Os Odontoideum in Children.

Os odontoideum is a rare entity of the second cervical vertebra, characterized by a circumferentially corticated ossicle separated from the body of C2. The ossicle is a distinct entity from an odontoid fracture or a persistent ossiculum terminale. The diagnosis may be made incidentally on imaging obtained for the workup of neck pain or neurologic signs and symptoms. Diagnosis usually can be made with plain radiographs. MRI and CT can assess spinal cord integrity and C1-C2 instability. The etiology of os odontoideum is a topic of debate, with investigative studies supporting both congenital and traumatic origins. A wide clinical range of symptoms exists. Symptoms may present as nondescript pain or include occipital-cervical pain, myelopathy, or vertebrobasilar ischemia. Asymptomatic cases without evidence of radiologic instability are typically managed with periodic observation and serial imaging. The presence of atlantoaxial instability or neurological dysfunction necessitates surgical intervention with instrumentation and fusion for stability.

The C0-C2 axial rotation test: normal values, intra- and inter-rater reliability and correlation with the flexion rotation test in normal subjects.

OBJECTIVES: Impairment in upper cervical spine mobility is associated with cervicogenic headache severity and disability. Measures of such mobility include the flexion-rotation test (FRT), which requires full cervical flexion and may be influenced by lower cervical spine dysfunction. The C0-C2 axial rotation test also evaluates upper cervical mobility but normal values and reliability have not been reported. Our objective is to determine normal values, and intra-rater and inter-rater reliability of the C0-C2 axial rotation test. METHODS: Two therapists independently evaluated the FRT and C0-C2 axial rotation test with an iPhone compass application on 32 asymptomatic subjects with mean age 40.53 (SD 11.64) years on two occasions. Measurement procedures were standardized; and order of testing randomized. RESULTS: For the FRT and C0-C2 axial rotation test reliability was high (ICC > 0.88). For rater one, Mean range to the left during the FRT and C0-C2 axial rotation test was 45.0° (6.04) and 14.43° (2.94), respectively, while range to the right was 44.6° (6.57) and 15.44° (2.68). For the FRT and C0-C2 axial rotation test the standard error of measurement was at most 2°, while the minimum detectable change was at most 4°. A strong positive correlation exists between the FRT and C0-C2 axial rotation test (r = 0.84, P < 0.01). DISCUSSION: The range recorded during the C0-C2 axial rotation test and FRT have high levels of reliability when evaluated using an iPhone. The strong correlation between the FRT and C0-C2 axial rotation test indicate that both may be measuring similar constructs, but each test needs to be referenced to normal values.

Low bone mineral density predicts the formation of new syndesmophytes in patients with axial spondyloarthritis.

BACKGROUND: This study aimed to investigate whether the presence of low bone mineral density (BMD) in patients with axial spondyloarthritis (axSpA) predicts formation of new syndesmophytes over 2 years. METHODS: One hundred and nineteen patients fulfilling the imaging arm of the Assessment of SpondyloArthritis International Society axSpA criteria were enrolled. All patients were under 50 years of age. The modified Stoke Ankylosing Spondylitis Spinal Score (mSASSS) was assessed by two trained readers blinded to the patients' data. BMD (lumbar spine, femoral neck or total hip) at baseline was assessed using dual-energy absorptiometry. Low BMD was defined as Z score ≤ - 2.0. Spinal radiographic progression was defined as worsening of the mSASSS by ≥ 2 points over 2 years. Logistic regression analyses were performed to identify predictors associated with development of new syndesmophytes and spinal radiographic progression. RESULTS: At baseline, 19 (16%) patients had low BMD. New syndesmophytes had developed in 22 (21%) patients at 2-year follow-up. New syndesmophyte formation after 2 years occurred more in patients with low BMD than in those with normal BMD (p = 0.047). In the multivariable analysis, current smoking, existing syndesmophytes and low BMD at baseline were associated with spinal radiographic progression (OR (95% CI) 3.0 (1.1, 7.7), 4.6 (1.8, 11.8) and 3.6 (1.2, 11.2), respectively). The presence of syndesmophytes at baseline and low BMD were predictors of new syndesmophytes over the following 2 years (OR (95% CI) 5.5 (2.0, 15.2) and 3.6 (1.1, 11.8), respectively). CONCLUSIONS: Low BMD and existing syndesmophytes at baseline were independently associated with the development of new syndesmophytes in young axSpA patients.

