Posterior Atlanto-occipital Membrane Research Articles

The Application of the Posterior Atlanto-Occipital Membrane Tension Release Technique for Surgical Exposure of the Horizontal Part of the Vertebral Artery's Third Segment: An Anatomical and Clinical Investigation.

This study aims to elucidate the anatomical principles governing the surrounding venous structures (VS) of the horizontal part of the third segment of the vertebral artery (V3h) and develop a safe and bloodless surgical technique for exposing V3h. This study used 10 formalin-infused cadaveric head specimens. The dissections were performed stepwise to simulate the far lateral approach process, exposing the V3h with a novel technique. Additionally, we applied this technique to 10 patients undergoing far or extreme lateral approaches. The VS surrounding V3h is divided into 3 components: the vertebral venous plexus, suboccipital cavernous sinus, and the anastomotic vein. The posterior atlanto-occipital membrane (PAOM), a resilient fascial layer in the craniovertebral junction, extends from the periosteum of the occipital squama to the posterior arch of the atlas. It adheres ventrally to the VS within the suboccipital triangle (SOT), forming a tent-like structure that maintains tension and ensures fullness of the VS around V3h. We discovered that by releasing tension in this membrane and reducing strain on this tent-like structure, the collapse of the venous sinus within the SOT can be achieved, resulting in reduced intraoperative bleeding and improved surgical efficiency. Additionally, we successfully managed 10 clinical cases employing the PAOM tension release technique in clinical cases, with no reported incidents of intraoperative vertebral artery injury. The application of the PAOM tension release technique effectively collapses the tent-like structure within the SOT, significantly reducing bleeding during V3h exposure in craniovertebral junction.

Prognostic Significance of Central Skull Base Remodeling in Chiari II Malformation.

Outward convexity of the basiocciput and posterior atlanto-occipital membrane are common in patients with Chiari II malformation associated with an open neural tube defect. We aimed to determine if the severity of these findings correlated with the need for future hydrocephalus treatment. A retrospective chart and imaging review identified patients who underwent open neural tube defect repair at a quaternary care pediatric hospital from July 2014 through September 2022. Patients were classified by the need for hydrocephalus treatment and whether they received prenatal or postnatal neural tube defect repair. Measurements of imaging parameters related to posterior fossa maldevelopment and skull base remodeling were performed. Compared with 65 patients who did not require hydrocephalus treatment, 74 patients who required treatment demonstrated statistically significantly greater mean basiocciput convexity (P < .001). While the mean basiocciput length in the hydrocephalus treatment group was smaller (P < .001), the ratio of basiocciput convexity to length was larger (P < .001). Notably, 100% of patients with a basiocciput convexity of ≥4 mm required hydrocephalus treatment. The mean posterior atlanto-occipital membrane convexity was significantly greater for patients who required hydrocephalus treatment in the postnatal group (P = .02), but not the prenatal group (P = .09). Pediatric patients with Chiari II malformation who ultimately required surgical hydrocephalus treatment had greater outward convexity of the basiocciput but had greater posterior atlanto-occipital membrane outward convexity only if the repair was performed postnatally. Together these measurements may be useful in predicting the need for hydrocephalus treatment.

Morphological and ultrastructural investigation of the posterior atlanto-occipital membrane: Comparing children with Chiari malformation type I and controls.

