Chapter 35: Infections of the Central Nervous System. Answers Explained

MULTIPLE CHOICE 1. What is the volume of cerebrospinal fluid (CSF) in an average adult? a. 90 to 150 mL b. 15 to 45 mL c. 40 to 80 mL d. 200 to 300 mL A In normal adults, the CSF volume ranges from 90 to 1 ...

MULTIPLE CHOICE 1. What is the volume of cerebrospinal fluid (CSF) in an average adult? a. 90 to 150 mL b. 15 to 45 mL c. 40 to 80 mL d. 200 to 300 mL A In normal adults, the CSF volume ranges from 90 to 150 mL, the protein level is 15 to 45 mg/dL, and the CSF glucose level is 40 to 80 mg/dL (CSF glucose:serum glucose ratio of 0.6). REF: 856 OBJ: Level 1: Recall 2. All of the following organisms commonly cause meningitis except: a. Streptococcus pneumoniae. b. Pseudomonas aeruginosa. c. Haemophilus influenzae. d. Neisseria meningitidis. B Acute meningitis is commonly caused by bacteria (e.g., S. pneumoniae, N. meningitidis, H. influenzae), or viruses (e.g., enteroviruses, herpes virus, mumps virus). REF: 856 OBJ: Level 1: Recall 3. A college student is examined at the emergency department; he is disoriented with a fever, intense headache, stiff neck, vomiting, and sensitivity to light. His friends say that he has been sick for about 2 days and that his condition worsened over the last 3 hours. The physician does a complete blood count (CBC) and electrolytes. The electrolytes are normal, but the patient’s white blood count (WBC) is 12,000 cells/L. What test should the physician order next? a. Urinalysis and urine culture b. Stool Gram stain and culture c. Cerebrospinal fluid Gram stain and culture d. Blood cultures  3 C Patients with acute meningitis usually present with fever, headache, vomiting, photophobia, and altered mental status. REF: 856 OBJ: Level 3: Synthesis 4. What is the first step in developing meningitis? a. A cold that compromises your immune system b. Living in close quarters, like military barracks or a college dorm c. Poor sanitary conditions d. Nasopharyngeal colonization by a meningeal pathogen D The first step in the development of a meningeal infection with bacteria involves nasopharyngeal colonization by one of the meningeal pathogens, followed by local invasion across the mucosal barrier and entry into the bloodstream. REF: 856 OBJ: Level 1: Recall 5. What organism is the most common cause of meningitis in adults? a. Streptococcus pneumoniae b. Pseudomonas aeruginosa c. Haemophilus influenzae d. Neisseria meningitidis A S. pneumoniae is a gram-positive diplococcus and is the most common cause of meningitis in adults and the second most common cause of meningitis in children. REF: 857 OBJ: Level 1: Recall 6. What organism is a common cause of meningitis in neonates and infants up to 3 months of age and can be contracted by passing through the birth canal? a. Streptococcus pneumoniae b. Streptococcus agalactiae c. Haemophilus influenzae d. Neisseria meningitidis B S. agalactiae or group B streptococcus is a gram-positive coccus that is often isolated from rectal or vaginal cultures of asymptomatic pregnant women. It is a common cause of meningitis in neonates and infants up to age 3 months. REF: 857 OBJ: Level 2: Interpretation 7. What condition is characterized by lymphocytic pleocytosis in the cerebrospinal fluid (CSF) but a lack of identifiable organism after routine culture and Gram stain? a. Purulent meningitis b. Septic meningitis c. Aseptic meningitis d. Malignant meningitis C Viruses are the most common cause of aseptic meningitis, a condition characterized by a lymphocytic pleocytosis in the CSF and lack of identifiable etiologic agent after routine stains and culture of the CSF. REF: 858 OBJ: Level 2: Interpretation 8. All the following viruses can resist inactivation by gastric acid except: a. enteroviruses. b. adenoviruses. c. parvovirus. d. herpesvirus. D Some viruses, such as enteroviruses, adenoviruses, and parvovirus, can resist inactivation by gastric acid. After initial replication at the site of mucosal colonization, viremia develops, followed by invasion of the central nervous system (CNS). REF: 858 OBJ: Level 1: Recall 9. What enterovirus is commonly associated with neurologic illness? a. Coxsackievirus B b. Parvovirus c. Herpesvirus 1 d. Calicivirus A A Enteroviruses (EVs) belong to the family Picornaviridae and include the polioviruses, coxsackieviruses A and B, echoviruses, and the newly numbered EVs. The EVs that are frequently associated with neurologic illness include coxsackievirus B and echoviruses. REF: 858 OBJ: Level 1: Recall 