Cervicomedullary Junction Research Articles

TMIC-17. TARGETING THE FLUIDIC FORCE-SENSING MECHANISM TO TREAT BRAIN TUMOR METASTASIS

Abstract Biofluid flow generates fluid shear stress (FSS), a mechanical force widely present in tissue microenvironment. How brain tumor growth alters the conduit of biofluid, thereby impacting FSS-regulated cancer progression is unknown. Medulloblastoma (MB) is the most common malignant brain tumor in children. Dissemination of MB cells into the cerebrospinal fluid (CSF) initiates metastasis within the central nervous system. By simulating CSF dynamics based on magnetic resonance imaging of MB patients, we discovered that FSS is elevated at the cervicomedullary junction. Strikingly, we found that MB-relevant FSS promotes metastasis along mouse spinal cords. Mechanistically, FSS induces metastatic cell behaviours, including weakened cell-substrate adhesion, increased motility, cell clustering, and plasma membrane localization of glucose transporter 1 (GLUT1) to enhance glucose uptake. FSS is perceived by mechanosensitive ion channel PIEZO2, which drives actomyosin contractility-dependent GLUT1 recruitment at the plasma membrane. Genetic targeting of PIEZO2 or pharmacologic inhibition of GLUT1 mitigates metastasis. Collectively, these findings define a targetable FSS-activated mechano-metastatic cascade for the treatment of MB metastasis.

Transoral Approach for Ruptured Anterior Spinal Artery Aneurysm at the Cervicomedullary Junction: 2-Dimensional Operative Video.

Transoral Approach for Ruptured Anterior Spinal Artery Aneurysm at the Cervicomedullary Junction: 2-Dimensional Operative Video.

C1-2 hypermobility and its impact on the spinal cord: a finite element analysis.

The authors present a finite element analysis (FEA) evaluating the mechanical impact of C1-2 hypermobility on the spinal cord. The Code_Aster program was used to perform an FEA to determine the mechanical impact of C1-2 hypermobility on the spinal cord. Normative values of Young's modulus were applied to the various components of the model, including bone, ligaments, and gray and white matter. Two models were created: 25° and 50° of C1-on-C2 rotation, and 2.5 and 5 mm of C1-on-C2 lateral translation. Maximum von Mises stress (VMS) throughout the cervicomedullary junction was calculated and analyzed. The FEA model of 2.5 mm lateral translation of C1 on C2 revealed maximum VMS for gray and white matter of 0.041 and 0.097 MPa, respectively. In the 5-mm translation model, the maximum VMS for gray and white matter was 0.069 and 0.162 MPa. The FEA model of 25° of C1-on-C2 rotation revealed maximum VMS for gray and white matter of 0.052 and 0.123 MPa. In the 50° rotation model, the maximum VMS for gray and white matter was 0.113 and 0.264 MPa. This FEA revealed significant spinal cord stress during pathological rotation (50°) and lateral translation (5 mm) consistent with values found during severe spinal cord compression and in patients with myelopathy. While this finite element model requires oversimplification of the atlantoaxial joint, the study provides biomechanical evidence that hypermobility within the C1-2 joint leads to pathological spinal cord stress.

Reliability and Predictors of Intraoperative Neuromonitoring Changes During Intramedullary Tumor Resection: A Multicenter Experience

