Rectus Capitis Posterior Major Research Articles

Soft Tissue Dissection in the Transcondylar Approach: A Modified Layered Technique to Maximize Lateral Access

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 Results The sternocleidomastoid (SCM) muscle was retracted anteriorly; the splenium capitis, semispinalis capitis, and longissimus capitis muscles were disconnected from the superior nuchal line and reflected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capitis posterior major muscles were then dissected off the inferior nuchal line, and the suboccipital muscle group was retracted inferomedially en bloc. The greater auricular nerve was retracted laterally with the SCM, and the greater occipital nerve was retracted inferomedially with the suboccipital muscle group.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

Modulation of Central Nociceptive Transmission by Manual Pressure Techniques in Patients with Migraine: An Observational Study.

Manual pressure in the upper cervical spine is used to provoke and reduce the familiar migraine headache. Information is scarce on the segmental levels, myofascial structure provocation, and reduction occurrences. The required dosage (amount of pressure, number of repetitions, and duration) has not been objectified yet. Prospective observational study. Thirty patients with migraine were examined interictally. Manual pressure was applied at four sites: the posterior arch of C1, the articular pillar of C2, the rectus capitis posterior major muscle, and the obliquus capitis inferior muscle, bilaterally. On sites where the familiar headache was provoked, the pressure was sustained to induce pain reduction (three repetitions). Provocation of familiar headache (yes/no), headache intensity (numerical pain rating scale), time to obtain a reduction of the headache (seconds), and applied pressure (g/cm2) were recorded. Provocation of the familiar headache occurred at the posterior arches C1 in 92%, and at one of the articular pillars of C2 in 65.3% of cases. At one of the rectus capitis major muscles, the familiar headache was provoked in 84.6% of cases; at one of the oblique capitis inferior muscles, the familiar headache was provoked in 76.9% of cases. The applied mean pressure ranged from 0.82 to 1.2 kg/cm2. Maintaining the pressure reduced headache pain intensity significantly between the start and end of each of the three consecutive trials (p < 0.04). This reduction occurred faster in the third application than in the first application (p = 0.03). Manual pressure at upper cervical segments provokes familiar referred migraine headaches, with low manual pressure. Maintaining the pressure reduces the referred head pain significantly, indicating modulation of central nociceptive transmission.

Course of the V3 segment of the vertebral artery relative to the suboccipital triangle as an anatomical marker for a safe far lateral approach: A retrospective clinical study

Background: The third segment of the vertebral artery (V3) is vulnerable during far lateral and retrosigmoid approaches. Although the suboccipital triangle (SOT) is a useful anatomical landmark, the relationship between V3 and the muscles forming the triangle is not well-described. We aimed to demonstrate the relationship between the V3, surrounding muscles, and SOT in clinical cases.Methods: Operative videos of patients with the vertebral artery (VA) and posterior inferior cerebellar artery (PICA) aneurysms treated with occipital artery-PICA bypass through the far lateral approach were examined. Videos from January 2015 to October 2021 were retrospectively reviewed to determine anatomy of the V3 and the SOT.Results: Fourteen patients were included in this study. The ipsilateral V3 was identified without injury in all patients using the bipolar cutting technique. The lateral 68.2% of the horizontal V3 segment, including the V3 bulge, was covered by the inferomedial part of the superior oblique muscle (SO). The medial 23.9% was covered by the inferolateral part of the rectus capitis posterior major muscle. The inferomedial part of the horizontal V3 segment is located within the SOT.Conclusion: Most of the V3, including the V3 bulge, were located beneath the SO and the inferomedial part of V3 located within the SOT. Elevation of the SO should be performed carefully using the bipolar cutting technique to avoid injury to the V3. To the best of our knowledge, this is the first description of the V3 relative to the SOT in the clinical setting.

