Lumbar Spinous Process-Splitting Technique for Ligamentum Flavum Cyst Removal.

BACKGROUND: Laminotomy for lumbar stenosis is a well-defined procedure and represents a routine in every neurosurgical department. It is a common experience that the uni- or bilateral paraspinal muscle detachment, together with injury of the supra- and interspinous ligaments, can lead to postoperative pain. In the literature, the application of a minimally invasive technique, the lumbar spinous process-splitting (LSPS) technique, has been reported. METHODS: In this study, we present a case series of 12 patients who underwent LSPS from September 2019 to April 2020. Two patients had a cyst of the ligamentum flavum, eight a single-level lumbar canal stenosis (LCS), and two a two-level LCS. Moreover, we propose a novel morphological classification of postoperative muscle atrophy and present volumetric analysis of the decompression achieved. RESULTS: There were no complications related to this technique. In all patients, the vertebral canal area was more than doubled by the procedure. The muscle sparing showed grade A, according to our classification. CONCLUSION: To our knowledge, this is the first description of this surgical technique and the first LSPSL case series in Europe. Furthermore, cases of ligamentum flavum cyst removal using this safe and effective technique have not yet been reported.

Use of BoneScalpel Ultrasonic Bone Dissector in Anterior Clinoidectomy and Posterior Fossa Surgery: Technical Note.

BackgroundFirst popularized by Dolenc, anterior clinoidectomies were performed with rongeurs, before the adoption of modern high-speed drills. We describe a novel application of the piezoelectric BoneScalpel™ in anterior skull base and posterior fossa surgeries. In the literature, to date, there are no mentions of anterior clinoidectomies performed with piezosurgical devices.MethodsWe reported a total of 12 patients, 8 affected by posterior fossa tumors and 4 treated for anterior skull base oncologic and vascular pathologies. This study aims to assess the safety and efficacy of the piezoelectric osteotomy in skull base and posterior fossa surgeries. In all patients, an ultrasonic bone dissector (BoneScalpel™ - Misonix) was used to perform the anterior clinoidectomy (AC) and craniotomy.ResultsA successful clinoidectomy was performed in 4 out of 12 patients (33.3%). We did not notice any heat damage to the surrounding soft tissue in critical areas such as paraclinoid structures. We documented only one durotomy in an oncologic patient, while no lesions of SSS or TS were detected.We recorded only a slightly increased surgery duration in the PIEZOSURGERY® and BoneScalpel™ group, compared to standard surgery with an osteotome to perform craniotomies, but no time difference in performing the clinoidectomy between BoneScalpel™ and a conventional high-speed drill.ConclusionWe report the first experience with piezosurgery for anterior clinoidectomy. There is no time difference in performing the clinoidectomy between BoneScalpel™ and a conventional high-speed drill, and this is an undoubted advantage in critical contexts such as clinoid-paraclinoid surgeries, where the risk of dural sinuses tears is common.

Vertebrobasilar Dolichoectasia, Hypoplastic Third Ventricle, and Related Biventricular Hydrocephalus: Case Report and Review of the Literature.

BACKGROUND: Vertebrobasilar dolichoectasia (VBDE) is defined as a symptomatic dilatation and tortuosity of the vertebrobasilar arteries. The risk of hydrocephalus development is due to direct compression of the third ventricle outflow or brainstem compression and related aqueduct stenosis. We present an uncommon case of a patient with symptomatic VBDE with the uniqueness of a hypoplastic third ventricle associated with biventricular hydrocephalus. A literature review concerning diagnosis and management of patients affected by biventricular hydrocephalus caused by VBDE was also performed. CASE ILLUSTRATION: We report a case of a 54-year-old man who presented with headache, ideomotor apraxia, and gait disorder. A head computed tomography (CT) scan showed a biventricular hydrocephalus and a subsequent CT angiography documented the presence of a VBDE compressing the anterior part of the third ventricle that also appeared hypoplastic. The patient also presented a clinical history of arterial hypertension for which he was given a proper pharmacologic treatment with symptom relief. A surgical treatment of ventriculoperitoneal shunt along with endoscopic septostomy was proposed, but the patient refused, probably due to the slightly positive response to medical treatment. CONCLUSIONS: The natural clinical history of patients affected by VBDE is unfavorable with 7.8 years of median survival. The therapeutic strategy is usually conservative and the role of antiplatelets or oral anticoagulants is still debated. In selected patients, ventriculoperitoneal shunt to resolve intracranial hypertension caused by biventricular hydrocephalus is the most effective treatment. In our opinion, chronic third ventricle compression could lead to anatomic-pathologic alterations like the third ventricle hypoplasia documented in our report.

