Case Presentation: A 14-year-old male with autism spectrum disorder presented with history of 5 days of refusal to move and imbalance for 2 days, following diarrheal illness two weeks prior. On admission, he was tachycardic and hypertensive with dry mucous membranes. His neurologic exam was limited by agitation but demonstrated symmetric facies and 5/5 strength throughout. Lab work up showed an elevated lactate and high anion gap metabolic acidosis, both of which resolved with fluids. Two days later, he was noted to have 3/5 strength in bilateral hip flexors but 5/5 strength in all other muscle groups, as well as areflexia in the lower extremities. Sensory and upper extremity coordination were unremarkable. MRI thoracic and lumbosacral spine showed cauda equina nerve root enhancement. A lumbar puncture revealed cerebrospinal fluid (CSF) with 0 nucleated cell/uL, 1 red blood cell/uL, protein 59 mg/dL, and glucose 65 mg/dL. He was diagnosed with GBS and treated with 5 days of intravenous immunoglobulin. His symptoms worsened over the next week; he developed right facial droop, restriction of upward gaze, vertical nystagmus, and slurred speech, as well as bilateral upper extremity tingling and ascending paralysis requiring intubation. Further workup revealed multiple nutritional deficiencies including thiamine (B1), B12, folate, and methylmalonic acid. MRI brain showed increased T2/FLAIR signal at the bilateral medial thalami, caudate nuclei, periaqueductal gray, and floor of the fourth ventricle with restricted bilateral medial thalamic diffusion, suggestive of Wernicke’s encephalopathy. He received aggressive B12, thiamine, and folate repletion with gradual recovery, including successful extubation and return to baseline mental status.

Discussion: Thiamine is an essential micronutrient obtained through many food sources. TD manifests as a multitude of neurologic symptoms, including decreased or absent deep tendon reflexes, ataxia, and altered mental status. Wernicke’s encephalopathy, a degenerative brain disorder caused by thiamine deficiency, is characterized by a triad of clinical symptoms: confusion, ataxia, and ocular abnormalities. In our patient, the MRI and CSF results, as well as prior diarrheal illness, were suggestive of GBS. However, our patient worsened despite treatment and was ultimately diagnosed with TD and Wernicke’s encephalopathy.

Conclusions: Due to its atypical presentation, TD is often missed or misdiagnosed, especially in pediatrics. Early diagnosis and treatment is essential to prevent long term neurologic deficits. Our case highlights the importance of considering TD in all children who present with unexplained neurologic abnormalities, particularly in those with autism and/or sensory food aversions.