A system of anatomical triangles defining dissection routes to brainstem cavernous malformations

J Neurosurg 138:768–784, 2023

Anatomical triangles defined by intersecting neurovascular structures delineate surgical routes to pathological targets and guide neurosurgeons during dissection steps. Collections or systems of anatomical triangles have been integrated into skull base surgery to help surgeons navigate complex regions such as the cavernous sinus. The authors present a system of triangles specifically intended for resection of brainstem cavernous malformations (BSCMs). This system of triangles is complementary to the authors’ BSCM taxonomy that defines dissection routes to these lesions.

METHODS The anatomical triangle through which a BSCM was resected microsurgically was determined for the patients treated during a 23-year period who had both brain MRI and intraoperative photographs or videos available for review.

RESULTS Of 183 patients who met the inclusion criteria, 50 had midbrain lesions (27%), 102 had pontine lesions (56%), and 31 had medullary lesions (17%). The craniotomies used to resect these BSCMs included the extended retrosigmoid (66 [36.1%]), midline suboccipital (46 [25.1%]), far lateral (30 [16.4%]), pterional/orbitozygomatic (17 [9.3%]), torcular (8 [4.4%]), and lateral suboccipital (8 [4.4%]) approaches. The anatomical triangles through which the BSCMs were most frequently resected were the interlobular (37 [20.2%]), vallecular (32 [17.5%]), vagoaccessory (30 [16.4%]), supracerebellar-infratrochlear (16 [8.7%]), subtonsillar (14 [7.7%]), oculomotor-tentorial (11 [6.0%]), infragalenic (8 [4.4%]), and supracerebellar-supratrochlear (8 [4.4%]) triangles. New but infrequently used triangles included the vertebrobasilar junctional (1 [0.5%]), supratrigeminal (3 [1.6%]), and infratrigeminal (5 [2.7%]) triangles. Overall, 15 BSCM subtypes were exposed through 6 craniotomies, and the approach was redirected to the BSCM by one of the 14 triangles paired with the BSCM subtype.

CONCLUSIONS A system of BSCM triangles, including 9 newly defined triangles, was introduced to guide dissection to these lesions. The use of an anatomical triangle better defines the pathway taken through the craniotomy to the lesion and refines the conceptualization of surgical approaches. The triangle concept and the BSCM triangle system increase the precision of dissection through subarachnoid corridors, enhance microsurgical execution, and potentially improve patient outcomes.

Contralateral subfrontal approach for tuberculum sellae meningioma

J Neurosurg 138:598–609, 2023

Tuberculum sellae meningiomas (TSMs) present a burdensome surgical challenge because of their adjacency to vital neurovascular structures. The contralateral subfrontal approach provides an outstanding corridor for removing a TSM with an excellent visual outcome and limited complications. The authors present their long-term surgical experience in treating TSMs via the contralateral subfrontal approach and discuss patient selection, surgical techniques, and clinical outcomes.

METHODS Between 2005 and 2021, the authors used the contralateral subfrontal approach in 74 consecutive patients presenting with TSMs. The surgical decision-making process and surgical techniques are described, and the clinical outcomes were retrospectively analyzed.

RESULTS The mean patient age was 54.4 years, with a female predominance (n = 61, 82%). Preoperatively, 61 patients (82%) had vision symptoms and 73 (99%) had optic canal invasion by tumor. Gross-total resection was achieved in almost all patients (n = 70, 95%). The visual function improvement and stabilization rate was 91% (67/74). Eight patients (11%) showed a worsening of visual function on the less-compromised (approach-side) optic nerve. There was no occurrence of cerebrospinal fluid leakage. Four patients (5%) experienced recurrences after the initial operation (mean follow-up duration 63 months). There were no deaths in this study.

CONCLUSIONS The contralateral subfrontal approach provides a high chance of complete tumor removal and visual improvement with limited complications and recurrences, especially when the tumor is in a unilateral or midline location causing unilateral visual symptoms or bilateral asymmetrical visual symptoms, regardless of tumor size or encasement of major vessels. With the appropriate patient selection, surgical technique, and familiarity with surrounding neurovascular structures, this approach is reliable for TSM surgery.

Practical Technique for Transcortical / Transventricular Colloid Cyst Removal Independent of Ventricular Size

Operative Neurosurgery 24:E61–E67, 2023

In the presence of a dilated foramen of Monro, a transcortical, transforaminal approach is considered the safest and simplest approach for resection of colloid cysts. However, in the presence of small or normal frontal horns, numerous microsurgical approaches and, often complicated, variations have been described, invariably employing forms of stereotactic navigation.

