Purpose or Case Report: Background:

Pediatric acute-onset neuropsychiatric syndrome (PANS) is a rare neuroinflammatory entity that is often associated with infectious and non-infectious triggers. This condition was first associated with recent Streptococcal infections (PANDAS) in the late 1990s. PANS manifests with sudden obsessive-compulsive disorder and/or restricted food intake with additional neuropsychiatric abnormalities. Children with PANS demonstrate generalized increased median diffusivity in the brain, more prominently in the deep gray matter, including the thalami, basal ganglia, and amygdala. Although neuroimaging plays a supportive role in diagnosis, its use is limited by the lack of positive findings in cases with clinically diagnosed PANS.

Purpose:

We aim to showcase brain MRI findings in a child with a clinical diagnosis of PANS at different time points. Our goal is to build on the potential role of neuroimaging in this condition in the acute and subacute phases.

Case description:

We discuss the case of an 11-year-old boy who presented with fever and altered mental status two weeks after having an upper respiratory infection. The patient underwent a contrast-enhanced brain MRI, which showed increased T2W/FLAIR signal and swelling of the caudate nuclei and putamina bilaterally, with no abnormal enhancement or restricted diffusion; notably, there was mild increased diffusion in the basal ganglia, likely reflecting vasogenic edema. Five days later, a repeat brain MRI revealed mild, diffuse high T2W/FLAIR signal, which was overall decreased compared to the prior scan. Additionally, diffusion in the caudate relatively decreased compared to the putamina. Twelve days later, there was a continued decrease in the T2W/FLAIR signal in the putamina, caudate nuclei, and possibly the lateral portion of the globi pallidi.

Discussion points:

-To present common neuroimaging findings in patients with suspicion/diagnosis of PANS/PANDAS over time, including increased T2W/FLAIR signal and mild increased diffusion in the basal ganglia.
-To discuss the current roles/limitations of neuroimaging in the workup based on the existing literature.
-To illustrate the primary differential diagnoses that can mimic PANS/PANDAS neuroimaging findings in children, including autoimmune encephalitis, Sydenham chorea, mitochondrial disorders, and tic disorders.
-To hypothesize the role of glymphatic, CSF, and venous dynamics in neuroinflammation in PANS/PANDAS related to early vasogenic edema.
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