Enhancement in the Round Window Niche: A Potential Pitfall in High-Resolution MR Imaging of the Internal Auditory Canal.

BACKGROUND AND PURPOSE: There is limited discussion in current literature about the normal imaging appearance of the round window. The purpose of this study was to assess the prevalence and imaging characteristics of gadolinium enhancement in the round window niche on MR imaging to the internal auditory canal. MATERIALS AND METHODS: The presence or absence and laterality of enhancement in the round window niche on MR imaging was retrospectively reviewed in 95 patients from 1 institution. All studies included high-resolution (≤0.5-mm section thickness) pre- and postgadolinium 3D FSE T1 with fat-saturation and postgadolinium 3D FLAIR image sequences. T1 and T2 acquisitions were viewed as coregistered overlays to confirm that enhancement was lateral to the round window membrane within the round window niche. CT was reviewed when available to assess the presence and laterality of soft tissue in the round window niche. RESULTS: Ninety-five patients with internal auditory canal MRIs were included. Enhancement was present in the round window of 15 of 95 patients (15.8%). Of the 27 patients who underwent CT, 4 (14.8%) had concordant soft tissue on CT and MR imaging enhancement in the round window niche. One patient had MR imaging enhancement within the round window niche without a corresponding abnormality on CT. The absence of soft tissue on CT and the corresponding lack of MR imaging enhancement were present in 22 (81.5%) patients. CONCLUSIONS: Enhancement can be visualized within the round window niche on MR imaging as an incidental finding. This enhancement probably represents postinflammatory granulation tissue and does not require further intervention. However, the potential for this enhancement to be misdiagnosed as a pathologic process can be a pitfall in MR imaging.

Increased Labyrinthine T1 Postgadolinium Signal Intensity Is Associated with the Degree of Ipsilateral Sensorineural Hearing Loss in Patients with Sporadic Vestibular Schwannoma.

BACKGROUND AND PURPOSE: Vestibular schwannomas are benign, generally slow-growing tumors, commonly presenting with hearing loss. Alterations in the labyrinthine signal are seen in patients with vestibular schwannoma; however, the association between imaging abnormalities and hearing function remains poorly defined. The purpose of this study was to determine whether labyrinthine signal intensity is associated with hearing in patients with sporadic vestibular schwannoma. MATERIALS AND METHODS: This was an institutional review board-approved retrospective review of patients from a prospectively maintained vestibular schwannoma registry imaged in 2003-2017. Signal-intensity ratios of the ipsilateral labyrinth were obtained using T1, T2-FLAIR, and postgadolinium T1 sequences. Signal-intensity ratios were compared with tumor volume and audiometric hearing threshold data including pure tone average, word recognition score, and American Academy of Otolaryngology-Head and Neck Surgery hearing class. RESULTS: One hundred ninety-five patients were analyzed. Ipsilateral labyrinthine signal intensity including postgadolinium T1 images was positively correlated with tumor volume (correlation coefficient = 0.17, P = .02). Among signal-intensity ratios, postgadolinium T1 was significantly positively associated with pure tone average (correlation coefficient = 0.28, P < .001) and negatively associated with the word recognition score (correlation coefficient = -0.21, P = .003). Overall, this result correlated with impaired American Academy of Otolaryngology-Head and Neck Surgery hearing class (P = .04). Multivariable analysis suggested persistent associations independent of tumor volume with pure tone average (correlation coefficient = 0.25, P < .001) and the word recognition score (correlation coefficient = -0.17, P = .02) but not hearing class (P = .14). No consistent significant associations were noted between noncontrast T1 and T2-FLAIR signal intensities and audiometric testing. CONCLUSIONS: Increased ipsilateral labyrinthine postgadolinium signal intensity is associated with hearing loss in patients with vestibular schwannoma.

Normal Enhancement within the Vestibular Aqueduct: An Anatomic Review with High-Resolution MRI.

