The term "radiosurgery" describes several related
techniques that combine stereotactic approaches to achieve precise three-dimensional
localization of highly focused, high-energy radiation. This
procedure allows for the delivery of a very large dose of radiation
to a small intracranial lesion while achieving rapid fall-off in dose
outside the target volume. Since Leksell pioneered the technique in
1951, radiosurgery has proven to be an effective alternative to
conventional neurosurgery or brachytherapy in the management of
selected small intracranial tumors. It is also an alternative to
surgery and/or intravascular embolization for the treatment of
patients who have arteriovenous malformations (AVMs).
Currently, there are three broad types of radiosurgical devices,
which are distinguishable from one another by the type and source of
high-energy radiation utilized. The gamma knife uses a hemispherical
array of radioactive cobalt-60 sources that emit gamma-ray photons.
With this device, 201 fixed, separate beams precisely converge on an
isocenter. Selection of a subset of these beams modifies the shape of
the irradiated volume to more closely match a specific target.
Linear accelerator-based radiosurgery uses x-ray photons that are
produced in a collision between accelerated electrons and a metal
target. Conventional linear accelerators are mounted on a gantry that
has a fixed axis of rotation. By rotating both the linear accelerator
and treatment couch, multiple intersecting arc fields can be produced
that concentrate the radiation dose at a precise isocenter.
The third form of radiosurgery uses heavy particles, such as protons
or heliumions, generated by massive accelerators, such as cyclotrons
or synchrotrons. These positively charged particles deliver most of
their radiation dose at a set depth in tissue that is determined by
energy. This allows for the delivery of high doses to small targets
with little radiation dose to surrounding normal tissues.
All three radiosurgical instruments utilize an external frame of
reference, which is attached to the patients head. This device
is needed for spatial localization of the target and cranial
immobilization during treatment.
This article surveys the clinical results and complications of
radiosurgery for the treatment of metastatic tumors, primary gliomas,
AVMs, and benign conditions, including pituitary tumors, acoustic
neuromas, and meningiomas. These results are derived from a
cross-section of published data and our experience treating patients
with these tumors at Stanford University Medical Center.
The treatment of brain metastases is the most common application of
radiosurgery due to the high incidence of this disease. The American
Cancer Society estimates that 170,000 cancer patients develop
cerebral metastases each year in the United States. Because most
patients with metastases eventually succumb to their underlying
malignancy, the primary benefits of radiosurgery are palliation of
symptoms and some modest prolongation of survival.
Radiosurgery produces median survival (6.4 to 10 months)[3-10]
comparable to that after surgical resection followed by conventional
fractionated radiotherapy (4 to 13 months),[11,12] with good local
control (Table 1 and
Figure 1).[3-9,13,14] Two studies have shown that patients
treated with radiosurgery for either one or two brain metastases have
prolonged survival equivalent to that achieved with surgical resection.[15,16]
Selection criteria for radiosurgery generally include: (1) limited
number of brain metastasis (typically three or less), (2) maximal
tumor diameter < 3.5 cm for each lesion, (3) suitable target
shape, and (4) absent or stable disease at the primary and other
extracranial sites. Surgical resection may be preferable to
radiosurgery for the treatment of brain metastases in two clinical
situations: when the primary source is unknown, and when there are
significant symptoms attributable to mass effect and edema unrelieved
by corticosteroids. Surgical resection typically relieves symptoms
more promptly than does radiosurgery.
Radiosurgery is preferable to surgery in patients whose medical
condition precludes craniotomy, those with tumors located in eloquent
cerebral regions, and those who refuse surgery. Radiosurgery avoids
the perioperative morbidity and mortality that craniotomy entails.
Furthermore, several tumors can be radiated during one outpatient
In general, radiosurgical ablation of brain metastases is followed by
whole-brain fractionated radiotherapy to minimize the likelihood of
regional relapse. Although radiosurgery can be used without
subsequent whole-brain fractionated radiotherapy, this approach to
brain metastases remains investigational. Unlike conventional brain
irradiation, radiosurgery can be repeated for meta-chronous lesions
months to years after initial treatment.
