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Background and purpose Radiation therapy is an important component of treatment in patients with malignancies of the head, neck, and spine. However, radiation to these regions has well-known potential side effects, many of which can be encountered on imaging. In this manuscript, we review selected radiographic manifestations of therapeutic radiation to the head, neck, and spine that may be encountered in the practice of radiology. Methods We conducted an extensive literature review of known complications of radiation therapy in the head, neck, and spine. We excluded intracranial and pulmonary radiation effects from our search. We selected complications that had salient, recognizable imaging findings. We searched our imaging database for illustrative examples of these complications. Results Based on our initial literature search and imaging database review, we selected cases of radiation-induced tumors, radiation tissue necrosis (osteoradionecrosis and soft tissue necrosis), carotid stenosis and blowout secondary to radiation, enlarging thyroglossal duct cysts, radiation myelopathy, and radiation-induced vertebral compression fractures. Conclusions We describe the clinical and imaging features of selected sequelae of radiation therapy to the head, neck, and spine, with a focus on those with characteristic imaging findings that can be instrumental in helping to make the diagnosis. Knowledge of these entities and their imaging findings is crucial for accurate diagnosis. Not only do radiologists play a key role in early detection of these entities, but many of these entities can be misinterpreted if one is not familiar with them.

Intrathecal gadolinium magnetic resonance (MR) myelography can be used to localize various types of spinal cerebrospinal fluid (CSF) leaks; however, its diagnostic yield is not well known. We sought to determine the diagnostic yield of MR myelography in patients with spontaneous intracranial hypotension. A retrospective review was performed on all patients who had undergone intrathecal gadolinium MR myelography at our institution from 2002 to 2020 for suspected spinal CSF leak. The MR myelography images were reviewed for the presence or absence of a spinal CSF leak site. Images were also evaluated for the presence an extradural fluid collection. A total of 97 patients were included in the final cohort. The average age was 52.6 years; 67.0% were female, 4 patients underwent 2 examinations each, yielding a total of 101 MR myelograms. The source of a spinal CSF leak was localized in 14 patients. The diagnostic yield for CSF leak localization on intrathecal gadolinium MR myelography was 14/101 (13.9%) per GdM examination and 14/97 (14.4%) per patient. Among the subset of patients without extradural fluid collections, the yield was 15.7% per examination. All detected leaks were either CSF-venous fistulas or distal nerve root sleeve tears. Intrathecal gadolinium MR myelography is capable of localizing CSF-venous fistulas and distal nerve root sleeve tears; however, our data show that it has a limited diagnostic yield. We suggest that other modalities may be a better first step before attempting intrathecal gadolinium MR myelography.

BackgroundCT-guided biopsy is a commonly used diagnostic procedure for spinal lesions. This meta-analysis aims to investigate its diagnostic performance and complications, as well as factors influencing outcomes.MethodsA systematic review of the literature was performed to identify studies reporting outcomes of CT-guided biopsies for spinal lesions. Diagnostic yield (ie, the rate of procedures resulting in a specific pathological diagnosis) and diagnostic accuracy (ie, the rate of procedures resulting in the correct diagnosis) were the primary outcomes of interest. Complications following biopsy procedures were also included.ResultsThirty-nine studies with 3917 patients undergoing 4181 procedures were included. Diagnostic yield per procedure was 91% (95% CI 88% to 94%) among 3598 procedures. The most common reason for non-diagnostic biopsies was inadequacy of sample. No difference in diagnostic yield between different locations and between lytic, sclerotic, and mixed lesions was found. Diagnostic yield did not differ between procedures using ≤13G and ≥14G needles. Diagnostic accuracy per procedure was 86% (95% CI 82% to 89%) among 3054 procedures. Diagnostic accuracy among 2426 procedures that yielded a diagnosis was 94% (95% CI 92% to 96%). Complication rate was 1% (95% CI 0.4% to 1.9%) among 3357 procedures. Transient pain and minor hematoma were the most common complications encountered.ConclusionIn our meta-analysis of 39 studies reporting diagnostic performance and complications of CT-guided biopsy, we found a diagnostic yield of 91% and diagnostic accuracy of 86% with a complication rate of 1%. Diagnostic yield did not differ between different locations, between lytic, sclerotic and mixed lesions, and between wide- and thin-bore needles.

Introduction There is increased interest in the use of artificial intelligence-based (AI) software packages in the evaluation of neuroimaging studies for acute ischemic stroke. We studied whether, compared to standard image interpretation without AI, Brainomix e-ASPECTS software improved interobserver agreement and accuracy in detecting ASPECTS regions affected in anterior circulation LVO. Methods We included 60 consecutive patients with anterior circulation LVO who had TICI 3 revascularization within 60 minutes of their baseline CT. A total of 16 readers, including senior neuroradiologists, junior neuroradiologists and vascular neurologists participated. Readers interpreted CT scans on independent workstations and assessed final ASPECTS and evaluated whether each individual ASPECTS region was affected. Two months later, readers again evaluated the CT scans, but with assistance of e-ASPECTS software. We assessed interclass correlation coefficient for total ASPECTS and interobserver agreement with Fleiss’ Kappa for each ASPECTS region with and without assistance of the e-ASPECTS. We also assessed accuracy for the readers with and without e-ASPECTS assistance. In our assessment of accuracy, ground truth was the 24 hour CT in this cohort of patients who had prompt and complete revascularization. Results Interclass correlation coefficient for total ASPECTS without e-ASPECTS assistance was 0.395, indicating fair agreement compared, to 0.574 with e-ASPECTS assistance, indicating good agreement (P Conclusions Use of Brainomix e-ASPECTS software resulted in significant improvements in inter-rater agreement and accuracy of ASPECTS score evaluation in a large group of neuroradiologists and neurologists. e-ASPECTS software was more predictive of final infarct/ASPECTS than the overall group interpreting the CT scans with and without e-ASPECTS assistance.

Spinal metastases are most commonly osseous and may extend to the epidural space. Less commonly, spinal metastases can be subdural, leptomeningeal, or intramedullary. Among these, subdural metastases are the most rare, with few reported cases. While these lesions are now almost exclusively detected on MRI, they can rarely be apparent on other modalities. It is important to recognize subdural metastases on any modality, because they have a significant impact on patient prognosis and treatment. We report a case of renal cell carcinoma in a 68-year-old male initially presenting with subdural metastases detected on CT myelography, with subsequent confirmation by MRI. The case illustrates, to our knowledge, the first example of subdural metastatic disease seen on CT myelography.

