To describe two cases of raccoon roundworm encephalomyelitis, identify important features to aid in early diagnosis, and contrast outcomes of early versus late treatment.

Baylisascaris procyonis, transmitted via raccoon fecal matter, is a rare cause of ocular and cerebral larva migrans, and has been associated with potentially fatal eosinophilic meningoencephalitis. Highest risk populations include young children and individuals with developmental disabilities and/or pica. Treatment requires antiparasitic agents and steroids. 

Patient one is a teenager with autism and pica who presented with one week of encephalopathy, ataxia, and left gaze preference. MRIs showed numerous enhancing brain lesions as well as patchy non-enhancing myelitis. A mild CSF pleocytosis (15% eosinophils) and known raccoon exposure raised suspicion for Baylisascaris procyonis. Retinal exam revealed unilateral neuroretinitis and a nematode, which was then laser ablated. We initiated steroids and high dose albendazole within two weeks. He recovered well with normalization of his neurologic exam and cognitive improvement to 80% of baseline.  

Patient two was a previously healthy toddler who presented subacutely with ataxia, progressive encephalopathy, loss of all milestones, and severe hypertonia. He was treated at multiple hospitals for presumed atypical ADEM with steroids, IVIg, plasmapheresis, and rituximab. On our initial evaluation three months after symptom onset, we noted that his MRI, CSF, and ophthalmologic findings were nearly identical to those of patient one. The still viable retinal nematode was laser ablated, and we initiated albendazole with steroids. Unfortunately, the patient has had limited recovery with severe spastic quadriparesis and neurocognitive impairment.

Baylisascaris procyonis is a rare but important mimic of ADEM, and can also present with myelitis and neuroretinitis. Diagnostic clues include raccoon exposure, peripheral eosinophilia, and eosinophilic CSF pleocytosis in toddlers or individuals with pica.  These two cases highlight the importance of early diagnosis and treatment, which may improve outcomes.