Advanced Imaging of the Peripheral Nerves, From the AJR "How We Do It" Special Series.

Advanced imaging of peripheral nerves is occupying an increasingly important role in the diagnostic workup of peripheral nerve disorders. Advances in MR neurography (MRN) and high-resolution ultrasound have addressed historical challenges in peripheral nerve imaging related to nerves' small size and non-linear course, and difficult differentiation from surrounding tissues. Modern MRN depicts neuromuscular anatomy with exquisite contrast resolution, and MRN has become the workhorse imaging modality for peripheral nerve evaluation. MRN protocols vary across institutions and are adjusted in individual patients, although commonly include nerve-selective sequences and diffusion tensor imaging tractography. Ultrasound offers a dynamic, real-time high-resolution assessment of peripheral nerves, and is widely accessible and less costly than MRN. Ultrasound has greater ability to interrogate peripheral nerves at the fascicular level and provides complementary information to MRN. However, ultrasound of peripheral nerves requires substantial skill and experience and is operator-dependent. The two modalities have distinct advantages and disadvantages, and the selection between these depends on the clinical context. This article provides an overview of advanced imaging techniques used for evaluation of peripheral nerves, with attention to MRN and high-resolution ultrasound. We draw on our institutional experience in performing both modalities to highlight technical considerations for optimizing examinations.

Practical Applications of Artificial Intelligence in Spine Imaging: A Review.

Artificial intelligence (AI), a transformative technology with unprecedented potential in medical imaging, can be applied to various spinal pathologies. AI-based approaches may improve imaging efficiency, diagnostic accuracy, and interpretation, which is essential for positive patient outcomes. This review explores AI algorithms, techniques, and applications in spine imaging, highlighting diagnostic impact and challenges with future directions for integrating AI into spine imaging workflow.

Comparison of Lumbosacral Fusion Grade in Patients after Transforaminal and Anterior Lumbar Interbody Fusion with Minimum 2-Year Follow-Up.

OBJECTIVE: Generally, anterior lumbar interbody fusion (ALIF) was believed superior to transforaminal lumbar interbody fusion (TLIF) in induction of fusion. However, many studies have reported comparable results in lumbosacral fusion rate between the two approaches. This study aimed to evaluate the realistic lumbosacral arthrodesis rates following ALIF and TLIF in patients with degenerative spondylolisthesis as measured by CT and radiology. METHODS: Ninety-six patients who underwent single-level L5-S1 fusion through ALIF (n = 48) or TLIF (n = 48) for degenerative spondylolisthesis at the Spine Center, University of California San Francisco, between October 2014 and December 2017 were retrospectively evaluated. Fusion was independently evaluated and categorized as solid fusion, indeterminate fusion, or pseudarthroses by two radiologists using the modified Brantigan-Steffee-Fraser (mBSF) grade. Clinical data on sex, age, body mass index, Meyerding grade, smoking status, follow-up times, complications, and radiological parameters including disc height, disc angle, segmental lordosis, and overall lumbar lordosis were collected. The fusion results and clinical and radiographic data were statistically compared between the ALIF and TLIF groups by using t-test or chi-square test. RESULTS: The mean follow-up period was 37.5 (ranging from 24 to 51) months. Clear, solid radiographic fusions were higher in the ALIF group compared with the TLIF group at the last follow-up (75% vs 47.9%, p = 0.006). Indeterminate fusion occurred in 20.8% (10/48) of ALIF cases and in 43.8% (21/48) of TLIF cases (p = 0.028). Radiographic pseudarthrosis was not significantly different between the TLIF and ALIF groups (16.7% vs 8.3%; p = 0.677). In subgroup analysis of the patients without bone morphogenetic protein (BMP), the solid radiographic fusion rate was significantly higher in the ALIF group than that in the TLIF group (78.6% vs 45.5%; p = 0.037). There were no differences in sex, age, body mass index, Meyerding grade, smoking status, or follow-up time between the two groups (p > 0.05). The ALIF group had more improvement in disc height (7.8 mm vs 4.7 mm), disc angle (5.2° vs 1.5°), segmental lordosis (7.0° vs 2.5°), and overall lumbar lordosis (4.7° vs 0.7°) compared with the TLIF group (p < 0.05). Overall complication rates were similar between the TLIF and ALIF groups (10.4% vs 8.33%; p > 0.999). CONCLUSIONS: With a minimum 2-year radiographic analysis of arthrodesis at lumbosacral level by radiologists, the rate of solid radiographic fusions was higher in the ALIF group compared with the TLIF group, whereas the TLIF group had a higher rate of indeterminate fusion. Radiographic pseudarthrosis did not differ significantly between the TLIF and ALIF groups.

