High-resolution ultrasound of peripheral nerves in systemic sclerosis: a pilot study of computer-aided quantitative assessment of nerve density.
OBJECTIVE
To quantitatively evaluate and compare nerve density in patients with limited cutaneous systemic sclerosis (lcSSc) and control subjects using high-resolution ultrasound (US) with a computer-aided assessment.


METHODS
Forty patients and 40 age- and sex-matched control subjects were prospectively enrolled. Ultrasound (US) examination (17-5 MHz probe) of the median nerve at the elbow was performed bilaterally by one radiologist. A software quantified the ratio between the hypoechoic and hyperechoic areas of peripheral nerves on ultrasound. Two observers set the threshold in the images acquired, and three observers performed the digital analysis of nerve density. Statistical analysis included Mann-Whitney U-test of patients versus control subjects and subgroup analysis of symptomatic and non-symptomatic patients. Intra and inter-observer agreement of the three observers were assessed with the kappa statistic.


RESULTS
In all, 160 median nerves were evaluated. According to the US, nerve density was significantly reduced in lcSSc patients compared to control subjects (mean and standard deviation: 41 ± 3 vs 56 ± 4, p < 0.01). Subgroup analysis showed that symptomatic patients (n = 15) had reduced nerve density compared to non-symptomatic (n = 25) patients (39 ± 5 vs 43 ± 4, p < 0.01). Intra-observer agreement was very good (K = 0.82). Inter-observer agreements were good: reader 1 vs reader 2: k = 0.78 (95% confidence interval 0.65 to 0.91); reader 2 vs reader 3: k = 0.72 (95% confidence interval 0.65 to 0.82); reader 3 vs reader 1: k = 0.71 (95% confidence interval 0.64-0.81).


CONCLUSIONS
In lcSSc patients, nerve density was reduced, especially in the symptomatic group, compared to control subjects.
Department of Health Sciences (DISSAL), University of Genoa, Largo Rosanna Benzi 8, 16132, Genoa, Italy.
Bianca
B
Bignotti
Department of Internal Medicine IRCCS Azienda Ospedaliera Universitaria San Martino-IST, Largo Rosanna Benzi 10, 16132, Genoa, Italy.
Massimo
M
Ghio
Department of Medicine, Lavagna Hospital, Via Don Bobbio 25, 16033, Lavagna, Italy.
Nicoletta
N
Panico
Consiglio Nazionale delle Ricerche, Istituto di Matematica Applicata e Tecnologie Informatiche, Via De Marini 6, 16149, Genoa, Italy.
Giulio
G
Tagliafico
Department of Health Sciences (DISSAL), University of Genoa, Largo Rosanna Benzi 8, 16132, Genoa, Italy.
Carlo
C
Martinoli
Institute of Anatomy, Department of Experimental Medicine (DIMES), University of Genoa, Largo Rosanna Benzi, No. 8, 16132, Genoa, Italy. atagliafico@sirm.org.
Alberto
A
Tagliafico
D000328:Adult; D000368:Aged; D000465:Algorithms; D003720:Densitometry / Q000379:methods*; D005260:Female; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008297:Male; D008875:Middle Aged; D010525:Peripheral Nerves / Q000000981:diagnostic imaging*; D010523:Peripheral Nervous System Diseases / Q000000981:diagnostic imaging* / Q000209:etiology; D010865:Pilot Projects; D015203:Reproducibility of Results; D012595:Scleroderma, Systemic / Q000150:complications / Q000000981:diagnostic imaging*; D012680:Sensitivity and Specificity; D014463:Ultrasonography
Nerve density; Neuropathy; Peripheral nerve; Scleroderma; Ultrasound