Radiation exposure of normal temporal bone structures during stereotactically guided gamma knife surgery for vestibular schwannomas

Restricted access

Object. The dosimetry of radiation exposure of healthy inner, middle, and external ear structures that leads to hearing loss, tinnitus, facial weakness, dizziness, vertigo, and imbalance after gamma knife surgery (GKS) for vestibular schwannomas (VSs) is unknown. The authors quantified the dose of radiation received by these structures after GKS for VS to assess the likelihood that these doses contributed to postradiosurgery complications.

Methods. A retrospective study was performed using a prospectively acquired database of a consecutive series of 54 patients with VS who were treated with GKS during a 3.5-year period at an “open unit” gamma knife center. Point doses were measured for 18 healthy temporal bone structures in each patient, with the anatomical position of each sampling point confirmed by a fellowship-trained neurootologist. These values were compared against single-dose equivalents for the 5-year tolerance dose for a 5% risk of complications and the 5-year tolerance dose for a 50% risk of complications, which were calculated using known 2-Gy/fraction thresholds for chronic otitis, chondromalacia, and osseous necrosis, as well as the tumor margin dose and typical tumor margin prescription doses for patients in whom hearing preservation was attempted.

External and middle ear doses were uniformly low. The intratemporal facial nerve is susceptible to unintentionally high radiation exposure at the fundus of the internal auditory canal, with higher than tumor margin doses detected in 26% of cases. In the cochlea, the basal turn near the modiolus and its inferior portion are most susceptible, with doses greater than 12 Gy detected in 10.8 and 14.8% of cases. In the vestibular labyrinth, the ampulated ends of the lateral and posterior semicircular canals are most susceptible, with doses greater than 12 Gy detected in 7.4 and 5.1% of cases.

Conclusions. Doses delivered to middle and external ear structures are unlikely to contribute to post-GKS complications, but unexpectedly high doses may be delivered to sensitive areas of the intratemporal facial nerve and inner ear. Unintentional delivery of high doses to the stria vascularis, the sensory neuroepithelium of the inner ear organs and/or their ganglia, may play a role in the development of post-GKS tinnitus, hearing loss, dizziness, vertigo, and imbalance. Minimizing treatment complications post-GKS for VS requires precise dose planning conformality with the three-dimensional surface of the tumor.

Article Information

Address correspondence to: Peter A. S. Johnstone, M.D., Radiation Oncology Division, Naval Medical Center, San Diego, California 92134–1014. email: pajohnstone@nmcsd.med.navy.mil.

© AANS, except where prohibited by US copyright law.

Headings

Figures

  • View in gallery

    Digital screen image captured from Gamma Plan version 4.0 demonstrating the cursor position for the sampling point dose on an MR treatment planning image for two of the four facial nerve segments, and three of the eight inner ear structures measured (Table 2). All cursor positions were localized by a neurootologist. Different structures were best seen on different axial levels within the temporal bone.

  • View in gallery

    Digital screen image captured from Gamma Plan version 4.0 demonstrating the cursor position for the sampling point dose on an MR treatment planning image for two of the five middle ear, and one of the eight inner ear structures measured (Table 2). All cursor positions were localized by a neurootologist. Different structures were best seen on different axial levels within the temporal bone.

  • View in gallery

    Digital screen image captured from Gamma Plan version 4.0 demonstrating the cursor position for the sampling point dose on an MR treatment planning image for the external auditory canal bone/cartilage junction, and two of the eight inner ear structures measured (Table 2). All cursor positions were localized by a neurootologist. Different structures were best seen on different axial levels within the temporal bone.

  • View in gallery

    Graph depicting the mean conformality index (C.I.; tumor margin prescription [Rx] dose volume/tumor volume) per radiosurgery team on the y axis plotted against the mean number (#) of isocenters per tumor per radiosurgery team on the x axis. There was a positive linear correlation between these two variables (r = 0.62).

References

  • 1.

    Adler MHawke MBerger Get al: Radiation effects on the external auditory canal. J Otolaryngol 14:2262321985Adler M Hawke M Berger G et al: Radiation effects on the external auditory canal. J Otolaryngol 14:226–232 1985

  • 2.

    Berg NOLindgren M: Dose factors and morphology of delayed radiation lesions of the internal and middle ear in rabbits. Acta Radiol 56:3053191961Berg NO Lindgren M: Dose factors and morphology of delayed radiation lesions of the internal and middle ear in rabbits. Acta Radiol 56:305–319 1961

  • 3.

    Bohne BAMarks JEGlasgow GP: Delayed effects of ionizing radiation on the ear. Laryngoscope 95:8188281985Bohne BA Marks JE Glasgow GP: Delayed effects of ionizing radiation on the ear. Laryngoscope 95:818–828 1985

  • 4.

    Borsanyi SJ: The effects of radiation therapy on the ear: with particular reference to radiation otitis media. Southern Med J 55:7407431962Borsanyi SJ: The effects of radiation therapy on the ear: with particular reference to radiation otitis media. Southern Med J 55:740–743 1962

  • 5.

