Chapter 23: Infections of the nervous system

Question 1

Through which routes may infectious agents reach the nervous system?

Answer 1

• Hematogenous spread by way of the arterial blood supply (most common)
• Direct implantation of microorganisms is almost invariably due to open or penetrating trauma; (rarely iatrogenic, by a lumbar puncture needle or into a surgical field)
• Local extension can occur with infections of the skull or spine (sources include air sinuses, infected teeth, cranial or spinal osteomyelitis, and congenital malformations)
• Peripheral nerves also may serve as paths of entry for a few pathogens—in particular, viruses such as rabies and herpes zoster.

Question 2

True/false: The epidural and subdural spaces can be involved by viral infections, usually as a consequence of direct local spread

Answer 2

False! They are usually involved in bacterial or fungal infections (instead of viral)

Question 3

True/false: The underlying arachnoid and subarachnoid spaces usually are unaffected, but a large subdural empyema may produce a mass effect

Answer 3

True

Question 4

What clinical symptoms do most patients with epidural and subdural infections present with?

Answer 4

Most patients are febrile, with headache and neck stiffness, and if untreated may develop focal neurologic signs referable to the site of the infection, lethargy, and coma

Question 5

True/false: even if an infected patient is treated with promptly, a thickened dura may be a residual finding

Answer 5

No, if treated prompt, complete recovery is usual (although it can occur is resolution is complete)

Question 6

What is meningitis?

Answer 6

Meningitis is an inflammatory process involving the leptomeninges within the subarachnoid space; if the infection spreads into the underlying brain, it is termed meningoencephalitis

Question 7

Does meningitis mean there is an infection?

Answer 7

Not per definition, chemical and carcinomatous meningitis can also occur. However infectious meningitis is most common

Question 8

Infectious meningitis can be broadly divided into acute pyogenic (i), aseptic (ii) and chronic (iii) subtypes. What do i-iii mean?

Answer 8

i (acute pyogenic): usually bacterial
ii (aseptic): usually viral
iii (chronic): usually tuberculous, spirochetal or fungal

Question 9

How are the various causes of meningitis distinguished?

Answer 9

Examination of CSF

Question 10

What are symptoms of patients with acute pyogenic (bacterial) meningitis?

Answer 10

Across ages, patients typically show systemic signs of infection along with meningeal irritation and neurologic impairment, including headache, photophobia, irritability, clouding of consciousness, and neck stiffness

Question 11

DON’T LEARN THIS

What are the common bacteria that are cause of acute pyogenic meningitis?

Answer 11

The most likely causes of bacterial meningitis vary with patient age. In neonates, common organisms are Escherichia coli and group B streptococci. In adolescents and young adults, Neisseria meningitidis is the most common pathogen; in older adults, Streptococcus pneumoniae and Listeria monocytogenes are more common

Question 12

What will a lumbar puncture and CSF of bacterial/acute pyogenic meningitis reveal?

Answer 12

Lumbar puncture: an increased pressure

CSF: Abundant neutrophils, elevated protein, and reduced glucose

Question 13

True/false: untreated pyogenic meningitis is fatal

Answer 13

Often yes, but with prompt diagnosis and administration of antibiotics, most patients can be saved.

Question 14

What are clinical difference between acute pyogenic and viral meningitis?

Answer 14

The clinical course is less fulminant than in pyogenic meningitis and is typically self-limiting

Question 15

What does the CSF of viral meningitis show?

Answer 15

Lymphocytosis, moderate protein elevation, and a normal glucose level, but bacteria cannot be cultured

Question 16

Can a virus be identified by culture and serologic methods?

Answer 16

No, it is often difficult

(application of nucleic acid sequencing has the potential to change our understanding of these cases. There are no distinctive macroscopic findings except for brain swelling, which may be seen in only some instances. On microscopic examination, there is either no recognizable abnormality or a mild to moderate leptomeningeal lymphocytic infiltrate)

Question 17

How will tuberculous meningitis appear (both clinically as morphologically)?

Answer 17

Tuberculous meningitis usually manifests with generalized signs and symptoms of headache, malaise, mental confusion, and vomiting. There is only a moderate increase in CSF cellularity, with mononuclear cells or a mixture of polymorphonuclear and mononuclear cells; the protein level is elevated, often strikingly so, and the glucose content typically is moderately reduced or normal

Question 18

True/false: Several pathogens, including mycobacteria, some spirochetes, and fungi, cause a chronic meningitis; infections with these organisms also may involve the brain parenchyma.

