II. Epidemiology

  1. Bacterial Meningitis Annual Incidence: 0.69 per 100,000 persons (in 2007, U.S.)
    1. Prior to Vaccination, rates were 1 to 1.5 per 100,000 persons

III. Pathophysiology

  1. Inefficient Phagocytosis of pathogen
  2. Cerebrospinal Fluid deficient in immune factors
    1. Specific Antibody
    2. Functional complement

IV. Risk Factors: Adults

  1. Recent Otitis Media or Bacterial Sinusitis (25% of cases)
  2. Pneumonia (12% of cases)
  3. Immunocompromised state (16%)

V. Causes: Bacterial

  1. Older adults over age 60 years
    1. Streptococcus Pneumoniae
    2. Escherichia coli
    3. KlebsiellaPneumoniae
    4. Streptococcus agalactiae (Group B Streptococcus)
    5. Listeria monocytogenes (more common than in other age groups)
  2. Adults
    1. Streptococcus Pneumoniae (30-50%)
    2. Neisseria Meningitidis (10-35%)
    3. Staphylococci (5-15%)
    4. HaemophilusInfluenzae (1-3%)
    5. Gram Negative Bacilli (1-10%)
    6. Streptococcus species
    7. Listeria monocytogenes (esp. immunosuppressed, pregnancy)
  3. Children or Infants
    1. Streptococcus Pneumoniae (10-20%)
    2. Neisseria Meningitidis (25-40%)
    3. HaemophilusInfluenzae (40-60%)
      1. Markedly reduced with Immunizations (rare now in U.S.)
  4. Neonates (highest rates among any age group, 40 cases per 100,000)
    1. Group B Streptococcus (49%)
    2. Escherichia coli (18%)
    3. Listeria monocytogenes (7%)
    4. Non-Group B Streptococcus

VI. Symptoms

  1. General
    1. Fulminant onset <24 hours (25%)
    2. Respiratory illness precedes onset by <7 days (50%)
    3. Nearly half of patients present with Bacterial Meningitis in first 24 hours (contrast with days for Aseptic Meningitis)
  2. Presentation in Adults and Older Children
    1. Classic Triad (approaches 85% in some studies)
      1. Headache (87%)
      2. Nuchal Rigidity or Stiff Neck (83%)
      3. Fever (77%)
    2. Classic triad symptoms and impaired consciousness
      1. Virtually all Bacterial Meningitis patients have one of these symptoms
      2. Two of four symptoms present in 95% of patients
    3. Other Presenting Symptoms
      1. Nausea (74%)
      2. Altered Level of Consciousness (69%)
      3. Vomiting (35%)
      4. Focal neurologic deficit (29%)
      5. Seizures (5%)
      6. Lethargy
      7. Irritability
      8. Confusion
      9. Rash (26%)
  3. Newborns and Infants
    1. Presentation <1 month is subtle (e.g. Vomiting, lethargy, irritability)
    2. Temperature Instability (Hypothermia or Fever)
      1. Fever in only 60% of Meningitis cases <1 month old
    3. NO Nuchal Rigidity
    4. Listlessness
    5. Lethargy
    6. Irritability
    7. High pitched crying
    8. Refusal to eat or poor feeding
    9. Weak sucking response
    10. Vomiting
    11. Diarrhea
    12. Respiratory distress
    13. Bulging Fontanelle (late sign in 1/3 neonates)
    14. Seizures (40%)
  4. Older adults
    1. Altered Mental Status (84%)
    2. Focal neurologic deficits (46%)
    3. Less common to have Headache (60-77%), Nuchal Rigidity (31%)

VII. Signs

  1. Meningeal Irritation (50% of adult patients)
    1. Recent studies suggest low efficacy
      1. See Meningeal Irritation for specific studies
      2. Do not rely on these signs to diagnose Meningitis
      3. Lumbar Puncture is critical if higher level of suspicion regardless of Meningeal Irritation findings
    2. Nuchal Rigidity
      1. Unreliable in under age 18 months due to neck musculature not fully developed
    3. Spinal Rigidity
    4. Tests with high Test Specificity (but poor Test Sensitivity)
      1. Kernig's Sign
        1. Hip flexed to 90 degrees, and patient unable to extend knee due to hamstring pain
      2. Brudzinski's Sign
        1. Passive neck flexion results in hip flexion
  2. Skin Rash Causes
    1. Meningococcal Meningitis (present in 65% of Meningococcal Meningitis, typically Petechiae)
    2. HaemophilusInfluenzae
    3. Pneumococcal Meningitis
    4. Echovirus type 9
    5. Staphylococcus aureus
  3. Other Neurologic Signs (more common in Pneumococcal Meningitis)
    1. Cranial Nerve Palsies
    2. Altered Level of Consciousness (69%)
    3. Focal Neurologic Signs (10-20%)
    4. Seizures (5%)
    5. Papilledema (3%)
  4. Atypical presentations (classic signs often absent in these groups)
    1. Age over 65 may present with Seizures or Hemiparesis
    2. Young children may present with lethargy, irritability or Seizures

