An overview of Cerebellar Astrocytoma

Cerebellar astrocytoma (CA) is a benign tumor of astrocytes or a specific type of glial cell tumor which has been mainly observed in the posterior fossa region (25%) of the brain. Overall, CA accounts for almost 10% of all primary brain tumors. Glial cells are supportive cells to neurons in the brain consisting of astrocytes, oligodendrocytes, ependymal cells, as well as microglia. ​ CA is most evident among children and young adults with well-circumscribed regions, as it is also called juvenile pilocytic astrocytoma. The cerebellum is the vital part of the brain which is responsible for balance and coordinated movements. Pilocytic astrocytoma is synonymously used for cerebellar astrocytoma as it most commonly occurs in the cerebellum.

The majority of CA arises from the central nervous system (CNS). The nature of the tumor is a low grade with patients having long-term survival. CA may lead to increased head circumference with cerebellar lesion-oriented major symptomatic manifestations such as peripheral ataxia, intention tremor, dysmetria, nystagmus, and dysarthria.

Global perspective

According to the WHO, such rare tumors are considered Grade I astrocytomas with a good prognosis. Generally, CA is a pediatric tumor that is caused by ionizing radiations and/or mutations of the BRAF proto-oncogene sporadically. Most pilocytic astrocytomas (90%) are having a global survival mean of 10 years. These Grade I tumors contribute to approximately 5.1 % of all gliomas with males being slightly more affected in comparison to females. Most juvenile pilocytic astrocytomas manifest by the early two decades of life with an estimated incidence rate of 14 new cases per million in children (<15 years).

Indian perspective

According to a study decades ago, emphasis on the role of radiotherapy following surgical resection as the mainstay of pilocytic astrocytoma management was established in India. There is a concern for prognosis which needs to be addressed for the infiltrating types of diffused astrocytomas. However, a recent Indian population study with adult low-grade gliomas has associated p53 mutations and altered microvascular density count to detect early recurrence of aggressive infiltrating diffuse tumor behavior of pilocytic astrocytomas, indicating the malignancies can occur at a higher rate in adults.

Signs and symptoms

Some very common signs are headaches, nausea, vomiting, balance problems along with vision defects. CA can merely be managed through surgical removal with fewer chances of leading to malignancy.

Diagnosis

A diagnosis of CA relies on clinical evaluation and a number of tumor-specific investigations including imaging modalities. Such major imaging techniques are:

• Computerized tomography (CT) scans

• Magnetic resonance imaging (MRI)

Other than imaging techniques, surgical removal and microscopic evaluation of biopsy samples are done for histopathological confirmation of the diagnosis. A biopsy is not to be sought if the tumor is in the optical axis.

Management

The mainstay of management is surgery, preferably complete resection with minimal neurological damage which can be curative. Post-operative radiotherapy after surgery is required, following time to time monitoring with different imaging techniques for ensuring patients’ quality of life. In case of unfortunate recurrence, further surgical resection may be required. ​ Radiotherapy is the option for surgically unresectable or malignant tumors. Management of hydrocephalus is another major area of management in patients where fluid accumulates inside the brain cavities. Surgery following cerebrospinal fluid (CSF) diversion using an external ventricular drain (EVD), endoscopic third ventriculostomy (ETV), or ventricular-peritoneal shunt (VPS) is the major operative procedure in the management of patients with CA. ​ The prognosis is good in CA tumors. Post resection, recurrence of tumors or malignancies are rare. According to detailed research, it has been formulated according to Collins' law which states that there is a risk for tumor recurrence till nine months after the initial diagnosis in children. Unfortunately, infants under the age of one year have the worst prognosis in pilocytic astrocytomas. ​ For completely excised tumors, there should be regular monitoring by imaging at least for three years to check for any signs of recurrence. In patients with mainly affected posterior fossa region, they may develop hydrocephalus in the pre-operative phase with a need to have a VP-shunt throughout their life. Though recurrence is rare, some patients may exhibit malignant degeneration. The majority of such recurrent malignant cases seem to follow radiotherapy. ​ Specifically, pilocytic astrocytoma in children requires immediate evaluation and management. These rare disease patients need to be presented to pediatricians or emergency clinicians for early detection through signs and symptoms of affected cerebellum involving the distinct clinical manifestation of hydrocephalus. An effort from an interprofessional team consisting of neurosurgeons, oncologists, anesthetists as well as nursing staff should be involved in the decision-making process for the prompt management of patients.

Quality of life

Following surgery, the quality-of-life management should be ensured by a post-operative team of experts. Especially in children, the quality of life (QoL) should be critically assessed with the involvement of school teachers and mentors. Therefore, educational support is crucial in managing the quality of life. Whereas, in general, cerebellar astrocytoma patients indeed have long-term complications influencing physical, psychological, as well as cognitive health. Therefore, timely monitoring of different physical and cognitive features along with the help of support groups are required in giving the patient a good quality of life.