Introduction Spontaneous intracranial hypotension (SIH) caused by a spinal cerebrospinal fluid (CSF) leak classically presents with orthostatic headache. Digital subtraction myelography (DSM) has a well-established diagnostic yield in the absence of extradural spinal collection. At our institution, DSM is followed by lateral decubitus CT myelogram (LDCTM) in the same decubitus position to increase diagnostic yield of the combined study. We evaluated the incremental diagnostic yield of LDCTM following negative DSM and reviewed patient outcomes. Methods Retrospective review of consecutive DSMs with subsequent LDCTM from April 2019 to March 2021 was performed. Combined reports were reviewed, and studies with positive DSMs were excluded. Of the exams with negative DSM, only studies with LDCTM reports identifying potential leak site were included. Interventions and follow-up clinical notes were reviewed to assess symptoms improvement following treatment. Results Of the 83 patients with negative DSMs, 11 (13.2%) had positive leak findings on LDCTMs, and 21 (25.3%) were equivocal. Of 11 positive LDCTMs, 6 leaks were nerve sheath tears (NSTs) and 5 were CSF-venous fistulas (CVFs). 10/11 (90.9%) had intervention and follow-up, with 9/10 (90%) having positive clinical outcome. Of the 21 equivocal LDCTM patients (19 CVFs and 2 NSTs), 15 (71.4%) had interventions and follow-up, with 3/15 (20.0%) with positive clinical outcomes. Conclusion LDCTM following negative DSM has an incremental diagnostic yield up to 38.6%, with up to 14.5% of positive patient outcomes following treatment. LDCTM should be considered after DSM to maximize diagnostic yield of the combined exam.

Torus mandibularis is a benign osseous overgrowth arising from the lingual surface of the mandible. It is a common, incidental finding on imaging due to its relatively high prevalence. In the majority of cases, mandibular tori are asymptomatic. We report a novel presentation of a giant torus mandibularis causing bilateral obstruction of the submandibular ducts and consequent sialadenitis. Our patient presented with progressive pain centered in the floor of his mouth and had bilateral submandibular glandular enlargement on exam. Computed tomography showed a giant right torus mandibularis, which was causing obstruction and dilation of the bilateral submandibular ducts. Although conservative management was attempted, he ultimately underwent surgical resection of his torus with symptomatic improvement. This patient highlights a novel complication of torus mandibularis and illustrates successful treatment. Though not previously described, this complication may be underreported and should be considered in the appropriate clinical setting.

Standard clinical protocols require hearing protection during magnetic resonance imaging (MRI) for patient safety. This investigation prospectively evaluated the auditory function impact of acoustic noise exposure during a 3.0T MRI in healthy adults. Twenty-nine participants with normal hearing underwent a comprehensive audiologic assessment before and immediately following a clinically indicated head MRI. Appropriate hearing protection with earplugs (and pads) was used per standard of practice. To characterize noise hazards, current sound monitoring tools were used to measure levels of pulse sequences measured. A third audiologic test was performed if a significant threshold shift (STS) was identified at the second test, within 30 days post MRI. Some sequences produced high levels (up to 114.5 dBA; 129 dB peak SPL) that required hearing protection but did not exceed 100% daily noise dose. One participant exhibited an STS in the frequency region most highly associated with noise-induced hearing loss. No participants experienced OSHA-defined STS in either ear. Overall, OAE measures did not show evidence of changes in cochlear function after MRI. In conclusion, hearing threshold shifts associated with hearing loss or OAE level shifts reflecting underlying cochlear damage were not detected in any of the 3.0T MRI study participants who used the current recommended hearing protection.

Dural tears are a common cause of spontaneous spinal CSF leaks. The majority of such leaks occur ventrally along the thecal sac, typically due to ventral osseous spicules that cause a rent in the dura. A minority of dural leaks are posterolateral in location. These leaks usually do not have an identifiable anatomic cause. We have anecdotally observed cases of posterolateral leaks caused by osseous spicules and sought to describe this phenomenon.We retrospectively reviewed our imaging database, searching for cases of posterolateral CSF leaks caused by osseous spicules. We identified and included three such patients and reviewed imaging and clinical information from each patient.All three patients had been diagnosed using hyperdynamic CT myelography or conventional CT myelography. Their imaging showed dorsal epidural fluid collections that were related to posterolateral leaks adjacent to dorsal osseous spicules.Dorsal osseous spicules have the potential to cause posterolateral CSF leaks.

BACKGROUND AND PURPOSE: Digital subtraction myelography performed with the patient in the lateral decubitus position has the potential for increased sensitivity over prone-position myelography in the detection of spinal CSF-venous fistulas, a well-established cause of spontaneous intracranial hypotension. We report on the safety of performing routine, consecutive-day right and left lateral decubitus digital subtraction myelography in these patients. MATERIALS AND METHODS: In this retrospective case series, all patients undergoing consecutive-day lateral decubitus digital subtraction myelography for suspected spinal CSF leak between September 2018 and September 2019 were identified. Chart review was performed to identify any immediate or delayed adverse effects associated with the procedures. Procedural parameters were also analyzed due to inherent variations associated with the positive-pressure myelography technique that was used. RESULTS: A total of 60 patients underwent 68 pairs of consecutive-day lateral decubitus digital subtraction myelographic examinations during the study period. No major adverse effects were recorded. Various minor adverse effects were observed, including pain requiring analgesics (27.2%), nausea/vomiting requiring antiemetics (8.1%), and transient neurologic effects such as syncope, vertigo, altered mental status, and autonomic dysfunction (5.1%). Minor transient neurologic effects were correlated with increasing volumes of intrathecal saline injectate used for thecal sac prepressurization. CONCLUSIONS: In patients with spontaneous intracranial hypotension and suspected spontaneous spinal CSF leak, consecutive-day lateral decubitus digital subtraction myelography demonstrates an acceptable risk profile without evidence of neurotoxic effects from cumulative intrathecal contrast doses. Higher intrathecal saline injectate volumes may correlate with an increased incidence of minor transient periprocedural neurologic effects.

