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Aneurysmal bone cyst of the skull
Surg Neurol 1986;25:145-8
145
Aneurysmal Bone Cyst of the Skull Hidetoshi Ikeda, M.D., Hiroshi Niizuma, M.D., and Takashi Yoshimoto, M.D. Division of Neurosurgery, Institute of Brain Diseases, Tohoku University School of Medicine, Sendai, Japan
lkeda H, Niizuma H, Yoshimoto T. Aneurysmal bone cyst of the skull. Surg Neurol 1986;25:145-8.
A case of a 48-year-old woman with aneurysmal bone cyst of the skull is reported. By using estrogen, which is one of the chemical embolizing agents, the abnormal vascular shadow disappeared and clinical symptoms were improved. The significance of selective external carotid angiography in the diagnosis of this lesion is discussed and the benefit of this therapeutic method is argued. KEYWORDS: Aneurysmal bone cyst; Skull; Arteriovenous fistula; Chemical embolization; Estrogen
We encountered a case o f unilateral exophthalmus with hyperemia o f the conjunctiva and thickening of the skull at the site o f a middle meningeal artery-diploic vein fistula. A histological study was not made in this case, but a diagnosis o f aneurysmal bone cyst was possible based upon x-ray and angiographic findings. By means of continuous arterial administration of conjugated estrogen, closure of the arteriovenous fistula and alleviation of symptoms was achieved. This case, together with a brief discussion of the pathology of this condition, is reported below. Case Report The patient was a 48-year-old woman presenting with right-sided exophthalmus and hyperemia of the right conjunctiva. There were no notable findings in her family history, but she had had a floating kidney since the age of 33, and she had her menopause at the early age of 33. From around 1972, a region of vascular dilatation developed on the superior lateral portion of the right orbit, where a pulse was palpable. The vascular dilatation disappeared after she slipped on the snow, bruising her hip, at the beginning of January 1982. In April of that Address reprint requests to." H. lkeda, M.D., Division of Neurosurgery, Institute of Brain Diseases, Tohoku University School of Medicine, Sendai 980, Japan. © 1986 by Elsevier Science PublishingCo., Inc.
year, she noted the appearance of right exophthalmus and right conjunctival congestion (Figure 1). The congestion worsened and there gradually appeared a pulsating right frontal headache and tinnitus. She was admitted to our clinic on December 10, 1982. A pulsating noise was audible at the right upper eyelid and there was venous congestion of the right fundus. Plain x-ray films of the skull showed that there was a bulge on the inner surface of the skull in the right frontoparietal region. In lateral view, a meandering radiolucent area with relatively distinct borders and surrounded by a somewhat sclerotic region was found (Figure 2). Moreover, enlargement of the vascular markings of the middle meningeal artery connected to this radiolucent area was also present. In computed tomography (CT) scans, no asymmetry of the external surface of the skull was seen, but there were two bulges from the inner surface of the lamina interna of the right frontoparietal bone with the coronal suture as a border. By changing the window level, we found this hypertrophic lesion to be an enlarged diploic space (Figure 3). A slight shift of the midline from right to left was also seen. In right carotid arteriograms, there was seen the development of the middle meningeal artery that fed into the anterior temporal and frontal diploic veins in the vicinity of the radiolucent area o f the parietal region. From there it fed the superior ophthalmic vein by way of the supraorbital vein (Figure 4). This circulatory route required 13 seconds to complete from the time of injection of the contrast medium. On December 24, 1982, canulation of the right external carotid artery was done and from the following day for a total of 9 days conjugated estrogen (Premarin, Ayerst Laboratories, New York, NY) was injected continuously at a rate o f 100 mg/day. Two days following the start of estrogen treatment, the conjunctival congestion began to improve and the pulsating noise over the right eye disappeared by the fourth day. On the ninth day, after it had been confirmed that visualization o f blood vessels was not possible distal from the tip o f the cannula in the right external carotid artery, the cannula was extracted. All clinical symptoms had disappeared and the patient was discharged on January 23, 1983. 0090-3019/86/$3.50
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Ikeda et al
Figure 1. Hyperemia of conjuncttva and exophthalmos of right eye.
