CT evaluation of Chamberlain's, McGregor's, and McRae's skull-base lines

Mobility Assessment Using Multi-Positional MRI in Children with Cranio-Vertebral Junction Anomalies

OBJECTIVE

This study aimed to assess the relevance of using multi-positional MRI (mMRI) to identify cranio-vertebral junction (CVJ) instability in pediatric patients with CVJ anomalies while determining objective mMRI criteria to detect this condition.

MATERIAL AND METHODS

Data from children with CVJ anomalies who underwent a mMRI between 2017 and 2021 were retrospectively reviewed. Mobility assessment using mMRI involved: (1) morphometric analysis using hierarchical clustering on principal component analysis (HCPCA) to identify clusters of patients by considering their mobility similarities, assessed through delta (Δ) values of occipito-cervical parameters measured on mMRI; and (2) morphological analysis based on dynamic geometric CVJ models and analysis of displacement vectors between flexion and extension. Receiver operating characteristics (ROC) curves were generated for occipito-cervical parameters to establish instability cut-off values. (3) Additionally, an anatomical qualitative analysis of the CVJ was performed to identify morphological criteria of instability.

RESULTS

Forty-seven patients with CVJ anomalies were included (26 females, 21 males; mean age: 10.2 years [3-18]). HCPCA identified 2 clusters: cluster №1 (stable patients, n = 39) and cluster №2 (unstable patients, n = 8). ΔpB-C2 (pB-C2 line delta) at ≥2.5 mm (AUC 0.98) and ΔBAI (Basion-axis Interval delta) ≥ 3 mm (AUC 0.97) predicted instability with 88% sensibility and 95% specificity and 88% sensitivity and 85% specificity, respectively. Geometric CVJ shape analysis differentiated patients along a continuum, from a low to a high CVJ motion that was characterized by a subluxation of C1 in the anterior direction. Qualitative analysis found correlations between instability and C2 anomalies, including fusions with C3 (body p = 0.032; posterior arch p = 0.045; inferior articular facets p = 0.012; lateral mass p = 0.029).

CONCLUSIONS

We identified a cluster of pediatric patients with CVJ instability among a cohort of CVJ anomalies that were characterized by morphometric parameters with corresponding cut-off values that could serve as objective mMRI criteria. These findings warrant further validation through prospective case-control studies.

Three-Dimensional-Printed Drill Guides for Occipitothoracic Fusion in a Pediatric Patient With Occipitocervical Instability

BACKGROUND

Pediatric occipitothoracic fusion can be challenging because of small size pedicles and thin occipital bone. Three-dimensional (3D) printing technology can help with accurate screw insertion but has not been described for occipital keel plate positioning so far.

OBJECTIVE

To describe the novel use of 3D technology to position occipital keel plates during pediatric occipitothoracic fixation.

METHODS

A young boy with segmental spinal dysgenesis presented with asymmetrical pyramidal paresis in all limbs. Developmental abnormities of the cervical spine caused a thinned spinal cord, and because of progressive spinal cord compression, surgical intervention by means of occipitothoracic fixation was indicated at the age of 3 yr.Because of the small-size pedicles and thin occipital bone, the pedicle screws and occipital plates were planned meticulously using 3D virtual surgical planning technology. The rods were virtually bent in order to properly align with the planned screws. By means of 3D-printed guides, the surgical plan was transferred to the operating theater. For the occipital bone, a novel guide concept was developed, aiming for screw positions at maximal bone thickness.

RESULTS

The postoperative course was uneventful, and radiographs showed good cervical alignment. After superimposing the virtual plan with the intraoperative acquired computed tomography, it was confirmed that the occipital plate positions matched the virtual plan and that pedicle screws were accurately inserted without signs of breach.

CONCLUSION

The use of 3D technology has greatly facilitated the performance of the occipitothoracic fixation and could, in the future, contribute to safer pediatric spinal fixation procedures.

Association between craniovertebral junction abnormalities and syringomyelia in patients with chiari malformation type-1

Objectives:

To assess the correlation between craniovertebral junction (CVJ) abnormalities and syringomyelia in patients with Chiari malformation type-1 (CM1).

Methods:

This was a retrospective study including patients with CM1. Identification of cases was done by searching a radiology database at a university hospital from 2012 to 2017. Patients were divided into 2 groups based on whether CVJ abnormalities were present (CVJ+) or absent (CVJ-). The patients’ demographic and clinical data were reviewed. All magnetic resonance imaging studies were examined by a certified neuroradiologist.

