Developing a Method to Precisely Locate the Keypoint During Craniotomy Using the Retrosigmoid Keyhole Approach: Surgical Anatomy and Technical Nuances

Optimizing surgical technique in microvascular decompression for hemifacial spasm - Results from a surgical series with contemporary use of neuronavigation and intraoperative neuromonitoring

Background

Microvascular decompression (MVD) through a retrosigmoid approach is considered the treatment of choice in cases of hemifacial spasm (HFS) due to neurovascular conflict (NVC). Despite the widespread of neuronavigation and intraoperative neuromonitoring (IONM) techniques in neurosurgery, their contemporary application in MVD for HFS has been only anecdotally reported.

Methods

Here, we report the results of MVD performed with a combination of neuronavigation and IONM, including lateral spread response (LSR) in 20 HFS patients. HFS clinical outcome and different surgical-related factors, such as craniotomy size, surgical duration, mastoid air cell (MAC) opening, postoperative cerebral spinal fluid (CSF) leakage, sinus injury, and other complications occurrence, and the length of hospitalization (LOS) were studied.

Results

Postoperatively, residual spasm persisted only in two patients, but at the latest follow-up (FU) (mean: 12.5 ± 8.98 months), all patients had resolution of symptoms. The mean surgical duration was 103.35 ± 19.36 min, and the mean LOS was 2.21 ± 1.12 days. Craniotomy resulted in 4.21 ± 1.21 cm2 in size. Opening of MAC happened in two cases, whereas no cases of CSF leak were reported as well as no other complications postoperatively and during FU.

Conclusion

MVD for HFS is an elective procedure, and for this reason, surgery should integrate all technologies to ensure safety and efficacy. The disappearance of LSR is a crucial factor for identifying the vessel responsible for NVC and for achieving long-term resolution of HFS symptoms. Simultaneously, the benefits of using neuronavigation, including the ability to customize the craniotomy, contribute to reduce the possibility of complications.

Application of Preoperative Multimodal Image Fusion Technique in Microvascular Decompression Surgery via Suboccipital Retrosigmoid Approach

OBJECTIVE

To explore the application value of preoperative multimodal image fusion technique in microvascular decompression (MVD) surgery via the suboccipital retrosigmoid approach.

METHODS

Comprehensive data of 13 patients with primary trigeminal neuralgia (TN) and 13 patients with hemifacial spasm (HFS) treated by MVD surgery via the suboccipital retrosigmoid approach at the Department of Neurosurgery in Zhuhai People's Hospital from January 2021 to December 2021 were retrospectively analyzed. Preoperatively, all patients underwent cranial thin-section computed tomography and magnetic resonance examinations. Three-dimensional (3D) digital images of the skull, brainstem, nerves, and blood vessels were constructed by the 3D-slicer software or RadiAnt DICOM Viewer, which were then applied to design the surgical approach and surgical plan. The multimodal image fusion results, clinical characteristics, intraoperative data, surgical outcomes, and complications of all patients were summarized.

RESULTS

The 3D digital images after fusion reconstruction can vividly show the anatomical relationship between the skull, brainstem, nerves, and blood vessels and was helpful to tailor the surgical strategy. All 26 patients underwent a smooth surgery. During the surgery, the key points were accurately located, the corners of the transverse sinus and sigmoid sinus were completely exposed, and no venous sinus injury occurred in all 26 patients. The key point was approximately located at the top point of the digastric groove, 12.3 ± 0.46 mm vertically above and 6.3 ± 0.6 mm laterally to the Frankfurt horizontal plane. The average cranial opening time was 30.4 (±3.6) min, and the mean operating time was 104.7 (±12.1) min. The diameter of the bone window was about 2.0 cm-3.0 cm, and the bone flap was restored. Among the 13 patients with primary TN, 12 (92.3%) exhibited complete relief of pain and 1 had significant relief. Complications of surgery included facial sensory numbness in 1 case, vertigo in 2 cases, and herpes at the corners of the mouth in 1 case. Of the 13 patients with HFS, 12 (92.3%) had complete relief of facial twitching symptoms and 1 had significant relief, and the complications included mild facial palsy in 2 (15.4%) cases and facial sensory numbness in another 2 (15.4%) cases. The mean follow-up time after surgery ranged from 6-16 months, and 1 of 26 patients experienced recurrence of HFS during the follow-up period.

