Compression of Thoracic Spinal Cord with Decreased Cerebrospinal Fluid Space After Implantation of Paddle Lead Spinal Cord Stimulation at T9: A Three-Dimensional Myelographic Computed Tomography Study.

OBJECTIVES: To investigate the extent of spinal cord compression and cerebrospinal fluid (CSF) space after T9 paddle lead spinal cord stimulation (SCS) using three-dimensional myelographic computed tomography scans. METHODS: Preoperative and postoperative three-dimensional myelographic computed tomography scans were performed in 15 patients with paddle lead SCS at T9 for neuropathic back and leg pain. Four axial levels between each row of the electrodes were selected and the cross-sectional areas of thecal sac and spinal cord, the width of anterior and posterior CSF space, and contact angle of the lead within T9 spinal canal were measured with 12-month pain relief assessment. RESULTS: The cross-sectional areas of thecal sac and spinal cord under each contact of paddle leads decreased significantly (23.89 ± 11.48% and 9.45 ± 4.80%; P < 0.05, respectively). The width of posterior CSF space decreased by 38.65 ± 20.97% and that of anterior CSF space showed a greater reduction by 59.09 ± 18.39% (P < 0.05). We achieved a mean pain relief of 45.49 ± 13.73% at 12-month follow-up and found a significant correlation with percentage reduction in the area of the spinal cord. CONCLUSIONS: Significant reduction in the cross-sectional area of spinal cord and anterior CSF space as well as thecal sac and posterior CSF space resulted in deformation of the spinal cord under paddle leads at T9 within 7 postoperative days. Close approximation to the dorsal column and the mass effect of paddle leads may determine the clinical outcome of paddle lead SCS and also raise safety concerns.

Síndrome de hipotensión intracraneal espontánea: aportación de la cisternografía radioisotópica / Spontaneous intracranial hypotension syndrome: contribution of radioisotope cisternography

La hipotensión intracraneal espontánea es un síndrome clínico debido a la pérdida de volumen de líquido cefalorraquídeo, generalmente secundario a su fuga por defectos estructurales de la duramadre espinal. La cisternografía radioisotópica (CR) es una técnica que puede aportar un diagnóstico confirmatorio en este síndrome, principalmente en casos dudosos o de presentación atípica. Estudiamos retrospectivamente 8 pacientes con CR realizada por sospecha de hipotensión intracraneal espontánea con clínica atípica y/o hallazgos no concluyentes en las técnicas de imagen. La CR detectó extravasación paraespinal de líquido cefalorraquídeo en 7 de ellos. Además, se apreciaron signos indirectos de fuga de líquido cefalorraquídeo en los 8 pacientes, consistentes en la presencia precoz del radiotrazador en orina, presencia de actividad de fondo corporal y/o reducción de la cantidad de radiotrazador en cráneo a las 24 h. La CR tuvo un impacto significativo en el diagnóstico de 6 pacientes y en el manejo terapéutico de 4 pacientes (AU)

Spontaneous intracranial hypotension is a clinical syndrome caused by a loss of cerebrospinal fluid volume, usually secondary to leaking through structural defects of the spinal dura mater. Radioisotope cisternography (RC) can confirm the diagnosis of spontaneous intracranial hypotension, especially in doubtful or atypical case presentations. A retrospective study was conducted on 8 patients who underwent RC because spontaneous intracranial hypotension was suspected, and they presented with atypical clinical manifestations and/or inconclusive findings in other imaging techniques. RC detected paradural extravasation of cerebrospinal fluid in 7 patients. Moreover, there was indirect evidence of cerebrospinal fluid leaks in all 8 patients (early appearance of radioactivity in the bladder, soft tissue uptake of radioisotope and/or reduction in the amount of radiotracer in the brain at 24hours). RC had a significant impact on the diagnosis of 6 patients, and on the therapeutic management of 4 patients (AU)

Optimal contrast concentration for CT-guided epidural steroid injections.

