- Email: [email protected]
Radiation-induced edema after radiosurgery for pontine arteriovenous malformation
Surg Neurol 1992;37:15-21
15
Radiation-Induced Edema After Radiosurgery for Pontine Arteriovenous Malformation A Case Report and Detection by Magnetic Resonance Imaging Masaaki Yamamoto, M.D., MinoruJimbo, M.D., and Christer Lindquist, M.D., Ph.D. Department of Neurosurgery, Tokyo Women's Medical College Dai-ni Hospital, Tokyo, Japan, and Department of Neurosurgery, Karolinska Hospital, Stockholm, Sweden
Yamamoto M, Jimbo M, Lindquist C. Radiation-induced edema after radiosurgery for pontine arteriovenous malformation. A case report and detection by magnetic resonance imaging. Surg Neurol 1992;37:15-21.
A 29-year-old woman, who had undergone stereotactic radiosurgery for a pontine arteriovenous malformation, experienced sudden onset of facial nerve palsy with trigeminal nerve disturbance 19 months after irradiation. Magnetic resonance imaging revealed significant radiation-induced edema surrounding the nidus. Angiography demonstrated total obliteration of the arteriovenous malformation 24 months after irradiation. Further magnetic resonance imaging studies, performed 28 months after treatment, showed that, despite the persistence of symptoms, the radiation-induced edema had subsided. KEYWORDS: Radiosurgery; Radiation; Arteriovenous malformation; Pons; Radiation-induced edema; Magnetic resonance imaging
Although stereotactic radiosurgery is regarded as the treatment of choice for small, deep-seated arteriovenous malformations (AVMs) [1,2,5], experience in using this treatment for brain stem AVMs is limited. We report here a case of a pontine AVM presenting with radiation-induced edema surrounding the nidus after successful obliteration o f the AVM. Case Report This 29-year-old pregnant woman experienced a change in taste sensation on March 11, 1987, followed by rightsided facial muscle weakness and periodic vomiting. She was admitted to a local hospital, where computed toAddress reprint requests to: Masaaki Yamamoto, M.D., Department of Neurosurgery, Tokyo Women's Medical College Dai-ni Hospital, 2-1-10 Nishiogu, Arakawa-ku, Tokyo, Japan. Received April 23, 1991; accepted June 3, 1991.
© 1992 by Elsevier Science Publishing Co., Inc.
mography (CT) scan revealed a small hemorrhage within the pons. Seven days later, she was referred to our clinic for evaluation because of worsening symptoms.
Examination Physical examination on admission was within normal limits, except for slight lethargy. Neurological examination disclosed a mild sensory disturbance on the right side of the face; hemifacial muscle weakness, including the upper half of the face, associated with hyperacusis of the right ear; and loss of taste on the right, anterior portion of the tongue. A consulting gynecologist reported that the patient was in the eighth week of pregnancy. The pregnancy was artificially terminated 2 weeks after admission. Computer tomography scan showed a hyperdense right dorsal pontine lesion that was enhanced by contrast medium (Figure 1, upper). Angiography revealed a small pontine AVM fed by the anterior inferior cerebellar artery and draining into the petrous sinus (Figure 2). She left our clinic on April 26, 1987, after medical treatment had produced complete remission of her symptoms.
Radiosurgery After a 12-month asymptomatic period, she underwent stereotactic radiosurgery with a gamma unit at the Karolinska Hospital, Stockholm, on May 17, 1988. The 10 x 13 x 10-mm nidus was covered by a 90% isodose volume of the 14-mm collimator, and a maximum dose of 24.0 Gy was used to irradiate the central part of the nidus, with the peripheral dose being 21.6 Gy.
Postoperative Course On admission to our clinic for a routine check 12 months after radiosurgery, there was no evidence of 0090-3019/92/$3.50
16
Surg Neurol 1992;37:15-21
Yamamoto et al
Figure 1. Sequential C T scans, (left) plain and (right) enhanced. (Upper) C T scan, taken 2 weeks after the onset, showed a right pontine hyperdense lesion with slight enhancement. ( ~ ) Plain C T scan, taken 19 months after treatment, demonstrated no density abnormality, (middle right) but enhanced C T revealed a hyperdense lesion. (Lower left) An equivocal hyperdense spot was identified by C T taken 28 months after treatment, with a smaller enhanced area (lower right) than was seen on the previous image (middle right).