OBJECTIVE: To report an alternative, accurate, microsurgical stereotactic low-profile technique.

METHODS: The small frontal horn is stereotactically targeted as previously described. Routine equipment is used to accurately create a novel, rigid, atraumatic surgical corridor.

RESULTS: After a 7-mm corticotomy, a peel-away catheter carrying the AxiEM stylet engages the target set as the frontal horn. All joints of the endoscope holder are locked, allowing only catheter advancement (y axis) while lateral (x axis) or anteroposterior (z axis) movements are secure. Two, 7-mm retractor blades are inserted. The extremely consistent anatomy of the foramen of Monro allows en bloc microsurgical removal without unnecessary coagulation of cyst wall or choroid plexus.

CONCLUSION: Despite a plethora of approaches to the rostral third ventricle, in the presence of normal or small frontal horns, including creation of transcallosal/ interforniceal, suprachoroidal (or transchoroidal), and sub-choroidal, colloid cyst resection does not necessarily need to be convoluted. Technical nuances of an accurate, practical, minimally invasive technique are described.

Sacrifice or preserve the superior petrosal vein in microvascular decompression surgery

J Neurosurg 138:390–398, 2023

In microvascular decompression (MVD) surgery through the retrosigmoid approach, the surgeon may have to sacrifice the superior petrosal vein (SPV). However, this is a controversial maneuver. To date, high-level evidence comparing the operative outcomes of patients who underwent MVD with and without SPV sacrifice is lacking. Therefore, this study sought to bridge this gap.

METHODS The authors searched the Medline and PubMed databases with appropriate Medical Subject Heading (MeSH) terms and keywords. The primary outcome was vascular-related complications; secondary outcomes were new neurological deficit, cerebrospinal fluid (CSF) leak, and neuralgia relief. The pooled proportions of outcomes and OR (95% CI) for categorical data were calculated by using the logit transformation and Mantel-Haenszel methods, respectively.

RESULTS Six studies yielding 1143 patients were included, of which 618 patients had their SPV sacrificed. The pooled proportion (95% CI) values were 3.82 (0.87–15.17) for vascular-related complications, 3.64 (1.0–12.42) for new neurological deficits, 2.85 (1.21–6.58) for CSF leaks, and 88.90 (84.90–91.94) for neuralgia relief. The meta-analysis concluded that, whether the surgeon sacrificed or preserved the SPV, the odds were similar for vascular-related complications (2.5% vs 1.5%, OR [95% CI] 1.01 [0.33–3.09], p = 0.99), new neurological deficits (1.2% vs 2.8%, OR [95% CI] 0.55 [0.18–1.66], p = 0.29), CSF leak (3.1% vs 2.1%, OR [95% CI] 1.16 [0.46–2.94], p = 0.75), and neuralgia relief (86.6% vs 87%, OR [95% CI] 0.96 [0.62–1.49], p = 0.84).

CONCLUSIONS SPV sacrifice is as safe as SPV preservation. The authors recommend intentional SPV sacrifice when gentle retraction fails to enhance surgical field visualization and if the surgeon encounters SPV-related neurovascular conflict and/or anticipates impeding SPV-related bleeding.


Dual Dural Patch Graft With AlloDerm and DuraGen Underlay for Duraplasty in Chiari Malformation Results in Significantly Decreased Cerebrospinal Fluid Leak Complications

Operative Neurosurgery 24:162–167, 2023

Grafts available for posterior fossa dural reconstruction after Chiari decompression surgery include synthetic, xenograft, allograft, and autograft materials. The reported rates of postoperative pseudomeningocele and cerebrospinal fluid leak vary, but so far, no dural patch material or technique has sufficiently eliminated these problems.

OBJECTIVE: To compare the incidence of graft-related complications after posterior fossa surgery using AlloDerm alone vs AlloDerm with a DuraGen underlay.

METHODS: We performed a retrospective single-center study of a cohort of 106 patients who underwent Chiari decompression surgery by a single surgeon from 2014 through 2021. Age, sex, body mass index, tonsillar descent, syrinx formation, type of dural graft, and follow-up data were analyzed using univariate and χ2 statistical tests.