Right external carotid arteriograms taken 8 months after she was discharged revealed neither the developed middle meningeal artery nor abnormal vascular shadows (Figure 5). Recurrence of symptoms has also not been seen.
Figure 3. CT scan showing the eccentricbulging area in the frontoparietal bone with enlargement of the diploic space.
Discussion In 1942, Jaffe and Lichtenstein introduced the concept of aneurysmal bone cyst as a lesion with characteristic x-ray findings. The bone surface showed eccentric processes, the internal structure of which had a soap-bubble
Figure 2. Plain skull film, lateral view, demonstrates soap bubble appearance in the radiolucent area of the right frontoparietal bone with faint marginal sclerosis.
or honeycombed appearance. Histologically, large and small vascular lumens that were separated due to diploic stroma and some of which were filled with liquid blood were found. Jaffe and Lichtenstein believed this lesion to be a distinct clinicopathological entity and labeled it "aneurysmal bone cyst." Aneurysmal bone cyst confined to the skull is extremely rare--amounting to no more than 37 reported cases, as far as we know [1-6,9,10,11,13,15-17,19,21]. The primary symptoms are local processes and mild headache. However, in the present case, exophthalmos, conjunctival hyperemia, venous congestion of the fundus, and an intracranial vascular noise were found, which have not been reported previously. Further symptoms unique to our case include the 10year continuation of the vascular dilatation in the lateral superior surface of the right orbit, followed by a 3month disappearance. These changes in symptomatology can likely be explained in terms of changes in the hemodynamics of the arteriovenous fistula. That is, initially, the blood flow from the arteriovenous fistula was from the diploic vein to the supraorbital vein to the middle temporal vein, and resulted in the vascular dilatation on the lateral surface of the right orbit. At around the time of the pelvic trauma, the blood flow is thought to have been changed to a route via the diploic vein to the supraorbital vein to the superior ophthalmic vein. As a consequence, the vascular dilatation of the right orbit disappeared and the venous pressure within the
Cranial Aneurysmal Bone Cyst
Surg Neurol 1986;25:145-8
147
:4 :!::ii!!i
A Figure 5. Right selective external carotid angiogram performed 8 months after the treatment. Neither the dilated middle meningeal artery nor the abnormal venous shadow could be seen.
B
Figure 4. Right selective external carotid angiogram, lateral view (A). anteroposterior view (B). These figures are produced by synthesis of both the arterial and the venous phase. An arteriovenous fistula between the dilated middle meningeal artery and the diploic vein can be seen. It took more than 10 minutes to visualize the abnormal venous shadou,.
eyeball increased, together with the appearance of exophthalmos and the conjunctival congestion. Jaffe noted that from the roentgenographical and histological findings of aneurysmal bone cyst, there is a large blood space into and out of which blood flows, but
he did not refer to any angiographic findings. However, using selective catheterization and subtraction techniques, it has now become possible to make detailed observations of the external carotid arterial system. If it is considered that the main feature of an aneurysmal bone cyst is a blood-filled cavity within a blow-out bone lesion, the importance of angiographic findings in the diagnosis of this lesion becomes evident. There have been few reports of the angiographic findings in cases of aneurysmal bone cysts and there have been marked differences according to the stage of the lesion [7,15]. Lindbom [14] has indicated that the unique characteristics in angiograms of aneurysmal bone cyst of long bones included the dilatation of the feeding arteries, the presence ofarteriovenous shunts, capillaries, and patchy density in the venous phase. Moreover, Ishiguro et a] [9] have reported a case in which, although enlargement of feeding arteries was not seen, abnormal shadows were visible for more than 10 seconds following injection of contrast medium at the site of the affected bone. In our case as well, an abnormal shadow of the diploic space was apparent for 13 seconds. In the x-ray films of the skull, the peripheral region of the radiolucent area was smooth with signs of sclerosis and showed a vascular channel from the middle meningeal artery. Such findings are said to be the result of gradual progression of the bony lesion (24) and are thought to be benign. The bony lesion involved both the frontal and parietal bones. That it was not confined to one bone is thought to be a characteristic feature of aneurysmal bone cysts (25).