BACKGROUND AND PURPOSE: Contrast is used in CT-guided epidural steroid injections to ensure proper needle placement. Once injected, undiluted contrast often obscures the needle, hindering subsequent repositioning. The purpose of this investigation was to establish the optimal contrast dilution for CT-guided epidural steroid injections. MATERIALS AND METHODS: This investigation consisted of an initial phantom study, followed by a prospective, randomized, single-center trial assessing a range of contrast dilutions. In the phantom study, a phantom housing a chamber containing a 22-gauge needle and various dilutions of contrast was scanned, and images were evaluated for needle visibility. On the basis of these results, concentrations of 66, 100, 133, and 150 mg/mL iodine were selected for evaluation in a clinical study. Patients presenting for CT-guided epidural steroid injections were randomly assigned to a contrast dilution, and images from the procedure were evaluated by 2 readers blinded to the contrast assignment. Needle visibility was scored by use of a 5-point scale. RESULTS: In the phantom study, the needle was not visible at contrast concentrations of ≥133 mg/mL. In the clinical study, needle visibility was strongly associated with contrast concentration (P < .0001). Significant improvements in visibility were found in 66 mg/mL and 100 mg/mL compared with higher iodine concentrations; no difference was found comparing 66 mg/mL with 100 mg/mL iodine. Neither injection location (cervical versus lumbar) nor technique (interlaminar versus transforaminal) influenced visibility scores. CONCLUSIONS: For CT-guided epidural steroid injections, the optimal contrast concentration is 66-100 mg/mL iodine. Because these concentrations are not commercially available, proceduralists must dilute their contrast for such procedures.

New generation intraoperative three-dimensional imaging (O-arm) in 100 spine surgeries: does it change the surgical procedure?

The O-arm (Medtronic Sofamor Danek, Inc., Memphis, TN, USA), an intraoperative CT scan imaging system, may provide high-quality imaging information to the surgeon. To our knowledge, its impact on spine surgery has not been studied. We reviewed 100 consecutive spine surgical procedures which utilized the new generation mobile intraoperative CT imaging system (O-arm). The most common diagnoses were degenerative conditions (disk disease, spondylolisthesis, stenosis and acquired kyphosis), seen in 49 patients. The most common indication for imaging was spinal instrumentation in 81 patients (74 utilized pedicle screws). In 52 (70%) of these, the O-arm was used to assess screw position after placement; in 22 (30%), it was coupled with Stealth navigation (Medtronic Sofamor Danek, Inc.) to guide screw placement. Another indication was to assess adequacy of spinal decompression in 38 patients; in 19 (50%) of these, intrathecal contrast material was used to obtain an intraoperative CT myelogram. In 20 patients O-arm findings led to direct surgeon intervention in the form of screw removal/repositioning (n=13), further decompression (n=6), interbody spacer repositioning (n=1), and removal of kyphoplasty trocar (n=1). In 20% of spine surgeries, the procedure was changed based on O-arm imaging findings. We found the O-arm to be useful for assessment of instrumentation position, adequacy of spinal decompression, and confirmation of balloon containment and cement filling in kyphoplasty. When used with navigation for image-guided surgery, it obviated the need for registration.

Use of flat panel DynaCT myelography to locate the site of CSF leak.

Spontaneous intracranial hypotension is often treated conservatively or with epidural blood patch. Patients who are resistant to these treatments require accurate imaging localisation of the site of cerebrospinal fluid (CSF) leak for surgical repair. We describe two patients where MRI, CT myelography and MRI gadolinium myelography showed evidence of a large volume of epidural CSF, but failed to identify the pressure site of leak. Subsequently, DynaCT (Siemens, Erlangen, Germany) accurately identified the site with confidence in both cases, confirmed at surgery. This technique of using a flat panel detector-based, angiographic system to produce high quality, high-contrast multiplanar CT images for detecting the source of rapid CSF leak is detailed.

