Tag: Cranial nerves

Posted on

Skull Base Anatomy Presented in 360° Photogrammetry 3-Dimensional Models

Operative Neurosurgery 30:124–136, 2026

This article presents the creation of seven photorealistic 360° photogrammetric 3D models of the central skull base derived from stepwise dissections of a formalin-fixed, vessel-injected cadaveric head. The workflow—dissection stages, smartphone-based image capture, cloud photogrammetry, refinement in Blender, and VR/MR upload—enables immersive visualization of cranial nerves, ICA/vertebral segments, and regional anatomy.

The models offer progressive exocranial-to-endocranial perspectives for education and preoperative planning, highlighting cavernous sinus, infratemporal and pterygopalatine fossae, petrous bone, and foraminal relationships. Limitations include a single-specimen dataset, color variations from fixation, and resolution constraints in deep cavities; nevertheless, the freely accessible VR models complement traditional dissection and anatomical atlases.

360° Photogrammetric 3D Models: Realistic, photogrammetry-based 3D models of the central skull base were created from cadaveric dissections, offering immersive 360° visualization of complex neuroanatomical structures for enhanced spatial understanding.

Stepwise Dissection and Scanning: Seven progressive anatomical models were generated by systematically dissecting and scanning a formalin-fixed, vessel-injected head specimen, documenting both exocranial and endocranial perspectives.

Key Structures Visualized: The models detail the courses of cranial nerves, major vessels (including all internal carotid artery segments), skull base foramina, infratemporal and pterygopalatine fossae, paranasal sinuses, and deep neck spaces.

Technical Workflow: High-resolution images were captured using a smartphone multi-camera system, processed via cloud-based photogrammetry, refined in 3D software, and made accessible through web, VR, and MR platforms.

Educational Value: The interactive models allow customizable, layered exploration of anatomy, overcoming limitations of traditional 2D images and static atlases, and are freely accessible for educational and preoperative planning purposes.

Limitations: The study used a single specimen, which may not represent anatomical variants; image quality in deep/narrow regions could be further improved with advanced imaging and fixation techniques.

Broad Accessibility: Smartphone-based and cloud photogrammetry methods make high-resolution anatomical modeling more accessible and less resource-intensive, facilitating widespread dissemination.

Conclusions: 360° photorealistic 3D models significantly enhance comprehension of skull base anatomy and are a valuable adjunct to traditional teaching, with potential to improve neurosurgical training and patient outcomes.

Posted on

Novel classification of foramen magnum meningiomas predicted by topographic position relative to neurovascular bundle

Acta Neurochirurgica (2024) 166:199

Proximity to critical neurovascular structures can create significant obstacles during surgical resection of foramen magnum meningiomas (FMMs) to the detriment of treatment outcomes. We propose a new classification that defines the tumor’s relationship to neurovascular structures and assess correlation with postoperative outcomes.

Methods In this retrospective review, 41 consecutive patients underwent primary resection of FMMs through a far lateral approach. Groups defined based on tumor-neurovascular bundle configuration included Type 1, bundle ventral to tumor; Type 2a-c, bundle superior, inferior, or splayed, respectively; Type 3, bundle dorsal; and Type 4, nerves and/or vertebral artery encased by tumor.

Results The 41 patients (range 29–81 years old) had maximal tumor diameter averaging 30.1 mm (range 12.7–56 mm). Preoperatively, 17 (41%) patients had cranial nerve (CN) dysfunction, 12 (29%) had motor weakness and/or myelopathy, and 9 (22%) had sensory deficits. Tumor type was relevant to surgical outcomes: specifically, Type 4 demonstrated lower rates of gross total resection (65%) and worse immediate postoperative CN outcomes. Long-term findings showed Types 2, 3, and 4 demonstrated higher rates of permanent cranial neuropathy. Although patients with Type 4 tumors had overall higher ICU and hospital length of stay, there was no difference in tumor configuration and rates of postoperative complications or 30-day readmission.

Conclusion The four main types of FMMs in this proposed classification reflected a gradual increase in surgical difficulty and worse outcomes. Further studies are warranted in larger cohorts to confirm its reliability in predicting postoperative outcomes and possibly directing management decisions.

Posted on

Extradural disconnection of the cavernous sinus with preservation of the internal carotid artery: indication and technique

Acta Neurochirurgica (2023) 165:2951–2956

Extradural disconnection of the cavernous sinus (CS) with preservation of the internal carotid artery (ICA) is indicated for aggressive and recurrent tumors, in patients presenting loss of oculomotor function and non-functional circle of Willis.

