Trigeminal Neuralgia: Current Trends in Surgical Research

1. Trigeminal Neuralgia: Current Trends in Surgical Research Reza Jarrahy, M.D. Division of Skull Base Surgery Cedars-Sinai Medical Center Trigeminal Neuralgia Workshop February 26, 2000 Cedars-Sinai Medical Center Los Angeles, CA

2. Research Efforts in TN • pharmacological research • neurophysiological research • clinical research

3. Clinical Research in TN • two year effort at Cedars-Sinai Medical Center • goals: develop techniques that improve surgical outcomes in patients undergoing microvascular decompression for TN

4. Clinical Research in TN • prerequisites to introducing new surgical techniques: the innovative procedure must... • … have a sound theoretical basis • … be reproducible in a controlled setting (animal laboratory) • … represent an improvement over the traditional therapy

5. Clinical Research in TN • prerequisites to introducing new surgical techniques: the innovative procedure must... • … have a sound theoretical basis • … be reproducible in a controlled setting (animal laboratory) • … represent an improvement over the traditional therapy

6. Clinical Research in TN • theory: • in patients whose neuralgia is caused by vascular compression of the root of the trigeminal nerve, there is an anatomical basis for the disease and the surgical therapy • in these patients, surgical success is directlyrelated to accurate visualization of the involved anatomical structures

7. Clinical Research in TN • theory: • visualization of the posterior fossa with the operating microscope (the traditional surgical approach) is restricted due to the limited capabilities of the instrument...

8. Clinical Research in TN • theory: • better images of the posterior fossa during surgery leads to more comprehensive identification of all nerve-vessel conflicts, and therefore more complete repair

9. Clinical Research in TN • theory: • endoscopes (long, thin telescopes) are ideally suited to imaging the trigeminal nerve and surrounding blood vessels during surgery for TN • varying widths, angles of view • full range of accessories (cameras, light sources, recorders, processors, irrigation sheaths, holding arms)

10. Clinical Research in TN • hypothesis: • better endoscopic images lead to improved surgical outcomes...

11. Clinical Research in TN • prerequisites to introducing new surgical techniques: the innovative procedure must... • … have a sound theoretical basis • … be reproducible in a controlled setting (animal laboratory) • … represent an improvement over the traditional therapy

12. Clinical Research in TN • animal experimentation: • allows 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

13. Clinical Research in TN • experimental model • porcine and human skull base anatomy are very similar • anatomical relationships are also analogous

14. Clinical Research in TN • experimental model • method • 30 kg Hampshire-Yorkshire-Duroc swine • general anesthesia • left lateral decubitus position • 2 cm retrosigmoid craniotomy • incision of dura • endoscopic exploration of posterior fossa • identification of cranial nerves

15. Clinical Research in TN • experimental model • results • visualization of cerebellum, lower cranial nerves (CN IX-XI), acousticofacial bundle (CN VII-VIII), and trigeminal nerve (CN V)

16. Clinical Research in TN • experimental model • results • panoramic views with addition of angled endoscopes • impediments to visualization (e.g., petrous apex) circumnavigated

17. Clinical Research in TN • experimental model • results • impediments to visualization (e.g., petrous apex) circumnavigated

18. Clinical Research in TN • experimental model • 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.

19. Clinical Research in TN • prerequisites to introducing new surgical techniques: the innovative procedure must... • … have a sound theoretical basis • … be reproducible in a controlled setting (animal laboratory) • … represent an improvement over the traditional therapy

20. Clinical Research in TN • clinical improvement attributable to a new technique should be objectively demonstrated prior to its widespread acceptance • posterior fossa endoscopy offers unique opportunity in this regard: • it can be used in conjunction with the microscope to directly compare their qualities

21. Clinical Research in TN • endoscope-assisted mvd • Magnan et al: • combined endoscopic and microscopic techniques in MVD for hemifacial spasm in 60 patients • findings: “When the operating microscope was used alone, the exact location of the offending vessel was obvious in only 16 patients (28%). The endoscopic procedure gave an additional 72% accuracy rate for the diagnosis of vessel-nerve conflict…” Magnan J et al, Hemifacial spasm: endoscopic vascular decompression. Otolaryngol Head Neck Surg 1997;117(4):308-314.

22. Clinical Research in TN • endoscope-assisted mvd • Magnan et al: • “Over the past two years, [we] have combined microsurgery and endoscopy to increase safety and effectiveness in the… retrosigmoid approach… In the future, an endoscopic microvascular decompression seems to be a possible approach.” Magnan J et al, Surgical perspectives of endoscopy of the cerebellopontine angle. Am J Otol 1994;15(3):366-370.

23. Clinical Research in TN • endoscope-assisted mvd • Division of Skull Base Surgery • objectives: to determine the efficacy of endoscopy as an imaging modality in posterior fossa vascular decompression relative to microscopy • design: case series (n = 20) with review of medical records and intraoperative video

24. Clinical Research in TN • endoscope-assisted mvd • Division of Skull Base Surgery • interventions: • microvascular decompression via retrosigmoid craniotomy • endoscopes used to conduct surveys of nerve-vessel conflicts prior to microscopic intervention • endoscopes also used to conduct final surveys of posterior fossa to evaluate adequacy of microscopic intervention

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29. Clinical Research in TN • endoscope-assisted mvd • Division of Skull Base Surgery • results: • endoscopes were able to identify nerve-vessel conflicts that were not detected under microscopic examination • endoscopic images were particularly useful when the nerve vessel conflicts were close to the opening of Meckel’s cave, highlighting the flexibility of the endoscope

30. Clinical Research in TN • endoscope-assisted mvd • Division of Skull Base Surgery • results: • In 24% of patients, endoscopic survey following microscopic placement of insulating Teflon pads revealed areas of the nerves that were not adequately decompressed

31. Clinical Research in TN • endoscope-assisted mvd • Division of Skull Base Surgery • conclusions: • “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.” Jarrahy R, Berci G, Shahinian HK. Endoscope-assisted microvascular decompression of the trigeminal nerve. Accepted for publication in Otolaryngol Head Neck Surg

32. Clinical Research in TN • prerequisites to introducing new surgical techniques: the innovative procedure must... • … have a sound theoretical basis • … be reproducible in a controlled setting (animal laboratory) • … represent an improvement over the traditional therapy

33. Clinical Research in TN • fully endoscopic cranial nerve vascular decompression surgery...

34. Clinical Research in TN • fully endoscopic cranial nerve vascular decompression surgery… • “The strength of the endoscope in this setting is its ability to impart to the surgeon more comprehensive anatomical images than those that are obtainable under the static anteroposterior viewing capabilities of the microscope… Improved visualization has direct implications for surgical outcome.” • Jarrahy R, Mathiasen RA, Cha ST, Berci G, Shahinian HK. Fully endoscopic vascular • decompression of the trigeminal nerve. Accepted for publication in Arch Otolaryngol • Head Neck Surg