RESULTS: The AlloDerm-only group had a percutaneous cerebrospinal fluid (CSF) leak rate of 8.6% vs a 0% rate in the dual graft group (P = .037). At initial follow-up, there was a 15.5% combined rate of pseudomeningocele formation plus CSF leak in the AlloDerm-only group vs 18.8% in the AlloDerm + DuraGen group (P = .659). However, the pseudomeningoceles were larger in the AlloDerm-only cohort (45.5 vs 22.4 mm anteroposterior plane, P = .004), and 5 patients in this group required operative repair (56%). All pseudomeningoceles resolved without reoperation in the AlloDerm + DuraGen group (P = .003).

CONCLUSION: The use of a DuraGen underlay with a sutured AlloDerm dural patch resulted in significantly fewer CSF-related complications and eliminated the need for reoperation compared with AlloDerm alone. This single-center study provides evidence that buttressing posterior fossa dural grafts with a DuraGen underlay may decrease the risk of postoperative complications.

Internal neurolysis versus intraoperative glycerin rhizotomy for trigeminal neuralgia

J Neurosurg 138:270–275, 2023

Internal neurolysis (IN) and intraoperative glycerin rhizotomy (ioGR) are emerging surgical options for patients with trigeminal neuralgia without neurovascular contact. The objective of this study was to compare the neurological outcomes of patients who underwent IN with those of patients who underwent ioGR.

METHODS The authors retrospectively reviewed all patients who underwent IN or ioGR for trigeminal neuralgia at our institution. Patient demographic characteristics and immediate postoperative outcomes, as well as long-term neurological outcomes, were compared.

RESULTS Of 1044 patients who underwent open surgical treatment for trigeminal neuralgia, 56 patients underwent IN and 91 underwent ioGR. Of these 147 patients, 37 had no evidence of intraoperative neurovascular conflict. All patients who underwent IN and 96.7% of patients who underwent ioGR had immediate postoperative pain relief. At last followup, patients who underwent IN had lower Barrow Neurological Institute (BNI) pain intensity scores (p = 0.05), better BNI facial numbness scores (p < 0.01), and a greater degree of pain improvement (p = 0.05) compared with those who underwent ioGR. Patients who underwent IN also had significantly lower rates of symptomatic pain recurrence (p < 0.01) at last follow-up over an average of 9.5 months.

CONCLUSIONS IN appears to provide patients with a greater degree of pain relief, lower rates of facial numbness, and lower rates of pain recurrence compared with ioGR. Future prospective studies will better characterize long-term pain recurrence and outcomes.


Anterior transtemporal endoscopic selective amygdalohippocampectomy

Acta Neurochirurgica (2022) 164:2841–2849

Selective amygdalohippocampectomy (SelAH) is one of the most common surgical treatments for mesial temporal sclerosis. Microsurgical approaches are associated with the risk of cognitive and visual deficits due to damage to the cortex and white matter (WM) pathways. Our objective is to test the feasibility of an endoscopic approach through the anterior middle temporal gyrus (aMTG) to perform a SelAH.

Methods Virtual simulation with MRI scans of ten patients (20 hemispheres) was used to identify the endoscopic trajectory through the aMTG. A cadaveric study was performed on 22 specimens using a temporal craniotomy. The anterior part of the temporal horn was accessed using a tubular retractor through the aMTG after performing a 1.5 cm corticectomy at 1.5 cm posterior to the temporal pole. Then, an endoscope was introduced. SeIAH was performed in each specimen. The specimens underwent neuronavigation-assisted endoscopic SeIAH to confirm our surgical trajectory. WM dissection using Klingler’s technique was performed on five specimens to assess WM integrity.

Results This approach allowed the identification of collateral eminence, lateral ventricular sulcus, choroid plexus, inferior choroidal point, amygdala, hippocampus, and fimbria. SelAH was successfully performed on all specimens, and CT neuronavigation confirmed the planned trajectory. WM dissection confirmed the integrity of language pathways and optic radiations.

Conclusions Endoscopic SelAH through the aMTG can be successfully performed with a corticectomy of 15 mm, presenting a reduced risk of vascular injury and damage to WM pathways. This could potentially help to reduce cognitive and visual deficits associated with SelAH.

Prone Transpsoas Lateral Lumbar Interbody Fusion for Degenerative Lumbar Spine Disease

Operative Neurosurgery 23:382–388, 2022

Lateral lumbar interbody fusion has inherent limitations, such as the necessity to reposition the patient. To overcome this limitation, the prone transpsoas (PTP) approach for lateral lumbar interbody fusion has been developed.