Narcolepsy-A Neuropathological Obscure Sleep Disorder: A Narrative Review of Current Literature.

Narcolepsy is a chronic, long-term neurological disorder characterized by a decreased ability to regulate sleep-wake cycles. Some clinical symptoms enter into differential diagnosis with other neurological diseases. Excessive daytime sleepiness and brief involuntary sleep episodes are the main clinical symptoms. The majority of people with narcolepsy experience cataplexy, which is a loss of muscle tone. Many people experience neurological complications such as sleep cycle disruption, hallucinations or sleep paralysis. Because of the associated neurological conditions, the exact pathophysiology of narcolepsy is unknown. The differential diagnosis is essential because relatively clinical symptoms of narcolepsy are easy to diagnose when all symptoms are present, but it becomes much more complicated when sleep attacks are isolated and cataplexy is episodic or absent. Treatment is tailored to the patient's symptoms and clinical diagnosis. To facilitate the diagnosis and treatment of sleep disorders and to better understand the neuropathological mechanisms of this sleep disorder, this review summarizes current knowledge on narcolepsy, in particular, genetic and non-genetic associations of narcolepsy, the pathophysiology up to the inflammatory response, the neuromorphological hallmarks of narcolepsy, and possible links with other diseases, such as diabetes, ischemic stroke and Alzheimer's disease. This review also reports all of the most recent updated research and therapeutic advances in narcolepsy. There have been significant advances in highlighting the pathogenesis of narcolepsy, with substantial evidence for an autoimmune response against hypocretin neurons; however, there are some gaps that need to be filled. To treat narcolepsy, more research should be focused on identifying molecular targets and novel autoantigens. In addition to therapeutic advances, standardized criteria for narcolepsy and diagnostic measures are widely accepted, but they may be reviewed and updated in the future with comprehension. Tailored treatment to the patient's symptoms and clinical diagnosis and future treatment modalities with hypocretin agonists, GABA agonists, histamine receptor antagonists and immunomodulatory drugs should be aimed at addressing the underlying cause of narcolepsy.

Optic Tract as an Upper Limit in Amygdalectomy: Microsurgical Study.

BACKGROUND: In surgeries involving resection of the amygdala, despite clear relations established with the medial, lateral, anterior, posterior, and inferior segments, the upper limit remains controversial. The optic tract (OT) has been anatomically considered as a good landmark immediately inferior to the striatopallidal region. This anatomic structure has barely been explored by microsurgical study, generating uncertainty about the exact relationship with the surrounding structures. OBJECTIVE: To describe the OT in its entire length through microsurgical study, showing its superior, inferior, medial, and lateral relationships and highlighting its value as a landmark in superior amygdala resection. METHODS: Microsurgical anatomic dissection of the OT, from its origin in the chiasm to the lateral geniculate nucleus was performed in 8 alcohol-fixed human hemispheres, showing its different segments and relations. Photographs were taken from different angles to facilitate surgical orientation. RESULTS: We performed a dissection of the OT, showing its position relative to caudate and hippocampal formations. We exposed the structures related to the OT superiorly (striatopallidal region and superior caudate fasciculus), inferiorly (head of the hippocampus, amygdala, anterior choroidal artery, perforating artery branch of the anterior choroidal artery, terminal stria, and basal vein), medially (internal capsule and midbrain), and laterally (temporal stem [uncinate and inferior fronto-occipital fascicle], anterior perforated substance, and superior caudate fasciculus). CONCLUSION: To date, there is a paucity of articles describing the anatomy of the OT from a neurosurgery perspective. In this study, we describe the microsurgical anatomic path of the OT, as a reliable upper limit landmark for amygdala resection.