Evaluation of angiographically occult spinal dural arteriovenous fistulae with surgical microscope-integrated intraoperative near-infrared indocyanine green angiography: report of 3 cases.

BACKGROUND: Spinal dural arteriovenous fistulae (dAVFs), are lesions involving an aberrant connection between a radicular feeding artery and the venous system of the spinal cord at the dural sleeve of the nerve root. When rare dAVFs are occult on digitally subtracted catheter-based angiography, they present a diagnostic and therapeutic challenge. OBJECTIVE: We report 3 cases of angiographically occult spinal dAVFs that were evaluated during surgery with indocyanine green (ICG) fluorescent microscope-integrated angiography. METHODS: Three patients with clinical and magnetic resonance imaging features suggestive of a spinal dAVF but no abnormality on digital subtraction angiography underwent surgical exploration with the aid of microscope-integrated ICG videoangiography. RESULTS: In all 3 cases, ICG identified the intradural vein draining the fistula, clearly distinguishing it from an artery or uninvolved medullary vein. CONCLUSION: ICG angiography can rapidly identify a draining vein as it enters the spinal canal even in dAVFs not identifiable on catheter-based digital subtraction angiography.

Toward more useful pressure-controlled discography: in vitro evaluation of injection speed, sensor location, and tube length.

OBJECTIVE: Pressure-controlled manometric discography is used by clinicians to evaluate discogenic pain. However, some would improve diagnostic accuracy. The goal of this study was to investigate potential confounding factors that might affect discographic results. Pressure differences depending on different speed of injection, lengths of connecting tubing and locations of sensors were evaluated using an in vitro model system. METHODS: Two sets of automated discography devices were arranged to record post-syringeal pressure pressures (PSPs) and intradiscal pressures (IDPs) in an "air chamber disk model" representing intradiscal pressure. PSPs and IDPs were measured simultaneously while varying injection speeds, and using intrasyringeal and extrasyringeal pressure sensors and contrast medium-filled tubing of different lengths. All pressure/volume curves were collected and viewed dynamically, and stored for further analysis. RESULTS: At injection speed of 0.1 cc/second, the mean pressure difference (mean ΔP) between PSP and IDP was 38.1 psi. As injection speed was reduced, mean ΔP was proportionally decreased. Mean ΔP was 5.3 psi at injection speed of 0.01 cc/second and 0.7 psi at 0.005 cc/second. Mean ΔP values were significantly higher when pressures were recorded using intrasyringeal sensor: at injection speed of 0.1 cc/second, PSP and IDP values were 82.9 and 30.1 psi, respectively, compared with 50.6 and 12.5 psi measured by extrasyringeal sensor. Mean ΔP due to increased length of tubing was not significant. CONCLUSION: Discography can be better performed with low speed injection (≤0.01 cc/second), using an extrasyringeal sensor. Difference of length of connecting tubings did not cause significant pressure differences. These data suggest that automated discography is a helpful adjunct to improve diagnostic accuracy, due to extrasyringeal location of pressure sensor and greater control of injection speed.

Comparison of spinal anatomy between 3-Tesla MRI and CT-myelography under healthy and pathological conditions.

PURPOSE: In many centres both MRI and CT-myelography are performed for treatment planning of degenerative spine disease. More and more centres acquire 3-Tesla MRI scanners in which some artefacts, which lead to difficulties in image evaluation, are more pronounced than at 1.5 Tesla. Aim of this study was to compare spinal physiological and pathological anatomy between 3-Tesla MRI and CT-myelography and to review current imaging standards. METHODS: In 47 spinal segments commonly used 3-Tesla T2-weighted sequences and CT-myelography studies were evaluated retrospectively. Spinal canal, neural foraminal, spinal cord and disc protrusion diameters were measured. RESULTS: The spinal canal was found to be 10% tighter with the utilized MRI sequences, in comparison to CT-M and foraminal diameters were found to be 19.7% tighter in MRI. This was more pronounced in narrowed than in healthy segments. Spinal cord size and size of disc protrusions displayed no significant difference between MRI and CT-myelography. CONCLUSIONS: The main advantage of CT-myelography, in comparison to 3-Tesla MRI, is the reliable information about the bony structures. Soft tissues like the spinal cord or disc protrusions were visualised equivalently with both modalities concerning diameters.

