Multivariate risk factor analysis and literature review of postoperative deterioration in Karnofsky Performance Scale score in elderly patients with skull base meningioma.

OBJECTIVE Elderly patients are particularly at risk for severe morbidity following surgery. Among the various risk factors, age and skull base location of meningioma are known to be poor prognostic factors in meningioma surgery. The authors conducted this study to analyze significant preoperative risk factors in elderly patients with skull base meningioma. METHODS A total of 265 elderly patients (≥ 65 years old) with meningioma were surgically treated at the authors' institute and affiliated hospitals between 2000 and 2016, and these cases were reviewed. Among them, 57 patients with skull base meningioma were evaluated. Among the various risk factors, the authors analyzed age, sex, Karnofsky Performance Scale (KPS) score, American Society of Anesthesiologists score, and tumor size, location, and pathology. Body mass index (BMI) and serum albumin were investigated as the frailty factors. The authors also reviewed 11 surgical studies of elderly patients ≥ 60 years old with meningioma. RESULTS The mean age was 72.4 ± 5.7 years, and 42 patients were female (73.6%). The mean size of meningioma was 36.6 ± 14.8 mm at the maximum diameter, and the mean follow-up period was 31.1 ± 31.5 months. (The continuous variables are expressed as the mean ± SD.) Histopathological investigation revealed a higher incidence (71.9%) of WHO Grade I. The rates of deterioration after surgery, at 3 months, and at 1 year were 33.3%, 37.3%, and 39.1%, respectively. Univariate analysis revealed location, preoperative KPS score, BMI level 2, and serum albumin level (p = 0.010, 0.017, 0.0012, and 0.0019, respectively) to be poor prognostic factors. Multivariate analysis revealed that location (p = 0.038) and BMI (p = 0.035) were risk factors for KPS score deterioration immediately after surgery. According to the 11 papers reviewed, the median rate (25th-75th percentile) of skull base-related location was 43.5% (39.6-47.75); for asymptomatic status the mean was 24%; and for mortality at 3 months and 1 year the medians were 6.3% (0.7-7.1) and 8% (4.8-9.4), respectively. CONCLUSION Careful preoperative assessment based on the frailty concept was essential for better outcome in elderly patients with skull base meningioma. The BMI is appropriate as a quantitative factor for measure of frailty, particularly in elderly individuals with skull base meningioma. Further prospective randomized controlled trials are necessary to validate frailty as a preoperative risk factor. Not only patient selection but also surgical timing was an important factor.

Surgical resection of large encephalocele: a report of two cases and consideration of resectability based on developmental morphology.

INTRODUCTION: The first-line treatment of encephalocele is reduction of herniated structures. Large irreducible encephalocele entails resection of the lesion. In such case, it is essential to ascertain preoperatively if the herniated structure encloses critical venous drainage. CASE REPORTS: Two cases of encephalocele presenting with large occipital mass underwent magnetic resonance (MR) imaging. In first case, the skin mass enclosed the broad space containing cerebrospinal fluid and a part of occipital lobe and cerebellum. The second case had occipital mass harboring a large portion of cerebrum enclosing dilated ventricular space. Both cases had common venous anomalies such as split superior sagittal sinus and high-positioned torcular herophili. They underwent resection of encephalocele without subsequent venous congestion. We could explain the pattern of venous anomalies in encephalocele based on normal developmental theory. CONCLUSION: Developmental theory connotes that major dural sinuses cannot herniate into the sac of encephalocele. Irrespective to its size, encephalocele can be resected safely at the neck without subsequent venous congestion.

Preoperative simulation of the running course of the abducens nerve in a large petroclival meningioma: a case report and literature review.

One of the most important and useful pieces of information in the preoperative evaluation of a large petroclival meningioma is the running course of the abducens nerve. The abducens nerve is small and has a long intracranial course, making it prone to compression by the tumor at various anatomical points. In relatively large tumors, it is difficult to confirm the entire course of the abducens nerve, even by heavy T2-thin slice imaging. We report a case of successful preoperative estimation of the course of the abducens nerve that aided in its complete preservation during the resection of a large petroclival tumor.