Trabecular bone score as an assessment tool to identify the risk of osteoporosis in axial spondyloarthritis: a case-control study.

OBJECTIVES: To compare the trabecular bone score (TBS) between patients with axial spondyloarthritis (axSpA) and matched normal controls and identify risk factors associated with a low TBS. METHODS: TBS and BMD were assessed in the two groups (axSpA and control) using DXA. Osteoporosis risk factors and inflammatory markers were also assessed. Disease activity and radiographic progression in the sacroiliac joint and spine were evaluated in the axSpA group. Multivariate linear regression analysis was performed to identify risk factors associated with TBS. RESULTS: In the axSpA group, 248 subjects were enrolled; an equal number of age- and sex-matched subjects comprised the control group. The mean TBS was 1.43 (0.08) and 1.38 (0.12) in the control and axSpA groups, respectively (P < 0.001); BMD at the lumbar spine did not differ between the two groups. The TBS was negatively correlated with ESR and CRP levels in the axSpA group only (P < 0.001 and P = 0.007, respectively). Syndesmophytes in the axSpA group was associated with lower TBS (P < 0.001) but higher lumbar BMD (P = 0.021) vs controls. In the multivariate analyses, ESR, CRP and spinal radiographic progression were significantly associated with TBS. CONCLUSION: TBS assessments revealed poor bone quality in patients with axSpA compared with the matched controls. In axSpA, systemic inflammatory markers were negatively correlated with TBS and spinal radiographic progression and inflammatory markers were independently correlated with low TBS. TBS may, therefore, be a useful clinical tool to identify the risk of osteoporosis in patients with axSpA.

'Congenital anomalies of craniovertebral junction presenting after 50 years of age': An oxymoron or An unusual variation?

OBJECTIVES: Manifestation of congenital anomalies of cranio-vertebral junction (CVJ) in the later half of life is unusual and intriguing. Coexisting cervical spondylotic changes with multilevel compression, poorer bone quality as well as less smooth post-surgical recuperation make management of elderly Congenital Atlantoaxial Dislocation/ Basilar Invagination (CAAD/BI) challenging. The clinico-radiological presentation, pathogenesis and outcome are analysed here. PATIENTS AND METHODS: Clinico-radiological data of 20 patients of CAAD/BI (with markers of congenital anomalies) presenting after 50 years of age, the challenges faced and outcomes after C1-C2 fusion have been analysed. RESULTS: Three distinct groups were identified. Seven patients with Os-odontoideum had reducible AAD (Type I). Seven patients had assimilated C1, C2-3 fusion and deformed C1-2 joints with irreducible AAD/BI (Type II). In type III, 4 patients had similar segmentation defects but with compression at both cervico-medullary junction and subaxial spine, although clinical localisation pointed to the CVJ. Spastic quadriparesis was the commonest presentation. All underwent C1-2 fusion alone. There was significant improvement in 18, including those with compression at additional level. Bony fusion was documented in all patients followed up beyond one year. CONCLUSION: Congenital CVJ anomalies may present in later half of life, though attempts at reasoning remain speculative. These patients improve after multiplanar realignment and C1-2 fusion. Careful clinico-radiological evaluation is required in those with additional subaxial compression. Bone quality in elderly is not a deterrent for instrumentation. Fusion eventually occurs in most.

Magnetic Resonance Imaging Analysis of Deep Cervical Flexors in Patients with Ossification of the Posterior Longitudinal Ligament and Clinical Implication.