Technology and Tool Development for BACPAC: Qualitative and Quantitative Analysis of Accelerated Lumbar Spine MRI with Deep-Learning Based Image Reconstruction at 3T.

OBJECTIVES: To evaluate whether combining fast acquisitions with deep-learning reconstruction can provide diagnostically useful images and quantitative assessment comparable to standard-of-care acquisitions for lumbar spine magnetic resonance imaging (MRI). METHODS: Eighteen patients were imaged with both standard protocol and fast protocol using reduced signal averages, each protocol including sagittal fat-suppressed T2-weighted, sagittal T1-weighted, and axial T2-weighted 2D fast spin-echo sequences. Fast-acquisition data was additionally reconstructed using vendor-supplied deep-learning reconstruction with three different noise reduction factors. For qualitative analysis, standard images as well as fast images with and without deep-learning reconstruction were graded by three radiologists on five different categories. For quantitative analysis, convolutional neural networks were applied to sagittal T1-weighted images to segment intervertebral discs and vertebral bodies, and disc heights and vertebral body volumes were derived. RESULTS: Based on noninferiority testing on qualitative scores, fast images without deep-learning reconstruction were inferior to standard images for most categories. However, deep-learning reconstruction improved the average scores, and noninferiority was observed over 24 out of 45 comparisons (all with sagittal T2-weighted images while 4/5 comparisons with sagittal T1-weighted and axial T2-weighted images). Interobserver variability increased with 50 and 75% noise reduction factors. Deep-learning reconstructed fast images with 50% and 75% noise reduction factors had comparable disc heights and vertebral body volumes to standard images (r2≥ 0.86 for disc heights and r2≥ 0.98 for vertebral body volumes). CONCLUSIONS: This study demonstrated that deep-learning-reconstructed fast-acquisition images have the potential to provide noninferior image quality and comparable quantitative assessment to standard clinical images.

Variant Sciatic Nerve Anatomy in Relation to the Piriformis Muscle on Magnetic Resonance Neurography: A Potential Etiology for Extraspinal Sciatica.

OBJECTIVE: To assess the prevalence and clinical implications of variant sciatic nerve anatomy in relation to the piriformis muscle on magnetic resonance neurography (MRN), in patients with lumbosacral neuropathic symptoms. MATERIALS AND METHODS: In this retrospective single-center study, 254 sciatic nerves, from 127 patients with clinical and imaging findings compatible with extra-spinal sciatica on MRN between 2003 and 2013, were evaluated for the presence and type of variant sciatic nerves, split sciatic nerve, abnormal T2-signal hyperintensity, asymmetric piriformis size and increased nerve caliber, and summarized using descriptive statistics. Two-tailed chi-square tests were performed to compare the anatomical variant type and clinical symptoms between imaging and clinical characteristics. RESULTS: Sixty-four variant sciatic nerves were identified with an equal number of right and left variants. Bilateral variants were noted in 15 cases. Abnormal T2-signal hyperintensity was seen significantly more often in variant compared to conventional anatomy (40/64 vs. 82/190; p = 0.01). A sciatic nerve split was seen significantly more often in variant compared to conventional anatomy (56/64 vs. 20/190; p < 0.0001). Increased nerve caliber, abnormal T2-signal hyperintensity, and asymmetric piriformis size were significantly associated with the clinically symptomatic side compared to the asymptomatic side (98:2, 98:2, and 97:3, respectively; p < 0.0001 for all). Clinical symptoms were correlated with variant compared to conventional sciatic nerve anatomy (64% vs. 46%; p = 0.01). CONCLUSION: Variant sciatic nerve anatomy, in relation to the piriformis muscle, is frequently identified with MRN and is more likely to be associated with nerve signal changes and symptomatology.

