Diffusion tensor imaging can be used to detect lesions in peripheral nerves in patients with chronic inflammatory demyelinating polyneuropathy treated with subcutaneous immunoglobulin.
BACKGROUND
Magnetic resonance imaging (MRI) with diffusion tensor imaging (DTI) has shown that fractional anisotropy (FA) is lower in peripheral nerves in chronic inflammatory demyelinating polyneuropathy (CIDP). We examined whether DTI correlates to muscle strength or impairment.


METHODS
MRI of sciatic and tibial nerves was performed on 3-T MR scanner by obtaining T2- and DTI-weighted sequences with fat saturation. On each slice of T2-weighted (T2w) and DTI, the tibial and sciatic nerves were segmented and served for calculation of signal intensity. On DTI images, pixel-by-pixel calculation of FA and apparent diffusion coefficient (ADC) was done. Muscle strength at knee and ankle was determined by isokinetic dynamometry and severity of CIDP by neuropathy impairment score (NIS).


RESULTS
Fourteen CIDP patients treated with subcutaneous immunoglobulin were compared to gender- and age-matched controls. T2w values expressed as a nerve/muscle ratio (nT2w) were unchanged in CIDP versus controls 0.93 ± 0.21 versus 1.02 ± 0.21 (P = 0.10). FA values were lower in CIDP compared to controls 0.38 ± 0.07 versus 0.45 ± 0.05 (P < 0.0001), and ADC values were higher in CIDP versus controls 1735 ± 232 versus 1593 ± 116 × 10(-6) mm(2)/s (P = 0.005). In CIDP, FA values correlated to clinical impairment (NIS) (r = -0.57, P = 0.03), but not to muscle strength. FA value in the sciatic nerve distinguishes CIDP from controls with a sensitivity and a specificity of 92.9 %.


CONCLUSIONS
CIDP patients have unchanged nT2w values, lower FA values, and higher ADC values of sciatic and tibial nerves compared to controls. FA values correlated to NIS but were unrelated to muscle strength. DTI of sciatic nerves seems promising to differentiate CIDP from controls.
Department of Neurology, Aarhus University Hospital, Noerrebrogade 44, DK-8000, Aarhus C, Denmark. larsmark@rm.dk.
Lars H
LH
Markvardsen
Department of Neurology, Aarhus University Hospital, Noerrebrogade 44, DK-8000, Aarhus C, Denmark.|Department of Diagnostic Imaging: MR Research Centre, Aarhus University Hospital, Aarhus, Denmark.
Michael
M
Vaeggemose
Department of Diagnostic Imaging: MR Research Centre, Aarhus University Hospital, Aarhus, Denmark.
Steffen
S
Ringgaard
Department of Neurology, Aarhus University Hospital, Noerrebrogade 44, DK-8000, Aarhus C, Denmark.
Henning
H
Andersen
D000368:Aged; D056324:Diffusion Tensor Imaging / Q000379:methods*; D005260:Female; D006801:Humans; D007136:Immunoglobulins / Q000008:administration & dosage*; D007279:Injections, Subcutaneous; D008297:Male; D008875:Middle Aged; D053580:Muscle Strength / Q000187:drug effects*; D010525:Peripheral Nerves / Q000000981:diagnostic imaging* / Q000187:drug effects / Q000503:physiopathology*; D020277:Polyradiculoneuropathy, Chronic Inflammatory Demyelinating / Q000000981:diagnostic imaging* / Q000188:drug therapy / Q000503:physiopathology*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D016896:Treatment Outcome
D007136:Immunoglobulins
CIDP; Diffusion tensor imaging; MRI; Muscle strength; Subcutaneous immunoglobulin