Ependymomas arising from the fourth ventricle typically show which pattern of spread?

Explanation

## Fourth Ventricular Ependymoma — Pattern of Spread **Key Point:** Fourth ventricular ependymomas characteristically extend **downward through the foramen magnum** and frequently show **leptomeningeal dissemination** along the spinal cord and brain surface. ### Anatomical Basis **High-Yield:** The fourth ventricle is located at the pontomedullary junction, directly above the foramen magnum. Tumors arising here naturally extend caudally into the cervical spinal canal and subarachnoid space, leading to: - Spinal cord compression - Leptomeningeal seeding ("drop metastases") - Spinal MRI findings of nodular enhancement along nerve roots ### Clinical Consequences | Complication | Mechanism | Imaging Finding | |--------------|-----------|------------------| | **Obstructive hydrocephalus** | Mass in 4th ventricle | Enlarged lateral and 3rd ventricles | | **Spinal dissemination** | Downward growth + CSF seeding | Nodular enhancement on spinal MRI | | **Syrinx** | Cord compression or tethering | T2 hyperintensity in cord | | **Brainstem compression** | Direct mass effect | Deformity of pons/medulla | ### Why This Matters **Clinical Pearl:** Spinal MRI is **mandatory** in all ependymoma patients because leptomeningeal dissemination affects staging, prognosis, and treatment planning (radiation field design). **Mnemonic:** **FOSSA** — Fourth ventricular tumors: Forward (obstructive hydrocephalus) and downward Spread (foramen magnum extension, Spinal dissemination) [cite:Osborn's Brain Imaging Ch 5] ### Imaging Protocol 1. Brain MRI with contrast (assess primary tumor, hydrocephalus) 2. **Spinal MRI with contrast** (mandatory for staging) 3. CSF cytology (if clinically indicated)