Diamond-Shaped Mini-Craniotomy: A New Concept in Neurosurgery.

BACKGROUND: We describe, step by step, a modified, less invasive, diamond-shaped mini-craniotomy that optimizes dural opening and can be performed in elderly patients affected by acute subdural or intracerebral hematomas, in therapy with antiplatelets or anticoagulants. METHODS: We retrospectively analyzed the clinical records of 67 patients (mean age of 78.5 years) treated in our institution, during a period of 10 years, with this novel diamond-shaped craniotomy. Seventeen patients were treated for intracerebral hemorrhage and 50 patients for acute subdural hematomas. All the patients were in therapy with antiplatelets or anticoagulants. RESULTS: Approach-related complications were not detected. Ten of 67 patients (14.9%) presented temporal muscle atrophy; there was no scar deformity, paresthesia, hyperalgesia, or ramus frontalis palsy around the scalp incision. Thirty-day mortality was 22%. The mean follow-up was 1.3 years. One-month postoperative brain computed tomography scans showed a satisfactory hematoma evacuation in 57 of 67 patients (85%). CONCLUSIONS: The diamond-shaped mini-craniotomy for acute subdural and intracerebral hematomas is safe and effective, and it should be considered as an alternative to traditional approaches, particularly in elderly patients.

Use of Gelatin-thrombin Hemostatic Matrix for Control of Ruptured Cerebral Aneurysm.

BACKGROUND: The use of thrombin-based hemostatic agents (TBHAs) has become common practice in most neurosurgical procedures, both cranial and spinal. METHODS: We present the case of a 40-year-old woman who was referred to our institution with intense headache and Fisher grade 3 subarachnoid hemorrhage (SAH) mainly at the level of the right sylvian fissure, caused by a 5.71-mm right middle cerebral artery (MCA) bifurcation aneurysm, with hourglass morphology and a bleb on the bottom. Cerebral angiography demonstrated aneurysm enlargement, compared with the prior angiographic computerized tomography scan. RESULTS: A right pterional craniotomy was performed. After initial arachnoid dissection to get proximal vascular control, but before we obtained it, we witnessed profuse bleeding from the aneurysm. Floseal, a gelatin-thrombin matrix sealant, was sprayed over the breach of the aneurysm, and cottonoids were gently pressed with a self-retaining spatula, stopping the hemorrhage. After that, we obtained proximal control with an extradural clinoidectomy and temporary clipping of the right internal carotid artery (ICA) and MCA. Finally, aneurysm dissection and final clipping were performed with the application of two clips. The postoperative course was uneventful, and the patient was discharged on postoperative day 10. CONCLUSION: Intraoperative aneurysm rupture (IAR) is a dangerous event that carries great risks-even death. Proper use of TBHAs is a useful and safe way to stop the bleeding, take a deep breath, and achieve proximal vascular control. To the best of our knowledge, this is the first report of the use of TBHA during aneurysm clipping.

Largest neurosurgical social media group and its impact on communication and research.

