Spontaneous Regression of Glioma-Mimicking Brainstem Lesion in a Child: A Case Report.

Differential diagnosis of focal brainstem lesions detected on MRI is challenging, especially in young children. Formerly, brainstem gliomas were classified mainly based on MRI features and location. However, since 2016, the World Health Organization's brainstem lesion classification requires tissue biopsy to reveal molecular characteristics. Although modern techniques of stereotactic or navigation-guided biopsy ensure accurate biopsy of the lesion with safety, biopsy of brainstem lesions is still generally not performed. Here, we report a focal brainstem lesion mimicking brainstem glioma in a 9-year-old girl. Initial MRI, MR spectroscopy, and ¹¹C-methionine positron emission tomography (PET) features suggested low-grade glioma or diffuse intrinsic pontine glioma. However, repeated MR spectroscopy, perfusion MRI, and ¹⁸fluorodeoxyglucose PET findings suggested that it was more likely a non-tumorous lesion. As the patient presented not with a neurological manifestation but with precocious puberty, the attending oncologist chose to observe with regular follow-up MRI. The pontine lesion with high signal intensity on T2-weighted MRI regressed from the 6-month follow-up and became invisible on the 1.5-year follow-up MRI. We reviewed brainstem glioma-mimicking lesions in the literature and discussed the key points of differential diagnosis.