Magnetic resonance imaging findings of redundant nerve roots of the cauda equina

BACKGROUND Redundant nerve roots(RNRs)of the cauda equina are often a natural evolutionary part of lumbar spinal canal stenosis secondary to degenerative processes characterized by elongated,enlarged,and tortuous nerve roots in the superior and/or inferior of the stenotic segment.Although magnetic resonance imaging(MRI)findings have been defined more frequently in recent years,this condition has been relatively under-recognized in radiological practice.In this study,lumbar MRI findings of RNRs of the cauda equina were evaluated in spinal stenosis patients.AIM To evaluate RNRs of the cauda equina in spinal stenosis patients.METHODS One-hundred and thirty-one patients who underwent lumbar MRI and were found to have spinal stenosis between March 2010 and February 2019 were included in the study.On axial T2-weighted images(T2WI),the cross-sectional area(CSA)of the dural sac was measured at L2-3,L3-4,L4-5,and L5-S1 levels in the axial plane.CSA levels below 100 mm^2 were considered stenosis.Elongation,expansion,and tortuosity in cauda equina fibers in the superior and/or inferior of the stenotic segment were evaluated as RNRs.The patients were divided into two groups:Those with RNRs and those without RNRs.The CSA cut-off value resulting in RNRs of cauda equina was calculated.Relative length(RL)of RNRs was calculated by dividing the length of RNRs at mid-sagittal T2WI by the height of the vertebral body superior to the stenosis level.The associations of CSA leading to RNRs with RL,disc herniation type,and spondylolisthesis were evaluated.RESULTS Fifty-five patients(42%)with spinal stenosis had RNRs of the cauda equina.The average CSA was 40.99±12.76 mm^2 in patients with RNRs of the cauda equina and 66.83±19.32 mm^2 in patients without RNRs.A significant difference was found between the two groups for CSA values(P<0.001).Using a cut-off value of 55.22 mm^2 for RNRs of the cauda equina,sensitivity,specificity,positive predictive value(PPV),and negative predictive value(NPV)values of 96.4%,96.1%,89.4%,and 98.7%were obtained,respectively.RL was 3.39±1.31(range:0.93-6.01).When the extension of RNRs into the superior and/or inferior of the spinal canal stenosis level was evaluated,it was superior in 54.5%,both superior and inferior in 32.8%,and inferior in 12.7%.At stenosis levels leading to RNRs of the cauda equina,29 disc herniations with soft margins and 26 with sharp margins were detected.Disc herniation type and spondylolisthesis had no significant relationship with RL or CSA of the dural sac with stenotic levels(P>0.05).As the CSA of the dural sac decreased,the incidence of RNRs observed at the superior of the stenosis level increased(P<0.001).CONCLUSION RNRs of the cauda equina are frequently observed in patients with spinal stenosis.When the CSA of the dural sac is<55 mm^2,lumbar MRIs should be carefully examined for this condition.

Advanced magnetic resonance imaging findings in salivary gland tumors

Salivary gland tumors(SGTs)make up a small portion(approximately 5%)of all head and neck tumors.Most of them are located in the parotid glands,while they are less frequently located in the submandibular glands,minor salivary glands or sublingual gland.The incidence of malignant or benign tumors(BTs)in the salivary glands varies according to the salivary gland from which they originate.While most of those detected in the parotid gland tend to be benign,the incidence of malignancy increases in other glands.The use of magnetic resonance imaging(MRI)in the diagnosis of SGTs is increasing every day.While conventional sequences provide sufficient data on the presence,localization,extent and number of the tumor,they are insufficient for tumor specification.With the widespread use of advanced techniques such as diffusion-weighted imaging,semiquantitative and quantitative perfusion MRI,studies and data have been published on the differentiation of malignant or BTs and the specificity of their subtypes.With diffusion MRI,differentiation can be made by utilizing the cellularity and microstructural properties of tumors.For example,SGTs such as high cellular Warthin’s tumor(WT)or lymphoma on diffusion MRI have been reported to have significantly lower apparent diffusion values than other tumors.Contrast agent uptake and wash-out levels of tumors can be detected with semiquantitative perfusion MRI.For example,it is reported that almost all of the pleomorphic adenomas show an increasing enhancement time intensity curve and do not wash-out.On quantitative perfusion MRI studies using perfusion parameters such as Ktrans,Kep,and Ve,it is reported that WTs can show higher Kep and lower Ve values than other tumors.In this study,the contribution of advanced MRI to the diagnosis and differential diagnosis of SGTs will be reviewed.

Diagnostic efficacy of diffusion-weighted imaging and semiquantitative and quantitative dynamic contrast-enhanced magnetic resonance imaging in salivary gland tumors

BACKGROUND Increased use of functional magnetic resonance imaging(MRI)methods such as diffusion-weighted imaging(DWI)and dynamic contrast-enhanced(DCE)MRI consisting of sequential contrast series,allows us to obtain more information on the microstructure,cellularity,interstitial distance,and vascularity of tumors,which has increased the discrimination power for benign and malignant salivary gland tumors(SGTs).In the last few years,quantitative DCE MRI data containing T1 perfusion parameters(K_(trans),K_(ep)and V_(e)),were reported to contribute to the differentiation of benign or malignant subtypes in SGTs.AIM To evaluate the diagnostic efficacy of DWI and semiquantitative and quantitative perfusion MRI parameters in SGTs.METHODS Diffusion MRI[apparent diffusion coefficient(ADC)value]with a 1.5 T MR machine,semiquantitative perfusion MRI[time intensity curve(TIC)pattern],and quantitative perfusion MRI examinations(K_(trans),K_(ep)and V_(e))of 73 tumors in 67 patients with histopathological diagnosis performed from 2017 to 2021 were retrospectively evaluated.In the ADC value and semiquantitative perfusion MRI measurements,cystic components of the tumors were not considered,and the region of interest(ROI)was manually placed through the widest axial section of the tumor.TIC patterns were divided into four groups:Type A=T_(peak)>120 s;type B=T_(peak)≤120 s,washout ratio(WR)≥30%;type C=T_(peak)≤120 s,WR<30%;and type D=flat TIC.For the quantitative perfusion MRI analysis,a 3D ROI was placed in the largest solid component of the tumor,and the K_(trans),K_(ep)and V_(e)values were automatically generated.RESULTS The majority of SGTs were located in the parotid glands(86.3%).Of all the SGTs,68.5%were benign and 31.5%were malignant.Significant differences were found for ADC values among pleomorphic adenomas(PMAs),Warthin's tumors(WTs),and malignant tumors(MTs)(P<0.001).PMAs had type A and WTs had type B TIC pattern while the vast majority of MTs and other benign tumors(OBTs)(54.5%and 45.5%,respectively)displayed type C TIC pattern.PMAs showed no washout,while the highest mean WR was observed in WTs(59%±11%).K_(trans)values of PMAs,WTs,OBTs,and MTs were not significantly different.K_(ep)values of PMAs and WTs were significantly different from those of OBTs and MTs.Mean V_(e)value of WTs was significantly different from those of PMAs,OBTs,and MTs(P<0.001).CONCLUSION The use of quantitative DCE parameters along with diffusion MRI and semiquantitative contrastenhanced MRI in SGTs could improve the diagnostic accuracy.