Before the advent of radiosurgery, treatment of pituitary tumors
consisted of surgical resection, medical management with
pharmacologic suppression using such agents as bromocriptine
(Parlodel) and somatostatin, or fractionated external-beam-radiotherapy,
which is often the preferred treatment for bulky tumors with
suprasellar extension. Most pituitary tumors are resectable with a
transsphenoidal approach. The recurrence rate after this procedure
ranges from 8% to 15%, with mortality varying from 0.3% to
1.8%.[17-20] Among hormone-secreting pituitary tumors, hormonal
control rates range from 42% to 86%, depending on the type of
Morbidity and mortality following surgical resection of pituitary
tumors are higher among patients who have recurrent disease or
significant intercurrent medical conditions. Radiosurgery is a
particularly attractive alternative to resection in these settings.
There is considerable experience with fractionated radiotherapy in
the management of pituitary tumors. When this treatment is used
alone, 10-year tumor control rates for pituitary tumors range from
77% to 87%.[21,22] However, the rates of pituitary dysfunction in one
study were 35% for thyroxine, 32% for glucocorticoids, and 33% for
sex hormones. Overall complication rates from fractionated
radiotherapy range from 3% to 7%.[22,23] Complications include
injuries to the visual tracts, late secondary malignancies, and rare
Although several small series report high control rates after
radiosurgery for small primary or recurrent pituitary tumors (Table
2),[3,24-26] follow-up has been limited to 2 to 5 years.
Reported rates of recurrence vary from 0% to 2%. Hormonal cure rates
after radiosurgery have been reported to range from 48% to 100%
depending on the subtype of tumor.[3,24-27] Treatment is most
successful for patients with prolactinoma, acromegaly, or
Cushings disease and least effective in those rare patients
with Nelsons syndrome.
Large pituitary tumors (> 3.5 cm) or tumors closer than 3 mm to
the optic nerve or chiasm cannot be treated by radiosurgery without a
significant risk of radiation injury to the optic apparatus.
Alternative strategies for such patients include: (1) combined
surgical resection and radiosurgery (with radiosurgery reserved for
treatment of any residual sellar and cavernous sinus tumor once it
has been debulked away from the optic apparatus), or (2) conventional
Regardless of the treatment approach employed, all patients with
pituitary tumors require serial endocrinologic studies to document
changes in hormonal function and allow for institution of hormonal
replacement if hypopituitarism develops. Patients who develop
recurrent pituitary adenoma after fractionated radiotherapy to the
pituitary region may be treatable with radiosurgery, although the
risks of radiation injury are not well defined in this setting.
Because small- to moderate-sized acoustic neuromas typically produce
hearing loss leading to diagnosis, these tumors are ideal targets for
radiosurgery. Acoustic neuromas occur as sporadic unilateral tumors
or as part of the genetic syndrome, type II neurofibromatosis
(bilateral tumors). Although these lesions are surgically
approachable, surgery entails a high probability of hearing loss and
a lower, but moderate, rate of facial nerve dysfunction.
Among 749 patients with acoustic neuroma from three surgical series,
only 15% to 37% retained hearing and approximately 20% had injury to
the facial nerve resulting in partial or complete facial
palsy.[28-30] Complete resection was achieved in 90% of
patients,[28-30] and only 1% of these tumors recurred over 5-year
follow-up. However, 10% recurred within 5 years if resection was incomplete.
A 1992 National Institutes of Health consensus conference recognized
the promising role of radiosurgery in the treatment of acoustic
neuroma. Several large series of patients treated with
radiosurgery for acoustic neuroma have been compiled (Table
3).[32-35] Across all of these series, 51% of patients had
hearing preserved and more than 90% retained normal facial nerve function.[32-35]
Although the results of radiosurgical treatment of acoustic neuroma
described above represent an improvement in cranial nerve
preservation compared to conventional surgery, these patients were
treated with single large fractions. Recent trends toward the use of
fractionated radiosurgery have further increased rates of hearing preservation.
In an ongoing series of patients at Stanford treated with three
fractions delivered over 36 hours, hearing was preserved in 88% of
patients at 1 year. Hearing was maintained more often in patients
with unilateral tumors than in those with neurofibromatosis type II
(100% vs 71%; P = .09). Two patients experienced temporary partial
facial numbness, but there have been no facial nerve injuries.