The fibrous posterior atlanto-occipital membrane (PAOM) at the craniocervical junction is typically removed during decompression surgery for Chiari malformation type I (CM-I); however, its importance and ultrastructural architecture have not been investigated in children. We hypothesized that there are structural differences in the PAOM of patients with CM-I and those without. In this prospective study, blinded pathological analysis was performed on PAOM specimens from children who had surgery for CM-I and children who had surgery for posterior fossa tumors (controls). Clinical and radiographic data were collected. Statistical analysis included comparisons between the CM-I and control cohorts and correlations with imaging measures. A total of 35 children (mean age at surgery 10.7 years; 94.3% white) with viable specimens for evaluation were enrolled: 24 with CM-I and 11 controls. There were no statistical demographic differences between the two cohorts. Four children had a family history of CM-I and five had a syndromic condition. The cohorts had similar measurements of tonsillar descent, syringomyelia, basion to C2, and condylar-to-C2 vertical axis (all p>0.05). The clival-axial angle was lower in patients with CM-I (138.1 vs. 149.3 degrees, p = 0.016). Morphologically, the PAOM demonstrated statistically higher proportions of disorganized architecture in patients with CM-I (75.0% vs. 36.4%, p = 0.012). There were no differences in PAOM fat, elastin, or collagen percentages overall and no differences in imaging or ultrastructural findings between male and female patients. Posterior fossa volume was lower in children with CM-I (163,234 mm3 vs. 218,305 mm3, p<0.001), a difference that persisted after normalizing for patient height (129.9 vs. 160.9, p = 0.028). In patients with CM-I, the PAOM demonstrates disorganized architecture compared with that of control patients. This likely represents an anatomic adaptation in the presence of CM-I rather than a pathologic contribution.

Frequency of Ponticulus posticus and Ponticulus lateralis in patients admitted to hospital with traumatic brain injur

To determine the frequency of Ponticulus posticus and Ponticulus lateralis among patients admitted to a24-hour emergency hospital. The study included 2887 patients with a traumatic history who were admitted to the hospital for emergency reasons. This principle of sampling allowed us to exclude a high concentration of studies of patients with chronic neurological diseases, the cause of which could be symptomatic Kimmerle's anomaly (KA). During the period 01.01.20 to 31.12.20, primary CT was performed on an emergency basis in 7348 patients. Of these, CT scans of the brain and cervical spine were performed in 2965 patients. Some patients (78 people) were excluded from the study due to the presence of cervical vertebral fractures and metal artifacts in the craniovertebral region. The Ponticulus posticus was detected in 1162 (40.2%) patients, among them class 3 and 4 was detected in 27.7%, and class 2 ossification in 12.5%. This Ponticulus posticus was significantly more common (χ2 test, p=0.0005) in men. The Ponticulus lateralis was identified in 231 patients (8%), among them 94 patients (3.3%) had complete ponticulus on both sides, 29 patients (1%) - on one side, and 108 patients (3.7%) - two-sided incomplete ponticulus. In patients with class 2-3-4, Ponticulus lateralis were detected significantly more often (χ2 test, p<0.0001). The cumulative incidence of KA was 42%, 17% of patients are carriers of a complete KA bridge, which is significantly higher than in the European or Asian regions. The data suggest that KA is not the result of ossification of the posterior atlanto-occipital membrane, since different classes of KA occur equally often at different ages. Further studies of KA are needed, including its occurrence in patients of the neurological department and its correlation with individual neurological syndromes to determine the need for surgical treatment in the population.

Full-endoscopic technique for posterior fossa decompression in Chiari malformation type I: An anatomical feasibility study in human cadavers.

Although endoscope-assisted techniques have been described, a full-endoscopic approach is yet to be performed for posterior fossa decompression (PFD) in Chiari malformation type I (CM-I). This study aims to describe the full-endoscopic PFD technique and evaluate its feasibility. Five fresh-frozen anonymized adult human cadavers were operated on using an endoscope with an oval shaft cross-section with a diameter of 9.3 mm, a working length of 177 mm, and a viewing angle of 20°. It also had an eccentric working channel with a diameter of 5.6 mm, a light guide, a sheath for continuous irrigation, and a rod lens system. The instruments were introduced from the working channel. Posterior craniocervical structures were dissected, and PFD was achieved. The planned steps were performed in all five cadavers. The endoscope was introduced to the posterior craniocervical region, dissecting the structures to easily expose the suboccipital bone and C1 posterior arch. Important structures, such as the C1 posterior tubercle, rectus capitis posterior minor muscles, and posterior atlantooccipital membrane, were used as landmarks. PFD was feasible even with the dural opening. Using the full-endoscopic approach, posterior craniocervical structures can be reached, and PFD can be performed successfully. The instruments used are well-defined for spinal usage; thus, this full-endoscopic technique can be widely used in the surgical treatment of patients with CM-I.