BACKGROUND AND PURPOSE: The normal appearance of the vestibular aqueduct on postcontrast MR images has not been adequately described in the literature. This study set out to characterize the expected appearance of the vestibular aqueduct, with particular emphasis on the enhancement of the structure on both 3D FSE T1 and 3D-FLAIR sequences. MATERIALS AND METHODS: All MR imaging examinations of the internal auditory canals performed between March 1, 2021, and May 20, 2021, were retrospectively reviewed. All studies included high-resolution (≤0.5-mm section thickness) pre- and postgadolinium 3D FSE T1 with fat-saturated and postgadolinium 3D-FLAIR sequences. Two neuroradiologists independently reviewed the MR images of the vestibular aqueduct for the presence or absence of enhancement on both T1 and FLAIR images and compared the relative intensity of enhancement between sequences. The presence or absence of an enlarged vestibular aqueduct was also noted. RESULTS: Ninety-five patients made up the patient cohort, of whom 5 did not have postcontrast FLAIR images available (50 women [55.6%]). On both sides, enhancement was significantly more commonly seen on postgadolinium FLAIR (76/180, 42.2%) than on T1 fat-saturated images (41/190, 21.6%) (P < .001). The intensity of enhancement was significantly greater on postgadolinium FLAIR images than on T1 fat-saturated images (38.9% versus 3.7%, respectively; P < .001). CONCLUSIONS: Enhancement within the vestibular aqueduct is an expected finding on MR imaging and is both more common and more intense on postgadolinium 3D-FLAIR than on T1 fat-saturated sequences. Such enhancement should not be confused with pathology on MR imaging unless other suspicious findings are present.

A New Frontier in Temporal Bone Imaging: Photon-Counting Detector CT Demonstrates Superior Visualization of Critical Anatomic Structures at Reduced Radiation Dose.

BACKGROUND AND PURPOSE: Photon-counting detector CT is a new technology with a limiting spatial resolution of ≤150 µm. In vivo comparisons between photon-counting detector CT and conventional energy-integrating detector CT are needed to determine the clinical impact of photon counting-detector CT in temporal bone imaging. MATERIALS AND METHODS: Prospectively recruited patients underwent temporal bone CT examinations on an investigational photon-counting detector CT system after clinically indicated temporal bone energy-integrating detector CT. Photon-counting detector CT images were obtained at an average 31% lower dose compared with those obtained on the energy-integrating detector CT scanner. Reconstructed images were evaluated in axial, coronal, and Pöschl planes using the smallest available section thickness on each system (0.4 mm on energy-integrating detector CT; 0.2 mm on photon-counting detector CT). Two blinded neuroradiologists compared images side-by-side and scored them using a 5-point Likert scale. A post hoc reassignment of readers' scores was performed so that the scores reflected photon-counting detector CT performance relative to energy-integrating detector CT. RESULTS: Thirteen patients were enrolled, resulting in 26 image sets (left and right sides). The average patient age was 63.6 [SD, 13.4] years; 7 were women. Images from the photon-counting detector CT scanner were significantly preferred by the readers in all reconstructed planes (P < .001). Photon-counting detector CT was rated superior for the evaluation of all individual anatomic structures, with the oval window (4.79) and incudostapedial joint (4.75) receiving the highest scores on a Likert scale of 1-5. CONCLUSIONS: Temporal bone CT images obtained on a photon-counting detector CT scanner were rated as having superior spatial resolution and better critical structure visualization than those obtained on a conventional energy-integrating detector scanner, even with a substantial dose reduction.

Non-EPI versus Multishot EPI DWI in Cholesteatoma Detection: Correlation with Operative Findings.