Answer 18

True

Question 19

What is neurosyphilis?

Answer 19

Tertiary stage of syphilis

I don’t think this is necessary to know

Question 20

How can spirochetal infections appear?

don’t think you ought to know this

Answer 20

• Meningovascular neurosyphilis
• Paretic neurosyphilis
• Tabes dorsalis

(the differences are mostly the locations)

Question 21

What is neuroborreliosis?

don’t think you ought to know this

Answer 21

Neuroborreliosis refers to involvement of the nervous system by the spirochete Borrelia burgdorferi, the causative agent of Lyme disease. Neurologic signs and symptoms are highly variable and include aseptic meningitis, facial nerve palsies, mild encephalopathy, and polyneuropathies.

Question 22

Can fungal infection of the nervous system give rise to chronic meningitis?

Answer 22

Yes

Question 23

Can all pathogens of infectious meningitis be associated with parenchymal infection?

Answer 23

Yes

Question 24

What are several fungal pathogens that cause CNS disease?

don’t think you ought to know this

Answer 24

• Cryptococcus neoformans
• Histoplasma capsulatum
• Coccidioides immitis

Question 25

Fill in: In general, viral infections are diffuse/localized, bacterial infections (not associated with meningitis) are diffuse/localized

Answer 25

diffuse and localized respectively

Question 26

Is brain abscess often caused by viral or bacterial infections?

Answer 26

Bacterial

Question 27

What are abscesses?

Answer 27

Abscesses are discrete destructive lesions with central liquefactive necrosis surrounded by a rim of vascularized granulation and fibrous tissue

Question 28

What is viral encephalitis?

Answer 28

Viral encephalitis is a parenchymal infection of the brain that is almost invariably associated with menin- geal inflammation (meningoencephalitis)

Question 29

Different viruses of viral encephalitis can show varying patterns of injury, what are the most characteristic histologic features?

Answer 29

perivascular and parenchymal mononuclear cell infiltrates, microglial nodules, and neuronophagia. Certain viruses also form characteristic inclusion bodies.

Question 30

True/false: viral encephalitis infect any type of cell

Answer 30

Some viruses infect specific CNS cell types, while others preferentially involve particular brain regions

Question 31

What viruses is the nervous system particularly susceptible to?

Answer 31

e.g. rabies- and poliovirus

Question 32

Just read the following flashcards, don’t study s.v.p.

Answer 32

Intrauterine viral infection following transplacental spread of rubella and CMV may cause destructive lesions, and Zika virus causes developmental abnormalities of the brain. In addition to direct infection of the nervous system, the CNS also can be injured by immune mechanisms after systemic viral infections.

Question 33

In the book, arboviruses, herpesviruses, cytomegalovirus, poliovirus, rabies virus, HIV and polymavirus are explained in great detail on p865-867

Answer 33

They are not included in these flashcards, since they aren’t discussed in the lecture. However, they are listed in the course guide so feel free to look at those pages :)

Question 34

What is Progressive multifocal leukoencephalopathy (PML)?

Answer 34

Progressive multifocal leukoencephalopathy (PML) is caused by JC virus, a polyomavirus, which preferentially infects oligodendrocytes, resulting in demyelination as these cells are injured and then die

Question 35

What clinical aspects do patients with PML present with?

Answer 35

Patients develop focal and relentlessly progressive neurologic signs and symptoms, and imaging studies show extensive, often multifocal lesions in the hemispheric or cerebellar white matter.

Question 36

What do fungal infections produce?

Answer 36

Parenchymal granulomas or abscesses, often associated with meningitis (different types are not discussed)

Question 37

Other meningoencephalitides (cerebral toxoplasmosis, cysticercosis, amebiasis) are also not discussed

Answer 37

But feel free to look at p868

Question 38

What are prion diseases?

Answer 38

Prion diseases are a group of infectious diseases in which the causative agent is an abnormal form of a cellular protein. These include sporadic, familial, iatrogenic, and variant forms of Creutzfeldt-Jakob disease (CJD), as well as animal diseases such as scrapie in sheep and bovine spon- giform encephalopathy in cattle (“mad cow disease”)

further info (p869-890) are skipped because they’re also not explained in the lecture