INTRODUCTION: Intraoperative neuromonitoring (IONM) is used in real-time to alert neurosurgeons of potential neurological changes when resecting intramedullary spinal cord tumors (IMSCTs). Previous studies have reported variable reliability of IONM. METHODS: A multicenter retrospective study was performed on patients undergoing IMSCTs surgery with neuromonitoring at the three Mayo Clinic sites between 2005 to 2022. Demographics, SSEP, MEP changes and postoperative outcomes were recorded. Specificity, sensitivity, positive predictive value (PPV), and negative predictive value (NPV) were calculated. Variables found significant on univariate analysis (p < 0.05) were applied to a multivariate model to identify predictors for IONM SSEP and MEP changes. RESULTS: 135 patients underwent surgical resection for IMSCTs using IONM. The mean age at diagnosis was 45 ± 17.9 years. Laminectomy was the most frequent index operation (96.3%). A total of 8.9% of patients presented with short-term improvement, while 70.4% presented long-term improvement on their baseline McCormick Scale. Sensitivity, specificity, PPV, NPV, accounted for 86.2%, 51%, 5.2%, 99.2% for MEP; 77.8%, 48.2%, 4.4%, 98.6% for SSEP. We found predictors of IONM changes: poorly defined MEP baseline (OR 3.004, 95% CI 1.22-7.397, p = 0.017), WHO grade II tumors (OR 2.334, 95% CI 1.043-5.223, p = 0.039), cervicomedullary junction location (OR 0.103, 95% CI 0.011-0.983, p = 0.048). Only WHO grade II tumors (OR 2.85, 95% CI 1.208-6.727, p = 0.017) was a predictor for SSEP changes. CONCLUSIONS: Our study represents the largest cohort describing sensitivity, specificity, and predictive factors for intraoperative changes and postoperative outcomes of resection of IMSCTs. A poorly defined baseline and cervicomedullary tumor location were predictors of IONM MEP changes, whiIe WHO grade II tumors were a predictor for both IONM SSEP and MEP changes.

Endoscopic endonasal approach for resection of odontoid process, decompression of the cervicomedullary junction spinal cord, and resection of pannus.

Odontoid pannus is an abnormal collection of degenerative or inflammatory tissue on the C1-dens joint that can result in severe spinal cord compression myelopathy. Treatment options vary depending on severity and etiology. In cases of severe cord compression, surgical management could be either through a purely posterior approach or in combination with an anterior decompression via endoscopic endonasal approach (EEA). This case presents a 77-year-old female who underwent posterior cervical fixation for odontoid pannus causing dramatic cervical myelopathy who failed to improve over a 6-month period and required anterior transodontoid pannus resection and decompression via EEA. The video can be found here: https://stream.cadmore.media/r10.3171/2024.1.FOCVID23176.

A case of vertebrobasilar dolichoectasia manifesting as sudden sensorineural hearing loss with vertigo

Vertebrobasilar dolichoectasia (VBD) is a rare vascular condition characterized by the elongation, widening, and tortuosity of the vertebrobasilar artery. It can lead to various symptoms due to compression of cranial nerves and brainstem structures. We report a rare case of VBD presenting as sudden sensorineural hearing loss (SSNHL) with vertigo and spontaneous downbeat nystagmus in a 65-year-old woman with a history of hypertension. Magnetic resonance imaging revealed a tortuous and dilated right vertebrobasilar artery compressing the brainstem and left 8th cranial nerve root entry zone, without signs of acute cerebellar stroke. The compression of the anterior inferior cerebellar artery and cervicomedullary junction was also noted, suggesting a vascular cause for her symptoms. Following high-dose steroid treatment, the patient showed significant hearing improvement. This case underscores the importance of considering VBD in patients with unexplained SSNHL and vertigo, highlighting the role of detailed vascular imaging in the diagnosis and management of such cases.

Pathogenesis of EMA negative PR negative Microcystic Meningioma: A Case Report

A patient, aged 35 years female complained of headache. CT examination revealed a non-succable tumor at anterolateral aspect of dura. Tumor extended from the right cervicomedullary junction upto C7 level. Tumor was excised and multiple soft tissue pieces, together measuring 1.5×1×1 cm were cellected. All the pieces were sectioned. Tumor had a sieve-like and cyst-like appearance. Section showed a circumscribed globular tumor which consisted of proliferated bland spindle cells. Tumor had an edematous stroma and presented a microcystic appearance. The cells had elongated ovoid nuclei and mild eosinophilic cytoplasm. Several thin-walled vascular spaces were also seen in the tumor. Strong positive reaction was obtained with an anti-S100 antibody, suggesting a neural origin of tumor cells. Further, anti-Ki 67 antibody gave mild reaction (Ki67 index was 12%) suggesting benign neoplasm. Anti-CD 34 and anti-D2.40antibodies gave positive reactions (2+) with small blood vessels of the tumor. Keywords: Benign cystic neoplasm with similar behavior among various subtypes.