BACKGROUND AND PURPOSE: Although multishot EPI (readout-segmented EPI) has been touted as a robust DWI sequence for cholesteatoma evaluation, its efficacy in disease detection compared with a non-EPI (eg, HASTE) technique is unknown. This study sought to compare the accuracy of readout-segmented EPI with that of HASTE DWI in cholesteatoma detection. MATERIALS AND METHODS: A retrospective review was completed of consecutive patients who underwent MR imaging for the evaluation of suspected primary or recurrent/residual cholesteatomas. Included patients had MR imaging examinations that included both HASTE and readout-segmented EPI sequences and confirmed cholesteatomas on a subsequent operation. Two neuroradiologist reviewers assessed all images, with discrepancies resolved by consensus. The ratio of signal intensity between the cerebellum and any observed lesion was noted. RESULTS: Of 23 included patients, 12 (52.2%) were women (average age, 47.8 [SD, 25.2] years). All patients had surgically confirmed cholesteatomas: Six (26.1%) were primary and 17 (73.9%) were recidivistic. HASTE images correctly identified cholesteatomas in 100.0% of patients. On readout-segmented EPI sequences, 16 (69.6%) were positive, 5 (21.7%) were equivocal, and 2 (8.7%) were falsely negative. Excellent interobserver agreement was noted between reviews on both HASTE (κ = 1.0) and readout-segmented EPI (κ = 0.9) sequences. The average signal intensity ratio was significantly higher on HASTE than in readout-segmented EPI, facilitating enhanced detection (mean difference 0.5; 95% CI, 0.3-0.8; P = .003). CONCLUSIONS: HASTE outperforms readout-segmented EPI in the detection of primary cholesteatoma and disease recidivism.

Beyond Tympanomastoidectomy: A Review of Less Common Postoperative Temporal Bone CT Findings.

Postoperative temporal bone imaging after surgical procedures such as ossiculoplasty, tympanomastoidectomy, cochlear implantation, and vestibular schwannoma resection is often encountered in clinical neuroradiology practice. Less common otologic procedures can present diagnostic dilemmas, particularly if access to prior operative reports is not possible. Lack of familiarity with the less common surgical procedures and expected postoperative changes may render radiologic interpretation challenging. This review illustrates key imaging findings after surgery for Ménière disease, superior semicircular canal dehiscence, temporal encephalocele repairs, internal auditory canal decompression, active middle ear implants, jugular bulb and sigmoid sinus dehiscence repair, and petrous apicectomy.

The Many Faces of Persistent Stapedial Artery: CT Findings and Embryologic Explanations.

Persistent stapedial artery is a vascular anomaly with both clinical and surgical implications. Because of its scarcity, however, it remains underrecognized on imaging. Presented here is a series of 10 cases, demonstrating characteristic CT findings associated with this vascular anomaly and its most common pathognomonic imaging signs. The variable morphologic configurations and their corresponding embryologic underpinnings are described. Clinical and surgical implications of this rare anomaly are discussed.

Imaging Findings Related to the Valsalva Maneuver in Head and Neck Radiology.

Forced exhalation against a closed glottis, known as the Valsalva maneuver, is an important clinical diagnostic and therapeutic tool due to its physiologic effects. Several unique conditions and anatomic changes can occur with repetitive or acute changes in pressure from the Valsalva maneuver. We will discuss and review various pertinent head and neck imaging cases with findings resulting from induced pressure gradients, including the Valsalva maneuver. Additionally, we will demonstrate the diagnostic utility of the Valsalva maneuver in head and neck radiology.

Prevalence of Spontaneous Asymptomatic Facial Nerve Canal Meningoceles: A Retrospective Review.

BACKGROUND AND PURPOSE: The prevalence of patent facial nerve canals and meningoceles along the facial nerve course is unknown. This study aimed to assess the frequency of such findings in asymptomatic patients. MATERIALS AND METHODS: A retrospective review was completed of patients with high-resolution MR imaging of the temporal bone whose clinical presentations were unrelated to facial nerve pathology. Facial nerve canals were assessed for the presence of fluid along each segment and meningoceles within either the labyrinthine segment (fluid-filled distention, ≥1.0-mm diameter) or geniculate ganglion fossa (fluid-filled distention, ≥2.0-mm diameter). If a meningocele was noted, images were assessed for signs of CSF leak. RESULTS: Of 204 patients, 36 (17.6%) had fluid in the labyrinthine segment of the facial nerve canal and 40 (19.6%) had fluid in the geniculate ganglion fossa. Five (2.5%) had meningoceles of the geniculate ganglion fossa; no meningoceles of the labyrinthine segment of the canal were observed. No significant difference was observed in the ages of patients with fluid in the labyrinthine segment of the canal or geniculate ganglion compared with those without fluid (P = .177 and P = .896, respectively). Of the patients with a meningocele, one had a partially empty sella and none had imaging evidence of CSF leak or intracranial hypotension. CONCLUSIONS: Fluid within the labyrinthine and geniculate segments of the facial nerve canal is relatively common. Geniculate ganglion meningoceles are also observed, though less frequently. Such findings should be considered of little clinical importance without radiologic evidence of CSF otorrhea, meningitis, or facial nerve palsy.