Application of Compound Action Potential of Facial Muscles Evoked by Transcranial Stimulation as a Reference Waveform of Motor-evoked Potential in Spinal Surgery.

Transcranial electrical stimulation motor-evoked potential (TES-MEP) has been widely used to monitor major motor pathways in cranial and spinal surgeries. However, the results of TES-MEP might be strongly influenced by anesthetic agents and muscle relaxants. To compensate for this effect, a technique using compound muscle action potentials of the abductor pollicis brevis (APB-CMAP) evoked by median nerve stimulation has recently been reported. In this article, we adopted the transcranial electrical stimulation motor-evoked potential of facial muscles (TES-FMEP) instead of APB-CMAP as a reference waveform for compensation. Intraoperative monitoring in spinal surgeries using TES-MEP, TES-FMEP and APB-CMAP was performed in 64 patients. We compared with and without compensation methods using TES-FMEP and APB-CMAP to evaluate TES-MEP. The cases which demonstrated postoperative motor disturbance, including transient symptoms, were judged to be positive cases. Postoperative transient paraplegia was shown in one intramedullary tumor case among those 64 cases. Compensation by TES-FMEP exhibited the highest specificity (90.5%) and lowest false-positive rate (9.5%) among the three compensation modalities when evaluated at 80% amplitude decrease. TES-FMEP, being derived from motor cortex stimulation, is not influenced by the original spinal lesion or surgical manipulation of the spine. Therefore, compensation using TES-FMEP is suitable for intraoperative monitoring during spinal surgery. The authors advocate TES-FMEP as a reference waveform for the compensation of intraoperative TES-MEP.

A Case of Holocord Leptomeningeal Dissemination from Cerebellar Hemangioblastoma without von Hippel-Lindau Disease.

Hemangioblastoma disseminated along leptomeninges from the solitary cranial lesion without von Hippel-Lindau (VHL) disease is a quite rare instance with 23 cases reported in 40 years. We add a new case and discuss these rare instances. A 55-year-old female underwent surgery for total removal of cerebellar hemangioblastoma. Twenty months later, magnetic resonance (MR) images of the spinal cord revealed a tumor compressing the thoracic cord at T3-4 level which was removed en bloc by emergent spinal surgery. However, paraplegia and bowel bladder dysfunction recurred 5 months after the spinal surgery. Spine MR images showed diffuse enhancement of subarachnoid space. Exploratory surgery disclosed that the enhanced lesion was disseminated hemangioblastoma. After whole spinal irradiation, she was transferred to a palliative care hospital. Even after complete removal, possibility of leptomeningeal dissemination demands continuous follow-up. The mechanism of seeding of hemangioblastoma remains unclear, but attention must be paid to avoid spreading tumor cells during surgery because all the disseminated cases had precedent cranial surgery.

A Case of Cutaneous Meningioma in the Rudimentary Meningocele.

We report a rare case of neonatal cutaneous meningioma derived from a rudimentary meningocele. This neonate had a congenital skin-covered hump in the thoracolumbar region. Computed tomography showed bifid laminae of T12 and L1 underneath the mass lesion. Magnetic resonance images showed the mass to have no cerebrospinal fluid space and that it had a stalk connecting to the spinal canal. Split cord malformation was also observed under the bifid laminae. Because of the increasing size of the lump and cosmetic reasons, the parents opted for surgical treatment. We operated on the patient 9 months after birth. Operative findings showed that the cutaneous mass was connected to intraspinal contents by a vascular stalk and it was totally removed. The split spinal cord was untouched. The histopathological findings of the mass showed components of meningioma with a collagenous matrix. We concluded that this patient had a meningioma derived from rudimentary meningocele.

