Vascular Anatomy of the Cauda Equina and Its Implication on the Vascular Lesions in the Caudal Spinal Structure

Use of corticosteroids for adult chronic pain interventions: sympathetic and peripheral nerve blocks, trigger point injections - guidelines from the American Society of Regional Anesthesia and Pain Medicine, the American Academy of Pain Medicine, the American Society of Interventional Pain Physicians, the International Pain and Spine Intervention Society, and the North American Spine Society

BACKGROUND

There is potential for adverse events from corticosteroid injections, including increase in blood glucose, decrease in bone mineral density and suppression of the hypothalamic-pituitary axis. Published studies note that doses lower than those commonly injected provide similar benefit.

METHODS

Development of the practice guideline was approved by the Board of Directors of American Society of Regional Anesthesia and Pain Medicine with several other societies agreeing to participate. The scope of guidelines was agreed on to include safety of the injection technique (landmark-guided, ultrasound or radiology-aided injections); effect of the addition of the corticosteroid on the efficacy of the injectate (local anesthetic or saline); and adverse events related to the injection. Based on preliminary discussions, it was decided to structure the topics into three separate guidelines as follows: (1) sympathetic, peripheral nerve blocks and trigger point injections; (2) joints; and (3) neuraxial, facet, sacroiliac joints and related topics (vaccine and anticoagulants). Experts were assigned topics to perform a comprehensive review of the literature and to draft statements and recommendations, which were refined and voted for consensus (≥75% agreement) using a modified Delphi process. The United States Preventive Services Task Force grading of evidence and strength of recommendation was followed.

RESULTS

This guideline deals with the use and safety of corticosteroid injections for sympathetic, peripheral nerve blocks and trigger point injections for adult chronic pain conditions. All the statements and recommendations were approved by all participants after four rounds of discussion. The Practice Guidelines Committees and Board of Directors of the participating societies also approved all the statements and recommendations. The safety of some procedures, including stellate blocks, lower extremity peripheral nerve blocks and some sites of trigger point injections, is improved by imaging guidance. The addition of non-particulate corticosteroid to the local anesthetic is beneficial in cluster headaches but not in other types of headaches. Corticosteroid may provide additional benefit in transverse abdominal plane blocks and ilioinguinal/iliohypogastric nerve blocks in postherniorrhaphy pain but there is no evidence for pudendal nerve blocks. There is minimal benefit for the use of corticosteroids in trigger point injections.

CONCLUSIONS

In this practice guideline, we provided recommendations on the use of corticosteroids in sympathetic blocks, peripheral nerve blocks, and trigger point injections to assist clinicians in making informed decisions.

Diagnosis of spinal dural arteriovenous fistula: a multimodal MRI assessment strategy

AIM

To identify more specific screening indicators at magnetic resonance imaging (MRI) for the diagnosis of spinal dural arteriovenous fistulas (SDAVFs) and to determine an efficient diagnostic strategy.

MATERIALS AND METHODS

This retrospective study analysed clinical and imaging data of patients diagnosed with SDAVF and alternative myelopathy who underwent conventional MRI examinations. Additionally, three-dimensional (3D) T2-weighted sampling perfection with application-optimised contrasts using different flip-angle evolutions (3D-T2-SPACE) and contrast-enhanced magnetic resonance angiography (CE-MRA) data from patients with SDAVF were compared with digital subtraction angiography (DSA) data.

RESULTS

The age of onset, perimedullary flow voids (PFV), distribution of lesions, syringomyelia, degree of spinal oedema, and cauda equina disorder (CED) were factors that showed statistically significance in the identification of SDAVF with alternative myelopathy. After controlling for age, gender, PFV, degree of spinal cord swelling, and syringomyelia, the multivariable ordinal logistic regression model showed that the CED sign (OR = 32.46; 95% confidence interval [CI]: 2.47-427.15; p=0.008) was an independent predictor for SDAVF. The diagnostic model constructed using the PFV and CED signs had better diagnostic performance, with an area under the curve of 0.957 (p<0.001), maximum Youden index of 0.844, sensitivity of 92.9%, and specificity of 91.5%. Both 3D-T2-SPACE (77.8%) and CE-MRA (83.3%) sequences had good localisation values for SDAVF. Combining the two imaging examinations had better diagnostic accuracy than that of DSA.

