Infections of the Central Nervous System

Infections of the Central Nervous System

Michelle VanDemark

Joanne V. Hickey

Infections of the central nervous system (CNS) can be life-threatening and require early recognition and treatment to improve outcomes. A comprehensive medical history and physical examination provide critical information in establishing the cause of the CNS infection and appropriate nursing interventions. This chapter will focus on meningitis, encephalitis, and abscesses. Other selected nervous system infections are briefly presented in tabular format.


Meningitis is an inflammation of the meninges that surround the brain and spinal cord. Primary causes of meningitis are bacterial or viral infections but meningitis can also be due to a fungus or parasite. Infections can occur when an organism gains access to the meninges via the blood-borne route or through the spread of nearby infections such as sinusitis, mastoiditis, otitis media, osteomyelitis of the skull or vertebrae, or pneumonia.1 Other sources of cerebrospinal fluid (CSF) contamination include neurosurgical procedures, lumbar puncture (LP), and penetrating head wounds. Infections of the meninges also result from preexisting connections between the CNS and dural defects, congenital sinuses, or occult encephaloceles.2

Bacterial Meningitis

Bacterial meningitis is a pyogenic (purulent or suppurative) infection that involves the pia-arachnoid layers of the meninges and the subarachnoid space (SAS), including CSF. Common risk factors for the development of bacterial meningitis include immunocompromised conditions such as organ transplantation, cancer, diabetes mellitus, asplenia, chronic steroid therapy, HIV infection, intravenous
drug use, alcoholism, or malnutrition. Other risk factors include penetrating head trauma, otorrhea, rhinorrhea, or neurosurgical procedures. Also, living in close quarters such as college dormitories or military barracks can enhance the spread of meningitis; and travel to endemic areas such as sub-Saharan Africa is also a risk factor for meningitis.3

The annual incidence of bacterial meningitis is 4 to 6 cases per 1,00,000 adults (persons older than 16 years of age).4 In the United States, the annual incidence of people acquiring bacterial meningitis has decreased to 1.38 cases per 1,00,000 population with the median age shifting up to 41.9 years.5, 6, 7 The two populations that remain the greatest risk for acquiring meningitis are the very young (<2 months) and the elderly.7 Two factors have changed the epidemiology of bacterial meningitis significantly over the past 15 years. The first one is the advent of the Haemophilus influenzae type b (Hib) vaccine, conjugate pneumococcal vaccine, and recently the conjugated meningococcal vaccine. The incidence of meningococcal disease has decreased dramatically since the meningococcal vaccine; however, it does not contain serogroup B which is a causative agent of meningococcal disease.8 Secondly, there is an increasing emergence of antimicrobial resistant organisms, making treatment challenging.

Common Causative Organisms

The common causative organisms for bacterial meningitis tend to differ by age group. In older children and adults, Streptococcus pneumoniae and Neisseria meningitides are the most common causative organisms of meningitis.8 S. pneumoniae is the primary agent responsible for community-acquired bacterial meningitis. In older adults (50 years of age and older), S. pneumoniae is likely to cause meningitis in association with pneumonia or otitis media. Other common causative organisms include group B streptococcus (GBS) and Listeria monocytogenes. L. monocytogenes is responsible for meningitis in people who are immunosuppressed.8 In addition, gram-negative bacilli Enterobacteriaceae (Escherichia coli, Klebsiella pneumoniae, Pseudomonas, Enterobacter, and Serratia) are the organisms likely to cause meningitis in association with chronic lung disease, sinusitis, neurosurgical procedures, or chronic urinary tract infection in older patients (Table 29-1). Except during summer when incidence decreases, the rate of cases of meningitis is relatively constant throughout the year.





Pneumococcal meningitis

Streptococcus pneumoniae (gram-positive diplococci)

  • Most common type of meningitis with worldwide distribution

  • Most common in young children and older adults

  • Occurs mostly in winter and early spring

  • Predisposing conditions include pneumonia, sinusitis, alcoholism, and head trauma

Haemophilus influenzae meningitis

H. influenzae (gram-negative cocci)

  • Used to occur most often in infants and children, but occurring more in adults

  • Incidence has decreased in half due to H. influenzae vaccine

  • Often follows upper respiratory or ear infections

Meningococcal meningitis

Neisseria meningitidis (gram-negative diplococci)

  • Highest incidence in children and young adults

  • Presentation includes petechial rash, purpuric lesions, or ecchymosis that develop in 50% of patients

  • About 10% develop a fulminating infection with overwhelming septicemia (meningococcemia); creates a medical emergency (high fever, circulatory collapse from adrenocortical insufficiency secondary to hemorrhage and necrosis of the adrenals called Waterhouse-Friderichsen syndrome); disseminated intravascular coagulation may also occur

  • Death can result hours after onset

Listeria monocytogenes meningitis

  • Fourth most common cause of meningitis in nonsurgical bacterial meningitis

Less common sources

  • Staphylococcus aureus

  • Streptococcus group A

  • Streptococcus group B

  • Increased incidence of nosocomial infections noted

  • Often introduced during neurosurgical procedures (craniotomy) or related to brain abscess, epidural abscess, or head trauma

Less common sources

  • Klebsiella

  • Proteus

  • Pseudomonas

  • Related to lumbar puncture, spinal anesthesia, or shunting procedure

Tuberculosis meningitis

  • Myobacterium tuberculosis

  • Secondary infection resulting from bacterial seeding of the meninges from tuberculosis elsewhere in the body

  • Most common in children

  • Incidence reflects the rate of tuberculosis in a country (relatively low in the United States)

aThe organisms presented here are responsible for 80-90% of the cases of bacterial meningitis worldwide; these organisms are normally found in the nasopharynx of a significant portion of the population.

Jul 14, 2016 | Posted by in NURSING | Comments Off on Infections of the Central Nervous System

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