Objective  While the transcondylar approach is technically challenging, it provides generous ventral and caudal exposure to the craniovertebral junction. This approach requires navigation around multiple eloquent neurovascular structures including the lower cranial nerves, vertebral artery and its branches, and the brainstem. Superficial exposure, including incision location and muscle dissection, can dramatically affect the surgical angle and maneuverability at depth. Methods  We demonstrate the transcondylar approach in a step-by-step fashion in a formalin-embalmed, latex-injected cadaver head. Dissection within each layer of the suboccipital muscles was performed. A small cohort with an illustrative case is also included herein. Results  The sternocleidomastoid (SCM) muscle was retracted anteriorly; the splenium capitis, semispinalis capitis, and longissimus capitis muscles were disconnected from the superior nuchal line and reflected inferomedially. The suboccipital muscle group was fully exposed. The superior and inferior oblique muscles were disconnected from the transverse process of C1. The superior oblique and the rectus capitis posterior major muscles were then dissected off the inferior nuchal line, and the suboccipital muscle group was retracted inferomedially en bloc . The greater auricular nerve was retracted laterally with the SCM, and the greater occipital nerve was retracted inferomedially with the suboccipital muscle group. Conclusion  This technique avoids the obstructive muscle bulk that results from a myocutaneous approach while maximizing deep exposure. Understanding the detailed muscular anatomical relationship with the insertion location and suboccipital nerves is key to complete and safe extracranial dissection. Diligent dissection helps minimize postoperative pain and muscle spasm while optimizing the closure technique.

Primary cranial neurolymphomatosis (PCNL) is a rare subtype of primary CNS lymphoma (PCNSL) in which infiltrative lymphomatous involvement is confined to cranial nerves. Here, we report a case of PCNL with successful genomic profiling. A 57-year-old male had a lengthy prediagnostic phase spanning approximately 30 months, characterized by multiple episodes of cranial neuropathies managed by steroids. At the time of diagnosis, the patient had right-sided cranial neuropathies involving cranial nerves (CN) V, VI, and VII. Pathological findings of the right cavernous lesion biopsy were consistent with large B-cell lymphoma-infiltrating nerve fibers. The clinical course was aggressive and refractory, characterized by relentless progression with the development of cervical spinal neurolymphomatosis, cerebrospinal fluid involvement, and ependymal and intraparenchymal cerebral involvement, despite multiple lines of therapy, including chemoimmunotherapy, Bruton\'s tyrosine kinase inhibitor, radiation, autologous stem cell transplant, chimeric antigen receptor T-cell therapy (CAR-T), and whole-brain radiation. The patient survived for 22 months from the time of the initial diagnosis and 52 months after the first episode of cranial neuropathy. Next-generation sequencing identified mutations (MYD88, CD79b, and PIM1) that are frequently observed in PCNSL. The unusual findings included a total of 22 mutations involving PIM1, indicating a highly active aberrant somatic hypermutation and two missense CXCR4 mutations. CXCR4 mutations have never been described in PCNSL and may have implications for disease biology and therapeutic interventions. We provide a literature review to further elucidate PCNL.

OBJECTIVE: To determine if super-resolution deep learning reconstruction (SR-DLR) improves the depiction of cranial nerves and interobserver agreement when assessing neurovascular conflict in 3D fast asymmetric spin echo (3D FASE) brain MR images, as compared to deep learning reconstruction (DLR).
METHODS: This retrospective study involved reconstructing 3D FASE MR images of the brain for 37 patients using SR-DLR and DLR. Three blinded readers conducted qualitative image analyses, evaluating the degree of neurovascular conflict, structure depiction, sharpness, noise, and diagnostic acceptability. Quantitative analyses included measuring edge rise distance (ERD), edge rise slope (ERS), and full width at half maximum (FWHM) using the signal intensity profile along a linear region of interest across the center of the basilar artery.
RESULTS: Interobserver agreement on the degree of neurovascular conflict of the facial nerve was generally higher with SR-DLR (0.429-0.923) compared to DLR (0.175-0.689). SR-DLR exhibited increased subjective image noise compared to DLR (p ≥ 0.008). However, all three readers found SR-DLR significantly superior in terms of sharpness (p < 0.001); cranial nerve depiction, particularly of facial and acoustic nerves, as well as the osseous spiral lamina (p < 0.001); and diagnostic acceptability (p ≤ 0.002). The FWHM (mm)/ERD (mm)/ERS (mm-1) for SR-DLR and DLR was 3.1-4.3/0.9-1.1/8795.5-10,703.5 and 3.3-4.8/1.4-2.1/5157.9-7705.8, respectively, with SR-DLR\'s image sharpness being significantly superior (p ≤ 0.001).
CONCLUSIONS: SR-DLR enhances image sharpness, leading to improved cranial nerve depiction and a tendency for greater interobserver agreement regarding facial nerve neurovascular conflict.

