Analysis of radiological parameters associated with decreased fractional anisotropy values on diffusion tensor imaging in patients with lumbar spinal stenosis

Longitudinal DTI analysis of microstructural changes in lumbar nerve roots following Interspinous process device placement

Diffusion tensor imaging (DTI) and its parameters such as fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (AD), radial diffusivity (RD) are increasingly being used to assess peripheral nerve integrity alongside nerve conduction studies. This pilot study aims to compare DTI values of lumbar spinal nerve roots before (T0) and after (T1) treatment with an interspinous process device (IPD). Seven patients (5 females, 2 males; mean age: 68) suffering from neurogenic claudication and lumbar spinal canal and foraminal stenosis were evaluated. Visual Analog Scale (VAS) for perceived pain, Oswestry Disability Index (ODI), and DTI parameters were assessed between T0 and T1. No significant difference in FA was found in treated roots, while MD (p = 0.0015), RD (p = 0.0032), and AD (p = 0.0221) were significantly altered. At untreated levels, all DTI parameters showed highly significant differences (p < 0.0001) between T0 and T1. In treated roots, FA values significantly increased in the intraforaminal segment(p = 0.0229), while MD(p = 0.0124), AD(p = 0.0128), and RD (p = 0.0143) values decreased in the pre-foraminal segment. In untreated roots, FA significantly increased in pre(p = 0.0039)and intraforaminal(p = 0.0003) segments, and MD, AD, and RD decreased in all segments (p < 0.0001). VAS (p < 0.0001) also decreased between T0 and T1. This pilot study aims to clarify the biomechanical impact of interspinous spacers through microstructural analysis of both treated and adjacent untreated nerve roots. To our knowledge, no studies have examined the short- to medium-term changes in DTI values of lumbar nerve roots before and after IPD placement, or compared changes between treated and untreated roots.

Clinical Value and Reliability of Quantitative Assessments of Lumbosacral Nerve Root Using Diffusion Tensor and Diffusion Weighted MR Imaging: A Systematic Review

BACKGROUND

Lumbosacral radicular pain diagnosis remains challenging. Diffusion tensor imaging (DTI) and diffusion weighted imaging (DWI) have potential to quantitatively evaluate symptomatic nerve root, which may facilitate diagnosis.

PURPOSE

To determine the ability of DTI and DWI metrics, namely fractional anisotropy (FA) and apparent diffusion coefficient (ADC), to discriminate between healthy and symptomatic lumbosacral nerve roots, to evaluate the association between FA and ADC values and patient symptoms, and to determine FA and ADC reliability.

STUDY TYPE

Systematic review.

SUBJECTS

Eight hundred twelve patients with radicular pain with or without radiculopathy caused by musculoskeletal-related compression or inflammation of a single, unilateral lumbosacral nerve root and 244 healthy controls from 29 studies.

FIELD STRENGTH/SEQUENCE

Diffusion weighted echo planar imaging sequence at 1.5 T or 3 T.

ASSESSMENT

An extensive systematic review of the literature was conducted in Embase, Scopus, and Medline databases. FA and ADC values in symptomatic and contralateral lumbosacral nerve roots were extracted and summarized, together with intra- and inter-rater agreements. Where available, associations between DWI or DTI parameters and patient symptoms or symptom duration were extracted.

STATISTICAL TESTS

The main results of the included studies are summarized. No additional statistical analyses were performed.

RESULTS

The DTI studies systematically found significant differences in FA values between the symptomatic and contralateral lumbosacral nerve root of patients suffering from radicular pain with or without radiculopathy. In contrast, identification of the symptomatic nerve root with ADC values was inconsistent for both DTI and DWI studies. FA values were moderately to strongly correlated with several symptoms (eg, disability, nerve dysfunction, and symptom duration). The inter- and intra-rater reliability of DTI parameters were moderate to excellent. The methodological quality of included studies was very heterogeneous.

DATA CONCLUSION

This systematic review showed that DTI was a reliable and discriminative imaging technique for the assessment of symptomatic lumbosacral nerve root, which more consistently identified the symptomatic nerve root than DWI. Further studies of high quality are needed to confirm these results.

EVIDENCE LEVEL

N/A TECHNICAL EFFICACY: Stage 2.

Microstructural Alteration of Lumbosacral Nerve Roots in Chronic Inflammatory Demyelinating Polyradiculoneuropathy: Insights From DTI and Correlations with Electrophysiological Parameters

RATIONALE AND OBJECTIVES

To detect the diffusion characteristics of lumbosacral nerve roots in patients with chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) and further to explore their correlations with electrophysiological parameters of lower extremity nerves.