neurological deficit. C o m p u t e d tomography revealed a pontine hyperdense lesion that was enhanced by contrast medium. The A V M was still clearly visible with
angiography, indicating that it had not been completely obliterated by the radiosurgery. She was seen on D e c e m b e r 15, 1989, following the
Radiation-Induced Edema by Radiosurgery
sudden development of facial nerve palsy and sensory impairment of the right side of the face associated with balance disturbance. Although nonenhanced CT scan revealed no density abnormalities, a small hyperdense lesion in the ports could be visualized on CT scan with enhancement (Figure 1, middle). Tl-weighted magnetic resonance imaging (MRI) demonstrated enlargement of the right half of the pons and an area of low intensity, corresponding to the hyperdense lesion seen on enhanced CT scan, which was significantly enhanced by gadolinium (Gd)-DTPA administration (Figure 3, upper and middle). T2-weighted MRI revealed a hyperintense zone surrounding the lesion in the pons and cerebellum (Figure 3, lower). Since these findings suggested radiation-induced edema, beta-methasone was given at a dose o f 16 mg daily for 4 weeks, then tapered off over 3 months. The patient responded to steroid treatment with a slight clinical improvement, but her symptoms never completely subsided. Angiography taken 2 years after irradiation demonstrated total obliteration of the AVM (Figure 4). Follow-up CT and MRI were performed in September 1990. Computed tomography showed a faint hyperdense spot in the right dorsal part of the pons with slight enhancement after contrast administration (Figure 1, lower), which appeared as a hypointense area on both T1- and T2-weighted MRIs with no significant enhancement after G d - D T P A administration (Figure 5). The edema within the pons and cerebellum, detected by previous MRI studies, had disappeared.
Surg Neurol 1992;37:15-21
17
Figure 2. Angiograms, taken a week after the onset, showedan arteriovenous malformation, fed by the anterior inferior cerebellararters and draining into the petrous rein.
Discussion With the increasing use of gamma units, more patients with AVM, acoustic neurinoma, pituitary adenoma, and so on are being treated by stereotactic radiosurgery [ 1 3]. Nevertheless, the incidence of postirradiation complications remains statistically insignificant. The overall incidence of permanent morbidity from radiosurgery for AVMs is estimated to be only 3.1% [4]. Radiation exposure to critical organs is considered insignificant in this treatment (less than 0.1 Gy). As previously mentioned, experience in using this treatment for brain stem lesions is limited. Therefore, little is known about the radiosensitivity of adjacent brain structures, such as the pons. For this reason, a peripheral dose of 21.6 Gy, generally considered a suboptimal dose, was given in this case. The optimal dose for AVM is more than 23 Gy. In our experience with radiosurgical treatment of acoustic neurinoma [3,6], irradiation of the portion of the pons facing the tumor with a dose of 18 Gy or slightly more has never resulted in permanent damage to the pons. Therefore, the dose given in this case was
18
Surg Neurol 1992;37:15-21
Figure 3. T l-weighted M R I (upper, SE 400/21) demonstrated a hypointense area in the pons with significant enhancement after G d - D T P A administration (middle). This lesion was surrounded by a hyperintense edematous area in the pons and cerebellum, as revealed by T2-weighted MRI (lower, SE 2500/150). This M R I study was performed at 0.5 T. 19 months after treatment.
Figure 4. Total obliteration of the arteriovenous malformation was confirmed by angiograms taken 24 months after irradiation.
x,O
20
Surg Neurol 1992;37:15-21
Yamamoto et al
Figure 5. The lesion, demonstrated as an abnormally enhanced area by the previous MRI study, was seen as a hypointense area on both Tl-weighted (upper, SE 500/20) and T2-weighted (lower, SE 2000/80) MRIs. (Middle) This lesion was not enhanced by Gd-DTPA administration. This MRI study was performed at 1.5 T, 28 months after treatment.