A case of petrous apex cholesterol granuloma successfully treated with endoscopic endonasal surgery.

A transcranial approach in combination with a transpetrosal setting has been the mainstream of surgical treatment of cholesterol granulomas in the petrous apex. However, endoscopic endonasal surgery has become a choice of treatment for these lesions with recent advancements in surgical techniques and instruments. We report a successful case of cholesterol granuloma managed with endoscopic endonasal surgery. A 45-year-old woman, who had a long-standing history of otitis media, presented with left abducens nerve palsy and discomfort around the left eye. Magnetic resonance (MR) imaging showed a large cystic lesion, suggesting cholesterol granuloma, in the left middle fossa abutting the cavernous sinus and lateral wall of the sphenoid sinus. We chose an endoscopic endonasal approach to drain the contents of the cyst because the lesion protruded into the left sphenoid sinus. The sphenoid sinus was widely opened and the cyst wall was fenestrated with the assistance of an image guidance navigation system. Postoperative MR images confirmed the complete collapse of the cyst. She has been free from symptoms since the operation.

Relevance of the Foramen of Vesalius for Preoperative Tumor Embolization in Skull Base Meningioma.

OBJECTIVE: The objective of this study was to investigate the role of the foramen of Vesalius (FV) in the pathogenesis of skull base meningioma by analyzing data from various multi-image modalities. METHODS: For this single-center retrospective study, 39 consecutive patients with skull base meningioma who underwent tumor resection between January 2020 and March 2023 were enrolled. The anatomical and pathological characteristics of the FV were evaluated using computed tomography and 3-dimensional digital subtraction angiography. The clinical significance of the FV in tumor hemodynamics and treatment, such as preoperative tumor embolization, was investigated using the 3-dimensional digital subtraction angiography/computed tomography fusion images. RESULTS: We identified FV in 52% (17/27) of the finally included patients. In 10 (30%) patients, the FV was found bilaterally with no significant variation in appearance between the healthy and tumor-affected sides (P = 0.786). The mean FV diameter was significantly larger on the tumor-affected side (P = 0.010). No significant anatomical differences, like duplication and partial assimilation with the foramen ovale, were observed between the 2 sides. The FV was involved in venous skull base perfusion around the tumor in 9 cases. In 4 cases where it was the pathway for tumor feeders, preoperative tumor embolization via the FV resulted in disappearance of the tumor stain. No complications associated with endovascular treatment were observed. CONCLUSIONS: This study elucidated the anatomical asymmetry of the FV and its role in the hemodynamics of skull base meningioma. Our findings highlight the significance of performing anatomical and pathological evaluations of the FV in determining treatment strategies, including preoperative embolization, for skull base lesions.

Application of 4D-CTA using 320-row area detector computed tomography on spinal arteriovenous fistulae: initial experience.

Time-resolved computed tomography angiography (4D-CTA) using a 320-row area detector CT scanner has recently been applied in the evaluation of cranial vascular disorders. However, application of 4D-CTA to spinal vascular disorder evaluation has never before been described. The authors herein report their initial experience of 4D-CTA in the evaluation of spinal arteriovenous fistulas (AVFs) and compare this novel modality with other imaging modalities. Four consecutive patients with spinal AVF underwent time-resolved contrast-enhanced magnetic resonance angiography (trMRA), 4D-CTA, and selective catheter angiography (CA). In 4D-CTA, volume data was transformed into 3D volume-rendered images and maximum intensity projection. These images were also evaluated by time-resolved serial phases. Then, images of each modality were compared, focusing on the detection of perimedullary draining veins and the prediction of AVF location and drainage flow direction. All modalities successfully detected perimedullary draining veins in all cases. Location of the AVF was detected in all cases by CA. trMRA and 4D-CTA detected the AVF in three out of the four cases. With regard to flow direction, while 4D-CTA successfully depicted ascending or descending drainage flow in the spinal canal, CA failed to detect the flow direction in one case while trMRA failed in two cases. In the case with epidural AVF, 4D-CTA was the only technique to detect the flow direction of perimedullary drainage. Although this is only an initial experience of the application of 4D-CTA to spinal vascular diseases, 4D-CTA was capable of detecting the dynamic vascular flow of spinal AVFs. The authors believe that 4D-CTA can be a useful option in the evaluation of spinal AVFs.