148
Surg Neurol 1986;25:145-8
Various treatments of aneurysmal bone cysts, including curettage, cautery, resection, and excision, have been performed [25], but all such methods carry the risk of hemorrhage during the surgical procedure [8]. In cases in which the lesion cannot be approached for surgical treatment or in cases in which massive hemorrhage is feared, radiotherapy has been recommended [12]. There have been reports, however, of fibrous sarcomas [ 12,25 ] and osteogenic sarcomas [35] developing at the site of radiation several years following the radiotherapy of aneurysmal bone cysts. Among hypotheses concerning the pathogenesis of aneurysmal bone cysts, Lichtenstein's hypothesis concerning a local hemodynamic disturbance [14,20] was supported by other authors [25]. It is possible that if a local hemodynamic disturbance were the initial cause of the lesion, the condition might improve due to improvement of the abnormal hemodynamics. We have previously utilized a chemical embolization technique using estrogen in cases of dural arteriovenous malformations, meningiomas, etc. [18,22,23]. We used this method in this case of aneurysmal bone cyst for the first time and favorable results were obtained. In light of the fact that an aneurysmal bone cyst is a benign lesion in which an improvement in local hemodynamics can lead to recovery, this chemical embolization technique, though we have experienced only one case, can be recommended.
References 1. Bilge T, (~oban O, ()zden B, Turantan I, Tfirker K, Bahar S. Aneurysmal bone cyst of the occipital bone. Surg Neurol 1983;20:227-30. 2. Burns-Cox CJ, Higgins AT. Aneurysmal bone cyst of the frontal bone. J Bone Joint Surg 1969;51-B:344-5. 3. Cacdac MA, Malls LI, Anderson PJ. Aneurysmal parietal bone cyst. J Neurosurg 1972;37:237-41. 4. Cares HL, Bakay L. Giant cell lesions of the skull. Acta Neurochir 1971;35:1-18. 5. Chalapti Rao KV, Subba Rao B, Pulla Reddy C, Sundareshwar B, Reddy CRRM. Aneurysmal bone cyst of the skull: case report. J Neurosurg 1977;47:633-6. 6. Costantini FE, Iraci G, Benedetti A, Melanotte PL. Aneurysmai
Ikeda et al
bone cyst as an intracranial spaceoccupying lesion. J Neurosurg 1966;25:205-7. 7. Dabska M, Buraczewski J. Aneurysmal bone cyst. Cancer 1969;23:371-89. 8. Dahlin DC, Besse BE, Pugh DG, Ghormley RK. Aneurysmal bone cyst. Radiology 1955;64:56-65. 9. lshiguro S, Kimura A, Munemoto S, Yamashima T. Aneurysmal bone cyst of the frontal bone. Neurol Surg 1977;5:453-6. 10. Keuskamp PA, Horoupian DS, Fein JM. Aneurysmal bone cyst of the temporal bone presenting as a spontaneous intracerebral hemorrhage: case report. Neurosurgery 1980;7:166-70. 11. Lichtenstein L. Aneurysmal bone cyst: a pathological entity commonly mistaken for giant-cell tumor and occasionally for hemangioma and osteogenic sarcoma. Cancer 1950;3:279-89. 12. Lichtenstein L. Aneurysmal bone cyst: further observations. Cancer 1953;6:1228-37. 13. Lichtenstein L. Aneurysmal bone cyst: observations on fifty cases. J Bone Joint Surg 1957;39-A:873-82. 14. Lindbom A, S6derberg G, Spjut HJ, Sunnqvist O. Angiography of aneurysmal bone cyst. Acta Radiol 1961;55:12-6. 15. Luccarelli G, Fornari M, Savoiardo M. Angiography and computerized tomography in the diagnosis of aneurysmal bone cyst of the skull. J Neurosurg 1980;53:113-6. 