CNS Infections — MCQs
A 29-year-old patient presents with focal seizures. MRI shows frontal and temporal enhancement. What is the most probable diagnosis?
Symptomatic neonatal CNS involvement is most commonly seen in which group of congenital intrauterine infections?
A mother brings her 1-month-old infant to the pediatrician. She says the baby is crying more than usual and is vomiting and does not want to eat. Meningitis is suspected, and a lumbar puncture is done, which shows the following results; Opening pressure = 240 mm H2O (normal = 100-200 mm H2O), WBC count: 1200/mm3, Protein: 200 mg/dL, Glucose: 30 mg/dL, Gram stain: gram-positive rods, Which of the following organisms is most likely responsible for this infant's meningitis?
Which of the following statements about the CSF findings in pyogenic meningitis is true?
A baby born at 32 weeks gestation with Apgar scores of 2 and 7 was placed in the neonatal intensive care unit. She developed a fever and leukocytosis; lumbar puncture revealed pleocytosis with increased protein, decreased glucose, and gram-positive rods. Which one of the following organisms was most likely isolated from the CSF?
Neurological complications of meningitis include all of the following except:
A 6-year-old with recurrent febrile seizures presents lethargic with a high fever. What is the most appropriate next step in management?
Which of the following electrolyte abnormalities is a cause of status epilepticus in a child?
Symptomatic neonatal CNS involvement is most commonly seen in which group of congenital intrauterine infections?
A child presents with myoclonic jerks and decreasing school performance. The child had a history of fever and rash at the age of 1 year. What is the most likely diagnosis?
CNS Infections Indian Medical PG Practice Questions and MCQs
Question 1: A 29-year-old patient presents with focal seizures. MRI shows frontal and temporal enhancement. What is the most probable diagnosis?
- A. Herpes simplex encephalitis (Correct Answer)
- B. Enterovirus encephalitis
- C. Japanese encephalitis
- D. Meningococcal meningitis
Explanation: ***Herpes simplex encephalitis*** - **Herpes simplex encephalitis (HSE)** characteristically causes inflammation and damage in the **frontal** and **temporal lobes**, leading to focal neurological deficits and seizures [1]. - MRI findings of **enhancement** in these specific brain regions are highly suggestive of HSE. *Enterovirus encephalitis* - **Enterovirus encephalitis** typically affects a broader range of brain regions and less commonly presents with the focal frontal and temporal enhancement seen in HSE. - While it can cause seizures, the MRI findings are not as specific for this diagnosis. *Japanese encephalitis* - **Japanese encephalitis** is geographically restricted to parts of Asia and is transmitted by mosquitoes. The clinical presentation typically includes diffuse encephalitic symptoms rather than focal frontal/temporal involvement and enhancement on MRI. - This diagnosis would be unlikely without a relevant travel history and exposure. *Meningococcal meningitis* - **Meningococcal meningitis** is an infection of the **meninges**, the membranes surrounding the brain and spinal cord, not primarily the brain tissue itself. - MRI would typically show inflammation and enhancement of the meninges, rather than focal parenchymal (brain tissue) enhancement in the frontal and temporal lobes.
Question 2: Symptomatic neonatal CNS involvement is most commonly seen in which group of congenital intrauterine infections?
- A. Rubella and toxoplasmosis
- B. CMV and syphilis
- C. Rubella and HSV
- D. CMV and toxoplasmosis (Correct Answer)
Explanation: ***CMV and toxoplasmosis*** - Both **cytomegalovirus (CMV)** and **Toxoplasma gondii** are well-known causes of congenital infections that frequently lead to significant and symptomatic central nervous system (CNS) involvement in neonates. - Congenital CMV can cause **microcephaly**, **periventricular calcifications**, **hearing loss**, and developmental delay, while congenital toxoplasmosis can result in **hydrocephalus**, **intracranial calcifications**, **chorioretinitis**, and seizures. *Rubella and toxoplasmosis* - While **toxoplasmosis** causes significant CNS involvement, **congenital rubella syndrome** typically presents with cataracts, heart defects (e.g., patent ductus arteriosus), and hearing loss, with CNS involvement being less consistently severe or frequently symptomatic in the immediate neonatal period compared to CMV or toxoplasmosis. - Although rubella can cause **encephalitis** or **meningoencephalitis**, these are not as common or consistently severe as the direct destructive CNS lesions seen with CMV or toxoplasmosis. *CMV and syphilis* - **CMV** is a major cause of neonatal CNS symptoms. However, **congenital syphilis** primarily affects bones, skin, and mucous membranes (e.g., "snuffles"), with CNS involvement typically presenting as **meningitis**, **hydrocephalus**, or neurodevelopmental delays, but often not as overtly symptomatic in the immediate neonatal period as CMV or toxoplasmosis. - While syphilis can cause neurosyphilis, the spectrum and severity of immediate symptomatic CNS involvement are distinct from the widespread calcifications and structural abnormalities seen with CMV or toxoplasmosis. *Rubella and HSV* - **Rubella** primarily causes classic congenital defects in eyes, ears, and heart, with CNS effects being less common and severe. - **Congenital herpes simplex virus (HSV)** infection, while causing severe CNS disease (e.g., encephalitis) when disseminated, is relatively rare overall compared to CMV and toxoplasmosis, and often presents with skin, eye, and mouth lesions first.
