The Pivotal Role of MRI in the Diagnosis of Listeria Rhomboencephalitis

Sixty-six year-old female presented to the Emergency Department with history of several days of headache, malaise, chills, and fatigue with accompanying nausea, vomiting, and inability to tolerate oral intake. She had no history of fever and remained afebrile at the time of presentation. Physical exam and immediate lab values were non-contributory; CSF was obtained and sent for analysis. The patient was placed preemptively on acyclovir, as viral meningitis was the admitting diagnosis. MRI of the brain showed abnormal FLAIR signal hyperintensity and enhancement involving the entire cisternal segment of the left trigeminal nerve, which extended dorsally along the nerve fiber tracks to the left trigeminal nucleus. Abnormal signal extended inferiorly from this nucleus to the left cerebellomedullary junction and upper cervical cord. Extensive involvement of the trigeminal nerve, brain stem along with CSF findings of lymphocytosis, increased protein and decreased glucose made listeria rhombencephalitis the most likely diagnosis. This was confirmed later by positive CSF growth on the 5th day of the admission. Listeria is the third leading cause of foodborne related death in US with case fatality rate of 20%. Delay in the early diagnosis increases the associated morbidity and mortality, as the pathogen respond only to the few particular drugs, which typically are not included in the empirical therapy. Specific diagnoses with blood/CSF culture are negative in 40% of the cases with additional challenge added by nonspecific clinical history. The specific tropism of the bacteria for the brainstem and cerebellum with specific imaging findings on MRI are pivotal in early diagnosis. This understanding fosters improved care and deceased morbidity and mortality in this patient population