Results:

Sixty-four consecutive patients with CM1 were included. The mean age was 24±17 years; 59% were females. The CVJ+ group had more female patients (p = 0.012). The most frequent CVJ abnormality was platybasia (71%), followed by short clivus (44%) and cervical kyphosis (33%). The CVJ abnormalities were more in Syringomyelia cases (p = 0.045). However, the results were not significant when hydrocephalus cases were excluded.

Conclusion:

Among CM1 patients, CVJ abnormalities were found more in patients with syringomyelia. Future studies with larger sample size are required to further study the correlation between CVJ abnormalities and both syringomyelia and hydrocephalus in CM1 patients.

Anatomical evaluation of the craniovertebral junction on cone-beam computed tomography images

INTRODUCTION

There are many craniometric measurements that are used in evaluating craniovertebral junction (CVJ) pathologies such as basilar invagination, atlantoaxial dislocation and platybasia. Therefore, it is important to determine the normal reference range of the craniometric measurements. This study aims to determine the morphometric reference values of the bony structures in the CVJ from cone-beam computed tomography (CBCT) images of a group of South Eastern Anatolian population.

MATERIALS AND METHODS

The CBCT images of 300 individuals were retrospectively evaluated. 14 parameters on midsagittal and 2 parameters on the coronal plane were studied. The data were statistically evaluated.

RESULTS

Measurement results were found as follows; the distances between odontoid process (OP) and McGregor line as 0.31 ± 3.22 mm, OP and Chamberlain line 1.06 ± 3.22 mm, OP and McRae line 5.30 ± 1.59 mm, OP and Fischgold digastric line 8.70 ± 4.12 mm, OP and Fischgold bimastoid line - 5.15 ± 4.86 mm, length of McRae line 35.58 ± 2.52 mm, atlantodental interval 1.28 ± 0.48 mm, posterior atlantodental interval 19.54 ± 2.24 mm, basion axial interval 4.01 ± 1.83 mm, basion dental interval 4.92 ± 1.77 mm, length of Modified Ranawat line 28.66 ± 2.38 mm, length of Redlund-Johnell line 35.11 ± 4.09 mm, clivus canal angle 157.62° ± 11.85°, Welcher basal angle 130.83° ± 6.29°, craniocervical tilt 126.98° ± 12.24° and Powers ratio as 0.72 ± 0.06.

CONCLUSION

In this study, the morphometric values were evaluated according to age and gender in individuals who did not have any radiologic anomalies. The normal reference ranges may be useful for researchers who are researching pathology in this region. It is recommended to conduct further studies with different populations to determine the normal reference range.

X-ray and Computed Tomography Scan-Based Morphometric Analysis of Skull Baselines in Indian Population

Introduction:

The study aims at providing an overview of morphometric measurements of the skull baselines in normal Indian population and compares these dimensions with those of other races and ethnicities. This study will help in defining “normal” baseline values for Indian population. It will also compare dimensions as measured on X-ray and computed tomography (CT) scan to assess the reliability of X-ray as a diagnostic modality for the assessment of the skull baselines in Indian population.

Materials and Methods:

Retrospective study with a sample size of 116 patients and duration of 30 months.

Results:

The mean value for distance between dens tip and Chamberlain line on CT was 0.498 mm and on X-ray was 0.528 mm and for the distance between dens tip and McGregor line on CT was 0.213 mm and on X-ray was 0.228 mm. The mean distance between the dens tip and McRae line was 4.67 1.69 mm on CT scan and 4.7 1.76 mm on X-ray.

Conclusion:

There was not a single patient in whom the dens tip crossed the McRae line. Any protrusion of the dens tip beyond the foramen magnum is abnormal. Hence, the McRae line is easiest to understand and remember. Furthermore, the Chamberlain and McGregor lines rely on identifying the hard palate, which may not be included in routine X-ray, CT, and magnetic resonance imaging studies depend on the field of view. Hence, we recommend the use of McRae line for screening purposes while evaluating pathologies of the craniovertebral junction. X-ray is a reliable diagnostic technique for assessing morphometry of the skull baselines in an emergency or rural setting if facility for CT scan is not available.

Halo-gravity traction for the treatment of pediatric cervical spine disorders

OBJECTIVE

Halo-gravity traction (HGT) is an effective and safe method for gradual correction of severe cervical deformities in adults. However, the literature is limited on the use of HGT for cervical spine deformities that develop in children. The objective of the present study was to evaluate the safety and efficacy of HGT for pediatric cervical spine deformities.