CONCLUSION

CED and PFV on conventional MRI were specific indicators for the diagnosis of SDAVF. To compensate for the lack of fistula localisation on conventional MRI, 3D-T2-SPACE and CE-MRA can be used. Together they complement each other and have good diagnostic potential.

The value of 3D T2-weighted SPACE sequence in the differential diagnosis of spinal arteriovenous fistula and acute transverse myelitis

OBJECTIVE

Spinal arteriovenous fistulas (SAVF) was often neglected and misdiagnosed as acute transverse myelitis (ATM) due to its insidious onset and non-specific clinical symptoms. This study aims to investigate the differential diagnostic value of high-resolution T2-weighted volumetric sequence (3D sampling perfection with application-optimized contrasts using different flip-angle evolutions [SPACE]) in patients with SAVF and ATM.

METHODS

Retrospectively analyzed the clinical and radiological findings of 32 SDAVF patients and 32 ATM patients treated at our institutions from May 2018 to January 2023. They all underwent conventional spinal MRI and T2-SPACE examination, compared their performance in identifying lesions, to estimate the value of T2 SPACE sequence in the diagnosis of SAVF and ATM patients.

RESULTS

The clue of cauda equina area change (CEAC) in conventional MRI and T2-SPACE sequences is specific for the diagnosis of SAVF. The diagnostic model composed of perimedullary flow voids (PFV) and CEAC has good diagnostic performance (AUCMRI = 0.95; AUCSPACE = 0.935). Compared with conventional MRI, the T2-SPACE sequence has a higher detection rate, sensitivity, and negative predictive value for PFV and CEAC in SAVF patients, but lower specificity and positive predictive value. In T2-SPACE images, there are significant differences in the distribution range, quadrant, and maximum diameter of PFV vessels between SAVF and ATM patients. Moreover, T2-SPACE sequence can determine the site of fistula in most SAVF patients preferably, and the inter-rater agreement was good in the assessment of the fistula.

CONCLUSION

The CEAC is a new and useful clue for the diagnosis of thoracolumbar SAVF. And T2-SPACE sequence can more intuitively observe the lesions of SAVF, has good differential diagnostic value for SAVF and ATM patients.

Targeted embolisation for coexisting conus medullaris arteriovenous malformation and cauda equina arteriovenous fistulas with a varix on a shared drainer†

BACKGROUND

The coexistence of vascular malformations in the conus medullaris and cauda equina has been rarely reported, and the complex angioarchitecture in multiple arteriovenous lesions remains poorly understood.

CASE DESCRIPTION

A 17-year-old woman presented with a sudden-onset, stepwise worsening of weakness and pain in the bilateral legs. Angiography revealed conus medullaris arteriovenous malformation and cauda equina arteriovenous fistulas. One of the drainers was shared between the coexisting lesions and harboured a varix. Targeted embolisation of a fistulous point in the conus lesion was performed with precaution to prevent occluding the common drainage route, which led to symptom improvement with angiographical diminishment of the varix.

CONCLUSIONS

Recognising that communications between drainers can be observed in multiple spinal arteriovenous lesions is important in facilitating a safe embolisation. Cautious assessment of angiogram with fusion images of cone-beam computed tomography and volumetric T2 magnetic resonance imaging can help in establishing the diagnosis and treatment strategy.

Anatomical considerations regarding a high-flow arteriovenous fistula below the conus medullaris in a patient with hereditary hemorrhagic telangiectasia: Case report

BACKGROUND AND IMPORTANCE

Cauda equina radicular arteriovenous fistulas are rare "low flow" shunting lesions characterized by direct communication between the radicular artery and vein of a cauda equina nerve root. None have been associated with hereditary hemorrhagic telangiectasia and a high-flow cauda equina radicular arteriovenous fistula has never been reported. We present a unique case of a high-flow cauda equina radicular arteriovenous fistula in a patient with hereditary hemorrhagic telangiectasia. Marked flow-induced vascular remodeling posed significant diagnostic and therapeutic challenges which will be highlighted in this report.

