Evaluation of the Results of Endoscope-Assisted Acoustic Neuroma Surgery through Posterior Fossa Approach

Abstract

The objective of this study was to evaluate the results of endoscope-assisted acoustic neuroma surgery in posterior fossa approach. Between 1996 and 2002, 60 consecutive patients with acoustic neuroma were operated via the retrosigmoid suboccipital approach. Standard 4-mm sinus endoscopes at different angles were used during the surgeries either for inspection or tumor endoscopic dissection. Clinical parameters and treatment outcome were evaluated retrospectively. Tumor sizes were small, medium and large in 46.6, 45 and 8.3% of the patients, respectively. The hearing preservation rate, which did not correlate with tumor size (p > 0.05), was 24.4%. The need for facial reanimation surgery, which was needed in 5% of patients, was significantly higher in the large tumors than in the small and medium tumors (p < 0.001). Cerebrospinal fluid fistula rate, which was not related to tumor size (p > 0.05), was 13.3%. Tumor recurrence or residual tumor was not encountered at all. In conclusion, endoscopes give accurate information about the relationship between the tumor and the adjacent structures and help control the fundus of the internal auditory canal to ensure complete tumor removal. It is also helpful in visually verifying the continuity of the facial and cochlear nerves. The use of endoscopes does not appear to increase the hearing preservation rate, but is very helpful in complete tumor removal in the posterior fossa approach.

An electrophysiological study on the safety of the endoscope-assisted microsurgical removal of vestibular schwannomas

“…In such cases the endoscopic inspection allows for assessment of the completeness of tumour removal, especially the existence of tumour remnants in the most lateral part of the IAC [22]. The remnant could be removed under endoscopic or microscopic control [3,5,9]. Although in our series we did not find such remnants, some authors report a rate of up to 17.6% [3,8].…”

“…Its application in case of lesions located in cerebellopontine angle (CPA), offers the possibility to identify at an early stage various structures and their relations, as well as to look for hidden tumour parts [3]. In case of vestibular schwannomas (VS) the whole internal auditory canal (IAC) up to its fundus can be inspected without increasing the risk of violation to the bony labyrinth; thus tumour remnants or opened air cells are readily visualized [4][5][6][7][8].…”

“…The issue of potential thermal injury caused by the heat generated by the light source of endoscopes has been mentioned by several authors [3,5,10]. This effect in laboratory settings has been studies by Hori et al, who performed a thermographic study [11].…”

Minimally Invasive Endoscopic and Endoscopy-Assisted Microsurgery of Vestibular Schwannoma

“…Inability to completely visualize the lateral extent of the tumor as well as incomplete visualization of the exposed air cells are among the main disadvantages of the retrosigmoid approach. Excessive drilling of the petrous bone that is necessary in tumors extending to the lateral parts and fundus of internal auditory canal needed to achieve safe and radical tumor removal, might hamper the chance for hearing preservation as a consequence of injury of the posterior semicircular canal or labyrinth (Koval et al 1993, Low 1999b, Goksu et al 2005. Simultaneously, extensive drilling of the posterior meatal wall with improper sealing of the opened pneumatic system is associated with increased risk of cerebrospinal fluid leak (Valtonen et al 1997).…”

“…Cerebellum can be protected during the procedure by covering it with a neurosurgical cotton, piece of Penrose drain or artificial dura. However working with 30° endoscopes has been repeatedly shown to be safe , Goksu et al 2005, Miyazaki et al 2005. Risk of injury with insertion of 45° and 70° endoscopes is probably higher, but this can best alleviated by microscopic control.…”