Deep learning for automated, interpretable classification of lumbar spinal stenosis and facet arthropathy from axial MRI.

OBJECTIVES: To evaluate a deep learning model for automated and interpretable classification of central canal stenosis, neural foraminal stenosis, and facet arthropathy from lumbar spine MRI. METHODS: T2-weighted axial MRI studies of the lumbar spine acquired between 2008 and 2019 were retrospectively selected (n = 200) and graded for central canal stenosis, neural foraminal stenosis, and facet arthropathy. Studies were partitioned into patient-level train (n = 150), validation (n = 20), and test (n = 30) splits. V-Net models were first trained to segment the dural sac and the intervertebral disk, and localize facet and foramen using geometric rules. Subsequently, Big Transfer (BiT) models were trained for downstream classification tasks. An interpretable model for central canal stenosis was also trained using a decision tree classifier. Evaluation metrics included linearly weighted Cohen's kappa score for multi-grade classification and area under the receiver operator characteristic curve (AUROC) for binarized classification. RESULTS: Segmentation of the dural sac and intervertebral disk achieved Dice scores of 0.93 and 0.94. Localization of foramen and facet achieved intersection over union of 0.72 and 0.83. Multi-class grading of central canal stenosis achieved a kappa score of 0.54. The interpretable decision tree classifier had a kappa score of 0.80. Pairwise agreement between readers (R1, R2), (R1, R3), and (R2, R3) was 0.86, 0.80, and 0.74. Binary classification of neural foraminal stenosis and facet arthropathy achieved AUROCs of 0.92 and 0.93. CONCLUSION: Deep learning systems can be performant as well as interpretable for automated evaluation of lumbar spine MRI including classification of central canal stenosis, neural foraminal stenosis, and facet arthropathy. KEY POINTS: • Interpretable deep-learning systems can be developed for the evaluation of clinical lumbar spine MRI. Multi-grade classification of central canal stenosis with a kappa of 0.80 was comparable to inter-reader agreement scores (0.74, 0.80, 0.86). Binary classification of neural foraminal stenosis and facet arthropathy achieved favorable and accurate AUROCs of 0.92 and 0.93, respectively. • While existing deep-learning systems are opaque, leading to clinical deployment challenges, the proposed system is accurate as well as interpretable, providing valuable information to a radiologist in clinical practice.

Magnetic Resonance Imaging of the Lumbar Spine: Recommendations for Acquisition and Image Evaluation from the BACPAC Spine Imaging Working Group.

Management of patients suffering from low back pain (LBP) is challenging and requires development of diagnostic techniques to identify specific patient subgroups and phenotypes in order to customize treatment and predict clinical outcome. The Back Pain Consortium (BACPAC) Research Program Spine Imaging Working Group has developed standard operating procedures (SOPs) for spinal imaging protocols to be used in all BACPAC studies. These SOPs include procedures to conduct spinal imaging assessments with guidelines for standardizing the collection, reading/grading (using structured reporting with semi-quantitative evaluation using ordinal rating scales), and storage of images. This article presents the approach to image acquisition and evaluation recommended by the BACPAC Spine Imaging Working Group. While the approach is specific to BACPAC studies, it is general enough to be applied at other centers performing magnetic resonance imaging (MRI) acquisitions in patients with LBP. The herein presented SOPs are meant to improve understanding of pain mechanisms and facilitate patient phenotyping by codifying MRI-based methods that provide standardized, non-invasive assessments of spinal pathologies. Finally, these recommended procedures may facilitate the integration of better harmonized MRI data of the lumbar spine across studies and sites within and outside of BACPAC studies.

Automatic detection and voxel-wise mapping of lumbar spine Modic changes with deep learning.

