MRI shows increased sciatic nerve cross sectional area in inherited and inflammatory neuropathies

Abstract

Measurements of the cross sectional area of the sciatic nerve are described in a group of 10 patients with genetically confirmed Charcot-Marie-Tooth disease type 1A (CMT1A), nine patients with chronic inflammatory demyelinating polyneuropathy (CIDP) and 10 healthy controls using MRI. One mid-thigh of each individual was imaged using a short tau inversion recovery sequence and the nerve appearance evaluated radiologically with respect to the signal intensity and visibility of the internal neural structure. The cross sectional area of the sciatic nerve of each individual was measured by defining irregular enclosing regions of interest on the MRI images. The sciatic nerve area was enlarged in both CMT1A (p<0.001) and CIDP (p=0.008) compared with controls and in CMT1A compared with CIDP (p<0.001). Median (interquartile range) areas were 67.6 (16.2) mm(2) for the CIDP group, 135.9 (46.5) mm(2) for the CMT1A group and 43.3 (19.9) mm(2) for the control group. The critical upper value for discriminating pathologically enlarged nerves from normal controls with p<0.05 was 64.4 mm(2). Quantification of sciatic nerve hypertrophy on MRI may be of assistance in cases where the diagnosis is still in doubt, providing an objective pathological marker complimenting other clinical investigations.

Sciatic nerve tumor and tumor-like lesions—uncommon pathologies

“…There is symmetrical, moderate to marked enlargement of the nerves in CMT type 1A (Fig. 6) [12,39]. Axial T1-weighted images through the lower thighs may show bilateral fatty infiltration of the posterior compartments, with the anterior compartment showing delayed involvement [40].…”

“…Pathologically, there is chronic degeneration and enlargement of nerves with fatty infiltration of the interfascicular epineurium coexisting with demyelination and atrophic fascicles [39].…”

Neuroimaging in diagnosis of atypical polyradiculoneuropathies: report of three cases and review of the literature

“…Brachial and lumbosacral plexus hypertrophy on MRI is also well documented in patients with demyelinating Charcot-Marie-Tooth disease (CMT) [24] and the differential diagnosis with CIDP, besides genetic abnormalities, can also rely on the measurement of the sciatic nerve CSA at mid-thigh by means of MRN [25].…”

Challenges in sciatic nerve repair: anatomical considerations

“…To correlate our results with in vivo studies we reviewed ultrasound and MRI data from sciatic and sural nerves in healthy controls (Table 3). 9,16,23,26,42,44 These studies also demonstrate a large variability with regard to CSA, especially of the sural nerve. 9,15,16,26,44 Specifically, the sural nerve CSA as measured by ultrasound ranged from 1.44 to 5.3 mm 2 .…”