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) mm2 for the CIDP group, 135.9 (46.5) mm2 for the CMT1A group and 43.3 (19.9) mm2 for the control group. The critical upper value for discriminating pathologically enlarged nerves from normal controls with p<0.05 was 64.4 mm2. 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.
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Funding Funding was partly provided by the Medical Research Council (MRC) Centre for Neuromuscular Diseases, UCL Institute of Neurology. MAM was partially supported by AlBan, High Level Scholarship Programme of the European Union (2004-2006) and Caja de Seguro Social (CSS), Panama. MMR is grateful to the MRC and the Muscular Dystrophy Campaign for their support. This work was undertaken at UCLH/UCL who received a proportion of funding from the Department of Health's NIHR Biomedical Research Centres funding scheme.
Competing interests M G Hanna is Deputy Editor of JNNP but had no role in the editorial process for this paper.
Ethics approval This study was conducted with the approval of the The National Hospital for Neurology and Neurosurgery and the Institute of Neurology Joint Research Ethics Committee.
Provenance and peer review Not commissioned; externally peer reviewed.