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Medical conditions > CNS Infections > Flashcards

CNS Infections Flashcards

MLA conditions: Meningitis, encephalitis, brain abscess. Describe causes, diagnosis, and management. Recognise: myelitis

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USMLE® Step 1 flashcards
1
Q

What is meningitis?

A

An inflammation of the meninges (covers the brain and spinal cord), usually caused by an infection, but can occur without underlying infection.

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2
Q

What are the different types of meningitis?

A

Bacterial including TB, viral, fungal, non-infective

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3
Q

What are the 3 most common bacteria that cause meningitis?

Which is the most common?

A

**1. Streptococcus pneumoniae, **
2. Neisseria meningitidis
3. Haemophilus influenzae.

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4
Q

What are the 3 most common viruses that cause meningitis?

A
  1. Enteroviruses,
  2. herpes simplex virus, and
  3. mumps virus.
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5
Q

For neonates, which additional pathogens may cause meningitis?

A

Group B Streptococcus, Escherichia coli, Listeria monocytogenes.

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6
Q

For elderly, which additional pathogens may cause meningitis?

A

Listeria monocytogenes

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7
Q

What are some causes of non-infectious meningitis? How are they different in presentation?

A

Cancer (meningeal involvement such as leukaemia), systemic lupus erythematosus, certain drugs, or head injury

Onset is often less acute than infectious (days to a week rather than hours to days)

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8
Q

How does viral meningitis differ from bacterial meningitis in terms of prognosis and treatment

A

Viral meningitis generally has a better prognosis and is often self-limiting, requiring supportive care. Bacterial meningitis is more severe, requiring prompt antibiotic treatment to prevent complications and death

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9
Q

What are the classic signs and symptoms of meningitis?

A

Fever, headache, neck stiffness (classic triad in adults), photophobia, nausea/vomiting, altered mental status e.g. drowsiness, and sometimes a rash (in meningococcal meningitis).

Infants may present with nonspecific symptoms such as irritability, poor feeding, lethargy, bulging fontanelle, and seizures,

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10
Q

What are additional signs that may indicate meningococcal septicaemia?

A

Signs include a non-blanching purpuric rash, hypotension, tachycardia, cold extremities, and multi-organ failure.

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11
Q

Which 2 clinical tests are specific but not sensitive to bacterial meningitis?

A

Kernig’s sign and Brudzinski’s sign (specific but not sensitive)

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12
Q

What may tuberculous meningitis present additionally with?

A

Cranial nerve symptoms. Travel history.

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13
Q

If you suspect meningitis in the community, what should be your first step?

A

Immediate transfer to the hospital.

For people with strongly suspected meningococcal disease, give intravenous or IM ceftriaxone or benzylpenicillin

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14
Q

If bacterial meningitis is strongly suspected e.g. patient very unwell, having non-blanching purpura, what should you do before any investigations?

A

Take a blood culture and give empiric antibiotics (broad-spectrum e.g. ceftriaxone).

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15
Q

What is the pathophysiology of meningitis?

What does it do to the blood-brain barrier?

A

Pathogens invade the meninges. releasing toxins and triggering an inflammatory response.

This leads to increased permeability of the blood-brain barrier which increases WBC and proteins, resulting in cerebral oedema and raised ICP.

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16
Q

How do pathogens reach the meninges? List 3 ways

A
  • bloodstream/septicaemia (hematogenous spread),
  • direct extension from nearby infections (e.g., sinusitis, otitis media), or
  • through a breach in the skull or spinal column connecting the nasopharynx and the meninges.
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17
Q

What are the typical inflammatory responses in meningitis? Why can it cause increased ICP i.e. headache, N/V?

A

Due to inflammatory responses: release of cytokines, recruitment of white blood cells, and increased production of cerebrospinal fluid (CSF), leading to swelling and pressure on the brain.

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18
Q

What are the key steps in diagnosing meningitis?

A

Diagnosis involves clinical evaluation, lumbar puncture for CSF analysis, blood cultures, and sometimes imaging studies.

Other blood tests: FBC, UnE, blood gases and organ function tests: blood pH, organ damage

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19
Q

List 5 domains in a lumbar puncture that you should look for in diagnosis of meningitis.

A
  • Opening pressure/appearance
  • WBC: number and type
  • glucose
  • protein
  • culture (and gram staining)
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20
Q

What are the typical cerebrospinal fluid (CSF) findings in bacterial versus viral meningitis?

A

Bacterial: Cloudy CSF, elevated WBC (predominantly neutrophils), low glucose, high protein.

Viral: normal/elevated WBC count (predominantly lymphocytes), normal glucose, moderately elevated protein.

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21
Q

When should imaging e.g. CT be considered before a lumbar puncture? What are some symptoms that?

A

Imaging is recommended if there are signs of increased ICP:

  • focal neurological deficits,
  • pupil abnormality,
  • rapidly dropping GCS
  • new-onset seizures,

or immunocompromised state to rule out mass effect or other contraindications.

22
Q

What are the first-line antibiotics used in the treatment of bacterial meningitis? What additional antibiotic may be used in immunocompromised/elderly people?

A

Ceftriaxone or cefotaxime

Vancomycin for strep. pneumoniae
Amoxicillin/ampicillin to treat Listeria

23
Q

What is the role of corticosteroids in the management of meningitis?

A

Corticosteroids, such as dexamethasone, are used to reduce inflammation and prevent neurological complications, particularly in cases of pneumococcal meningitis.

24
Q

How should close contacts of a patient with meningococcal meningitis be managed?

What is the most common antibiotic of choice?

A

Close contacts should receive prophylactic antibiotics.

Ciprofloxacin: Single dose, more commonly used.