UNASSIGNED: The cavernous sinus (CS) is a demanding surgical territory, given its deep location and the involvement of multiple neurovascular structures. Subjected to recurrent discussion on the optimal surgical access, the endoscopic transorbital approach has been recently proposed as a feasible route for selected lesions in the lateral CS. Still, for this technique to safely evolve and consolidate, a comprehensive anatomical description of involved cranial nerves, dural ligaments, and arterial relations is needed.
UNASSIGNED: Detailed anatomical description of the CS, the course of III, IV, VI, and V cranial nerves, and C3-C7 segments of the carotid artery, all described from the ventrolateral endoscopic transorbital perspective.
UNASSIGNED: Five embalmed human cadaveric heads (10 sides) were dissected. An endoscopic transorbital approach with lateral orbital rim removal, anterior clinoidectomy, and petrosectomy was performed. The course of the upper cranial nerves was followed from their apparent origin in the brainstem, through the middle fossa or cavernous sinus, and up to their entrance to the orbit. Neuronavigation was used to follow the course of the nerves and to measure their length of surgical exposure.
UNASSIGNED: The transorbital approach allowed us to visualize the lateral wall of the CS, with cranial nerves III, IV, V1-3, and VI. Anterior clinoidectomy and opening of the frontal dura and the oculomotor triangle revealed the complete course of the III nerve, an average of 37 (±2) mm in length. Opening the trigeminal pore and cutting the tentorium permitted to follow the IV nerve from its course around the cerebral peduncle up to the orbit, an average of 54 (±4) mm. Opening the infratrochlear triangle revealed the VI nerve intracavernously and under Gruber\'s ligament, and the extended petrosectomy allowed us to see its cisternal portion (27 ± 6 mm). The trigeminal root was completely visible and so were its three branches (46 ± 2, 34 ± 3, and 31 ± 1 mm, respectively).
UNASSIGNED: Comprehensive anatomic knowledge and extensive surgical expertise are required when addressing the CS. The transorbital corridor exposes most of the cisternal and the complete cavernous course of involved cranial nerves. This anatomical article helps understanding relations of neural, vascular, and dural structures involved in the CS approach, essential to culminating the learning process of transorbital surgery.

BACKGROUND: Trigeminal schwannomas (TSs) are intracranial tumors that can cause significant brainstem compression. TS resection can be challenging because of the risk of new neurologic and cranial nerve deficits, especially with large (≥ 3 cm) or giant (≥ 4 cm) TSs. As prior surgical series include TSs of all sizes, we herein present our clinical experience treating large and giant TSs via microsurgical resection.
METHODS: This was a retrospective, single-surgeon case series of adult patients with large or giant TSs treated with microsurgery in 2012-2023.
RESULTS: Seven patients underwent microsurgical resection for TSs (1 large, 6 giant; 4 males; mean age 39 ± 14 years). Tumors were classified as type M (middle fossa in the interdural space; 1 case, 14%), type ME (middle fossa with extracranial extension; 3 cases, 43%), type MP (middle and posterior fossae; 2 cases, 29%), or type MPE (middle/posterior fossae and extracranial space; 1 case, 14%). Six patients were treated with a frontotemporal approach (combined with transmastoid craniotomy in the same sitting in one patient and a delayed transmaxillary approach in another), and one patient was treated using an orbitofrontotemporal approach. Gross total resection was achieved in 5 cases (2 near-total resections). Five patients had preoperative facial numbness, and 6 had immediate postoperative facial numbness, including two with worsened or new symptoms. Two patients (28%) demonstrated new non-trigeminal cranial nerve deficits over mean follow-up of 22 months. Overall, 80% of patients with preoperative facial numbness and 83% with facial numbness at any point experienced improvement or resolution during their postoperative course. All patients with preoperative or new postoperative non-trigeminal tumor-related cranial nerve deficits (4/4) experienced improvement or resolution on follow-up. One patient experienced tumor recurrence that has been managed conservatively.
CONCLUSIONS: Microsurgical resection of large or giant TSs can be performed with low morbidity and excellent long-term cranial nerve function.