BACKGROUND: The use of social media to communicate and disseminate knowledge has increased exponentially, especially in the field of neurosurgery. 'Neurosurgery cocktail' (NC) was developed by a group of young neurosurgeons as a means of sharing didactic materials and clinical experiences via social media. It connects 35.000 neurosurgeons worldwide on multiple platforms, primarily Facebook and Twitter. Given the rising utilization of social media in neurosurgery, the popularity of NC has also increased since its inception. In this study, the authors surveyed the social media analytics of NC for both Facebook and Twitter. Besides, we reviewed the literature on the use of social media in neurosurgery. METHODS: Facebook and Twitter metrics were extracted through each respective platform's analytics tools from December 2020 (earliest available date for data analysis) through January 2021. A literature search was conducted using PubMed (MEDLINE) and Scopus databases. RESULTS: On Facebook, as of January 2021, the group had a total of 25.590 members (87.6% male), most commonly (29%) between 35 and 44 years of age with over 100 countries were represented. As of January 2021, they had amassed 6457 followers on Twitter. During the last 28 d between December 2020 and January 2021, the account published 65 tweets that garnered a total of 196,900 impressions. Twelve articles were identified in our literature review on the use of social media within the neurosurgical community. CONCLUSIONS: NC is one of the most widely utilized neurosurgical social media resources available. Sharing knowledge has been broadened thanks to the recent social media evolution, and NC has become a leading player in disseminating neurosurgical knowledge.

A Review of Remote Intracerebral Hemorrhage after Chronic Subdural Hematoma Evacuation.

BACKGROUND: Remote intracerebral hemorrhage (RICH) is a severe complication following chronic subdural hematoma (cSDH) drainage, and only case reports and small case series have been reported to date. The authors present an emblematic patient affected by RICH following cSDH drainage. A systematic review of the literature on diagnosis and management of patients affected by RICH following cSDH evacuation has also been performed. METHODS: A literature search according to the PRISMA statement was conducted using PubMed and Scopus databases with the following Mesh terms: [(remote) AND (intracerebral hemorrhage or cerebral hematoma or cerebral infarction or cerebellar hemorrhage or cerebellar hematoma or cerebellar infarction) AND (chronic subdural hematoma)]. RESULTS: The literature search yielded 35 results, and 25 articles met our inclusion criteria: 22 articles were case reports and 3 were case series including three to six patients. Overall, 37 patients were included in the study. Age was reported in all 37 patients, 26 males (70.3%) and 11 females (29.7%), with a male-to-female ratio of 2.4:1. The mean age at diagnosis was 64.6 years (range: 0.25-86 years). Only in 5 cases (13.5%) did the ICH occur contralaterally to the previously drained cSDH. The rapidity of drainage can lead to several types of intracranial hemorrhages, caused by a too rapid change in the cerebral blood flow (CBF) and/or tears of bridging veins. The average time interval between cSDH drainage and neurologic deterioration was 71.05 hours (range: 0-192 hours). CONCLUSIONS: RICH following cSDH represents a rare occurrence and a serious complication, associated with elevated morbidity. Careful monitoring of drain speed after cSDH evacuation surgery is recommended, and minimally invasive techniques such as twist drill craniostomy are suggested, especially for massive cSDHs.

Thoracic Spinal Angiolipomas: A Systematic Review.