Supra- and Infratentorial Extradural Hematoma: A Series of Three Cases with Literature Review

AbstractThe extradural hematoma (EDH) of the posterior fossa is a rare clinical condition in head injury cases. The posterior fossa extradural hematoma (PFEDH) contributes to not more than 4 to 8% of all the EDH encountered in traumatic brain injury. The limited volume of the posterior fossa leads to early clinical deterioration and, if not subjected to timely intervention, may be fatal. This rapid deterioration is because of significant compression over the brainstem and cervicomedullary junction as well as obstructive hydrocephalus. The PFEDHs are often associated with fracture of the occipital bone, which may lead to the extension of hematoma in the supratentorial and infratentorial spaces. The traumatic supra- and infratentorial EDH (TSIEDH) constitutes less than 2% of all the EDH. Limited literature is available regarding TSIEDH, and the majority are in the form of isolated case reports. We share our experience of three cases over the last 5 years from a tertiary care referral institute with a literature review of TSIEDH. Two of these cases were managed nonoperatively, and one underwent surgical evacuation of hematoma. In the present study, we share our experience regarding prompt diagnosis and management of this particular subset of traumatic brain injury patients. We also describe the surgical technique for evacuation of TSIEDH. Early diagnosis and prompt surgical intervention can be life-saving as these hematomas may have a benign clinical presentation but rapid clinical deterioration.

Chiari I Malformation Presenting Vertical Gaze-Evoked Nystagmus : A Case Report

Abstract
 Introduction : Chiari malformation is characterized by herniation of posterior cerebellar vermis in which type 1 malformation has coexisting syringomyelia of cervicothoracic spinal cord. This malformation can be congenital or acquired, in which gaze-evoked nystagmus is the typical movement deficit. This case aimed to report a case of vertical gaze-evoked nystagmus as a primary symptom to detect Type I Chiari Malformation.
 Case Illustration : A 44-year-old woman presented with involuntary movements of both eyes in the last 5 months with vision problems in which objects appear to jump or vibrate. Visual acuity was 20/50 in both eyes with 12 prism diopters BI exotropia. We recognized vertical and torsional nystagmus in upgaze without any movement in primary gaze. While performing supraduction, the oscillation was detected and increased. Brain MRI revealed Type I Chiari Malformation.
 Discussion : Nystagmus was seen in many diseases of the central nervous system, in particular those affecting the brainstem and cerebellum. Vertical gaze evoked nystagmus was a disorder of the gaze holding function, purely vertical gaze-evoked nystagmus is observed in midbrain lesions involving the interstitial nucleus of Cajal (INC) as the neural integrator for vertical gaze-holding function. Based on this pathophysiology, the Brain MRI of this patient revealed some degrees of compression in midbrain, and cervico medullary junction due to her brain malformation.
 Conclusion : A sustained gaze-evoked nystagmus is an important ocular finding that may indicate serious neurologic pathology. It is important for an eye care provider to thoroughly examine additional tests to determine the underlying cause of the nystagmus.

Giant Invasive Schwannomas of C1 Root – Technical Challenges and Report of the First Two Cases in Literature

Abstract Giant invasive schwannomas (GISs) have been defined as different from other spinal schwannomas. C1 schwannomas are rare and often described with other high cervical tumors. GISs of C1 have not been previously described. Two cases of GIS are reported. In both patients, presenting with myelopathy, the lesions were extradural and intradural with posterior, lateral, and anterior extensions, compressing the cervicomedullary junction (CMJ) and displacing it. The V3-4 segments of the vertebral artery (VA) were closely associated. A posterolateral approach was used to initially expose and debulk the extradural portion of the lesion, which allowed access to the intradural component. The latter was followed anterior and/or posterior to the CMJ and excised completely. The tumors were dissected at the VA. Bleeding from the perivertebral venous plexus was controlled using topical hemostats. A small bit of tumor was left in a blind area anterior to the C1 arch in one patient. There were no complications and both patients improved in the postoperative period. GIS of the C1 are rare lesions in a difficult location. Complex relationships to the CMJ, lower cranial nerves, VA, and bony spine need a careful preoperative understanding of the anatomy and planning of surgery.

Database Review of 514 Patients with Os Odontoideum. Detailed Analysis of 258 Surgically Treated (1978-2019).

