American Board of Psychiatry and Neurology (ABPN) Practice Exam 2025 - Free ABPN Practice Questions and Study Guide

In the case of a 6-year-old girl experiencing headaches and vomiting, the most likely diagnosis is medulloblastoma, particularly when assessed alongside MRI findings. Medulloblastoma is the most common malignant brain tumor in children and often presents with symptoms related to increased intracranial pressure, such as headaches and vomiting due to obstruction of cerebrospinal fluid (CSF) pathways or brain growth.

On MRI, medulloblastomas typically appear as hyperdense masses located in the posterior fossa, often affecting the cerebellum. They may also demonstrate features like hydrocephalus secondary to blockage of CSF flow caused by the tumor's location. Additionally, these tumors can exhibit contrast enhancement and may spread through the CSF, which can also affect their presentation in imaging.

The other options, while presenting in the pediatric population, have differing characteristics that make them less likely diagnoses. Glioblastoma, a highly aggressive tumor, is more common in adults than in young children. An arachnoid cyst might appear on MRI but typically would not present with these acute symptoms, nor would it account for significant tumors' typical impact on CSF flow. Hemangioblastomas are rare and usually associated with von Hippel-Lindau syndrome; they