A Neglected Normal Anatomical Structure in Mammal: A Study in Bats and Tree Shrews

The myodural bridge is a dense connective tissue connecting muscles and ligaments to the spinal dura mater in the atlanto-occipital interspace. Some researchers believe that the myodural bridge may play a vital physiological role. It is possible, for instance, that the prevention of spinal dura mater infoldings might be involved in regulated cerebrospinal fluid circulation. For instance, it is possible to prevent spinal dura mater infoldings, regulating cerebrospinal circulation. Bats are nocturnal and the only mammals that can perform a genuine and sustained flight, whereas tree shrews are arboreal mammals that often climb to a high altitude of about 10,000 feet. Both animals have lifestyles that are different from other previously studied mammals. The study of these two animals will shed further light on the existence of the myodural bridge in mammals. Gross anatomical dissection was used to observe the connections between the deep muscles of the neck and the dura mater at the level of the atlanto-occipital interspace. The existing structures were analyzed using conventional and special histological staining techniques. The suboccipital regions in bats and tree shrews contained the rectus capitis dorsal major (RCDma), rectus capitis dorsal minor (RCDmi), oblique capitis anterior (OCA), and oblique capitis posterior (OCP). Dense connective tissue connects the RCDmi to the posterior atlanto-occipital membrane (PAOM) and the latter to the spinal dura mater. The myodural bridge in these mammals shares a similar structure to the myodural bridge in humans. Histological analyses confirmed that the connective fibers of the myodural bridge were primarily type I collagen fibers. In this study, it is supplemented by the existence of the myodural bridge in mammals. This further demonstrates that myodural bridge widely exists in the normal anatomy of mammals. This provides morphological support for a comparative anatomical study of the physiological function of the myodural bridge.

MORPHOMETRIC ANALYSIS OF ATLAS AND IT'S CLINICAL SIGNIFICANCE: AN ANATOMICAL STUDY OF INDIAN HUMAN ATLAS VERTEBRA.

The atlas and axis are unique in their morphology and also have a complex vertebral artery relationship.The atlas consists of a neurovascular groove for the vertebral artery located behind each lateral mass at the posterior arch of the atlas. Superiorly the vertebral groove is arched by the posterior atlanto-occipitalmembrane, leaving an opening for the upwards passage of the vertebral artery and the outwards passage of the rst cervical spinal nerve. This prospective observational study was conducted in the Department of Anatomy, Government Medical College, Jammu, a total of 40 dry adult atlas vertebrae were measured with the aim to study the morphology of Indian human atlas vertebra and it's clinical signicance. The mean±SD and range of various parameters of atlas were recorded. It was observed that there was no signicant difference between right and left sides which shows bilateral symmetry. The study concluded that various parameters of atlas are helpful for the different neurosurgeries mainly in the surgical procedures of traumatic neck condition to prevent further injuries to vertebral artery and spinal cord

The Prevalence, Classification, and Potential Clinical Implications of Anatomical Variations of First Cervical Vertebra