Isolated Internal Auditory Canal Diverticula: A Normal Anatomic Variant Not Associated with Sensorineural Hearing Loss.

BACKGROUND AND PURPOSE: Bony internal auditory canal diverticula are relatively common, occurring in approximately 5% of temporal bone CTs. Internal auditory canal diverticula have historically been considered incidental; however, a recent publication reported that internal auditory canal diverticula are associated with sensorineural hearing loss. The objective of this study was to further characterize this potential association in a large cohort of patients. MATERIALS AND METHODS: A total of 1759 patients undergoing high-resolution temporal bone CT were collected during a 6-year interval, and audiometric data were obtained from those with internal auditory canal diverticula. To assess any association of isolated internal auditory canal diverticula with sensorineural hearing loss, we excluded from further analysis patients with concomitant otosclerosis and bilateral diverticula and those without audiometric data, leaving 22 index cases. Audiometric data for the ear with a diverticulum was compared with that in the contralateral ear, to serve as an internal control. RESULTS: Of 1759 patients, 82 (4.7%) had either unilateral (n = 33, 40%) or bilateral (n = 49, 60%) internal auditory canal diverticula. The co-incidence of otosclerosis and internal auditory canal diverticula was 34% (n = 28). There was no correlation between patient age and diverticulum size on either side. Among the index cases with isolated unilateral internal auditory canal diverticula and complete audiometric data, word recognition scores and the prevalence and severity of sensorineural hearing loss were not significantly different comparing the internal auditory canal diverticulum side to its contralateral control. CONCLUSIONS: This study did not find a statistically significant association between ears with internal auditory canal diverticula and worsening sensorineural hearing loss or word recognition. Internal auditory canal diverticula most likely represent a normal anatomic variant in ears without otosclerosis.

Comparison of a Photon-Counting-Detector CT with an Energy-Integrating-Detector CT for Temporal Bone Imaging: A Cadaveric Study.

BACKGROUND AND PURPOSE: Evaluating abnormalities of the temporal bone requires high-spatial-resolution CT imaging. Our aim was to assess the performance of photon-counting-detector ultra-high-resolution acquisitions for temporal bone imaging and compare the results with those of energy-integrating-detector ultra-high-resolution acquisitions. MATERIALS AND METHODS: Phantom studies were conducted to quantify spatial resolution of the ultra-high-resolution mode on a prototype photon-counting-detector CT scanner and an energy-integrating-detector CT scanner that uses a comb filter. Ten cadaveric temporal bones were scanned on both systems with the radiation dose matched to that of the clinical examinations. Images were reconstructed using a sharp kernel, 0.6-mm (minimum) thickness for energy-integrating-detector CT, and 0.6- and 0.25-mm (minimum) thicknesses for photon-counting-detector CT. Image noise was measured and compared using adjusted 1-way ANOVA. Images were reviewed blindly by 3 neuroradiologists to assess the incudomallear joint, stapes footplate, modiolus, and overall image quality. The ranking results for each specimen and protocol were compared using the Friedman test. The Krippendorff α was used for interreader agreement. RESULTS: Photon-counting-detector CT showed an increase of in-plane resolution compared with energy-integrating-detector CT. At the same thickness (0.6 mm), images from photon-counting-detector CT had significantly lower (P < .001) image noise compared with energy-integrating-detector CT. Readers preferred the photon-counting-detector CT images to the energy-integrating-detector images for all 3 temporal bone structures. A moderate interreader agreement was observed with the Krippendorff α = 0.50. For overall image quality, photon-counting-detector CT image sets were ranked significantly higher than images from energy-integrating-detector CT (P < .001). CONCLUSIONS: This study demonstrated substantially better delineation of fine anatomy for the temporal bones scanned with the ultra-high-resolution mode of photon-counting-detector CT compared with the ultra-high-resolution mode of a commercial energy-integrating-detector CT scanner.

