Clinical Reasoning: A 2-Year-Old Girl With Acute Encephalopathy After Febrile Systemic Illness

A 2-year-old girl presented with an acute encephalopathy with hemiparesis after febrile systemic illness. MRI showed multifocal symmetrical lesions in both thalami, and CSF showed a slightly elevated protein. The final diagnosis in this patient led to a revision of the diagnosis of neuroborreliosis in her mother, 15 years earlier. The bilateral, symmetric thalamic involvement at presentation was an important clue to suggest the final diagnosis in the mother. This case highlights common clinical pitfalls and important neuroimaging findings that led to the final diagnosis in the case of an acute encephalopathy after febrile systemic illness in a child. It also demonstrates the importance of a thorough family history in diagnosing neurologic encephalopathies to evaluate previous neurologic episodes in family members.