Question 3: A mother brings her 1-month-old infant to the pediatrician. She says the baby is crying more than usual and is vomiting and does not want to eat. Meningitis is suspected, and a lumbar puncture is done, which shows the following results; Opening pressure = 240 mm H2O (normal = 100-200 mm H2O), WBC count: 1200/mm3, Protein: 200 mg/dL, Glucose: 30 mg/dL, Gram stain: gram-positive rods, Which of the following organisms is most likely responsible for this infant's meningitis?
- A. Neisseria meningitidis
- B. Streptococcus agalactiae
- C. Escherichia coli
- D. Listeria monocytogenes (Correct Answer)
Explanation: ***Listeria monocytogenes*** - The presence of **gram-positive rods** in the CSF of a 1-month-old infant with meningitis, coupled with the classic CSF findings (high WBC, high protein, low glucose), is highly suggestive of *Listeria monocytogenes*. - This organism is a significant cause of **neonatal meningitis** and is known for its rod-shaped morphology. *Neisseria meningitidis* - This organism is a **gram-negative diplococcus**, which is inconsistent with the gram stain result of **gram-positive rods**. - While it causes meningitis, its typical presentation and Gram stain morphology differ significantly. *Streptococcus agalactiae* - Also known as **Group B Streptococcus (GBS)**, this is a common cause of neonatal meningitis but is characterized as **gram-positive cocci in chains**, not rods. - The gram stain finding rules out GBS in this case. *Escherichia coli* - *E. coli* is a **gram-negative rod** and can cause neonatal meningitis. - However, the CSF gram stain in this case indicated **gram-positive rods**, which rules out *E. coli*.
Question 4: Which of the following statements about the CSF findings in pyogenic meningitis is true?
- A. CSF contains no organisms
- B. CSF is sterile and clear
- C. Glucose is decreased and protein is elevated (Correct Answer)
- D. Chloride is decreased and glucose is normal
Explanation: ***Glucose is decreased and protein is elevated*** - In **pyogenic (bacterial) meningitis**, bacteria consume glucose, leading to a **decreased CSF glucose** level. [1] - The inflammatory response increases the permeability of the blood-brain barrier, allowing proteins to leak into the CSF, resulting in **elevated CSF protein**. [1] *CSF contains no organisms* - This statement is incorrect; **pyogenic meningitis** is caused by bacterial infection, and therefore, **bacteria (organisms)** are typically present in the CSF. [1] - Microscopic examination and culture of the CSF are crucial for identifying the causative organism. [1] *CSF is sterile and clear* - CSF in **pyogenic meningitis** is **not sterile** due to the presence of bacteria, and it is typically **turbid or cloudy** due to the high leukocyte count. [1] - A clear and sterile CSF would suggest the absence of bacterial infection or a very early stage of viral meningitis. [1] *Chloride is decreased and glucose is normal* - While **CSF chloride** might be slightly decreased in severe meningitis cases, it is not a primary diagnostic marker, and **glucose is typically decreased**, not normal, in pyogenic meningitis. - **Normal CSF glucose** with decreased chloride might be observed in other conditions, but not typically in established pyogenic meningitis. **References:** [1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Manifestations Of Central And Peripheral Nervous System Disease, pp. 708-709.
Question 5: A baby born at 32 weeks gestation with Apgar scores of 2 and 7 was placed in the neonatal intensive care unit. She developed a fever and leukocytosis; lumbar puncture revealed pleocytosis with increased protein, decreased glucose, and gram-positive rods. Which one of the following organisms was most likely isolated from the CSF?