16. MacCarty CS, Dahlin DC, Doyle JB, Lipscomb PR, Pugh DG. Aneurysmal bone cyst of the neural axis. J Neurosurg 1961;18:671-7. 17. Mufti ST. Aneurysmal bone cyst of the skull: case report. J Neurosurg 1978;49:730-3. 18. Nagamine Y, Komatsu S, Suzuki J. New embolization method using estrogen: effect of estrogen on microcirculation. Surg Neurol 1983;20:269-75. 19. Oki S, Shima T, Uozumi T, Kodama T: Aneurysmal bone cyst of the skull--a case report. Neurol Surg 1978;6:1197-201. 20. Phetan JT. Aneurysmal bone cyst. Surg Gynec Obstet 1964;119:979-83. 21. Ruiter DJ, Van Rijssel TH, Van der Velde EA. Aneurysmal bone cyst: a clinicopathological study of 105 cases. Cancer 1977;39:2231-9. 22. Suzuki J, Komatsu S. Estrogen in patient with chronic subdural hematoma. Surg Neurol 1977;8:243-7. 23. Suzuki J, Komatsu S. New embolization method using estrogen for dural arteriovenous malformation and meningioma. Surg Neurol 1981;16:438-42. 24. ThomasJE, Baker H L Assessment ofroentgenographiclucencies of the skull: a systemic approach. Neurology 1975;25:99-106. 25. Tillman BP, Dahlin DC, Lipscomb PR, Stewart JR. Aneurysmal bone cyst: an analysis of ninety-five cases. Mayo Clin Proc 1968;43:478-95.
145
Aneurysmal Bone Cyst of the Skull Hidetoshi Ikeda, M.D., Hiroshi Niizuma, M.D., and Takashi Yoshimoto, M.D. Division of Neurosurgery, Institute of Brain Diseases, Tohoku University School of Medicine, Sendai, Japan
lkeda H, Niizuma H, Yoshimoto T. Aneurysmal bone cyst of the skull. Surg Neurol 1986;25:145-8.
A case of a 48-year-old woman with aneurysmal bone cyst of the skull is reported. By using estrogen, which is one of the chemical embolizing agents, the abnormal vascular shadow disappeared and clinical symptoms were improved. The significance of selective external carotid angiography in the diagnosis of this lesion is discussed and the benefit of this therapeutic method is argued. KEYWORDS: Aneurysmal bone cyst; Skull; Arteriovenous fistula; Chemical embolization; Estrogen
We encountered a case o f unilateral exophthalmus with hyperemia o f the conjunctiva and thickening of the skull at the site o f a middle meningeal artery-diploic vein fistula. A histological study was not made in this case, but a diagnosis o f aneurysmal bone cyst was possible based upon x-ray and angiographic findings. By means of continuous arterial administration of conjugated estrogen, closure of the arteriovenous fistula and alleviation of symptoms was achieved. This case, together with a brief discussion of the pathology of this condition, is reported below. Case Report The patient was a 48-year-old woman presenting with right-sided exophthalmus and hyperemia of the right conjunctiva. There were no notable findings in her family history, but she had had a floating kidney since the age of 33, and she had her menopause at the early age of 33. From around 1972, a region of vascular dilatation developed on the superior lateral portion of the right orbit, where a pulse was palpable. The vascular dilatation disappeared after she slipped on the snow, bruising her hip, at the beginning of January 1982. In April of that Address reprint requests to." H. lkeda, M.D., Division of Neurosurgery, Institute of Brain Diseases, Tohoku University School of Medicine, Sendai 980, Japan. © 1986 by Elsevier Science PublishingCo., Inc.