The radiosurgical end point of treatment is reduction or
stabilization in tumor size over several years. This result has been
achieved in 93% of patients reported in the radiosurgical literature
(55% to 63% of tumors decreased and 33% to 37% stabilized over 1
year; 78% of tumors decreased over 3 years).[32-35] Our experience at
Stanford parallels these results (Figure
Patients with recurrent acoustic tumors after resection and those in
whom craniotomy is associated with significant risk also represent
ideal candidates for radiosurgery. Despite the encouraging studies
reported in the literature, follow-up, both in terms of tumor control
and complications, is relatively short, given the long natural
history of acoustic neuroma. In addition, use of radiosurgery is
limited to the treatment of small tumors; large acoustic neuromas
must still be treated with surgical resection.
1. Leksell L: The stereotactic method and radiosurgery of the brain.
Acta Chir Scand 102:316-319, 1951.
2. Posner J: Management of brain metastases. Rev Neurol 148:477-487, 1992.
3. Steiner L, Prasad D, Lindquist C, et al: Gamma knife surgery in
vascular, neoplastic, and functional disorders of the nervous system,
in Schmidek HH, Sweet WH (eds): Operative Neurosurgical Techniques,
vol 2, pp 667-694. Philadelphia, WB Saunders, 1994.
4. Loeffler J, Alexander III E: Radiosurgery for the treatment of
intracranial metastasis, in Alexander III E, Loeffler J, Lunsford LD
(eds): Stereotactic Radiosurgery, pp 197-206. New York, McGraw-Hill, 1993.
5. Coffey RJ, Flickinger JC, Bissonette DJ, et al: Radiosurgery for
solitary brain metastases using the cobalt-60 gamma unit: Methods and
results in 24 patients. Int J Radiat Oncol Biol Phys 20:1287-1295, 1991.
6. Kihlstrom L, Karlsson B, Lindquist C: Gamma knife surgery for
cerebral metastases: Implications for survival based on 16 years
experience. Stereotact Funct Neurosurg 61(suppl 1):45-50, 1993.
7. Engenhart R, Kimmig BN, Hover KH, et al: Long-term follow-up for
brain metastases treated by percutaneous stereotactic single
high-dose irradiation. Cancer 71:1353-1361, 1993.
8. Mehta MP, Rozental JM, Levin AB, et al: Defining the role of
radiosurgery in the management of brain metastases. Int J Radiat
Oncol Biol Phys 24:619-625, 1992.
9. Valentino V, Mirri MA, Schinaia G et al: Linear accelerator and
Greitz-Bergstroms head fixation system in radiosurgery of
single cerebral metastases: A report of 86 cases. Acta Neurochir
(Wien) 121:140-145, 1993.
10. Flickinger JC, Kondziolka D, Lunsford LD, et al: A
multi-institutional experience with stereotactic radiosurgery for
solitary brain metastasis [see comments]. Int J Radiat Oncol Biol
Phys 28:797-802, 1994.
11. Sundaresan N, Galicich JH: Surgical treatment of brain
metastases: Clinical and computerized tomography evaluation of the
results of treatment. Cancer 55:1382-1388, 1985.
12. Ferrara M, Bizzozzero L, Talamonti G, et al: Surgical treatment
of 100 single brain metastases: Analysis of the results. J Neurosurg
Sci 34:303-308, 1990.
13. Sturm V, Kimmig B, Engenhardt R, et al: Radiosurgical treatment
of cerebral metastases: Method, indications and results. Stereotact
Funct Neurosurg 57:7-10, 1991.
14. Somaza S, Kondziolka D, Lunsford LD, et al: Stereotactic
radiosurgery for cerebral metastatic melanoma. J Neurosurg
15. Alexander E, Moriarty TM, Davis RB, et al: Stereotactic
radiosurgery for the definitive, noninvasive treatment of brain
metastasis. J Natl Cancer Inst 87:34-40, 1995.
16. Joseph J, Adler JR, Cox RS, et al: Linear accelerator-based
stereotactic radiosurgery for brain metastases: The influence of
number of lesions on survival. J Clin Oncol 14:1085-1092, 1996.
17. Mindermann T, Wilson CB: Pediatric pituitary adenomas.
Neurosurgery 36:259-268; 269 (discussion), 1995.