OBJECTIVE: The objective of this study was to describe the quantitative features of intraoperative electromyographic recordings obtained from cranial nerve III, IV, and VI neuromonitoring using 25-mm intraorbital electrodes, in the larger context of demonstrating the practicality of this technique during neurosurgical cases.
METHODS: A 25-mm-long shaft-insulated intraorbital needle electrode is routinely used at the authors\' institution for extraocular muscle (EOM) electromyographic monitoring of the inferior rectus, superior oblique, and/or lateral rectus muscles when their function is at risk. Cases monitored between January 1, 2021, and December 31, 2022, were reviewed for patient demographics, tumor location and pathology, EOMs monitored, pre- and postoperative examination, and complications from electrode placement. Compound muscle action potentials on triggered electromyography, as well as neurotonic discharges on free-run electromyography, were described quantitatively.
RESULTS: There were 141 cases in 139 patients reviewed during the 24-month time span, with 278 EOMs monitored (inferior rectus/superior oblique/lateral rectus muscles 68/68/142). Triggered electromyography yielded biphasic or triphasic compound muscle action potentials from EOMs with a mean onset latency of 1.51 msec (range 0.94-3.22 msec), mean maximal peak-to-trough amplitude of 1073.93 μV (range 76.75-7796.29 μV), and high specificity for the channel in nearly all cases. Neurotonic discharges were recorded in 30 of the 278 EOMs (with all 3 muscles represented) and associated with a greater incidence of new or worsened ophthalmoparesis (OR 4.62, 95% CI 1.3-16.4). There were 2 cases of small periorbital ecchymosis attributed to needle placement; additionally, 1 case of needle-related intraorbital hematoma occurred after the review period.
CONCLUSIONS: The 25-mm shaft-insulated intraorbital electrode facilitates robust and consistent electromyographic recordings of EOMs that are advantageous over existing techniques. Combined with the relative ease of needle placement and low rate of complications, the technique is practical for neuromonitoring during craniotomies.

BACKGROUND: Brainstem mapping with electrical stimulation allows functional identification of neural structures during resection of deep lesions. Single pulses or train of pulses are delivered to map cranial nerves and corticospinal tracts, respectively.
METHODS: We introduce a hybrid stimulation technique for mapping the brainstem. The stimulus consists of an electrical single pulse followed by a short train of 3-5 pulses at 500 Hz, at an interval of 60-75 ms. The responses to this stimulation pattern are recorded from appropriate cranial and limb muscles.
RESULTS: Both the single pulse and the short train elicit electromyographic responses when motor fibers or motor nuclei of the cranial nerves are stimulated. Responses to the train but not to the preceding single pulse indicate activation of the descending motor tracts, in the mesencephalon and the pons. Conversely, in the medulla, limb responses to stimulation of the corticospinal tracts are elicited by a single pulse. Identification of the extra and intra-axial courses of the trigeminal motor and sensory fibers is possible by recording responses from the masseter and the tongue muscles.
CONCLUSIONS: To date, either a pulse or a train is delivered during brainstem mapping, switching from one to the other modality according to the expected target structure. This procedure can be time-consuming and may even lead to false negative responses to the stimulation, eventually leading to inaccurate neurosurgical procedures.
CONCLUSIONS: The novel hybrid pulse-train technique enhances the advantage of brainstem mapping procedure, minimizing pitfalls and improving patient safety.

BACKGROUND: Neurosarcoidosis is rare, and among its manifestations, nerve root involvement has been reported in only a few cases. Therefore, magnetic resonance imaging (MRI) findings of neurosarcoidosis, particularly those involving nerve roots, are scarce in the literature.
METHODS: We presented the case of neurosarcoidosis involving cervical nerve roots and cranial nerves, alongside a systematic literature review.
RESULTS: A 28-year-old female suddenly developed right facial numbness as well as left upper extremity and left hand pain. Initial brain and spine MRI showed a bulging mass of T2 iso-to-high signal intensity in the left Meckel\'s cave/trigeminal nerve, as well as diffuse enlargement of the right C6 and C7 nerve roots. Follow-up MRI at 2 months revealed a reduction in the size of the initial lesion and the appearance of new similar lesions on the contralateral side (right Meckel\'s cave, left C3-C8 nerve roots). In particular, the lesions involving the nerve roots demonstrated central enlargement along the nerve roots, without involvement of the adjacent spinal cord. All these lesions exhibited enhancement, leading to the differentiation between sarcoidosis and lymphoma. Sarcoidosis was subsequently confirmed through biopsy of a hilar lymph node.
CONCLUSIONS: This report presents a distinctive MRI feature of neurosarcoidosis involving spinal nerve roots, representing the first of its kind, and describes the evolution of MRI findings throughout the clinical course.

BACKGROUND: Cavernous malformations (CMs) are clusters of thin-walled sinusoidal vessels without well-defined walls. Though they can occur anywhere in the neuroaxis, cranial nerve (CN) CMs are rare.
METHODS: We report a 47-year-old male with gradual CN III palsy. Initial imaging showed no significant findings, but a follow-up MRI revealed a growing lesion along CN III. Intraoperative findings confirmed a CN III CM. Diagnosing and treating CN III CM are complex. Radiological findings lack specificity, requiring consideration of various diagnoses for patients with isolated CN III palsy and abnormal radiological findings.
CONCLUSIONS: Surgery is the gold standard, aiming for complete lesion removal while minimizing neurological complications.

Communications between cranial nerves or their branches have been described previously. The exact functional significance of some of these neural communications remains to be fully understood. This paper reports a unique communication between the auriculotemporal and inferior alveolar nerves within the infratemporal fossa. The histological examination indicates an antegrade connection from the inferior alveolar nerve to the auriculotemporal nerve, which could potentially be implicated in referred pain from the anatomical territory of one nerve to the other.