year, she noted the appearance of right exophthalmus and right conjunctival congestion (Figure 1). The congestion worsened and there gradually appeared a pulsating right frontal headache and tinnitus. She was admitted to our clinic on December 10, 1982. A pulsating noise was audible at the right upper eyelid and there was venous congestion of the right fundus. Plain x-ray films of the skull showed that there was a bulge on the inner surface of the skull in the right frontoparietal region. In lateral view, a meandering radiolucent area with relatively distinct borders and surrounded by a somewhat sclerotic region was found (Figure 2). Moreover, enlargement of the vascular markings of the middle meningeal artery connected to this radiolucent area was also present. In computed tomography (CT) scans, no asymmetry of the external surface of the skull was seen, but there were two bulges from the inner surface of the lamina interna of the right frontoparietal bone with the coronal suture as a border. By changing the window level, we found this hypertrophic lesion to be an enlarged diploic space (Figure 3). A slight shift of the midline from right to left was also seen. In right carotid arteriograms, there was seen the development of the middle meningeal artery that fed into the anterior temporal and frontal diploic veins in the vicinity of the radiolucent area o f the parietal region. From there it fed the superior ophthalmic vein by way of the supraorbital vein (Figure 4). This circulatory route required 13 seconds to complete from the time of injection of the contrast medium. On December 24, 1982, canulation of the right external carotid artery was done and from the following day for a total of 9 days conjugated estrogen (Premarin, Ayerst Laboratories, New York, NY) was injected continuously at a rate o f 100 mg/day. Two days following the start of estrogen treatment, the conjunctival congestion began to improve and the pulsating noise over the right eye disappeared by the fourth day. On the ninth day, after it had been confirmed that visualization o f blood vessels was not possible distal from the tip o f the cannula in the right external carotid artery, the cannula was extracted. All clinical symptoms had disappeared and the patient was discharged on January 23, 1983. 0090-3019/86/$3.50
146
Surg Neurol 1986;25:145-8
Ikeda et al
Figure 1. Hyperemia of conjuncttva and exophthalmos of right eye.
Right external carotid arteriograms taken 8 months after she was discharged revealed neither the developed middle meningeal artery nor abnormal vascular shadows (Figure 5). Recurrence of symptoms has also not been seen.
Figure 3. CT scan showing the eccentricbulging area in the frontoparietal bone with enlargement of the diploic space.
Discussion In 1942, Jaffe and Lichtenstein introduced the concept of aneurysmal bone cyst as a lesion with characteristic x-ray findings. The bone surface showed eccentric processes, the internal structure of which had a soap-bubble
Figure 2. Plain skull film, lateral view, demonstrates soap bubble appearance in the radiolucent area of the right frontoparietal bone with faint marginal sclerosis.
or honeycombed appearance. Histologically, large and small vascular lumens that were separated due to diploic stroma and some of which were filled with liquid blood were found. Jaffe and Lichtenstein believed this lesion to be a distinct clinicopathological entity and labeled it "aneurysmal bone cyst." Aneurysmal bone cyst confined to the skull is extremely rare--amounting to no more than 37 reported cases, as far as we know [1-6,9,10,11,13,15-17,19,21]. The primary symptoms are local processes and mild headache. However, in the present case, exophthalmos, conjunctival hyperemia, venous congestion of the fundus, and an intracranial vascular noise were found, which have not been reported previously. Further symptoms unique to our case include the 10year continuation of the vascular dilatation in the lateral superior surface of the right orbit, followed by a 3month disappearance. These changes in symptomatology can likely be explained in terms of changes in the hemodynamics of the arteriovenous fistula. That is, initially, the blood flow from the arteriovenous fistula was from the diploic vein to the supraorbital vein to the middle temporal vein, and resulted in the vascular dilatation on the lateral surface of the right orbit. At around the time of the pelvic trauma, the blood flow is thought to have been changed to a route via the diploic vein to the supraorbital vein to the superior ophthalmic vein. As a consequence, the vascular dilatation of the right orbit disappeared and the venous pressure within the
Cranial Aneurysmal Bone Cyst
Surg Neurol 1986;25:145-8
147
:4 :!::ii!!i
A Figure 5. Right selective external carotid angiogram performed 8 months after the treatment. Neither the dilated middle meningeal artery nor the abnormal venous shadow could be seen.