25
Q

What are the potential complications of meningitis? Consider 3 risks you might have to mention to an infant’s parents.

A

Hearing loss, seizures, hydrocephalus, cognitive deficits, and in severe cases, death.

Long-term: hearing loss, epilepsy, cognitive/behavioural problems, especially for younger patients.

26
Q

What vaccines are available to prevent meningitis?

A

Vaccines include the Haemophilus influenzae type b (Hib) vaccine, pneumococcal vaccines (PCV13, PPSV23), and meningococcal vaccines (MenACWY, MenB).

27
Q

What are 3 risk factors for developing meningitis?

A
  1. Age (infants and elderly),
  2. immunocompromised state e.g. medical conditions, chronic organ disease, including splenectomy
  3. living in close quarters (e.g., uni students living in dormitories, military barracks)
28
Q

Is bacterial meningitis a notifiable disease?

A

Yes

29
Q

Co-occurring meningitis and encephalitis is called –?

A

Meningoencephalitis

30
Q

How might meningitis and encephalitis differ in presentation?

List the positive symptoms in each that the other doesn’t have.

A

Meningitis: neck stiffness — may be concurrent in meningoencephalitis.

Encephalitis: altered mental state and are more likely to have mental state changes and neurological deficits e.g. weaknesses.

31
Q

What is the most common cause of encephalitis?

A

HSV-1
Herpes simplex virus

Other viruses: Varcella-zoster virus, CMV, EBV

32
Q

How does HSV-1 enter the brain?

A

Through the olfactory nerve or other mucosal surfaces.

Leading to viral replication and inflammation in the brain tissue.

33
Q

Which brain region does HSV-1 affect? As a result, what symptoms are caused?

A

Temporal lobes of the brain, including the hippocampus and amygdala.

These areas are crucial for memory and emotional processing, explaining the cognitive and behavioral symptoms often seen in HSE patients.

34
Q

What are some arboviruses that can cause encephalitis?

A

West Nile virus, Japanese encephalitis virus, tick-borne encephalitis virus

35
Q

What may precipitate encephalitis?

A

Recent infection causing post-Infectious Encephalitis: Immune-mediated inflammation occurs after the body has fought off an initial infection, leading to demyelination and white matter damage.

36
Q

Which type of encephalitis involve auto-antibodies? Give and example of an antibodiy

A

Auto-immune encephalitis. Anti-NMDA

37
Q

List 2 causes that may trigger anti-NMDA encephalitis?

A
  • HSV-1
  • Ovarian teratomas

Treat with immunotherapy

38
Q

How does encephalitis generally present?

Think neuropsychiatry

A

Acute onset of psychiatric symptoms/altered mental state such as confusion/agitation/hallucinations/behavioural changes + ** seizures/ focal neurological signs ** e.g. hemiparesis, hyperrefleia, weakness, aphasia

39
Q

If a patient with suspected encephalitis starts jerking uncontrollably, what do you think has happened? How can you manage them?

A

Seizure. Manage with anti-epileptics.

40
Q

What prodromal symptoms might occur before encephalitis?

A
  • Fever
  • Headache
  • Rash
  • Nausea and vomiting
41
Q

Which diagnostic tests are performed to confirm encephalitis? Which one is diagnostic?

A
  • Blood tests: same for suspecting infection, cultures
  • CSF — diagnostic
  • MRI — clear picture
42
Q

What is the role of cerebrospinal fluid (CSF) analysis in diagnosing encephalitis?

A

Similar to meningitis – determine infection in the brain e.g. elevated white blood cell count, elevated protein, and sometimes the presence of specific pathogens through PCR or culture

43
Q

What are some long-term complications of encephalitis?

A
  • Cognitive impairment, behavioural and psychiatric problems
  • Motor deficits, hearing or vision loss, speech and language disorders
  • Recurrent seizures/ epilepsy
44
Q

What are the treatment options for viral encephalitis?

A

Treatment often includes antiviral medications (e.g., acyclovir for HSV) —started empirically for a suspected case, supportive care, and management of complications e.g. as seizures and increased intracranial pressure

45
Q

When should treatment be started for suspected meningitis and encephalitis ?

A

Immediatebly upon clinical suspicion, due to potentially life-threatening consequences e.g. coma, extensive damage and death.

Admit to hospital if not already.

46
Q

List 3 way how increased intracranial pressure is managed in patients with encephalitis.

A
  • Head elevation,
  • Fluid balance
  • osmotic diuretics (e.g., mannitol), hypertonic solution
47
Q

What are some specific risk factors for contracting viral encephalitis?

A
  • certain age groups (e.g., young children and the elderly)
  • Immunosuppressed people, and
  • in regions where specific pathogens are endemic

e.g. Japanese encephalitis is predominantly found in rural areas of Asia and parts of the Western Pacific. West Nile virus is more commonly found in Africa, Europe, the Middle East, North America, and West Asia.

48
Q

If a patient comes in with a few days of headache, low-grade fever, and neck stiffness, nausea, and some weakness in one limb, following an unresolving ear infection. What would you suspect? How would you confirm it?

A

Brain abscess. Cofirmed through CT - ring enhancing lesion with hypodense centre (necrotic)

49
Q

How do brain abscesses start and develop?

A

Cerbritis eventually causing inflammation and necrosis.

50
Q

Management of brain abscesses.

Which antibiotics are first-line?
What is a definitive treatment if the abscess is large e.g. >2.5 cm

A

1st line: empiral antibiotics cephalosporin and metronidazole

Definitive treatment: craniotomy with drainage.

Steroids and antiepileptic drugs may be used if needed.

Medical conditions (13 decks)

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