A novel computed tomography scoring system for evaluating the risk of dural defects in anterior surgery for cervical ossification of the posterior longitudinal ligament.

OBJECTIVE: To develop and validate a computed tomography (CT)-based scoring system for evaluating the risk of dural defects (DDs) in anterior surgery for cervical ossification of the posterior longitudinal ligament (OPLL). METHODS: We retrospectively analyzed CT imaging features of 114 OPLL patients in our institute who received anterior decompression surgery. Intraoperative DDs were found in 16 patients. A multivariable logistic regression was used to evaluate the predictors. According to the odd ratio of the included risk factors, we developed a CT scoring system for evaluating the risk of DDs in anterior OPLL surgery. The system was further validated in an independent group of 39 OPLL patients. RESULTS: We developed a CT scoring system as follows: hook sign (2 points), K-line (-) (1 point) and broad base (1 point). Thus, the system comprised 4 total points, and patients were at high risks of dural defects when the score ≥3 points. The operating characteristics of a score ≥3 for predicting DDs in the validation group were: sensitivity of 0.83, specificity of 0.94, LR positive of 13.75, LR negative of 0.18 and AUC of 0.886. The discriminatory ability of the proposed score could be demonstrated in the validation cohort. CONCLUSIONS: The relatively simple and easy-to-use scoring system we propose integrates the 3 most reliable spinal CT findings observed in patients with OPLL and a DD. The likelihood to identify the underlying risks of spinal CSF leaks may be useful to triage patients who may benefit from indirect decompression techniques.

Predictors for Development of Symptomatic Myelopathy in Patients with Radiculopathy Caused by Cervical Ossification of Posterior Longitudinal Ligament.

OBJECTIVE: To identify clinical factors predicting the development of myelopathy in cervical ossification of the posterior longitudinal ligament (OPLL) patients with radiculopathy. METHODS: We retrospectively reviewed 83 cervical OPLL patients who presented with radiculopathy. On the basis of the symptoms and physical findings, we divided patients into 2 groups: myelopathy group and nonmyelopathy group. Demographic, clinical, and radiologic characteristics were reviewed and analyzed among the 2 groups. Predictors for the development of myelopathy were assessed via univariate and multivariate analysis. RESULTS: Univariate analysis demonstrated that a high occupying ratio and the presence of an intramedullary high signal were risk factors for development of myelopathy from radiculopathy in OPLL patients. Multivariate analysis further identified that a high occupying ratio was the only independent predictor (odds ratio 1.05, 95% confidence interval 1.003-1.091, P = 0.035). The cervical range of motion and minor trauma were not related to the development of myelopathy in our study. CONCLUSIONS: Nonmyelopathic OPLL patients with radiculopathy and a high occupying ratio were at higher risk of developing myelopathy, and surgical intervention should be recommended in these cases. However, for elderly patients with significant comorbid conditions, the risks and benefits of surgery should be carefully considered.

Carotid Artery-Related Perioperative Stroke Following Anterior Cervical Spine Surgery: A Series of 3 Cases and Literature Review.

BACKGROUND: Vascular complications following anterior cervical spine surgery are rare but potentially devastating. Complications associated with the carotid artery are even more disastrous but largely anecdotal, with no more than 4 reported cases. MATERIALS AND METHODS: We report 3 new cases of carotid artery-related perioperative stroke following anterior cervical spine surgery. All 3 patients had carotid artery atherosclerosis and the time of intraoperative carotid artery retraction was longer than 1 hour. One patient underwent hypotension during surgery. Risk factors as well as prevention and management protocols of carotid artery-related perioperative stroke based on the literature review and our clinical experience are discussed. CONCLUSIONS: Carotid artery-related perioperative stroke following anterior cervical spine surgery is extremely rare. Prolonged traction, carotid artery atherosclerosis, and intraoperative hypotension can produce cerebral hypoperfusion and cause ischemic stroke. Preoperative risk assessment, adequate perioperative manipulation, and postoperative management can minimize overall morbidity and mortality.

Computed Tomography Imaging Study of Basilar Invagination and Atlantoaxial Dislocation.