B
Figure 4. Right selective external carotid angiogram, lateral view (A). anteroposterior view (B). These figures are produced by synthesis of both the arterial and the venous phase. An arteriovenous fistula between the dilated middle meningeal artery and the diploic vein can be seen. It took more than 10 minutes to visualize the abnormal venous shadou,.
eyeball increased, together with the appearance of exophthalmos and the conjunctival congestion. Jaffe noted that from the roentgenographical and histological findings of aneurysmal bone cyst, there is a large blood space into and out of which blood flows, but
he did not refer to any angiographic findings. However, using selective catheterization and subtraction techniques, it has now become possible to make detailed observations of the external carotid arterial system. If it is considered that the main feature of an aneurysmal bone cyst is a blood-filled cavity within a blow-out bone lesion, the importance of angiographic findings in the diagnosis of this lesion becomes evident. There have been few reports of the angiographic findings in cases of aneurysmal bone cysts and there have been marked differences according to the stage of the lesion [7,15]. Lindbom [14] has indicated that the unique characteristics in angiograms of aneurysmal bone cyst of long bones included the dilatation of the feeding arteries, the presence ofarteriovenous shunts, capillaries, and patchy density in the venous phase. Moreover, Ishiguro et a] [9] have reported a case in which, although enlargement of feeding arteries was not seen, abnormal shadows were visible for more than 10 seconds following injection of contrast medium at the site of the affected bone. In our case as well, an abnormal shadow of the diploic space was apparent for 13 seconds. In the x-ray films of the skull, the peripheral region of the radiolucent area was smooth with signs of sclerosis and showed a vascular channel from the middle meningeal artery. Such findings are said to be the result of gradual progression of the bony lesion (24) and are thought to be benign. The bony lesion involved both the frontal and parietal bones. That it was not confined to one bone is thought to be a characteristic feature of aneurysmal bone cysts (25).
148
Surg Neurol 1986;25:145-8
Various treatments of aneurysmal bone cysts, including curettage, cautery, resection, and excision, have been performed [25], but all such methods carry the risk of hemorrhage during the surgical procedure [8]. In cases in which the lesion cannot be approached for surgical treatment or in cases in which massive hemorrhage is feared, radiotherapy has been recommended [12]. There have been reports, however, of fibrous sarcomas [ 12,25 ] and osteogenic sarcomas [35] developing at the site of radiation several years following the radiotherapy of aneurysmal bone cysts. Among hypotheses concerning the pathogenesis of aneurysmal bone cysts, Lichtenstein's hypothesis concerning a local hemodynamic disturbance [14,20] was supported by other authors [25]. It is possible that if a local hemodynamic disturbance were the initial cause of the lesion, the condition might improve due to improvement of the abnormal hemodynamics. We have previously utilized a chemical embolization technique using estrogen in cases of dural arteriovenous malformations, meningiomas, etc. [18,22,23]. We used this method in this case of aneurysmal bone cyst for the first time and favorable results were obtained. In light of the fact that an aneurysmal bone cyst is a benign lesion in which an improvement in local hemodynamics can lead to recovery, this chemical embolization technique, though we have experienced only one case, can be recommended.
