For a child with a fever who has an altered level of consciousness, the differential diagnosis is considerable. The possibility of a viral etiology must always be entertained, especially with environmental exposure to specific vector-borne diseases. However, given the family's precautions regarding regular tick inspections, coupled with insect repellent use, the likelihood of a vector-borne disease is less likely than other diagnoses.
As for herpes simplex encephalitis, typical CSF findings include lymphocytic pleocytosis, normal glucose levels, and increased protein levels. The low glucose level and the lack of a lymphocytic pleocytosis in this patient are important findings that suggest an alternative diagnoses.
Regarding rabies meningoencephalitis, the patient's history did not suggest any type of exposure to a possibly rabid animal. The evolution of this child's symptoms was a progressive one, not the waxing and waning symptomatology that is classically seen with "furious" rabies. Moreover, he had no history of hydrophobia or aerophobia. Finally, the characteristic CSF findings in human rabies are lymphocytosis and normal glucose levels, values not consistent with N fowleri meningoencephalitis.[3,4,5]
The CSF findings of an elevated protein level and a low glucose level in this patient are more consistent with a bacterial infection. In fact, the low incidence of primary amebic meningoencephalitis (PAM) may be attributable to its misdiagnosis as bacterial meningitis.[6,7] However, with bacterial meningoencephalitis, Gram staining would be expected to yield a bacterial etiology. In this case, the results of Gram staining were negative.
The characteristic CSF findings associated with a rickettsial infection include pleocytosis with a WBC count that is usually less than 100/µL, as well as a moderately increased protein level and a normal glucose level. Such findings were not seen in this patient.
A more in-depth analysis of the history of the boy's diving and snorkeling in a warm freshwater lake prompted additional CSF testing. A wet preparation of the CSF revealed amebic microorganisms. Giemsa and trichrome staining of wet samples may show the organisms in real time. Polymerase chain reaction testing can confirm the initial findings.[8,9] Results of a CT scan may be normal early in the course of the disease, as it was in this case.
Medscape © 2023 WebMD, LLC
Any views expressed above are the author's own and do not necessarily reflect the views of WebMD or Medscape.
Cite this: Paul P. Rega. 13-Year-Old Boy Unaware of His Surroundings - Medscape - Sep 14, 2023.