Case ReportUpfront Gamma Knife Surgery for Giant Central Neurocytoma
Introduction
Central neurocytomas (CNCs) are rare brain tumors generally associated with the septum pellucidum or the wall of the lateral ventricles. Only around 500 cases have been reported, which represents 0.1%–0.5% of all primary brain tumors.1 Most of these tumors are benign and classified as grade II tumors by the Word Health Organization in its classification of tumors in the nervous system. Nonetheless, a number of atypical tumors have also been reported.2
Radiosurgery has recently been used as primary or adjuvant treatment for many intracranial tumors. Similarly, radiosurgery seems to be a highly attractive treatment modality for CNC, because of the radiosensitive nature of the tumors and their anatomic location.3, 4 Recent advances in radiologic techniques have increased the incidental detection of CNCs. Several reports have recommended radiosurgery as the primary treatment for CNC.3, 5, 6 CNCs are intraventricularly located and tend initially to follow an indolent clinical course. Therefore, they can grow to a large size without detection. Most of the symptoms are associated with the blockage of cerebrospinal fluid pathways. The treatment of choice for large symptomatic CNCs is complete surgical resection, whenever possible. The outcomes of microsurgical removal depend on the extent of the resection and the histologic grading.2, 7 However, the deeply seated intraventricular location of CNCs puts them close to critical neurovascular structures, such as the fornix and thalamus. Surgical morbidity and mortality are not uncommon. In contrast, tumor control rates after stereotactic radiosurgery (SRS) for the subtotal removal of CNC reached 90% in a 5-year follow-up and more than 80% in a 10-year follow-up.5, 6 Thus, the issue of whether CNCs can be treated primarily by SRS remains a topic of debate, particularly in cases of silent CNC. The relatively small patient population means that methods for the optimal management of asymptomatic or incidentally identified CNC have yet to be confidently established. In this article, 2 cases of giant ventricular CNC (>50 mL in volume) are reported, which were treated with Gamma Knife surgery (GKS) (Elekta, Stockholm, Sweden). The feasibility is investigated of directly targeting large-volume CNCs, as an alternative to decompression or the total removal of the tumor in the first stage of treatment. Histologic proof is essential for tumors of this size; therefore, upfront GKS refers only to primary SRS after needle or open biopsy of the tumor.
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Patient Population
In a review of the 1185 patients who were treated at the Buddhist Tzu Chi General Hospital, Hualien, Taiwan between 2003 and 2015, we identified 2 patients who presented with giant CNCs. These patients were followed after undergoing upfront management of the tumors using GKS. The institutional review board of the Buddhist Tzu Chi Medical Center approved the research protocol.
Diagnosis, Treatment, and Follow-Up
A pathology-proven diagnosis was obtained for each tumor based on stereotactic biopsy or open partial removal of the
Case 1
The patient was a 20-year-old woman presenting with mild headache, dizziness, and tinnitus over a period of 3 years. The symptoms became more severe 6 months before admission, at which point MR images showed a huge mass measuring approximately 60 × 59 × 57 mm in the bilateral lateral cerebral and third ventricles (Figure 2). Physicians initially planned a left occipital transcortical approach to tumor removal; however, only minimal removal was conducted because of the hypervascularity of the
Surgery for CNC
CNCs are rare intraventricular brain tumors, which are believed to be benign neoplasms with neuronal differentiation.8 The ventricular location and indolent clinical course mean that they can grow into a large biventricular mass with third ventricle extension by the time of presentation. Common clinical symptoms include dizziness and headache, both of which are usually associated with partial obstructive hydrocephalus or intracranial hypertension. This characteristic has led to the suggestion
Conclusions
In this article, 2 cases of giant CNCs treated using GKS after stereotactic or open biopsy are reported. This approach reduced the volume of the tumors by more than half within 6 months after GKS. Many cases would require the insertion of a ventriculoperitoneal shunt to deal with the hydrocephalus; however, we did not encounter the need for such interventions in this study. Upfront SRS for large CNCs appears to be a feasible approach when clinical symptoms are indolent. Surgical intervention to
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Conflict of interest statement: The authors declare that the article content was composed in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.