Background: Modic changes (MCs) are the most prevalent classification system for describing magnetic resonance imaging (MRI) signal intensity changes in the vertebrae. However, there is a growing need for novel quantitative and standardized methods of characterizing these anomalies, particularly for lesions of transitional or mixed nature, due to the lack of conclusive evidence of their associations with low back pain. This retrospective imaging study aims to develop an interpretable deep learning-based detection tool for voxel-wise mapping of MCs. Methods: Seventy-five lumbar spine MRI exams that presented with acute-to-chronic low back pain, radiculopathy, and other symptoms of the lumbar spine were enrolled. The pipeline consists of two deep convolutional neural networks to generate an interpretable voxel-wise Modic map. First, an autoencoder was trained to segment vertebral bodies from T1-weighted sagittal lumbar spine images. Next, two radiologists segmented and labeled MCs from a combined T1- and T2-weighted assessment to serve as ground truth for training a second autoencoder that performs segmentation of MCs. The voxels in the detected regions were then categorized to the appropriate Modic type using a rule-based signal intensity algorithm. Post hoc, three radiologists independently graded a second dataset with the aid of the model predictions in an artificial (AI)-assisted experiment. Results: The model successfully identified the presence of changes in 85.7% of samples in the unseen test set with a sensitivity of 0.71 (±0.072), specificity of 0.95 (±0.022), and Cohen's kappa score of 0.63. In the AI-assisted experiment, the agreement between the junior radiologist and the senior neuroradiologist significantly improved from Cohen's kappa score of 0.52 to 0.58 (p < 0.05). Conclusions: This deep learning-based approach demonstrates substantial agreement with radiologists and may serve as a tool to improve inter-rater reliability in the assessment of MCs.

Cerebrospinal Fluid-Venous Fistulas: A Systematic Review and Examination of Individual Patient Data.

BACKGROUND: Spontaneous intracranial hypotension (SIH) is usually caused by a spinal cerebrospinal fluid (CSF) leak. CSF-venous fistula is an underdiagnosed cause of spinal CSF leak, as it is challenging to identify on myelography. OBJECTIVE: To review existing literature to summarize common presentations, diagnostic imaging modalities, and current treatment strategies for CSF-venous fistulas. METHODS: We conducted a systematic review using PubMed, Embase, Scopus, and Web of Science databases to identify studies discussing CSF-venous fistulas. Titles and abstracts were screened. Studies meeting prespecified inclusion criteria were reviewed in full. RESULTS: Of 180 articles identified, 16 articles met inclusion criteria. Individual patient data was acquired from 7 studies reporting on 18 patients. CSF-venous fistula most frequently presented as positional headache. Digital subtraction myelography provided greatest detection of CSF-venous fistula in the lateral decubitus position and detected CSF-venous fistula in all individual patient cases. Dynamic computed tomography (CT) myelogram enabled detection and differentiation of CSF-venous fistulas from low-flow epidural leaks. The majority of fistulas were in the thoracic spine and slightly more common on the right. Epidural blood patch (EBP) provided temporary or no relief in all individual patients. Resolution or improvement of clinical symptoms and radiologic normalization were observed in all surgically treated patients. CONCLUSION: Although rare, CSF-venous fistula is an important cause of spinal CSF leak contributing to SIH. Dynamic CT myelogram and digital subtraction myelography, particularly in the lateral decubitus position, are the most accurate and effective diagnostic imaging modalities. EBPs often provide only transient relief, while surgical management is preferred.

Diagnostic Challenges in Primary Sacral Tumors and the Yield of Computed Tomography-Guided Needle Biopsy in the Modern Era.

OBJECTIVE: Primary sacral tumors pose unique challenges because of their complex radiographic appearances, diverse pathologic entities, and dramatically different treatment paradigms based on tumor type. Magnetic resonance imaging and computed tomography (CT) can provide valuable information; however, sacral lesions can possess unique radiographic features and pose diagnostic dilemmas. CT-guided percutaneous needle biopsy is a critical component of the diagnostic workup. However, limited data are available on its efficacy for primary sacral tumors. METHODS: The data from patients with newly diagnosed primary sacral lesions during a 12-year period at our hospital were analyzed. The preoperative magnetic resonance imaging findings, biopsy results, and pathological data for patients who required surgery were analyzed. Unique cases in which the final pathologic result was unexpected from the preoperative imaging findings have been highlighted. RESULTS: Of 38 patients who underwent percutaneous needle biopsy, diagnostic tissue was obtained on the first attempt for 31 (82%). Five of the remaining 7 obtained diagnostic tissue on the second attempt, yielding 95% diagnosis, with only two requiring open biopsies. In 2 patients with diagnostic tissue on CT-guided biopsy, an open biopsy was still recommended because of the clinical scenario. In both patients, the open biopsy results matched those of the CT-guided biopsy. For the 18 patients who required surgery, we found 100% correlation between the percutaneous needle biopsy findings and the final pathological diagnosis. No biopsy-induced complications or extraspinal tumor seeding occurred. CONCLUSIONS: CT-guided biopsy is a safe and effective technique. It represents a critical component of the diagnostic algorithm, given the diverse pathological findings of primary sacral lesions and dramatic differences in treatment.