Background: First cervical vertebra has different anatomical features than other cervical vertebrae. It holds globe of skull and lacks body and spine. It is composed of 2 lateral masses linked by anterior and posterior arches. Posterior atlanto-occipital membrane is attached to posterior arch whose lateral edge sometimes ossifies thus converting groove into canal. Consequently, neurovascular groove gets converted into a bony ring “ponticulus posticus”. It can cause of neck pain and headache. Knowledge of this variation is important during various orthopedic procedures involving atlas including C1 lateral mass screw placement. Congenital defects of atlantal arch a developmental failure of chondrogenesis is a rare anomaly. These defects are a benign variation discovered incidentally. Detection of these anomalies is clinically important as they can cause acute neurologic deficits, which is associated with neck extension. Study was done: To determine the prevalence of Ponticulus Posticus and to report the frequency of various types of congenital malformations of the atlantal arch. Methodology: 250 computerized tomography (CT) head and neck in axial and sagittal sections from Picture Archiving and Communication System (PACS) of Dr RMLIMS, Lucknow was studied as CT is the best method to study the bony landmarks and any anomaly. Prevalence of variations was calculated. Data was analyzed statistically using SPSS version 21 by Chi-square test. Result: Prevalence of ponticulus posticus was 32.4%. Males had higher prevalence (20.4%) than females (12%). Incomplete ponticulus posticus (24.4%) was more than complete variant (8%). There was predominance of left sided ponticulus posticus(12% vs 8.4%) Deficient posterior arch was found in 9(3.6%) cases. 6 were of type A 3 were of type B. Conclusion: This study will help in determining cause of neurological deficit in patients due to presence of above variations.

Kimmerle anomaly as a cause of extravasal compression of the vertebral artery

Kimmerle anomaly, also known as ponticulus posticus, is a commonly known variant of the atlas anatomy. It occurs as a result of complete or incomplete ossification of the posterior atlanto-occipital membrane over the groove of the vertebral artery, which leads to the formation of an arcuate foramina containing the vertebral artery and the posterior branch of the C1 spinal nerve. This anatomical variation is associated with symptoms of vertebrobasilar insufficiency, various types of headache, visual impairment, photopsia, syncope, drowsiness, reduced work capacity, unsteady gait, sleep disturbance, panic attacks.Objective of the article is to highlight the attention of physicians on the widespread and not well understood Kimmerle anomaly, which is the cause of ischemic disorders in the vertebrobasilar circulation due to extravasal compression of the vertebral arteries.In the case of signs of impaired blood flow in the vertebrobasilar circulation, an X-ray of the cervical spine has to be done. In case of Kimmerle anomaly, ultrasound of neck vessels and transcranial doppler with functional tests should be performed. In the case of significant influence of disorder on the vertebrobasilar circulation, computed tomography with angiography is mandatory. If the patient's large vertebral artery is compressed, indications for surgical decompression of the vertebral artery at the level of the atlas is indicated. In cases of mild symptoms of cerebral vertebrobasilar circulation, symptomatic medication, wearing a Chance collar, physical therapy, and regimen restrictions are prescribed.

Interrelationship Between Craniocervical Dissociation Spectrum Injuries and Atlantoaxial Instability on Trauma Cervical MRI Examinations.

Background and purpose Craniocervical dissociation injuries encompass a spectrum of osteoligamentous injuries between the skull base and C1-C2 that may be treated via prolonged external immobilization versus occipital cervical fusion depending on the risk of persistent craniocervical instability. However, the presence of atlantoaxial instability (AAI) at C1-C2, as determined by transverse atlantal ligament (TAL) integrity with or without a C1 fracture, may guide the neurosurgical management of craniocervical dissociation spectrum injuries (CDSI) since it implies an overall greater degree of instability at the craniocervical junction (CCJ). Materials and methods Adult trauma patients who suffered a transverse atlantal ligament injury on cervical magnetic resonance imaging (MRI) were identified retrospectively. The cervical computed tomography (CT) and magnetic resonance imaging examinations for these patients were reviewed for additional traumatic findings. Demographic information, treatment, and outcome information were recorded. Results Twenty-nine trauma patients presented to the emergency department (ED) with an acute, midsubstancetransverse atlantal ligament tear on cervical magnetic resonance imaging. Thirty-one percent of patients demonstrated a tear in at least one major craniocervical ligament (atlanto-occipital capsular ligaments, alar ligaments, and tectorial membrane {TM}) with 14% demonstrating a tear in two major craniocervical ligamentsand no patients demonstrating a tear in all three major craniocervical ligaments. Minor craniocervical ligament injuries (anterioratlanto-occipital membrane complex {AAOMc} and posterior atlanto-occipital membrane complex {PAOMc}) were common and observed in 76% of patients. Conclusions Our study suggests that multiple major craniocervical junction ligamentous injuries on cervical magnetic resonance imaging are relatively uncommon in the setting of transverse atlantal ligament injury.