METHODS

Twenty-eight patients (18 females) whose mean age was 11.3 ± 5.58 years (range 2-24.9 years) underwent HGT. Common indications included kyphosis (n = 12), rotatory subluxation (n = 7), and basilar invagination (n = 6). Three children (11%) received traction to treat severe occipitocervical instability. For these 3 patients, traction combined with a halo vest, with bars attached rigidly to the vest, but with the ability to slide through the connections to the halo crown, was used to guide the corrective forces and moments in a specific and controlled manner. Patients ambulated with a wheelchair or halo walker under constant traction. Imaging was done before and during traction to evaluate traction efficacy. The modified Clavien-Dindo-Sink classification was used to categorize complications.

RESULTS

The mean duration of HGT was 25 days (IQR 13-29 days), and the mean traction was 29% ± 13.0% of body weight (IQR 19%-40% of body weight). The mean kyphosis improved from 91° ± 20.7° (range 64°-122°) to 56° ± 17.6° (range 32°-96°) during traction and corresponded to a mean percentage kyphosis correction of 38% ± 13.8% (range 21%-57%). Twenty-five patients (89%) underwent surgical stabilization, and 3 patients (11%) had rotatory subluxation that was adequately reduced by traction and were treated with a halo vest as their definitive treatment. The mean hospital stay was 35 days (IQR 17-43 days).Nine complications (32%) occurred: 8 grade I complications (28%), including 4 cases of superficial pin-site infection (14%) and 4 cases of transient paresthesia (14%). One grade II complication (4%) was seen in a child with Down syndrome and a preexisting neurological deficit; this patient developed flaccid paralysis that rapidly resolved with weight removal. Six cases (21%) of temporary neck discomfort occurred as a sequela of a preexisting condition and resolved without treatment within 24-48 hours.

CONCLUSIONS

HGT in children is safe and effective for the gradual correction of cervical kyphosis, atlantoaxial subluxation, basilar invagination, and os odontoideum. Cervical traction is an additional tool for the pediatric spine surgeon if uncertainties exist that the spinal alignment required for internal fixation and deformity correction can be safely achieved surgically. Common complications included grade I complications such as superficial pin-site infections and transient paresthesias. Halo vest gravity traction may be warranted in patients with baseline neurological deficits and severe occipitocervical instability to reduce the chance of catastrophic movement.

Delayed Instrumentation Following Removal of Cranio-Vertebral Junction Chordomas: A Technical Note

Objective  To investigate on the feasibility and safety of a new approach which consists of delaying instrumentation after destabilizing craniovertebral junction (CVJ) chordoma surgery, allowing proton beam radiotherapy to be performed in a metal-free tumoral cavity. Design  This is a retrospective series of a prospectively maintained database. Participants  Five consecutive patients operated on for a CVJ chordomas for which instrumentation after tumor resection was deferred to after radiotherapy treatment. Main Outcome Measures  The main outcome consisted of measurements of the following parameters: C0-C2 angle, atlanto-dens interval (ADI), condylar gap, and the position of the dens relative to McGregor's line and coronal inclination, performed at 3 different times for all patients: before tumor surgery (baseline), before instrumentation surgery, and after instrumentation surgery. Results  For all patients, CVJ parameters deteriorated during the delay period, but stayed within normal limits for most. Because of radiological instability, one patient necessitated instrumentation before receiving radiotherapy. All parameters except condylar gap were partially corrected after instrumentation. No new neurological symptom or evolving neck pain occurred during the delay period. Conclusion  Delayed instrumentation of CVJ chordomas can be a safe alternative that might lead to improved subsequent radiotherapeutical treatment. Patient's selection and close clinical and radiological follow-up are mandatory for the success of this approach.

Agenesis of the posterior arch of the atlas and complex alterations of the craniovertebral junction: A case report

The craniovertebral junction is a unique part of the somite-derived axial skeleton. The absence or hypoplasia of the posterior arch of C1 is frequently associated with compensatory hypertrophy of the anterior arch of C1 and of the spinous process of C2. Here, we report a patient with agenesis of the posterior arch of C1 without neurologic deficits. Our patient presented with complex alterations of the craniovertebral junction that involved interactions between the condyles, clivus, atlas, and epistropheus. To our knowledge, dislocation of the odontoid process above the Chamberlain line, including cranial migration of the anterior arch of C1, has not been reported in the literature.

