Biological laterality and peripheral nerve DTI metrics

Neurophysiological indices for split phenomena: correlation with age and sex and potential implications in amyotrophic lateral sclerosis

Background

Split phenomena (SP) are characterized by patterns of differential muscle wasting and atrophy, which are highly prevalent in amyotrophic lateral sclerosis (ALS) patients. Several neurophysiological indicators, including the split-hand index (SHI), split-leg index (SLI), and split-elbow index (SEI), have been proposed to assess SP. Nevertheless, their cutoff values and the impact of age and sex on these measures remain unclear.

Methods

We prospectively collected neurophysiological data from 300 healthy adult subjects. The following indices were measured from compound muscle action potentials (CMAPs): SHI [abductor pollicis brevis (APBcmap) x first dorsal interosseous (FDI)cmap/adductor digiti minimi (ADMcmap)], SEI (BICEPScmap/TRICEPScmap), SLI (extensor digit brevis (EDB)cmap/abductor Hallucis (AH)cmap), and the neurophysiological ratios APBcmap /ADMcmap and FDIcmap/ADMcmap. Multiple linear regression analysis was used to investigate the association between age, sex, CMAPs, and neurophysiological indicators.

Results

The median SHI was 10.4, with a median APBcmap/ADMcmap ratio of 0.9 and a median FDIcmap/ADMcmap ratio of 1.2. The median SEI was 1.6 (IQR:1.1-2.4) and the median SLI was 0.7 (IQR:0.5-1.0). Negative associations were observed between age, most of the CMAPs, and all the neurophysiological indices, except for SLI. The male subjects exhibited significantly higher CMAP values for the first dorsal interosseous (FDI), biceps, and SHI compared to the female participants.

Conclusion

Our findings highlight the importance of age- and sex-adjusted normative data for SP indices, which could enhance their diagnostic accuracy and clinical utility in patients with ALS. The SL index appears to be the most reliable indicator, as it showed no significant association with age or sex.

Application of magnetic resonance neuroimaging in determining the relationship between tumors and peripheral nerves

BACKGROUND

Magnetic resonance imaging (MRI) is commonly used to analyze the relationship between tumors and nerves before surgery. However, the application value of diffusion tensor imaging (DTI), diffusion weighted imaging (DWI), and post-processing techniques needs further elucidation.

PURPOSE

To assess the value of DTI, DWI, and various post-processing techniques in determining the relationship between tumors and nerves.

MATERIAL AND METHODS

The participants were 42 patients diagnosed with peripheral nerve-related tumors and 20 healthy controls. DTI and DWI scans were performed before surgery, and then DTI unidirectional maximum intensity projection (MIP) post-processing and DWI subtraction of unidirectionally encoded images for suppression of heavily isotropic objects (DWISUSHI) postprocessing techniques were used to observe the relationship between the mass and the target nerves. The mean apparent diffusion coefficient (ADC) of nerves was compared among the target neural origin group, non-target neural origin group, and healthy control group using the paired Wilcoxon rank-sum test.

RESULTS

The diagnostic coincidence rates of preoperative DTI and DWI findings with postoperative pathology were 88.1% and 100%, respectively. DTI images were of poor quality when compared to DWISUSHI (P < 0.05). The mean ADC value of the target neural origin group was greater than that of the non-target neural origin group and the healthy control group (P < 0.05).

CONCLUSION

Both DTI and DWISUSHI can stereoscopically display the relationship between peripheral nerves and tumors, but the latter contributes to better quality of the reconstructed images.