Ultrasonography Method of Deep Cervical Muscles and Thickness Measurement Reliability in Cervicogenic Headache and Healthy Subjects:APilot Study

Introduction: In Cervicogenic Headache (CGH), motor control of muscles is impaired and deep upper neck muscles (extensor and flexor muscles) become atrophied. In this research, thickness measurement of Longus Capitis (LCap), Rectus Capitis Posterior Major (RCPM), and Obliquus Capitis Superior (OCS) muscles were conducted and intra-rater reliability of the thickness measurement of these muscles was assessed in CGH and healthy subjects.
 Materials and Methods: Twenty subjects, including 10 healthy subjects (19-32 years old) and 10 CGH patients (20-35 years old) participated in this study. LCap thickness was measured at the level of C3-C4 in the supine position and posterior muscles (RCPM and OCS) thickness at the C1-C2 level in the sitting position. All ultrasound images were captured by a linear probe with a 50-mm footprint in B mode option and frequency range of 9-12 Hz. Intraclass Correlation Coefficients (ICC), Standard Error Of Measurement (SEM), and the Smallest Detectable Difference (SDD) were calculated for data analysis.
 Results: The ICC for thickness measurement of LCap was from 0.70 to 0.91 (good to excellent), for RCPM thickness was from 0.69 to 0.94 and for OCS muscle thickness was from 0.87 to 0.98. SEM values for LCap were between 0.08 and 0.25 and the SDD values between 0.22 and 0.71. SEM values for RCPM were between 0.22 and 0.43 and these values were reported for OCS muscle between 0.19 and 0.45.
 Conclusion: The results indicated that the presented position and the level of ultrasonography in this study are appropriate and ultrasound is a reliable tool to measure the deep upper neck muscle thickness in CGH and healthy subjects.

Relationship between echogenicity of deep cervical muscles and pain laterality in subjects suffering from cervicogenic headache

ABSTRACT Objective This study investigated the deep upper cervical muscles echogenicity in cervicogenic headache (CGH) patients. Methods The echogenicity of longus capitis (LCAP), rectus capitis posterior major (RCPM), and obliquus capitis superior (OCS) muscles was measured by ultrasonography and analyzed by Image J software in 17 CGH patients matched with 17 healthy subjects. Results The echogenicity of all muscles in the CGH group was higher than that in healthy subjects. The echogenicity of the LCAP muscle on the right side was significantly different between the CGH and healthy subjects (p< 0.05), but there was no difference in the echogenicity of RCPM and OCS muscles between the groups (p> 0.05). Additionally, the echogenicity differences did not match with the pain side in CGH patients (p> 0.05). Conclusion Only the deep anterior muscle (LCAP) echogenicity affected by CGH and fatty infiltration occurred in this muscle. Hence, anterior muscle dysfunction is important in CGH diagnosis and treatment.

Implied Evidence of the Functional Role of the Rectus Capitis Posterior Muscles.

Osteopathic physicians often target the rectus capitis posterior minor (RCPm) and rectus capitis posterior major (RCPM) muscles when using muscle energy or soft tissue cervical techniques to treat patients with head and neck pain. The RCPm and RCPM muscles are located deep within the posterior occipitoatlantal and atlantoaxial interspaces, respectively. To characterize the functional role of RCPm and RCPM muscles by comparing electromyographic (EMG) activation patterns of these muscles with EMG activation patterns of specific flexor and extensor muscles of the head and neck, the sternocleidomastoid (SCM), and the splenius capitis (SC) muscles, respectively. Asymptomatic participants were recruited from the Michigan State University College of Osteopathic Medicine student body. Disposable 25-gauge, bipolar fine-wire intramuscular electrodes were used to collect EMG data from the right and left RCPm and RCPM muscles. Surface electrodes were used to collect EMG data from the right and left SCM and SC muscles. Data were collected as participants performed 4 cycles of flexion and extension with an external 4-lb force applied to the back of the head and the forehead. In RCPM muscles, EMG activity was significantly greater (P<.003) during flexion and extension of the head and neck when an external force was applied to the back of the head. EMG activity in SCM muscles was significantly greater (P<.0001) during flexion and extension of the head and neck when an external force was applied to the forehead. The authors observed that EMG activity in SC muscles was significantly greater (P<.015) during flexion and extension of the head and neck when an external force was applied to the back of the head. No significant difference was found in EMG activity in RCPm muscles (P<.834) during flexion and extension of the head and neck, regardless of whether the external force was applied to the back of the head or the forehead. The EMG activation patterns of the RCPm muscles suggest that their functional role may be to stabilize the occipitoatlantal joint by helping maintain congruency of the joint surfaces. In contrast, the EMG activation patterns of the RCPM muscles suggest that their functional role may be to contribute to extension of the head, primarily at the occipitoatlantal and the atlantoaxial joints.