BACKGROUND AND PURPOSE: Inadvertent subdural contrast injections can occur during any myelogram. Currently, there are no guidelines defining when residual subdural iodinated contrast will be cleared and no longer interfere with subsequent procedure and imaging. We investigated the time to resolution of subdural contrast using a 2-day lateral decubitus digital subtraction myelogram and associated CT myelogram data in patients undergoing evaluation for spontaneous intracranial hypotension. MATERIALS AND METHODS: Retrospective review of 63 patients with lateral decubitus digital subtraction myelograms from September 4, 2018, to October 1, 2019, was performed. Patients with 2-day lateral decubitus digital subtraction myelograms on 2 consecutive days, with or without a same-day CT myelogram on day 1 and with a same-day CT myelogram on day 2, were included. Patients with next-day CT covering at least the abdomen and pelvis after either-day injection were also included. In cases of subdural injection, next-day CT scans were evaluated for residual subdural contrast. RESULTS: Of 49 included patients, 5 had subdural injection on day 1, with the second-day CT myelogram available for review. One of these 5 patients had subdural injections on 2 different days and subsequently had chest/abdomen/pelvis CTA a day after the second subdural injection. In all 6 cases of subdural injections, there was complete resolution of subdural contrast on the next-day CT, with the shortest time to resolution of approximately 20.5 hours (range, 20.5–28.5 hours). CONCLUSIONS: Our study suggests that resolution of inadvertently injected subdural contrast occurs within 1 day, and the myelogram can be reattempted as early as the next day.

Chordomas are rare primary bone malignancies derived from notochord remnants. The tumors often are slow-growing and often present with indolent, nonspecific symptoms. Nevertheless, chordomas are locally aggressive and highly prone to local recurrence, necessitating precise planning before biopsy and/or surgical resection. Familiarity with the imaging features of chordomas is, therefore, essential. This case highlights the typical imaging and pathologic features of a spinal chordoma as well as the surgical approach and the patient’s subsequent outcome.

Spontaneous intracranial hypotension is a condition characterized by low CSF volume secondary to leakage through a dural defect with no identifiable cause. Patients classically present with orthostatic headaches, but this symptom is not specific to spontaneous intracranial hypotension, and initial misdiagnosis is common. The most prominent features of spontaneous intracranial hypotension on intracranial MR imaging include “brain sag” and diffuse pachymeningeal enhancement, but these characteristics can be seen in several other conditions. Understanding the clinical and imaging features of spontaneous intracranial hypotension and its mimickers will lead to more prompt and accurate diagnoses. Here we discuss conditions that mimic the radiologic and clinical presentation of spontaneous intracranial hypotension as well as other disorders that CSF leaks can imitate.

Background Virchow-Robin or enlarged perivascular spaces (PVS) are benign pial-lined spaces that surround penetrating arteries and arterioles through the brain parenchyma. We present 2 cases of enlarging PVS in adults following whole-brain radiation therapy. Case Description Two patients underwent whole-brain radiation therapy for adult-onset medulloblastoma. Neither patient had enlarged PVS at the time of radiation treatment. The patients presented with PVS in the basal ganglia 6 and 8 years following the completion of radiation, respectively. One patient subsequently showed a decrease in size of PVS over time. Neither patient experienced symptoms, required surgical intervention, or had signs of tumor recurrence. Conclusions Enlarging PVS can occur years after radiation therapy to the brain parenchyma. Recognition of these benign PVS is important so as not to mistake the changes for more sinister pathology that could lead to unnecessary intervention. Moreover, focal cystic changes more frequently seen surrounding areas of focal brain radiation therapy might represent enlarged PVS.

Background Klippel-Trenaunay syndrome (KTS) is associated with a wide variety of vascular and neurologic abnormalities, including venolymphatic malformations. A recent report postulated that patients with KTS may also be predisposed to spontaneous intracranial hypotension. We reviewed brain magnetic resonance imaging from 67 patients with KTS and unexpectedly noted findings of cerebrospinal fluid (CSF) hypotension in 4 of them. Case Description Patients included a 39-year-old woman with episodic orthostatic headaches, a 62-year-old woman with orthostatic headaches and light-headedness, a 14-year-old girl with a history of headaches for years, and an asymptomatic 20-year-old man. All 4 patients had known KTS, and all had brain magnetic resonance imaging done during their evaluation showing evidence of CSF hypotension. The first 2 patients also had spine imaging demonstrating paraspinal and/or epidural venolymphatic malformations. The second patient had a meningeal diverticulum and underwent surgical repair with intraoperative evidence of a CSF leak. Conclusions Patients with KTS have an increased incidence of CSF hypotension. While it is possible that intrinsic dural weakness may be responsible for this association, we hypothesize that these patients are also predisposed to developing CSF venous fistulas. Paraspinal and epidural venolymphatic malformations have been described in multiple patients with CSF venous fistulas. Such malformations were present in 2 of our 4 patients who underwent spine imaging. Patients with KTS with orthostatic headaches may benefit from brain and spine magnetic resonance imaging to assess for evidence of CSF hypotension and venolymphatic malformations. Decubitus digital subtraction myelography may also have a role in these patients if CSF venous fistulas are suspected.

BACKGROUND AND PURPOSE There is a relative paucity of radiology literature on spinal cord cavernous malformations (SCMs). We hypothesized that the classic MRI features of cavernous malformations are not highly prevalent. The purpose was to review MR imaging findings of SCMs with a focus on prevalence of hemorrhagic features, including adjacent intramedullary hemorrhage at initial presentation. METHODS In this single-institution study, 78 SCMs in 76 patients diagnosed on imaging/pathology were retrospectively evaluated for size, location, cord expansion, exophytic component, popcorn morphology, signal characteristics, including T1 weighted (T1w) and T2w rims, blood-fluid levels, and adjacent intramedullary hemorrhage. Intramedullary hemorrhage was defined as centrally and/or eccentrically located linear or flame shaped non-edematous signal abnormality extending longitudinally away from SCMs, distinct from lesional rim. RESULTS Sixty-three percent (49/78) of SCMs measured