- A. Escherichia coli
- B. Neisseria meningitidis
- C. Streptococcus agalactiae
- D. Listeria monocytogenes (Correct Answer)
Explanation: ***Listeria monocytogenes*** - This organism is a common cause of **meningitis in neonates**, often acquired transplacentally or during birth, and presents with gram-positive rods. - The patient's **prematurity**, low Apgar scores, fever, and CSF findings of **pleocytosis, increased protein, and decreased glucose** are highly characteristic of bacterial meningitis, and *Listeria* specifically. *Escherichia coli* - While *E. coli* is a frequent cause of **neonatal meningitis**, it typically presents as **gram-negative rods**, not gram-positive. - The clinical presentation is consistent with bacterial meningitis, but the Gram stain result rules out *E. coli* as the most likely pathogen. *Neisseria meningitidis* - *N. meningitidis* causes bacterial meningitis, but it is characterized by **gram-negative cocci**, not gram-positive rods. - This organism is more commonly associated with meningitis in older infants, children, and young adults, rather than premature neonates. *Streptococcus agalactiae* - *Streptococcus agalactiae* (Group B Strep) is a major cause of **early-onset neonatal sepsis and meningitis**, characterized by **gram-positive cocci in chains**, not rods. - While clinically plausible given the neonatal presentation, the Gram stain finding of "gram-positive rods" makes it less likely than *Listeria monocytogenes*.
Question 6: Neurological complications of meningitis include all of the following except:
- A. Increased intracranial pressure
- B. Brain abscess
- C. Subdural effusions
- D. Cerebral hamartoma (Correct Answer)
Explanation: Cerebral hamartoma - A cerebral hamartoma is a benign, tumor-like malformation of abnormally organized mature brain tissue; it is a developmental anomaly and not a complication of meningitis. - Unlike the other options, it does not represent an inflammatory, infectious, or pressure-related sequela of meningeal infection. Increased intracranial pressure - Increased intracranial pressure (ICP) is a common and serious complication of meningitis due to cerebral edema, hydrocephalus, or vasodilation. - Elevated ICP can lead to herniation, neurological deficits, and even death if not managed promptly. Brain abscess - A brain abscess is a localized collection of pus within the brain parenchyma that can develop as a focal complication of bacterial meningitis, particularly in cases of hematogenous spread or direct extension of infection [1]. - This serious condition causes focal neurological deficits and requires aggressive treatment. Subdural effusions - Subdural effusions are accumulations of sterile or infected fluid in the subdural space, most commonly seen in infants and young children with bacterial meningitis. - While they can be asymptomatic, large effusions may cause increased ICP or focal neurological signs requiring drainage.
Question 7: A 6-year-old with recurrent febrile seizures presents lethargic with a high fever. What is the most appropriate next step in management?
- A. Perform lumbar puncture (Correct Answer)
- B. Consider using antipyretics for comfort
- C. Start anticonvulsants
- D. Order urgent EEG
Explanation: ***Perform lumbar puncture*** - The combination of **lethargy**, high fever, and a history of recurrent febrile seizures in a 6-year-old child raises suspicion for **meningitis or encephalitis**, necessitating a prompt **lumbar puncture** to analyze **cerebrospinal fluid (CSF)**. - While febrile seizures alone are benign, **altered mental status (lethargy)** in conjunction with fever is a red flag for **central nervous system infection**. *Consider using antipyretics for comfort* - **Antipyretics** can help reduce fever and improve comfort but do not address the underlying cause of lethargy and potential CNS infection. - Delaying definitive diagnostic steps like a **lumbar puncture** while waiting for antipyretics to work could worsen the patient's prognosis if a serious infection is present. *Start anticonvulsants* - **Anticonvulsants** are primarily used for managing ongoing seizures or preventing recurrent non-febrile seizures but are **not indicated as a first-line diagnostic or emergency treatment** for a child presenting with **fever and lethargy without active seizures**. - There is no clinical indication of current seizure activity, and the immediate concern is detecting a potential **CNS infection**. *Order urgent EEG* - An **EEG (electroencephalogram)** is useful for evaluating seizure disorders or encephalopathy but is **not the most appropriate initial diagnostic step** when a **serious CNS infection like meningitis** is suspected. - A **lumbar puncture** is crucial for diagnosing or ruling out meningitis, which requires immediate treatment.
Question 8: Which of the following electrolyte abnormalities is a cause of status epilepticus in a child?