VIII. Differential Diagnosis: Nuchal Rigidity

IX. Differential Diagnosis: CNS Process

  1. Meningitis
    1. Bacterial Meningitis (13.9%)
    2. Aseptic Meningitis
      1. Viral Meningitis (most common form of Meningitis)
        1. Enterovirus Meningitis (50.9% of all Meningitis cases in adults)
        2. Herpes Simplex Virus Meningitis (8.3% of all Meningitis cases in adults)
        3. Arbovirus Meningitis (1.1% of all Meningitis cases in adults)
      2. Parasitic Meningitis
      3. Fungal Meningitis (2.7% of all Meningitis cases)
      4. Tuberculous Meningitis
      5. Drug-Induced Meningitis (e.g. NSAIDs, trimethoprim-sulfamethoxazole)
      6. Benign Recurrent Lymphocytic Meningitis
      7. Neoplastic Meningitis
      8. Leptomeningeal Carcinomatosis
  2. Encephalitis
    1. Viral Encephalitis
    2. HSV Encephalitis
    3. NMDA Ecephalitis
    4. West Nile Virus Encephalitis
  3. Other CNS Infection
    1. See Neurologic Manifestations of HIV
    2. Intracranial Abscess
    3. Lyme Disease (Neuroborreliosis)
    4. Ehrlichiosis
    5. Neurosyphilis
  4. Rheumatologic Conditions or Vasculitis
    1. Systemic Lupus Erythematosus
    2. Neurosarcoidosis
    3. Behcet Syndrome

XI. Diagnosis

  1. Lumbar Puncture
    1. See evaluation for LP indications (do not hesitate to obtain when clinical suspicion dictates)
    2. See Labs below
  2. Consider CT Head prior to Lumbar Puncture
    1. See Lumbar Puncture for CT Head indications (to rule out CNS mass at risk for Brainstem Herniation)
    2. However, do not delay empiric antibiotics while awaiting CT Head, Lumbar Puncture
    3. Obtain Blood Cultures immediately and then administer empiric antibiotics
      1. Even before Head CT and Lumbar Puncture completed

XII. Labs

  1. CSF Exam consistent with Bacterial Meningitis (everything increased except the Glucose)
    1. Precautions
      1. CSF may be atypical despite Bacterial Meningitis in Immunocompromised, older, Listeria or partially treated cases
      2. Cell type (e.g. Pleocytosis) cannot differentiate from Aseptic Meningitis in age <18 years old
      3. Use age-adjusted cut-offs for CSF Cell Counts in infants
    2. See Nigrovic Clinical Decision Rule
    3. CSF Leukocytes
      1. Over 500 (mean 5k-20k) with >80% Neutrophils
      2. Over 50k suggests Brain Abscess
      3. May be 100 (with only 50% Neutrophils) in Listeria infection
    4. CSF Opening Pressure
      1. Exceeds 180 mm H2O
    5. CSF Protein
      1. CSF Protein >100 mg/dl (may be normal with listeria)
      2. Range: 100-500 mg/dl (typically >250 mg/dl in Bacterial Meningitis)
    6. CSF Glucose
      1. Less than 40% of Blood Glucose (or less than 40 mg/dl)
    7. CSF Gram Stain Positive
      1. Test Sensitivity 75% (untreated)
    8. CSF Culture Positive
      1. Test Sensitivity 70-80%
    9. CSF Latex Agglutination (replaced with PCR testing)
      1. Rapid test for common Bacteria (high Test Specificity, BUT poor sensitivity)
      2. Does not rule-out Bacterial Meningitis
    10. CSF Polymerase Chain Reaction (PCR)
      1. Available for enterovirus, West Nile Virus, HSV, VZV, EBV, CMV, Tuberculosis, Neurosyphilis
  2. Blood Culture (40-60% sensitivity)
    1. HaemophilusInfluenzae (uncommon now due to Vaccine)
    2. Streptococcus Pneumoniae
    3. Neisseria Meningitidis
  3. Complete Blood Count
    1. Peripheral White Blood Cell Count does not distinguish Bacterial Meningitis from Aseptic Meningitis
    2. A normal White Blood Cell Count does not rule-out Bacterial Meningitis (esp. in young children)
  4. Urine Culture
    1. Indicated in infants
  5. Other markers that may be useful in differentiating Bacterial Meningitis
    1. C-Reactive Protein
      1. High Negative Predictive Value (but not useful if positive)
      2. Gerdes (1998) Scand J Clin Lab Invest 58(5): 383-93 [PubMed]
    2. Procalcitonin
      1. Test Sensitivity 96%, Test Specificity >89% for Bacterial Meningitis
      2. Henry (2016) Clin Pediatr 55(8): 749-64 [PubMed]
      3. Vikse (2015) Int J Infect Dis 38:78-76 [PubMed]
    3. CSF Lactate
      1. Test Sensitivity >93 and Test Specificity >92% for Bacterial Meningitis
      2. Sakushima (2011) J Infect 62(4): 255-62 [PubMed]