Upper Cervical Subluxation and Cervicomedullary Junction Compression in Patients with Rheumatoid Arthritis

Objective

Rheumatoid arthritis (RA) is known to involve the cervical spine up to 86%. It often causes cervical instability like atlantoaxial subluxation (AAS), subaxial subluxation, and vertical subluxation (VS). In order to find the relation between RA and cord compression, we will evaluate the characteristics and risk factors of basilar invagination (BI) and cervicomedullary junction (CMJ) compression.

Methods

From January 2007 to May 2015, 12667 patients administrated to Hanyang University Medical Center. Four thousand three hundred eighty-six patients took cervical X-ray and 250 patients took cervical computed tomography or magnetic resonance imaging. Radiologic parameters, medication records were obtained from 242 patients. Multivariate logistic regression analysis was performed with correlation of CMJ compression, basin-dental interval (BDI), basin-posterior axial line interval (BAI), pannus formation, BI, and AAS.

Results

In the point of CMJ compression, atlantodental interval (ADI), posterior-atlantodental interval, BAI, AAS, and BI are relatively highly correlated. Patients with BI have 82 times strong possibility of radiologic confirmed CMJ compression, while AAS has 6-fold and pannus formation has the 3-fold possibility. Compared to the low incidence of BI, AAS and pannus formation have more proportion in CMJ compression. Furthermore, wrist joint erosion was correlated with VS and AAS.

Conclusion

BI has a very strong possibility of CMJ compression, while AAS and pannus formation have a high proportion in CMJ compression. Hence bilateral wrist joint erosion can be used as an indicator for the timing of screening test for cervical involvement. We suggest the early recommendation of cervical spine examination for the diagnosis of cervical involvement in order to prevent morbidity and mortality.

Radiological Evaluation of Craniocervical Region in Patients with Basilar Invagination

STUDY DESIGN

A retrospective analysis of collected data.

OBJECTIVE

Our study aims to present the morphology of cranial-cervical spinal canal in basilar invagination (BI) patients.

SUMMARY OF BACKGROUND DATA

BI is characterized by protrusion of the odontoid process into the foramen magnum (C0), leading to compression of the cervicomedullary junction. However, no study has ever clarified the anatomical diameters of spinal canal in patients with BI.

METHODS

The study retrospectively examined computed tomography (CT)-based anatomical characteristics in a cohort of 84 patients with and without BI. We measured the anteroposterior diameter (APD) and transversal diameter (TVD) of spinal canal from C0 to C4, together with the area of vertebral canal (Area). Independent samples t test was used for statistical analysis.

RESULTS

The APD in the BI group was shorter than the control group from C0 to C2 (C0: 27.98 vs. 35.11 mm, P < 0.001; C1: 11.87 vs. 16.91 mm, P < 0.001; C2: 12.91 vs. 14.84 mm, P < 0.001), but it became longer from C3 to C4. The TVD of the BI group was significantly wider from C0 to C3 (C0: 30.59 vs. 28.54 mm, P < 0.001; C1: 31.31 vs. 25.98 mm, P < 0.001; C2: 21.56 vs. 20.40 mm, P = 0.01; C3: 22.45 vs. 21.23 mm, P = 0.013), and it had no significance at C4. The Area showed no difference between the two groups from C1 to C2, but it turned larger at C3 and C4 in BI patients.

CONCLUSION

BI patients may have shorter APD from C0 to C2, which could be the leading cause of neurological compression, necessitating decompression on sagittal plane. Below the pathological levels, BI patients have larger spinal canal than general population.

LEVEL OF EVIDENCE

3.

Chiari I Malformation and Basilar Invagination in Fibrous Dysplasia: Prevalence, Mechanisms, and Clinical Implications

