Schwannoma

​​​​Revised: June 2014

In both intracranial and spinal locations these tumours have a propensity for the sensory roots. The most common intracranial schwannoma is the acoustic neuroma followed by trigeminal neuroma. In the spinal region the lumbar followed by thoracic and cervical regions are most frequently involved. The usual goal of treatment for these tumours is complete surgical excision. Malignant degeneration does occur, most frequently arising de novo from a peripheral nerve.

Stereotactic radiation therapy (SRT) may be useful in patients with acoustic neuroma who decline surgery or who are medically inoperable, or in those with bilateral tumours or tumours in the only hearing ear, since surgery may be associated with a relatively high risk of loss of functional hearing. Single fraction SRT has been shown to lead to high rates of control, defined by tumour stabilization or shrinkage, with good prospects for hearing preservation (1-3). There is no evidence that Gamma Knife SRT is in any way superior to linear-accelerator based SRT. Studies have suggested that fractionated SRT may lead to even better hearing preservation in patients who have functional hearing to start with (4,5).  One long term single institution series comparing fractionated stereotactic radiotherapy versus single fraction stereotactic radiosurgery showed similar 5 and 10 year survival rates of 96% in both groups (6).  Single fraction doses over 13 Gy were associated with higher rates of hearing loss compares to fractionated treatment or lower dose single fractions. 

References

  1. Flickinger, J.C., Lunsford, L.D., Linskey, M.E., Duma, C.M. & Kondziolka, D. (1993). Gamma knife radiosurgery for acoustic tumors: Multivariate analysis of four year results. Radiotherapy and Oncology 27(2):91-98.    

  2. Noren, G., Greitz, D., Hirsch, A. & Lax, I. (1993). Gamma knife surgery in acoustic tumours. Acta Neurochirurgica - supplement 58:104-107.

  3. Mendenhall, W.M., Friedman, W.A., Buatti, J.M. & Bova, F.J. (1996). Preliminary results of linear accelerator radiosurgery for acoustic schwannomas. Journal of Neurosurgery 85(6):1013-1019.

  4. Varlotto, J.M., Shrieve, D.C., Alexander, E. et al.  (1996). Fractionated stereotactic radiotherapy for the treatment of acoustic neuromas: Preliminary results. International Journal of Radiation Oncology - Biology - Physics 36(1):141-145.    

  5. Andrews, D.W., Silverman, C.L., Glass, J. et al. (1995). Preservation of cranial nerve function after treatment of acoustic neurinomas with fractionated stereotactic radiotherapy: Preliminary observations in 26 patients. Stereotactic and Functional Neurosurgery 64(4):165-82.

  6. Combs, S.E., Welzel, T., Shulz-Ertner, D. et al. (2010). Differences in clinical results after LINAC-based single dose radiosurgery versus fractionated stereotactic radiotherapy for patients with vestibular schwannomas. International Journal of Radiation Oncology - Biology - Physics​ 76:193.