BACKGROUND AND OBJECTIVES: Exposure of the root entry zone (REZ) of the trigeminal nerve (TN) for microvascular decompression is commonly obtained with a retrosigmoid approach, with or without endoscopic assistance. We hypothesized that adequate exposure of the TN REZ could be obtained through an endoscopic retrolabyrinthine (RL) approach. We aim to quantify exposure of the REZ of the TN using endoscopic RL approach, with and without drilling of the suprameatal tubercle of the internal auditory canal. METHODS: Surgical dissection was performed bilaterally on 3 embalmed cadaveric human heads at the anatomy laboratory of the House Institute. Heads were scanned for volumetric analysis using 3D Slicer software both before and after dissection. Extent of exposure was quantified in 2 ways: first, by assessment of the surgeon's ability to visualize 16 predetermined anatomic landmarks with the endoscope and second, we estimated the “working” area by placing fiducials under the fully endoscopic view and calculating the resultant 3D volume. RESULTS: Using the standard endoscopic RL approach, an average of 13.8 landmarks (range 12-16) was visualized. The estimated working volume exposed by the RL on each side of each head varied from 189.28 to 527.85 mm3. Drilling of the suprameatal tubercle provided both increases in landmark visualization and, on average, an additional 55 mm3 of working volume. CONCLUSION: The endoscopic RL approach is a viable alternative to the standard retrosigmoid approach. Potential advantages of the RL include a more lateral trajectory that minimizes the need for cerebellar retraction and a shorter working distance and shallower angle to the cerebellopontine angle. Potential disadvantages include longer surgery time, increased technical difficulty of exposure, and potential for cerebrospinal fluid leak and or hearing loss.

BACKGROUND AND OBJECTIVES: Cubital tunnel syndrome is the second most common nerve entrapment, and understanding the anatomy is crucial for the success of the nerve release. During ulnar nerve release for cubital tunnel syndrome, a motor branch is frequently encountered crossing anteriorly over the ulnar nerve from its medial/ulnar side proximally to the lateral/radial side distally. Little has been noted about this crossing branch in the literature. In this anatomic study, we sought to characterize this branch further and discuss its potential significance in cubital tunnel release. METHODS: We performed a cadaveric dissection of 48 elbow specimens as if performing a cubital tunnel release. We assessed for the presence of the crossing motor branch of the ulnar nerve and measured the distance from the medial epicondyle to the branch takeoff and to its target of innervation. RESULTS: Of our 48 specimens, 34 (71%) were noted to have a crossing motor branch at the area of compression by the deep flexor carpi ulnaris muscle fascia (common aponeurosis). On average, the distance from the medial epicondyle to the branch origin from the ulnar nerve was 18.2 mm and to the target muscle innervation was 28.4 mm. CONCLUSION: Identifying this branch is important for performing a cubital tunnel release, and awareness of this anatomy during ulnar nerve decompression procedures may help avoid injury to this motor branch.

BACKGROUND AND OBJECTIVES: The cavernous internal carotid artery (cICA) and its branches can make it challenging to approach the lateral portion of the retrocarotid area of the cavernous sinus (RcACS) and surrounding areas during the endoscopic endonasal approach (EEA). This can sometimes require more invasive transcranial approaches, causing a higher risk of complications. We sought to explore the feasibility of adding a contralateral transmaxillary (CTM) corridor to improve access to the RcACS during EEA. METHODS: We performed EEA and CTM extensions on 6 cadavers (12 sides) using image guidance. The depth of the surgical corridor, the surgical exposure, the angle of attack, and the trajectory to the anterior genu of the cICA were measured. Two illustrative clinical cases are presented. RESULTS: Compared with the contralateral transnasal approach, the CTM corridor provided a 10.76 (5.32)-mm shorter distance (P < .001), 36.23% (20.70%) larger surgical exposure (P < .001), and a 24.6° (3.4°) more parallel trajectory to the anterior genu of the cICA (P < .001). The mean angle of the lateral nasal wall line and the middle eye line was equal to the mean angle of the contralateral transnasal (P = .075) and CTM (P = .262) approaches, respectively. The CTM corridor allowed us to achieve near-total resection of the RcACS and beyond in 2 invasive adenomas with significant lateral extension. CONCLUSION: The CTM corridor is a feasible addition to standard EEA to access the RcACS and beyond, providing a more medial-to-lateral trajectory and improved access. The middle eye line can be used as a reference to help select patients for this approach.

BACKGROUND AND OBJECTIVES: Patients with basilar invagination (BI) can be treated with several surgical options, ranging from simple posterior decompression to circumferential decompression and fusion. Here, we aimed at examining the indications and outcomes associated with these surgical strategies to devise a staged algorithm for managing BI. METHODS: We conducted a retrospective cohort study in 2 neurosurgical centers and included patients with a BI, as defined by a position of the dens tip at least 5 mm above the Chamberlain line. Other craniovertebral junction anomalies, such as atlas assimilation, platybasia, and Chiari malformations, were documented. C1-C2 stability was assessed with a dynamic computed tomography scan. RESULTS: We included 30 patients with BI with a mean follow-up of 56 months (min = 12, max = 166). Posterior decompression and fusion (n = 8) was only performed in cases of obvious atlanto-axial instability (eg, increased atlanto-dental interval or hypermobility on flexion/extension), while anterior decompression (transoral or transnasal) was reserved to patients with lower cranial nerves deficits (eg, swallowing dysfunction) and irreducible anterior compression (n = 9). Patients with posterior signs (eg, Valsalva headaches) or myelopathy but without C1-C2 instability nor anterior signs were managed with an isolated foramen magnum decompression, with or without duraplasty (n = 13). Complications were more frequent for combined procedures, including neurological deterioriation (n = 4) and tracheostomy (n = 2), but reinterventions were more likely in patients undergoing posterior decompression alone (n = 3). CONCLUSION: Patient selection is key to determine the appropriate surgical strategy for BI: In our experience, combined approaches are only needed for patients with irreducible and symptomatic anterior compression, while fusion should be restricted to patient with obvious signs of atlanto-axial instability. Other BI patients can be managed by foramen magnum decompression alone to minimize surgical morbidity.