XIII. Imaging

  1. Consider head imaging
  2. See Lumbar Puncture for indications prior to LP

XIV. Management

XV. Complications

  1. Acute
    1. Increased Intracranial Pressure
      1. See Bacterial Meningitis Management
    2. Seizures (20-30% of children with Bacterial Meningitis)
      1. Evaluate for Hypoglycemia and Hyponatremia
      2. See Status Epilepticus
      3. Consider anticonvulsants for prolonged or recurrent Seizures
    3. Syndrome of Inappropriate Antidiuretic Hormone Secretion (SIADH)
    4. Subdural Effusion (15-40% of children with Bacterial Meningitis)
      1. Risk factors include younger age, Leukopenia, higher CSF Protein
      2. Consider Subdural Empyema in clinical deterioration
  2. Chronic: Children
    1. Cognitive Impairment: 30 to 45%
    2. Hearing Loss: 6.7 to 31% reversible (2-7% permanent Deafness)
    3. Spasticity or paresis: 3.5%
    4. Seizure Disorder: 1.8 to 4.2%
    5. Mortality: 0.3 to 3.8%
  3. Chronic: adults
    1. Focal neurologic deficits: 37-50% (Hemiparesis in 4-6%)
    2. Cardiorespiratory failure: 29-38%
    3. Seizure Disorder: 15-24%
    4. Mortality: 15-21%
    5. Hearing Loss: 14-69%

XVI. Prevention

  1. Postexposure Prophylaxis
    1. See Bacterial Meningitis Postexposure Prophylaxis
    2. Indicated only in Meningococcal Meningitis and Haemophilus influenza Meningitis
      1. Not indicated in other Bacterial Meningitis exposure
  2. Primary Prevention
    1. Meningococcal Vaccine
    2. HaemophilusInfluenzae Vaccine
    3. Adult Pneumococcal Vaccine
      1. Decreases Bacterial Meningitis risk by 50%

XVII. Prognosis

  1. Overall mortality: 15.6%
  2. Meningococcal Meningitis
    1. Meningococcemia: Prognosis poor (20-30% fatality)
    2. Meningitis alone: Better prognosis (4-5% case fatality)
  3. Pneumococcal Meningitis (highest morbidity and mortality)
    1. Case fatality rate 10% in children (30% in adults)
    2. Morbidity >30% (Hearing Loss common in children)
    3. Worse prognosis with Penicillin-resistant strains
  4. Tuberculous Meningitis
    1. Mortality rate: 19.3%
    2. Neurologic sequelae: 53.9%
    3. Chiang (2014) Lancet Infect Dis 14(10): 947-57 [PubMed]
  5. Poor prognostic factors
    1. Low Glasgow Coma Scale
    2. Systemic compromise (e.g. Tachycardia, low CSF white count, positive Blood Cultures)
    3. Abnormal Neurologic Exam
    4. Alcoholism
    5. Pneumococcal infection
    6. Male gender

XVIII. Reference

  1. Fuchs and Yamamoto (2012) APLS, Jones and Bartlett, Burlington, p. 175-80
  2. Gilbert (1998) Sanford Guide to Antimicrobial Therapy
  3. Wilson (1991) Harrison's Internal Medicine, p. 651-2
  4. Choi (2001) Clin Infect Dis 33:1380-5 [PubMed]
  5. Mount (2017) Am Fam Physician 96(5): 314-22 [PubMed]
  6. Tunkel (1997) Am Fam Physician 56(5):1355-62 [PubMed]

