Meningitis
B. Denise Hemby and Theresa M. Campo
Definition: Types of Meningitis
A.Meningitis is an acute inflammation of the meninges, the three layers of membranes that enclose the brain and spinal cord. Viral or bacterial infections are the most common causes of meningeal inflammations.
B.Bacterial meningitis is caused by pyogenic inflammation of the meninges and subarachnoid cerebrospinal fluid (CSF). If the infection is left untreated, it can lead to death or lifelong disabilities. There are two categories of infections involving the central nervous system (CNS): one involves the meninges (meningitis) and the other the parenchyma (encephalitis).
C.Bacterial meningitis is a severe infection with associated complications including brain damage, hearing loss, neurologic/learning disabilities, and digit or limb amputations. Mortality rate varies in part with the organism and if it is a nosocomial or a community-acquired infection.
D.Viral meningitis, in most cases (85%), is benign, self-limiting and may only need supportive care, but in some instances, an antiviral may be indicated. Causes of meningitis can include viruses, bacteria, fungi, drugs, and parasites.
1.Viral meningitis is the most common type of meningitis:
a.Enterovirus category: Coxsackievirus A, coxsackievirus B, and echoviruses.
b.West Nile, influenza, mumps, measles, herpes, HIV, Coltivirus (Colorado tick fever), and lymphocytic choriomeningitis virus.
2.Bacterial—most common organisms:
a.Streptococcus pneumoniae, Neisseria meningitidis, Haemophilus influenzae, Listeria monocytogenes, and group B Streptococcus.
3.Fungal meningitis—most common fungi: Cryptococcus (most common form of meningitis in people with HIV or cancer), Histoplasma, Blastomyces, Coccidioides.
4.Parasitic meningitis—most common parasites:
Angiostrongylus cantonensis, Baylisascaris procyonis, Gnathostoma spinigerum.
Naegleria fowleri, a primary amebic meningoencephalitis (PAM) is a very rare form of parasitic meningitis. It is usually fatal.
5.Noninfectious meningitis—common causes:
a.Cancers.
b.Systemic lupus erythematosus (SLE)—often precipitated by drugs.
c.Drug-induced meningitis (DIAM) includes nonsteroidal anti-inflammatory drugs (NSAIDs), corticosteroids, antimicrobials, muromonab (OKT3), eculizumab (Soliris), intravenous immunoglobulin (IVIG), tumor necrosis factor (TNF)-alpha, inhibitors, and antineoplastics. Drugs and diagnostic agents administered intraventicularly and intrathecally.
d.Neurosurgery and deep brain stimulation hardware.
6.Head trauma—noninfectious insult, such as blood in the subarachnoid space, causes aseptic meningitis. Three baseline clinical features have been independently associated with an adverse outcome—hypotension, altered mental status, and seizures.
Incidence
A.There are more than 10,000 cases of viral meningitis reported annually but it is speculated that the number is much higher because the reporting is not as strong as it is with bacterial meningitis.
B.The Centers for Disease Control and Prevention (CDC) reports the incidence of inpatient hospitalization from viral meningitis can range from 25,000 to 50,000 per year, which is approximately 11 per 100,000 population.
C.The incidence of meningitis varies and is based on the etiologic factor; it is higher in developing countries due to the lack of preventative services (i.e., vaccinations).
D.In the United States, almost 4,100 cases and 500 deaths occur annually from bacterial meningitis. The overall incidence of bacterial meningitis in the United States has declined because of the Hib vaccination.
E.In adults after age 60 the risk of meningitis starts to rise again due to underlying comorbid conditions and weakened immune systems.
F.Meningitis affects all races but in the United States there is a higher reported rate in Blacks than Whites and Hispanics.
Pathogenesis
Meningitis is caused by an infectious agent that has established or colonized as a localized infection somewhere in the host. Sites include the nasopharynx, respiratory tract, skin, gastrointestinal (GI) tract, and genitourinary tract. The infectious agent can gain access to the CNS and cause meningeal disease by three major pathways:
A.Invasion into the bloodstream then getting into the CNS—this is the most common mode.
B.A retrograde neuronal pathway—olfactory and peripheral nerves.
C.Direct contiguous spread—sinusitis, otitis media, trauma, congenital malformations.
D.The incubation period is variable, depending on the pathogen/type of meningitis.
Predisposing Factors
A.Peak demographics:
1.Adolescents.
2.Freshman college students living in dormitories.
B.Attendance in the military.
C.Sequela of Lyme disease (LD).
D.Odontogenic infection.
E.Sequela of otitis media, bacterial sinusitis, H. influenzae type B infection, and varicella.
F.Sickle cell disease, asplenia, Hodgkin’s disease, and antibody deficiencies.
G.Review history for STI and HIV infection.
H.Penetrating wound, head trauma, spinal tap, surgery, or anatomic abnormality.
I.Occupational exposure such as laboratory personnel.
J.Travel exposure.
K.Maternal infection and fever at the time of delivery.
L.Lumbar epidural steroid injections.
M.Immunosuppression.
Common Complaints
Only about 44% of adults with bacterial meningitis exhibit the classic triad. Symptoms can develop over several hours to 1 to 2 days.
A.Classic triad:
1.Nuchal rigidity.
2.Fever.