BACKGROUND: Spinal angiolipomas (SAs) are rare, benign tumors, representing 0.0004 to 1.2% of angiolipomas, usually located at the extradural and posterior thoracic level, with multimetameric extension. METHODS: A systematic literature review was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement. The authors searched on PubMed and Scopus databases for published articles with the Mesh term "spinal angiolipoma" and pertinent associations. Language restriction to English papers was applied. The authors also reported three emblematic cases of patients who underwent surgical resection of spindle-shaped (type IA) and dumbbell-shaped (type II) SAs between 2014 and 2020. RESULTS: Of the 256 retrieved articles, 33 were included in the meta-analysis. These 33 studies, together with our 3 reported cases, included a total of 60 patients, 36 females (60%) and 24 males (40%), with a mean age of 53.12 ± 12.82 years (range: 12-77 years).T5 was the most represented level (22 patients). Usually, the localization of SA was extradural, with 53 patients suffering from spindle-shaped type IA SA (88.3%) and 7 patients from dumbbell-shaped type II SA (11.6%). Almost all patients underwent laminectomy (78.3%) and presented a full recovery of motor deficits (85%). Gross total removal (GTR) was performed in 93.3% of patients. The mean follow-up was of 22.71 ± 21.45 months (range: 2-80 months). There was no documented recurrence at follow-up magnetic resonance imaging in any of the patients. CONCLUSIONS: SAs are rare, benign tumors with a great vascular component that presents a favorable outcome. GTR is the gold standard treatment and usually an adjuvant therapy is not required. Even infiltrative lesions, which are more complex, can be treated successfully with a good prognosis. Dumbbell-shaped SAs must be differentiated from schwannomas and meningiomas, and require different surgical techniques, given the profuse bleeding associated with the attempt of debulking. En block resection is the key to treat these common benign tumors with acceptable blood loss.

Primary Extracranial Meningiomas of the Head and Neck.

Meningiomas represent the most common benign histological tumor of the central nervous system. Usually, meningiomas are intracranial, showing a typical dural tail sign on brain MRI with Gadolinium, but occasionally they can infiltrate the skull or be sited extracranially. We present a systematic review of the literature on extracranial meningiomas of the head and neck, along with an emblematic case of primary extracranial meningioma (PEM), which provides further insights into PEM management. A literature search according to the PRISMA statement was conducted from 1979 to June 2021 using PubMed, Web of Science, Google Scholar, and Scopus databases, searching for relevant Mesh terms (primary extracranial meningioma) AND (head OR neck). Data for all patients were recorded when available, including age, sex, localization, histological grading, treatment, possible recurrence, and outcome. A total of 83 published studies were identified through PubMed, Google Scholar, and Scopus databases, together with additional references list searches from 1979 to date. A total of 49 papers were excluded, and 34 manuscripts were considered for this systematic review, including 213 patients. We also reported a case of a 45-year-old male with an extracranial neck psammomatous meningioma with sizes of 4 cm × 3 cm × 2 cm. Furthermore, whole-body 68Ga-DOTATOC PET/CT was performed, excluding tumor spread to other areas. Surgical resection of the tumor was accomplished, as well as skin flap reconstruction, obtaining radical removal and satisfying wound healing. PEMs could suggest an infiltrative and aggressive behavior, which has never found a histopathological correlation with a malignancy (low Ki-67, <5%). Whole-body 68Ga-DOTATOC PET/CT should be considered in the patient's global assessment. Surgical removal is a resolutive treatment, and the examination of frozen sections can confirm the benignity of the lesion, reducing the extension of the removal of healthy tissue surrounding the tumor.

Acrometastases to the Hand: A Systematic Review.

Background and Objectives: The term acrometastases (AM) refers to secondary lesions sited distally to the elbow and knee, representing 0.1% of all bony metastases. By frequency, pulmonary cancer and gastrointestinal and genitourinary tract neoplasms are the most responsible for the reported AM. Improvements in oncologic patient care favor an increase in the incidence of such rare cases. We performed a systematic review of acrometastases to the hand to provide further insight into the management of these fragile patients. We also present a peculiar case of simultaneous acrometastasis to the ring finger and pathological vertebral fracture. Material and Methods: A literature search according to the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) statement was conducted using the PubMed, Google Scholar, and Scopus databases in December 2020 on metastasis to the hand and wrist, from 1986 to 2020. MeSH terms included acrometastasis, carpal metastasis, hand metastasis, finger metastasis, phalangeal metastasis, and wrist metastasis. Results: In total, 215 studies reporting the follow-up of 247 patients were analyzed, with a median age of 62 years (range 10-91 years). Overall, 162 out of 247 patients were males (65.6%) and 85 were females (34.4%). The median reported follow-up was 5 months (range 0.5-39). The median time from primary tumor diagnosis to acrometastasis was 24 months (range 0.7-156). Acrometastases were located at the finger/phalanx (68.4%), carpal (14.2%), metacarpal (14.2%), or other sites (3.2%). The primary tumors were pulmonary in 91 patients (36.8%). The average interval from primary tumor diagnosis to acrometastasis varied according to the primary tumor type from 2 months (in patients with mesenchymal tumors) to 64.0 months (in patients with breast cancer). Conclusions: Acrometastases usually develop in the late stage of oncologic disease and are associated with short life expectancy. Their occurrence can no longer be considered rare; physicians should thus be updated on their surgical management and their impact on prognosis and survival.