not considered to be dangerously high. We speculate that part of the pons, having been damaged by the preceding hemorrhage, was vulnerable to the ischemia that accompanies obliteration of the AVM. The sequential CT and MRI studies of this case could be considered to reveal a process of gradual AVM obliteration after radiosurgery. In the initial studies, per-
formed 19 months after treatment, isodensity with contrast enhancement on CT scan (Figure 1, middle), low intensity on Tl-weighted MRIs with partial gadolinium enhancement, and mixed intensity on T2-weighted MRIs (Figure 3) could suggest partial thrombosis of the nidus with minimal residual blood flow. However, in the study performed 28 months after irradiation, when
R a d i a t i o n - I n d u c e d E d e m a by Radiosurgery
total obliteration of the AVM had been confirmed angiographically, a hyperdense spot with minimal contrast enhancement (Figure 1, lower), low intensity on both T1- and T2-weighted MRIs and lack of gadolinium enhancement (Figure 5) suggested total thrombosis associated with accumulation of calcium and/or hemosiderin, and no residual blood flow. Thus, controlled studies of the long- and short-term sequelae of radiosurgical treatment of brain stem lesions should be conducted using MRI as well as CT. The authors thank Bierta E. Barfod, M.D., University of Washington School of Medicine, for her assistance in the preparation of this manuscript. This study was supported by scholarships from the Royal Swedish Academy of Sciences, the Japanese Society for the Promotion of Science, the Japan Private School Promotion Foundation, and the Dr. Itoe Okamoto International Exchange Fund.
Surg N e u r o l 1992:37:15-21
21
References I. Jimbo M. Radiotherapy of AVM: gamma-knife. In: Takakura K, ed. Treatment of cerebral and spinal arteriovenous malformations. Tokyo: Gendai-iryou-sha, 1988:117-28. 2. Lindquist C, Steiner L. Stereotactic radiosurgical treatment of arteriovenous malformations. In: Lunsford LD, ed. Modern stereotactic neurosurgery. Boston: Nijhoff, 1988:491-505. 3. Nor~n G, Arndt J, Hindmarsh T, Hirsch A. Stereotactic radiosurgical treatment of acoustic neurinomas. In: Lunsford LD, ed. Modern stereotactic neurosurgery. Boston: Nijhoff, 1988:481-9. 4. Steiner L. Possibilities and limits of radiosurgery in the treatment of intracranial tumors and arteriovenous malformations. Abstract of the 49th Annual Meeting of the Japan Neurosurgical Society, Tokyo, lc)90:IL-4. 5. Steiner L. Treatment of arteriovenous malformation by radiosurgery. In: Wilson CB, Stein BM, eds. lntracranial arteriovenous malformations. Baltimore: Williams & Wilkins, 1984:295-313. (~. Yamamoto M, Nordn G. Stereotactic radiosurgery in acoustic neurinomas. Neurol Surg (Tokyo) 1900; l 8:1101-6.
15
Radiation-Induced Edema After Radiosurgery for Pontine Arteriovenous Malformation A Case Report and Detection by Magnetic Resonance Imaging Masaaki Yamamoto, M.D., MinoruJimbo, M.D., and Christer Lindquist, M.D., Ph.D. Department of Neurosurgery, Tokyo Women's Medical College Dai-ni Hospital, Tokyo, Japan, and Department of Neurosurgery, Karolinska Hospital, Stockholm, Sweden
Yamamoto M, Jimbo M, Lindquist C. Radiation-induced edema after radiosurgery for pontine arteriovenous malformation. A case report and detection by magnetic resonance imaging. Surg Neurol 1992;37:15-21.
A 29-year-old woman, who had undergone stereotactic radiosurgery for a pontine arteriovenous malformation, experienced sudden onset of facial nerve palsy with trigeminal nerve disturbance 19 months after irradiation. Magnetic resonance imaging revealed significant radiation-induced edema surrounding the nidus. Angiography demonstrated total obliteration of the arteriovenous malformation 24 months after irradiation. Further magnetic resonance imaging studies, performed 28 months after treatment, showed that, despite the persistence of symptoms, the radiation-induced edema had subsided. KEYWORDS: Radiosurgery; Radiation; Arteriovenous malformation; Pons; Radiation-induced edema; Magnetic resonance imaging
Although stereotactic radiosurgery is regarded as the treatment of choice for small, deep-seated arteriovenous malformations (AVMs) [1,2,5], experience in using this treatment for brain stem AVMs is limited. We report here a case of a pontine AVM presenting with radiation-induced edema surrounding the nidus after successful obliteration o f the AVM. Case Report This 29-year-old pregnant woman experienced a change in taste sensation on March 11, 1987, followed by rightsided facial muscle weakness and periodic vomiting. She was admitted to a local hospital, where computed toAddress reprint requests to: Masaaki Yamamoto, M.D., Department of Neurosurgery, Tokyo Women's Medical College Dai-ni Hospital, 2-1-10 Nishiogu, Arakawa-ku, Tokyo, Japan. Received April 23, 1991; accepted June 3, 1991.
