A 10 year old previously healthy male presents after 24 hours of non-remitting headache, intractable vomiting, and fevers to 104.1F at home. Mother brought the patient to the ED after symptoms continued to worsen, and she noticed him moving his neck less. No recent travel, but he did go to a sleepover recently and notes that one of the friends there had a “GI bug.” Given his symptoms, a lumbar puncture is performed, and the fluid obtained is noted to be clear and colorless with an opening pressure of 30 mmH20, WBC of 200, predominantly lymphocytes, protein low at 80 mg/dl, and glucose slightly elevated to 60 mg/dl. Serum glucose was 85. Given these results, what is the most likely etiology of this child’s symptomatology?
A. Bacterial meningitis
B. Subarachnoid hemorrhage
C. Fungal meningitis
D. Viral meningitis
E. Tuberculous meningitis
The correct answer is D, Viral Meningitis.
Answer Choice A: Bacterial Meningitis
This answer is incorrect given the CSF profile. The opening pressure in cases of bacterial meningitis is typically much higher than viral with a turbid appearance of the fluid and high protein count with low glucose and leukocytosis with neutrophilic predominance. It is important to note that a viral meningitis may have a neutrophilic predominance if caught very early in the disease course. The CSF to serum glucose ratio can be calculated from the question stem and is typically <0.4 in bacterial, fungal, and tubercular meningitis compared to a typical ratio of >0.6 with viral meningitis. The most common causes of meningitis vary by age group:
-Newborns are at the highest risk for Group B Streptococcus (Streptococcus agalactiae), Listeria monocytogenes, E. coli, and Klebsiella.
-The most common pathogens seen in toddlers and children are Streptococcus pneumoniae, Neisseria meningitidis, and Haemophilus influenzae Type B (although this is significantly decreased with vaccinations).
-Teens most commonly are affected by Neisseria meningitidis and Streptococcus pneumoniae.
Answer Choice B: Subarachnoid Hemorrhage
This answer is incorrect. The signs of an acute subarachnoid hemorrhage can include sudden and severe headache, vomiting, lethargy, weakness or paralysis, new-onset seizure, loss of consciousness, or altered mental status. Keys in the question stem that lead away from this as the correct answer are notably the fever and viral prodrome. Additionally, the lumbar puncture would likely be grossly bloody or xanthochromic but may otherwise have normal indices.
Answer Choice C: Fungal Meningitis
This answer choice is also incorrect given the CSF profile and the presenting fact that this patient was overall healthy prior to sudden disease onset. Fungal meningitis is more likely to occur in immunocompromised patients. CSF profile in a patient with fungal meningitis will have a slightly elevated protein count, slightly decreased glucose (similar to bacterial meningitis) and a mild leukocytosis made up of predominantly monocytes (similar to viral meningitis). Fungal and tuberculous meningitis are essentially indistinguishable at this level. Because of this, you can essentially eliminate both answer choices C and E!
Answer Choice D: Viral Meningitis
If you guessed this answer choice, you are correct! Overall, viral meningitis is the most common cause of meningitis and the clinical presentation as well as the lab findings of CSF analysis are consistent with this picture. Of all of the viruses, Enteroviruses are the most common cause of viral meningitis across all age groups with Parechoviruses being the next most common in children. Herpesviruses that cause meningitis include Herpes simplex virus (HSV) types 1 and 2, Varicella-zoster virus (VZV), Cytomegalovirus (CMV), Epstein-Barr virus (EBV), and Human herpesvirus 6 (HHV6). Other viral causes include Adenovirus, Lymphocytic Choriomeningitis virus (LCMV), Influenza, Parainfluenza, and Mumps. There are more than 100 arthropod-borne viruses (commonly known as Arboviruses) that cause disease. The most common of these that can cause viral meningitis, encephalitis, or a combination of the two include West Nile virus, LaCrosse virus, and Saint Louis virus. These will typically present with a viral prodromal period of headaches, arthralgias, myalgias, and rash, followed by neurologic symptoms of vomiting, stiff neck, or even mental status changes and seizures.
Answer Choice E: Tuberculous Meningitis
As mentioned previously, this answer choice is also incorrect and would be very difficult to distinguish from fungal meningitis. Tuberculous meningitis may also have a xanthochromic, fibrinous, or opaque color to the fluid whereas fungal can have the fibrin appearance but is more likely to appear clear like viral meningitis. Tuberculous meningitis is most commonly found in children 1-5 years old. There are very few bacteria that cause an aseptic meningitis, and they include Mycobacterium tuberculosis (TB), Borrelia burgdorferi (Lyme disease), and Treponema pallidum (Syphilis). The classic “RIPES” regimen with rifampin, isoniazid, pyrazinamide, ethambutol, and streptomycin would be the standard therapy for at least 9 months for these patients.
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