OBJECTIVE: To report clinical and radiographic outcome measures of a series of patients who underwent PTP at our hospital. METHODS: A retrospective chart review was conducted to identify patients who underwent PTP for degenerative lumbar spine disease between September 2019 and August 2021. A thorough analysis of clinical and radiographic outcome measures for these patients was conducted.

RESULTS: Our search resulted in the identification of 15 consecutive patients. Four patients were operated using the assistance of fluoroscopy-based instrument tracking. Overall, the mean follow-up duration was 11.9 ± 7.9 months. Radiographically, the PTP approach resulted in significant postoperative improvement of lumbar lordosis (P = .03) and pelvic incidence minus lumbar lordosis (P < .005). No significant difference was found postoperatively in other regional sagittal alignment parameters, including pelvic tilt, sacral slope, or pelvic incidence. Clinically, the patients’ Oswestry Disability Indices (P = .002) and Short Form Survey-12 Physical Scores improved significantly (P = .01). The estimated mean blood loss for patients who underwent the PTP procedure was 137.7 ± 96.4 mL, the mean operative time was 212.5 ± 77.1 minutes, and the mean hospital stay was 2.7 ± 1.4 days. One patient each had superficial wound infection, transient paralytic ileus, transient pulmonary embolism, transient urinary retention, or required revision lumbar surgery.

CONCLUSION: This study demonstrates that the PTP approach is associated with significant improvement in radiographic and clinical outcomes.

KEY WORDS: Fluoroscopy-based instrument tracking, Lateral lumbar interbody fusion, Lumbar lordosis, Prone transpsoas, Sagittal alignment

Basilar decompression via a far lateral transcondylar approach

Acta Neurochirurgica (2022) 164:2563–2572

Treatments for symptomatic or unstable basilar invagination (BI) include posterior decompression, distraction/ fusion, trans-nasal or trans-oral anterior decompression, and combined techniques, with the need for occipitocervical fusion based on the degree of craniocervical instability. Variations of the far lateral transcondylar approach are described in limited case series for BI, but have not been widely applied.

Methods A single-institution, retrospective review of consecutive patients undergoing a far lateral transcondylar approach for odontoidectomy (± resection of the inferior clivus) followed by occipitocervical fusion over a 6-year period (1/1/2016 to 12/31/2021) is performed. Detailed technical notes are combined with images from cadaveric dissections and patient surgeries to illustrate our technique using a lateral retroauricular incision.

Results Nine patients were identified (3 males, 6 females; mean age 40.2 ± 19.6 years). All patients had congenital or acquired BI causing neurologic deficits. There were no major neurologic or wound-healing complications. 9/9 patients (100%) experienced improvement in preoperative symptoms.

Conclusions The far lateral transcondylar approach provides a direct corridor for ventral brainstem decompression in patients with symptomatic BI. A comprehensive knowledge of craniovertebral junction anatomy is critical to the safe performance of this surgery, especially when using a lateral retroauricular incision.

Circumferential sulcus-guided resection technique for improved outcomes of low-grade gliomas

J Neurosurg 137:1015–1025, 2022

Many neurosurgeons resect nonenhancing low-grade gliomas (LGGs) by using an inside-out piecemeal resection (PMR) technique. At the authors’ institution they have increasingly used a circumferential, perilesional, sulcusguided resection (SGR) technique. This technique has not been well described and there are limited data on its effectiveness. The authors describe the SGR technique and assess the extent to which SGR correlates with extent of resection and neurological outcome.

METHODS The authors identified all patients with newly diagnosed LGGs who underwent resection at their institution over a 22-year period. Demographics, presenting symptoms, intraoperative data, method of resection (SGR or PMR), volumetric imaging data, and postoperative outcomes were obtained. Univariate analyses used ANOVA and Fisher’s exact test. Multivariate analyses were performed using multivariate logistic regression.

RESULTS Newly diagnosed LGGs were resected in 519 patients, 208 (40%) using an SGR technique and 311 (60%) using a PMR technique. The median extent of resection in the SGR group was 84%, compared with 77% in the PMR group (p = 0.019). In multivariate analysis, SGR was independently associated with a higher rate of complete (100%) resection (27% vs 18%) (OR 1.7, 95% CI 1.1–2.6; p = 0.03). SGR was also associated with a statistical trend toward lower rates of postoperative neurological complications (11% vs 16%, p = 0.09). A subset analysis of tumors located specifically in eloquent brain demonstrated SGR to be as safe as PMR.

CONCLUSIONS The authors describe the SGR technique used to resect LGGs and show that SGR is independently associated with statistically significantly higher rates of complete resection, without an increase in neurological complications, than with PMR. SGR technique should be considered when resecting LGGs.