18. Petruson B, Jakobsson KE, Elfverson J, et al: Five-year follow-up
of nonsecreting pituitary adenomas. Arch Otolaryngol Head Neck Surg
19. Dyer EH, Civit T, Visot A, et al: Transsphenoidal surgery for
pituitary adenomas in children. Neurosurgery 34:207-212; 212
20. Laws E: Surgical management of pituitary tumors, in Mazzaferri E,
Samaan N (eds): Endocrine Tumors, pp 215-222. Boston, Blackwell
21. Hughes MN, Lamas KJ, Yelland ME, et al: Pituitary adenomas:
Long-term results for radiotherapy alone and post-operative
radiotherapy. Int J Radiat Oncol Biol Phys 27:1035-1043, 1993.
22. Tsang RW, Brierley JD, Panzarella T, et al: Radiation therapy for
pituitary adenoma: Treatment outcome and prognostic factors. Int J
Radiat Oncol Biol Phys 30:557-565, 1994.
23. Fisher BJ, Gaspar LE, Noone B: Radiation therapy of pituitary
adenoma: Delayed sequelae. Radiology 187:843-846, 1993.
24. Ganz JC, Backlund EO, Thorsen FA: The effects of gamma knife
surgery of pituitary adenomas on tumor growth and endocrinopathies.
Stereotact Funct Neurosurg 61(suppl 1):30-37, 1993.
25. Stephanian E, Lunsford LD, Coffey RJ, et al: Gamma knife surgery
for sellar and suprasellar tumors. Neurosurg Clin North Am 3:207-218, 1992.
26. Valentino V: Postoperative radiosurgery of pituitary adenomas. J
Neurosurg Sci 35:207-211, 1991.
27. Thoren M: Stereotactic radiosurgery with the cobalt-60 gamma unit
in the treatment of growth hormone-producing pituitary tumors.
Neurosurgery 29:663-668, 1991.
28. Ojemann RG: Management of acoustic neuromas (vestibular
schwannomas) [honored guest presentation]. Clin Neurosurg 40:498-535, 1993.
29. Glasscock ME, Hays JW, Minor LB, et al: Preservation of hearing
in surgery for acoustic neuromas [see comments]. J Neurosurg
30. Pellet W, Emram B, Cannoni M, et al: Functional results of the
surgery of unilateral acoustic neuroma. Neurochirurgie 39:24-40;
40-21 (discussion), 1993.
31. Eldridge R, Parry D: Vestibular schwannoma (acoustic neuroma):
Consensus development conference [see comments]. Neurosurgery
32. Lindquist C, Steiner L: Radiosurgery for tumors, in Wilkins R,
Rengachary S (eds): Neurosurgery, pp 1887-1908. New York,
33. Flickinger JC, Lunsford LD, Linskey ME, et al: Gamma knife
radiosurgery for acoustic tumors: Multivariate analysis of four year
results. Radiother Oncol 27:91-98, 1993.
34. Noren G, Greitz D, Hirsch A, et al: Gamma knife surgery in
acoustic tumours. Acta Neurochir (Wien) 58(suppl):104-107, 1993.
35. Mendenhall WM, Friedman WA, Bova FJ: Linear accelerator-based
stereotactic radiosurgery for acoustic schwannomas [see comments].
Int J Radiat Oncol Biol Phys 28:803-810, 1994.
36. Chang SD, Adler JR: The treatment of skull base meningiomas with
LINAC radiosurgery. Neurosurgery 41:1022-1029, 1997.
37. Kondziolka D, Lunsford LD, Coffey RJ, et al: Stereotactic
radiosurgery of meningiomas. J Neurosurg 74:552-559, 1991.
38. Kondziolka D, Lunsford LD: Radiosurgery of meningiomas. Neurosurg
Clin North Am 3:219-230, 1992.
39. Chang SD, Adler JR: Stereotactic radiosurgery for cavernous sinus
meningiomas: Clinical and radiologic results. J Neurosurg 86:359A, 1997.
40. Ciric I, Landau B: Tentorial and posterior cranial fossa
meningiomas: Operative results and long term follow up: Experience
with 26 cases. Surg Neurology 39:530-537, 1993.
41. DeMonte F, Smith HK, al-Mefty O: Outcome of aggressive removal of
cavernous sinus meningiomas. J Neurosurg 81:245-251, 1994.
42. Mahmood A, Qureshi NH, Malik GM: Intracranial meningiomas:
Analysis of recurrence after surgical treatment. Acta Neurochiurgica
43. Jaaskelainen J: Seemingly complete removal of histologically
benign intracranial meningioma: Late recurrence rate and factors
predicting recurrence in 657 patients: A multivariate analysis. Surg
Neurol 26:461-469, 1986.