The relationship between compensatory hyperplasia of the myodural bridge complex and reduced compliance of the various structures within the cranio-cervical junction.

The myodural bridge complex (MDBC) is described as a functional anatomic structure that involves the dense connective tissue fibers, muscles, and ligaments in the suboccipital region. It has recently been proposed that the MDBC can influence cerebrospinal fluid (CSF) circulation. In the present study, bleomycin (BLM), a type of antibiotic that is poisonous to cells, was injected into the posterior atlanto-occipital interspace (PAOiS) of rats to induce fibrous hyperplasia of structures in PAOiS. Sagittal sections of tissues obtained from the posterior-occipital region of the rats were stained utilizing the Masson Trichrome staining method. Semiquantitative analysis evidenced that the collagen volume fraction of collagen fibers of the MDBC, as well as the sum of the area of the spinal dura mater and the posterior atlanto-occipital membrane in the BLM group were significantly increased (p < .05) compared to that of the other groups. This finding illustrates that the MDBC fibers as well as other tissues in the PAOiS of rats in the BLM group developed fibrotic changes which reduced compliance of the spinal dura mater. Indeed, the sectional area of the rectus capitis dorsal minor muscle in the BLM group was measured to be increased. These changes may further restrict CSF flow. The present research provides support for the recent hypothesis proposed by Labuda et al. concerning the pathophysiology observed in symptomatic adult Chiari malformation Type I patients, that there exists a relationship between the altered compliance of the anatomic structures within the craniocervical region and the resultant compensatory hyperplasia of the MDBC.

Unilateral atlanto-occipital injury: A case series and detailed radiographic description.

ContextAtlanto-occipital dissociation is a highly lethal ligamentous injury at the craniocervical junction (CCJ). Previous studies have described rare cases of milder forms of atlanto-occipital injury (AOI) which might be managed nonoperatively, but there is a paucity of literature on this subject.Aims:We retrospectively reviewed our institutional experience to characterize the injury patterns, treatments, and clinical courses of patients with unilateral AOI.Methods:We included patients with radiographic evidence of unilateral occipitocervical joint capsular disruption, distraction, or edema ± injury of the apical ligament, tectorial membrane, anterior atlanto-occipital membrane, posterior atlanto-occipital membrane, alar ligaments, or cruciate ligament. The long-term outcomes were gathered from medical records, and six patients were available for Neck Disability Index via phone call at the time of the study.Results:Eight patients were included in the study. The mean age was 45.1 years ± 26.5. Causes of trauma included motor vehicle collision for five patients (5/8, 62.5%), falls for two (2/8, 25), and assault for one (1/8, 12.5%). All patients had a widened condyle-C1 interval >2 mm. Three patients underwent occipitocervical fusion, one patient underwent atlantoaxial fusion, and another received subaxial fusions for other injuries. Three patients underwent no surgical intervention. All patients were seen at least once as an outpatient following hospital discharge. There were no delayed neurologic injuries or deaths.Conclusions:We propose that ligamentous injury at the CCJ functions more as a spectrum rather than dichotomous diagnosis, of which a subset can likely be safely managed nonoperatively.