CLINICAL PRESENTATION

A 39-year-old female with genetically confirmed hereditary hemorrhagic telangiectasia presented with progressive thoracic myelopathy secondary to a high-flow single-hole arteriovenous fistula below the conus. The feeding artery, arising from the anterior spinal artery, and draining vein had a paramedian course, favoring the diagnosis of a cauda equina radicular arteriovenous fistula (supplied by a proximal radicular artery) over a filum terminale arteriovenous fistula. Transarterial embolization was attempted but significant elongation and tortuosity of the anterior spinal artery precluded microcatheter access to the fistulous point. Surgical disconnection was successfully performed. The intraoperative findings supported the diagnosis of cauda equina radicular arteriovenous fistula. Delayed neurologic deterioration secondary to overshooting venous thrombosis was observed. She recovered after the initiation of therapeutic anticoagulation.

CONCLUSION

To the best of our knowledge, we hereby report the first high-flow cauda equina radicular arteriovenous fistula. The accurate differentiation of cauda equina radicular arteriovenous fistula from filum terminale arteriovenous fistulas, while challenging, is important to avoid treatment-related complications. Careful preoperative planning, the use of specialized endovascular and surgical techniques, and meticulous postoperative care can ensure the safe and complete disconnection of high-flow cauda equina radicular arteriovenous fistulas.

Functional Vascular Anatomy and Arteriovenous Shunts of the Spine

The history of vascular anatomy of the spinal cord and spine began in the late 19th century. With recent advances in endovascular and surgical treatment of vascular lesions of the spinal cord, understanding the vascular anatomy of the spinal cord has become more important than ever. Catheter angiography is the gold standard for diagnosing vascular lesions of the spinal cord, and the vascular architecture of the spinal cord itself is relatively simple, a repetition of basic longitudinal and axial structures. This review discusses the vascular anatomy of the spine and spinal cord from the embryological point of view, as well as an overview of typical spinal arteriovenous shunt diseases mainly depending on their locations: paraspinal, epidural, dural, perimedullary, intramedullary, filum terminale/cauda equina, craniocervical junction, and related diseases.

Sacral dural arteriovenous fistula of the filum terminale coexisting with partially thrombosed filum vein: A case report and literature review

Background:

Filum terminale arteriovenous fistulas (FTAVFs) are rare and usually classified as intradural ventral AVFs or Type IVa perimedullary fistulas, located on the pia surface along the course of filum terminale internum (FTI). We report an extremely rare case of sacral dural arteriovenous fistula of the FT. We also review the occurrence of FTAVFs in the sacral region.

Case Description:

A 64-year-old man presented with progressive weakness of the lower extremities for 3 months and bowel/bladder dysfunction following long history of back pain radiating to both legs. Magnetic resonance imaging of the lumbosacral and thoracic spine showed spinal cord congestion, extending from the conus medullaris to the level of T3, and partial thrombosis within the abnormal tortuous and dilated flow void, running from the sacral area to conus medullaris. Further findings were compression fracture of L2 vertebra, Grade I degenerative spondylolisthesis at the level of L2-3, and L3-4, and spinal stenosis at L2-3, L3-4, and L4-5. Spinal angiography, maximum intensity projection reformatted image of angiographic computerized tomography, and three-dimensional reconstructed image clearly demonstrated dural AVF of the FT at the level of S2 supplied by bilateral lateral sacral and middle sacral arteries with cranial drainage to perimedullary vein through the enlarged vein of the filum. The patient was indirectly treated by transection of the filum terminale and the draining vein at the level of L5 rostral to the fistula.