10. What type of meningitis is usually uncomplicated and resolves in 2 to 7 days? a. Septic meningitis b. Enteroviral c. Bacterial d. Meningococcal B Most cases of enteroviral meningitis are uncomplicated, with signs and symptoms resolving in 2 to 7 days. REF: 859 OBJ: Level 2: Interpretation 11. Common arborviruses that cause meningitis include all the following except: a. St. Louis encephalitis virus. b. La Crosse virus. c. Venezuelan equine encephalitis. d. West Nile virus. C Although several of these viruses cause encephalitis, aseptic meningitis and meningoencephalitis can also occur. The common arboviruses causing aseptic meningitis include St. Louis encephalitis virus, La Crosse virus, eastern and western equine encephalitis virus, and West Nile virus. REF: 859 OBJ: Level 1: Recall 12. What is a common neurologic complication with the mumps? a. Encephalitis b. Meningoencephalitis c. Viremia d. Aseptic meningitis D The mumps virus, a member of the family Paramyxoviridae, is an RNA virus that commonly causes parotitis. Aseptic meningitis is the most common neurologic complication. REF: 859 OBJ: Level 1: Recall 13. What virus is an uncommon cause of aseptic meningitis that can be acquired from dust or food contaminated with urine or feces from infected rodents and hamsters? a. Lymphocytic choriomeningitis virus b. Epstein-Barr virus c. Guillain-Barré virus d. Astrovirus A Lymphocytic choriomeningitis virus is a member of the Arenaviridae family. It is an RNA virus that is an uncommon cause of aseptic meningitis in humans. The virus is shed in the urine and other excretions of infected rodents and hamsters. Humans are infected by aerosol or by ingestion of dust or food contaminated with the urine, feces, blood, or nasopharyngeal secretions of infected rodents. REF: 859 OBJ: Level 2: Interpretation 14. Syphilitic involvement in the central nervous system (CNS) can take all of the following forms except: a. syphilitic meningitis. b. aseptic meningitis. c. gummatous neurosyphilis. d. parenchymatous neurosyphilis. B Syphilitic involvement of the CNS can take one of four forms: syphilitic meningitis, meningovascular syphilis, parenchymatous neurosyphilis, and gummatous neurosyphilis. REF: 860 OBJ: Level 1: Recall 15. All of the following are common fungal causes of central nervous system (CNS) infection except: a. Cryptococcus neoformans. b. Coccidioides immitis. c. Candida albicans. d. Histoplasma capsulatum. C Fungi are rare causes of CNS infections. The most common organisms in CNS fungal infections include C. neoformans, C. immitis, H. capsulatum, and Blastomyces dermatitidis. REF: 860 OBJ: Level 1: Recall 16. What fungus causes chronic meningitis in HIV patients? a. Cryptococcus neoformans b. Coccidioides immitis c. Candida albicans d. Histoplasma capsulatum A C. neoformans is an encapsulated basidiomycetous yeast. It can spread hematogenously to the central nervous system (CNS) from pulmonary foci and can cause chronic meningitis, particularly in patients with acquired immunodeficiency syndrome (AIDS). REF: 860 OBJ: Level 1: Recall 17. A teenager and her friends go to the lake and spend the day swimming and picnicking. Later that evening, she starts to feel sick. She complains of a headache and general malaise. The next morning, she is very ill and is rushed to the emergency department. Many neurologic changes are noted. Despite the staff’s best efforts, the teenager dies. Autopsy reveals the presence of small protozoans in her brain tissue. What is the most probable organism that caused her death? a. Acanthamoeba spp. b. Naegleria fowleri c. Balamuthia mandrillaris d. Angiostrongylus cantonensis B N. fowleri can cause a rapidly progressive and almost always fatal primary meningoencephalitis. It is found in warm fresh water and moist soil. Most cases of infection have been associated with swimming in warm natural bodies of water. Acanthamoeba spp. and B. mandrillaris usually cause granulomatous amebic encephalitis with a more insidious onset. REF: 861 OBJ: Level 3: Synthesis 18. Infection with what organism results in a chronic meningoencephalitis, more commonly known as sleeping sickness? a. Gnathostoma spinigerum b. Baylisascaris procyonis c. Trypanosoma brucei d. Trypanosoma cruzi C Trypanosomes that infect humans include Trypanosoma brucei subsp. gambiense, Trypanosoma brucei subsp. rhodesiense, and Trypanosoma cruzi. The first two are found predominantly in Africa. Humans are infected by the bite of tsetse flies. T. brucei gambiense results in a