Fibrous dysplasia (FD) is a mosaic disorder of benign fibro-osseous lesions, which may be associated with extraskeletal features as part of McCune-Albright syndrome (MAS). Cranial base abnormalities, including Chiari I malformation (CM1), in which the cerebellum extends below the foramen magnum, and secondary basilar invagination (BI), in which the odontoid prolapses into the posterior cranial fossa, are potentially serious complications of metabolic bone disorders. The purpose of this study was to determine the prevalence, natural history, and risk factors for CM1 and BI in patients with FD/MAS, and to determine mechanisms of cranial base deformities. Clinical and radiographic data from subjects in an FD/MAS natural history study were evaluated and compared to normal controls. In 158 patients with craniofacial FD, 10 (6.3%) cases of CM1 and 12 (7.6%) cases of BI were diagnosed. No cranial base abnormalities were identified in 10 control subjects. Craniomorphometric and volumetric analyses identified cranial constriction and cranial settling as the primary mechanisms of cranial base abnormalities, whereas intracranial hypertension was a contributing factor in a minority of subjects. Longitudinal analyses found progression of odontoid position with age, but no progression of tonsillar position. No endocrinopathies were associated with CM1. MAS endocrinopathies associated with BI included hyperthyroidism (odds ratio [OR] 12.0; 95% confidence interval [CI], 2.9 to 55.6; p < 0.01), precocious puberty (OR 5.6; 95% CI, 1.2 to 26.0; p < 0.05), and hypophosphatemia (OR 7.7; 95% CI, 1.9 to 27.0; p < 0.01). Scoliosis was associated with both CM1 (OR 4.8; 95% CI, 1.1 to 22.8; p < 0.05) and BI (OR = infinity; 95% CI, 4.7 to infinity; p < 0.01). This study successfully characterized cranial base abnormalities in FD/MAS and the pathophysiological connection between them. These findings support routine screening for cranial base abnormalities in patients with craniofacial FD, as well as aggressive management of contributory risk factors. © 2018 American Society for Bone and Mineral Research.

Auditory Brainstem Implant Array Position Varies Widely Among Adult and Pediatric Patients and Is Associated With Perception

OBJECTIVES

The auditory brainstem implant (ABI) provides sound awareness to patients who are ineligible for cochlear implantation. Auditory performance varies widely among similar ABI cohorts. We hypothesize that differences in electrode array position contribute to this variance. Herein, we classify ABI array position based on postoperative imaging and investigate the relationship between position and perception.

DESIGN

Retrospective review of pediatric and adult ABI users with postoperative computed tomography. To standardize views across subjects, true axial reformatted series of scans were created using the McRae line. Using multiplanar reconstructions, basion and electrode array tip coordinates and array angles from vertical were measured. From a lateral view, array angles (V) were classified into types I to IV, and from posterior view, array angles (T) were classified into types A to D. Array position was further categorized by measuring distance vertical from basion (D1) and lateral from midline (D2). Differences between array classifications were compared with audiometric thresholds, number of active electrodes, and pitch ranking.

RESULTS

Pediatric (n = 4, 2 with revisions) and adult (n = 7) ABI subjects were included in this study. Subjects had a wide variety of ABI array angles, but most were aimed superiorly and posteriorly (type II, n = 7) from lateral view and upright or medially tilted from posterior view (type A, n = 6). Mean pediatric distances were 8 to 42% smaller than adults for D1 and D2. In subjects with perceptual data, electrical thresholds and the number of active electrodes differed among classification types.

CONCLUSIONS

In this first study to classify ABI electrode array orientation, array position varied widely. This variability may explain differences in auditory performance.

Revisiting the differences between irreducible and reducible atlantoaxial dislocation in the era of direct posterior approach and C1–2 joint manipulation

OBJECTIVE

The current management of atlantoaxial dislocation (AAD) focuses on the C1–2 joints, commonly approached through a posterior route. The distinction between reducible AAD (RAAD) and irreducible AAD (IrAAD) seems to be less important in modern times. The roles of preoperative traction and dynamic radiographs are questionable. This study evaluated whether differentiating between the 2 groups is important in today's era.

METHODS

Ninety-six consecutive patients with congenital AAD (33 RAAD and 63 IrAAD), who underwent surgery through a posterior approach alone, were studied. The preoperative and follow-up clinical statuses for both groups were studied and compared using Japanese Orthopaedic Association (JOA) scores. The radiological findings of the 2 groups were compared, and the intraoperative challenges described.

RESULTS

A poor preoperative JOA score (clinical status) was seen in one-fifth of patients with IrAAD, although the mean JOA score was nearly similar in the RAAD and IrAAD groups. There was significant improvement in follow-up JOA score in both groups. However, segmentation defects (such as an assimilated arch of the atlas and C2–3 fusion) and anomalous vertebral arteries were found significantly more often in cases of IrAAD compared with those of RAAD. Os odontoideum was commonly seen in the RAAD group. The C1–2 joints were acute in IrAAD compared with RAAD. Preoperative traction in IrAAD resulted in vertical distraction and improvement in clinical and respiratory status. Surgery for IrAAD required much more drilling and manipulation of the C1–2 joints while safeguarding the anomalous vertebral artery.