OBJECTIVE: We sought to analyze axis deformities and the biomechanics related to atlantoaxial dislocation (AAD) in patients with basilar invagination (BI). METHODS: Seventy-six patients were retrospectively analyzed including 21 patients who had BI (group B), 32 patients with BI and AAD (group C), and 23 nondeformity control subjects (group A). Using 3-dimensional computed tomography imaging the distance from the tip of the dens above the Chamberlain line in the sagittal plane, atlantodental interval, sagittal inclination, coronal inclination, and craniocervical tilt, the height of the odontoid and ratio of the height to the odontoid basal width were measured in each patient. We statistically analyzed the resulting data for correlations among physiologic measurements and disease state. RESULTS: The height of the odontoid process in groups A, B, and C was 13.38 ± 1.50 mm, 10.87 ± 1.48 mm, and 8.49 ± 2.49 mm, respectively. The ratio of height-to-basal width of the odontoid in groups A, B, and C was 1.32 ± 0.21, 0.91 ± 0.21, and 0.65 ± 0.17, respectively. The sagittal inclination in groups A, B, and C was 85.85 ± 4.55 degrees, 105.76 ± 10.72 degrees, and 123.48 ±12.43 degrees, and the coronal inclination was 108.95 ± 24.09 degrees, 105.40 ± 25.16 degrees, and 108.82 ± 21.41 degrees, respectively. The craniocervical tilt in groups A, B, and C was 60.31 ± 6.98 degrees, 84.53 ± 18.94 degrees, and 71.79 ± 11.69 degrees, respectively. The height of the odontoid, height-to-basal width, and sagittal inclination were significantly correlated with both BI and AAD (P < 0.001). Odontoid height and height-to-basal width ratio were significantly correlated with BI, AAD, and sagittal inclination (P < 0.001). Finally, craniocervical tilt was correlated only with the BI severity (P < 0.001). CONCLUSION: This study confirms that deformities of the odontoid process and the lateral joint correlate with severity of BI, while deformity of the odontoid process may be a primary factor in AAD for patients with BI.

Risk Factors and Management of Dural Defects in Anterior Surgery for Cervical Ossification of the Posterior Longitudinal Ligament.

OBJECTIVE: To investigate risk factors and outcomes and to develop a cogent perioperative management algorithm for dural defects (DDs) in anterior surgery for cervical ossification of the posterior longitudinal ligament (OPLL). METHODS: Ninety OPLL patients who had undergone anterior cervical decompression between January 2014 and December 2016 were reviewed. DDs occurred in 12 patients. Demographic, clinical, and radiologic data; intraoperative and postoperative management; and complications were analyzed. Risk factors for DDs were assessed with multivariate analysis. A treatment algorithm was identified based on these findings and our experience. RESULTS: The prevalence of DDs was 13.3% (12/90). Univariate and multivariate analyses showed that the ratio of OPLL base to spinal canal (odds ratio [OR] 1.09, P = 0.012), kyphotic cervical alignment with thick OPLL masses (OR 9.44, P = 0.026), and lateral, curved, and irregular OPLL masses (OR 8.28, P = 0.037) could be risk factors for DDs. DDs were repaired intraoperatively with onlay grafts, and lumbar drains were placed in all DD patients. The treatment was successful in all DD patients, and outcome measures did not differ between the DD and no DD groups. No patient had experienced complications associated with DDs and CSF leaks at the final follow-up visit. CONCLUSIONS: Patients with broad-based OPLL, kyphotic cervical alignment with thick OPLL masses, and lateral, curved, and irregular OPLL masses have a higher risk of DD in anterior surgery for OPLL. Intraoperative primary repair with onlay grafts combined with early lumbar drains is a simple, safe, and effective strategy for DDs. The outlook for the long-term sequelae of DDs is optimistic if they are managed adequately.

Modulation of C-nociceptive Activities by Inputs from Myelinated Fibers.

To understand the mechanisms of neuropathic pain caused by demyelination, a rapid-onset, completed but reversible demyelination of peripheral A-fibers and neuropathic pain behaviors in adult rats by single injection of cobra venom into the sciatic nerve, was created. Microfilament recording revealed that cobra venom selectively blocked A-fibers, but not C-fibers. Selective blockade of A-fibers may result from A-fiber demyelination at the site of venom injection as demonstrated by microscope examination. Neuropathic pain behaviors including inflammatory response appeared almost immediately after venom injection and lasted about 3 weeks. Electrophysiological studies indicated that venom injection induced loss of conduction in A-fibers, increased sensitivity of C-polymodal nociceptors to innocuous stimuli, and triggered spontaneous activity from peripheral and central terminals of C-fiber nociceptors. Neurogenic inflammatory responses were also observed in the affected skin via Evans blue extravasation experiments. Both antidromic C-fiber spontaneous activity and neurogenic inflammation were substantially decreased by continuous A-fiber threshold electric stimuli applied proximally to the venom injection site. The data suggest that normal activity of peripheral A-fibers may produce inhibitory modulation of C-polymodal nociceptors. Removal of inhibition to C-fiber polymodal nociceptors following demyelination of A-fibers may result in pain and neurogenic inflammation in the affected receptive field.