Ultrasound‐guided botulinum toxin therapy for deep muscles in cervical dystonia

AbstractBotulinum toxin (BoNT) injection is the established first line of treatment for cervical dystonia, and the accurate injection into target muscles is of paramount importance to improve the treatment outcome. To this purpose, guided injections with the electromyography or the ultrasound (US) are commonly utilized. The current review provides personally invented US‐guided procedures to approach the obliquus capitis inferior (OCI), the semispinalis cervicis, the longissimus capitis, and the rectus capitis posterior major muscles for BoNT injection. Among them the OCI is particularly important because it is a strong head rotator and is an essential target for rotatocollis. The OCI is also involved in no‐no type of dystonic tremor and jaw protrusion (sagittal shift) and should be dealt with as a target of treatment in the routine practice. The US‐guided muscle identification followed by BoNT injection is a fundamental technique particularly for deep cervical muscles. As for the rectus capitis posterior major muscle, however, its demonstration technique with the US seems challenging.

Relationship between thickness of deep neck muscles synergy and painful side in patients with cervicogenic headache

ABSTRACT Objective: This study was conducted to evaluate changes in the thickness of the upper deep neck muscles in patients with cervicogenic headache (CGH). Methods: The thickness of the longus capitis (LCap) muscle, rectus capitis posterior major (RCPM), and obliquus capitis superior (OCS) muscles was measured by B-mode ultrasonography in 22 CGH patients matched with 22 healthy subjects. Data were analyzed using SPSS version 16. Results: The thickness of all muscles in the CGH group was less than healthy subjects. The thickness of the LCap muscle and right RCPM muscle was significantly different between the CGH and healthy subjects (p < .05), but there was no difference in the thickness of the OCS and left RCPM muscles between the groups (p > .05). Moreover, the thickness differences were not related to the CGH side (p > .05). Discussion: These muscles were atrophic due to CGH, but this phenomenon was not related to the headache side and was bilateral.

The myodural bridge complex defined as a new functional structure.

The connective tissue between suboccipital muscles and the cervical spinal dura mater (SDM) is known as the myodural bridge (MDB). However, the adjacent relationship of the different connective tissue fibers that form the MDB remains unclear. This information will be highly useful in exploring the function of the MDB. The adjacent relationship of different connective tissue fibers of MDB was demonstrated based upon three-dimensional visualization model, P45 plastinated slices and histological sections of human MDB. We found that the MDB originating from the rectus capitis posterior minor muscle (RCPmi), rectus capitis posterior major muscle (RCPma) and obliquus capitis inferior muscle (OCI) in the suboccipital region coexists. Part of the MDB fibers originate from the ventral aspect of the RCPmi and, together with that from the cranial segment of the RCPma, pass through the posterior atlanto-occipital interspace (PAOiS) and enter into the posterior aspect of the upper cervical SDM. Also, part of the MDB fibers originate from the dorsal aspect of the RCPmi, the ventral aspect of the caudal segment of the RCPma, and the ventral aspect of the medial segment of the OCI, enter the central part of the posterior atlanto-axial interspace (PAAiS) and fuse with the vertebral dura ligament (VDL), which connects with the cervical SDM. Our findings prove that the MDB exists as a complex structure which we termed the 'myodural bridge complex' (MDBC). In the process of head movement, tensile forces could be transferred possibly and effectively by means of the MDBC. The concept of MDBC will be beneficial in the overall exploration of the function of the MDB.