CONCLUSIONS

Bony and vascular anomalies were much more common in patients with IrAAD, which made surgery more challenging than it was in RAAD despite similar approaches. An irreducible dislocation seen on preoperative radiographs made surgeons aware of difficulties that were likely to be encountered and helped them to better plan the surgery. Distraction achieved through preoperative traction reaffirmed the feasibility of intraoperative reduction. This made the differentiation between the 2 groups and the use of preoperative traction equally important.

Treatment of Basilar Invagination With Klippel-Feil Syndrome: Atlantoaxial Joint Distraction and Fixation With Transoral Atlantoaxial Reduction Plate

BACKGROUND

Klippel-Feil syndrome (KFS) is characterized by congenital vertebral fusion of the cervical spine and a wide spectrum of associated anomalies. In patients with KFS with basilar invagination (BI), compression of the brainstem and upper cervical cord results in neurological deficits, and decompression and occipitocervical reconstruction are required. The highly varied anatomy of KFS makes a posterior occipitocervical fixation strategy challenging. For these patients, the transoral atlantoaxial reduction plate (TARP) operation is an optimal option to perform a direct anterior fixation to achieve stabilization.

OBJECTIVE

To evaluate the effectiveness of TARP internal fixation for the treatment of BI with KFS.

METHODS

Ten consecutive patients with BI and KFS who underwent TARP reduction and fixation from 2010 to 2012 were reviewed. Clinical assessment and image measurements were performed preoperatively and at the most recent follow-up. Nine patients (9/10) were followed for an average of 31.44 months.

RESULTS

Symptoms were alleviated in 9 of 9 patients (100.00%). The odontoid process was ideally corrected with the TARP system. The mean clivus canal angle improved from 124° preoperatively to 152° postoperatively. The average preoperative and postoperative Japanese Orthopedic Association scores were 10.56 (n = 9) and 14.67 (n = 9), respectively, indicating 63.82% improvement. There was bony bridge catenation on the computed tomography scans and no evidence of hardware failure at 6 months.

CONCLUSION

The TARP operation is effective and safe for treating patients with BI with KFS. The midterm clinical results were satisfactory.

Spontaneous regression of a chiari malformation type 1 in a 58-year-old female

Studies have established a complex age-related variation of the position of the cerebellar tonsils relative to the foramen magnum (FM). Chiari malformation type 1 (CM1) is generally defined by a protrusion >5 mm from the FM and may be an asymptomatic incidental finding. Symptoms include headache, nausea and neurological disturbances, including trigeminal neuralgia. Moreover, tonsils are often peg shaped and associated with syringohydromyelia. Symptomatic CM1 may be managed with decompression of the posterior cranial fossa, but spontaneous regression in adults has been reported occasionally. Theories include restoration of normal cerebrospinal fluid dynamics around the FM after rupture of subarachnoid adhesions or the syrinx itself during transient episodes of raised intracranial pressure. Supratentorial neurosurgery has also been implicated. We present a 58-year-old female diagnosed with CM1 and no associated syringohydromyelia following MRI investigation of trigeminal neuralgia. Managed medically, she re-presented 6 years later with new neurological symptoms. A subsequent MR study of the posterior cranial fossa showed resolution of the CM1, with only residual tonsillar ectopia. At no point was intracranial intervention performed, nor were there any events that might favour CM1 regression. This case demonstrates spontaneous resolution of CM1 without surgical intervention.

Congenital Agenesis of the Posterior Elements of the Axis (C2), Occipitalization of the Atlas (C1), and Basilar Invagination in an Adult Woman: A Case Report

CASE

A 55-year-old woman presented with chronic neck pain. Physical and neurological examination results were normal. Radiographs revealed absence of the posterior elements of C2 with hypertrophy of the spinous process of C3. A computed tomography scan showed occipitalization of the atlas with basilar invagination. Magnetic resonance imaging did not reveal any soft-tissue abnormalities. The patient was treated with a short course of a nonsteroidal anti-inflammatory drug and physiotherapy.

CONCLUSION

Agenesis of the posterior elements of C2 should be considered in patients with hypertrophy of the spinous process of C3. Patients may have a varied presentation ranging from neck pain to myelopathy. Dynamic (flexion and extension) lateral cervical spine radiographs should be obtained, as cases reported in the literature involved instability of the cervical spine.