Hypertrophic olivary degeneration (HOD) is a condition caused by interruption of white matter tracts within the dentato-rubro-olivary pathway (DROP), resulting in inferior olivary T2 hyperintensity and enlargement on MRI. Olivary atrophy may be seen as a sequela of HOD.1 HOD has been described in association with brainstem infarcts, tumours, demyelination and vascular lesions such as cavernous malformations.2 However, HOD can also be seen in the absence of any lesion in the DROP and is sometimes idiopathic.3 Rhombencephalitis refers to inflammation involving the brainstem and/or cerebellum and can rarely be caused by paraneoplastic syndromes. Several neural specific antibodies are classically associated with paraneoplastic rhombencephalitis, including anti-Ma2 and antineuronal nuclear antibody type 2 (ANNA2 or anti-Ri). Kelch-like protein 11 (KLHL11) IgG is another recently described serological biomarker that has a strong association with paraneoplastic rhombencephalitis.4 The tumours frequently associated with paraneoplastic rhombencephalitis include testicular seminoma, breast cancer, small cell lung cancer and gynaecological malignancies. Brain MRI is often normal or shows progressive brainstem and cerebellar atrophy. MRI in these patients can also rarely show brainstem T2 hyperintensity and enhancement. A recently reported KLHL11 rhombencephalitis patient was incidentally noted to have left-sided HOD caused by a dentate lesion.4 However, no clear association between paraneoplastic rhombencephalitis and HOD has been previously suggested, even in comprehensive reviews.5 Here, we report six patients with onconeural antibody-associated paraneoplastic rhombencephalitis who developed HOD. Electronic medical records were queried to identify patients evaluated at our institution from 2005 to 2020 whose serum and/or cerebrospinal fluid demonstrated seropositivity to any of the following autoantibodies: type-1 antineuronal nuclear antibody (ANNA1/anti-Hu), KLHL11, Ma2, ANNA-2 (anti-Ri), Purkinje cell antibody type 1 (PCA-1, anti-Yo), collapsin response mediator 5 (CRMP5 or anti-CV2), amphiphysin and PCA-Tr (DNER). This revealed 177 total patients (KLHL11, n=24; Ma2, n=11; ANNA-1, n=60; ANNA-2, n=14; …

Background Spontaneous intracranial hypotension (SIH) is a debilitating disorder caused by non-iatrogenic spinal cerebrospinal fluid leaks. SIH is increasingly recognized as an important treatable cause of secondary headaches. Treatment involves either epidural blood patching or surgery, which have considerable differences in their adverse event rates, recovery times, and cost. The objective of this evidence map is to understand the breadth of studies that investigate SIH treatment efficacy and to identify knowledge gaps to inform future research. Methods This review will consider experimental, observational, and systematic review studies that assess the efficacy of epidural blood patching and surgery for the treatment of patients with SIH. Individual case studies, clinical guidelines, editorials, protocols, and studies that do not assess an intervention will not be included. English language studies will be included without limitation based on the date of publication. Databases to be searched include MEDLINE® (via Ovid), EMBASE (via Elsevier), and Web of Science™ (via Clarivate). Study selection will be performed independently by two investigators with extracted data to include study type, the number of patients included, patient descriptors, intervention characteristics, and outcome measure used. Data will be presented through a narrative summary aided by tabular and graphical formats in a manner that aligns with the objective of the evidence mapping review. Discussion The overarching goal of this evidence map is to provide an improved understanding of the breadth of studies investigating SIH treatment efficacy in the literature and to thereby identify knowledge gaps that can inform future research directions. Trial registration OSF Registry https://osf.io/nwju7.

Purpose Understanding all factors that may impact radiation dose and procedural time is crucial to safe and efficient image-guided interventions, such as fluoroscopically guided sacroiliac (SI) joint injections. The purpose of this study was to evaluate the effect of flow pattern (intra- vs. periarticular), patient age, and body mass index (BMI) on radiation dose and fluoroscopy time. Methods A total of 134 SI joint injections were reviewed. Injectate flow pattern, age, and BMI were analyzed in respect to fluoroscopy time (minutes), radiation dose (kerma area product (KAP); µGy m2), and estimated skin dose (mGy). Results BMI did not affect fluoroscopy time, but increased BMI resulted in significantly higher skin and fluoroscopy doses ( p Conclusion Increased BMI had the largest impact on procedural radiation dose and skin dose. Flow pattern also showed a statistically significant association with radiation dose and skin dose, but the clinical difference was small. Proceduralists should be aware that BMI has the greatest impact on fluoroscopy dose and skin dose during SI joint injections compared to other factors.

Clival chordomas are classically thought of as locally aggressive tumors of the skull base and differentiate themselves from their benign counterparts by demonstrating moderate to marked contrast enhancement, reported as 95-100% in prior studies. The purpose of this review was to evaluate the imaging characteristics of lesions from a single institution classified as clival chordomas with an emphasis of highlighting lesions that do not follow the prevalent current description for chordoma. We searched our institutional databases for all patients with pathologically proven clival chordomas from 1997 to 2017 who had pre-operative imaging available. The images were evaluated for degree of contrast enhancement, MRI signal characteristics, osseous involvement, location, aggressiveness of appearance, and presence of calcifications. 28 cases were identified that had preoperative imaging available for review. Over half of the patients demonstrated either no/minimal (11/28, 39%) or mild enhancement (7/28, 25%). The remaining cases demonstrated moderate (4/28, 14%) and marked enhancement (6/28, 21%). The 4 lesions measuring less than 20 mm all had mild to minimal/no enhancement and lacked aggressive features on CT. Our experience finds that over half (64%) of clival chordomas will demonstrate mild or no enhancement at all. These findings suggest that the lack of MRI contrast enhancement should not be synonymous with a benign clival mass.

A 29-year-old woman with relapsed T-cell acute lymphoblastic leukemia presented with 4 months of progressive ataxia, weakness, and bowel/bladder incontinence. Symptoms started after completing 2 cycles of nelarabine. Examination revealed paraplegia and complete sensory loss from mid-chest down, loss of vibration and joint position in upper limbs, areflexia, and bilateral Babinski signs. EMG showed fibrillation potentials with no activated motor units in lower limbs. Laboratory workup, including paraneoplastic autoantibody panel, CSF analysis, vitamin B12, methylmalonic acid, and copper levels, was unremarkable. Spine MRI findings were consistent with nelarabine-induced subacute combined degeneration, including previously unreported lateral column involvement and cord enhancement (figure).1,2 The unremarkable CSF, MRI findings (tractopathy), and subacute course made alternative etiologies such as infection, infiltrative leukemia, ischemia, or cord hemorrhage less likely. The patient was treated conservatively and started to spontaneously improve. She then underwent allogenic stem cell transplantation. Three months later, she regained movement against gravity in all lower extremity muscles. However, she remained severely ataxic, requiring the use of a wheelchair. Repeat EMG showed reinnervation in most lower-limb muscles and less frequent fibrillation potentials.