Unilateral Rectus Capitis Posterior Major Muscle Duplication: Clinical Implications

Here, we present an anomaly of the rectus capitis posterior major (RCPM) muscle, found during routine cadaver dissection in a gross anatomy course. The RCPM is one of four muscles in the suboccipital region, the superior portion of the posterior neck, inferior to the occipital region of the head. The suboccipital muscles, including the RCPM, maintains posture of the neck to support the head and facilitate flexion, extension and lateral bending of the neck and rotation of the head at the atlanto‐occipital joint. We observed a unilateral, right‐sided duplication of the RCPM. This anomaly has several clinical implications: (1) Contraction of this duplicate muscle may cause postural instability or shift toward the right side, leading to improper weight bearing of the head. This may also cause loss of range of motion in the head of neck. This may lead to chronic neck pain and cervicogenic headache. (2) The greater occipital nerve passes through the suboccipital triangle, as it relays cutaneous innervation from the occipital scalp. We observed the greater occipital nerve passing between the two RCPM muscles, suggesting a potential for compression and sensory deficits. (3) The vertebral artery also passes inferior to the suboccipital muscles on its course to the brain stem, and compression of the vertebral artery by the RCPM may reduce blood supply to the brain stem, leading to dizziness or other neurovascular symptoms. Overall, this anomalous muscle, though likely rare, may be identified as a potential cause of the aforementioned symptoms, and surgical intervention may be warranted in severe cases.Support or Funding InformationN/AThis abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Anatomical Parameters of the Rectus Capitis Posterior Major and Obliqus Capitis Inferior Muscles Based on an Oblique Sagittal Magnetic Resonance Scan Method

The deep suboccipital muscles has been shown to connect the spinal dura mater via dense connective tissue termed the myodural bridge (MDB). The MDB has both physiological and clinical implications. Data on morphological and imaging anatomical parameters of the deep suboccipital muscles are scare. In this study, T2-weighted images of rectus capitis posterior major (RCPma) and obliqus capitis inferior (OCI) of 109 healthy adults were obtained by 0-degree sagittal and 30-degree oblique sagittal continuous MRI scanning of the head and neck of the subjects. Sectional area parameters of the RCPma and the OCI were measured. The 0-degree sagittal section was measured with 5 mm bias from the median sagittal plane, the sectional area of the RCPma was 186.34± 55.02 mm2 on the left, and 202.35± 59.76 mm2 on the right. The sectional area of OCI was 221.72± 68.99 mm2 on the left, and 224.92± 61.34 mm2 on the right; At the section with 30-degree bias from the oblique sagittal plane, the sectional area of RCPma was 183.30± 42.24 mm2 in males, and 133.05± 26.44 mm2 in females. The sectional area of OCI was 254.81± 46.20 mm2 in males, and 167.42± 27.85 mm2 in females. Significant sex difference exists in the sectional areas of the RCPma and OCI, the values of the male subjects were predominantly larger (P < 0.05), however there were no age- related significant difference. The sectional area of RCPma is bilateral asymmetric, the RCPma on the right side is larger than that of the left side (P < 0.05), but the OCI is bilaterally symmetric (P >0.05). The MRI image features, imaging anatomical data and sexual dimorphism of the RCPma and the OCI are presented in this study. This imaging anatomical data will be useful for functional and clinical studies on the RCPma, OCI, and the MDB.

Muscular-stage Dissection during Far Lateral Approach and Its Transcondylar Extension.

Background The far lateral approach includes exposure of the C1 transverse process, vertebral artery, posterior arch of the atlas, and occipital condyle. We designed a method for systematic muscular-stage dissection and present our experience with this approach. Operative Methods We used a horseshoe scalp flap that was reflected downward and medially. The lateral muscle layers were separated layer to layer to expose the suboccipital triangle. The medial muscle layers were separated in the midline and reflected in a single layer. At this stage, the midline of the C1 process and the foramen magnum were identified. The rectus capitis posterior major muscle was reflected to expose the posterior arch of the atlas. The C1 transverse process and vertebral artery were identified by reflection of the superior oblique muscle. The occipital condyle was separated accordingly. Results We used this method of muscular dissection in 10 patients (foramen magnum meningioma, n = 5; hypoglossal schwannoma, n = 2; others, n = 3). Systematic muscular-stage dissection facilitates identification of the anatomical landmarks with no vertebral artery injury. Gross total removal was obtained in all 9 patients with complex tumors. The patient with vertebral artery dissection successfully underwent proximal clipping. Conclusion Our muscular-stage dissection could contribute to safe and effective surgery for the far lateral approach.