Mechanisms of topical analgesics in relieving pain in an animal model of muscular inflammation.

OBJECTIVE: To investigate the possible mechanisms of topical analgesics in relieving pain in an animal model of muscular inflammation. METHODS: Adult Sprague-Dawley rats of both sexes were injected with complete Freund's adjuvant to induce inflammation in the anterior tibialis muscle of left hindlimb. One of two types of topical analgesics: Xiaotong Tiegao (XTT), a Tibetan herb compound, or Capzasin (CAP), a cream containing 0.1% capsaicin, was applied to the skin over the inflamed anterior tibialis muscle. The following experiments were performed: pain behavioral tests, evaluation of plasma extravasation in the affected limb, and electrophysiological recordings of afferent nerve fibers. RESULTS: The behavioral experiments demonstrated that applications of either type of topical analgesic to the skin over the inflamed muscle significantly reduced muscular inflammatory pain, as indicated by the increased weight bearing capacity on the affected hindlimb (with latencies of 10 minutes for XTT and 1-2 hours for CAP). Meanwhile, both analgesics caused plasma extravasation in the affected skin. Electrophysiological recordings from the afferent fibers in the related cutaneous nerve indicated that topical analgesics selectively activated C-fibers, but not A-fibers innervating the same region of receptive field. The latency and duration of C-fiber activation was similar to those of the reduction of muscular inflammatory pain. On the contrary, topical analgesics substantially decreased C-fiber afferent spontaneous firing in the nerve innervating the inflamed muscle. Moreover, denervation of the affected skin blocked the analgesic effects of both topical analgesics in muscular inflammatory pain. CONCLUSION: This study suggests that topical analgesics may reduce the nociceptive input from inflamed muscles via a reflex mechanism by activating the cutaneous nociceptive afferents.

[Dendritic projections from meridian-related motoneurons to sympathic preganglion neurons in the spinal cord of rats].

OBJECTIVE: Previous studies indicated a close involvement of reflex activities of motoneurons in the spinal cord in the mechanism of meridian phenomena. The present study was designed to investigate the dendrite projections of meridian-related motoneurons among the motoneurons and sympathetic preganglionic neurons in the spinal cord. METHODS: A total of 41 Sprague-Dawley rats were used in the present study. Cholera toxin B-subunit conjugated horseradish peroxidase (CB-HRP) containing 1.0% HRP was respectively injected to acupoint "Chengman" (ST 20), "Liangmen" (ST 21), "Guanmen" (ST 22), "Taiyi" (ST 23), "Huaroumen" (ST 24), "Tianshu" (ST 25) and "Wailing" (ST 26) of the Stomach Meridian, and "Ganshu" (BL 18), "Danshu" (BL 19), "Pishu" (BL 20), "Weishu" (BL 21) and "Sanjiaoshu" (BL 22) of the Bladder Meridian, and "Daimai" (GB 26), "Wushu" (GB 27), "Weidao" (GB 28), "Juliao" (GB 29), "Huantiao" (GB 30), "Fengshi" (GB 31), "Zhongdu" (GB 32), "Xiyangguan" (GB 33) and "Yanglingquan" (GB 34) of the Gallbladder Meridian (for labeling preganglionic neurons), and the celiac ganglion and superior mesenteric ganglion for labeling sympathetic preganglionic neurons. Three days after injection, the animals anesthetized were transcardia-cally perfused with 1.5% paraformaldehyde, the spinal cord was removed to be fixed routinely and then cut into sections for observing the labeled cells under microscope. RESULTS: In the ipsilateral ventral horn of the spinal cord, the motoneurons retrogradely labeled by CB-HRP formed dendritic projections oriented only to those motoneurons innervating the same meridian. In the longitudinal sections of spinal cord, the labeled motoneurons formed a bead-like column with a prominent network of longitudinal dendrites connecting the motoneurons innervating acupoints from the same meridian. In the transverse sections of spinal cord, two groups of dendrites from the labeled motoneurons projected to the identified sympathetic preganglionic regions: one group extended dorsolateraly to the intermediolateral gray, another group extended intermediolateraly toward the central canal. In rats with injection of CB-HRP into both acupoint regions and ipsilateral celiac ganglion, the dendrites originated from the labeled motoneurons projected directly to the labeled sympathetic preganglionic neurons. CONCLUSION: Each of the ST, BL and GB meridians is innervated by a specific group of motoneurons in the spinal cord. The motoneurons form a column with distinct border in the ventral horn of spinal cord, and the dendritic projections from the motoneurons oriented only to those innervating the same meridian. The dendrites from the meridian-related motoneurons can specifically project to the sympathetic preganglionic neurons at the thoracolumbar level.