Occipito‑transtentorial approach for falcotentorial meningiomas

Acta Neurochirurgica (2022) 164:2505–2509

Falcotentorial meningiomas are rare tumors that arise at the junction of the dural folds of the tentorium and falx cerebri, at the junction of the vein of Galen with the straight sinus with possible extensions along the course of the straight sinus. Surgery of falcotentorial meningiomas remains challenging due to the intimate neurovascular relationships in the posterior incisural space.

Methods We describe the key steps of the occipito-transtentorial approach for falcotentorial meningiomas with a video illustration. The surgical anatomy is described along with the advantages and limitations of this approach.

Conclusion The occipito-transtentorial approach offers good surgical exposure and outcomes in carefully selected patients harboring falcotentorial meningiomas. Precise understanding of the relationship between the tumor and the internal cerebral veins, basal veins, and vein of Galen should be thoroughly analyzed as these structures may be infiltrated or displaced.

A new simple and free tubular device for microscopic transcortical approach to deep‑seated lesions

Acta Neurochirurgica (2022) 164:2049–2055

Surgery for deep-seated brain tumors remains challenging. Transcortical approaches often require brain retraction to ensure an adequate surgical corridor, thus possibly leading to brain damage. Various techniques have been developed to minimize brain retraction such as self-retaining retractors, endoscopic approaches, or tubular retractor systems. Even if they evenly distribute the mechanical pressure over the parenchyma, rigid retractors can also cause some degree of brain damage and have significant disadvantages. We propose here a soft cottonoid retractor for microscopic resection of deepseated and ventricular lesions.

Methods Through a small corticectomy, a channel route with a blunt cannula is developed until the lesion is reached. Then, a “balloon-like system” made with a surgical glove is progressively inflated, dilatating the surgical corridor. A mini-tubular device, handmade by suturing a surgical cottonoid, is positioned into the corridor, unfolded, and sutured to the edge of the dura, to prevent it from being progressively expelled from the working channel. This allows a good visualization of the lesion and surrounding structures under the microscope.

Results Advantages of this technique are the softness of the tube walls, the absence of rigid arm to hold the tube, and the possibility for the tube to follow the movements of the instruments and to modify its orientation according to the working area.

Conclusion This simple and inexpensive tubular working channel for microscopic transcortical approach is a valuable alternative technique to traditional self-retaining retractor and rigid tube for the microsurgical resection of deep-seated brain tumors.

Supraorbital and mini-pterional keyhole craniotomies for brain tumors

J Neurosurg 136:1314–1324, 2022

The authors’ objective was to compare the indications, outcomes, and anatomical limits of supraorbital (SO) and mini-pterional (MP) craniotomies in patients with intra- and extraaxial brain tumors, and to assess approach selection, utility of endoscopy, and surgical field overlap.

METHODS A retrospective analysis was conducted of all brain tumor patients who underwent an SO or MP approach. The analyzed characteristics included pathology, endoscopy use, extent of resection, length of stay (LOS), and complications. On the basis of preoperative MRI data, tumor heatmaps were constructed to compare surgical access provided by both routes, including coronal projection heatmaps for parasellar tumors.

RESULTS From 2007 to 2020, 158 patients underwent 173 (84.8%) SO craniotomies and 30 patients underwent 31 (15.2%) MP craniotomies; 71 (34.8%) procedures were reoperations. Of these 204 operations, 110 (63.6%) SO and 21 (67.7%) MP approaches were for extraaxial tumors (meningiomas in 65% and 76.2%, respectively). Gliomas and metastases together represented 84.1% and 70% of intraaxial tumors accessed with SO and MP approaches, respectively. Overall, 56.1% of tumors accessed with the SO approach and 41.9% of those accessed with the MP approach were in the parasellar region. Axial projection heatmaps showed that SO access extended along the entire ipsilateral and medial contralateral anterior cranial fossa, parasellar region, ipsilateral sylvian fissure, medial middle cranial fossa, and anterior midbrain, whereas MP access was limited to the ipsilateral middle cranial fossa, sylvian fissure, lateral parasellar region, and posterior aspect of anterior cranial fossa. Coronal projection heatmaps showed that parasellar access extended further superiorly with the SO approach compared with that of the MP approach. Endoscopy was utilized in 98 (56.6%) SO craniotomies and 7 (22.6%) MP craniotomies, with further tumor resection in 48 (49%) and 5 (71.4%) cases, respectively. Endoscope-assisted tumor removal was clustered in areas that were generally at farther distances from the craniotomy or in angled locations such as the cribriform plate region where microscopic visualization is limited. Gross-total or neartotal resection was achieved in 120/173 (69%) SO approaches and 21/31 (68%) MP approaches. Major complications occurred in 11 (6.4%) SO approaches and 1 (3.2%) MP approach (p = 0.49). The median LOS decreased to 2 days in the last 2 years of the study.

