Prevalence of fascicular hyperintensities in peripheral nerves of healthy individuals with regard to cerebral white matter lesions

3-T MR neurography of lumbo-sacral plexus in hereditary transthyretin-related amyloidosis with polyneuropathy

OBJECTIVES

Our aim was to evaluate the ability of magnetic resonance neurography (MRN) of the lumbo-sacral plexus (LSP) to distinguish patients with hereditary transthyretin-related amyloidosis with polyneuropathy (ATTRv-PN) from asymptomatic variant carriers (AVC) and healthy controls and to assess its prognostic value.

METHODS

Three-Tesla MRN was performed in 25 consecutive ATTRv-PN patients, 18 AVC, and 10 controls including T2-w DIXON and DWI MR sequences. Two blinded readers independently assessed LSP root diameter and intraneural signal on the MRN images of each subject. MRN findings were compared between groups and correlated with clinical impairment scored on the Neuropathy Impairment Score (NIS) and the modified Polyneuropathy Disability score (mPND).

RESULTS

The agreement between readers on MRN images was excellent (Cohen's kappa = 0.82). LSP root enlargement was significantly more frequent in ATTRv-PN patients compared to AVC (ratio = 4.38, p = 0.038). Increased LSP root intraneural signal on T2-w images was significantly more frequent in ATTRv-PN patients compared to AVC (ratio = 3.4, p = 0.016). In contrast, there were no MRN abnormalities in controls. In ATTRv-PN patients, LSP root enlargement was associated with higher mPND scores (p = 0.03) and increased intraneural signal on T2-w images was associated with significantly higher NIS and mPND scores (p = 0.004 and 0.02, respectively).

CONCLUSIONS

MRN of the LSP can help differentiate ATTRv-PN patients from AVC. LSP root enlargement and increased intraneural signal are significantly associated with clinical impairment, suggesting potential implications for patient care.

KEY POINTS

• ATTRv-PN patients showed abnormal LSP changes on MRN. • MRN of the LSP can help to differentiate ATTRv-PN patients from AVC and healthy controls. • LSP root enlargement and increased intraneural signal were significantly associated with clinical impairment in ATTRv-PN patients.

Routine knee MRI: how common are peripheral nerve abnormalities, and why does it matter?

OBJECTIVE

To evaluate the frequency, MRI appearance, and clinical significance of peripheral nerve abnormalities encountered on routine knee MRI.

MATERIALS AND METHODS

A retrospective review was performed to identify consecutive patients who underwent routine knee MRI from March 2015-2018 and had peripheral nerve abnormalities. MRIs were reviewed for the presence of tibial (TN) and common peroneal nerve (CPN) abnormalities (including hyperintensity, bulbous enlargement, discontinuity, architectural distortion, skeletal muscle denervation). The presence or absence of concomitant meniscal, cruciate, and collateral ligament tears was documented. Patient demographics and clinical outcomes were recorded. Descriptive statistics were reported.

RESULTS

The search yielded 8125 MRIs, of which 50 knee MRIs (patient age (years): 44 + 19) had peripheral nerve abnormalities (hyperintensity (TN: 30%(15/50), CPN: 80%(40/50)), bulbous enlargement (TN: 10%(5/50), CPN: 30%(15/50)), discontinuity (TN: 0, CPN: 4%(2/50)), architectural distortion (TN: 4%(2/50), CPN: 18%(9/50)), and skeletal muscle denervation (TN: 14%(7/50), CPN: 28%(14/50)). Medial meniscus (TN: 12% (6/50), CPN: 36%(18/50)), ACL (TN: 4%(2/50), CPN: 32%(16/50)), PCL (TN: 2%(1/50), CPN: 20%(10/50)), and lateral meniscus (TN: 12%(6/50), CPN: 24%(12/50)) tears were frequently present. Of these, 32% (16/50) were treated for peripheral nerve injury (PNI), characterized as high-grade (n = 7/16) or low-grade (n = 9/16). Nerve discontinuity, architectural distortion, and denervation were encountered more in high-grade PNI than low-grade PNI. Five patients were recalled for follow-up imaging and operative management was performed in 36% of cases (18/50).

CONCLUSION

Although uncommon (frequency = 0.6%), peripheral nerve abnormalities (CPN more common than TN) are encountered on routine knee MRI and affect patient management, with 36% requiring surgical treatment.