OBJECTIVE: The purpose of this study was to analyze the cross-sectional area (CSA) of deep cervical flexors as measured by magnetic resonance imaging in ossification of the posterior longitudinal ligament (OPLL) patients with neck pain and, by implication, how this may relate to recruitment of the deep cervical flexors and sternocleidomastoid. DESIGN: A retrospective case-control study was conducted. All 72 subjects were imaged using plain radiography, computed tomography, and magnetic resonance imaging. RESULTS: There was a more limited cervical range of motion in the OPLL group than that in the control group. Cervical lordosis, T1 slope, and thoracic inlet angle values were significantly lower in the OPLL group than in the control group. Bilateral CSAs of the longus colli muscle and longus capitis muscle of the OPLL group were smaller than those of the control group. In addition, bilateral CSAs of the sternocleidomastoid of the OPLL subjects were greater than those of healthy subjects. CONCLUSIONS: The authors found that the OPLL patients with chronic neck pain had lesser lordotic cervical alignment, smaller deep cervical flexor CSAs, and larger sternocleidomastoid CSAs than the control group did. The authors' theory is that the sternocleidomastoids in these OPLL patients have compensatorily hypertrophied in response to presumably atrophied deep cervical flexors.

Intended and non-intended kinematic effects of atlanto-axial rotational high-velocity, low-amplitude techniques.

INTRODUCTION: The study of neck kinematics during high-velocity, low-amplitude manipulations of the atlanto-axial segment is essential to understanding cervical motion mechanisms and their impact and possible risk for soft-tissue injuries during treatment of spine disorders. METHODS: Twenty fresh-frozen specimens were tested during manual application of an axial rotation technique. FINDINGS: The kinematics indicate the thrust induced motion components of approximately 1° at the treated segment around all three axes of the local embedded reference frame. Moreover, an equal amount of axial rotation motion took place at the adjacent atlanto-occipital joint. INTERPRETATION: Overall atlanto-axial motion remained below the level of slow regional mobilization of the cervical spine. These findings can be correlated to literature data concerning the limited increase in vertebral artery strain during high-velocity, low-amplitude manipulation.

Ankylosing spondylitis without axial progression: analysis of associated factors.

OBJECTIVE: To evaluate clinical factors associated with the absence of radiographic progression in patients with spondylitis. METHODS: The cross-sectional study included 672 patients. All patients presented a disease evolution of more than 15 years. Patients were classified as with radiographic spinal involvement versus without radiographic spinal involvement. We included clinical variables potentially related to null radiological progression. RESULTS: Seventy-five patients had no radiographic involvement. These patients were predominantly female, had a lower erythrocyte sedimentation rate (ESR), and a lower C-reactive protein level. Multivariate analysis showed an association with the female sex and low ESR. CONCLUSION: Clinical factors associated with this lack of progression were female sex and low ESR.

Axial head rotation increases facet joint capsular ligament strains in automotive rear impact.

Axial head rotation prior to low speed automotive rear impacts has been clinically identified to increase morbidity and symptom duration. The present study was conducted to determine the effect of axial head rotation on facet joint capsule strains during simulated rear impacts. The study was conducted using a validated intact head to first thoracic vertebra (T1) computational model. Parametric analysis was used to assess effects of increasing axial head rotation between 0 and 60° and increasing impact severity between 8 and 24 km/h on facet joint capsule strains. Rear impacts were simulated by horizontally accelerating the T1 vertebra. Characteristics of the acceleration pulse were based on the horizontal T1 acceleration pulse from a series of simulated rear impact experiments using full-body post mortem human subjects. Joint capsule strain magnitudes were greatest in ipsilateral facet joints for all simulations incorporating axial head rotation (i.e., head rotation to the left caused higher ligament strain at the left facet joint capsule). Strain magnitudes increased by 47-196% in simulations with 60° head rotation compared to forward facing simulations. These findings indicate that axial head rotation prior to rear impact increases the risk of facet joint injury.

Dynamic response of the idiopathic scoliotic spine to axial cyclic loads.