Perforating Arteries of the Lemniscal Trigone: A Microsurgical Neuroanatomic Description.

Background: The perforating arteries in the dorsolateral zone of the midbrain play a crucial role in the functions of the brain stem. Their damage due to herniation, pathological lesions, or surgery, favored by the narrow tentorial incisura, can lead to hemorrhages or ischemia and subsequently to severe consequences for the patient. Objective: In literature, not much attention has been directed to the perforating arteries in the lemniscus; in fact, no reports on the perforators of this anatomical region are available. The present study aims to a detailed analysis of the microanatomy and the clinical implications of these perforators, in relation to the parent vessels. We focused on the small vessels that penetrate the midbrain's dorsolateral surface, known as lemniscal trigone, to understand better their microanatomy and their functional importance in the clinical practice during the microsurgical approach to this area. Methods: Eighty-seven alcohol-fixed cadaveric hemispheres (44 brains) without any pathological lesions provided the material for studying the perforating vessels and their origin around the dorsolateral midbrain using an operating microscope (OPMI 1 FC, Zeiss). Measurements of the perforators' distances, in relation to the parent vessels, were taken using a digital caliper. Results: An origin from the SCA could be found in 70.11% (61) and from the PCA in 27.58% (24) of the hemispheres. In one hemisphere, an origin from the posterior choroidal artery was found (4.54%). No perforating branches were discovered in 8.04% of specimens (7). Conclusion: The perforating arteries of the lemniscal trigone stem not only from the superior cerebellar artery (SCA), as described in the few studies available in literature, but also from the posterior cerebral artery (PCA). Therefore, special attention should be paid during surgery to spare those vessels and associated perforators. A comprehensive understanding of the lemniscal trigone's perforating arteries is vital to avoid infarction of the brainstem when treating midbrain tumors or vascular malformations.

Roy-Camille Type 3 suicidal jumper's fractures: Case series and review of the literature.

BACKGROUND: Roy-Camille reported only three patients in their Type 3 posttraumatic transverse sacral fracture (TSF) classification. A modified Roy-Camille classification has been already proposed by other authors suggesting further categorization of the TSFs as partially displaced or completely displaced to predict the rate of neurological recovery following lumbopelvic fixation. MATERIALS AND METHODS: We reported three adult cases of surgical fixation of fracture-dislocation (3A and 3B) of the sacrum due to traumatic injuries and submitted to lumbopelvic posterior reconstruction. A case of a 15-year-old male patient affected by Type 3C with vascular pelvic injury was also reported. A comprehensive literature search was performed on evaluation and management of Type 3 TSFs. RESULTS: In Type 3A, there is a minimal anterior dislocation and the reduction is feasible with good chance of recovery. In Type 3B, the anterior dislocation is severe, neurological deficits are present, reduction is difficult, and there is a risk of vascular injury both at the trauma and during the surgical reduction. In Type 3C, the anterior dislocation is massive, and the risk of vascular injury is very high requiring prompt vascular or endovascular treatment. Open reduction and posterior instrumentation are technically feasible in patients affected by Type 3 high TSFs. CONCLUSIONS: In our opinion, a modified Roy-Camille classification could be useful in the assessment of prognostic and therapeutic aspects of such fractures, In our opinion, a modified Roy-Camille classification could help assess the prognostic and therapeutic aspects of such fractures, in which the severity of the dislocation affects the surgical technique, the chance of neurological recovery, and the patient's life expectancy.