Database review (1978-2019) is to identify the cause of os odontoideum, its presentation, associated abnormalities, and management recommendations. Review of referral database of 514 patients and 258 surgically treated patients ages 4-64years. Detailed history of early childhood trauma and initial encounter record retrieval were made. Patients had dynamic motion radiographs, dynamic motion MRI and also CT to identify pathology and reducibility of craniocervical instability. Preoperative crown halo traction was made before the year 2000 except in children. Intraoperative traction with O-arm/CT documentation was made since 2001. Reducible and partially reducible cases underwent halo traction under general anesthesia distraction, dorsal stabilization, and rib graft augmentation for fusion. Later semi-rigid instrumentation and subsequently rigid instrumentation was made. Irreducible compression of cervicomedullary junction was treated with ventral decompression. The follow up was 3-20years. Database; acute worsening after trauma 262, insidious neurological deficit 252. Minimal/normal motion with neurological deficit was present in 18, previous C1-C2 fusion with worsening in 18. 28 patients of 64 without treatment worsened in 4years. An intact odontoid process was seen in 52 children of 156 who had early craniovertebral junction trauma and later developed os odontoideum. There were 174 patients with reducible lesions and partially reducible were 22. Irreducible lesions were 62. Of the reducible, 50 underwent transarticular C1-C2 fusion, 26 C1 lateral mass, and C2 pars screw fixation. 182 had occipitocervical fusion (19 had extension of previous C1-C2 fusion and 43 after transoral decompression). 62 with irreducible ventral compression of the cervicomedullary junction underwent transoral decompression; 43 had a trapped transverse ligament between the os and C2 body and 19 previous C1-C2 fusions. Compression was by the axis body, os odontoideum, and the posterior C2 arch. Syndromic and skeletal/connective tissue abnormalities were found in 86 (36%). 2 patients worsened, age 10 and 62, due to failure of semi-rigid construct. The etiology of os odontoideum is multifactorial considering the associated abnormalities, reports of congenital-familiar occurrence, and early childhood craniovertebral trauma which also plays a role in the etiology. Patients with reducible lesions require stabilization. Asymptomatic patients are at risk for later instability. Patients who underwent childhood C1-C2 fusion must be followed for later problems. The irreducibility was seen due to trapped transverse ligament, pannus, or previous dorsal C1-C2 fusion.

Stereotactic Radiosurgery for Cranial and Spinal Hemangioblastomas: A Single-Institution Retrospective Series.

Stereotactic radiosurgery (SRS) has been an attractive treatment modality for both cranial and spinal hemangioblastomas, especially for multiple lesions commonly associated with von Hippel-Lindau (VHL) disease. This study aims to provide the largest long-term analysis of treatment efficacy and adverse effects of SRS for cranial and spinal hemangioblastomas at a single institution. We evaluated the clinical and radiological outcomes of patients with hemangioblastomas treated with CyberKnife SRS at our institute from 1998 to 2022. The follow-up data were available for 135 hemangioblastomas in 35 patients. Twenty-eight patients had 123 hemangioblastomas associated with VHL, and 7 had 12 sporadic hemangioblastomas. The median age was 36 years, and the median tumor volume accounted for 0.4 cc. The SRS was administered with the median single-fraction equivalent dose of 18 Gy to the 77% median isodose line. At a median follow-up of 57 months (range: 3-260), only 20 (16.2%) of the VHL-associated and 1 (8.3%) sporadic hemangioblastomas progressed. The 5-year local tumor control rate was 91.3% for all hemangioblastomas, 91.7% among the sporadic lesions, and 92.9% in patients with VHL. SRS improved tumor-associated symptoms of 98 (74.8%) of 131 symptomatic hemangioblastomas, including headache, neck pain, dizziness, visual disturbances, dysesthesia, ataxia, motor impairment, seizures, and dysphagia. Two patients developed radiation necrosis (5.7%), and 1 of them required surgical resection. SRS is a safe and effective treatment option for patients with hemangioblastomas in critical locations, such as the brainstem, cervicomedullary junction, and spinal cord, and in patients with multiple hemangioblastomas associated with VHL disease.

Endoscopic odontoidectomy for brainstem compression in association with posterior fossa decompression and occipitocervical fusion.

