CMT 1A: MRI shows increased sciatic nerve cross sectional area in inherited and

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J Neurol Neurosurg Psychiatry. 2010 Oct 22

MRI shows increased sciatic nerve cross sectional area in inherited and

inflammatory neuropathies.

Sinclair CD, Miranda MA, Cowley P, Morrow JM, Davagnanam I, Mehta H, Hanna MG,

Koltzenburg M, Reilly MM, Yousry TA, Thornton JS.

MRC Centre for Neuromuscular Diseases, UCL Institute of Neurology, London, UK.

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.

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 & emsp14;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.