Radiation therapy is commonly utilized in the majority of solid cancers and many hematologic malignancies and other disorders. While it has an undeniably major role in improving cancer survival, radiation therapy has long been recognized to have various negative effects, ranging from mild to severe. In this manuscript, we review several intracranial manifestations of therapeutic radiation, with particular attention to those that may be encountered by radiologists. We conducted an extensive literature review of known complications of intracranial radiation therapy. Based on this review, we selected complications that had salient, recognizable imaging findings. We searched our imaging database for illustrative examples of these complications, focusing only on patients who had a history of intracranial radiation therapy. We then selected cases that best exemplified expected imaging findings in these entities. Based on our initial literature search and imaging database review, we selected cases of radiation-induced meningioma, radiation-induced glioma, cavernous malformation, enlarging perivascular spaces, leukoencephalopathy, stroke-like migraine after radiation therapy, Moyamoya syndrome, radiation necrosis, radiation-induced labyrinthitis, optic neuropathy, and retinopathy. Although retinopathy is not typically apparent on imaging, it has been included given its clinical overlap with optic neuropathy. We describe the clinical and imaging features of selected sequelae of intracranial radiation therapy, with a focus on those most relevant to practicing radiologists. Knowledge of these complications and their imaging findings is important, because radiologists play a key role in early detection of these entities.

Purpose: Deep learning (DL) algorithms have shown promising results for brain tumor segmentation in MRI. However, validation is required prior to routine clinical use. We report the first randomized and blinded comparison of DL and trained technician segmentations. Approach: We compiled a multi-institutional database of 741 pretreatment MRI exams. Each contained a postcontrast T1-weighted exam, a T2-weighted fluid-attenuated inversion recovery exam, and at least one technician-derived tumor segmentation. The database included 729 unique patients (470 males and 259 females). Of these exams, 641 were used for training the DL system, and 100 were reserved for testing. We developed a platform to enable qualitative, blinded, controlled assessment of lesion segmentations made by technicians and the DL method. On this platform, 20 neuroradiologists performed 400 side-by-side comparisons of segmentations on 100 test cases. They scored each segmentation between 0 (poor) and 10 (perfect). Agreement between segmentations from technicians and the DL method was also evaluated quantitatively using the Dice coefficient, which produces values between 0 (no overlap) and 1 (perfect overlap). Results: The neuroradiologists gave technician and DL segmentations mean scores of 6.97 and 7.31, respectively (p

Background Diagnosis of spontaneous intracranial hypotension (SIH) may be delayed due to nonspecific symptoms and variable imaging findings. Cases of hyperostosis in children who are overshunted, a process that may be physiologically analogous to adults with SIH, have been reported by others and observed in our practice. The purpose of this retrospective study was to assess the frequency and pattern of calvarial hyperostosis in patients with SIH. Methods We retrospectively reviewed computed tomography and magnetic resonance imaging examinations from consecutive patients who underwent myelography for the evaluation of SIH to assess for the presence of generalized calvarial thickening or development of a secondary layer of bone. Patients with typical benign hyperostosis frontalis were excluded. Patient demographics and clinical factors were evaluated for association with hyperostosis. Results Among 285 patients with SIH, 40 (14.0%) demonstrated diffuse calvarial hyperostosis on imaging. Most of these patients (32/40; 80.0%) demonstrated a distinct circumferentially layered appearance to the skull, whereas 8 of 40 (20.0%) had generalized calvarial thickening without layering. Conclusions Diffuse calvarial hyperostosis, particularly the concentrically layered form that we term “layer cake skull,” is a relatively common imaging feature in patients with SIH. In the appropriate clinical context, this finding will allow the possibility of SIH to be raised based on computed tomography imaging, which is otherwise of limited utility in the initial diagnosis of this condition.

ObjectiveTo assess the diagnostic yield of lateral decubitus digital subtraction myelography (LDDSM) and stratify LDDSM diagnostic yield by the Bern spontaneous intracranial hypotension (SIH) score of preprocedure brain MRI.MethodsThis retrospective diagnostic study included consecutive adult patients investigated for SIH who underwent LDDSM. Patients without preprocedure brain and spine MRI and patients with extradural fluid collection on spine MRI (type 1 leak) were excluded. LDDSM images and brain MRIs were assessed by 2 independent blinded readers; a third reader adjudicated any discrepancies. Diagnostic yield of LDDSM was assessed, both overall and stratified by Bern SIH scoring.ResultsOf the 62 patients included in this study, 33 (53.2%) had a CSF leak identified on LDDSM. Right-sided leaks were more common (70.6%), and the most commonly identified levels of leaks were at T6, T7, and T10. No leak was found in any of the 9 patients with Bern SIH score of 2 or less. Of the 11 patients with Bern SIH score of 3–4, 5 (45.5%) had a CSF leak identified; of the 42 patients with Bern SIH score of 5 or higher, 28 (66.7%) had a CSF leak identified.ConclusionsLDDSM has a high diagnostic yield for finding the exact location of spinal CSF leak, and the diagnostic yield increases with higher Bern SIH score. No leaks were found in patients with Bern SIH score of 2 or less, suggesting that foregoing invasive testing such as LDDSM in these patients may be appropriate unless accompanied by high clinical suspicion.Classification of EvidenceThis study provides Class II evidence that for patients with suspected SIH, higher Bern SIH scores are associated with a greater likelihood of LDDSM-identified CSF leaks.

Paraneoplastic syndromes are systemic reactions to neoplasms mediated by immunologic or hormonal mechanisms. The most well-recognized paraneoplastic neurologic syndrome, both clinically and on imaging, is limbic encephalitis. However, numerous additional clinically described syndromes affect the brain, spinal cord, and peripheral nerves. Many of these syndromes can have imaging findings that, though less well described, are important in making the correct diagnosis. Moreover, imaging in these syndromes frequently mimics more common pathology, which can be a diagnostic challenge for radiologists. Our goal is to review the imaging findings of paraneoplastic neurologic syndromes, including less well-known entities and atypical presentations of common entities. Specifically, we discuss limbic encephalitis, paraneoplastic cerebellar degeneration, paraneoplastic brain stem encephalitis, cranial neuropathy, myelitis, and polyneuropathy. We also demonstrate common diagnostic pitfalls that can be encountered when imaging these patients.