CONCLUSIONS This clinical experience suggests the SO and MP craniotomies are versatile, safe, and complementary approaches for tumors located in the anterior and middle cranial fossae and perisylvian and parasellar regions. The SO route, used in 85% of cases, achieved greater overall reach than the MP route. Both approaches may benefit from expanded visualization with endoscopy.


Treatment Strategies for Different Types of Intraneural Offending Vessels in Microvascular Decompression Surgery for Trigeminal Neuralgia

Neurosurgery 90:562–568, 2022

Microvascular decompression (MVD) surgery is the treatment of choice for trigeminal neuralgia (TGN). However, decompression becomes difficult when the offending vessel penetrates the trigeminal nerve root.

OBJECTIVE: To estimate the rates and patterns of different types of intraneural offending vessels in patients with TGN for MVD and to discuss respective management strategies. METHODS: All patients with TGN undergoing MVD in our center from January 1, 2015, to December 31, 2019, were analyzed retrospectively. The intraneural offending vessels included veins and arteries. The postoperative pain relief rate, complications, and recurrences were evaluated.

RESULTS: Of the 302 TGN cases, the intraneural offending vessels were identified in 58 of the cases (19.2%). The 9 cases (15.5%) of intraneural offending arteries were decompressed using shredded Teflon wrapping interposition. Of the 49 cases (84.5%) of intraneural offending veins (INOVs), 29 were not considered true offending vessels, and the treatment only addressed the offending artery in these patients. Of the remaining 20 INOVs, 15 were electrocoagulated and divided, and 5 were decompressed with shredded Teflon. Complete pain relief was achieved in all 58 patients. However, the pain recurred in 5 patients (8.6%), and transient hemifacial numbness occurred in 4 patients (6.9%).

CONCLUSION: Intraneural offending vessels requiring treatment are uncommon and are seen in less than 1 in 10 patients undergoing MVD for TGN. For intraneural offending artery, decompression by shredded Teflon wrapping interposition is recommended. Management of the INOV depends on the individual situations, and the management includes sacrifice, wrapping decompression, or leaving them untreated.


Retrolabyrinthine transsigmoid approach to complex parabrainstem tumors in the posterior fossa

J Neurosurg 136:1097–1102, 2022

The surgical management of large and complex tumors of the posterior fossa poses a formidable challenge in neurosurgery. The standard retrosigmoid craniotomy approach has been performed at most neurosurgical centers; however, the retrosigmoid approach may not provide enough working space without significant retraction of the cerebellum. The transsigmoid approach provides wider and shallower surgical fields; however, there have been few clinical and no cadaveric studies on its usefulness. In the present study, the authors describe the transsigmoid approach in clinical cases and cadaveric specimens.

METHODS For the clinical study, the authors retrospectively reviewed the medical records and operative charts of patients who had been surgically treated for parabrainstem tumors using the transsigmoid approach between 1997 and 2019. They analyzed patient demographic and clinical data, as well as surgical and clinical outcomes. In the cadaveric study, they compared the surgical views obtained in different approaches (retrosigmoid, presigmoid, retrolabyrinthine, and transsigmoid) and measured the sigmoid sinus width at the level of the endolymphatic sac and the distance between the anterior edge of the sigmoid sinus and the endolymphatic sac on 35 sides in 19 cadaveric specimens.

RESULTS A total of 21 patients (6 males and 15 females) with a mean age of 42.2 (range 15–67) years were included in the clinical study. Eleven patients had meningioma, 7 had vestibular schwannoma, 2 had hemangioblastoma, and 1 had epidermoid cyst. Gross-total, near-total, and subtotal removal were achieved in 7 (33.3%), 3 (14.3%), and 11 (52.4%) patients, respectively. In the cadaveric study, 19 cadaveric specimens were used. The sigmoid sinus was cut in the middle, and the incision was extended from the retrosigmoid to the presigmoid dura. The dura was then retracted upward and downward like opening a door. The results indicated that this technique can widen the operative field anteriorly by approximately 2 cm as compared to the retrosigmoid approach and provides a better view anterior to the brainstem.