CyberKnife stereotactic radiotherapy for spinal tumors: value of computed tomographic myelography in spinal cord delineation.

OBJECTIVE: For para- and intraspinal tumors, precise spinal cord delineation is critical for CyberKnife (Accuray, Inc., Sunnyvale, CA) stereotactic radiotherapy. We evaluated whether computed tomographic (CT) myelography is superior to magnetic resonance imaging (MRI) for accurate spinal cord delineation. Treatment parameters and short-term outcome and toxicity are also presented. METHODS: The planning CT scan, the gadolinium-enhanced, T1-weighted, 3-dimensional (3D) fast imaging employing steady-state acquisition MRI scan, and the CT myelogram were fused before volume-of-interest delineation. The planning target volume margin was less than 1 mm using the Xsight Spine tracking system (Accuray). We present data from 11 heavily pretreated patients who underwent CyberKnife stereotactic radiosurgery between November 2006 and January 2008. RESULTS: Spatial resolution was 0.46 and 0.93 mm/pixel for CT myelography and 3D-fast imaging employing steady-state acquisition MRI, respectively. The contrast between cerebrospinal fluid and spinal cord was excellent with CT myelography. A transient postmyelography headache occurred in 1 patient. The mean gross tumor volume was 51.1 mL. The mean prescribed dose was 34 Gy in 4 fractions (range, 2-7 fractions) with 147 beams (range, 79-232 beams) to the 75% reference isodose line (range, 68-80%), covering 95% (range, 86-99%) of the gross tumor volume with a mean conformity index of 1.4 (range, 1.1-1.8). No short-term toxicity on the spinal cord was noted at 1- to 6-months of follow-up. CONCLUSION: CT myelography was more accurate for spinal cord delineation than 3D-fast imaging employing steady-state acquisition MRI (used for its myelographic effect), particularly in the presence of ferromagnetic artifacts in heavily pretreated patients or in patients with severe spinal compression. Because other MRI sequences (T2 and gadolinium-enhanced T1) provide excellent tumor characterization, we suggest trimodality imaging for spinal tumor treatment to yield submillimetric delineation accuracy. Combined with CyberKnife technology, CT myelography can improve the feasibility of dose escalation or reirradiation of spinal tumors in selected patients, thereby increasing local control while avoiding myelopathy. Further follow-up and prospective studies are warranted.

Dynact soft-tissue visualization using an angiographic C-arm system: initial clinical experience in the operating room.

INTRODUCTION: DynaCT is a clinical application protocol to create computed tomographic (CT)-like images allowing soft-tissue visualization acquired from an angiography system. A cone beam three-dimensional CT reconstruction is produced from the acquisition of two-dimensional projection images by rotating the c-arm with x-ray source and image receptor around the patient. The purpose of this study is to evaluate the clinical efficacy of DynaCT in the operating room. METHODS: DynaCT was performed in 100 patients undergoing cerebral or spinal interventional procedures in the new-concept operating room. Specially designed AXIOM Artis BA (conventional image intensifier system; 55 patients; Siemens Medical Solutions, Erlangen, Germany) and AXIOM Artis dBA (flat-panel detector; 45 patients; Siemens Medical Solutions) biplane neuroangiographic systems (Siemens Medical Solutions, Germany) were installed in the operating room. The volumetric data set from the AXIOM Artis systems were reconstructed immediately on the three-dimensional workstation in the operating room. We compared DynaCT images with the use of multidetector computed tomography. RESULTS: DynaCT was performed successfully in all patients. High-contrast structures, such as bone, calcified lesions, and metallic materials, were visualized on DynaCT as well as in multidetector computed tomography for each group. Although contrast differentiation of soft tissue such as cerebral cortex, muscle, and hematoma on DynaCT were inferior to multidetector CT scans, the images were sufficiently used as intraoperative CT-like images. However, DynaCT images acquired from flat panel detector-based systems were found to be superior to those images acquired from image intensifier-based systems. Striking ring artifacts were exhibited and resulted in major limitations in the image intensifier group. CONCLUSION: DynaCT has the potential to be used as a powerful tool for endovascular and neurosurgical procedures and will open new possibilities for neurosurgical management.