Conclusion:

Sacral DAVFs of the FT are extremely rare. In our case, the formation of fistula may cause by venous hypertension secondary to partial thrombosis within the filum vein, probably resulting from long-standing spinal canal stenosis. Sacral FTAVFs may be found on the pia surface of the terminal FTI, dural component at the area of dural sac termination, or dural extension covering the filum terminale externum.

Intradural lumbar radicular arteriovenous malformation mimicking perimedullary arteriovenous malformation of the conus medullaris: illustrative case

BACKGROUND

Intradural radicular arteriovenous malformation (AVM) of the cauda equina is a rare entity of spinal AVMs. Because of the specific arterial supply of the conus medullaris and cauda equina, AVMs in this area sometimes present with confusing radiological features.

OBSERVATIONS

The authors reported a rare case of intradural radicular AVM arising from the lumbar posterior root. The patient presented with urinary symptoms with multiple flow void around the conus medullaris, as shown on magnetic resonance imaging. Digital subtraction angiography demonstrated arteriovenous shunt at the left side of the conus medullaris fed by the anterior spinal artery via anastomotic channel to the posterior spinal artery and rich perimedullary drainers. There was another arteriovenous shunt at the L3 level from the left L4 radicular artery. Preoperative diagnosis was perimedullary AVM with radicular arteriovenous fistula. Direct surgery with indocyanine green angiography revealed that the actual arteriovenous shunt was located at the left L4 posterior root. The AVM was successfully treated by coagulation of feeding branches.

LESSONS

Unilateral arteriovenous shunt fed by either posterior or anterior spinal artery at the conus medullaris may include AVM of the cauda equina despite abundant perimedullary venous drainage. Careful pre- and intraoperative diagnostic imaging is necessary for appropriate treatment.

Cauda equina arteriovenous fistula supplied by proximal radicular artery and concomitant sacral dural arteriovenous fistula: A case report and literature review

Background

Cauda equina arteriovenous fistulas (AVFs) fed by the proximal radicular artery are exceedingly rare. Spinal dural arteriovenous fistulas (DAVFs) in the sacral region are rare and usually misdiagnosed. We report a case of a cauda equina AVF with concomitant sacral DAVF. We also review the coexistence of multiple types of spinal vascular malformations in a single patient.

Case Description

A 54-year-old man presented with progressive weakness of the lower extremities for 1 month. Magnetic resonance imaging (MRI) of the lumbosacral and thoracic spine showed spinal cord congestion, extending from the conus medullaris to the level of T7, and abnormal tortuous and dilated flow void, running from the level of L5 to T12 along anterior surface of the spinal cord. Spinal angiography demonstrated the fistula at the level of L2 below the conus medullaris. Based on intraoperative findings, the cauda equina AVF supplied by the proximal radicular artery with cranial drainage through the enlarged radicular vein was confirmed and successfully obliterated. Another enlarged arterialized radicular vein running parallel to another cauda equina nerve root is observed with unknown origin. After the operation, the patient showed mild improvement of his symptoms. Follow-up MRI and contrast-enhanced MR angiography revealed an another sacral DAVF vascularized by the lateral sacral artery.

Conclusion

The coexistence of different spinal vascular malformations in a same patient is extremely rare. Most authors of several studies hypothesized that venous hypertension and thrombosis due to the presence or treatment of the first spinal vascular lesion may produce a second DAVF.

Filum Terminale Arteriovenous Fistula with Additional Arterial Supply by the Posterior Spinal Artery: A Report of Two Cases

Filum terminale arteriovenous fistulas (FTAVFs) are rare and usually supplied by the artery of the filum terminale, distal termination of the anterior spinal artery (ASA). These fistulas may also supply from the lateral sacral artery (LSA) arising from the internal iliac artery and/or middle sacral artery. Additional supply by the posterior spinal artery (PSA) has never been mentioned before. The authors describe two middle-aged men harboring FTAVFs manifested with progressive myelopathy and bowel/bladder dysfunction. The first fistula was supplied by the ASA with additional supply by the dilated PSA connecting with the ASA. Another fistula was supplied by the LSA and the PSA communicating with the ASA. The first case was successfully treated by endovascular treatment with N-butyl cyanoacrylate through the enlarged PSA, whereas the second case was surgically treated by direct obliteration of the fistula. Both patients had good neurological outcome.

