Pilocytic astrocytoma (PA) is the most common pediatric cerebellar neoplasm and the most common pediatric glioma, constituting 85 % of all cerebellar astrocytomas and 10 % of all cerebral astrocytomas in this age group [1]. PAs are usually clinically benign and are classified as grade I by the World Health Organization (WHO) [2].

The incidence is approximately 4.8 cases per million people per year, with 2.3–6 % of all brain tumors classified as PA [3]. They have a peak incidence between the age of 5 and 13 years and occur equally frequent in boys and girls [1]. Cerebellar astrocytomas are usually sporadic, but association with neurofibromatosis type 1, Turcot syndrome, PHACE(S) syndrome, and Ollier’s disease has been reported [4]. The prognosis depends particularly on tumor characteristics (location, gross structure, and size) and the completeness of resection. Complete resection, hemispheric location, small size, and presence of cysts are favorable prognostic factors [5].

They are potentially curable by surgery and are associated with a longer survival, with the 25 years survival rate being close to 90 % [6].

Very rarely, a PA may undergo spontaneous malignant transformation and become an anaplastic astrocytoma. Accurate interpretation of imaging studies plays an essential role in directing treatment of these tumors. Patients with cerebellar PA typically present with a gradual onset of symptoms due to the slow growth of the tumor. Common presenting symptoms include headache, nausea and vomiting, and gait imbalance. Common clinical findings include truncal ataxia and papilledema (due to increased intracranial pressure) [7] (Fig. 26.1).