A Worm's Tale or Why to Avoid the Raccoon Latrine: A Case of Baylisascaris procyonis Meningoencephalitis

Abstract

The raccoon roundworm Baylisascaris procyonis (B. procyonis) may infect humans to cause severe or fatal meningoencephalitis, as well as ocular and visceral larva migrans. Young children are at greater risk for cerebral larva migrans with severe meningoencephalitis, and early empiric therapy may improve outcomes. Familiarity with characteristic brain imaging findings may prompt earlier diagnosis, particularly in the setting of CSF eosinophilia. We report a case of a 19-month-old boy who presented with truncal ataxia and was found to have peripheral and CSF eosinophilia. MRI demonstrated symmetric, confluent T2 hyperintense signal in the cerebral and cerebellar deep white mater, which helped differentiate B. procyonis meningoencephalitis from other infectious and non-infectious causes of eosinophilic meningoencephalitis. Early recognition and treatment of B. procyonis meningoencephalitis are important for improved outcomes, and careful review of neuroimaging can play a critical role in suggesting the diagnosis.

Figure 1

MRI obtained on admission demonstrating diffuse confluent symmetric T2 FLAIR hyperintensities in the supratentorial periventricular and deep white matter, sparing the subcortical U fibers, and in bilateral cerebellar hemispheres around the deep nuclei (a–c). A focus of T2 FLAIR hyperintensity is noted in the lateral left thalamus (arrow in (b)). Postcontrast images reveals punctiform and curvilinear enhancement centered in bilateral supratentorial periventricular white matter with a perivascular distribution pattern (arrows in (d)). Foci of faint and curvilinear enhancement (arrow in (f)) were also present in bilateral cerebellar white matter. Small curvilinear enhancement was noted in the lateral left thalamus, likely reflective of a vein or a perivenous process (arrow in (e)).

Figure 2

MRI obtained 10 days after admission demonstrating mild progression in diffuse white matter T2 FLAIR hyperintensity (a–c) with slightly increased involvement of the left lateral thalamus (arrow in (b)). Previously noted punctiform enhancement in the supratentorial periventricular white matter has nearly resolved with minimal residual curvilinear enhancement, possibly vessels (arrows in (d)). Small curvilinear enhancement is again seen in the left thalamus (arrow in (e)). Prior curvilinear enhancement in the cerebellum had resolved with interval development of few new punctiform cerebellar enhancing foci (arrows in (f)).