A 69-year-old female presented with subacute onset ascending weakness and paraesthesias. She was initially diagnosed with Guillain–Barré syndrome (GBS) based on her clinical presentation and cerebrospinal fluid (CSF) analysis showing albuminocytological dissociation. However, she was later found to have anti-neuronal nuclear antibody 1 (ANNA-1/anti-Hu)-positive CSF and was subsequently diagnosed with small-cell lung cancer. Her neurological symptoms were ultimately attributed to ANNA-1/anti-Hu-associated paraneoplastic polyneuropathy. During the course of her evaluation, she had magnetic resonance imaging findings of dorsal predominant cauda equina nerve root enhancement, which has not been previously described. The only previously reported case of cauda equina enhancement due to ANNA-1-associated polyneuropathy described ventral predominant findings. The distinction between ventral and dorsal enhancement is important, since it suggests that different patterns of nerve root involvement may be associated with this paraneoplastic syndrome. Therefore, ANNA-1-associated paraneoplastic inflammatory polyneuropathy can be considered in the differential diagnosis of cauda equina nerve root enhancement with ventral and/or dorsal predominance. This can potentially be helpful in differentiating ANNA-1 polyneuropathy from GBS, which classically has ventral predominant enhancement.

The common carotid artery (CCA) and extracranial internal carotid artery are subject to a wide variety of non-atheromatous pathologies. These entities are often overshadowed in both research and clinical realms by atherosclerotic disease. Nevertheless, non-atherosclerotic disease of the carotid arteries may have profound, even devastating, neurologic consequences. Hence, this review will cover both common and uncommon forms of extracranial carotid artery pathologies in a pictorial format, in order to aid the diagnostician in identifying and differentiating such pathologies.

Objective Non-contrast MRI of the internal auditory canal (IAC) using high-resolution T2WI (T2 weighted image) has been proposed as the primary screening study in patients with sudden or asymmetric sensorineural hearing loss (ASNHL). However, there are concerns that non-contrast MRI may not detect labyrinthine pathology, specifically intralabyrinthine schwannomas (ILSs). The purpose of this study was to determine if non-contrast high-resolution T2WI alone are adequate to exclude these uncommon intralabyrinthine tumors. Methods 31 patients with ILSs and 36 patients without inner ear pathology that had dedicated MRI of the IAC performed with both non-contrast T2WI and post-contrast T1WI (T1 weighted image) were identified. Three board-certified neuroradiologists reviewed only the T2WI from these 67 cases. When an ILS was identified, its location and size were recorded. Sensitivity, specificity, and accuracy were calculated using the post-contrast T1WI as the “gold standard.” A consensus review of cases with discordant results was conducted. Results The sensitivity, specificity, and accuracy were 1.0, 1.0, and 1.0 for Observer 1; 0.84, 1.0, and 0.96 for Observer 2; 0.90, 1.0, and 0.98 for Observer 3. The 5 ILSs with discordant results were correctly identified upon consensus review. The median size of the ILSs was 4.4 mm (± 2.9 mm) and most (18/31) were intracochlear in location. Conclusion Non-contrast high-resolution T2WI alone can detect ILSs with 84–100% sensitivity, suggesting that gadolinium may be unnecessary to exclude ILSs on screening MRI. These findings have implications for reducing cost, time, and adverse events associated with gadolinium administration in patients presenting with sudden or ASNHL. Level of evidence 4

SUMMARY: The dentate nucleus is a cerebellar structure involved in voluntary motor function and cognition. There are relatively few entities that affect the dentate, and the clinical features of these conditions are often complex and nonspecific. Because these entities are rarely encountered, the formulation of a differential diagnosis can be difficult. Many of the conditions are reversible or treatable with early intervention. Therefore, it is important to recognize classic clinical presentations and their associated characteristic imaging findings. We provide a summary of entities that affect the dentate nucleus and a diagnostic workflow for approaching dentate nucleus imaging abnormalities.

Objective Cerebrospinal fluid-venous fistula is an uncommon cause of spontaneous spinal cerebrospinal fluid leak (SSCSFL). We aim to describe the clinical presentation, imaging evaluation, treatment and outcome of SSCSFL secondary to cerebrospinal fluid-venous fistula. Methods A retrospective review was undertaken of SSCSFL cases secondary to cerebrospinal fluid-venous fistula confirmed radiologically or intraoperatively, seen at our institution from January 1994 to March 2019. Cases with undetermined SSCSFL etiology, alternative etiology or unconfirmed fistula were excluded. Results Forty-four of 156 patients met the inclusion criteria (31 women, 13 men). Mean age of symptom onset was 52.6 years (SD 8.7, range 33–71 years). Headache was the presenting symptom in almost all, typically daily (69%), and most often in occipital/suboccipital regions. Headache character was most commonly pressure (38%), followed by throbbing/pulsing (21.4%). Orthostatic headache worsening occurred in 69% and an even greater percentage of patients (88%) reported Valsalva-induced headache exacerbation or precipitation. Headache occurred in isolation to Valsalva maneuvers in 12%. Of 37 patients with documented cerebrospinal fluid opening pressure, 13% were 2O; 84%, 7–20 cmH2O; and one, 25 cmH2O. Fistulas were almost exclusively thoracic (95.5%). Only one patient responded definitively to epidural blood patch (EBP). Forty-two patients underwent surgery. Most improved following surgery; 48.7% were completely headache free and 26.8% had at least 50% improvement. Conclusion In our series, cerebrospinal fluid-venous fistula was associated with a greater occurrence of Valsalva-induced headache exacerbation or precipitation than orthostatic headache and did not respond to EBP. Surgery provided significant improvement. Cerebrospinal fluid-venous fistula should be considered early in the differential diagnosis of Valsalva-induced (“cough”) headache.