The second terminations of the suboccipital muscles: An assistant pivot for the To Be Named Ligament.

In the last two decades, many studies have focused on the muscles and dense connective tissues located in the suboccipital region. Our study investigated the existence of the second terminations originating from the suboccipital muscles, and the relationship between the variable types of the To Be Named Ligament (TBNL). Anatomical dissection was performed on 35 head-neck specimens. The existence of the second terminations of the suboccipital muscles was confirmed and various types of the TBNL were observed in this study. The second terminations originated from multiple suboccipital muscles including the rectus capitis posterior minor (RCPmi), rectus capitis posterior major (RCPma) and obliquus capitis inferior (OCI) muscles, merged and terminated at the TBNL. The overall incidence of the second terminations of the suboccipital muscles was 34.29% and it varied among the various suboccipital muscle origins. 28.57% of the second terminations originated from the RCPma; 11.43% was from the RCPmi and 8.57% was from the OCI. Furthermore, there was a significant relationship between the existence of second terminations and the particular type of the TBNL. 95% of the arcuate type of the TBNL was accompanied with the second terminations which attached to their turning part, whereas only 10% of all the radiate type of the TBNL was accompanied with the second terminations. This study for the first time described the second terminations originating from multiple suboccipital muscles and demonstrated the relationship with the various types of the TBNL. We speculated that the second terminations maintain the arcuate TBNL and transfer tensile forces to the Myodural Bridge (MDB), thereby modulating the physiological functions of the MDB.

Morphological classification and comparison of suboccipital muscle fiber characteristics.

In an attempt to clarify the function of the suboccipital muscles, we performed morphological observation of the suboccipital muscles for variations in the muscle belly and compared the morphology of their muscle fibers in terms of cross-sectional area by immunostaining with anti-myosin heavy chain antibodies. The cadavers of 25 Japanese individuals were used: 22 for morphological examinations and three for histological examinations. Among samples of the rectus capitis posterior major muscle (RCPma) and rectus capitis posterior minor muscle (RCPmi), 86.4% had a typical muscle appearance with a single belly, and 13.6% had an anomalous morphology. None of the samples of the obliquus capitis superior (OCS) or obliquus capitis inferior (OCI) muscles had an anomalous appearance. Measurement of cross-sectional area revealed that fast-twitch muscle fibers in the RCPma and OCI had a significantly greater cross-sectional area than those of the RCPmi and OCS. The cross-sectional area of intermediate muscle fibers was also significantly greater in the OCS than in the RCPma, RCPmi, and OCI. The cross-sectional area of slow-twitch muscle fibers was significantly greater in the OCS than in the RCPma, RCPmi, and OCI, and the RCPmi showed a significantly greater cross-sectional area for slow-twitch muscle fibers than did the RCPma, and OCI. Our findings indicate that the RCPmi and OCS exert a greater force than the RCPma and OCI, and act as anti-gravity agonist muscles of the head. Prolonged head extension in individuals with anomalous suboccipital muscle groups could result in dysfunction due to undue stress.