Arcuate Foramen: An Anatomical Variation in the Atlas Vertebrae

Background: Arcuate foramen is a variation in the posterior arch of atlas vertebrae. It is commonly called as Kimmerle’s anomaly, also known as Ponticulus Posticus. It is the product of the complete or incomplete ossification of the posterior atlantooccipital membrane over the vertebral artery groove resulting in the formation of arcuate foramen containing the vertebral artery and the posterior branch of the first cervical spinal nerve. Aims: The aim of the present study was to identify the percentage of incidence of arcuate foramen in the atlas and its clinical important. Materials and Methods: The study was conducted in the Department of Anatomy, Katihar Medical College, Katihar, India with 32 adult dried atlas vertebrae. Results: We found four (12.5%) atlas with arcuate foramen. One atlas having complete arcuate foramen and three having partial complete arcuate foramen. Conclusion: Awareness of this type of variation is very important for neurosurgeons and radiologist during their clinical practice. The presence of the arcuate foramen would also complicate screw placement during surgery. Clinical prescreening for signs of vertebrobasilar insufficiency is important for chiropractic and manual therapies. KEYWORDS: Atlas, Variation, Arcuate foramen, Vertebral artery, Atlantooccipital membrane.

The Posterior Atlantooccipital Membrane: The Anchor for the Myodural Bridge and Meningovertebral Structures.

Introduction: Sheet plastination has provided evidence that the posterior atlantooccipital membrane attaches to the dura’s posterior sleeve at the cerebrospinal junction. These findings contradict the traditional anatomical description of this membrane extending from the atlas’ posterior arch to the foramen magnum.Methods: A total of 16 plastinated cadavers were studied to evaluate the in situ and gross configuration of the posterior atlantooccipital membrane. Fifteen cadavers underwent sheet plastination, and one head was hemisected and plastinated. In all specimens, stereomicroscopy was used to evaluate the posterior atlantooccipital membrane and related structures within the intervertebral and epidural spaces.Results: In all 16 specimens, the posterior atlantooccipital membrane extending from the occiput, merged with the craniocervical dura mater, and formed a membrane-dura complex that ended at the level of the third cervical vertebra. The superior and inferior myodural bridge coalesced with their respective vertebrodural ligaments and fused with the posterior atlantooccipital membrane at their respective interspaces.Conclusion: The median aspect of the posterior atlantooccipital membrane does not directly communicate with the posterior arch of the atlas. Instead, the posterior atlantooccipital membrane converges with the craniocervical dura mater and terminates at the level of the third cervical vertebra. This membrane-dura complex serves as a common attachment site for the myodural and vertebrodural structures.

The segmentation of the vertebral artery: An ambiguous anatomical concept.

The course of the vertebral artery from its subclavian artery origin up to its termination at the vertebrobasilar junction is divided into four segments (V1-V4). This segmentation, based on schemes that have evolved since the late nineteenth century, should be a consistent and reproducible anatomical concept. However, the current literature offers conflicting definitions of that scheme, not infrequently within a single article or monograph. The principal inconsistency found in modern publications concerns the termination of the V2 segment, which is either set at the C2 or C1 transverse foramen depending on the scheme considered. Consequently, the portion of the vertebral artery extending between C2 and C1-a frequent site of pathological involvement-either belongs to the V2 or V3 segment. This discrepancy can affect the validity of studies evaluating the diagnosis and management of vertebral artery disorders. A V3 segment extending from the transverse foramen of C2 to the posterior atlanto-occipital membrane and subdivided into vertical, horizontal, and oblique subsegments-a pattern suggested by Barbieri in 1867 and adopted in some modern publications-would provide a simple, precise, and reliable solution without significantly altering the widely accepted division of the vertebral artery into four segments (V1-V4).