44. Steiner L, Lindquist C, Steiner M: Radiosurgery. Adv Tech Stand
Neurosurg 19:19-102, 1992.
45. Duma CM, Lunsford LD, Kondziolka D, et al: Stereotactic
radiosurgery of cavernous sinus meningiomas as an addition or
alternative to microsurgery. Neurosurgery 32:699-704; 704-695
46. Engenhart R, Kimmig BN, Hover KH, et al: Stereotactic single
high-dose radiation therapy of benign intracranial meningiomas. Int J
Radiat Oncol Biol Phys 19:1021-1026, 1990.
47. Valentino V, Schinaia G, Raimondi AJ: The results of
radiosurgical management of 72 middle fossa meningiomas. Acta
Neurochir (Wien) 122:60-70, 1993.
48. Wilson CB: Meningiomas: Genetics, malignancy, and the role of
radiation in induction and treatment: The Richard C. Schneider
lecture. J Neurosurg 81:666-675, 1994.
49. Miralbell R, Linggood RM, de la Monte S, et al: The role of
radiotherapy in the treatment
of subtotally resected benign meningiomas. J Neurooncol 13:157-164, 1992.
50. Barbaro NM, Gutin PH, Wilson CB, et al: Radiation therapy in the
treatment of partially resected meningiomas. Neurosurgery 20:525-528, 1987.
51. Simpson JR, Horton J, Scott C, et al: Influence of location and
extent of surgical resection on survival of patients with
glioblastoma multiforme: Results of three consecutive Radiation
Therapy Oncology Group (RTOG) clinical trials. Int J Radiat Oncol
Biol Phys 26:239-244, 1993.
52. Werner-Wasik M, Scott CB, Nelson DF, et al: Final report of a
phase I/II trial of hyperfractionated and accelerated
hyperfractionated radiation therapy with carmustine for adults with
supratentorial malignant gliomas: Radiation Therapy Oncology Group
Study. Cancer 77:1535-1543, 1996.
53. Jeremic B, Grujicic D, Antunovic V, et al: Accelerated
hyperfractionated radiation therapy for malignant glioma: A phase II
study. Am J Clin Oncol 18:449-453, 1995.
54. Buatti JM, Friedman WA, Bova FJ et al: LINAC radiosurgery for
high-grade gliomas: The University of Florida experience. Int J
Radiat Oncol Biol Phys 32:205-210, 1995.
55. Larson DA, Gutin PH, McDermott M, et al: Gamma knife for glioma:
Selection factors and survival. Int J Radiat Oncol Biol Phys
56. Kondziolka D, Flickinger JC, Bissonette DJ, et al: Survival
benefit of stereotactic radiosurgery for patients with malignant
glial neoplasms. Neurosurgery 41:776-785, 1997.
57. Brown RD, Jr., Wiebers DO, Forbes G, et al: The natural history
of unruptured intracranial arteriovenous malformations. J Neurosurg
58. Morgan MK, Johnston IH, Hallinan JM, et al: Complications of
surgery for arteriovenous malformations of the brain [see comments].J
Neurosurg 78:176-182, 1993.
59. Piepgras DG, Sundt TM, Jr, Ragoowansi AT, et al: Seizure outcome
in patients with surgically treated cerebral arteriovenous
malformations. J Neurosurg 78:5-11, 1993.
60. Heros RC, Korosue K, Diebold PM: Surgical excision of cerebral
arteriovenous malformations: Late results. Neurosurgery 26:570-577;
577-578 (discussion), 1990.
61. Yasargil M: Summary of operative results, in Microsurgery, pp
369-393. New York, Thieme, 1988.
62. Stein BM: Arteriovenous malformations of the medial cerebral
hemisphere and the limbic system. J Neurosurg 60:23-31, 1984.
63. Lunsford LD, Kondziolka D, Bissonette DJ, et al: Stereotactic
radiosurgery of brain vascular malformations. Neurosurg Clin North Am
64. Steinberg GK, Fabrikant JI, Marks MP, et al: Stereotactic
heavy-charged-particle Bragg-peak radiation for intracranial
arteriovenous malformations [see comments]. N Engl J Med 323:96-101, 1990.