BACKGROUND AND OBJECTIVES: Suprasellar tumors, particularly pituitary adenomas (PAs), commonly present with visual decline, and the endoscopic endonasal transsphenoidal approach (EETA) is the primary management for optic apparatus decompression. Patients presenting with complete preoperative monocular blindness comprise a high-risk subgroup, given concern for complete blindness. This retrospective cohort study evaluates outcomes after EETA for patients with PA presenting with monocular blindness. METHODS: Retrospective analysis of all EETA cases at our institution from June 2012 to August 2023 was performed. Inclusion criteria included adults with confirmed PA and complete monocular blindness, defined as no light perception, and a relative afferent pupillary defect secondary to tumor mass effect. RESULTS: Our cohort includes 15 patients (9 males, 6 females), comprising 2.4% of the overall PA cohort screened. The mean tumor diameter was 3.8 cm, with 6 being giant PAs (>4 cm). The mean duration of preoperative monocular blindness was 568 days. Additional symptoms included contralateral visual field defects (n = 11) and headaches (n = 10). Two patients presented with subacute PA apoplexy. Gross total resection was achieved in 46% of patients, reflecting tumor size and invasiveness. Postoperatively, 2 patients experienced improvement in their effectively blind eye and 2 had improved visual fields of the contralateral eye. Those with improvements were operated within 10 days of presentation, and no patients experienced worsened vision. CONCLUSION: This is the first series of EETA outcomes in patients with higher-risk PA with monocular blindness on presentation. In these extensive lesions, vision remained stable for most without further decline and improvement from monocular blindness was observed in a small subset of patients with no light perception and relative afferent pupillary defect. Timing from vision loss to surgical intervention seemed to be associated with improvement. From a surgical perspective, caution is warranted to protect remaining vision and we conclude that EETA is safe in the management of these patients.

The intraosseous subarcuate loop is an anatomic variant of the anterior inferior cerebellar artery (AICA), in which the artery gives off the subarcuate artery at the apex of the loop, entrapped in the subarcuate fossa (SF) of the temporal bone. First reported by Tanriover and Rhoton, 1 few others 2-5 have addressed this additional challenge during cerebellopontine angle surgery, occurring in 0.6%–4%. 3,6 We present a case of the safe mobilization of the intraosseous variant of the AICA and resection of a trigeminal schwannoma through a retrosigmoid approach with reverse anterior petrosectomy. Illustration of the same anatomic variation in a specimen is also provided. A 42-year-old male patient presented with intermittent right trigeminal neuropathy. MRI identified an extra-axial dumbbell-shaped heterogeneously contrast-enhancing lesion extending from the right Meckel cave into the cerebellopontine angle. The 3D-CISS sequence demonstrated a possible vascular loop of the right AICA within the SF. Physical examination was negative. Documented and verified informed consent was obtained. A right retrosigmoid craniotomy with reverse anterior petrosectomy was performed. The subarcuate artery was coagulated and divided, and the intraosseous loop of the AICA was safely mobilized, with the steps demonstrated on a specimen. The extra-axial mass was exposed, and gross total resection was achieved. The Doppler signal in AICA was appropriate at the end of the operation. The patient recovered well with mild ipsilateral trigeminal sensory loss and no new neurological deficits. Intraosseous AICA loop in the SF is a relatively common anatomic variation. Identification and safe mobilization are essential to avoid intraoperative lesion of AICA.

BACKGROUND AND OBJECTIVES: The primary objective of this study was to evaluate the influence of operating room nurse (ORN) characteristics on the duration of elective neurosurgical procedures in adults. In addition, we conducted a cost-benefit analysis of various strategies for organizing the workflow of ORNs. METHODS: We collected and analyzed operating times for adult elective neurosurgical procedures, categorizing them by surgeon, procedure complexity (dichotomized as technologically complex and simple), and ORN characteristics (dichotomized as ORN dedicated to neurosurgery [dORN] and ORN not dedicated to neurosurgery [ndORN]). The monetary valuation of operating times is based on the unitary cost per minute of the operating room, including opportunity costs of ORN, as well as their training costs and salaries. Cost-benefit analysis adopted the hospital perspective. RESULTS: Analysis of operating times reveals an approximately 20-minute difference for complex procedures when performed with ndORN. However, there is no significant difference in operating times for simple procedures, whether they are conducted by dORN or ndORN. The additional annual cost incurred by complex procedures performed with ndORN is estimated at CHF 68 144.4 for the Geneva University Hospitals. CONCLUSION: Complex neurosurgical procedures exhibit shorter durations when performed by dORNs. We explore several hypotheses to explain this difference. By adapting available human resources and optimizing workflow organization, hospitals can potentially achieve a net benefit.