Endonasal endoscopic odontoidectomy (EEO) is an alternative to transoral surgery for symptomatic ventral compression of the anterior cervicomedullary junction (CMJ), allowing for earlier extubation and feeding. Because the procedure destabilizes the C1-2 ligamentous complex, posterior cervical fusion is often performed concomitantly. The authors' institutional experience was reviewed to describe the indications, outcomes, and complications in a large series of EEO surgical procedures in which EEO was combined with posterior decompression and fusion. A consecutive, prospective series of patients who underwent EEO between 2011 and 2021 was studied. Demographic and outcome metrics, radiographic parameters, extent of ventral compression, extent of dens removal, and increase in CSF space ventral to the brainstem were measured on the preoperative and postoperative scans (first and most recent scans). Forty-two patients (26.2% pediatric) underwent EEO: 78.6% had basilar invagination, and 76.2% had Chiari type I malformation. The mean ± SD age was 33.6 ± 3.0 years, with a mean follow-up of 32.3 ± 4.0 months. The majority of patients (95.2%) underwent posterior decompression and fusion immediately before EEO. Two patients underwent prior fusion. There were 7 intraoperative CSF leaks but no postoperative CSF leaks. The inferior limit of decompression fell between the nasoaxial and rhinopalatine lines. The mean ± SD vertical height of dens resection was 11.98 ± 0.45 mm, equivalent to a mean ± SD resection of 74.18% ± 2.56%. The mean increase in ventral CSF space immediately postoperatively was 1.68 ± 0.17 mm (p < 0.0001), which increased to 2.75 ± 0.23 mm (p < 0.0001) at the most recent follow-up (p < 0.0001). The median (range) length of stay was 5 (2-33) days. The median time to extubation was 0 (0-3) days. The median time to oral feeding (defined as, at minimum, toleration of a clear liquid diet) was 1 (0-3) day. Symptoms improved in 97.6% of patients. Complications were rare and mostly associated with the cervical fusion portion of the combined surgical procedures. EEO is safe and effective for achieving anterior CMJ decompression and is often accompanied by posterior cervical stabilization. Ventral decompression improves over time. EEO should be considered for patients with appropriate indications.

Upper cervical intramedullary schwannoma of the spinal cord presenting with myelopathy: illustrative case.

Intramedullary schwannomas account for 1.1% of all spinal schwannomas. Preoperative diagnosis is best accomplished by thoroughly evaluating clinical and radiological characteristics, accompanied by a high index of suspicion. The authors report a case of C2-3 intramedullary schwannoma in a young male who presented with neck pain and vertigo. The current literature is also reviewed. The authors reviewed the data of a young male with a 2-month history of neck pain and vertigo. Magnetic resonance imaging of the brain and cervical spine showed an intramedullary mass at C2-3 with a syrinx extending into the cervicomedullary junction. Laminectomy, myelotomy, and microsurgical excision of the mass under intraoperative neurological monitoring (IONM) were done. Postoperative pathology reported the specimen as a schwannoma. Gross-total resection of a schwannoma using IONM is the treatment of choice because of the lesion's benign nature, a better prognosis, and defined cleavage plane. Schwannomas should be included in the differential diagnosis of intramedullary spinal tumors. Because of its progressive nature, early surgery is recommended in symptomatic patients.