Method Extradural resection of the anterior clinoid process disconnects the CS anteriorly. The ICA is dissected in the foramen lacerum via extradural subtemporal approach. The intracavernous tumor is split and removed following the ICA. Bleeding control of the inferior and superior petrosal and intercavernous sinuses completes posterior CS disconnection.

Conclusion This technique can be proposed for recurrent CS tumors and need of ICA preservation.

Posted on

Management of cavernous sinus meningiomas: Consensus statement on behalf of the EANS skull base section

Brain and Spine 2 (2022) 100864

The evolution of cavernous sinus meningiomas (CSMs) might be unpredictable and the efficacy of their treatments is challenging due to their indolent evolution, variations and fluctuations of symptoms, heterogeneity of classifications and lack of randomized controlled trials. Here, a dedicated task force provides a consensus statement on the overall management of CSMs. Research question: To determine the best overall management of CSMs, depending on their clinical presentation, size, and evolution as well as patient characteristics.

Material and methods: Using the PRISMA 2020 guidelines, we included literature from January 2000 to December 2020. A total of 400 abstracts and 77 titles were kept for full-paper screening.

Results: The task force formulated 8 recommendations (Level C evidence). CSMs should be managed by a highly specialized multidisciplinary team. The initial evaluation of patients includes clinical, ophthalmological, endocrinological and radiological assessment. Treatment of CSM should involve experienced skull-base neurosurgeons or neuro-radiosurgeons, radiation oncologists, radiologists, ophthalmologists, and endocrinologists.

Discussion and conclusion: Radiosurgery is preferred as first-line treatment in small, enclosed, pauci-symptomatic lesions/in elderly patients, while large CSMs not amenable to resection or WHO grade II-III are candidates for radiotherapy. Microsurgery is an option in aggressive/rapidly progressing lesions in young patients presenting with oculomotor/visual/endocrinological impairment. Whenever surgery is offered, open cranial approaches are the current standard. There is limited experience reported about endoscopic endonasal approach for CSMs and the main indication is decompression of the cavernous sinus to improve symptoms. Whenever surgery is indicated, the current trend is to offer decompression followed by radiosurgery.

Posted on

Hypertrophic Interstitial Neuropathy of the Trigeminal Nerve

Neurosurgery 87:E41–E47, 2020

Hypertrophic interstitial neuropathy (HIN) is an uncommon, non-neoplastic lesion typically affecting peripheral nerves. Cranial nerve (CN) involvement is exceedingly rare. We present a case of isolated trigeminal nerve HIN manifesting with V3 distribution neuralgia.

CLINICAL PRESENTATION: A 50-yr-old male presented with left sided trigeminal neuralgia refractory to medical management. The patient underwent retromastoid craniectomy for possible microvascular decompression. Intra-operatively, the trigeminal nerve appeared to be focally enlarged with a sausage-like configuration. We selectively resected 1 fascicle which was predominantly involved. Histopathological examination revealed onion bulb formations composed of Schwann cells around centrally placed axons. A diagnosis of HIN was made. Postoperatively, the patient experienced complete resolution of symptoms.

CONCLUSION: This is the third case of isolated trigeminal nerve HIN in the literature. We performed a selective resection in a patient presenting with trigeminal neuralgia, resulting in complete resolution of symptoms. It is reported here with intraoperative microscope images, along with a review and analysis of this topic as it related to CN.

Posted on

Probabilistic Tractography to Predict the Position of Cranial Nerves Displaced by Skull Base Tumors: Value for Surgical Strategy Through a Case Series of 62 Patients

Neurosurgery, Volume 85, Issue 1, July 2019, Pages E125–E136

Predicting the displacement of cranial nerves by tumors could make surgery safer and the outcome better. Recent advances in imaging and processing have overcome some of the limits associated with cranial nerve tractography, such as spatial resolution and fiber crossing. Among others, probabilistic algorithms yield to a more accurate depiction of cranial nerve trajectories.

OBJECTIVE: To report how cranial nerve probabilistic tractography can help the surgical strategy in a series of various skull base tumors.

METHODS: After distortion correction and region of interest seeding, a probabilistic tractography algorithm used the constrained spherical deconvolution model and attempted the reconstruction of cranial nerve trajectories in both healthy and displaced conditions.