Myelographic abnormalities of spinal cord and nerve roots lesions in conventional myelography.

The authors review the myelographic abnormalities of spinal lesions on 90 patients evaluated with conventional or fluoroscopy myelography between 1989 and 1995. The value of Conventional myelography in spinal lesions involving the spinal cord and nerve roots are assessed. The subjects include 49 (45.4%) males and 41 (45.6%) females with a mean age of 38.3 years. Majority of the cases 74(82.2%) had specific neurological symptoms while 16 (17.8%) presented with non-specific neurological symptoms. On the whole 78 (86.7%) cases were successfully analysed, in which 58 (74%) cases had abnormal myelograms and 20 (25.5%) had normal myelograms. Extradural lesions was seen in 47 (81%) cases, while 6 (10.3%) cases and 2 (3.5%) cases showed Intramedullary and Intradural-extramedullary lesions respectively. 3 (5.2%) cases showed combined lesions. The most common anatomical site or location of abnormal myelograms was the Thoracic region with 31 (53.4%) cases, 16 (27.6%) cases in the lumbar, 10 (17.2%)and 1 (1.8%) cases in the cervical and sacral regions respectively. Conventional myelography can be successfully used to demonstrate myelographic abnormalities, including identification and determination of the extent of the anatomical location of spinal lesions.

[Intraoperative three-dimensional imaging to monitor selective decompression in lumbar spinal stenosis]. / Intraoperative 3D-Bildgebung zur Kontrolle der selektiven Dekompression bei lumbaler Wirbelkanalstenose.

BACKGROUND: We are looking for a possibility to examine the amount of decompression in operations for spinal stenosis with an Iso-C(3D) fluoroscope (Siemens). METHODS: In ten patients operated on because of spinal stenosis from one side with undercutting, we performed a scan with the Iso-C(3D) fluoroscope during the operation. In five patients we additionally performed intraoperative myelography. RESULTS: In all cases we were able to make useful scans. Two times we changed our surgical procedure because of the scans. There were no complications because of the investigation with the Iso-C(3D) fluoroscope and none related to the myelography, but the myelography was dispensable. CONCLUSIONS: It is possible and useful to investigate the decompression in spinal stenosis intraoperatively with less effort.

[Myelography, can it be performed as an outpatient procedure?]. / Myelografi, kan det gøres ambulant?

The modern contrast agents used today in myelography cause far fewer complications than earlier. This development has opened up the prospect of undertaking myelography as an outpatient procedure. The complications that can occur after the myelography are, for the great majority known, benign, and disappear within a few days, mainly headache. The frequency of minor complications can be minimised by the use of a smaller gauge and/or a rounded needle tip. When the procedure is done by experienced personnel with non-toxic antiseptic preparation, the complications seem to be similar in frequency, magnitude, and type to a simple diagnostic spinal tap. Positioning of the patients after the examination does not affect the frequency or seriousness of the complications. Our study of the patients' attitude towards outpatient myelography shows great satisfaction with the procedure. We therefore conclude that there is no added risk in performing outpatient myelography; the only noticeable complication is headache, which seldom needs intervention, and there are considerable benefits for both patients and hospital in an outpatient procedure.

[Introduction of a new mobile C-arm/CT combination equipment (ISO-C-3D). Initial results of 3-D sectional imaging]. / Vorstellung eines neuen mobilen C-Bogen-/CT-Kombinationsgerät (ISO-C-3D). Erste Ergebnisse der 3D-Schnittbildgebung.