Diagnostic Performance of CT-Guided Bone Biopsies in Patients with Suspected Osteomyelitis of the Appendicular and Axial Skeleton with a Focus on Clinical and Technical Factors Associated with Positive Microbiology Culture Results.

PURPOSE: To assess diagnostic performance of CT-guided percutaneous needle bone biopsy (CTNBB) in patients with suspected osteomyelitis and analyze whether certain clinical or technical factors were associated with positive microbiology results. MATERIALS AND METHODS: All CTNBBs performed in a single center for suspected osteomyelitis of the appendicular and axial skeleton during 2003-2018 were retrospectively reviewed. Specific inclusion criteria were clinical and radiologic suspicion of osteomyelitis. Standard of reference was defined using outcome of surgical histopathology and microbiology culture and clinical and imaging follow-up. Technical and clinical data (needle size, comorbidities, clinical factors, laboratory values, blood cultures) were collected. Logistic regression was performed to assess associations between technical and clinical data and microbiology biopsy outcome. RESULTS: A total of 142 CTNBBs were included (46.5% female patients; age ± SD 46.10 y ± 22.8), 72 (50.7%) from the appendicular skeleton and 70 (49.3%) from the axial skeleton. CTNBB showed a sensitivity of 42.5% (95% confidence interval [CI], 32.0%-53.6%) in isolating the causative pathogen. A higher rate of positive microbiology results was found in patients with intravenous drug use (odds ratio [OR] = 5.15; 95% CI, 1.2-21.0; P = .022) and elevated white blood cell count ≥ 10 × 109/L (OR = 3.9; 95% CI, 1.62-9.53; P = .002). Fever (≥ 38°C) was another clinical factor associated with positive microbiology results (OR = 3.6; 95% CI, 1.3-9.6; P = .011). CONCLUSIONS: CTNBB had a low sensitivity of 42.5% for isolating the causative pathogen. Rate of positive microbiology samples was significantly higher in patients with IV drug use, elevated white blood cell count, and fever.

Schwannomatosis of the Spinal Accessory Nerve: A Case Report.

Schwannomatosis is a distinct syndrome characterized by multiple peripheral nerve schwannomas that can be sporadic or familial in nature. Cases affecting the lower cranial nerves are infrequent. Here, the authors present a rare case of schwannomatosis affecting the left spinal accessory nerve. Upon genetic screening, an in-frame insertion at codon p.R177 of the Sox 10 gene was observed. There were no identifiable alterations in NF1, NF2, LZTR1, and SMARCB1. This case demonstrates a rare clinical presentation of schwannomatosis in addition to a genetic aberration that has not been previously reported in this disease context.

Clinical Utility of Diffusion-Weighted Imaging in Spinal Infections.

PURPOSE: Both laboratory markers and radiographic findings in the setting of spinal infections can be nonspecific in determining the presence or absence of active infection, and can lag behind both clinical symptoms and antibiotic response. Magnetic resonance imaging (MRI) with diffusion-weighted imaging (DWI) has been shown to be helpful in evaluating brain abscesses but has not been commonly used in evaluating spinal infections. We aimed to correlate findings on DWI of the spine to results of microbiological sampling in patients with suspected spinal infections. METHODS: Patients who underwent MRI with DWI for suspicion of spinal infections and microbiological sampling from 2002 to 2010 were identified and reviewed retrospectively in this institutional review board approved study. In addition to DWI, scans included sagittal and axial T1, fast-spin echo (FSE) T2, and post-gadolinium T1 with fat saturation. Regions of interest were drawn on apparent diffusion coefficient (ADC) maps in the area of suspected infections, and ADC values were correlated with microbiological sampling. RESULTS: Of 38 patients with suspected spinal infections, 29 (76%) had positive microbiological sampling, and 9 (24%) had negative results. The median ADC value was 740â€¯× 10-6 mm2/s for patients with positive microbiological sampling and 1980â€¯× 10-6 mm2/s for patients with negative microbiological sampling (p < 0.001). Using an ADC value of 1250â€¯× 10-6 mm2/s or less as the cut-off value for a positive result for spinal infection, sensitivity was 66%, specificity was 88%, positive predictive value was 95%, negative predictive value was 41% and accuracy was 70%. CONCLUSION: In patients with suspected spine infection, ADC values on DWI are significantly reduced in those patients with positive microbiological sampling compared to patients with negative microbiological sampling. The DWI of the spine correlates well with the presence or absence of spinal infection and may complement conventional magnetic resonance imaging (MRI).