STUDY DESIGN: Numerical techniques were used to study the vibration response of idiopathic scoliosis patients with single thoracic curve. OBJECTIVE: To analyze the dynamic characteristics of the idiopathic scoliotic spine under the whole-body vibration condition. The influence of the upper body mass was also studied. SUMMARY OF BACKGROUND DATA: The relationship between the whole-body vibration and the spinal disorders has been investigated using finite element method. However, the dynamic response features of the scoliotic spine to the vibration were poorly understood. METHODS: The resonant frequencies of the scoliotic spine and the effects of the body weight were studied using a finite element model described previously. Modal and harmonic analysis was conducted. The amplitudes of 6 fundamental vertebral movements around the long, coronal and sagittal axis were quantified in the frequency range of 1 to 35 Hz. RESULTS: The vibration-induced rotation amplitudes of the apex of the thoracic deformity were higher than that of the lumbar segments. The apical vertebrae had the greatest rotation amplitudes at 2 and 8 Hz, and the largest lateral translation amplitudes at 16 Hz. Vibration could cause large lateral flexion amplitudes in the apex of the thoracic deformity. The apical vertebrae had the largest side flexion amplitudes at 6 Hz. Increasing upper body mass could not change resonant frequency of vibration-induced lateral translation and rotation around the long axis of the apical vertebrae. CONCLUSION: The scoliotic spine is more sensitive to vibration than the normal spine. For a patient with single thoracic curve, long-term whole-body vibration may do more harm to the thoracic deformity than to the lower lumbar segments. Axial cyclic loads applied to an already deformed spine may cause further rotational and scoliotic deformity. The patients with idiopathic scoliosis are more likely to suffer from vibration-induced spinal disorders than those by normal persons.

Transpedicular screw fixation for type II Hangman's fracture: a motion preserving procedure.

Opinions have varied regarding the optimal treatment of an unstable Hangman's fracture. C2 pedicle screw instrumentation is a biomechanically strong fixation which although done through a simple posterior approach, is a technically demanding procedure. This prospective, non-randomized multicentre study included 15 consecutive patients with displaced type II traumatic spondylolisthesis of the axis. There were nine males and six females with a mean age of 37 years at surgery. The cause of injury was a road traffic accident in 11 patients and a fall from height in 4 patients. All patients had a single stage reduction and direct transpedicular screw fixation through the C2 pedicles. During follow-up, clinical evaluation and plain X-rays were performed at each visit; at 6-month follow-up, additional dynamic lateral flexion/extension views and a CT scan were performed. The average follow-up period was 32 months (range 25-56 months). At final follow-up, all patients were asymptomatic and regained a good functional outcome with no limitation of range of motion; all the patients showed solid union with no implant failure. There were no neurological complications. At 6-month follow-up, CT evaluation showed fusion in all patients and an adequate position of 28 screws. Two pedicle screws (6.6%) showed minimal (defined as <2 mm) intrusion; one into the spinal canal and the other into the vertebral foreamen. Transpedicular screw fixation through the C2 pedicles is a safe and effective method in treating type II traumatic spondylolisthesis of the axis resulting in good clinical and radiological outcomes. Adequate reduction was achieved and motion segments were preserved with its use.

Biomechanical assessment of bilateral C1 laminar hook and C1-2 transarticular screws and bone graft for atlantoaxial instability.