Surgical resection of arteriovenous fistula at the cauda equina

INTRODUCTION

Although spinal arteriovenous fistula (AVF) has been reported widely, AVF at the cauda equina is quite rare. We described a case of AVF at the cauda equina that was fed by the distal radicular artery (DRA).

CASE PRESENTATION

A 50-year-old woman presented with sudden weakness of the lower extremities. Magnetic resonance imaging (MRI) revealed a lesion with a highly intense signal at the conus medullaris, which was surrounded by several low-intensity signals (flow voids). Digital subtraction angiography revealed AVF at the cauda equina and that it was fed by the DRA, which was directly fed by the L3 segmental artery. We performed surgical resection of the AVF while monitoring motor-evoked potentials. The patient's postoperative course was uneventful, and her neurological symptoms gradually resolved. MRI 2 years after surgery showed the disappearance of both intramedullary edema and the flow voids.

DISCUSSION

For the AVF, located at the cauda equina and fed by the DRA in this case, surgical resection or endovascular embolization could have been selected. We performed open surgery to achieve complete obliteration of the AVF, which led to postoperative functional recovery without any adverse events. However, only a limited number of AVFs at the level of the cauda equina have been reported, and treatment standards have not been established. Further studies of AVFs at the cauda equina are necessary to clarify the epidemiological characteristics and clinical outcomes with an appropriate sample size.

Spinal arteriovenous fistula located in the filum terminale externa: A case report and review of the literature

A filum terminale arteriovenous fistula (FTAVF) is an extremely rare spinal arteriovenous fistula (AVF) and typically presents with myelopathy and conus medullaris syndrome caused by venous congestion in the spinal cord. Most reported FTAVFs are intradural pial AVFs with perimedullary drainage in the filum terminale interna. However, there are no reports of AVFs in the filum terminale externa (FTE). We describe a case involving a 68-year-old man with an AVF in the FTE who presented with progressive myelopathy and underwent successful endovascular treatment. We identified the specific shunt point by fusing postoperative computed tomography and magnetic resonance images. The features of the extradural sac AVF developed in the FTE may mimic those of a dural AVF with dural supply to the FTE covered by the dural component, unlike typical FTAVFs where the shunt develops at the pia mater. This case makes a significant contribution to the field by increasing the understanding of the clinical characteristics of an AVF that develops in the FTE and its angioarchitecture.

Acquired Lumbosacral Spinal Dural Arteriovenous Fistula in Association with Degenerative Lumbosacral Disc Herniation and Spinal Canal Stenosis: Report of Two Cases and Review of the Literature

The authors describe two cases harboring lumbosacral spinal dural arteriovenous fistulas (SDAVFs) manifested with nonspecific initial symptoms, leading to misdiagnosis and unnecessary procedures. A curvilinear flow void in the lumbar region and thoracic cord congestion with subtle perimedullary flow voids were detected on magnetic resonance imaging (MRI) in both patients. Contrast-enhanced magnetic resonance angiography and spinal angiography confirmed the SDAVFs in the lower lumbar and sacral region. Both fistulas were located at the same level of disc herniation and spinal canal stenosis and supplied by branches of the internal iliac arteries (i.e., iliolumbar and lateral sacral arteries) with cranial drainage from the dilated vein of the filum terminale, corresponding to a curvilinear flow void, to the perimedullary veins. The first case was successfully treated with embolization. Another case had recanalization of the fistula 4 months after endovascular treatment and was successfully treated with surgical interruption of the fistula. Our two case reports may provide additional evidence supporting an acquired etiology of SDAVFs, probably secondary to lumbosacral disc herniation and spinal canal stenosis. The authors also reviewed literature about preexistent lumbosacral SDAVFs associated with disc herniation and spinal canal stenosis. From our review, the level of SDAVFs in most patients is correlated with the level of disc herniation, spondylolisthesis, and/or spinal stenosis.

