Amrami, Kimberly K.

Background: The purpose of this study was to quantify the in vivo displacement of bilateral distal radioulnar joints (DRUJs) in resisted pronosupination. We hypothesize that this will demonstrate no appreciable difference between the left and right DRUJ, thus validating the concept of using the uninjured wrist as a control for physical examination as well as dynamic imaging studies. Methods: Thirty-two participants without a history of wrist pathology underwent a dynamic computed tomography (CT) protocol evaluating bilateral forearm rotation in neutral forearm rotation, 60° pronation, and 60° supination, including maximal isometric muscle loading. The DRUJ alignment, specifically the absolute degree and direction of subluxation of the ulna relative to the sigmoid notch, was then assessed using a modification of the radioulnar line method. Results: There was no significant difference in the mean displacement when comparing the right and left sides in neutral, pronation, or supination. The mean displacement was also compared between male and female patients, and there was no statistically significant difference in absolute displacement in neutral (male 0.99 mm vs female 1.38 mm) or supination (male −0.57 mm vs female −0.23 mm). However, the difference in pronation was statistically significant (male 2.69 mm vs female 3.26 mm). Of the 192 sequences, the measurements of displacement of the authors were within 1 mm 86% of the time (166 of 192). Conclusions: Dynamic CT of bilateral DRUJs in resisted pronation, supination, and neutral demonstrated symmetry between the right and left DRUJ, supporting the concept of using the contralateral side as a control to identify instability in an injured wrist.

See article on pages 339‐344 in this issue

OBJECTIVE Neurolymphomatosis (NL) is a rare manifestation of lymphoma confined to the peripheral nervous system that is poorly understood. It can be found in the cauda equina, but extraspinal disease can be underappreciated. The authors describe how extraspinal NL progresses to the cauda equina by perineural spread and the implications of this on timely and safe diagnostic options. METHODS The authors used the Mayo Clinic medical records database to find cases of cauda equina NL with sufficient imaging to characterize the lumbosacral plexus diagnosed from tissue biopsy. Demographics (sex, age), clinical data (initial symptoms, cerebrospinal fluid, evidence of CNS involvement, biopsy location, primary or secondary disease), and imaging findings were reviewed. RESULTS Ten patients met inclusion and exclusion criteria, and only 2 of 10 patients presented with cauda equina symptoms at the time of biopsy, with 1 patient undergoing a cauda equina biopsy. Eight patients were diagnosed with diffuse large B-cell lymphoma, 1 with low-grade B-cell lymphoma, and 1 with mantle cell lymphoma. Isolated spinal nerve involvement was identified in 5 of 10 cases, providing compelling evidence regarding the pathophysiology of NL. The conus medullaris was not radiologically involved in any case. Lumbosacral plexus MRI was able to identify extraspinal disease and offered diagnostically useful biopsy targets. FDG PET/CT was relatively insensitive for detecting disease in the cauda equina but was helpful in identifying extraspinal NL. CONCLUSIONS The authors propose that perineural spread of extraspinal NL to infiltrate the cauda equina occurs in two phases. 1) There is proximal and distal spread along a peripheral nerve, with eventual spread to anatomically connected nerves via junction and branch points. 2) The tumor cells enter the spinal canal through corresponding neural foramina and propagate along the spinal nerves composing the cauda equina. To diffusely infiltrate the cauda equina, a third phase occurs in which tumor cells can spread circumdurally to the opposite side of the spinal canal and enter contralateral nerve roots extending proximally and distally. This spread of disease can lead to diffuse bilateral spinal nerve disease without diffuse leptomeningeal spread. Recognition of this phasic mechanism can lead to identification of safer extraspinal biopsy targets that could allow for greater functional recovery after appropriate treatment.

BACKGROUND The advancement of high-resolution imaging and increased clinical experience have led to an increased understanding of the formation and treatment of intraneural ganglion cysts. Nearly all intraneural ganglion cysts in the common peroneal nerve have been reported to arise from a joint connection to the superior tibiofibular joint. The authors have identified four cases of intraneural ganglion cysts arising from the knee joint itself; however, none of these reported cases were well described, documented, or illustrated with high-resolution imaging. OBSERVATIONS Here the authors present the case of an intraneural ganglion cyst arising from the knee joint and causing intermittent weakness and pain. The articular branch to the knee joint was clearly demonstrated on high-resolution magnetic resonance imaging and confirmed at surgical exploration. The patient was treated with articular branch ligation and has had complete resolution of his symptoms without recurrence of the cyst on follow-up imaging. LESSONS This case adds to the mounting evidence that intraneural cyst pathology is dependent on a connection to a synovial joint as stated in the unifying theory of intraneural cyst development.