© 1992 by Elsevier Science Publishing Co., Inc.
mography (CT) scan revealed a small hemorrhage within the pons. Seven days later, she was referred to our clinic for evaluation because of worsening symptoms.
Examination Physical examination on admission was within normal limits, except for slight lethargy. Neurological examination disclosed a mild sensory disturbance on the right side of the face; hemifacial muscle weakness, including the upper half of the face, associated with hyperacusis of the right ear; and loss of taste on the right, anterior portion of the tongue. A consulting gynecologist reported that the patient was in the eighth week of pregnancy. The pregnancy was artificially terminated 2 weeks after admission. Computer tomography scan showed a hyperdense right dorsal pontine lesion that was enhanced by contrast medium (Figure 1, upper). Angiography revealed a small pontine AVM fed by the anterior inferior cerebellar artery and draining into the petrous sinus (Figure 2). She left our clinic on April 26, 1987, after medical treatment had produced complete remission of her symptoms.
Radiosurgery After a 12-month asymptomatic period, she underwent stereotactic radiosurgery with a gamma unit at the Karolinska Hospital, Stockholm, on May 17, 1988. The 10 x 13 x 10-mm nidus was covered by a 90% isodose volume of the 14-mm collimator, and a maximum dose of 24.0 Gy was used to irradiate the central part of the nidus, with the peripheral dose being 21.6 Gy.
Postoperative Course On admission to our clinic for a routine check 12 months after radiosurgery, there was no evidence of 0090-3019/92/$3.50
16
Surg Neurol 1992;37:15-21
Yamamoto et al
Figure 1. Sequential C T scans, (left) plain and (right) enhanced. (Upper) C T scan, taken 2 weeks after the onset, showed a right pontine hyperdense lesion with slight enhancement. ( ~ ) Plain C T scan, taken 19 months after treatment, demonstrated no density abnormality, (middle right) but enhanced C T revealed a hyperdense lesion. (Lower left) An equivocal hyperdense spot was identified by C T taken 28 months after treatment, with a smaller enhanced area (lower right) than was seen on the previous image (middle right).
neurological deficit. C o m p u t e d tomography revealed a pontine hyperdense lesion that was enhanced by contrast medium. The A V M was still clearly visible with
angiography, indicating that it had not been completely obliterated by the radiosurgery. She was seen on D e c e m b e r 15, 1989, following the
Radiation-Induced Edema by Radiosurgery
sudden development of facial nerve palsy and sensory impairment of the right side of the face associated with balance disturbance. Although nonenhanced CT scan revealed no density abnormalities, a small hyperdense lesion in the ports could be visualized on CT scan with enhancement (Figure 1, middle). Tl-weighted magnetic resonance imaging (MRI) demonstrated enlargement of the right half of the pons and an area of low intensity, corresponding to the hyperdense lesion seen on enhanced CT scan, which was significantly enhanced by gadolinium (Gd)-DTPA administration (Figure 3, upper and middle). T2-weighted MRI revealed a hyperintense zone surrounding the lesion in the pons and cerebellum (Figure 3, lower). Since these findings suggested radiation-induced edema, beta-methasone was given at a dose o f 16 mg daily for 4 weeks, then tapered off over 3 months. The patient responded to steroid treatment with a slight clinical improvement, but her symptoms never completely subsided. Angiography taken 2 years after irradiation demonstrated total obliteration of the AVM (Figure 4). Follow-up CT and MRI were performed in September 1990. Computed tomography showed a faint hyperdense spot in the right dorsal part of the pons with slight enhancement after contrast administration (Figure 1, lower), which appeared as a hypointense area on both T1- and T2-weighted MRIs with no significant enhancement after G d - D T P A administration (Figure 5). The edema within the pons and cerebellum, detected by previous MRI studies, had disappeared.
Surg Neurol 1992;37:15-21
17
Figure 2. Angiograms, taken a week after the onset, showedan arteriovenous malformation, fed by the anterior inferior cerebellararters and draining into the petrous rein.