BACKGROUND AND PURPOSE: There is a general assumption in the cerebrovascular literature that there is an association between carotid artery tortuosity and connective tissues disease; however, this has not been firmly established. The purpose of this study was to determine the prevalence of carotid artery tortuosity in patients with connective tissue diseases relative to matched controls. MATERIALS AND METHODS: Patients with previous CTA or MRA and a diagnosis of connective tissue diseases were identified and compared with a cohort of age-matched controls. Radiologists blinded to the diagnosis reviewed the images and evaluated the presence of carotid artery tortuosity (including loops, kinks, or coils). Continuous variables were compared using the Student t test, and categoric variables with χ(2) tests. RESULTS: One hundred forty-three patients with connective tissue disease and 143 controls were included in this study. Specific diagnoses included Marfan (n = 33), nonvascular Ehlers-Danlos (n = 36), Ehlers-Danlos vascular-type (n = 32), neurofibromatosis type 1 (n = 26), and Loeys-Dietz (n = 16) syndromes. The presence of carotid tortuosity was 44% in connective tissue disease and 16% in controls (P < .001). Of tortuosity manifestations, coils were most prevalent (23% versus 3%; P < .001). Among the various connective tissue diseases, the rates of any carotid tortuosity were 88% for Marfan syndrome, 63% for Loeys-Dietz syndrome, 42% for neurofibromatosis type 1, and 19% for both vascular- and nonvascular-type Ehlers-Danlos syndrome. The positive predictive value of the combination of aortic aneurysm and carotid tortuosity being associated with connective tissue disease was 95.4%. The specificity was 98.6%. CONCLUSIONS: Carotid artery tortuosity is highly associated with connective tissue diseases, particularly Marfan syndrome, Loeys-Dietz syndrome, and neurofibromatosis type 1. Such findings are relevant in risk assessment for vascular complications in connective tissue disease, endovascular treatment planning, and in understanding the pathomechanisms of vascular tortuosity in general.

Digital subtraction myelography is a valuable diagnostic technique to detect the exact location of CSF leaks in the spine to facilitate appropriate diagnosis and treatment of spontaneous spinal CSF leaks. Digital subtraction myelography is an excellent diagnostic tool for assessment of various types of CSF leaks, and lateral decubitus digital subtraction myelography is increasingly being used to diagnose CSF-venous fistulas. Lateral decubitus digital subtraction myelography differs from typical CT and fluoroscopy-guided myelograms in many ways, including equipment, supplies, and injection and image-acquisition techniques. Operators should be familiar with techniques, common pitfalls, and artifacts to improve diagnostic yield and prevent nondiagnostic examinations.

Study design Retrospective matched cohort study. Objective To determine if low-pressure lumbar provocation discography (PD) results in long-term accelerated disc degeneration, internal disc disruption, or disc herniation in patients with symptomatic low back pain (LBP). Summary of background data Study of subjects without clinically-significant LBP suggests that high-pressure PD may accelerate disc degeneration. Methods Consecutive patients with symptomatic LBP who underwent magnetic resonance imaging (MRI), PD, and repeat MRI more than 7 years later, but did not undergo subsequent spinal fusion surgery, were included. Punctured discs were matched (1:2 to 1:4) to corresponding discs in a control cohort by age, BMI, Pfirrmann score (±2), and presence of disc herniation; control cohort inclusion required MRIs for symptomatic LBP, separated by more than 7 years. The primary outcome of the study was a progression in Pfirrmann score category (I-II, III-IV, V). MRI disc-to-CSF T2 signal-intensity ratio, disc height, disc herniations, high intensity zones (HIZs), and Modic changes were assessed. Results Baseline and follow-up MRIs were available for 77 discs exposed to PD, and for 260 discs in the matched control cohort. There was no difference in the proportion of punctured discs that advanced in Pfirrmann score category in the PD group (17%, 95% CI 9-27%) compared with corresponding discs in the Control group (21%, 95% CI 17-27%), P = 0.3578, or in non-punctured discs in the PD group (35%, 95% CI 21-51%) compared with corresponding discs in the Control group (34%, 95% CI 27-42%), P = 0.1169. There were no differences in disc-to-CSF T2 signal-intensity ratio, presence of disc herniations, HIZs, or Modic changes following puncture in the PD versus matched cohort discs or in the non-punctured PD cohort discs versus corresponding control cohort discs (P > 0.05). Conclusion Patients with symptomatic LBP who underwent low-pressure PD, but who did not undergo a subsequent spinal fusion surgery, developed disc degeneration and new disc herniations at a similar rate to corresponding discs in matched control patients. Level of evidence 3.

BACKGROUND Positive-pressure myelogram (PPM) is an emerging radiologic study used to localize spinal dural defects. During PPM, cerebrospinal fluid pressure (CSFp) is increased by injecting saline with contrast into the cerebrospinal fluid. This has the potential to increase intracranial pressure and compromise cerebral perfusion. METHODS We performed a retrospective chart review and analysis of 11 patients. The aim was to describe the periprocedural anesthetic management of patients undergoing PPM. RESULTS All patients underwent PPM with general anesthesia and intra-arterial blood pressure and near-infrared spectroscopy monitoring of regional cerebral tissue oxygen saturation. Mean±SD maximum lumbar CSFp was 58±12 mm Hg. Upon intrathecal injection, mean systolic blood pressure increased from 115±21 to 142±32 mm Hg (P

Benign notochordal cell tumors (BNCTs) are considered to be benign intraosseous lesions of notochord origin; however, recent spine studies have suggested the possibility that some chordomas arise from BNCTs. Here, the authors describe two cases demonstrating histological features of BNCT and concomitant chordoma involving the clivus, which, to the best of the authors’ knowledge, have not been previously documented at this anatomical site.An 18-year-old female presented with an incidentally discovered clival mass. Magnetic resonance imaging revealed a 2.8-cm nonenhancing lesion in the upper clivus that was T2 hyperintense and T1 hypointense. She underwent an uneventful endoscopic transsphenoidal resection. Histologically, the tumor demonstrated areas of classic chordoma and a distinct intraosseous BNCT component. The patient completed adjuvant radiation therapy. Follow-up showed no recurrence at 18 months.A 39-year-old male presented with an incidentally discovered 2.8-cm clival lesion. The nonenhancing mass was T2 hyperintense and T1 hypointense. Surgical removal of the lesion was performed through an endoscopic transsphenoidal approach. Histological analysis revealed areas of BNCT with typical features of chordoma. Follow-up did not demonstrate recurrence at 4 years.These cases document histologically concomitant BNCT and chordoma involving the clivus, suggesting that the BNCT component may be a precursor of chordoma.