Vertebroplasty, first 1000 levels of a single center: evaluation of the outcomes and complications.

BACKGROUND AND PURPOSE: Percutaneous polymethylmethacrylate (PMMA) vertebroplasty has become a common procedure for treatment of pain and disability associated with vertebral compression fractures. We reviewed the experience with our first 1000 consecutively treated vertebral compression fractures in an attempt to demonstrate both the short- and long-term safety and efficacy of percutaneous vertebroplasty. MATERIALS AND METHODS: The first 1000 compression fractures treated by vertebroplasty at our institution were identified from a comprehensive prospectively acquired vertebroplasty data base. All patients treated with vertebroplasty were included, regardless of the underlying pathologic cause. Chart reviews of the procedure notes, imaging studies, clinical visits, and follow-up telephone interviews were performed for each patient. Evaluation at each follow-up time point included pain response (subjective and visual analog pain score), change in mobility, change in pain medication usage, and modified Roland-Morris Disability Questionnaire. Statistical analysis was performed on the pain response and change in the Roland-Morris score at each follow-up time point. Significant procedure-related complications that occurred from the time of the procedure were also specifically extracted from the patients' charts. RESULTS: There was a dramatic improvement in all the evaluated parameters following percutaneous vertebroplasty. The improvement in pain, mobility, medication usage, and Roland-Morris score was noticed immediately after the procedure and persisted through the 2-year follow-up. There was a low rate of complications from the procedure, the most common being rib fractures. CONCLUSION: According to our results, practitioners can quote a high success rate and low complication rate for vertebroplasty when making treatment recommendations for painful spinal compression fractures.

Subsequent vertebral fractures after vertebroplasty: association with intraosseous clefts.

BACKGROUND AND PURPOSE: Patients with vertebral fractures containing intraosseous clefts may represent a distinct subgroup of vertebroplasty patients, yet the development of subsequent vertebral fractures in this population has not been explored. We tested the hypothesis that after vertebroplasty for intraosseous clefts, subsequent fractures would occur earlier and more frequently than after treatment of non-cleft-containing fractures. METHODS: We retrospectively reviewed 362 patients treated with vertebroplasty for osteoporotic fractures. The location, frequency, and timing of subsequent fractures were compared between 2 subgroups: group 1, patients treated at fractures containing clefts, and group 2, treated patients without clefts. A vertebra-by-vertebra analysis was used to compare the relative risk and timing of subsequent fractures adjacent to vertebrae with or without clefts. RESULTS: Group 1 included 63 patients treated at 65 vertebrae and group 2 included 250 patients treated at 399 vertebrae. Group 1 demonstrated a nearly twofold increased risk of subsequent fracture (odds ratio [OR], 1.90; 95% confidence interval [CI], 1.04-3.49, P = .037). At the vertebral level, the relative risk of subsequent fracture was 2.02 (95% CI, 1.46-2.58; P = .013) times greater adjacent to a treated cleft. Fractures adjacent to any treated level occurred significantly sooner than nonadjacent fracture (P = .0004). The presence of a cleft was not significantly associated with the timing of subsequent fractures. CONCLUSIONS: Patients with osteoporotic vertebral fractures containing clefts are at increased risk for subsequent fractures and treatment of these clefts is associated with increased rates of adjacent fracture. There is no significant difference in the timing of subsequent fractures based on the presence of a cleft.

Predicting High-Flow Spinal CSF Leaks in Spontaneous Intracranial Hypotension Using a Spinal MRI-Based Algorithm: Have Repeat CT Myelograms Been Reduced?