Anatomical study of neck back muscle and spinal nerve dorsal rami

Objective To provide the microanatomy for surgical operation for spastic torticollis.Methods Through the anatomy research of adult embalmed cadaver (8 cases,16 sides) to description the layer、course、beginning and ending points of muscle and the ramification course、distribution and diameter of spinal nerve dorsal rami nerve.Results Neck back muscles can be divided into four layers.The first layer are trapezius muscle and sternocleidomastoid; The second are splenius capitis muscle、splenius cervicis and levator scapulae muscle; The third layer are semispinalis capitis muscle、semispinalis cervicis muscle and longissimus capitis muscle; The last layer are obliquus capitis superior、obliquus capitis inferior、rectus capitis posterior major and rectus capitis posterior minor.Except C1 、C2 the others dorsal branch of spinal nerve are traveling backward.The diameter of the dorsal branch(mm):Left C1:0.87-1.62 mm(1.28 ±0.33) mm;C2:2.64-3.92 mm(3.12 ±0.49) mm;C3:1.56-2.11 mm(1.79 ±0.20) mm;C4:0.91-1.98 mm(1.41 ±0.46)mm;C5:0.92-1.39 mm(1.16 ±0.19)mm;C6:0.93-1.36 mm (1.14 ±0.24)mm.Right C1:0.92-1.49 mm(1.23 ±0.23) mm;C2:2.81-3.93 mm(3.19 ±0.43) mm; C3:1.52-1.92 mm (1.72 ± 0.17) mm ; C4:1.02-2.01 mm (1.42 ± 0.39) mm ; C5:0.89-1.63 mm (1.17 ± 0.31) mm; C6:0.81-1.39 mm (1.17 ± 0.23) mm.The C2-6 spinal nerve dorsal rami can be observed in the gap between semispinalis capitis and semispinalis cervicis muscle.Accessory nerve at a distance about 2 cm where great auricular nerve pierce the back edge of stemocleidomastoid muscle,the accessory nerve appear in the posterior cervical triangle.The diameter of accessory nerve which pierce the back edge of stemocleidomastoid muscle is 1.93-2.37 mm(2.10 0.18)mm (Left) ; 1.89-2.23 mm (2.09 0.14)mm (Right).Conclusions The above-mentioned anatomic relations of neck back muscles and spinal nerves can be provided foundation for post-cranial and neck surgery.Especially for the spinal nerve dorsal branch cut to treatment spastic torticollis provide an important reference. Key words: Neck back muscles; Dorsal branch of spinal nerve; Accessory nerve

Activation of Rectus Capitis Posterior Major Muscles During Voluntary Retraction of the Head in Asymptomatic Subjects

ObjectiveThe purpose of this study was to assess levels of electromyographic activity measured from rectus capitis posterior major (RCPM) muscles of asymptomatic subjects as their heads moved from a self-defined neutral position to a retracted position. MethodsA 2 × 2 within-subjects factorial research design was used. Disposable, intramuscular electrodes were used to collect electromyographic data from asymptomatic subjects between the ages of 20 and 40 years old. Data analysis was performed using mixed effects β regression models. ResultsActivation of RCPM muscles was found to significantly increase (P < .0001) as the head moved from a self-defined neutral position to a retracted position. Rectus capitis posterior major muscle activation levels, measured as a function of head position, have not been previously reported. ConclusionsThe findings from this study showed that RCPM muscle activation significantly increases during voluntary retraction of the head.

Histological analysis of the rectus capitis posterior major's myodural bridge

Background contextIn recent literature, a soft-tissue communication between the rectus capitis posterior major (RCPma) muscle and the cervical dura mater has been identified. To the best of our knowledge, this communication has yet to be validated from a histological perspective nor has it been examined for neural tissue. PurposeThe purpose of this study was to examine the composition and true continuity of the communication between the RCPma and the dura mater at a microscopic level. The communication was also inspected for the presence of proprioceptive neurons. Study designAn anatomical and histological analysis of a novel structure in the atlantoaxial interspace. MethodsGross dissection was performed on 11 cadavers to remove the RCPma, the soft-tissue communication, and a section of posterior cervical dura mater as one continuous unit. Paraffin embedding and sectioning followed by hematoxylin and eosin staining was conducted to validate the connection. Staining with antineurofilament protein fluorescent antibodies was performed to identify proprioceptive neural tissue on one specimen, and all findings were recorded via photographic documentation. ResultsHistological investigation revealed a tendinous matrix inserting into both the RCPma and the posterior aspect of the cervical dura mater in all 11 specimens. In the one specimen examined for neural tissue, antineurofilament protein fluorescence revealed proprioceptive neurons within the communication. Immunoperoxidase staining demonstrated the insertion of these neurons into both the dura mater and the belly of the RCPma. ConclusionsThe existence of a true connection between the RCPma and the cervical dura mater provides new insight in understanding the complex anatomy of the atlantoaxial interspace. The presence of a neural component within this connection suggests that it may serve another function aside from simply anchoring this muscle to the dura mater. Such a connection may be involved in monitoring dural tension and may also play a role in certain cervicogenic pathologies. This study also supports previous reports that no true membrane joins the posterior arch of the atlas to the laminae of the axis and contradicts the conventional belief that the ligamentum flavum joins these two structures.

