Neurol Med Chir (Tokyo) 43, 391 395, 2003 Delayed Radiation Necrosis With Extensive Brain Edema After Gamma Knife Radiosurgery for Multiple Cerebral Cavernous Malformations Case Report Nobuo TAKENAKA, Tomoyuki IMANISHI, HikaruSASAKI, KenjiSHIMAZAKI, Hitoshi SUGIURA*, Yasuhisa KITAGAWA**, SariSEKIYAMA**, Masaaki YAMAMOTO***, andtakahitokazuno # Departments of Neurosurgery and *Pathology, Kawasaki Municipal Hospital, Kawasaki, Kanagawa; **Department of Neurology, Tokai University Oiso Hospital, Kanagawa; ***Katsuta Hospital Mito Gamma House, Hitachinaka, Ibaraki; # Department of Neurosurgery, Fujisawa Neurosurgical Hospital, Fujisawa, Kanagawa Abstract A 39-year-old man presented with multiple intracranial cavernous malformations manifesting as intractable seizures persisting for more than 20 years. He underwent gamma knife radiosurgery (GKRS) for right frontal and left temporal cavernous malformations. He began to suffer from progressive left hemiparesis and inattention 2 years 5 months after the GKRS. Magnetic resonance imaging showed abnormal ring enhancement and extensive brain edema around the right frontal lesion. Conservative therapies such as external decompression, low-dose barbiturates, and mild hypothermia had no effect on his clinical status. Stereotactic biopsy of the ring-enhanced area demonstrated gliosis. Signs of cerebral herniation appeared, so we performed partial resection of the right frontal lobe. His symptoms recovered immediately. Subsequent hyperbaric oxygen (HBO) therapy significantly improved the extensive brain edema. Delayed radiation necrosis associated with potentially fatal brain edema may occur after GKRS for cavernous malformations. Internal decompression and subsequent HBO therapy were very effective for the treatment of these lesions. Key words: radiation necrosis, gamma knife, cavernous malformation, decompression, hyperbaric oxygen therapy Introduction The benefits of gamma knife radiosurgery (GKRS) for the treatment of cavernous malformations remain unclear because of several unsolved problems including the natural history of these abnormalities, 2,13,15) the assessment of radiographic changes after GKRS, 2,9,12) the undetermined appropriate radiation dosage, 4) and the individual variations in irradiation sensitivity. 4) The risk of bleedingsignificantlydecreasesby2to4yearsorlonger after GKRS, 9,11,12,15) and the frequency of intractable seizures also decreases after GKRS. 3,7,10,22) However, the incidence of radiation-induced complications associated with GKRS for cavernous malformations Received July 16, 2002; Accepted March 24, 2003 is higher than that for arteriovenous malformations. 7,9,15) The adverse effects of GKRS include brain edema, 15,19) rebleeding, 9) stenosis of the middle cerebral artery, 20) radiation-induced tumors, 16) and cyst formation. 20) However, fatal brain edema attributable to GKRS has never been reported. We describe a case of extensive brain edema with impending cerebral herniation after GKRS for multiple cavernous malformations which was treated with internal decompression and subsequent hyperbaric oxygen (HBO) therapy. Case Report A 39-year-old man presented with history of intractable seizures persisting for more than 20 years. Magnetic resonance (MR) imaging demonstrated 391
392 N. Takenaka et al. Fig. 1 Axial T 2 -weighted magnetic resonance images obtained 9 months before gamma knife radiosurgery showing mixed intensity lesions suggesting cavernous malformations. Fig. 2 Axial T 2 -weighted magnetic resonance images showing the dose planning for lesions of the right frontal lobe (A) and the left temporal lobe (B). The arrow shows the 50% isodose gradient, and other lines are the 90%, 70%, 30%, and 20% isodose gradients from the center. mixed intensity signals surrounded by low intensity rims in the right frontal and left deep temporal regions, suggesting multiple intracranial cavernous malformations 8) (Fig. 1). His seizures were uncontrollable by medication (ex. sodium valpronate 1600 mg/day and zonisamide 600 mg/day), so he underwent GKRS at Katsuta Hospital Mito Gamma House on March 3, 1999. Lesion volumes were 5.9 ml for the right frontal lesion and 2.0 ml for the others. The marginal dose was 20 Gy and the maximum dose was 40 Gy for each lesion (Fig. 2). Subsequently, the seizures decreased in frequency but did not disappear. Serial MR imaging at intervals of a few months Fig.3 A,B:AxialT 2 -weighted magnetic resonance (MR) images obtained 2 years 1 month after gamma knife radiosurgery showing perifocal abnormal intensity in both cavernous malformations. C, D: Axial T 1 -weighted same time showing abnormal enhancement at the sites of both cavernous malformations and perifocal edema. showed no changes until April 2001, when abnormal ring enhancement