Cauda Equina Occupation Ratio as a New Imaging Parameter for the Evaluation of Spinal Dural Arteriovenous Fistulae

BACKGROUND

Because spinal dural arteriovenous fistulae (SDAVF) are rare and their clinical presentation is nonspecific, they are often overlooked during diagnostic evaluations. Typical magnetic resonance imaging (MRI) findings are intramedullary T2-weighted signal hyperintensity and perimedullary flow voids. There are few reports on the characteristic signs of the cauda equina. We assessed the significance of a new imaging parameter, the cauda equina occupation ratio (CEOR), for the evaluation of SDAVF.

METHODS

We retrospectively analyzed the clinical charts and radiological findings of 20 SDAVF patients treated at our institutions. We evaluated sagittal T2-weighted MRI scans and assessed the CEOR, the occupation ratio of the cauda equina compared to the sagittal diameter of the corresponding lumbar spinal canal. The controls were 21 age- and sex-matched subjects.

RESULTS

Of the 20 SDAVF, 10 were at the thoracic and 10 at the lumbar spine. There was no significant difference between the preoperative CEOR and the spinal level of the fistulae or the neurological signs. On preoperative MRI scans, the mean CEOR was 56.0 ± 7.8; postoperatively, it was 37.1 ± 7.4 (P = 0.000). The preoperative CEOR was significantly larger in SDAVF patients than in the controls (P = 0.000); postoperatively, it was smaller than in the controls (P = 0.14).

CONCLUSIONS

The preoperative CEOR was larger in patients with SDAVF than in the controls. It normalized after successful occlusion of the fistula. Our findings indicate that the CEOR is a useful parameter for the pre- and postoperative evaluation of SDAVF.

Dilated Vein of the Filum Terminale on MRI: A Marker for Deep Lumbar and Sacral Dural and Epidural Arteriovenous Fistulas

BACKGROUND AND PURPOSE

Conventional MR imaging can provide important clues regarding the location of a spinal vascular malformation. We hypothesized that a dilated vein of the filum terminale, identified as a curvilinear flow void on T2WI, could be an imaging marker for a lower lumbar (L3-L5) or sacral fistula.

MATERIALS AND METHODS

We retrospectively identified all spinal dural and spinal epidural arteriovenous fistulas from 2 large tertiary referral centers from 2005 to 2018. All patients had a lumbar spinal MR imaging and a conventional spinal angiography. Images were reviewed by 2 neuroradiologists who categorized the level of the arterial feeder to the fistula and the presence or absence of a dilated vein of the filum terminale on T2WI and T1 postcontrast images. We calculated the sensitivity, specificity, positive predictive value, and negative predictive value of the presence of a dilated filum terminale vein for a deep lumbar or sacral fistula.

RESULTS

One hundred sixty-two patients were included. An enlarged filum terminale vein was identified in 39 patients. Sensitivity, specificity, positive predictive value, and negative predictive value of the presence of a dilated filum terminale vein for a deep lumbar or sacral fistula were 86%, 98.3%, 94.9%, and 95.1%, respectively.

CONCLUSIONS

The presence of a dilated vein of the filum terminale can accurately localize a spinal dural arteriovenous fistula/spinal epidural arteriovenous fistula to the lower lumbar or sacral spine in patients being evaluated for such lesions. This finding can be used to facilitate both noninvasive and conventional spinal angiography.