RESULTS: Sixty-two patients were included and presented: vestibular schwannomas (n = 33); cerebellopontine angle meningiomas (n = 15); arachnoid or epidermoid cysts (n = 6); cavernous sinus and lower nerves schwannomas (n = 4); and other tumors (n = 4). For each patient, at least one ‘displaced’ cranial nerve was not clearly identified on classical anatomical MRI images. All 372 cranial nerves were successfully tracked on each healthy side; among the 175 cranial nerves considered ‘displaced’by tumors, 152 (87%) were success- fully tracked. Among the 127 displaced nerves of operated patients (n = 51), their position was confirmed intraoperatively for 118 (93%) of them. Conditions that led to tractography failure were detailed. On the basis of tractography, the surgical strategy was adjusted for 44 patients (71%).

CONCLUSION: This study reports a cranial nerve probabilistic tractography pipeline that can: predict the position of most cranial nerves displaced by skull base tumors, help the surgical strategy, and thus be a pertinent tool for future routine clinical application.

Posted on

Visualization of Cranial Nerves Using High-Definition Fiber Tractography

Visualization of Cranial Nerves Using High-Definition Fiber Tractography

Neurosurgery 79:146–165, 2016

Recent studies have demonstrated diffusion tensor imaging tractography of cranial nerves (CNs). Spatial and angular resolution, however, is limited with this modality. A substantial improvement in image resolution can be achieved with high-angle diffusion magnetic resonance imaging and atlas-based fiber tracking to provide detailed trajectories of CNs.

OBJECTIVE: To use high-definition fiber tractography to identify CNs in healthy subjects and patients with brain tumors.

METHODS: Five neurologically healthy adults and 3 patients with brain tumors were scanned with diffusion spectrum imaging that allowed high-angular-resolution fiber tracking. In addition, a 488-subject diffusion magnetic resonance imaging template constructed from the Human Connectome Project data was used to conduct atlas space fiber tracking of CNs.

RESULTS: The cisternal portions of most CNs were tracked and visualized in each healthy subject and in atlas fiber tracking. The entire optic radiation, medial longitudinal fasciculus, spinal trigeminal nucleus/tract, petroclival portion of the abducens nerve, and intrabrainstem portion of the facial nerve from the root exit zone to the adjacent abducens nucleus were identified. This suggested that the high-angularresolution fiber tracking was able to distinguish the facial nerve from the vestibulocochlear nerve complex. The tractography clearly visualized CNs displaced by brain tumors. These tractography findings were confirmed intraoperatively.

CONCLUSION: Using high-angular-resolution fiber tracking and atlas-based fiber tracking, we were able to identify all CNs in unprecedented detail. This implies its potential in localization of CNs during surgical planning.

Posted on

Three-Dimensional Microsurgical Anatomy and the Safe Entry Zones of the Brainstem

Three-Dimensional Microsurgical Anatomy and the Safe Entry Zones of the Brainstem

Operative Neurosurgery 10:602–620, 2014

There have been no studies of the structure and safe surgical entry zones of the brainstem based on fiber dissection studies combined with 3-dimensional (3-D) photography.

OBJECTIVE: To examine the 3-D internal architecture and relationships of the proposed safe entry zones into the midbrain, pons, and medulla.

METHODS: Fifteen formalin and alcohol-fixed human brainstems were dissected by using fiber dissection techniques, ·6 to ·40 magnification, and 3-D photography to define the anatomy and the safe entry zones. The entry zones evaluated were the perioculomotor, lateral mesencephalic sulcus, and supra- and infracollicular areas in the midbrain; the peritrigeminal zone, supra- and infrafacial approaches, acoustic area, and median sulcus above the facial colliculus in the pons; and the anterolateral, postolivary, and dorsal medullary sulci in the medulla.

RESULTS: The safest approach for lesions located below the surface is usually the shortest and most direct route. Previous studies have often focused on surface structures. In this study, the deeper structures that may be at risk in each of the proposed safe entry zones plus the borders of each entry zone were defined. This study includes an examination of the relationships of the cerebellar peduncles, long tracts, intra-axial segments of the cranial nerves, and important nuclei of the brainstem to the proposed safe entry zones.

CONCLUSION: Fiber dissection technique in combination with the 3-D photography is a useful addition to the goal of making entry into the brainstem more accurate and safe.

Proudly powered by WordPress