Anatomical study of endoscope-assisted far lateral keyhole approach to the ventral craniocervical region with neuronavigational guidance / 中华医学杂志(英文版)

<p><b>BACKGROUND</b>Image-guided neurosurgery, endoscopic-assisted neurosurgery and the keyhole approach are three important parts of minimally invasive neurosurgery and have played a significant role in treating skull base lesions. This study aimed to investigate the potential usefulness of coupling of the endoscope with the far lateral keyhole approach and image guidance at the ventral craniocervical junction in a cadaver model.</p><p><b>METHODS</b>We simulated far lateral keyhole approach bilaterally in five cadaveric head specimens (10 cranial hemispheres). Computed tomography-based image guidance was used for intraoperative navigation and for quantitative measurements. Skull base structures were observed using both an operating microscope and a rigid endoscope. The jugular tubercle and one-third of the occipital condyle were then drilled, and all specimens were observed under the microscope again. We measured and compared the exposure of the petroclivus area provided by the endoscope and by the operating microscope. Statistical analysis was performed by analysis of variance followed by the Student-Newman-Keuls test.</p><p><b>RESULTS</b>With endoscope assistance and image guidance, it was possible to observe the deep ventral craniocervical junction structures through three nerve gaps (among facial-acoustical nerves and the lower cranial nerves) and structures normally obstructed by the jugular tubercle and occipital condyle in the far lateral keyhole approach. The surgical area exposed in the petroclival region was significantly improved using the 0° endoscope (1147.80 mm(2)) compared with the operating microscope ((756.28 ± 50.73) mm(2)). The far lateral retrocondylar keyhole approach, using both 0° and 30° endoscopes, provided an exposure area ((1147.80 ± 159.57) mm(2) and (1409.94 ± 155.18) mm(2), respectively) greater than that of the far lateral transcondylar transtubercular keyhole approach ((1066.26 ± 165.06) mm(2)) (P < 0.05).</p><p><b>CONCLUSIONS</b>With the aid of the endoscope and image guidance, it is possible to approach the ventral craniocervical junction with the far lateral keyhole approach. The use of an angled-lens endoscope can significantly improve the exposure of the petroclival region without drilling the jugular tubercle and occipital condyle.</p>

Removal of vestibular schwannoma and facial nerve preservation using small suboccipital retrosigmoid craniotomy / 中华医学杂志(英文版)

<p><b>BACKGROUND</b>Vestibular schwannoma, the commonest form of intracranial schwannoma, arises from the Schwann cells investing the vestibular nerve. At present, the surgery for vestibular schwannoma remains one of the most complicated operations demanding for surgical skills in neurosurgery. And the trend of minimal invasion should also be the major influence on the management of patients with vestibular schwannomas. We summarized the microsurgical removal experience in a recent series of vestibular schwannomas and presented the operative technique and cranial nerve preservation in order to improve the rates of total tumor removal and facial nerve preservation.</p><p><b>METHODS</b>A retrospective analysis was performed in 145 patients over a 7-year period who suffered from vestibular schwannomas that had been microsurgically removed by suboccipital retrosigmoid transmeatus approach with small craniotomy. CT thinner scans revealed the tumor size in the internal auditory meatus and the relationship of the posterior wall of the internal acoustic meatus to the bone labyrinths preoperatively. Brain stem evoked potential was monitored intraoperatively. The posterior wall of the internal acoustic meatus was designedly drilled off. Patient records and operative reports, including data from the electrophysiological monitoring, follow-up audiometric examinations, and neuroradiological findings were analyzed.</p><p><b>RESULTS</b>Total tumor resection was achieved in 140 cases (96.6%) and subtotal resection in 5 cases. The anatomical integrity of the facial nerve was preserved in 91.0% (132/145) of the cases. Intracranial end-to-end anastomosis of the facial nerve was performed in 7 cases. Functional preservation of the facial nerve was achieved in 115 patients (Grade I and Grade II, 79.3%). No patient died in this series. Preservation of nerves and vessels were as important as tumor removal during the operation. CT thinner scan could show the relationship between the posterior wall of the internal acoustic meatus and bone labyrinths, that is helpful for a safe drilling of the posterior wall of the internal acoustic meatus.</p><p><b>CONCLUSIONS</b>The goal of every surgery should be the preservation of function of all cranial nerves. Using the retrosigmoid approach with small craniotomy is possible even for large schwannomas. Knowing the microanatomy of the cerebellopontine angle and internal auditory meatus, intraoperating neurophysiological monitoring of the facial nerve function, and the microsurgical techniques of the surgeons are all important factors for improving total tumor removal and preserving facial nerve function.</p>