References 1. Bilge T, (~oban O, ()zden B, Turantan I, Tfirker K, Bahar S. Aneurysmal bone cyst of the occipital bone. Surg Neurol 1983;20:227-30. 2. Burns-Cox CJ, Higgins AT. Aneurysmal bone cyst of the frontal bone. J Bone Joint Surg 1969;51-B:344-5. 3. Cacdac MA, Malls LI, Anderson PJ. Aneurysmal parietal bone cyst. J Neurosurg 1972;37:237-41. 4. Cares HL, Bakay L. Giant cell lesions of the skull. Acta Neurochir 1971;35:1-18. 5. Chalapti Rao KV, Subba Rao B, Pulla Reddy C, Sundareshwar B, Reddy CRRM. Aneurysmal bone cyst of the skull: case report. J Neurosurg 1977;47:633-6. 6. Costantini FE, Iraci G, Benedetti A, Melanotte PL. Aneurysmai
Ikeda et al
bone cyst as an intracranial spaceoccupying lesion. J Neurosurg 1966;25:205-7. 7. Dabska M, Buraczewski J. Aneurysmal bone cyst. Cancer 1969;23:371-89. 8. Dahlin DC, Besse BE, Pugh DG, Ghormley RK. Aneurysmal bone cyst. Radiology 1955;64:56-65. 9. lshiguro S, Kimura A, Munemoto S, Yamashima T. Aneurysmal bone cyst of the frontal bone. Neurol Surg 1977;5:453-6. 10. Keuskamp PA, Horoupian DS, Fein JM. Aneurysmal bone cyst of the temporal bone presenting as a spontaneous intracerebral hemorrhage: case report. Neurosurgery 1980;7:166-70. 11. Lichtenstein L. Aneurysmal bone cyst: a pathological entity commonly mistaken for giant-cell tumor and occasionally for hemangioma and osteogenic sarcoma. Cancer 1950;3:279-89. 12. Lichtenstein L. Aneurysmal bone cyst: further observations. Cancer 1953;6:1228-37. 13. Lichtenstein L. Aneurysmal bone cyst: observations on fifty cases. J Bone Joint Surg 1957;39-A:873-82. 14. Lindbom A, S6derberg G, Spjut HJ, Sunnqvist O. Angiography of aneurysmal bone cyst. Acta Radiol 1961;55:12-6. 15. Luccarelli G, Fornari M, Savoiardo M. Angiography and computerized tomography in the diagnosis of aneurysmal bone cyst of the skull. J Neurosurg 1980;53:113-6. 16. MacCarty CS, Dahlin DC, Doyle JB, Lipscomb PR, Pugh DG. Aneurysmal bone cyst of the neural axis. J Neurosurg 1961;18:671-7. 17. Mufti ST. Aneurysmal bone cyst of the skull: case report. J Neurosurg 1978;49:730-3. 18. Nagamine Y, Komatsu S, Suzuki J. New embolization method using estrogen: effect of estrogen on microcirculation. Surg Neurol 1983;20:269-75. 19. Oki S, Shima T, Uozumi T, Kodama T: Aneurysmal bone cyst of the skull--a case report. Neurol Surg 1978;6:1197-201. 20. Phetan JT. Aneurysmal bone cyst. Surg Gynec Obstet 1964;119:979-83. 21. Ruiter DJ, Van Rijssel TH, Van der Velde EA. Aneurysmal bone cyst: a clinicopathological study of 105 cases. Cancer 1977;39:2231-9. 22. Suzuki J, Komatsu S. Estrogen in patient with chronic subdural hematoma. Surg Neurol 1977;8:243-7. 23. Suzuki J, Komatsu S. New embolization method using estrogen for dural arteriovenous malformation and meningioma. Surg Neurol 1981;16:438-42. 24. ThomasJE, Baker H L Assessment ofroentgenographiclucencies of the skull: a systemic approach. Neurology 1975;25:99-106. 25. Tillman BP, Dahlin DC, Lipscomb PR, Stewart JR. Aneurysmal bone cyst: an analysis of ninety-five cases. Mayo Clin Proc 1968;43:478-95.