P11.49.B STEREOTACTIC RADIOSURGERY FOR CRANIAL AND SPINAL HEMANGIOBLASTOMAS: A SINGLE-INSTITUTION SERIES

Abstract BACKGROUND Stereotactic radiosurgery (SRS) has been an attractive treatment modality for both cranial and spinal hemangioblastomas, especially for multiple lesions commonly associated with von Hippel-Lindau (VHL) disease. This study aims to provide the largest long-term analysis of treatment efficacy and adverse effects of SRS for cranial and spinal hemangioblastomas at a single institution. MATERIAL AND METHODS We evaluated the clinical and radiological outcomes of patients with hemangioblastomas treated with CyberKnife SRS at our institute from 1998 to 2022. The follow-up data were available for 135 hemangioblastomas in 35 patients. Twenty-eight patients had 123 hemangioblastomas associated with VHL and 7 had 12 sporadic hemangioblastomas. The median age was 36 years and the median tumor volume accounted for 0.4 cc. The SRS was administered with the median single-fraction equivalent dose (SFED) of 18 Gy to the 77% median isodose line. RESULTS At a median follow-up of 57 months (range: 3-260), only 20 (16.2%) of the VHL-associated and 1 (8.3%) sporadic hemangioblastomas progressed. The 5-year local tumor control (LTC) rate was 91.3% for all hemangioblastomas, 91.7% among the sporadic lesions, and 92.9% in VHL patients. SRS improved tumor-associated symptoms of 98 (74.8%) of 131 symptomatic hemangioblastomas, including headache, neck pain, dizziness, visual disturbances, dysesthesia, ataxia, motor impairment, seizures, and dysphagia. Two patients developed radiation necrosis (5.7%) and 1 of them required surgical resection. CONCLUSION SRS is a safe and effective treatment option for patients with hemangioblastomas in critical locations such as the brainstem, cervicomedullary junction, and spinal cord, and in patients with multiple hemangioblastomas associated with VHL disease.

Linking corticospinal tract activation and upper-limb motor control in adults with cerebral palsy.

To quantify the cervicomedullary motor evoked potentials (CMEPs) at the cervical spinal level in adults with cerebral palsy (CP) and determine if altered CMEPs are linked with upper-extremity motor function in this population. This cross-sectional study consisted of a cohort of adults with CP (n = 15; mean age = 33 years 5 months [SD = 11 years 8 months]); Manual Ability Classification System levels I-IV) and neurotypical controls (n = 18; mean age = 30 years 10 months [SD = 10 years 4 months]), who were recruited to participate at an academic medical center. Adults with CP and typical adults (controls) were stimulated at the cervicomedullary junction to assess CMEPs at the cervical spinal cord level. Upper-extremity motor function was quantified using the Box and Blocks and Purdue Pegboard tests, self-reported upper-extremity function (UEF), and assessments of selective motor control. At higher stimulation levels, the contralateral CMEP responses of adults with CP were different from typical adults (p = 0.032). Reduced CMEP was correlated with reduced upper-limb function, including worse performance on the Box and Blocks (rho = 0.625, p = 0.025) and Purdue Pegboard tests (rho = 0.701, p = 0.010), lower self-reported UEF (rho = 0.761, p = 0.009), and overall selective motor control (rho = 0.731, p = 0.007). Changes in the activation of spinal motoneurons through corticospinal pathways may have an important role in the altered upper-extremity motor function of individuals with CP.

Recommendations for neuroradiological examinations in children living with achondroplasia: a European Society of Pediatric Radiology and European Society of Neuroradiology opinion paper.

Children living with achondroplasia are at an increased risk of developing neurological complications, which may be associated with acute and life-altering events. To remediate this risk, the timely acquisition of effective neuroimaging that can help to guide clinical management is essential. We propose imaging protocols and follow-up strategies for evaluating the neuroanatomy of these children and to effectively identify potential neurological complications, including compression at the cervicomedullary junction secondary to foramen magnum stenosis, spinal deformity and spinal canal stenosis. When compiling these recommendations, emphasis has been placed on reducing scan times and avoiding unnecessary radiation exposure. Standardized imaging protocols are important to ensure that clinically useful neuroimaging is performed in children living with achondroplasia and to ensure reproducibility in future clinical trials. The members of the European Society of Pediatric Radiology (ESPR) Neuroradiology Taskforce and European Society of Neuroradiology pediatric subcommittee, together with clinicians and surgeons with specific expertise in achondroplasia, wrote this opinion paper. The research committee of the ESPR also endorsed the final draft. The rationale for these recommendations is based on currently available literature, supplemented by best practice opinion from radiologists and clinicians with subject-specific expertise.

Application of the Robotic-Assisted Digital Exoscope for Resection of Posterior Fossa Tumors in Adults: A Series of 45 Cases.

