I have a couple of these patients a year. Please see ... Asano Y et al. Clinical features of
infants wtih primary human herpesvirus 6 infection. Pediatrics 1994;93:104-8. They describe a
series of 176 patients with serologically confirmed HHV6 infections- 26% had a bulging fontanel.
I believe this falls under the realm of pseudotumor cerebri or something like it. I think I once
read that CSF absorption at the arachnoid villi may be temporarily impaired or something.
Regarding the C-spine issue... The 'classic teaching' is that the sensitivity of a diagnostic
test does not vary with disease prevalence. This means that the lateral c-spine should perform
with the same sensitivity regardless of disease prevalence and one would assume, clinical
presentation. Disdaining 'classic teachings', I have heard experts explain in terms more sublime
than I can produce, that this is not exactly mathematically correct There is also the issue of
spectrum bias. Spectrum bias observes that the sensitivity of a test varies with the timing of
disease presentation, eg peripheral WBC in acute appendicitis ( early, low sensitivity, later,
higher sensitivity). However, since 'awake, alert', patients are less likely to have distraction
injuries that one could clearly see on lateral c-spine, I would expect the sensitivity of lateral
c-spine to be lower, if anything, in the group you describe. Of course, since the prevalence of
c-spine fracture in 'awake, alert' patients is lower than the entire c-spine fracture population
as a whole, the negative predictive value of a negative lateral c-spine would be slightly higher.
jay pershad wrote:
> Had another one of these! Probably the fourth or fifth of my brief career. A
> febrile infant (8 month old) with a bulging fontanelle (noted by the parent
> & confirmed by examining the baby sitting up with the baby not crying);
> somewhat fussy but not "irritable". CSF was "stone cold" normal. The patient
> looked well post tap.
> I have chosen to call it the "Benign Bulging Anterior Fontanelle" syndrome.
> Have folks seen this? What is the mechanism?
> BTW, Jay (Fischer, MD) thanks for the references on C-Spine. I guess my
> question is, what is the sensitivity of a lateral radiograph in a completely
> lucid patient, with no distracting injuries, a non focal neurologic exam and
> no midline c-spine tenderness, in a preverbal child. It is this age group,
> where getting a good "odontoid" view is an ordeal. The frequently quoted
> sensitivity of 70-80 % I believe, includes all comers, i.e even those who
> may under the influence, have AMS etc ....etc.
> Jay Pershad, MD
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