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Related Studies

Ontology: Meningitis (C0025289)

Definition (MSH) Inflammation of the coverings of the brain and/or spinal cord, which consist of the PIA MATER; ARACHNOID; and DURA MATER. Infections (viral, bacterial, and fungal) are the most common causes of this condition, but subarachnoid hemorrhage (HEMORRHAGES, SUBARACHNOID), chemical irritation (chemical MENINGITIS), granulomatous conditions, neoplastic conditions (CARCINOMATOUS MENINGITIS), and other inflammatory conditions may produce this syndrome. (From Joynt, Clinical Neurology, 1994, Ch24, p6)
Definition (CHV) brain infection
Definition (CHV) brain infection
Definition (MEDLINEPLUS)

Meningitis is inflammation of the thin tissue that surrounds the brain and spinal cord, called the meninges. There are several types of meningitis. The most common is viral meningitis, which you get when a virus enters the body through the nose or mouth and travels to the brain. Bacterial meningitis is rare, but can be deadly. It usually starts with bacteria that cause a cold-like infection. It can block blood vessels in the brain and lead to stroke and brain damage. It can also harm other organs. Pneumococcal infections and meningococcal infections can cause bacterial meningitis.

Anyone can get meningitis, but it is more common in people whose bodies have trouble fighting infections. Meningitis can progress rapidly. You should seek medical care quickly if you have

  • A sudden fever
  • A severe headache
  • A stiff neck

Early treatment can help prevent serious problems, including death. Vaccines can prevent some of the bacterial infections that cause meningitis. Parents of adolescents and students living in college dorms should talk to a doctor about the vaccination.

NIH: National Institute of Neurological Disorders and Stroke

Definition (NCI_NCI-GLOSS) Inflammation of the meninges (three thin layers of tissue that cover and protect the brain and spinal cord). Meningitis is usually caused by a bacterial or viral infection, but sometimes is caused by cancer, drug allergies, or inflammatory diseases.
Definition (NCI_CTCAE) A disorder characterized by acute inflammation of the meninges of the brain and/or spinal cord.
Definition (NCI) A disorder characterized by acute inflammation of the meninges of the brain and/or spinal cord.
Definition (CSP) inflammation of the meninges.
Concepts Disease or Syndrome (T047)
MSH D008581
ICD9 322.9, 322
ICD10 G03.9 , G03
SnomedCT 192681009, 154983000, 192678004, 7180009
LNC LP20756-0, LA7454-7
English Meningitides, Meningitis, Meningitis of unspecified cause, Meningitis - unspecified cause, Meningitis, unspecified, Unspecified meningitis, meningitis, meningitis (diagnosis), Meningitis NOS, meningitis NOS, Meningitis [Disease/Finding], meningitides, Unspecified meningitis (disorder), Meningitis of unspecified cause (disorder), Inflammation of meninges, MENINGITIS, Meningitis (disorder), infection; brain, membranes, Meningitis, NOS
French MENINGITE, Méningite, non précisée, Méningite de cause non précisée, Méningite SAI, Méningite
Portuguese MENINGITE, Meningite NE, Meningite de causa NE, Meningite
Spanish MENINGITIS, Meningitis de causa no especificada, Meningitis no especificada, Meningitis NEOM, meningitis de causa no especificada (trastorno), meningitis no especificada, meningitis de causa no especificada, meningitis no especificada (trastorno), meningitis (trastorno), meningitis, Meningitis
Dutch meningitis door niet-gespecificeerde oorzaak, meningitis, niet-gespecificeerd, meningitis NAO, infectie; hersenen, vliezen, Meningitis, niet gespecificeerd, meningitis, Meningitis
German Meningitis NNB, Meningitis, unspezifisch, Meningitis unspezifischer Ursache, HIRNHAUTENTZUENDUNG, Meningitis, nicht naeher bezeichnet, Meningitis, Hirnhautentzündung
Italian Meningite NAS, Meningite da causa non specificata, Meningite, non specificata, Meningite
Japanese 髄膜炎NOS, 髄膜炎、詳細不明, 原因不明の髄膜炎, 髄膜炎, ズイマクエンNOS, ズイマクエンショウサイフメイ, ズイマクエン, ゲンインフメイノズイマクエン
Swedish Hjärnhinneinflammation
Czech meningitida, zánět mozkových blan, Meningitida, Meningitida, blíže neurčená, Meningitida NOS, Meningitida blíže neurčeného původu
Finnish Aivokalvotulehdus
Korean 상세불명의 수막염
Polish Zapalenie opon
Hungarian meningitis k.m.n., Meningitis, nem meghatározott, Nem meghatározott etiológiájú meningitis, meningitis
Norwegian Hjernehinnebetennelse, Meningitt