CONCLUSIONS The transsigmoid approach is useful for complex parabrainstem tumors in the posterior fossa because it provides a wider and shallower operative view with less retraction of the cerebellum. This enables safer tumor removal with less damage to important structures in the posterior fossa, resulting in better operative and clinical outcomes.


Double pedicled nasoseptal flap for skull base repair after endoscopic expanded endonasal approach

Acta Neurochirurgica (2022) 164:1111–1114

Expanded endonasal approach offers a spectacular corridor for skull base tumour resection but requires reliable multilayer reconstruction techniques with a vascularized nasoseptal flap.

Method On the basis on our substantial experience of 136 patients operated on between January 2008 and January 2020, the double pedicled nasoseptal flap technique was developed for skull base repair. The technique is finely detailed. The nasal floor mucosa was preserved. CSF leakage occurred in 4% of patients.

Conclusion Double pedicled nasoseptal flap is a reproducible and efficient technique for skull base reconstruction after expanded endonasal approach and is associated with limited rhinological complications.

The mini-combined transpetrosal approach: an anatomical study and comparison with the combined transpetrosal approach

Acta Neurochirurgica (2022) 164:1079–1093

The combined transpetrosal approach (CTPA) is a versatile technique suitable for challenging skull base pathologies. Despite the advantages provided by a wide surgical exposure, the soft tissue trauma, complex and time-consuming bony work, and cosmetic issues make it far from patient expectations. In this study, the authors describe a less invasive modification of the CTPA, the mini-combined transpetrosal approach (mini-CTPA), and perform a quantitative comparison between these two approaches.

Methods Five human specimens were used for this study. CTPA was performed on one side and mini-CTPA on the opposite side. The surgical freedom, petroclival and brainstem area of exposure, and maneuverability for 6 anatomical targets, provided by the CTPA and mini-CTPA, were calculated and statistically compared. The bony volumes corresponding to each anterior petrosectomy were also measured and compared. Three clinical cases with an operative video are also reported to illustrate the effectiveness of the approach.

Results The question-mark skin incision done along the muscle attachments permits an optimal cosmetic result. Even though the limited incision, the smaller craniotomy, and the less extensive bone drilling of mini-CTPA provide a smaller area of surgical freedom, the areas of exposure of petroclival region and brainstem were not statistically different between the two approaches. The antero-posterior maneuverability for the oculomotor foramen (OF), Meckel’s cave (MC) and the REZ of trigeminal nerve, and the supero-inferior maneuverability for OF, MC, Dorello’s canal, and REZ of CN VII are significantly reduced by the smaller opening. The bony volume of anterior petrosectomy resulted similar among the approaches.

Conclusions The mini-CTPA is an interesting alternative to the CTPA, providing comparable surgical exposure both for petroclival region and for brainstem. Although the lesser soft tissue dissection and bony opening decrease the surgical maneuverability, the mini-CTPA may reduce surgical time, potential approach-related morbidities, and improve cosmetic and functional outcomes for the patients.

Paravertebral foramen screw fixation for posterior cervical spine surgery

J Neurosurg Spine 36:479–486, 2022

OBJECTIVE The goal of this study was to clarify the clinical utility of paravertebral foramen screws (PVFSs) and to determine intraoperative indicators for appropriate screw placement during posterior cervical fusion surgery to improve its safety.

METHODS The authors included data from 46 patients (29 men and 17 women, mean age 61.7 years) who underwent posterior cervical spine surgery with 94 PVFSs. Of the 94 PVFSs, 77 were used in C6, 9 in C3, 5 in C4, and 3 in C5. According to the cervical lateral radiographic view, the authors divided the 94 PVFSs into 3 groups as follows: a longer group, in which the tip of PVFS was located anteriorly from the line of the posterior wall of the vertebral body (> +0 mm); an intermediate group, in which the screw tip was located up to 2 mm posteriorly to the posterior wall of the vertebral body (–2 to 0 mm); and a shorter group, in which the screw tip was located more than 2 mm posteriorly (< –2 mm). The accuracy of screw placement was assessed using CT imaging in the axial plane, and the proportion of screws penetrating a vertebral foramen or a transverse foramen was compared between the 3 groups. Screw loosening was defined as a lucent zone around the screw evaluated on cervical radiography at 1 year after surgery. Complications related to PVFS insertion and revision surgery related to PVFS were evaluated.