3.Altered mental status (confusion).
Other Signs and Symptoms
A.Sudden onset of a severe, constant headache affecting the entire head that worsens with movement.
B.CNS symptoms (nuchal rigidity, nausea and/or vomiting, confusion, lethargy, decreased level of consciousness [LOC]).
C.Fever or chills.
D.Backache.
E.Photophobia.
F.Difficulty swallowing.
G.Facial and eye weakness and sagging eyelids.
H.Seizures.
I.Rash: The type of rash—macular, maculopapular, petechial, or purpuric—is dependent on the
virus/
J.Anorexia.
K.Nausea/vomiting.
L.Chronic meningitis: Usually have subacute onset of symptoms, including fever, headache, and vomiting.
Subjective Data
A.Review the onset, course, and duration of symptoms, including a progressive petechial or ecchymotic rash.
B.Determine current or recent history of ear infections, upper respiratory infection (URI), sinus infection, and chickenpox exposure.
C.Ask the patient about any recent dental procedures, extractions, and gum procedures.
D.Review the patient’s recent history of tick bite and any treatments.
E.Review the patient’s recent history of Hib immunization.
F.Evaluate a history of serious drug allergies.
G.Evaluate a history of recent head trauma/fracture.
H.Evaluate full history for ventriculoperitoneal shunt and other cranial surgery/procedures.
I.Review history for use of lumbar epidural steroid injections for pain.
J.Review all medications, including over-the-counter (OTC) and herbal products. Determine recent use of antibiotics.
K.Review for a history of illicit drug use, especially the intravenous (IV) route.
L.Review any recent travel locations.
Physical Examination
A.Check temperature, pulse, respirations, and blood pressure.
B.Inspect:
1.Observe general overall appearance.
2.Examine the skin for the presence of a petechial or ecchymotic rash.
3.Complete an ear, nose, and throat exam.
4.Examine mouth and teeth for dental diseases and disorders.
5.Assess the patient for dehydration.
6.Observe the patient for seizure activity.
7.Assess level of pain.
8.Inspect for cranial nerve palsies.
C.Auscultate heart and lungs, monitor breathing pattern.
D.Palpate:
1.Neck: Palpate the lymph nodes.
2.Palpate the mastoid bones.
3.Abdominal examination: Hepatosplenomegaly.
E.Neurologic exam:
1.Perform a complete neurologic examination.
2.Evaluate for signs of meningeal irritation by means of Brudzinski’s and Kernig’s signs (see Figures 19.1 and 19.2). Positive Brudzinski’s and Kernig’s signs:
a.Brudzinski’s sign: Place the patient supine and flex the head upward. Resulting flexion of both hips, knees, and ankles with neck flexion indicates meningeal irritation.
b.Kernig’s sign: Place the patient supine. Keeping one leg straight, flex the other hip and knee to a bent knee to form a 90-degree angle. Slowly extend the lower leg. This places a stretch on the meninges, resulting in pain and spasm for the hamstring muscle. Resistance to further extension can be felt.
Diagnostic Tests
Bacterial meningitis must be the foremost consideration in the differential diagnosis. In acute meningitis, a lumbar puncture (LP) and CSF exam should be done to identify the causative organism and, especially with bacterial meningitis, the antibiotics sensitivities.
A.LP to obtain CSF for analysis:
1.Opening pressure should be measured.
2.Cell count.
3.Gram stain and cultures, sensitivity.
4.White blood cells (WBCs) and absolute neutrophil count.
5.CSF protein and glucose.
B.Laboratory tests:
1.Complete blood count (CBC) with differential and platelets.
2.Complete metabolic panel (CMP).
3.Coagulation profile.
4.Blood cultures × 2.
C.Cultures of petechial or purpuric lesion scraping and synovial fluid.
D.MRI or CT scan, with and without contrast (a screening CT is not necessary in the majority of the patients).
Differential Diagnoses
Bacterial meningitis must be the foremost consideration with patients with fever, headache, neck stiffness, and altered mental status.
A.Meningitis:
1.Bacterial etiology.
2.Viral etiology.
3.Fungal etiology.
4.Aseptic meningitis.
5.Chronic meningitis.
B.Brain abscess.
C.Brain neoplasms.
D.Encephalitis.
E.Febrile seizures.
F.LD.
G.Herpes.
H.Delirium tremens.
I.Gonorrhea.
J.Otitis media.
K.Dental abscess.
L.Chickenpox.
M.Sinusitis.
N.Mastoiditis.
O.Subarachnoid hemorrhage.
Plan
A.General interventions:
1.Treatment for meningitis is initiated in the hospital setting. Delayed initiation of antibiotic treatment in bacterial meningitis patients is strongly associated with death and poor outcomes. Begin empiric antibiotic coverage according to age and presence of overriding physical conditions. The treatment depends on the organisms. Treat aggressively because the progression of disease is often rapid. Empiric therapy should be initiated immediately after blood cultures are drawn after the LP is done and CSF has been sent for testing. The choice of agents is based on known predisposing factors. Once pathogen is identified and antimicrobial susceptibilities are known the antibiotics should be modified for targeted treatment. The antibiotic used should attain adequate levels in the CSF and that depends on the solubility, protein-binding capacity, molecular size, and the patient’s degree of meningeal inflammation.