- A. Hypokalemia
- B. Hyperkalemia
- C. Hypernatremia
- D. Hyponatremia (Correct Answer)
Explanation: ***Hyponatremia*** - **Hyponatremia** (low sodium levels) can lead to **cerebral edema**, increasing intracranial pressure and predisposing to seizures, including status epilepticus, especially in children. - Rapid shifts in fluid balance and electrolyte disturbances, such as those seen with severe hyponatremia, can destabilize neuronal membranes and trigger **sustained seizure activity**. *Hypokalemia* - While significant **hypokalemia** (low potassium) affects cardiac and muscular function, it is **less commonly a direct cause of seizures** or status epilepticus compared to sodium imbalances. - Severe hypokalemia can impact neuronal excitability but primarily causes **muscle weakness** and **cardiac arrhythmias**. *Hyperkalemia* - **Hyperkalemia** (high potassium) primarily affects **cardiac conduction** and neuromuscular function, leading to **bradycardia** or **cardiac arrest**. - It is **not typically associated with seizures** or status epilepticus in children. *Hypernatremia* - **Hypernatremia** (high sodium) indicates a relative water deficit, leading to cell shrinkage and potentially **intracranial hemorrhage** or **thrombosis**. - While severe hypernatremia can cause neurological symptoms like **lethargy** or **coma**, it is **less commonly a direct cause of status epilepticus** compared to hyponatremia.
Question 9: Symptomatic neonatal CNS involvement is most commonly seen in which group of congenital intrauterine infections?
- A. Rubella and HSV
- B. CMV and Toxoplasmosis (Correct Answer)
- C. CMV and Syphilis
- D. Rubella and Toxoplasmosis
Explanation: ***CMV and Toxoplasmosis*** - **Cytomegalovirus (CMV)** is the **most common congenital infection** causing symptomatic neonatal CNS involvement, affecting 0.5-2% of live births and being the leading cause of non-genetic sensorineural hearing loss and neurological disability. - CMV causes **microcephaly, periventricular intracranial calcifications, ventriculomegaly, seizures**, and developmental delay. - **Toxoplasmosis** is the second most common, presenting with the classic triad of **hydrocephalus, diffuse intracranial calcifications, and chorioretinitis**. - Together, these two represent the **most frequently encountered** causes of symptomatic congenital CNS disease. *Rubella and HSV* - While both can cause neurological complications, they are **not the most common** causes of congenital CNS involvement. - **Rubella** is now rare due to widespread vaccination programs. - **HSV** as a true **congenital intrauterine infection is extremely rare**; most neonatal HSV is acquired **perinatally during delivery** or postnatally, not as a congenital infection. *Rubella and Toxoplasmosis* - While **Toxoplasmosis** is indeed a common cause of congenital CNS disease, **Rubella** is now uncommon due to vaccination. - This combination doesn't represent the most frequently seen pair compared to CMV and Toxoplasmosis. *CMV and Syphilis* - **CMV** is correct as the most common cause, but **Syphilis** primarily causes multi-system involvement including hepatosplenomegaly, skin rashes, and bone abnormalities. - While **neurosyphilis** can occur, CNS involvement is less consistently present compared to **Toxoplasmosis**, which characteristically causes the classic triad with prominent CNS features.
Question 10: A child presents with myoclonic jerks and decreasing school performance. The child had a history of fever and rash at the age of 1 year. What is the most likely diagnosis?
- A. Measles
- B. Subacute sclerosing panencephalitis (SSPE) (Correct Answer)
- C. Mesial temporal sclerosis
- D. Polio
Explanation: ***Subacute sclerosing panencephalitis (SSPE)*** - SSPE is a **rare, progressive, and fatal neurodegenerative disease** caused by persistent measles virus infection of the central nervous system. - The presentation of **myoclonic jerks** (stage 2 SSPE) and **decreasing school performance** (stage 1 - cognitive decline) in a child with a history of measles (fever and rash) at 1 year of age is **pathognomonic** for SSPE. - SSPE typically manifests **7-10 years after measles infection**, with male predominance (M:F = 2-4:1). - EEG shows characteristic **Radermecker complexes** (periodic high-amplitude slow wave complexes). - CSG findings include elevated measles antibodies with high CSF:serum antibody ratio. *Measles* - While the child had measles in infancy, the current neurological symptoms are **not acute measles** but rather a late complication (SSPE). - Acute measles is a self-limiting illness; these progressive neurological symptoms occurring years later indicate SSPE, not active measles. *Mesial temporal sclerosis* - This is the most common cause of **drug-resistant temporal lobe epilepsy** characterized by hippocampal atrophy. - Presents with **focal seizures with impaired awareness**, not generalized myoclonic jerks. - **No link to prior measles infection** and typically associated with history of febrile seizures or status epilepticus in childhood. - Progressive cognitive decline is not a primary feature. *Polio* - Polio is caused by **poliovirus** affecting anterior horn cells of the spinal cord, causing **acute flaccid paralysis**. - Presents with **asymmetric lower motor neuron weakness**, not myoclonic jerks or cognitive decline. - **No association with measles** or rash in history. - Would not cause the progressive encephalopathy seen in this case.
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