BACKGROUND AND PURPOSE: We adopted an imaging algorithm in 2011 in which extradural fluid on spinal MR imaging directs dynamic CT myelography. We assessed algorithm compliance and its effectiveness in reducing repeat or unnecessary dynamic CT myelograms. MATERIALS AND METHODS: CT myelograms for CSF leaks from January 2011 to September 2014 were reviewed. Patients with iatrogenic leaks, traumatic brachial plexus injuries, or prior CT myelography within 2 years were excluded. Completion and results of spinal MR imaging, CT myelographic technique, and the need for repeat CT myelography or unnecessary dynamic CT myelograms were recorded. RESULTS: The algorithm was followed in 102 (79%) of 129 patients. No extradural fluid was detected in 75 (74%), of whom 70 (93%) had no leak, 4 (5%) had a slow leak, and 1 (1%) had a fast leak. Extradural fluid was detected in 27 (26%): 24 (89%) fast leaks, 1 (4%) slow leak, and 2 (7%) with no leaks. When the algorithm was followed, 1 (1%) required repeat CT myelography and 3 (3%) had unnecessary dynamic CT myelograms. The algorithm was breached in 27 (21%) cases, including no pre-CT myelogram MR imaging in 11 (41%), performing conventional CT myelography when extradural fluid was present in 13 (48%), and performing dynamic CT myelography when extradural fluid was absent in 3 (11%). Algorithm breaches resulted in 4 (15%) repeat CT myelograms and 3 (12%) unnecessary dynamic CT myelograms, both higher than with algorithm compliance. CONCLUSIONS: Using spinal MR imaging to direct CT myelography resulted in significant reduction in repeat CT myelograms to localize fast leaks with minimal unnecessary dynamic CT myelograms.

Imaging appearance of dextranomer/hyaluronic acid copolymer implant injections for treatment of velopharyngeal insufficiency.

BACKGROUND AND PURPOSE: Dextranomer/hyaluronic acid copolymer implants are used in treating velopharyngeal insufficiency. These posterior nasopharyngeal implants can be mistaken for pathologic conditions such as retropharyngeal abscess on imaging. We studied the imaging appearance of dextranomer/hyaluronic acid copolymer implants in patients treated for velopharyngeal insufficiency. MATERIALS AND METHODS: A consecutive series of patients with velopharyngeal insufficiency treated with dextranomer/hyaluronic acid copolymer were included in this study. Data on patient characteristics and volume of dextranomer/hyaluronic acid copolymer injected were obtained. Postoperative imaging characteristics on plain radiography, CT, and MR imaging were assessed. The imaging appearance of postoperative complications was determined. RESULTS: Sixteen patients were included in this study. Seven patients underwent postoperative plain radiographs, 5 patients underwent CT, and 9 patients underwent MR imaging. Plain radiographs demonstrated soft-tissue swelling in the retropharyngeal space, which resolved at 1 month. On CT, dextranomer/hyaluronic acid copolymer implants appeared as bilateral nasopharyngeal soft-tissue masses isoattenuated to hypoattenuated relative to muscle in 80% (4/5) of patients. On MR imaging, dextranomer/hyaluronic acid copolymer implants appeared as bilateral nasopharyngeal soft-tissue masses that were isointense to muscle on T1 (8/9, 88.9%) and hyperintense to muscle on T2 (8/9, 88.9%) and demonstrated no restricted diffusion (4/4, 100.0%) or peripheral enhancement (7/7, 100.0%). CONCLUSIONS: The normal postoperative findings of posterior nasopharyngeal dextranomer/hyaluronic acid copolymer injection on MR imaging is characterized by the presence of bilateral nasopharyngeal soft-tissue masses that are isointense to muscle on T1 and hyperintense on T2, with no restricted diffusion or peripheral enhancement. Velopharyngeal dextranomer/hyaluronic acid copolymer implants are iso- to hypoattenuated to muscle on CT and are not visible radiographically once associated implantation-related swelling has resolved.

Temporal Bone CT: Improved Image Quality and Potential for Decreased Radiation Dose Using an Ultra-High-Resolution Scan Mode with an Iterative Reconstruction Algorithm.