Impact of intravenously administered cranial bone-derived mesenchymal stem cells on functional recovery in experimental spinal cord injury.

Impairments of the central nervous system, such as stroke, brain trauma, and spinal cord injury (SCI), cannot be reversed using current treatment options. Herein, we compared the characteristics of rat cranial bone-derived mesenchymal stem cells (rcMSCs) and rat bone marrow-derived mesenchymal stem cells (rbMSCs). We also investigated the therapeutic effects of intravenously administered rcMSCs and rbMSCs in a rat model of cervical SCI (cSCI) and elucidated its undrelying mechanism. Comprehensive comparative bioinformatics analysis of rcMSCs and rbMSCs RNA sequencing revealed that genes associated with leukocyte transendothelial migration and chemokine signaling were significantly downregulated in rcMSCs. Rats were divided into three groups that received intrtravenous administration of rcMSC, rbMSC, or phosphate-buffered saline (control) 24 h after cSCI. The rcMSC-treated group showed improved functional recovery over the rbMSC-treated and control groups, and reduced lesion volume compared with the control group. The mRNA expression of nitric oxide synthase 2 at the spinal cord lesion site was significantly higher in the rcMSC-treated group than in the control and rbMSCs-treated groups, whereas that of transforming growth factor-ß was significantly higher in the rcMSC-treated group compared to that in the control group. The transcriptome data indicated that rcMSCs and rbMSCs differentially affect inflammation. The intravenous administration of rcMSCs contributed to functional recovery and lesion reduction in cSCI. The rcMSCs have the potential to induce an anti-inflammatory environment in cSCI.

Assessment of Intraoperative Spinal Angiography via the Popliteal Artery for Spinal Vascular Diseases.

OBJECTIVE: Intraoperative spinal angiography via the popliteal artery for patients in the prone position has been reported only twice in 4 patients. This study aimed to clarify the safety precautions to be taken with this technique in a larger patient cohort. METHODS: Seven patients with spinal vascular disorders underwent intraoperative spinal angiography in the prone position via the popliteal artery. Ultrasound was used to evaluate the neurovascular anatomy in the popliteal fossa and guide the arterial puncture. Patient characteristics, features of angiography devices, puncture attempts, and angiography-related complications, such as hematoma formation and injury to the neurovascular bundle, were analyzed. RESULTS: The average number of arterial puncture attempts was 1.3 times (range: 1-2). Sheaths (4 and 4.5 Fr) with different ineffective lengths were used. In 1 case, a 4.5-Fr sheath was replaced with a 4-Fr sheath with a shorter noneffective length as the length of the catheter limited access to the target. Catheters with Type-JB2 tip shapes were used for craniocervical junction lesions, and those with Type-KAGAWA tip shapes were used for thoracic and lumbar spinal lesions. No puncture site complications were observed in any patient. CONCLUSIONS: Intraoperative spinal angiography via the popliteal artery was an effective tool in surgeries for spinal vascular diseases. The introduction of the ultrasound enabled atraumatic puncture of the popliteal artery. Spinal targets above T5 to T6 may be inaccessible from the popliteal fossa when using a 100-cm-long catheter.

A novel rat model for longitudinal electrophysiological evaluation after cold-induced brain injury.