Preclinical evaluation of a new mobile C-arm image amplifier with an option for three-dimensional computed tomography (CT) imaging (prototype Iso-C3D) with respect to high-contrast resolution and possible clinical applications. Cadaveric specimens (n = 30) of different joints of the lower and upper extremities and specimens of the spinal column were examined with the Iso-C3D and evaluated for image quality. In addition, using a high-contrast phantom (Catphan, Phantom Laboratory, Salem, N.Y., USA) and a fracture model of the femoral bone, measurements of high-contrast resolution were performed in comparison to spiral CT. With the exception of the shoulder, all joint regions including the entire spinal column could be examined. Adequate image quality could be achieved in smaller joints such as the wrist, elbow, ankle, and knee, whereas a remarkably decreased image quality was found when imaging the hip as well as the lumbar and thoracic spine. Images of the phantom study and high-contrast fracture model showed a high-contrast resolution comparable to helical CT (9 Lp/cm in xy-axis). In smaller joints, the image quality of the mobile C-arm CT imaging system (Iso-C3D) is comparable to that of helical CT. Image quality in examinations of the hip and lumbar and thoracic spine seems to be sufficient for intraoperative control studies of osteosynthesis. Problems still occur in shoulder examinations.

Needle diameter in outpatient myelography: rates of adverse effects and current practice trends.

Telephone calls were made to 1251 consecutive patients one day following outpatient myelography. Data were available on 518 patients punctured with 22-gauge (g) (large-diameter) and 465 with 25-g (small-diameter) spinal needles. We surveyed 48 academic and private practice groups regarding needle diameter use in myelography; data were obtained from 34 private practice and 14 academic radiology departments. Patients reported adverse effects including mild and severe headache, back pain and nausea. The percentage of total adverse effects was significantly greater in the 22-g than in the 25-g needle group. The percentage of patients with headache was higher in the 22-g than in the 25-g group, but this difference was not statistically significant. Only 19% of private practice groups and 17% of academic centers use 25-g needles; the remainder use 20-g or 22-g needles.

Discography 2000.

Discography is an invasive and controversial procedure that can be used as a complementary test to MR imaging or a CT myelogram prior to surgery. The examination may be performed in the prone or decubitus position. Pain provocation is the most important part of the examination. CT discography provides valuable information regarding pattern, number, extent, and degree of annular tears. Correlation of discography with cross-sectional imaging studies is reviewed and the surgical outcome is discussed.

Three-dimensional MR myelography of traumatic injuries of the brachial plexus.

PURPOSE: To determine the diagnostic accuracy of three-dimensional MR myelography in the evaluation of traumatic injuries of the brachial plexus. METHODS: Twenty patients with clinical and electromyographic evidence of traumatic brachial plexopathy were examined with three-dimensional MR myelography, conventional cervical myelography, and CT myelography 1 to 9 months after trauma. Three-dimensional MR myelography was performed on a 1.5-T MR unit with a constructive interference in steady state (CISS) technique. For each patient, maximum intensity myelographic projections and multiplanar reconstruction reformatted 1-mm axial sections were obtained from the same 3-D data set. Three-dimensional MR myelographic findings were compared with findings at cervical myelography and CT myelography. Surgical findings were available for comparison in 13 patients. RESULTS: Three-dimensional MR myelography enabled detection of meningoceles with avulsed or intact nerve roots, partial or complete radicular avulsions without disruption of the thecal sac, dural sleeve abnormalities, and dural scars. Assuming cervical myelography and CT myelography as the standards of reference, 3-D MR myelography showed 89% sensitivity, 95% specificity, and 92% diagnostic accuracy in the evaluation of nerve root integrity. CONCLUSION: Three-dimensional MR myelography can show the majority of traumatic lesions that involve the proximal portion of the brachial plexus in a single rapid examination. On the basis of our findings, we propose this technique as a screening examination for patients with traumatic brachial plexus palsy.