Minimally Invasive Skull Base Surgery: Fact or Fantasy?

1. Minimally Invasive Skull Base Surgery: Fact or Fantasy? Hrayr K. Shahinian M.D,FACS SKULL BASE INSTITUTE

2. A Need for Improvement... • Limitations of posterior fossa microscopy • visualization limited to direct anterior-posterior axis • shallow depth of field • “static” imaging

3. A Need for Improvement... • Limitations of posterior fossa microscopy • clinical implications for MVD • missed conflicts • inadequate decompressions; recurrence • clinical implications for pituitary surgery • residual tumor in lateral recesses of sella turcica

4. Technological Advancement • Rigid endoscopes • varying widths • varying angles of view • Cameras • single-chip • three-chip • digital • three-dimensional

5. Technological Advancement • Light sources • halogen • metal halide • xenon arc • Recorders/processors • digital • Irrigation sheaths • Holding arms

6. Animal Experimental Models • Allow for preliminary evaluation of the effectiveness of the new procedure • Can be reliably reproduced to increase familiarity with new instruments in a safe and controlled setting • Provides a means for surgical training before application in the operating room

7. Animal Experimental Models • Choice of porcine model: posterior fossa • bony anatomy and anatomical relationships of the posterior porcine skull base are analogous to human basicranium

8. Animal Experimental Models • Endoscopic cranial nerve vascular decompression: • aim • develop animal model for endoscopic surgery of the posterior fossa

9. Animal Experimental Models • Endoscopic cranial nerve vascular decompression: • relevance • improved surgical therapy for cranial nerve compression syndromes • trigeminal neuralgia (CN V) • hemifacial spasm (CN VII) • intractable vertigo (CN VIII) • glossopharyngeal neuralgia (CN IX) • spasmodic torticollis (CN XI)

10. Animal Experimental Models • Endoscopic cranial nerve vascular decompression: • method • 30 kg Hampshire-Yorkshire-Duroc swine • general anesthesia • left lateral decubitus position • 2 cm retrosigmoid craniotomy • endoscopic exploration of posterior fossa • identification of cranial nerves

11. Animal Experimental Models • Endoscopic cranial nerve vascular decompression: • results • visualization of cerebellum, lower cranial nerves (CN IX-XI), acousticofacial bundle (CN VII-VIII), and trigeminal nerve (CN V) • panoramic views with addition of angled endoscopes • impediments to visualization (e.g., petrous apex) circumnavigated

12. Animal Experimental Models • Endoscopic cranial nerve vascular decompression: • conclusion • “The dynamic optical qualities of the endoscope should allow for more careful navigation through the very constrained cavities of the skull base, for more detailed appreciation of critical surgical anatomy, and for more thorough surgical intervention with fewer complications due to better visualization.” Jarrahy R, Young J, Berci G, Shahinian HK. Endoscopic skull base surgery II: a new animal model for surgery of the posterior fossa. J Invest Surg 1999;13:1-6.

13. Clinical Trials: Endoscopic Posterior Fossa Surgery • Aim • determine the efficacy of endoscopy as an imaging modality in posterior fossa microvascular decompression

14. Clinical Trials: Endoscopic Posterior Fossa Surgery • Design • case series (n = 210) with retrospective review of medical records and operative video

15. Clinical Trials: Endoscopic Posterior Fossa Surgery • Intervention • microvascular decompression via retrosigmoid craniotomy (traditional approach) • preliminary endoscopic survey of nerve-vessel conflicts prior to microscopic intervention • final endoscopic survey to assess adequacy of microscopic therapy

16. Clinical Trials: Endoscopic Posterior Fossa Surgery • Results • 251 total nerve vessel conflicts • 27% not detected by microscopy--endoscope needed to diagnose and treat these conflicts

17. Clinical Trials: Endoscopic Posterior Fossa Surgery • Results • in 24% of patients, final endoscopic survey revealed incomplete decompression following microscopic therapy

18. Clinical Trials: Endoscopic Posterior Fossa Surgery • Conclusion • “In this series microscopic exploration of the surgical field failed to detect roughly one-quarter of the offending vessels. Likewise…, in one-quarter of cases what was deemed to be an adequate decompression of the trigeminal nerve under the microscope proved to be incomplete. These observations emphasize the value of controlled application of endoscopic techniques at the cerebellopontine angle and merit further attention.” Jarrahy R, Berci G, Shahinian HK. Endoscope-assisted microvascular decompression of the trigeminal nerve. Otolaryngol Head Neck Surg. Accepted for publication.

19. Animal Experimental Models • Choice of porcine model: anterior fossa • bony anatomy and anatomical relationships of the anterior porcine skull base are analogous to human basicranium

20. Animal Experimental Models • Endoscopic pituitary surgery: • aim • develop animal model for pituitary surgery/endoscopic surgery of the anterior fossa • eliminate invasive techniques associated with traditional approach • nasal/septal complications • upper labial hypoesthesia • postoperative nasal packing

21. Animal Experimental Models • Endoscopic pituitary surgery: • relevance • improved surgical therapy resection of pituitary tumors, tumors of the anterior fossa • chordoma • meningioma • craniopharyngioma • teratoma • other tumors

22. Animal Experimental Models • Endoscopic pituitary surgery: • method • 30 kg Hampshire-Yorkshire-Duroc swine • general anesthesia • supine position • gross dissection of hard palate • endoscopic exploration of sella turcica, parasellar and suprasellar areas

23. Animal Experimental Models • Endoscopic pituitary surgery: • results • clear visualization of pituitary gland, hypophyseal stalk, cavernous sinuses, optic nerves • angled endoscopes enabled visualization of lateral recesses (cavernous sinuses) and suprasellar areas

24. Animal Experimental Models • Endoscopic pituitary surgery: • conclusion • “Our results highlight the usefulness of endoscopy in providing superior exposure of the structures that are critical to hypophysectomy.” Jarrahy R, Young J, Berci G, Shahinian HK. Endoscopic skull base surgery I: a new animal model for surgery of the posterior fossa. J Invest Surg 1999;12:1-5.

25. Clinical Trials:Endoscopic Pituitary Surgery • Aim • objectively demonstrate that the use of endoscopy in pituitary surgery improves visualization and surgical outcome

26. Clinical Trials:Endoscopic Pituitary Surgery • Design • case series (n = 229) with retrospective review of medical records and operative videotape

27. Clinical Trials:Endoscopic Pituitary Surgery • Intervention • transseptal transsphenoidal approach to the sella turcica (traditional microscopic technique) • final endoscopic survey of sella and parasellar areas following completion of microscopic resection • residual tumor fragments--precursors to recurrence and persistent endocrinological symptoms--noted and resected

28. Clinical Trials:Endoscopic Pituitary Surgery • Results • residual tumor noted in 33% of patients (43% of macroadenomas) following what was thought to be complete resection via the microscope • angled endoscopes were able to expose lateral recesses of sella turcica where these fragments were missed

29. Clinical Trials:Endoscopic Pituitary Surgery • Conclusion • “…these observations do provide evidence that endoscopic imaging of the intrasellar, parasellar, and suprasellar spaces is more comprehensive than that provided by the operative microscope… [T]he potential impact upon the efficacy of tumor resection and subsequent rates of tumor recurrence is significant when endoscopy is implemented as an imaging modality in the surgical management of pituitary tumors. • Jarrahy R, Berci G, Shahinian HK. Assessment of the efficacy of endoscopy in the resection • of pituitary adenomas. Accepted for publication in Arch Otolaryngol Head Neck Surg.