Complete safe resection is the goal when pursuing surgical treatment for posterior fossa (PF) tumors. Efforts have led to the development of the exoscope that delineates tumors from non-neoplastic brain. This investigation aims to assess patient outcomes where PF tumor resection is performed with the exoscope by a retromastoid or suboccipital approach. A retrospective analysis was conducted for patients with PF tumors who underwent exoscope resection from 2017 to 2022. Patient demographics, clinical, operative, and outcome findings were collected. Extent of resection studies were also performed. Associations between perioperative data, discharge disposition, progression-free survival (PFS), and overall survival (OS) were evaluated. A total of 45 patients (22 male patients) with a median age of 57 years were assessed. Eighteen (40%) and 27 patients (60%) were diagnosed with malignant and benign tumors, respectively. Tumor neurovascular involvement was found in 28 patients (62%). Twenty-four (53%) and 20 (44%) tumors formed in the cerebellum and cerebellopontine angle cistern, respectively. One tumor (2%) was found in the cervicomedullary junction. The mean extent of resection was 96.7% for benign and malignant tumors. The PFS and OS rate at 6 months (PFS6, OS6) was 89.7% and 95.5%, respectively. Neurological complications included sensory loss and motor deficit, with 11 patients reporting no postoperative symptoms. Of the neurological complications, 14 were temporary and 9 were permanent. The exoscope is an effective intraoperative visualization tool for delineating PF tumors. In our series, we achieved low postoperative tumor volumes and a high gross total resection rate.

Measurement of brainstem diameter in small-breed dogs using magnetic resonance imaging.

Measurement of brainstem diameters (midbrain, pons, and medulla oblongata)is of potential clinical significance, as changes in brainstem size may decrease or increase due to age, neurodegenerative disorders, or neoplasms. In human medicine, numerous studies have reported the normal reference range of brainstem size, which is hitherto unexplored in veterinary medicine, particularly for small-breed dogs. Therefore, this study aims to investigate the reference range of brainstem diameters in small-breed dogs and to correlate the measurements with age, body weight (BW), and body condition score (BCS). Herein, magnetic resonance (MR) images of 544 small-breed dogs were evaluated. Based on the exclusion criteria, 193 dogs were included in the midbrain and pons evaluation, and of these, 119 dogs were included in the medulla oblongata evaluation. Using MR images, the height and width of the midbrain, pons, and medulla oblongata were measured on the median and transverse plane on the T1-weighted image. For the medulla oblongata, two points were measured for each height and width. The mean values of midbrain height (MH), midbrain width (MW), pons height (PH), pons width (PW), medulla oblongata height at the fourth ventricle level (MOHV), medulla oblongata height at the cervicomedullary (CM) junction level (MOHC), rostral medulla oblongata width (RMOW), and caudal medulla oblongata width (CMOW) were 7.18 ± 0.56 mm, 17.42 ± 1.21 mm, 9.73 ± 0.64 mm, 17.23 ± 1.21 mm, 6.06 ± 0.53 mm, 5.77 ± 0.40 mm, 18.93 ± 1.25 mm, and 10.12 ± 1.08 mm, respectively. No significant differences were found between male and female dogs for all the measurements. A negative correlation was found between age and midbrain diameter, including MH (p < 0.001) and MW (p = 0.002). All brainstem diameters were correlated positively with BW (p < 0.05). No significant correlation was found between BCS and all brainstem diameters. Brainstem diameters differed significantly between breeds (p < 0.05), except for MW (p = 0.137). This study assessed linear measurements of the brainstem diameter in small-breed dogs. We suggest that these results could be useful in assessing abnormal conditions of the brainstem in small-breed dogs.

Spontaneous obliteration of a spinal perimedullary fistula.

We herewith report a young patient who had an incidental spinal vascular malformation of the cervicomedullary junction discovered during a work-up for anosmia. Angiography demonstrated a perimedullary spinal arteriovenous fistula with supply from lateral spinal arteries arising from bilateral V3 level segmental arteries. It was decided to manage the patient conservatively with magnetic resonance imaging monitored biannually. On a recent follow-up magnetic resonance, nearly 10 years later, we noted a subtle change in caliber and imaging characteristics at the posterior margin of the cervical medullary junction. Repeat digital-subtraction angiography showed no evidence of early venous filling from the previously involved branches. Microcatheter exploration of the right lateral spinal artery confirmed spontaneous occlusion of the spinal perimedullary arteriovenous fistula, without any persistent shunting. Spontaneous resolution of a spinal vascular malformation is rare; this case demonstrates the dynamic nature of shunting vascular malformations and that spontaneous obliteration of arteriovenous shunts is possible.