Imaging Findings and Evaluation of Metabolic Bone Disease

Bone is a dynamic organ of the endoskeleton, playing an important role in structural integrity, mineral reservoirs, blood production, coagulation, and immunity. Metabolic bone disease encompasses a broad spectrum of inherited and acquired disorders that disrupt the normal homeostasis of bone formation and resorption. For patients affected by these processes, radiologic imaging plays a central role in diagnosis, monitoring treatment, and risk stratification. Radiologists should be familiar with the diseases, intimately aware of the imaging findings, and possessive of multimodality expertise to wisely guide the best practice of medicine. The purpose of this paper is to review the imaging features and characteristics of the most common types of metabolic bone disease with highlights of clinically relevant information so that readers can better generate appropriate differential diagnoses and recommendations. For this review, a thorough literature search for the most up-to-date information was performed on several key types of metabolic bone disease: osteoporosis, osteomalacia, rickets, scurvy, renal osteodystrophy, hyperparathyroidism, Paget’s disease, osteogenesis imperfecta, acromegaly, and osteopetrosis. Although they all affect the bone, these diseases have both shared characteristic features that can be discerned through imaging.

Age, gender and normalization covariates for spinal cord gray matter and total cross-sectional areas at cervical and thoracic levels: A 2D phase sensitive inversion recovery imaging study

The source of inter-subject variability and the influence of age and gender on morphometric characteristics of the spinal cord, such as the total cross-sectional area (TCA), the gray matter (GM) and white matter (WM) areas, currently remain under investigation. Understanding the effect of covariates such as age, gender, brain volumes, and skull- and vertebra-derived metrics on cervical and thoracic spinal cord TCA and GM areas in healthy subjects would be fundamental for exploring compartment specific changes in neurological diseases affecting the spinal cord. Using Magnetic Resonance Imaging at 3T we investigated 32 healthy subjects using a 2D phase sensitive inversion recovery sequence and we measured TCA, GM and WM areas at 4 cervical and thoracic levels of the spinal cord. We assessed age and gender relationships of cord measures and explored associations between cord measures and a) brain volumes and b) skull- and vertebra-derived metrics. Age and gender had a significant effect on TCA, WM and GM areas (with women and elderly having smaller values than men and younger people respectively), but not on the GM area/TCA ratio. The total intracranial volume and C3 vertebra dimensions showed the highest correlations with cord measures. When used in multi-regression models, they reduced cord areas group variability by approximately a third. Age and gender influences on cord measures and normalization strategies here presented might be of use in the study of compartment specific changes in various neurological diseases affecting the spinal cord.

Spontaneous resolution of Chiari type 1 malformation. A case report and literature review

We describe a 62-year-old woman who presented with a history of ataxia, dizziness and urinary urgency. Neurological examination disclosed a positive Romberg sign, ataxia and postural instability. A magnetic resonance imaging (MRI) scan showed Chiari type 1 malformation (CM1). Forty-eight months later, the patient was clinically improved and underwent a second MRI examination, which showed complete resolution of the Chiari 1 malformation. Spontaneous resolution of CM1 is exceptionally rare and has to be considered in the radiological and clinical management.

Craniospinal abnormalities and neurologic complications of osteogenesis imperfecta: imaging overview

Osteogenesis imperfecta is a rare genetic disorder that leads to progressive skeletal deformities due to deficits in type I collagen, the main pathophysiologic effect of the disease. In addition, it may lead to a wide range of associated neurologic abnormalities: The central nervous system is usually involved because of softening of bone at the base of the skull, with resultant upward migration of the upper cervical spine and odontoid process into the skull base. Upward migration of the spine may cause compression of the brainstem, mechanical impingement of the spinal canal with restriction of cerebrospinal fluid circulation, and impingement of the cranial nerves. Osteogenesis imperfecta also may directly involve neurovascular structures, leading to cavernous fistulas of the carotid artery, dissection of the cervical arteries, and cerebral aneurysms. The brain parenchyma is frequently affected by the disease, with manifestations including cerebral atrophy, communicating hydrocephalus, and cerebellar hypoplasia. The imaging features of the disorder vary as widely as its clinical manifestations, depending on the severity of disease. Severe forms accompanied by debilitating skeletal fractures and progressive neurologic impairments may lead to perinatal death, whereas milder asymptomatic forms might cause only a modest reduction in life span. The most important advance in medical therapy for osteogenesis imperfecta has been the introduction of bisphosphonate therapy to slow the resorption of bone in patients with moderate to severe forms of the disease (ie, type III or IV). In some patients, neurosurgery may be necessary to correct the effects of severe basilar invagination by the odontoid process.