after gadolinium administration and brain edema were first noticed (Fig. 3). The patient began to suffer from recent memory disturbance in July 2001, and progressive left hemiparesis in early August. He was admitted to our hospital on August 27, 2001. On admission, he had headache, appetite loss, and inattention. MR imaging demonstrated abnormal ring-like enhancement and extensive brain edema, suggesting radiation necrosis, around the right frontal lesion, which was associated with cingular herniation (Fig. 4). Angiography showed no abnormal findings except for circulation delay in the right hemisphere. His consciousness disturbance progressed, so stereotactic biopsy of the ring-enhanced lesion in the right frontal lobe and external decompression were conducted on August 30. The histological
Extensive Brain Edema After GKRS 393 Fig. 5 A: Axial T 2 -weighted magnetic resonance (MR) image obtained 7 weeks after hyperbaric oxygen therapy showing moderate shrinkage of the cavernous malformation and perifocal edema. B, C: T 1 -weighted same time (B: axial section, C: sagittal section) showing moderate shrinkage of the enhanced mass and perifocal edema. Fig. 4 A, B: Axial T 2 -weighted magnetic resonance (MR) images obtained 2 years 5 months after gamma knife radiosurgery showing marked enlargement of the cavernous malformation and perifocal edema. C E: T 1 -weighted same time (C: axial section, D: coronal section, E: sagittal section) showing an acutely enlarged ring-like enhancement at the site of the cavernous malformation, associated with marked edema. diagnosis of the biopsy specimen was gliosis. Severe intracranial hypertension was detected despite low-dose barbiturate therapy (4000 mg/day), mild hypothermia (34 359C), and dexamethasone administration (16 mg/day) after external decompression. On re-warming, impending central transtentorial herniation signs such as anisocoria appeared. Partial resection of the right frontal lobe for internal decompression was performed on September 6. The histological findings of the specimen included gliosis and interstitial edema. Subsequently, his consciousness disturbance and left hemiparesis disappeared and computed tomography showed improvement of the mass effect. The patient was discharged with only mild disorientation on December 5, 2001. The frequency of seizures decreased, and the patient returned to an independent life. MR imaging showed that the midline shift had improved, but the abnormal high intensity lesion on T 2 -weighted images and abnormal ring-like enhancement were still present in January 2002. He received HBO treatment for 10 days. MR imaging showed that the lesions were reduced in size 7 weeks later (Fig. 5). Discussion Resection of a cavernous malformation is expected to decrease the surrounding edema, but we per-
394 N. Takenaka et al. formed internal decompression rather than resection of the enlarged lesion after GKRS because MR imaging showed that the lesion had enlarged by several times, so we considered that radical resection would carry the risk of motor and/or intellectual deficits which would impair the patient's ability to lead a normal life. Internal decompression was much more effective than external decompression, low-dose barbiturates, hypothermia, 17) or steroid therapy, 18) and the patient was rescued from the potentially fatal effects of the brain edema. However, if the edema had persisted after the HBO therapy, we may have had to resect the cavernous malformation. Adverse effects of GKRS are associated with relatively high integrated tumor volume doses, increased tumor volume, increased10-gy volume, and repeated radiosurgery for the same lesion. 4) The present case had relatively small, well-defined lesions, so GKRS was expected to be safe. However, the smaller frontal lesion unexpectedly developed extensive brain edema after GKRS. Reactive astrocytes were recognized in the ring-enhanced lesion, so destruction of the blood-brain barrier may have been involved in the present case. 21) HBO therapy is a useful treatment for radiation necrosis, 14) and, in the present case, was effective in improving the MR imaging findings of radiation necrosis, i.e., the abnormal ring enhancement after gadolinium administration associated with extensive brain edema. 1) HBO therapy increases the tissue PO 2, which may facilitate cellular and vascular repair. 5,6) Radiation necrosis is considered to be associated with ischemic changes, so the efficacy of HBO therapy may reflect the plasticity of tissue with radiation-induced ischemic changes. GKRS is increasingly applied for various lesions including cavernous malformations, but delayed radiation necrosis associated with potentially fatal brain edema could occur after GKRS. 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