UNLABELLED: STUDYDESIGN: In vitro biomechanical test was conducted to compare the stability of 5 different atlantoaxial posterior fusion techniques. OBJECTIVE: To evaluate the biomechanical stability of an atlas laminar hook combined with transarticular (TA) screws relative to 4 different conventional fusion techniques. SUMMARY OF BACKGROUND DATA: The atlantoaxial instability caused by fractures, rheumatoid arthritis, congenital deformity, or traumatic lesions of the transverse ligament often result in acute or chronic spinal cord compression, a possible threat to a patient's life. Posterior atlantoaxial fixations are used to reconstruct the stability of atlantoaxial articulation. Conventional posterior atlantoaxial fixations are associated with high rates of pseudoarthrosis and carry the potential risk of neurologic complication. TA screw fixation can provide an excellent biomechanical stability. As a modified 3-point fixation technique, the bilateral C1-2 TA screws have been combined with C1 laminar hook and bone grafts. This modified technique had carried good clinical outcomes. METHODS: Eight human specimens (C0-C4) were loaded nondestructively with pure moments and the range of motion at the level of C1-C2 was measured. Eight specimens were implanted with each of the following techniques, respectively: Gallie fixation, C1-2 TA screw fixation combined with Gallie fixation, C1-2 TA screw fixation, C1 laminar hook combined with C1-2 TA screw fixation plus bone grafts, and the C1 lateral mass screws in the atlas combined with C2 isthmic screws in axis. RESULTS: Although the C1-2 TA screws best restricted lateral bending and axial rotation, the modified 3-point fixation technique additionally restricted flexion-extension and provided the excellent stability. Differences in axial rotation and lateral bending (with + or - 1.5 Nm load) were observed when the 3-point fixation techniques (TA + Gallie and TA + hook) were compared with atlas lateral mass screws in the atlas combined with isthmic screws in axis. CONCLUSIONS: The modified C1 laminar hook combined with C1-2 TA screws and bone graft fixation provided the best biomechanical stability. The C1 lateral mass screws in the atlas combined with isthmic screws in axis fixation is a sound alternative when the C1-2 TA screw fixation is not feasible.

Traumatic spondylolisthesis of the axis: a biomechanical comparison of clinically relevant anterior and posterior fusion techniques.

OBJECT: Surgical management of unstable traumatic spondylolisthesis of the axis includes both posterior and anterior fusion methods. The authors performed a biomechanical study to evaluate the relative stability of anterior fixation at C2-3 and posterior fixation of C-1 through C-3 in hangman's fractures. METHODS: Fresh-frozen cadaveric spine specimens (occipital level to T-2) were subjected to stepwise destabilization of the C1-2 complex, replicating a Type II hangman's fracture. Intact specimens, fractured specimens, and fractured specimens with either anterior screw and plate or posterior screw and rod fixation were each tested for stability. Each spine was subjected to separate right and left rotation, bending, flexion, and extension testing. RESULTS: Anterior fixation restored stiffness in flexion and extension movements to values greater than those for intact specimens. For other movement parameters, the values approximated those for intact specimens. Posterior fixation increased the stiffness to above those values seen for anterior fixation specimens. CONCLUSIONS: In cadaveric spine specimens subjected to a Type II hangman's fracture, both anterior fixation at C2-3 and posterior fixation with C-1 lateral mass screws and C-2 and C-3 pedicle screws resulted in a consistent increase in stiffness, and hence in stability, over intact specimens.

Evaluation of occipitocervical subluxation in rheumatoid arthritis patients, using coronal-view reconstructive computed tomography.

STUDY DESIGN: Reconstructive computed tomography (CT) study of occipito-atlanto and atlantoaxial joints in RA patients. SUMMARY OF BACKGROUND DATA: The occipitocervical region is one of the most common sites of rheumatoid arthritis (RA). Although lateral radiography has been used for the diagnosis of atlantoaxial subluxation and vertical subluxation, reconstructive CT imaging of the occipito-atlanto and atlantoaxial joints is more sensitive in detecting morphologic changes in this region. We investigated this region in RA patients, using coronal-view reconstructive CT images, and examined the relationship between the morphology and other radiographic parameters. METHODS: The occipitocervical region was examined in 58 female RA patients by reconstructive CT, plain radiography, and MRI. The degree of destructive change on reconstructive CT was compared to that on other radiographic evaluations. RESULTS: Coronal-view reconstructive CT revealed primary destructive changes before detection by lateral radiography, using Redlund-Johnell or Ranawat values. A Redlund-Johnell value less than 34 mm was diagnostic for occipitocervical subluxation in female RA patients. CONCLUSION: Coronal-view reconstructive CT is useful for the diagnosis of occipitocervical joint subluxation in RA.