PurposeA 7T magnetic resonance thermometry (MRT) technique was developed to validate the conversion factor between the system‐measured transmitted radiofrequency (RF) power into a home‐built RF wrist coil with the system‐predicted SAR value. The conversion factor for a new RF coil developed for ultra high magnetic field MRI systems is used to ensure that regulatory limits on RF energy deposition in tissue, specifically the local 10g‐averaged specific absorption rate (SAR10g), are not exceeded. MRT can be used to validate this factor by ensuring that MRT‐measured SAR values do not exceed those predicted by the system.MethodsA 14‐cm diameter high‐pass birdcage RF coil was built to image the wrist at 7T. A high spatial and temporal resolution dual‐echo gradient echo MRT technique, incorporating quasi‐simultaneous RF‐induced heating and temperature change measurements using the proton resonance frequency method, was developed. The technique allowed for high‐temperature resolution measurements (~±0.1°C) to be performed every 20 s over a 4‐min heating period, with high spatial resolution (2.56 mm3 voxel size) and avoiding phase discontinuities arising from severe magnetic susceptibility‐induced B0 inhomogeneities. Magnetic resonance thermometry was performed on a phantom made from polyvinylpyrrolidone to mimic the dielectric properties of muscle tissue at 297.2 MHz. Temperature changes measured with MRT and four fiber optic temperature sensors embedded in the phantom were compared. Electromagnetic simulations of the coil and phantom were developed and validated via comparison of simulated and measured B1+ maps in the phantom. The position of maximum SAR within the coil was determined from simulations, and MRT was performed within a wrist‐sized piece of meat positioned at that SAR hotspot location. MRT‐measured and system‐predicted SAR values for the phantom and meat were compared.ResultsTemperature change measurements from MRT matched closely to those from the fiber optic temperature sensors. The simulations were validated via close correlation between the simulated and MRT‐measured B1+ and SAR maps. Using a coil conversion factor of 2 kg−1, MRT‐measured point‐SAR values did not exceed the system‐predicted SAR10g in either the uniform phantom or in the piece of meat mimicking the wrist located at the SAR hotspot location.ConclusionsA highly accurate MRT technique with high spatial and temporal resolution was developed. This technique can be used to ensure that system‐predicted SAR values are not exceeded in practice, thereby providing independent validation of SAR levels delivered by a newly built RF wrist coil. The MRT technique is readily generalizable to perform safety evaluations for other RF coils at 7T.

Objective: Determine the radiological prevalence of popliteal artery entrapment (PAE) in subjects with anterior leg compartment chronic exertional compartment syndrome (CECS). Design: Retrospective review. Setting: Tertiary care center. Patients: Of 71 patients diagnosed with anterior leg compartment CECS using an in-scanner exercise-based magnetic resonance imaging (MRI), 64 also completed Fast Imaging Employing Steady-State Acquisition (FIESTA) imaging. Interventions: Electronic health records of patients diagnosed with anterior leg compartment CECS using an in-scanner exercise-based MRI between 2009 and 2018 were reviewed. Main Outcome Measures: Demographics, symptom laterality, and results of vascular work-up. Results: Magnetic resonance imaging was positive for PAE in 33 of 64 (51.6%). Vascular evaluation was performed in 30 of 33 (90.9%). Of these 30, ankle-brachial indices (ABIs) with PAE maneuvers were performed in 29 (96.7%) and positive in 25 (86.2%). Pre-exercise and post-exercise ABIs were performed in 29 (96.7%) and abnormal in 20 (69.0%). Thirteen arterial duplex ultrasounds were performed; 10 were consistent with PAE (76.9%). An MR angiogram was performed in 8 (26.7%) and consistent with PAE in all. One computed tomography angiogram (3.3%) was completed and was normal. Overall, one or more tests were positive for PAE in all 30 with vascular evaluation. Conclusions: The radiological prevalence of PAE and anterior leg CECS was 51.6%. All subjects with vascular studies (90.9%) had one or more tests confirming radiological PAE. These findings suggest that the coexistence of PAE and CECS is common, and the PAE protocol used has a high correlation with vascular studies.