Multimodal Simulation of a Novel Device for a Safe and Effective External Ventricular Drain Placement.

BACKGROUND: External ventricular drain (EVD) placement is mandatory for several pathologies. The misplacement rate of the EVD varies widely in literature, ranging from 12.3 to 60%. The purpose of this simulation study is to provide preliminary data about the possibility of increasing the safety of one of the most common life-saving procedures in neurosurgery by testing a new device for EVD placement. METHODS: We used a novel guide for positioning the ventricular catheter (patent RM2014A000376). The trajectory was assessed using 25 anonymized head CT scans. The data sets were used to conduct three-dimensional computer-based and combined navigation and augmented reality-based simulations using plaster models. The data set inclusion criteria were volumetric head CT scan, without midline shift, of patients older than 18. Evans' index was used to quantify the ventricle's size. We excluded patients with slit ventricles, midline shift, skull fractures, or complex skull malformations. The proximal end of the device was tested on the cadaver. RESULTS: The cadaveric tests proved that a surgeon could use the device without any external help. The multimodal simulation showed Kakarla grade 1 in all cases but one (grade 2) on both sides, after right and left EVD placement. The mean Evans' index was 0.28. The geometric principles that explain the device's efficacy can be summarized by studying the properties of circumference and chord. The contact occurs, for each section considered, at the extreme points of the chord. Its axis, perpendicular to the plane tangent to the spherical surface at the entry point, corresponds to the direction of entry of the catheter guided by the instrument. CONCLUSION: According to our multimodal simulation on cadavers, 3D computer-based simulation, 3D plaster modeling, 3D neuronavigation, and augmented reality, the device promises to offer safer and effective EVD placement. Further validation in future clinical studies is recommended.

Corrigendum: Perforating Arteries of the Lemniscal Trigone: A Microsurgical Neuroanatomic Description.

[This corrects the article DOI: 10.3389/fnana.2021.675313.].

Comparative analysis of surgical exposure and freedom between the subtonsillar, endoscope-assisted subtonsillar, and far-lateral approaches to the lower clivus: A cadaveric study.

The far-lateral (FL)approach is a classic technique for skull base surgeries involving the lower clivus (LC).Recently, a modified suboccipital midline approach known as the subtonsillar (ST) approach, along with the endoscope-assisted subtonsillar (EST) approach, has been described as a minimally invasive technique to treat LC lesions. However, there is no quantitative study on comparing these approaches together for reaching LC. We aimed to compare surgical exposure and freedom provided by ST, EST, and FL approaches for various targets at LC. These approaches were performed on each side of five cadaveric specimens (total 10 sides), and relevant parameters were quantified and compared using a repeated measures ANOVA test. FL approach yielded the greatest surgical area (237.8 ± 56.0 mm2) and exposure, including lengths of glossopharyngeal nerve (16.2 ± 1.9 mm), hypoglossal nerve (11.4 ± 2.4 mm), vertebral artery (23.9 ± 3.3 mm), followed by EST and ST approaches. For surgical freedom, FL approach provided the greatest angle of attack (90.0 ± 14.0° at jugular foramen, 95.1 ± 15.8° at hypoglossal canal, 83.4 ± 31.4° at bifurcation point of posterior inferior cerebellar artery and vertebral artery). Our systematic comparison suggests that EST approach, compared to ST approach, can significantly increase surgical exposure to the medial side of LC, but FL approach still provides the greatest surgical exposure and freedom at LC. Despite the limitations of a cadaveric study, our quantitative data can update the literature on currently available surgical techniques for reaching LC and better inform preoperative planning in this area. Further studies should be performed to evaluate these approaches in clinical practice.