-4 weeks	Streptococcus agalactiae (group B streptococci) E coli K1 Listeria monocytogenes
Age 4-12 weeks	S agalactiae E coli H influenzae S pneumoniae N meningitidis
Age 3 months to 18 years	N meningitidis S pneumoniae H influenzae
Age 18-50 years	S pneumoniae N meningitidis H influenzae
Age older than 50 years	S pneumoniae N meningitidis L monocytogenes Aerobic gram-negative bacilli
Immunocompromised state	S pneumoniae N meningitidis L monocytogenes Aerobic gram-negative bacilli
Intracranial manipulation, including neurosurgery	Staphylococcus aureus Coagulase-negative staphylococci Aerobic gram-negative bacilli, including P aeruginosa
Basilar skull fracture	S pneumoniae H influenzae Group A streptococci
CSF shunts	Coagulase-negative staphylococci S aureus Aerobic gram-negative bacilli Propionibacterium acnes

Table 5. CSF Picture of Meningitis According to Etiologic Agent

Agent	Opening Pressure	WBC count per µL	Glucose (mg/dL)	Protein (mg/dL)	Microbiology
Bacterial meningitis	200-300	100-5000; >80% PMNs*	< 40	>100	Specific pathogen demonstrated in 60% of Gram stains and 80% of cultures
Viral meningitis	90-200	10-300; lymphocytes	Normal, reduced in LCM and mumps	Normal but may be slightly elevated	Viral isolation, PCR^† assays
Tuberculous meningitis	180-300	100-500; lymphocytes	Reduced, < 40	Elevated, >100	Acid-fast bacillus stain, culture, PCR
Cryptococcal meningitis	180-300	10-200; lymphocytes	Reduced	50-200	India ink, cryptococcal antigen, culture
Aseptic meningitis	90-200	10-300; lymphocytes	Normal	Normal but may be slightly elevated	Negative findings on workup
Normal values	80-200	0-5; lymphocytes	50-75	15-40	Negative findings on workup
*Polymorphonuclear lymphocytes †Polymerase chain reaction

Table 6. Comparison of CSF Findings by Type of Organism

	Bacterial Meningitis	Viral Meningitis*	Fungal Meningitis**
Pressure 5-15 cm H₂ O	Increased	Normal or mildly increased	Normal or mildly increased in TB. May be increased in fungal. AIDS patients with cryptococcal meningitis have increased risk of blindness, death unless maintained at < 30 cm.
Cell count preterm: 0-25 term: 0-22 >6 months: 0-5 mononuclear cells/mm³	No cell count result can exclude bacterial meningitis. Typically thousands of PMNs, but may be less dramatic or even normal (classically, in very early meningococcal meningitis and in extremely ill neonates). Lymphocytosis with normal CSF chemistries seen in 15-25%, especially when cell counts < 1000 or if partially treated. Approximately 90% of patients with ventriculoperitoneal shunts have CSF WBC count >100 cells/mm³ are infected; CSF glucose usually normal, and organisms are less pathogenic. Cell count and chemistries normalize slowly (over days) with antibiotics.	Usually < 500 cells, nearly 100% mononuclear. Up to 48 hours, significant PMN pleocytosis may be indistinguishable from early bacterial meningitis; this is particularly true with eastern equine encephalitis. Presence of nontraumatic RBCs in 80% of HSV meningoencephalitis, although 10% have normal CSF results	Hundreds of mononuclear cells
Micro no organisms	Gram stain 80% sensitive. Inadequate decolorization may mistake H influenzae for gram-positive cocci. Pretreatment with antibiotics may affect stain uptake, causing gram-positive organisms to appear gram negative and decrease culture yield on average 20%.	No organism	India ink 80-90% sensitive for fungi; AFB stain 40% sensitive for TB (increase yield by staining supernate from at least 5 cc CSF)
Glucose euglycemia: >50% serum hyperglycemia: >30% serum wait 4 h after glucose load	Decreased	Normal	Sometimes decreased. Aside from fulminant bacterial meningitis, the lowest levels of CSF glucose are seen in TB, primary amebic meningoencephalitis, neurocysticercosis
Protein preterm: 65-150 term: 20-170 >6 months: 15-45 mg/dL	Usually >150, may be >1000	Mildly increased	Increased; >1000 with relatively benign clinical presentation suggestive of fungal disease
Some bacteria (eg, Mycoplasma, Listeria, Leptospira* species, Borrelia burgdorferi [Lyme], spirochetes) produce spinal fluid alterations that resemble the viral profile. An aseptic profile also is typical of partially treated bacterial infections (more than 33% of patients have received antimicrobial treatment, especially children) and the 2 most common causes of encephalitis — the potentially curable HSV and arboviruses. **In contrast, tuberculous meningitis and parasites resemble the fungal profile more closely.

Table 7. Recommended Empiric Antibiotics According to Predisposing Factors for Patients With Suspected Bacterial Meningitis

Predisposing Feature	Antibiotic(s)
Age 0-4 weeks	Ampicillin plus cefotaxime or an aminoglycoside
Age 1-3 months	Ampicillin plus cefotaxime plus vancomycin*
Age 3 months to 50 years	Ceftriaxone or cefotaxime plus vancomycin*
Older than 50 years	Ampicillin plus ceftriaxone or cefotaxime plus vancomycin*
Impaired cellular immunity	Ampicillin plus ceftazidime plus vancomycin*
Neurosurgery, head trauma, or CSF shunt	Vancomycin plus ceftazidime
*Vancomycin is added empirically to the initial regimen if the presence of penicillin-resistant S pneumoniae is suspected or if a high incidence of resistance is reported in the community.

Table 8. Recommended Empiric Antibiotics for Patients With Suspected Bacterial Meningitis and Known CSF Gram Stain Results

*Gram Stain Morphology*	*Antibiotic(s)*
Gram-positive cocci	Vancomycin plus ceftriaxone or cefotaxime
Gram-negative cocci	Penicillin G*
Gram-positive bacilli	Ampicillin plus an aminoglycoside
Gram-negative bacilli	Broad-spectrum cephalosporin^† plus an aminoglycoside
*Use ceftriaxone if penicillin-resistant N meningitidis occurs in the community. †Ceftriaxone is preferred. Ceftazidime is used when Pseudomonas infection is likely (eg, neurosurgical procedures).

Table 9. Specific Antibiotics and Duration of Therapy for Patients With Acute Bacterial Meningitis

Bacteria	Susceptibility	Antibiotic(s)	Duration (Days)
S pneumoniae	Penicillin MIC < 0.1 mg/L	Penicillin G	10-14
	MIC 0.1-1 mg/L	Ceftriaxone or cefotaxime
	MIC >2 mg/L	Ceftriaxone or cefotaxime
	Ceftriaxone MIC >0.5 mg/L	Ceftriaxone or cefotaxime plus vancomycin or rifampin
H influenzae	Beta-lactamase-negative	Ampicillin	7
H influenzae	Beta-lactamase-positive	Ceftriaxone or cefotaxime	7
N meningitidis	...	Penicillin G or ampicillin	7
L monocytogenes	...	Ampicillin or penicillin G plus an aminoglycoside	14-21
S agalactiae	...	Penicillin G plus an aminoglycoside, if warranted	14-21
Enterobacteriaceae	...	Ceftriaxone or cefotaxime plus an aminoglycoside	21
P aeruginosa	...	Ceftazidime plus an aminoglycoside	21

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