Abstract Objectives: The objective of the study is to distinguish the mechanisms of disease for chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) and multifocal motor neuropathy (MMN), which we believe to be fundamentally different. However, distinguishing the mechanisms is more difficult when the presentation of CIDP is motor-predominant, focal, or asymmetric. Methods: We describe 3 focal, motor-predominant, representative cases that could be interpreted on clinical and/or electrophysiological grounds as either MMN or focal CIDP, and present pathological findings. Results: We highlight pathological differences in these cases, and provide an argument that CIDP and MMN are distinct entities with different pathophysiological mechanisms—chronic demyelination for CIDP, and an immune-mediated attack on paranodal motor axons for MMN. Conclusions: Based on clinical evaluation, electrophysiology, and nerve biopsy pathology, we can divide the conditions into inflammatory demyelinating neuropathy (focal CIDP) versus chronic axonal neuropathy (MMN). The divergent pathological findings provide further evidence that CIDP and MMN are fundamentally different disorders.

AbstractBackgroundLipomatosis of nerve (LN) is a complex peripheral nerve disorder characterized by fibrofatty nerve enlargement. MRI of this pathology is pathognomonic and obviates a diagnostic biopsy. Mutation in PIK3CA has been associated with LN cases with nerve‐territory overgrowth which may occur in some cases. We evaluate an association of LN of the sciatic nerve and early‐onset colonic diverticular disease and discuss the potential pathogenesis.MethodsOur institutional database was searched for LN cases. Available information of identified cases was reviewed, and cases with a confirmed diagnosis of LN affecting the lumbosacral plexus and/or sciatic nerve; available MRI of the affected nerve(s); and diverticular disease occurring in the area supplied by the nerve(s) affected by LN were further analyzed. PIK3CA mutation testing was performed on available tissue samples.ResultsWe identified 10 LN cases of lumbosacral plexus and/or sciatic nerve. Of these, three fulfilled our inclusion criteria. All three patients had concomitant colonic diverticular disease, diagnosed at a relatively young age. MRI studies of these cases showed LN involvement of the sacral nerves innervating the sigmoid colon. All three also had abnormal diagnostic workup including various GI tests and evidence of associated nerve‐territory overgrowth. Colonic tissue samples for PIK3CA mutation were negative.ConclusionWhile the pathogenesis of the colonic diverticular disease is increasingly recognized as being multifactorial, our observations are consistent with the potential role of autonomic nervous system dysfunction affecting either the pelvic floor musculature, or the colon itself (or both) in a subset of patients with early‐onset diverticular disease.

10601 Background: Brachial plexopathy is a well-recognized complication of breast cancer, most attributed to late effects of radiation. However, direct involvement of brachial plexus by recurrent breast cancer occurs. Misdiagnoses may lead to inappropriate attribution of the plexopathy to radiation, and therefore inappropriate therapy. Methods: We report fourteen cases of brachial plexopathy secondary to breast cancer diagnosed at the Mayo Clinic-Rochester from 2003 to 2005. Results: Thirteen of fourteen primary tumors and 12/14 recurrences were ER/PR positive. Only 1/14 patient had Her 2 neu overexpression. The median time from the original breast cancer diagnosis to first brachial plexus symptom was 14 years. The median time from the development of symptoms to diagnosis was 8 months with the range being 1 month to 8 years. MRI revealed a distinct mass in 3/13 patients, plexus thickening in 5/13, and was normal in 5/13. Only 5/13 original MRI interpretations suggested tumor. In four patients that the 1.5 T MRI was either interpreted as normal or unlikely cancer the 3 Tesla MRI revealed abnormal uptake suggestive of malignancy. PET scan suggested malignancy in 3/6 patients. Two of these cases had other metastatic disease. In the other three cases that PET scans were done the uptake was mild, suggesting inflammation rather than malignancy. Reinterpretations of the PET scan and MRI in combination by an experienced musculoskeletal radiologist was highly suggestive of malignancy in all cases. Definitive diagnosis was eventually obtained by biopsy of the brachial plexus (7/14) or another site of metastasis in (4/14). Conclusions: The often slowly progressive nature of hormonally driven breast cancer can mimic radiation induced brachial plexopathy. In the cases reviewed, PET was not reliable in differentiating inflammation from tumor. MRI findings are nonspecific and higher resolution 3T MRI may be needed to detect an abnormality. Interpretation of MRI and PET together is useful. Patients with a history of breast cancer, and brachial plexus symptoms should be carefully evaluated with consideration for recurrent disease as a cause. Biopsy of the brachial plexus can be done safely and has an important role in diagnosis. No significant financial relationships to disclose.