RESULTS The authors classified 25 PVFSs into the longer group, 43 into the intermediate group, and 26 into the shorter group. The proportion of screws penetrating a vertebral foramen was largest in the shorter group, and the proportion penetrating a transverse foramen was largest in the longer group. Screw loosening was confirmed for 3 of 94 PVFSs. One PVFS inserted in C6 unilaterally within a long construct from C2 to C7 showed loosening, but it did not cause clinical symptoms. Revision surgery was required for 2 PVFSs inserted in C3 bilaterally as the lower instrumented vertebra in occiput–cervical fusion because they pulled out. There was no neurovascular complication related to PVFS insertion.

CONCLUSIONS PVFSs are useful for posterior cervical fusion surgery as alternative anchor screws, and the line of the posterior wall of the cervical body on lateral fluoroscopic images is a potential intraoperative reference to indicate an appropriate trajectory for PVFSs.

How I do it: horizontal fissure approach to the middle cerebellar peduncle

Acta Neurochirurgica (2022) 164:763–766

The horizontal fissure approach is a workhorse for brainstem lesions in the central and dorsolateral pons and middle cerebellar peduncle (MCP). The cerebellopontine fissure is a V-shaped fissure with a superior and inferior limb between the cerebellum, pons, and MCP. The horizontal or petrosal fissure is at the apex of the cerebellopontine fissure and extends laterally to divide the petrosal surface of the cerebellum into superior and inferior parts. Splitting this fissure exposes the posterolateral aspect of the MCP without excessive retraction or transgression of the cerebellum.

Method We demonstrate and describe the horizontal fissure operative approach to the middle cerebellar peduncle for resection of a pontine cavernoma with illustrative figures and operative video.

Conclusion Splitting the horizontal (petrosal) fissure of the cerebellum brings the middle cerebellar peduncle into view behind the root entry zone of the trigeminal nerve, providing an expanded, safe corridor to the central and dorsolateral pons.


Single-position prone lateral transpsoas approach: early experience and outcomes

J Neurosurg Spine 36:358–365, 2022

Lateral lumbar interbody fusion (LLIF) via a transpsoas approach is a workhorse minimally invasive approach for lumbar arthrodesis that is often combined with posterior pedicle screw fixation. There has been increasing interest in performing single-position surgery, allowing access to the anterolateral and posterior spine without requiring patient repositioning. The feasibility of the transpsoas approach in patients in the prone position has been reported. Herein, the authors present a consecutive case series of all patients who underwent single-position prone transpsoas LLIF performed by an individual surgeon since adopting this approach.

METHODS A retrospective review was performed of a consecutive case series of adult patients (≥ 18 years old) who underwent single-position prone LLIF for any indication between October 2019 and November 2020. Pertinent operative details (levels, cage use, surgery duration, estimated blood loss, complications) and 3-month clinical outcomes were recorded. Intraoperative and 3-month postoperative radiographs were reviewed to assess for interbody subsidence.

RESULTS Twenty-eight of 29 patients (97%) underwent successful treatment with the prone lateral approach over the study interval; the approach was aborted in 1 patient, whose data were excluded. The mean (SD) age of patients was 67.9 (9.3) years; 75% (21) were women. Thirty-nine levels were treated: 18 patients (64%) had single-level fusion, 9 (32%) had 2-level fusion, and 1 (4%) had 3-level fusion. The most commonly treated levels were L3–4 (n = 15), L2–3 (n = 12), and L4–5 (n = 11). L1–2 was fused in 1 patient. The mean operative time was 286.5 (100.6) minutes, and the mean retractor time was 29.2 (13.5) minutes per level. The mean fluoroscopy duration was 215.5 (99.6) seconds, and the mean intraoperative radiation dose was 170.1 (94.8) mGy. Intraoperative subsidence was noted in 1 patient (4% of patients, 3% of levels). Intraoperative lateral access complications occurred in 11% of patients (1 cage repositioning, 2 inadvertent ruptures of anterior longitudinal ligament). Subsidence occurred in 5 of 22 patients (23%) with radiographic follow-up, affecting 6 of 33 levels (18%). Postoperative functional testing (Oswestry Disability Index, SF-36, visual analog scale–back and leg pain) identified significant improvement.

CONCLUSIONS This single-surgeon consecutive case series demonstrates that this novel technique is well tolerated and has acceptable clinical and radiographic outcomes. Larger patient series with longer follow-up are needed to further elucidate the safety profile and long-term outcomes of single-position prone LLIF.

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