Neurological outcomes and surgical complications in 221 spinal nerve sheath tumors.

OBJECTIVE Among all primary spinal neoplasms, approximately two-thirds are intradural extramedullary lesions; nerve sheath tumors, mainly neurofibromas and schwannomas, comprise approximately half of them. Given the rarity of these lesions, reports of surgical complications are limited. The aim of this study was to identify the rates of new or worsening neurological deficits and surgical complications associated with the resection of spinal nerve sheath tumors and the potential factors related to these outcomes. METHODS Patients were identified through a search of an institutional neuropathology database and a separate review of current procedural terminology (CPT) codes. Age, sex, clinical presentation, presence of neurofibromatosis (NF), tumor type, tumor location, extent of resection characterized as gross total or subtotal, use of intraoperative neuromonitoring, surgical complications, presence of neurological deficit, and clinical follow-up were recorded. RESULTS Two hundred twenty-one tumors in 199 patients with a mean age of 45 years were identified. Fifty-three tumors were neurofibromas; 163, schwannomas; and 5, malignant peripheral nerve sheath tumors (MPNSTs). There were 70 complications in 221 cases, a rate of 32%, which included 34 new or worsening sensory symptoms (15%), 12 new or worsening motor deficits (5%), 10 CSF leaks or pseudomeningoceles (4%), 11 wound infections (5%), 5 cases of spinal deformity (2%), and 6 others (2 spinal epidural hematomas, 1 nonoperative cranial subdural hematoma, 1 deep venous thrombosis, 1 case of urinary retention, and 1 recurrent laryngeal nerve injury). Complications were more common in cervical (36%) and lumbosacral (38%) tumors than in thoracic (18%) lesions (p = 0.021). Intradural and dumbbell lesions were associated with higher rates of CSF leakage, pseudomeningocele, and wound infection. Complications were present in 18 neurofibromas (34%), 50 schwannomas (31%), and 2 MPNSTs (40%); the differences in frequency were not significant (p = 0.834). Higher complication rates were observed in patients with NF than in patients without (38% vs 30%, p = 0.189), although rates were higher in NF Type 2 than in Type 1 (64% vs 31%). There was no difference in the use of intraoperative neuromonitoring when comparing cases with surgical complications and those without (67% vs 69%, p = 0.797). However, the use of neuromonitoring was associated with a significantly higher rate of gross-total resection (79% vs 66%, p = 0.022). CONCLUSIONS Resection is a safe and effective treatment for spinal nerve sheath tumors. Approximately 30% of patients developed a postoperative complication, most commonly new or worsening sensory deficits. This rate probably represents an inevitable complication of nerve sheath tumor surgery given the intimacy of these lesions with functional neural elements.

An Imaging-Based Approach to Spinal Cord Infection.

Infections of the spinal cord, nerve roots, and surrounding meninges are uncommon, but highly significant given their potential for severe morbidity and even mortality. Prompt diagnosis can be lifesaving, as many spinal infections are treatable. Advances in imaging technology have now firmly established magnetic resonance imaging (MRI) as the gold standard for spinal cord imaging evaluation, enabling the depiction of infectious myelopathies with exquisite detail and contrast. In this article, we aim to provide an overview of MRI findings for spinal cord infections with special focus on imaging patterns of infection that are primarily confined to the spinal cord, spinal meninges, and spinal nerve roots. In this context, we describe and organize this review around 5 distinct patterns of transverse spinal abnormality that may be detected with MRI as follows: (1) extramedullary, (2) centromedullary, (3) eccentric, (4) frontal horn, and (5) irregular. We seek to classify the most common presentations for a wide variety of infectious agents within this image-based framework while realizing that significant overlap and variation exists, including some infections that remain occult with conventional imaging techniques.