MATERIALS AND METHODS

Eighteen CIDP patients and 18 age and sex-matched healthy volunteers were enrolled in this study from August 2019 to August 2020. Axial diffusion tensor imaging (DTI) of lumbosacral plexus was performed in all subjects and fractional anisotropy (FA), axial diffusivity (AD), radial diffusivity (RD), and mean diffusivity (MD) of lumbosacral nerve roots were measured. Two-sample t test or Mann-Whitney U test was used to compare the difference of DTI parameters between two groups. Receiver operating characteristic curves were plotted to determine the diagnostic accuracy. All patients also underwent nerve conduction studies. Correlations between DTI parameters of lumbosacral nerve roots and electrophysiological parameters were analyzed with Pearson or Spearman coefficients.

RESULTS

CIDP patients showed significantly lower FA as well as higher AD, RD, and MD values of lumbosacral nerve roots (FA:0.24±0.054, 0.32±0.044; AD:2.31±0.256, 2.11±0.230 (×10^-3mm²/s); RD:1.28±0.189, 1.13±0.106 (×10^-3mm²/s); MD:1.68±0.268, 1.45±0.186 (×10^-3mm²/s) in CIDP and control group, respectively, all p < 0.05). Receiver operating characteristic analysis showed among all DTI parameters, FA had the best diagnostic accuracy with an area under the curve of 0.914 and optimal cut-off value of 0.27. FA showed a positive correlation while RD showed a negative correlation with a conduction velocity of tibial and common peroneal nerves. RD also correlated positively with F-wave minimal latency of tibial nerves.

CONCLUSION

DTI can be used to assess the microstructure alterations of lumbosacral nerve roots in CIDP patients. FA and RD may serve as potential markers reflecting the conduction function of tibial and common peroneal nerves.

Diffusion tensor imaging with fiber tracking provides a valuable quantitative and clinical evaluation for compressed lumbosacral nerve roots: a systematic review and meta-analysis

PURPOSE

This study aimed to investigate the diagnostic value of fractional anisotropy (FA) and apparent diffusion coefficient (ADC) of the diffusion tensor imaging (DTI) with fiber tracking in patients with compressed lumbosacral nerve roots.

METHODS

A systematic literature search of databases (PubMed, Embase, Cochrane Library, and Web of Science) was carried out. FA values and ADC values were compared between compressed nerve roots and healthy controls. Pooled and subgroup analyses were performed using fixed or random-effect models based on I² heterogeneity.

RESULTS

A total of 262 patients from ten studies with 285 compressed lumbosacral nerve roots and 285 contralateral normal nerve roots were included in the meta-analysis. It was showed in pooled results that FA value was significantly reduced (SMD  - 3.03, 95% CI [ - 3.75 to  - 2.31], P < 0.001) and ADC value was significantly increased (SMD 2.07, 95% CI [0.92 to 3.22], P < 0.001) in the compressed nerve roots, compared with contralateral normal nerve roots. Subgroup analysis comparing the FA values and ADC values in different nerve root ranges (L2-S1, L4-S1, L5-S1, L5, S1) revealed the different ranges of nerve roots were possible sources of heterogeneity.

CONCLUSIONS

This study showed that FA value reduction and ADC value increase were valuable indicators of compressed lumbosacral nerve roots. These changes may be related to the neurological symptoms of patients. DTI with fiber tracking can directly visualize and accurately locate the compression zone of nerve roots to help make surgical treatment plans, is more advanced than conventional MRI.

The evaluation on neural status of cervical spinal cord in normal and Hirayama disease using diffusion tensor imaging

PURPOSE

To explore the changes in diffusion tensor imaging (DTI) parameters in cervical spinal cord in Hirayama disease (HD) patients and healthy volunteers and to compare these parameters between cervical flexion and neutral positions in HD patients.

METHODS

Seventeen male patients with HD and eleven healthy young males were included to receive DTI scans in cervical flexion and neutral positions. The FA and ADC values of different levels were measured based on the region of interest drawn on the mid-sagittal plane. The dynamic compressed level's parameters were defined as the lowest and the second lowest FA and the highest and the second highest ADC, respectively. The clinical assessment of patients was obtained using their disabilities of the arm, shoulder and hand (DASH) scores.

RESULTS

For the HD patients, the FA values in the cervical flexion position were lower and the ADC values were much higher than those in the cervical neutral position. Compared with the controls, the ADC values were significantly higher in the lower levels (C5/6-C7/T1) and the FA values obviously lower at C7/T1 in HD patients in cervical neutral position. The FA and ADC values of the dynamic compressed level in HD patients deviated significantly from the average of the lower levels in controls. Both the FA and ADC values of the dynamic compressed level correlated with the DASH scores (FA, R² = 0.520, P = 0.001; ADC, R² = 0.421, P = 0.005).

CONCLUSIONS

DTI parameters can support a hypothesis of dynamic cervical flexion compression and noninvasively reveal the neural status of HD patients. These slides can be retrieved under Electronic Supplementary Material.