OBJECTIVE: Cerebral contusion models of cold-induced injury are widely used in animal studies. However, owing to the difficulty of longitudinal recording of electrical stimulation transcranial motor evoked potential (tcMEP) in brain injury models of incomplete paralysis, to the authors' knowledge there have been no multimodal evaluations of cold-induced brain injury models that have included motor function and electrophysiological and histological evaluations. Therefore, in this study the authors aimed to perform a multimodal evaluation of a rat model of brain injury. METHODS: A brain injury model in female rats and a tcMEP recording technique based on the authors' previous study were established to enable multifaceted analysis, including longitudinal electrophysiological evaluation. RESULTS: The model showed incomplete paralysis of the right forelimb. Motor function showed recovery over time, and histological evaluation showed tissue changes associated with cerebral contusion. In addition, stable tcMEP waveforms were recorded before and after surgery and up to 4 weeks after injury. The tcMEP amplitude decreased significantly after injury and recovered over time. Furthermore, the amplitudes at 1, 7, and 14 days after injury were significantly lower than those at preinjury (p < 0.0006, p < 0.0007, and p < 0.0067, respectively). CONCLUSIONS: In the present study, the authors established a novel cold-induced brain injury rat model and technique that allowed for the evaluation of longitudinal tcMEP recording and demonstrated that multimodal evaluation for brain injury can be performed. This model can potentially be applied in future investigations of various therapies for brain injury.

Establishment of longitudinal transcranial stimulation motor evoked potentials monitoring of the forelimbs and hindlimbs in an ischemic stroke rat model.

Evaluation of motor function ischemic stroke rat models includes qualitative assessments such as the modified neurological severity score (mNSS). However, mNSS cannot evaluate the function of forelimbs and hindlimbs separately. We quantitatively assessed motor function in a middle cerebral artery occlusion (MCAO) rat model of ischemic stroke. We recorded transcranial stimulation motor evoked potentials (tcMEPs) from MCAO rats and measured the changes in onset latency and amplitude at the forelimbs and hindlimbs up to 28 days after stroke. All MCAO subjects showed hemiparesis. The amplitudes of tcMEPs in both fore- and hindlimbs were inversely correlated with mNSS scores, but the amplitudes in the forelimbs improved later than those in the hindlimbs. The onset latency of tcMEPs in the forelimbs and hindlimbs remained almost unchanged during the follow-up period. Our results showed the differences in tcMEPs amplitude recovery times between the forelimbs and hindlimbs after MCAO, which emphasizes the importance of separately evaluating forelimbs and hindlimbs in post-ischemic stroke models. This minimally invasive and longitudinal quantitative method could be useful for further research on diseases and neurogenesis.

Longitudinal electrophysiological changes after mesenchymal stem cell transplantation in a spinal cord injury rat model.

Transcranial electrically stimulated motor-evoked potentials (tcMEPs) are widely used to evaluate motor function in humans and animals. However, the relationship between tcMEPs and the recovery of paralysis remains unclear. We previously reported that transplantation of mesenchymal stem cells to a spinal cord injury (SCI) rat model resulted in various degrees of recovery from paraplegia. As a continuation of this work, in the present study, we aimed to establish the longitudinal electrophysiological changes in this SCI rat model after mesenchymal stem cell transplantation. SCI rats were established using the weight-drop method. The model rats were transvenously transplanted with two types of mesenchymal stem cells (MSCs), one derived from rat cranial bones and the other from the bone marrow of the femur and tibia bone, 24 h after SCI. A phosphate-buffered saline (PBS) group that received only PBS was also created for comparison. The degree of paralysis was evaluated over 28 days using the Basso-Beattie-Bresnahan (BBB) scale and inclined plane task score. Extended tcMEPs were recorded using a previously reported bone-thinning technique, and the longitudinal electrophysiological changes in tcMEPs were investigated. In addition, the relationship between the time course of recovery from paralysis and reappearance of tcMEPs was revealed. The appearance of the tcMEP waveform was earlier in MSC-transplanted rats than in PBS-administered rats (earliest date was 7 days after SCI). The MEP waveforms also appeared at approximately the same level on the BBB scale (average score, 11 points). Ultimately, this study can help enhance our understanding of the relationship between neural regeneration and tcMEP recording. Further application of tcMEP in regenerative medicine research is expected.