Sleep apnea in rheumatoid arthritis patients with occipitocervical lesions: the prevalence and associated radiographic features.

Since sleep apnea is a risk factor for high mortality of rheumatoid arthritis (RA) patients, this study examined the prevalence in RA patients with occipitocervical lesions, and the associated radiographic features. Twenty-nine RA patients requiring surgery for progressive myelopathy due to occipitocervical lesions (3 males, 26 females, average age 65 years) were preoperatively evaluated. Twenty-three (79%) had sleep apnea defined as apnea-hypopnea index >5 events per hour measured by a portable monitoring device, and all of them were classified as the obstructive type. Among gender, age, bone mass index (BMI), and radiographic parameters related to occipitocervical lesions: atlantodental interval (ADI), cervical angles (O/C1, C1/2, and C2/6), and cervical lengths (O-C2 and O-C6), the ADI and cervical lengths were shown to be significantly associated with the presence of sleep apnea by parametric statistical analysis. Since there were positive correlations between the ADI and cervical lengths by Pearson's test, we performed a multivariate logistic regression analysis after adjustment for confounding factors and found that small ADI was the principle parameter associated with sleep apnea. We therefore conclude that the prevalence of sleep apnea is higher than that in a general RA population that was reported previously, and believe that occipitocervical lesions are an independent risk factor for this condition. Small ADI and short neck, secondary to the vertical translocation by RA, may cause obstructive sleep apnea, probably through mechanical or neurological collapse of the upper airway.

C2-fractures: part II. A morphometrical analysis of computerized atlantoaxial motion, anatomical alignment and related clinical outcomes.

Knowledge on the outcome of C2-fractures is founded on heterogenous samples with cross-sectional outcome assessment focusing on union rates, complications and technical concerns related to surgical treatment. Reproducible clinical and functional outcome assessments are scant. Validated generic and disease specific outcome measures were rarely applied. Therefore, the aim of the current study is to investigate the radiographic, functional and clinical outcome of a patient sample with C2-fractures. Out of a consecutive series of 121 patients with C2 fractures, 44 met strict inclusion criteria and 35 patients with C2-fractures treated either nonsurgically or surgically with motion-preserving techniques were surveyed. Outcome analysis included validated measures (SF-36, NPDI, CSOQ), and a functional CT-scanning protocol for the evaluation of C1-2 rotation and alignment. Mean follow-up was 64 months and mean age of patients was 52 years. Classification of C2-fractures at injury was performed using a detailed morphological description: 24 patients had odontoid fractures type II or III, 18 patients had fracture patterns involving the vertebral body and 11 included a dislocated or a burst lateral mass fracture. Thirty-one percent of patients were treated with a halo, 34% with a Philadelphia collar and 34% had anterior odontoid screw fixation. At follow-up mean atlantoaxial rotation in left and right head position was 20.2 degrees and 20.6 degrees, respectively. According to the classification system of posttreatment C2-alignment established by our group in part I of the C2-fracture study project, mean malunion score was 2.8 points. In 49% of patients the fractures healed in anatomical shape or with mild malalignment. In 51% fractures healed with moderate or severe malalignment. Self-rated outcome was excellent or good in 65% of patients and moderate or poor in 35%. The raw data of varying nuances allow for comparison in future benchmark studies and metaanalysis. Detailed investigation of C2-fracture morphology, posttreatment C2-alignment and atlantoaxial rotation allowed a unique outcome analysis that focused on the identification of risk factors for poor outcome and the interdependencies of outcome variables that should be addressed in studies on C2-fractures. We recognized that reduced rotation of C1-2 per se was not a concern for the patients. However, patients with worse clinical outcomes had reduced total neck rotation and rotation C1-2. In turn, C2-fractures, especially fractures affecting the lateral mass that healed with atlantoaxial deformity and malunion, had higher incidence of atlantoaxial degeneration and osteoarthritis. Patients with increased severity of C2-malunion and new onset atlantoaxial arthritis had worse clinical outcomes and significantly reduced rotation C1-2. The current study offers detailed insight into the radiographical, functional and clinical outcome of C2-fractures. It significantly adds to the understanding of C2-fractures.