Vascular configurations of anastomotic basket of conus medullaris in human spinal cord

The arterial basket of the conus medullaris is one of several anastomoses between the anterior and posterior spinal arteries. The anatomy of this structure has attracted little attention. This work sought to investigate its configuration in human spinal cords. Spinal cords from male and female cadavers (n = 32) were injected with colored latex through the intercostal, lumbar, medial sacral and the posterior trunks of the hypogastric arteries. After injection, specimens preserving the dural sac were obtained and fixed in formaldehyde solution. Finally, the spinal arteries were microdissected. In 18.75% of the specimens, the anterior spinal artery divided symmetrically and formed anastomoses with the posterior spinal arteries. In 81.25%, the branching pattern observed was asymmetrical. In 21.87% there were differences in the diameter of the anastomotic arteries, and 40.63% originated at different levels along the craniocaudal axis. Interestingly, 12.5% of the specimens presented an intraparenchymatous anastomosis that has not been described previously. True unilateral anastomosis was only observed in 6.25% of the spinal cords. The most frequent configuration of the anastomotic basket of the conus medullaris is a bilateral asymmetric anastomosis. The asymmetry of the branches could be caused by differences in their diameters or in their origins along the craniocaudal axis. Symmetrical patterns are less frequent, and unilateral anastomoses are rare. In reality, some cases of apparently unilateral anastomosis present an intramedullary course of the anastomotic artery. Clin. Anat. 31:441-448, 2018. © 2017 Wiley Periodicals, Inc.

A case of arteriovenous fistula of the cauda equina fed by the proximal radicular artery: anatomical features and treatment precautions

PURPOSE

Arteriovenous fistula (AVF) of the cauda equina (CE) fed by the proximal radicular artery (PRA) is very rare, and the differentiation from that of the filum terminale (FT) is important to avoid treatment-related injury to the CE when endovascular treatment is selected. The authors describe a case of AVF of the CE fed by the PRA, demonstrate the anatomical features and discuss the treatment precautions.

METHODS

A 69-year-old man presented with a transient weakness of lower limbs. Spinal angiography and magnetic resonance (MR) imaging revealed AVF, of which the feeding artery arose from the anterior spinal artery (ASA), forming the fistula at L2 level to be drained into the longitudinal venous trunk. Under a tentative diagnosis of AVF of the FT, endovascular treatment was attempted but failed due to impossible catheterization into the ASA. Therefore, surgery was performed.

RESULTS

Intraoperative finding revealed that the feeding artery and draining vein were not on the FT but on the CE, resulting in the proper diagnosis of AVF of the CE. Surgical clips were applied to the draining vein closest to the fistula, and postoperatively the symptom improved gradually. Although we thoroughly reevaluated spinal angiography and MR images postoperatively, AVF of the CE fed by the PRA and that of the FT were not distinguishable.

CONCLUSIONS

The authors described a case of AVF of the CE fed by the PRA and demonstrated the difficulty of the differentiation from that of the FT. The utmost precautions are necessary when endovascular treatment is selected.

Three-dimensional micro-computed tomography analysis for spinal instability after lumbar facetectomy in the rat

PURPOSE

Intervertebral disc degeneration is thought to contribute to low back pain. However, the pathophysiological mechanisms remain controversial. In a previous study, we developed an animal model that showed delayed gait disturbance after lumbar facetectomy in the rat. We believe that this gait disturbance was caused by low back pain, although the mechanisms of this gait abnormality remain unknown. The purpose of this study was to evaluate structural changes of the lumbar spine after facetectomy in the rat utilizing three-dimensional micro-computed tomography (3DμCT) compared to histology.

METHODS

Thirty male SD rats were divided into three groups. In the Sham group (n = 13), only exposure of bilateral facet joints at the L4-5 level was performed. In the Experimental group (n = 13), complete resection of bilateral L4-5 facet joints was achieved. Naïve rats (n = 4) were used for controls. At 7-week postoperative, 3DµCT and histological analyses were performed.

RESULTS

On 3DµCT images, increased disc height and endplate irregularities at the L4-5 segment and decreased disc height at adjacent segments were observed in the Experimental group. Histological scores were also higher in the Experimental group than the Sham Group.

CONCLUSIONS

Degenerative changes were observed at the facetectomy level. These may correspond with the previously reported delayed gait disturbance after facetectomy. This animal model may be useful to create mechanically induced disc degeneration without direct tissue damage to the disc.