Bandscheibenerkrankungen konnen sich, uber das vertraute Bild des Bandscheibenvorfalls (Diskushernie) mit seinen typischen klinischen Merkmalen hinaus, durch ein breites Spektrum von Bildgebungsbefunden und klinischen Charakteristika manifestieren. Ziel dieses Reviews ist die bildliche Darstellung und Erorterung ungewohnlicher Manifestationen von Bandscheibenerkrankungen, denen der Radiologe begegnen kann: Bandscheibenvorfalle mit ungewohnlicher Lokalisation, Erkrankungen mit atypischen Bildgebungsbefunden und solche mit ungewohnlicher Pathophysiologie. Bei den vorgestellten Beispielen atypischer Bandscheibenvorfalle handelt es sich um Vorfalle in den dorsalen Epiduralraum sowie intradurale, symptomatische thorakale (einschlieslich solcher mit sehr grosen Kalzifikationen), extrem laterale (retroperitoneale), Fluor-18-Fluordesoxyglukose-avide, akute intravertebrale (Schmorl-Knoten) und massive lumbale Bandscheibenvorfalle. Als Beispiele mit atypischer Pathophysiologie werden Diskuszysten, fibrokartilaginose Ruckenmarksembolien, kalzifizierte Miniaturbandscheiben oder in Hohe eines Bandscheibenfachs auftretende Osteophytensporne als Ursache von Liquorlecks und intrakraniellem Unterdruck sowie die akute kalzifizierende Diszitis des Kindesalters vorgestellt. Die Grose der Bandscheiben ist bei diesem breiten Krankheitsspektrum sehr unterschiedlich und reicht von winzig (z. B. bei den verkalkten Miniaturbandscheiben als Ursache von Liquorlecks mit Austreten groser Liquormengen) bis zu extrem gros (z. B. bei den riesigen kalzifizierten, thorakalen intraduralen Bandscheibenvorfallen als Ursache von Myelopathien). Auch mit Blick auf den akuten Charakter der klinischen Symptomatik ist das vorgestellte Krankheitsspektrum breit: Es reicht von hyperakuten fibrokartilaginosen Embolien als Ursache von Ruckenmarksinfarkten uber akute Schmorl-Knoten bis hin zu chronischen intraduralen Herniationen. Zudem sind die typischen klinischen Verlaufe sehr verschieden, angefangen von den meist verheerenden Folgen eines Ruckenmarksinfarkts aufgrund einer fibrokartilaginosen Embolie bis zum gewohnlich spontanen Abklingen der akuten kalzifizierenden Diszitis des Kindesalters. Bei manchen Krankheiten sind grundliche differenzialdiagnostische Uberlegungen erforderlich, wahrend andere anhand der Bildgebungsbefunde relativ leicht zu diagnostizieren sind. Die pathophysiologischen Zusammenhange sind in manchen Fallen wohlbekannt, in anderen dagegen weitgehend ungeklart. Der Radiologe muss dieses breite Spektrum ungewohnlicher Bandscheibenerkrankungen kennen, um richtige radiologische Diagnosen stellen zu konnen.

The cervical spine in Chiari I patient with syringomyelia has significantly different anteroposterior diameters than it does in Chiari I patients without syringomyelia. We tested the hypothesis that patients with idiopathic syringomyelia (IS) also have abnormal cervical spinal canal diameters. The finding in both groups may relate to the pathogenesis of syringomyelia. Local institutional review boards approved this retrospective study. Patients with IS were compared to age-matched controls with normal sagittal spine MR. All subjects had T1-weighted spin-echo (500/20) and T2-weighted fast spin-echo (2000/90) sagittal cervical spine images at 1.5 T. Readers blinded to demographic data and study hypothesis measured anteroposterior diameters at each cervical level. The spinal canal diameters were compared with a Mann-Whitney U test. The overall difference was assessed with a Friedman test. Seventeen subjects were read by two reviewers to assess inter-rater reliability. Fifty IS patients with 50 age-matched controls were studied. IS subjects had one or more syrinxes varying from 1 to 19 spinal segments. Spinal canal diameters narrowed from C1 to C3 and then enlarged from C5 to C7 in both groups. Diameters from C2 to C4 were narrower in the IS group (p

Beyond the familiar disk herniations with typical clinical features, intervertebral disk pathologic conditions can have a wide spectrum of imaging and clinical manifestations. The goal of this review is to illustrate and discuss unusual manifestations of intervertebral disk pathologic conditions that radiologists may encounter, including disk herniations in unusual locations, those with atypical imaging features, and those with uncommon pathophysiologic findings. Examples of atypical disk herniations presented include dorsal epidural, intradural, symptomatic thoracic (including giant calcified), extreme lateral (retroperitoneal), fluorine 18 fluorodeoxyglucose-avid, acute intravertebral (Schmorl node), and massive lumbar disk herniations. Examples of atypical pathophysiologic conditions covered are discal cysts, fibrocartilaginous emboli to the spinal cord, tiny calcified disks or disk-level spiculated osteophytes causing spinal cerebrospinal fluid (CSF) leak and intracranial hypotension, and pediatric acute calcific discitis. This broad gamut of disease includes a variety of sizes of disk pathologic conditions, from the tiny (eg, the minuscule calcified disks causing high-flow CSF leaks) to the extremely large (eg, giant calcified thoracic intradural disk herniations causing myelopathy). A spectrum of clinical acuity is represented, from hyperacute fibrocartilaginous emboli causing spinal cord infarct, to acute Schmorl nodes, to chronic intradural herniations. The entities included are characterized by a range of clinical courses, from the typically devastating cord infarct caused by fibrocartilaginous emboli, to the usually spontaneously resolving pediatric acute calcific discitis. Several conditions have important differential diagnostic considerations, and others have relatively diagnostic imaging findings. The pathophysiologic findings are well understood for some of these entities and poorly defined for others. Radiologists' knowledge of this broad scope of unusual disk disease is critical for accurate radiologic diagnoses. Online supplemental material is available for this article. (©)RSNA, 2016.

We present a rare case of intracranial involvement in hemophagocytic lymphohistiocytosis (HLH) in an adult patient. MRI features in HLH may mimic those of other neoplastic, infectious, or inflammatory disorders. Key imaging findings correlate to central nervous system inflammation and include diffuse leptomeningeal enhancement, white matter changes with variable enhancement, hemorrhage, and restricted diffusion. Recognition of the imaging characteristic in correlation with clinical presentation, laboratory values, and biopsy findings is essential for making a correct diagnosis.

Vertebral compression fractures are very common, especially in the elderly. Benign osteoporotic and malignant vertebral compression fractures have extremely different management and prognostic implications. Although there is an overlap in appearances, characteristic imaging features can aid in the distinction between these 2 types of compression fractures. The aim of this review is to characterize the imaging features of benign and malignant vertebral compression fractures seen with CT, PET, SPECT, and MR imaging.