Ontology: Meningitis, Bacterial (C0085437)

Definition (MSH) Bacterial infections of the leptomeninges and subarachnoid space, frequently involving the cerebral cortex, cranial nerves, cerebral blood vessels, spinal cord, and nerve roots.
Definition (CSP) bacterial infections of the leptomeninges and subarachnoid space, frequently involving the cerebral cortex, cranial nerves, cerebral blood vessels, spinal cord and nerve roots; causative organism varies with age and clinical status (eg, postoperative, immunodeficient, posttraumatic states); clinical manifestations include the acute onset of fever, stiff neck, altered mentation, seizures, and focal neurologic deficits; death may occur within 24 hours of disease onset; pathologic features include a purulent exudate in the subarachnoid space, and diffuse inflammation of neural and vascular structures.
Concepts Disease or Syndrome (T047)
MSH D016920
ICD9 320.9, 320
ICD10 G00.9 , G00
SnomedCT 192662001, 267680008, 154984006, 95883001
English Bacterial Meningitides, Bacterial Meningitis, Meningitides, Bacterial, Meningitis, Bacterial, Meningitis due to unspecified bacterium, Bacterial meningitis, unspecified, MENINGITIS BACTERIAL, MENINGITIS BACT, BACT MENINGITIDES, BACT MENINGITIS, MENINGITIDES BACT, bacterial meningitis, bacterial meningitis (diagnosis), Meningitis bacterial NOS, Bacterial meningitis NOS, Meningitis, Bacterial [Disease/Finding], Meningitis;bacterial, bacterial meningitides, Bacterial meningitis NOS (disorder), Meningitis bacterial, Bacterial meningitis, BM - Bacterial meningitis, Bacterial meningitis (disorder), bacterial; meningitis, meningitis; bacterial, Bacterial meningitis, NOS, Meningitis, bacterial NOS
Portuguese MENINGITE BACTERIANA, Meningite bacteriana NE, Meningite por bactéria NE, Meningites Bacterianas, Meningite Bacteriana, Meningite por Bactéria, Meningites por Bactérias, Meningite por Bactérias, Meningite bacteriana
Dutch meningitis bacterieel NAO, meningitis door niet-gespecificeerde bacterie, bacteriële meningitis, bacterieel; meningitis, meningitis; bacterieel, Bacteriële meningitis, niet gespecificeerd, hersenvliesontsteking bacterieel, Bacteriële meningitis, Meningitis, bacteriële
French Méningite bactérienne SAI, Méningite due à une bactérie non précisée, MENINGITE BACTERIENNE, Méningite bactérienne
German Meningitis bakteriell NNB, Meningitis infolge einer unspezifischen Bakterie, Bakterielle Meningitis, nicht naeher bezeichnet, MENINGITIS BAKTERIELL, bakterielle Meningitis, Meningitis, bakterielle, Bakterielle Meningitis
Italian Meningite batterica NAS, Meningite da batteri non specificati, Meningite batterica
Spanish Meningitis por bacterias, Meningitis bacteriana NEOM, Meningitis por bacterias no especificadas, Meningitis Bacterianas, Meningitis Bacteriana, meningitis bacteriana, SAI, meningitis bacteriana, SAI (trastorno), Meningitis por Bacterias, meningitis bacteriana (trastorno), meningitis bacteriana, Meningitis bacteriana
Japanese 詳細不明の細菌による髄膜炎, 細菌性髄膜炎NOS, ショウサイフメイノサイキンニヨルズイマクエン, サイキンセイズイマクエン, サイキンセイズイマクエンNOS, 細菌性髄膜炎, 髄膜炎-細菌性
Swedish Hjärnhinneinflammation, bakteriell
Czech meningitida bakteriální, Bakteriální meningitida, Bakteriální meningitida NOS, Meningitida způsobená blíže určenými bakteriemi
Finnish Bakteerimeningiitti
Korean 상세불명의 세균성 수막염
Polish Zapalenie opon bakteryjne, Zapalenie opon mózgowych bakteryjne
Hungarian Nem meghatározott bacterium okozta meningitis, Bacterialis meningitis, bacterialis meningitis k.m.n., bacterialis meningitis
Norwegian Bakteriell meningitt, Meningitt, bakteriell