Healing process of Type II odontoid fractures after C1-C2 posterior screw fixation: Predictive factors for pseudoarthrosis.

Background: The healing process after C1-C2 posterior screw fixation (C1-C2 PSF) for odontoid fractures is not well understood. Here, we evaluated such processes and identified factors potentially contributing to pseudoarthroses following fusions for Type II odontoid fractures. Methods: Pre- and post-operative cervical radiographs and computed tomography (CT) images from 15 patients with preoperative Type II odontoid fractures who underwent C1-C2 PSF were retrospectively reviewed. Results: CT images identified three areas of bone fusion: The primary fracture site in the dens (9/15 patients, 60%), the atlanto-dental interspace (ADI) (10/15, 67%), and C1-C2 interlaminar space after onlay bone grafting (4/15, 27%). All patients showed bone fusion in at least one of three areas, while only one patient (6.7%) achieved bone fusion in all three areas. With these overall criteria, nine of 15 patients (60%) were considered fused, while six patients (40%) were determined to exhibit pseudoarthroses. Univariate analyzes showed that the preoperative C2-C7 SVA for the nonunion group was significantly larger versus the union group, and bone fusion at the level of the ADI was significantly more common in the nonunion versus the union group. Conclusion: CT studies identified three anatomical areas where bone fusion likely occurs after C1-C2 PSF. Increased sagittal balance in the cervical spine may negatively impact the fusion of odontoid fractures. Further, bone fusion occurring at other sites, not the primary fracture location, through stress shielding may contribute to delayed or failed fusions.

Spinal arteriovenous fistula in the lipoma of the filum terminale: A report of two cases and literature review.

BACKGROUND: Filum terminale arteriovenous fistulas (FTAVFs) are rare and their pathogenesis remains unknown. The authors report two cases of FTAVF that arose in the lipoma of the filum terminale. CASE DESCRIPTION: The two patients were 72 and 76 years of age, and both presented with a progressive paraparesis. The first patient had an arteriovenous fistula (AVF) located at L5 that was supplied by the anterior spinal artery originating from the left T10 intercostal artery. The second patient's AVF at L3-4 was fed by the anterior spinal artery originating from the left T8 intercostal artery. Both patients underwent partial resection of the filum terminale at the location of the shunts. The pathological examinations revealed that both the AVFs were embedded in the adipose tissue of the filum terminale, revealing the fatty fila that were not visible in preoperative magnetic resonance images. CONCLUSION: Two cases of FTAVF were successfully treated by obliterating the fistulas through partial resection of the affected fatty filum terminale. The literature review revealed 13 cases of FTAVF concomitant with the lipomas of the filum terminale. Resection and histological evaluation of the filum terminale should be performed to treat and elucidate the pathogenesis of FTAVF.

Imaging evolution from "presyrinx" to syrinx in patient with spinal lipoma.

Background: The evolution of syrinx formation has rarely been documented. Here, we report a patient whose "presyrinx" evolved on successive magnetic resonance (MR) images to a mature syrinx. Case Description: A patient had a lipoma and tethered cord at birth. At 3 weeks of age, he had undergone a partial removal of the lipoma and untethering of the spinal cord. At age 6, the thoracic MR images showed edema within the gray matter of the cord at the T7 level, consistent with a "presyrinx." In addition, subsequent MR studies (i.e., at age 7) showed a small cavity in the right posterior horn of the cord accompanied by further expansion throughout the right-sided gray matter. Despite repeated cord untethering at age 7, the T7 parenchymal cord change evolved into a mature syrinx by age 10. Conclusion: An infant with a lipoma/tethered cord, despite two instances of cord detethering (i.e., ages 3 weeks and 7 years), showed continued MR evolution of a "presyrinx" to a mature syrinx by age 10.

Spinal Osseous Epidural Arteriovenous Fistula with Intradural Reflux: A Case Report.