65. Steiner L, Lindquist C, Adler JR, et al: Clinical outcome of
radiosurgery for cerebral arteriovenous malformations. J Neurosurg
66. Chang SD, Shuster DL, Steinberg GK, et al: Stereotactic
radiosurgery of arteriovenous malformations: Pathologic changes in
resected tissue. Clin Neuropathol 16:111-116, 1997.
67. Colombo F, Pozza F, Chierego G, et al: Linear accelerator
radiosurgery of cerebral arteriovenous malformations: An update.
Neurosurgery 34:14-21, 1994.
68. Friedman WA, Bova FJ, Mendenhall WM: Linear accelerator
radiosurgery for arteriovenous malformations: The relationship of
size to outcome. J Neurosurg 82:180-189, 1995.
69. Kondziolka D, Lunsford LD, Flickinger J: Gamma knife stereotactic
radiosurgery for cerebral vascular malformations, in Alexander E,
Loeffler JS, Lunsford LD (eds): Stereotactic Radiosurgery, pp
136-146. New York, McGraw-Hill, 1993.
70. Sutcliffe JC, Forster DM, Walton L, et al: Untoward clinical
effects after stereotactic radiosurgery for intracranial
arteriovenous malformations. Br J Neurosurg 6:177-185, 1992.
71. Sheline GE, Wara WM, Smith V: Therapeutic irradiation and brain
injury. Int J Radiat Oncol Biol Phys 6:1215-1228, 1980.
72. Loeffler JS, Siddon RL, Wen PY, et al: Stereotactic radiosurgery
of the brain using a standard linear accelerator: A study of early
and late effects. Radiother Oncol 17:311-321, 1990.
73. Bodis S, Alexander Er, Kooy H, et al: The prevention of
radiosurgery-induced nausea and vomiting by ondansetron: Evidence of
a direct effect on the central nervous system chemoreceptor trigger
zone. Surg Neurol 42:249-252, 1994.
74. Kjellberg RN, Davis KR, Lyons S, et al: Bragg peak proton beam
therapy for arteriovenous malformation of the brain. Clin Neurosurg
75. Adams JH, Graham DI: Trauma, in An Introduction to
Neuropathology, pp 152-154. London, Churchill Livingstone, 1994.
76. Adler JR, Cox RS, Kaplan I, et al: Stereotactic radiosurgical
treatment of brain metastasis. J Neurosurg 76:444-449, 1992.
77. Linskey ME, Lunsford LD, Flickinger JC: Radiosurgery for acoustic
neurinomas: Early experience. Neurosurgery 26:736-744; 744-745
78. Linskey ME, Lunsford LD, Flickinger JC: Neuroimaging of acoustic
nerve sheath tumors after stereotaxic radiosurgery. Am J Neuroradiol
79. Linskey M, Lunsford L, Flickinger J: Tumor control after
stereotactic radiosurgery in neurofibromatosis patients with
bilateral acoustic tumors. Neurosurgery 31:829-839, 1992.
80. Linskey ME, Flickinger JC, Lunsford LD: Cranial nerve length
predicts the risk of delayed facial and trigeminal neuropathies after
acoustic tumor stereotactic radiosurgery. Int J Radiat Oncol Biol
Phys 25:227-233, 1993.
81. Degerblad M, Rahn T, Bergstrand G, et al: Long-term results of
stereotactic radiosurgery to the pituitary gland in Cushings
disease. Acta Endocrinol (Copenh) 112:310-314, 1986.
82. Nedzi LA, Kooy H, Alexander ED, et al: Variables associated with
the development of complications from radiosurgery of intracranial
tumors. Int J Radiat Oncol Biol Phys 21:591-599, 1991.
83. McKenzie MR, Souhami L, Caron JL, et al: Early and late
complications following dynamic stereotactic radiosurgery and
fractionated stereotactic radiotherapy. Can J Neurol Sci 20:279-285, 1993.
84. Laing RW, Warrington AP, Graham J, et al: Efficacy and toxicity
of fractionated stereotactic radiotherapy in the treatment of
recurrent gliomas (phase I/II study). Radiother Oncol 27:22-29, 1993.
85. Steiner L: Stereotactic radiosurgery with the cobalt-60 gamma
unit in the surgical treatment of intracranial tumors and
arteriovenous malformations, in Schmidek HH, Sweet WH (eds):
Operative Neurosurgical Techniques--Indications, Methods, and
Results, pp 515-529. Philadelphia, WB Saunders, 1988.