Imaging plays a key role in the diagnosis of pilocytic astrocytomas. Magnetic Resonance Imaging (MRI) and computed tomography with intravenous contrast agent administration are key to visualize and correctly diagnose pilocytic astrocytomas. In fact, imaging is particularly helpful delineating the PA from the surrounding healthy brain tissue [2]. We present the case of a 5-year-old patient. Bedridden patient from rural origin, who was brought by family member complaining of loss of muscle strength in upper and lower limbs lasting two months of progressive onset, associated with a history of headaches and vomiting, accompanied with vertigo, ataxic gait, diplopia and oculomotor paralysis.

Pilocytic Astrocytoma (PA) represents the most common primary benign tumor of the posterior fossa. According to the World Health Organization (WHO) classification it is considered a low-grade brain tumor [4]. It develops from star-shaped brain cells called astrocytes. Astrocytes are found within the brain and spinal cord, forming tissue that surrounds and protects other nerve cells. Clinical presentation will vary depending on the size and the location of the tumor. Symptoms result from increased brain pressure and include headaches, nausea, vomiting, ataxia and vision disorders [3]. The emergency doctor on duty requested a cerebral TDM, without contrast, with little information, which showed a heterogeneous expansive process located in the medulla oblongata (Figure 1). The following days an MRI, demonstrating an expansile process of posterior fossa, located in the medulla oblongata, with two components: (Figure 2), solid hyper intense on T2 and FLAIR component, heterogeneously enhanced after contrast media injection and a cystic hyper intense on T2, hypo intense on T1 and intermediate signal intensity on FLAIR component, with peripheral wall enhancement after contrast media injection. Surrounding perilesional edema can be depicted in T2 and FLAIR hyper intensity. Mass effect on the adjacent structures can be identified : on the inferior aspect of the fourth ventricle which is collapsed, as well as on the cerebellar tonsils. It is responsible for an effacement of the cerebello medullary cisterns, with tonsillar herniation through the foramen magnum. Spectroscopy shows a moderate decrease of the Choline/NAA ratio, and elevation of myo inositol peak and lactates on short-echo. No associated supra tentorial hydrocephalus, midline shift or other intraparenchymal signal abnormalities were found.

A biopsy was performed and the results of the pathological anatomy confirm the radiological diagnosis, and the patient is undergoing treatment.