Ponticulus posticus upon routine evaluation of cervical spine x-ray in head injury patient: Case reports

Introduction: Ponticulus posticus or known as foramen arcuate is an anatomic variation of the first cervical vertebra origin from calcification of the posterior atlantooccipital membrane. The vertebral artery passes through this canal. This canal can be complete or incomplete and can also be unilateral or bilateral. Often related to symptoms of headaches, vertebrobasilar insufficiency, or acute hearing loss. Whereas, imaging studies show the presence of a partial osseous bridge on the upper surface of the atlas. This study aimed to present two cases of ponticulus posticus in head injury patients.Case presentation: We reported 2 cases of ponticulus posticus found incidentally in head injury patients at our institution. The patients were managed conservatively for 5 days and sent home with no neurological deficit and complication.Conclusion: Ponticulus posticus is often ruled out in pre-admission screening. Neurosurgeons should consider this to predict the neurological deficit.Keywords: foramen arcuate, head injury, ponticulus posticus, posterior atlantooccipital membrane

C1-C2 Dorsal Epidural Hematoma on Cervical Spine CT: A Novel Imaging Sign of Posterior Atlanto-Occipital Membrane Stripping Injury.

Background and Purpose: Identify patients with a dorsal epidural hematoma at C1-C2 and examine the major craniocervical junction ligaments for injury on follow-up magnetic resonance imaging.Materials and Methods: Adult and pediatric trauma patients who suffered a dorsal epidural hematoma at C1-C2 were identified using Nuance mPower software (Nuance Communications, United States). The cervical computed tomography and magnetic resonance imaging exams for these patients were reviewed for craniocervical junction osteoligamentous injuries. An age-matched control group was obtained.Results: Eight trauma patients were identified with a dorsal epidural fluid collection at C1-C2. All patients with a dorsal epidural hematoma, who underwent follow-up cervical magnetic resonance imaging demonstrated a stripping injury of the posterior atlanto-occipital membrane from the C1 posterior arch with increased short tau inversion recovery signal in the posterior atlanto-occipital membrane complex. Disruption of additional major craniocervcial ligaments on magnetic resonance imaging was relatively common with the most frequently associated ligamentous injuries involving the tectorial membrane (five patients) followed by the alar ligaments and anterior altanto-occiptial membrane (four patients each). Conclusions: A C1-C2 dorsal epidural hematoma is a rare injury that may be identified on cervical spine computed tomography but may be easily overlooked by the radiologist. We propose that a C1-C2 dorsal epidural hematoma is a direct result of a significant hyperflexion-hyperextension force with subsequent stripping of the posterior atlanto-occipital membrane from the posterior C1 arch. Trauma patients with a C1-C2 dorsal epidural hematoma on cervical spine computed tomography should undergo a cervical magnetic resonance imaging examination to evaluate the integrity of the posterior atlanto-occipital membrane complex and remaining craniocervical junction ligaments for injury.

Experience with osteoplastic posterior fossa craniotomy in 13 children

Abstract Background: Posterior fossa free bone flap craniotomy in children is being currently used, and it significantly decreases postoperative cerebrospinal fluid (CSF) leakage and pseudomeningoceles. However, sometimes bone displacement, bone resorption, osteonecrosis, or infection occurs in a few children after posterior fossa free bone flap craniotomy. So, in recent years, a few posterior fossa osteoplastic craniotomy techniques to overcome these complications have been described. Here, we are documenting our experiences with one of the previously described techniques of osteoplastic craniotomy, with some modification in cases of pediatric posterior fossa tumor. We called this described procedure “ligamentous osteoplastic midline posterior fossa craniotomy (LOM-PFC),” as it preserves the attachments of the posterior atlanto-occipital membrane. Materials and Methods: This LOM-PFC approach was implemented between 2018 and 2019 in 13 pediatric patients who were suffering from posterior fossa tumor. Perioperative and follow-up clinico-radiologic details were reviewed. Results: Only one patient had transient mild CSF accumulation, which was managed by lumbar punctures. A 3D reconstruction of computed tomography (CT) scan head verified a well-aligned and fused LOM-PFC flap during the postoperative and the follow-up period, respectively. Cosmetic results were excellent. The maximal follow-up period was one year. Conclusions: We found that the LOM-PFC approach had no added risk. It preserves the anatomy of the foramen magnum and allows more stable fixation of the bone flap, which minimizes the risk of CSF leakage, pseudomeningocele and finally reduces the hospital stay. This approach is easy to learn, feasible, and cosmetically effective.

