Skull base osteosarcoma presenting with cerebrospinal fluid leakage after CyberKnife® treatment: a case report
© Yamada et al.; licensee BioMed Central Ltd. 2013
Received: 1 November 2012
Accepted: 12 March 2013
Published: 26 April 2013
CyberKnife® radiation is an effective treatment for unresectable skull base tumors because it can deliver a highly conformational dose distribution to the complex shapes of tumor extensions. There have been few reports of severe complications with this treatment. This is the first published case report to our knowledge of cerebrospinal fluid leakage induced by CyberKnife® radiotherapy.
A skull base tumor was identified on magnetic resonance imaging in a 78-year-old Asian woman with a headache in her forehead. An endoscopic transnasal tumor resection was performed; however, the tumor, invading into the cavernous sinuses and optic canal, was not completely removed. During the subtotal resection of the tumor, no cerebrospinal fluid leakage was observed. Osteosarcoma was histologically diagnosed, and CyberKnife® radiation was performed to the residual tumor considering the aggressive feature of the tumor with a molecular immunology Borstel-1 index of 15%. Five months after the treatment, magnetic resonance imaging showed definite tumor shrinkage, and the patient had been living her daily life without any troubles. After another month, the patient was transferred to our clinic because of coma with high fever, and computed tomography demonstrated severe pneumocephalus. Rhinorrhea was definitely identified on admission; therefore, emergency repair of the cerebrospinal fluid leakage was performed using an endoscope. Dural defects at the bottom of the sella turcica were identified under careful endoscopic observation and fat tissue was patched to the dural defects. Follow-up computed tomography proved complete disappearance of air from the cisterns 2 weeks after the surgery, and the patient was discharged from our hospital without any neurological deficits.
CyberKnife® radiation is one of the effective treatments for skull base tumors; however, the risk of cerebrospinal fluid leakage should be considered when tumor invasion to the dura mater is suspected. Emergency surgical treatment is required when cerebrospinal fluid leakage is induced by the radiotherapy because the leakage is not expected to be healed by palliative treatments.
KeywordsCerebrospinal fluid Complication CyberKnife® Radiation Skull base Tumor
Skull base tumors are frequently aggressive and total resection of the tumors is very difficult because of neurovascular anatomical features. Irradiation is well indicated for unresectable skull base tumors. Fractionated CyberKnife® radiation delivers a highly conformational dose distribution to the complex shapes of tumor extensions into the skull base . It is clear that many patients with skull base tumors have benefited from this radiosurgery [2–4]. Here we present a case of skull base osteosarcoma which, remarkably, was shrunk by CyberKnife® radiation, but cerebrospinal fluid (CSF) leakage occurred due to the tumor shrinkage.
In skull base tumors, the portions where surgical resection is difficult are also areas where radiation therapy is challenging, such as the cavernous sinus or optic canal, which include cranial nerves and arteries. Cranial nerve palsies and internal carotid artery stenosis caused by external radiation have been reported [6, 7]. To preserve the function of optic nerves, fractionated CyberKnife® radiation is safer and more effective than conventional radiation or gamma knife treatment . In our case, CyberKnife® treatment shrank the osteosarcoma without causing visual deterioration. However, critical CSF leakage occurred. As shown in Figure 3B left, endoscopic observation revealed thick residual tumor tissue invading the dura mater at the bottom of the sella before CyberKnife® irradiation, and the residual tumor protected the patient from CSF leakage. After the treatment, the irradiated tissue became hypovascular and necrotic change was identified in the residual tumor progressing to the dural defects. As another cause of the CSF leakage, it might be possible that the authors injured dura mater at the sella during the removal of the tumor because the border between the tumor and the dura was not observable at some points. And this pre-existing iatrogenic dural defect caused CSF leakage when the dura shrank in CyberKnife® therapy. To the best of our knowledge this is the first reported case of CSF leakage caused by CyberKnife® therapy, although a few cases of post-radiation CSF leakage were reported in gamma-knife treatment for skull base tumors [8–10]. There is no doubt that CyberKnife® treatment is very effective for skull base tumors; [2–4] however, the risk of radiation-induced CSF leakage should be considered when tumor invasion of the dura is suspected. Emergency surgical repair is required if CSF leakage is identified to avoid severe meningitis, because CSF leakage cannot be cured by palliative treatments. When a skull base tumor extends widely, it might be difficult to identify the point of CSF leakage induced by radiotherapy. In such a case, extended subcranial approach, which is usually performed for repairing rhinorrhea caused by anterior skull base fracture , should be considered instead of endoscopic transnasal surgery.
The risk of CSF leakage caused by CyberKnife® radiation should be considered when tumor invasion to the dura mater is recognized. Emergency surgical treatment is required when CSF leakage is identified because the leakage is not healed with conservative treatment.
Written informed consent was obtained from the patient for publication of this manuscript and any accompanying images. A copy of the written consent is available for review by the Editor-in-Chief of this journal.
Magnetic resonance imaging.
We all express our gratitude to JAM Post Incorporation for spell- and grammar-check of our English. The authors have declared no source of funding.
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