BACKGROUND AND PURPOSE: Radiation dose in temporal bone CT imaging can be high due to the requirement of high spatial resolution. In this study, we assessed whether CT imaging of the temporal bone by using an ultra-high-resolution scan mode combined with iterative reconstruction provides higher spatial resolution and lower image noise than a z-axis ultra-high-resolution mode. MATERIALS AND METHODS: Patients with baseline temporal bone CT scans acquired by using a z-axis ultra-high-resolution protocol and a follow-up scan by using the ultra-high-resolution-iterative reconstruction technique were identified. Images of left and right temporal bones were reconstructed in the axial, coronal, and Poschl planes. Three neuroradiologists assessed the spatial resolution of the following structures: round and oval windows, incudomallear and incudostapedial joints, basal turn spiral lamina, and scutum. The paired z-axis ultra-high-resolution and ultra-high-resolution-iterative reconstruction images were displayed side by side in random order, with readers blinded to the imaging protocol. Image noise was compared in ROIs over the posterior fossa. RESULTS: We identified 8 patients, yielding 16 sets of temporal bone images (left and right). Three sets were excluded because the patient underwent surgery between the 2 examinations. Spatial resolution was comparable (Poschl) or slightly better (axial and coronal planes) with ultra-high-resolution-iterative reconstruction than with z-axis ultra-high-resolution. A paired t test indicated that noise was significantly lower with ultra-high-resolution-iterative reconstruction than with z-axis ultra-high-resolution (P < .001), with a mean noise reduction of 37% (range, 18%-49%). CONCLUSIONS: The ultra-high-resolution-iterative reconstruction scan mode has similar or slightly better resolution relative to the z-axis ultra-high-resolution mode for CT of the temporal bone but significantly (P < .01) lower image noise, which may enable the dose to be reduced by approximately 50%.

Clinical and radiographic features of dural arteriovenous fistula, a treatable cause of myelopathy.

OBJECTIVE: To assess presentation, imaging, treatment, and outcome of patients with myelopathy due to a dural arteriovenous fistula (DAVF). PATIENTS AND METHODS: This retrospective review identified 94 patients with DAVF surgically treated at our institution between June 1985 and December 1999. The mean ages of the 75 men and 19 women were 62.6 years and 63.0 years, respectively (range, 31-83 years). Magnetic resonance imaging was performed in 87 patients, computed tomography-myelography was performed in 37 patients, and spinal angiography was performed in all patients. Initial examination findings were retrospectively adjusted to a modified Aminoff-Logue myelopathy scale. RESULTS: Of the 94 patients, 47 presented with symptoms that worsened with erect posture or Valsalva maneuver. As myelopathy progressed, patients' symptoms increased, and 6 patients had paraplegia at presentation. The mean time from symptom onset to diagnosis was 23 months (range, 2-120 months). Magnetic resonance imaging confirmed the diagnosis in 86 patients; computed tomography-myelography was needed to confirm the fistula in 1 patient. Spinal angiography detected the fistula in all patients. Surgical obliteration of the DAVF was successful in 93 patients; in 1 patient surgery failed because the DAVF was not localized, but acrylic endovascular embolization was successful. No patient experienced permanent morbidity or mortality. Of the 94 patients, 93 improved postoperatively 1 or 2 levels based on a modified Aminoff-Logue scale. Older patients with severe long-term deficits had poor outcomes. CONCLUSIONS: The diagnosis of a DAVF seems to be delayed considerably because DAVF is not included in the differential diagnosis of myelopathy and because of clinicians' unfamiliarity with suggestive or revealing findings on diagnostic imaging. Neurodiagnostic imaging confirms the diagnosis, and spinal angiography localizes the fistula. Surgical intradural disconnection of the DAVF clinically reverses the pathophysiology. Additionally, surgical treatment is associated with low short-term morbidity, no permanent morbidity, and no mortality. If the diagnosis is made early and treatment initiated in such patients, they generally do well.

Enhanced lumbar nerve roots in the spine without prior surgery: radiculitis or radicular veins?