CONCLUSIONS

Preoperative multimodal image fusion technology can provide adequate preoperative assessment for patients and assistance in designing surgical approaches, which is an important guideline for MVD surgery via the suboccipital retrosigmoid approach for primary TN and facial muscle spasm.

Surgical Effects of Resecting Skull Base Tumors Using Pre-operative Multimodal Image Fusion Technology: A Retrospective Study

Objectives

To analyze the surgical effects of resecting skull base tumors using multimodal three-dimensional (3D) image fusion technology in the neurosurgery department and present some typical cases.

Methods

From October 2019 to October 2021, we included 47 consecutive patients with skull base tumors in the Neurosurgery Department at Zhuhai People's Hospital in this study. Pre-operative head computed tomography and magnetic resonance imaging data acquisition was performed using the GE AW workstation software for registration fusion, image fusion, and 3D reconstruction. The surgical approach and surgical plan were designed based on the multimodal 3D image, and the resection rate, complication rate, and operative time of the surgery using the multimodal image fusion technique were analyzed.

Results

The reconstructed multimodal 3D images precisely demonstrated the size, location, and shape of the tumor along with the anatomical relationship between the tumor and surrounding structures, which is consistent with the intraoperative findings. Among 47 patients, 39 patients (78.7%) underwent total resection, 5 (14.9%) underwent subtotal resection, and 3 (6.4%) underwent partial resection. The mean operative time was 4.42 ± 1.32 h. No patient died during the inpatient period. Post-operative complications included 6 cases of cerebrospinal fluid leakage (14.9%), 3 cases of intracranial infection (6.4%), 6 cases of facial paralysis (12.8%), 2 cases of dysphagia (4.3%), and 1 case of diplopia (2.1%), all of which were improved after symptomatic treatment. The application value of pre-operative 3D image fusion technology was evaluated as outstanding in 40 cases (85.1%) and valuable in 7 cases (14.9%).

Conclusions

Pre-operative multimodal image fusion technology can provide valuable visual information in skull base tumor surgery and help neurosurgeons design the surgical incision, choose a more rational surgical approach, and precisely resect the tumor. The multimodal image fusion technique should be strongly recommended for skull base tumor surgery.

Precise Localization in Craniotomy With a Retrosigmoid Keyhole Approach: Microsurgical Anatomy and Clinical Study

Objective

We aimed to explore a method of precise localization within craniotomy based on skull anatomical landmarks via the suboccipital retrosigmoid approach.

Method

Craniometric measurements were taken from 15 adult dry skulls and eight cadaver head specimens. In the anatomical study, the keypoint corresponded to the transverse-sigmoid sinus junction's corresponding point on the external surface of the temporal mastoid process, eight cadaveric heads underwent a simulated craniotomy using the suboccipital retrosigmoid approach. The center of the burr hole is precisely oriented 12 mm vertically above the top point of the mastoid groove based on the line between the infraorbital margin and the upper edge of the external auditory canal. Clinical application was verified in clinical surgery by evaluating the accuracy, safety, rapidity, and minimal invasiveness of the procedure in 29 patients.

Result

No venous sinus injuries were observed. Within clinical application, 29 patients underwent craniotomy using the suboccipital retrosigmoid approach. The operative area was clearly exposed in all patients and the microsurgical anatomy of the intracranial region after the dura mater incision was satisfactory. No venous sinus ruptures were observed. The average craniectomy time was 27.02 ± 0.86 min. The diameter of the bone window was 1.7–2.9 cm.

Conclusion

We conclude that the method can ensure safe, accurate, and rapid craniotomy with good vision while avoiding injury to the venous sinus.