Distraction, Compression, and Extension Reduction of Basilar Invagination and Atlantoaxial Dislocation

BACKGROUND:

The management of basilar invagination (BI) and atlantoaxial dislocation (AAD) is a challenge.

OBJECTIVE:

To describe a new innovative method to reduce BI and AAD through a single-stage posterior approach.

METHODS:

Thirty-five patients had irreducible BI and AAD (May 2010 to April 2012). In all patients, reduction of AAD and BI was achieved by using an innovative method of distraction and spacer placement, followed by compression and extension. A C1 lateral mass/C2 translaminar screw was performed in cases where the C1 arch was not assimilated, and occipito-C2 translaminar screw fixation was performed in cases where the C1 arch was assimilated.

RESULTS:

Thirty-two of 35 (94%) patients improved clinically and 2 patients had stable symptoms (mean Nurick postoperative score = 1.4; preoperative score = 3.7). AAD reduced completely in 33/35 patients and &gt;50% in 2. BI improved significantly in all patients. Solid bone fusion was demonstrated in 24 patients with at least 1-year follow-up (range, 12-39 months; mean, 19.75 + 7.09 months). The duration of surgery was 80 to 190 minutes, and blood loss was 90 to 500 mL (mean, 170 ± 35 mL). There was 1 death because of cardiac etiology and 1 morbidity (wound infection).

CONCLUSION:

Distractive compressive extension and reduction of BI and AAD seems to be an effective and safe method of treatment. It is different from the earlier described techniques, because it is the first procedure that uses a spacer not, only for distraction, but also as a pivot to perform extension to reduce the AAD.

The importance of platybasia and the palatine line in patient selection for endonasal surgery of the craniocervical junction: a radiographic study of 12 patients

OBJECTIVE

Ventral decompressive surgery of the craniocervical junction is performed to manage a variety of conditions, including basilar invagination, which can be associated with platybasia. We have noted that the anatomic changes of platybasia could affect the height of the odontoid over a line drawn along the nasal cavity floor, the palatine line (PL). This anatomic change may influence the use of nasal endoscopic surgery for patients with platybasia who also have basilar invagination. We investigated whether the height of the craniocervical junction is elevated over the PL in patients with and without platybasia.

METHODS

We conducted a retrospective review of consecutive craniovertebral junction surgical cases during a 14-month period. During that time we treated 12 patients, including 4 with platybasia and 8 without. The average age was 50 years (range, 18-64 years). Preoperative and postoperative radiographic images were evaluated and charts reviewed.

RESULTS

The mean height of the odontoid over the PL without platybasia was 3.5 mm (range, 0-19.0 mm). In those with platybasia, it was 15.5 mm (range, 7-26.0 mm; P=.021). There was a statistically significant increase in the height of the clival tip and C1 ring in patient with platybasia as well.

CONCLUSIONS

Platybasia is associated with an increase in the odontoid and craniocervical junction over the PL. This increase in height has implications for endoscopic approach selection in patients with platybasia. Platybasia patients with basilar invagination may be better suited to a transnasal approach.

Chiari 1.5 malformation : an advanced form of Chiari I malformation

The Chiari 1.5 malformation is defined as a tonsillar herniation within a Chiari I malformation with additional caudal descent of the brainstem through the foramen magnum. We describe a patient with Chiari I malformation who evolved to Chiari 1.5 malformation during longitudinal follow-up. A 15-year-old girl presented with neck pain during exercise for two years. She had been diagnosed with Chiari I malformation with mild hydrocephalus after minor cervical trauma at the age of six years. At that time, she was asymptomatic. After she complained of aggravated neck pain, neuroimaging (nine years after first imaging) revealed caudal descent of the brainstem and syringomyelia in addition to progression of tonsillar herniation. Posterior fossa decompressive surgery resulted in complete resolution of neck pain. Based on neuroimaging and operative findings, she was diagnosed as Chiari 1.5 malformation. Neuroimaging performed seven months after surgery showed an increased anterior-posterior diameter of the medulla oblongata and markedly decreased syringomyelia. This case demonstrates progressive developmental process of the Chiari 1.5 malformation as an advanced form of the Chiari I malformation.