    Borsanyi SJBlanchard CL: Ionizing radiation and the ear. JAMA 181:9589611962Borsanyi SJ Blanchard CL: Ionizing radiation and the ear. JAMA 181:958–961 1962

  • 6.

    Borsanyi SJBlanchard CLThorne B: The effects of ionizing radiation on the ear. Ann Otol Rhinol Laryngol 70:2552621961Borsanyi SJ Blanchard CL Thorne B: The effects of ionizing radiation on the ear. Ann Otol Rhinol Laryngol 70:255–262 1961

  • 7.

    Coplan JPost EMRichman RAet al: Hearing loss after therapy with radiation. Am J Dis Child 135:106610671981Coplan J Post EM Richman RA et al: Hearing loss after therapy with radiation. Am J Dis Child 135:1066–1067 1981

  • 8.

    Dias A: Effects on the hearing of patients treated with irradiation in the head and neck area. J Laryngol Otol 80:2762871966Dias A: Effects on the hearing of patients treated with irradiation in the head and neck area. J Laryngol Otol 80:276–287 1966

  • 9.

    Emami BLyman JBrown Aet al: Tolerance of normal tissue to therapeutic irradiation. Int J Radiat Oncol Biol Phys 21:1091221991Emami B Lyman J Brown A et al: Tolerance of normal tissue to therapeutic irradiation. Int J Radiat Oncol Biol Phys 21:109–122 1991

  • 10.

    Ewald CA: Die wirkung des radium auf das Labyrinth. Zentralbl Physiol 19:2982991905Ewald CA: Die wirkung des radium auf das Labyrinth. Zentralbl Physiol 19:298–299 1905

  • 11.

    Flickinger JCKondziolka DPollock BEet al: Evolution in technique for vestibular schwannoma radiosurgery and effect on outcome. Int J Radiat Oncol Biol Phys 36:2752801996Flickinger JC Kondziolka D Pollock BE et al: Evolution in technique for vestibular schwannoma radiosurgery and effect on outcome. Int J Radiat Oncol Biol Phys 36:275–280 1996

  • 12.

    Fong RSBeste DJMurray KJ: Pediatric sensorineural hearing loss after temporal bone radiation. Am J Otol 16:7937961995Fong RS Beste DJ Murray KJ: Pediatric sensorineural hearing loss after temporal bone radiation. Am J Otol 16:793–796 1995

  • 13.

    Gamble JEPeterson EAChandler JR: Radiation effects on the inner ear. Arch Otolaryngol 88:1561611968Gamble JE Peterson EA Chandler JR: Radiation effects on the inner ear. Arch Otolaryngol 88:156–161 1968

  • 14.

    Grau CMoller MOvergaard Met al: Sensori-neural hearing loss in patients treated with irradiation for nasopharyngeal carcinoma. Int J Radiat Oncol Biol Phys 21:7237281991Grau C Moller M Overgaard M et al: Sensori-neural hearing loss in patients treated with irradiation for nasopharyngeal carcinoma. Int J Radiat Oncol Biol Phys 21:723–728 1991

  • 15.

    Gyorkey JPollock FJ: Radiation necrosis of the ossicles. Arch Otolaryngol 71:7937961960Gyorkey J Pollock FJ: Radiation necrosis of the ossicles. Arch Otolaryngol 71:793–796 1960

  • 16.

    Keleman G: Radiation and ear. Acta Otolaryngol Suppl 184:1481963 (Reference unverified)Keleman G: Radiation and ear. Acta Otolaryngol Suppl 184:1–48 1963 (Reference unverified)

  • 17.

    Kim CSShin SO: Ultrastructural changes in the cochlea of the guinea pig after fast neutron irradiation. Otolaryngol Head Neck Surg 110:4194271994Kim CS Shin SO: Ultrastructural changes in the cochlea of the guinea pig after fast neutron irradiation. Otolaryngol Head Neck Surg 110:419–427 1994

  • 18.

    Kondziolka DLunsford LDMcLaughlin MRet al: Long-term outcomes after radiosurgery for acoustic neuromas. N Engl J Med 339:142614331998Kondziolka D Lunsford LD McLaughlin MR et al: Long-term outcomes after radiosurgery for acoustic neuromas. N Engl J Med 339:1426–1433 1998

  • 19.

    Leach W: Irradiation of the ear. J Laryngol Otol 79:8708801965Leach W: Irradiation of the ear. J Laryngol Otol 79:870–880 1965

  • 20.

    Leksell L: A note on the treatment of acoustic tumors. Acta Chir Scand 137:7637651971Leksell L: A note on the treatment of acoustic tumors. Acta Chir Scand 137:763–765 1971

  • 21.

    Linskey MEFlickinger JCLunsford LD: Cranial nerve length predicts the risk of delayed facial and trigeminal neuropathies after acoustic tumor stereotactic radiosurgery. Int J Radiat Oncol Biol Phys 25:2272331993Linskey 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

  • 22.

    Lunsford LDLinskey ME: Stereotactic radiosurgery in the treatment of patients with acoustic tumors. Otolaryngol Clin North Am 25:4714911992Lunsford LD Linskey ME: Stereotactic radiosurgery in the treatment of patients with acoustic tumors. Otolaryngol Clin North Am 25:471–491 1992

  • 23.