Magnetic resonance neurography in the diagnosis of neuropathies of the lumbosacral plexus: a pictorial review.

Magnetic resonance neurography (MRN) is an important tool to detect abnormalities of peripheral nerves. This pictorial review demonstrates the MRN features of a variety of neuropathies affecting the lumbosacral plexus (LSP) and lower extremity nerves, drawn from over 1200 MRNs from our institution and supplemented by the literature. Abnormalities can be due to spinal compression, extraspinal compression, malignancy, musculoskeletal disease, iatrogenesis, inflammation, infection, and idiopathic disorders. We discuss indications and limitations of MRN in diagnosing LSP neuropathies. As MRN becomes more widely used, physicians must become familiar with the differential diagnosis of abnormalities detectable with MRN of the LSP.

Peripheral nerve imaging.

Disorders of peripheral nerve have been traditionally diagnosed and monitored using clinical and electrodiagnostic approaches. The last two decades have seen rapid development of both magnetic resonance imaging (MRI) and ultrasound imaging of peripheral nerve, such that these imaging modalities are increasingly invaluable to the diagnosis of patients with peripheral nerve disorders. Peripheral nerve imaging provides information which is supplementary to clinical and electrodiagnostic diagnosis. Both MRI and ultrasound have particular benefits in specific clinical circumstances and can be considered as complementary techniques. These technologic developments in peripheral nerve imaging will usher in an era of multimodality assessment of peripheral nerve disorders, with clinical evaluations supported by anatomic information from imaging, and functional information from electrodiagnostic studies. Such a multimodality approach will improve the accuracy and efficiency of patient care.

Large Cervical Vagus Nerve Tumor in a Patient with Neurofibromatosis Type 1 Treated with Gross Total Resection: Case Report and Review of the Literature.

Neurofibromas are benign peripheral nerve sheath tumors that occur commonly in individuals with neurocutaneous disorders such as neurofibromatosis type 1. Vagal nerve neurofibromas, however, are a relatively rare occurrence. We present the case of a 22-year-old man with neurofibromatosis type 1 with a neurofibroma of the left cervical vagal nerve. The mass was resected through an anterior approach without major event. In the postoperative course, the patient developed left vocal cord paralysis treated with medialization with injectable gel. We then present a comprehensive review of the literature for surgical resection of vagal nerve neurofibromas.

Microsurgical Fenestration and Paraspinal Muscle Pedicle Flaps for the Treatment of Symptomatic Sacral Tarlov Cysts.

OBJECTIVE: Sacral Tarlov cysts are rare causes of sciatic and sacrococcygeal pain and neurologic deficits. Although several microsurgical treatments have been described, the optimal treatment has yet to be determined. We describe our initial experience with symptomatic lesions combining 1) cyst fenestration and imbrication and 2) filling the epidural space using vascularized paraspinous muscle flaps rotated into the cystic cavity. METHODS: We retrospectively reviewed all consecutive cases of symptomatic giant sacral Tarlov cysts treated with microsurgery at our institution between 2003 and 2011. The main outcome measure was self-reported symptom relief. Postoperative imaging, surgical complications, and subsequent treatments were also recorded. RESULTS: Thirty-five patients were treated. Mean age was 52 years. All patients presented with a chief complaint of sacral-perineal pain. The mean cyst size was 3.6 cm (largest diameter). Follow-up beyond the initial hospital stay was available in 86% (median 8 months). Ninety-three percent reported improvement in pain at some point during the postoperative course but 50% of those developed recurrent pain symptoms. Postoperative imaging was available in 69% of the patients in whom 92% showed complete obliteration (25%) or reduction in cyst size (67%). CONCLUSIONS: The combination of microsurgical cyst fenestration and the use of vascularized muscle pedicle flaps to fill the cystic cavity and the epidural space results in obliteration or reduction in size of the majority of cysts and is associated with initial improvement in pain in most patients. However, delayed recurrence of pain was common with this technique.