Endoscopic far-lateral approach to the posterolateral craniovertebral junction: an anatomical study

Minimally invasive surgery to the posterolateral craniovertebral junction (CVJ) has not been sufficiently described. The aims of this study were to evaluate the feasibility of an endoscopic far-lateral approach to the posterolateral craniocervical junction and to better understand the related anatomy under distorted endoscopic view. Ten fresh cadavers were studied with 4-mm 0° and 30° endoscopes to develop the surgical approach and to identify surgical landmarks. After making a 3-cm straight incision behind the mastoid process, the superior oblique and rectus capitis posterior major muscles were partially exposed. An endoscope was then introduced and the two muscles were followed inferiorly until the posterior arch of the atlas appeared. The two muscles were removed to create ample working space without violating the posterior atlanto-occipital membrane. The vertebral artery was identified by the landmark of the posterior arch of the atlas, and the atlanto-occipital joint and foramen magnum were exposed. In addition to suboccipital craniectomy, transcondylar, supracondylar, and paracondylar extension by drilling were applicable through the narrow corridor under superb visualization. The intradural neurovascular structures from the acousticofacial bundle to the dorsal root of C2, anterolateral space of the foramen magnum, cerebellomedullary fissure, and fourth ventricle were clearly demonstrated. This endoscopic far-lateral approach offers excellent exposure of surgical landmarks around the posterolateral CVJ with minimal invasiveness. Endoscopic soft tissue dissection is key to creating the surgical corridor. This approach could offer an alternative to the conventional far-lateral approach in selected cases.

Anatomical Connection Between the Rectus Capitis Posterior Major and the Dura Mater

Anatomic study performed on 13 cadaveric specimens focused on muscles of the suboccipital triangle, specifically, the rectus capitis posterior major (RCPma). To investigate a connection between the RCPma and the cervical dura mater. In a study of the posterior intervertebral spaces, a connection between the RCPma and the dura mater was briefly described. To the best of our knowledge, no study has been conducted specifically on this communication. Anatomic dissections were performed in the suboccipital regions of 13 embalmed, adult cadaveric specimens. Findings were recorded via photographic documentation. In 11 of the 13 specimens, the RCPma attached to the spinous process of the axis and then continued to establish a gross anatomical connection with the dura mater in the atlantoaxial interspace. Manual traction of the RCPma resulted in gross dural movement from the spinal root level of the axis to the spinal root level of the first thoracic vertebra. A connection was found to exist between the RCPma and the cervical dura mater. Various clinical manifestations may be linked to this anatomical relationship.

上位頚髄病変に対する筋層温存手術

The adequate expansion of C1 and C2 spinal canal is required for the treatment for upper cervical spinal cord lesion. Conventional axial laminectomy and laminoplasty can cause postoperative cervical malalignment and axial neck pain. These complications are serious, especially for younger patients, who can be subjected to progressive kyphotic deformities. Complete opening of these laminae is not necessarily demanded for the degenerative cervical disease such as cervical spondylosis, disc hernia and ossification of posterior longitudinal ligament. C2 decompression can be achieved by bell-shape osteotomy through large C2 spinous process, or undermining one of C2 from caudal edge. However, complete laminar opening is needed for upper cervical spinal tumor, especially large intradural spinal tumor or intramedullary cord tumor. The authors developed the laminar opening and reconstruction with all the muscular attachment undisturbed for upper cervical spinal cord lesion including C1-2. The secure of intermuscular space for lateral gutter is key procedure after midline splitting of C1-2. In C1, the lateral gutter is secured between rectus capitis posterior major (RCPMa) and minor muscle, or between RCPMa and obliquus capitis inferior muscle (OCI). In C2, it is secured between OCI and semispinalis cervicis muscle. The laminar flap is opened with all the muscular attachment maintained. Sufficient operative field was acquired, and make intradural manipulation easier. Muscle-preserving laminoplasty is completed with or without hydroxyapatite implant. We introduced these procedures in detail, and verified the concept of musculo-skeletal preservation under the pre-and post-operative evaluation of muscular layers related with C1 and C2.