    Magnuson KFranzen LHenriksson Ret al: Structural changes in the middle ear tissues of the rat after fractionated irradiation. Eur Arch Otorhinolaryngol 250:92961993Magnuson K Franzen L Henriksson R et al: Structural changes in the middle ear tissues of the rat after fractionated irradiation. Eur Arch Otorhinolaryngol 250:92–96 1993

  • 24.

    Mencher GTNovotny GMencher Let al: Ototoxicity and irradiation: additional etiologies of hearing loss in adults. J Am Acad Audiol 6:3513571995Mencher GT Novotny G Mencher L et al: Ototoxicity and irradiation: additional etiologies of hearing loss in adults. J Am Acad Audiol 6:351–357 1995

  • 25.

    Moretti JA: Sensori-neural hearing loss following radiotherapy to the nasopharynx. Laryngoscope 86:5986021976Moretti JA: Sensori-neural hearing loss following radiotherapy to the nasopharynx. Laryngoscope 86:598–602 1976

  • 26.

    Moss WT: Therapeutic Radiology Rationale Technique Results. St. Louis: CV Mosby1959 pp 104105Moss WT: Therapeutic Radiology Rationale Technique Results. St. Louis: CV Mosby 1959 pp 104–105

  • 27.

    Nagel DSchafer J: Changes in cochlear microphonic response after γ-ray irradiation of the inner ear of the guinea-pig. Arch Otorhinolaryngol 241:17211984Nagel D Schafer J: Changes in cochlear microphonic response after γ-ray irradiation of the inner ear of the guinea-pig. Arch Otorhinolaryngol 241:17–21 1984

  • 28.

    Nomura RHattori TYanagita N: Radiation tolerance of the cochlear nerve at the gamma knife in rabbits. Auris Nasus Larynx 24:3413491997Nomura R Hattori T Yanagita N: Radiation tolerance of the cochlear nerve at the gamma knife in rabbits. Auris Nasus Larynx 24:341–349 1997

  • 29.

    Noren GGreitz DHirsch Aet al: Gamma knife surgery in acoustic tumors. Acta Neurochir Suppl 58:1041071993Noren G Greitz D Hirsch A et al: Gamma knife surgery in acoustic tumors. Acta Neurochir Suppl 58:104–107 1993

  • 30.

    Prasad DSteiner MSteiner L: Gamma surgery for vestibular schwannoma. J Neurosurg 92:7457592000Prasad D Steiner M Steiner L: Gamma surgery for vestibular schwannoma. J Neurosurg 92:745–759 2000

  • 31.

    Schuknecht HFKarmody CS: Radionecrosis of the temporal bone. Laryngoscope 76:141614281966Schuknecht HF Karmody CS: Radionecrosis of the temporal bone. Laryngoscope 76:1416–1428 1966

  • 32.

    Smouha EEKarmody CS: Non-osteitic complications of therapeutic radiation to the temporal bone. Am J Otol 16:83871995Smouha EE Karmody CS: Non-osteitic complications of therapeutic radiation to the temporal bone. Am J Otol 16:83–87 1995

  • 33.

    Talmi YPFinkelstein YZohar Y: Postirradiation hearing loss. Audiology 28:1211261989Talmi YP Finkelstein Y Zohar Y: Postirradiation hearing loss. Audiology 28:121–126 1989

  • 34.

    Thibadoux GMPereira WVHodges JMet al: Effects of cranial radiation on hearing in children with acute lymphocytic leukemia. J Pediatrics 96:4034061980Thibadoux GM Pereira WV Hodges JM et al: Effects of cranial radiation on hearing in children with acute lymphocytic leukemia. J Pediatrics 96:403–406 1980

  • 35.

    Winther FO: Early degenerative changes in the inner ear sensory cells of the guinea pig following local x-ray irradiation. A preliminary report. Acta Otolaryngol 67:2622681969Winther FO: Early degenerative changes in the inner ear sensory cells of the guinea pig following local x-ray irradiation. A preliminary report. Acta Otolaryngol 67:262–268 1969

  • 36.

    Winther FO: X-ray irradiation of the inner ear of the guinea pig. An electron microscopic study of the degenerating outer hair cells of the organ of Corti. Acta Otolaryngol 69:61761970Winther FO: X-ray irradiation of the inner ear of the guinea pig. An electron microscopic study of the degenerating outer hair cells of the organ of Corti. Acta Otolaryngol 69:61–76 1970

  • 37.

    Winther FO: X-ray irradiation of the inner ear of the guinea pig. Early degenerative changes in the cochlea. Acta Otolaryngol 68:981171969Winther FO: X-ray irradiation of the inner ear of the guinea pig. Early degenerative changes in the cochlea. Acta Otolaryngol 68:98–117 1969

TrendMD

Cited By

Metrics

Metrics

All Time Past Year Past 30 Days
Abstract Views 69 69 5
Full Text Views 130 130 0
PDF Downloads 52 52 1
EPUB Downloads 0 0 0

PubMed

Google Scholar