Elsevier

World Neurosurgery

Volume 97, January 2017, Pages 751.e15-751.e21
World Neurosurgery

Case Report
Upfront Gamma Knife Surgery for Giant Central Neurocytoma

https://doi.org/10.1016/j.wneu.2016.10.073Get rights and content

Background

In this report, we present the results of using upfront Gamma Knife surgery (GKS) in the management of giant central neurocytoma (CNC) (volume >50 mL) without the initial removal of the tumor mass.

Case Descriptions

Two patients underwent GKS for histologically proven CNC. Clinical and imaging studies were performed to evaluate the response to treatment. GKS involved delivery doses of 12 or 13 Gy to the tumor margin at the isodose line of 50%. Tumor response to GKS appeared as early as 4–6 months after GKS, at which point a dramatic reduction in volume was observed. No adverse effects of radiation or new neurologic deficits were observed in either of the cases. In case 1, we observed a reduction in tumor volume from 69 to 20 mL at 6 months and a further reduction to 10.3 mL at 86 months. In case 2, we observed a reduction in tumor volume from 62 to 31 mL at 4 months with a further reduction to 22.5 mL at 30 months. The female patient (case 1) showed mild weakness in the right lower limb after the minimal surgical removal of tumor using the cortical approach. No additional neurologic deficits were observed after GKS. The young male patient (case 2) presented a complete recovery without any signs of headache at 3 months after GKS.

Conclusions

Based on this initial experience, it appears that GKS is an effective treatment for CNC and may be used for upfront management in cases of indolent clinical symptoms, even when the tumor is very large.

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.

Section snippets

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.

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