An interesting case of dizziness: Bow Hunter's syndrome due to Kimmerle anomaly diagnosed with provocative DSA

BACKGROUND: Rotational occlusion of the vertebral artery known as Bow hunter's syndrome(BHS) is a very rare cause for transient vertebrobasilar insufficiency symptoms. Complete or incomplete ossification of the posterior atlantooccipital membrane is called a Kimmerle anomaly which causes symptom in only 5.5% of patients with this anomaly. Early diagnosis with high index of clinical suspicion and provactive digital substraction angiography aids in prompt surgical repair, relieving the patient from the disabling symptoms and avoiding unnecessary ineffective symptomatic therapies.

A Computed Tomographic Study to Document Anatomical Variations of First Cervical Vertebra: Prevalence, Classification and Possible Clinical Implications

Background - First cervical vertebra has different anatomical features as compared to other cervical vertebrae. It holds globe of skull and lacks body and spine. It is composed of 2 lateral masses linked by anterior and posterior arches. Posterior atlanto-occipital membrane is attached to posterior arch. Lateral edge of this membrane sometimes ossifies thus converting groove into canal. Consequently, neurovascular groove gets converted into a bony ring “ponticulus posticus”. It is considered as potential cause of neck pain and headache. Knowledge of this variation is important during procedures like instrumentation of atlas including C1 lateral mass screw placement which requires mobilization of C2 nerve root and screw insertion inferior to bony arch of atlas directly into lateral mass. In patients with ponticulus posticus, if not identified pre-operatively may give impression of wide bony arch for screw placement, which may result in vertebral artery injury due to a breach of this variation. Congenital defects of atlantal arch a developmental failure of chondrogenesis is a rare anomaly. These defects are a benign variation discovered incidentally. Detection of these anomalies is clinically important as they can cause acute neurologic deficits, which is associated with neck extension. Currarino et al proposed classification of posterior arch anomalies Type A Failure of posterior midline fusion of the 2 hemi arches. Type B Unilateral cleft. Type C Bilateral cleft with persistent dorsal part of arch. Type D Absence of posterior arch with persistent posterior tubercle. Type E Absence of entire posterior arch Objective Objectives this study is to find the prevalence of Ponticulus posticus Congenital anomalies of atlantal arch and classify them Material and Method- 250 computerized tomography (CT) head and neck in axial and sagittal sections from Picture Archiving and Communication System (PACS) of Dr RMLIMS, Lucknow was studied as CT is the best method to study the bony landmarks and any anomaly. Prevalence of variations was calculated. Data was analyzed statistically using SPSS version 21 by Chi-square test. Result- Prevalence of ponticulus posticus was 32.4%. Males had higher prevalence (20.4%) than females (12%). Incomplete ponticulus posticus (24.4%) was more than complete variant (8%). There was predominance of left sided ponticulus posticus(12% vs 8.4%) Deficient posterior arch was found in 9(3.6%) cases. 6 were of type A 3 were of type B. Conclusion- This study will help in determining cause of neurological deficit in patients due to presence of above variations. Significance Accurate evaluation of anatomic landmarks in patient with migraine or neck ache is important because changes in anatomy of atlas may be index pointing towards underlying disease process like vertebrobasilar insufficiency. Asymmetrical deviations of atlas in form, size, shape, and contour are often multiple and confusing. Therefore, they must not only be studied with care and precision and meticulously recorded. In our future project we plan to carry out computed tomographic study to find association of these variations in patients with migraine and cervical pain.