PURPOSE: To evaluate the clinical significance of continuous intradural lumbosacral nerve root enhancement in symptomatic patients without prior lumbar surgery. METHODS: Fifty-three patients without prior back surgery, referred to our institution for evaluation of low-back pain and radiculopathy, were studied with gadolinium-enhanced MR (0.1 mmol/kg) of the lumbar spine. Scans were reviewed for the presence of lumbosacral nerve root enhancement and any associated nerve root compression. Results were correlated with clinical history and physical examinations. RESULTS: Seventeen continuously enhancing nerve roots and two enhancing fila terminale were observed in 13 patients. Eight of 17 (47%) had no referable symptoms. Nine of these nerve roots (53%) were not associated with any degree of nerve root compression. Seven cases (41%) were noted to have flow-related enhancement on the entry section of the T1-weighted axial sequence. CONCLUSIONS: Lumbosacral nerve root enhancement correlates poorly with clinical radiculopathy. The use of contrast enhancement to detect lumbosacral nerve root enhancement in cases in which the unenhanced scan is less than diagnostic is not warranted. The high association between lumbosacral nerve root enhancement and entry-section flow-related enhancement suggests that these enhancing structures within the cauda equina are vessels. It is likely that lumbosacral nerve root enhancement represents intravascular enhancement of radicular veins and not a breakdown in the blood-nerve barrier.

Corpus callosal signal changes in patients with obstructive hydrocephalus after ventriculoperitoneal shunting.

BACKGROUND AND PURPOSE: Few reports have documented signal abnormalities within the corpus callosum on MR studies obtained after ventricular decompression in patients with hydrocephalus. Our purpose was to establish the frequency of this finding in shunted patients and attempt to elucidate its cause and clinical significance. METHODS: All patients with hydrocephalus shunted between 1989 and 1999 with postoperative MR studies available for review were included in the study group. Imaging analysis consisted of documenting hypointense signal on T1-weighted sagittal images and hyperintense signal on double-echo T2-weighted axial images within the corpus callosum. RESULTS: Characteristic signal abnormalities in the corpus callosum were noted in nine of 161 patients with shunted hydrocephalus studied with MR imaging. All nine patients were asymptomatic in regard to these MR findings. Comparison with preoperative scans and surgical records revealed that all patients with signal changes on postshunt scans had chronic obstructive hydrocephalus at presentation. Preshunt MR images were notable for marked elevation of the corpus callosum, which subsequently descended after ventricular decompression, suggesting that the cause of the signal changes was related to compression of the corpus callosum against the rigid falx. CONCLUSION: Signal abnormalities within the corpus callosum after ventricular shunting for obstructive hydrocephalus are not uncommon and are probably produced by compression of the corpus callosum against the falx before ventricular decompression. This distinctive appearance should not be mistaken for significant disease. Recognition of this pattern of signal abnormality will help avoid unnecessary intervention.

Contrast-enhanced radicular veins on MR of the lumbar spine in an asymptomatic study group.

PURPOSE: To determine whether radicular enhancement occurs in asymptomatic persons and, if so, to provide insight into the mechanism of such enhancement. METHODS: Thirty asymptomatic volunteers were studied with gadolinium-enhanced MR (0.1 mmol/kg) of the lumbar spine. The precontrast axial T1-weighted sequences were reviewed for the entry section phenomenon of flow-related enhancement. If present, the sequence was repeated in combination with a superior saturation pulse in an attempt to eliminate this phenomenon. All studies were reviewed to document the incidence of radicular enhancement and determine its association with the entry section phenomenon. RESULTS: The entry section phenomenon was observed in 16 of 30 volunteers with successful elimination obtained in all cases. Eighteen of the volunteers demonstrated radicular enhancement; 16 of the 18 enhancing roots were associated with the entry section phenomenon. CONCLUSIONS: Radicular enhancement occurs commonly in asymptomatic volunteers. This phenomenon most likely represents the enhancement of prominent radicular veins. We urge caution in interpreting this finding as abnormal in the symptomatic population with degenerative disk disease.