more chronic and slowly progressing form of sleeping sickness compared to T. brucei rhodesiense, which has a more rapid and acute course. Both diseases are fatal if untreated. REF: 862 OBJ: Level 2: Interpretation 19. All of the following are common causes of viral encephalitis except: a. herpes viruses. b. enteroviruses. c. arboviruses. d. toroviruses. D The most common causes of encephalitis are viruses including herpes viruses, enteroviruses, and arboviruses. REF: 862 OBJ: Level 1: Recall 20. All of the following are important arboviruses except: a. alphaviruses (Venezuelan equine encephalitis viruses, eastern equine encephalitis, and western equine encephalitis). b. St. Louis encephalitis virus. c. La Crosse virus. d. Lassa fever virus. D Arboviruses (arthropod-borne viruses) are RNA viruses that demonstrate strong tropism for the central nervous system. These viruses are transmitted to humans by mosquitoes, ticks, or sandflies. Important arboviruses in the western hemisphere include members of the alphaviruses (eastern equine encephalitis, western equine encephalitis, and Venezuelan equine encephalitis viruses), flaviviruses (St. Louis encephalitis virus), bunyaviruses (La Crosse virus), and Coltivirus (Colorado tick fever). REF: 862 OBJ: Level 1: Recall 21. What virus, spread by the mosquito, causes a typically self-limiting illness, but can be associated with a rash, aseptic meningitis, myelitis, and fatal encephalitis? a. West Nile virus b. Eastern equine encephalitis c. Colorado tick fever d. Venezuelan equine encephalitis A West Nile virus (WNV) is a mosquito-borne flavivirus that commonly causes a self-limited febrile illness, often associated with a rash. In 1999 the virus was introduced in the United States; it has since spread rapidly. Neurologic involvement includes aseptic meningitis, myelitis, and fatal encephalitis. The mortality rate is about 5%, and death occurs mainly in older patients. REF: 863 OBJ: Level 2: Interpretation 22. A farmer is bitten by a raccoon. He takes the usual precautions and washes the wound with soap and water, and then puts a bandage on it. A couple of days later, he begins to feel tired, has an upset stomach, and the wound is painful. About 2 days after noticing the symptoms, the farmer begins to feel agitated. He has a seizure and hallucinations. What condition matches the farmer’s symptoms and history? a. West Nile virus b. Rabies c. Colorado tick fever d. Lassa fever B Infection with rabies occurs following bites from infected animals, such as skunks, raccoons, bats, and foxes, as well as domesticated animals, such as dogs. Initial symptoms include fatigue, gastrointestinal symptoms, and pain at the bite wound. Rabies can present as acute encephalitis indistinguishable from other viral encephalitides or with the classic syndrome of agitation, emotional liability, seizures, and hallucinations (furious rabies). REF: 863 OBJ: Level 3: Synthesis 23. From where do most cerebral abscesses spread? a. Middle ear infections b. Mastoiditis c. Paranasal sinus infections d. All of the above D The majority of cerebral abscess occur because of spread from a contiguous focus of infection in the middle ear, mastoid cells, or paranasal sinuses. REF: 863 OBJ: Level 1: Recall 24. What are the most common bacteria isolated from nontraumatic brain abscesses? a. Staphylococcus b. Enteric gram-negative rods c. Streptococcus d. Clostridium C The most common organism isolated from nontraumatic brain abscesses include aerobic, anaerobic, and microaerophilic streptococci. Streptococci, such as S. anginosus, S. intermedius, and S. constellatus, are isolated in 50% to 70% of cases. REF: 863 OBJ: Level 1: Recall 25. Diagnosis of central nervous system (CNS) infections is based on: a. neurologic symptoms. b. physical symptoms. c. history. d. laboratory examination of CSF. D The diagnosis of CNS infections is based on examination of CSF samples obtained by lumbar puncture. REF: 864 OBJ: Level 1: Recall 26. A cerebrospinal fluid (CSF) sample collected from a child yields the following results: turbid and cloudy, very high total protein levels, and very low glucose levels. What would the probable diagnosis be? a. Bacterial meningitis b. Aseptic meningitis c. Encephalitis d. Brain abscess A In acute bacterial meningitis, the CSF is turbid or cloudy because protein levels are significantly raised. Glucose levels are very low (less than 40% of serum glucose concentration) in most patients with bacterial meningitis. REF: 864 OBJ: Level 3: Synthesis