Spontaneous rotatory atlantoaxial dislocation without neurological compromise in a child with Down syndrome: a case report.

Spontaneous atlantoaxial dislocation is a rare recognised complication of Down syndrome. In the majority of cases, dislocation takes place in an anteroposterior direction and is often associated with abnormalities of odontoid development or ossification. Rotatory atlantoaxial dislocation is extremely rare in Down syndrome and this is to our knowledge the first reported case in which modern imaging methods have been described; surface shaded reformats derived from a multislice CT scan were of fundamental importance in making the diagnosis.

Using peripheral stimulation to reduce the pain of C2-mediated occipital headaches: a preliminary report.

BACKGROUND: Peripheral nerve stimulation (PNS) is an accepted treatment for neuropathic pain. Recent studies have focused on its potential for relieving headache pain. OBJECTIVES: To investigate the effectiveness of PNS in reducing occipital headache pain. DESIGN: A prospective, 12-week pilot study involving 11 patients evaluated before and after implantation of PNS systems to treat C2-mediated occipital headaches. METHODS: Prior to and at 4 and 12 weeks after implantation, patients completed the Short-Form McGill Pain Questionnaire (SF-MPQ), Visual Analog Scale (VAS), and Present Pain Index (PPI). Patients also answered questionnaires and kept diaries to record stimulator use, medication consumption, and numbers of headaches. RESULTS: A comparison of pre- and post-implantation evaluations showed statistically significant declines in scores on the SF-MPQ (64%; p = 0.0013), VAS (67%; p < 0.0001), and PPI (68%; p = 0.0009). Most patients (91% and 64% respectively) reported reductions in medication use and numbers of headaches. Patients also reported a reduction in headache symptoms and the impact of headaches on activities. Two adverse events were encountered, one due to a loose connection and, the other caused by lead migration. CONCLUSIONS: PNS reduced headache pain, headache frequency and medication use.

Intraoperative dynamic angiography to detect resolution of Bow Hunter's syndrome: Technical case report.

BACKGROUND: Bow Hunter's syndrome is a rare form of vertebrobasilar insufficiency that may be successfully treated by surgical intervention. Use of intraoperative dynamic transcranial Doppler ultrasound for surgical treatment of vertebrobasilar insufficiency has been described in literature. However, this technique was inconsistent and unreliable in some patients. We present a case of a patient with Bow Hunter's syndrome treated surgically and emphasize the valuable addition of intraoperative dynamic angiography to determine resolution of vertebral artery compromise. CASE DESCRIPTION: The patient was a 58-year-old man with complaints of dizziness, vertigo, and near-syncopal episodes that occurred when he rotated his head to the left. Imaging revealed compromise of the dominant left vertebral artery with leftward head rotation. An anterior cervical approach with decompression of the left subaxial vertebral artery was performed. Significant osteophyte formation was observed. Removal of bone and decompression of the vertebral artery was performed. Intraoperative dynamic angiography confirmed resolution of vertebral artery compression and minimized the amount of decompression. No further intervention was required. CONCLUSION: Intraoperative dynamic angiography is a definitive test to determine hemodynamic resolution of Bow Hunter's syndrome. It offers real-time feedback of vertebral artery decompression, potentially minimizes the amount of decompression, and can be performed safely.

Axial loading with hyperflexion injury to the atlas resulting in crushed lateral masses.

A 40-year-old man was involved in an ATV accident, in which he landed on the top of his head. There was no neurological deficit. A plain radiograph showed prevertebral soft tissue swelling at the atlas and axis level. Computed tomography (CT) demonstrated vertical fractures of the anterior aspects of both lateral masses of the atlas, extending to the junction of the lateral mass with the anterior arch bilaterally. There was no lateral offset of the lateral masses. The mechanism of injury is believed to be axial loading along with hyperflexion.