The authors report a rare case of spinal osseous epidural arteriovenous fistula (AVF) with intradural reflux. A 71-year-old lady with a past history of a T12 compression fracture and neurofibromatosis type 1 presented with progressive paraparesis. Magnetic resonance (MR) images of the thoracolumbar spine showed edema of the spinal cord and flow voids. Catheter angiography revealed segmental arteries from T11 to L1 feeding an AVF in the epidural space. The AVF drained not only into the epidural venous plexus but also into the perimedullary veins. Of note, there was an intraosseous drainage route that involved the basivertebral vein of T12. Under the diagnosis of spinal osseous epidural AVF with intradural reflux, surgical interruption of the intradural arterialized draining vein was performed. Spinal osseous epidural AVF with intradural reflux is rare with only four cases reported in the past. We believe that spinal osseous epidural AVF should be recognized as a variant of spinal epidural AVF.

Effects of Preservation of the Semispinalis Cervicis Inserted into C2 on Craniocervical Alignment After Laminoplasty.

OBJECTIVE: The preservation of nuchal musculature is essential for preventing axial pain and cervical malalignment after laminoplasty. A few studies have examined the effect of preservation of nuchal musculature on the degenerative progression after laminoplasty. We aimed to clarify the influence of preservation of the semispinalis cervicis inserted into C2 on cervical degenerative change and alignment after laminoplasty. METHODS: We retrospectively reviewed 106 consecutive patients who underwent C3-7 laminoplasty for cervical spondylotic myelopathy during 2006-2017. Patients were classified into 2 groups according to the preservation (P-group; n = 33) or detachment (D-group; n = 73) of the Semispinalis cervicis muscles inserted into the C2 spinous process. Parameters of cervical sagittal alignment, range of motion, and progressive degenerative changes next to or within the range of laminoplasty were evaluated in cervical spine radiographs, and magnetic resonance images obtained during follow-up period. RESULTS: In the D-group, the postoperative C2-7 Cobb angle significantly decreased (-0.06°/month), while the O-C2 Cobb angle significantly increased (0.07°/month). In addition, the C2-7 range of motion significantly decreased in the D-group (-0.12°/month). Degenerative changes in the laminoplasty range were found in 5 patients per group. Three patients from the D-group developed retroodontoid pseudotumors (P < 0.001). CONCLUSIONS: To maintain horizontal gaze, the craniocervical segment can compensate for the loss of lordosis by increasing the Cobb angle. Excessive compensation may exert mechanical stress on the atlantoaxial junction, contributing to the development of a retroodontoid pseudotumor. Preservation of the semispinalis cervicis inserted into C2 is critical for the prevention of malalignment after laminoplasty.

A novel bone-thinning technique for transcranial stimulation motor-evoked potentials in rats.

Transcranial electrical stimulated motor-evoked potentials (tcMEPs) are widely used to evaluate motor function in humans, and even in animal studies, tcMEPs are used to evaluate neurological dysfunction. However, there is a dearth of reports on extended tcMEP recordings in both animal models and humans. Therefore, this study examined a new technique for stably recording tcMEPs over several weeks in six healthy female Sprague-Dawley rats. We thinned the skull bone using the skull base and spinal surgery technique to reduce electrical resistance for electrical stimulation. tcMEPs were recorded on days 1, 7, 14, 21, and 28 after surgery. The onset latency and amplitude of tcMEPs from the hindlimbs were recorded and evaluated, and histological analysis was performed. Stable amplitude and onset latency could be recorded over several weeks, and histological analysis indicated no complications attributable to the procedure. Thus, our novel technique allows for less invasive, safer, easier, and more stable extended tcMEP recordings than previously reported techniques. The presently reported technique may be applied to the study of various nerve injury models in rats: specifically, to evaluate the degree of nerve dysfunction and recovery in spinal cord injury, cerebral infarction, and brain contusion models.