Haemophilus Meningitis Differential Diagnoses

Updated: Mar 02, 2016
  • Author: Pranatharthi Haran Chandrasekar, MBBS, MD; Chief Editor: Niranjan N Singh, MD, DM  more...
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DDx

Diagnostic Considerations

Rashes are much more commonly associated with such differential considerations as Neisseria meningitidis meningitis, Rocky Mountain spotted fever, subacute bacterial endocarditis, and viral (eg, echovirus 9) meningoencephalitis than with Haemophilus influenzae type b (Hib) meningitis. In these diseases, the rash is typically erythematous and macular or maculopapular at onset and may quickly progress to petechia and purpura. Note that rashes of this sort are occasionally observed in Hib encephalitis.

Hemiconvulsive seizures at presentation with low-grade fever may necessitate the exclusion of Hashimoto encephalopathy. Focal or hemiconvulsive seizures in children may suggest such alternative diagnoses as herpes I, LaCrosse, Japanese B, or other forms of encephalitis, depending on time of year, region of the world, and historical exposures.

Most children younger than 18 months who present with a history of fever and seizures but who have normal findings on examination (including reliable exclusion of meningismus) do not have meningitis. One study showed that the risk for meningitis in such infants is approximately 1.2%. Of the 4 children in that study who did have meningitis, 3 had viral and 1 had Hib meningitis. Children older than 18 months who present with a history of fever and a seizure but who have normal examination findings are even less likely to have meningitis.

Seasonal variation in incidence of Hib meningitis

Time of year is an important factor in differentiating Haemophilus influenzae type b (Hib) meningitis from cases due to the other 2 major causes of human meningitis, N meningitidis and Streptococcus pneumoniae. Hib meningitis has a bimodal distribution, with the first peak in June and the second in September to October. In contrast, the incidence of meningococcal and pneumococcal meningitis is greatest in the winter months.

The increased Hib prevalence in summertime corresponds somewhat, but not exactly, to the period of highest prevalence of arboviral encephalitis, aseptic meningitis, enteric encephalitides such as poliomyelitis or coxsackie encephalitis, and tick-borne encephalitides such as Lyme disease or Rocky Mountain spotted fever. Many of these differential considerations have their highest prevalence in July to August.

Other problems to be considered

Other problems to be considered in the differential diagnosis of Hib meningitis are the following:

  • Brain abscess
  • Posterior fossa subdural or subdural empyema
  • Sepsis
  • Typhus
  • Cerebral malaria
  • Fungal meningitis
  • Carcinomatous meningitis

Differential Diagnoses