Discussion With the increasing use of gamma units, more patients with AVM, acoustic neurinoma, pituitary adenoma, and so on are being treated by stereotactic radiosurgery [ 1 3]. Nevertheless, the incidence of postirradiation complications remains statistically insignificant. The overall incidence of permanent morbidity from radiosurgery for AVMs is estimated to be only 3.1% [4]. Radiation exposure to critical organs is considered insignificant in this treatment (less than 0.1 Gy). As previously mentioned, experience in using this treatment for brain stem lesions is limited. Therefore, little is known about the radiosensitivity of adjacent brain structures, such as the pons. For this reason, a peripheral dose of 21.6 Gy, generally considered a suboptimal dose, was given in this case. The optimal dose for AVM is more than 23 Gy. In our experience with radiosurgical treatment of acoustic neurinoma [3,6], irradiation of the portion of the pons facing the tumor with a dose of 18 Gy or slightly more has never resulted in permanent damage to the pons. Therefore, the dose given in this case was
18
Surg Neurol 1992;37:15-21
Figure 3. T l-weighted M R I (upper, SE 400/21) demonstrated a hypointense area in the pons with significant enhancement after G d - D T P A administration (middle). This lesion was surrounded by a hyperintense edematous area in the pons and cerebellum, as revealed by T2-weighted MRI (lower, SE 2500/150). This M R I study was performed at 0.5 T. 19 months after treatment.
Figure 4. Total obliteration of the arteriovenous malformation was confirmed by angiograms taken 24 months after irradiation.
x,O
20
Surg Neurol 1992;37:15-21
Yamamoto et al
Figure 5. The lesion, demonstrated as an abnormally enhanced area by the previous MRI study, was seen as a hypointense area on both Tl-weighted (upper, SE 500/20) and T2-weighted (lower, SE 2000/80) MRIs. (Middle) This lesion was not enhanced by Gd-DTPA administration. This MRI study was performed at 1.5 T, 28 months after treatment.
not considered to be dangerously high. We speculate that part of the pons, having been damaged by the preceding hemorrhage, was vulnerable to the ischemia that accompanies obliteration of the AVM. The sequential CT and MRI studies of this case could be considered to reveal a process of gradual AVM obliteration after radiosurgery. In the initial studies, per-
formed 19 months after treatment, isodensity with contrast enhancement on CT scan (Figure 1, middle), low intensity on Tl-weighted MRIs with partial gadolinium enhancement, and mixed intensity on T2-weighted MRIs (Figure 3) could suggest partial thrombosis of the nidus with minimal residual blood flow. However, in the study performed 28 months after irradiation, when
R a d i a t i o n - I n d u c e d E d e m a by Radiosurgery
total obliteration of the AVM had been confirmed angiographically, a hyperdense spot with minimal contrast enhancement (Figure 1, lower), low intensity on both T1- and T2-weighted MRIs and lack of gadolinium enhancement (Figure 5) suggested total thrombosis associated with accumulation of calcium and/or hemosiderin, and no residual blood flow. Thus, controlled studies of the long- and short-term sequelae of radiosurgical treatment of brain stem lesions should be conducted using MRI as well as CT. The authors thank Bierta E. Barfod, M.D., University of Washington School of Medicine, for her assistance in the preparation of this manuscript. This study was supported by scholarships from the Royal Swedish Academy of Sciences, the Japanese Society for the Promotion of Science, the Japan Private School Promotion Foundation, and the Dr. Itoe Okamoto International Exchange Fund.
Surg N e u r o l 1992:37:15-21
21
References I. Jimbo M. Radiotherapy of AVM: gamma-knife. In: Takakura K, ed. Treatment of cerebral and spinal arteriovenous malformations. Tokyo: Gendai-iryou-sha, 1988:117-28. 2. Lindquist C, Steiner L. Stereotactic radiosurgical treatment of arteriovenous malformations. In: Lunsford LD, ed. Modern stereotactic neurosurgery. Boston: Nijhoff, 1988:491-505. 3. Nor~n G, Arndt J, Hindmarsh T, Hirsch A. Stereotactic radiosurgical treatment of acoustic neurinomas. In: Lunsford LD, ed. Modern stereotactic neurosurgery. Boston: Nijhoff, 1988:481-9. 4. Steiner L. Possibilities and limits of radiosurgery in the treatment of intracranial tumors and arteriovenous malformations. Abstract of the 49th Annual Meeting of the Japan Neurosurgical Society, Tokyo, lc)90:IL-4. 5. Steiner L. Treatment of arteriovenous malformation by radiosurgery. In: Wilson CB, Stein BM, eds. lntracranial arteriovenous malformations. Baltimore: Williams & Wilkins, 1984:295-313. (~. Yamamoto M, Nordn G. Stereotactic radiosurgery in acoustic neurinomas. Neurol Surg (Tokyo) 1900; l 8:1101-6.