# The Role of Ultrasonography in the Diagnostic Evaluation of Patients with Polyneuropathy
## 2 Materials and Methods
### Primary Outcome Measures
#### 2.4.2 Ultrasonographic Evaluation (US)  
All patients were US examined by one of the authors (SP) or a neurophysiological technician, both with >5 years of experience in performing US studies of peripheral nerves at the beginning of the study period. At the time of evaluation, US practitioners were not blinded to findings of clinical and EDx examinations. We used standard US equipment (ProSound Alpha 7), and a 4-13 MHz linear array transducer (Hitachi Aloka Medical, Ltd., Tokyo, Japan).  
Our main diagnostic criterion was an increase in the nerve cross-sectional area (CSA) measured by manual tracking of the nerve within the hyperechoic rim of the epineurium while positioning the probe perpendicular to the nerve. Our protocol included US evaluation at standard positions: median and ulnar nerves (at the wrist, forearm, elbow, and upper arm), fibular (at the fibular head and in the popliteal fossa), tibial (at the ankle and in the popliteal fossa) and sural nerve (slightly proximal to the ankle). We used a set of our previously reported reference values for nerve CSA [20] (Table 3). When appropriate, we also described changes in nerve echogenicity, thickening of individual nerve fascicles, segmental nerve thickening, and relevant pathologic structures outside of the peripheral nerves. US impressions were described as: (1) generalized nerve enlargement, (2) proximal nerve enlargements, (3) abnormally thin nerves, (4) nerve thickening in proximal limbs, (5) multifocal nerve enlargement at the non-entrapment sites, (6) multifocal nerve enlargement at the entrapment sites, and (7) normal nerves.  
\begin{table}
\begin{tabular}{l c c} \hline
**Polyneuropathy** & & **EDx Criteria** \\ \hline \multirow{8}{*}{Demyelinating} & - & Distal motor latency \(\geq\) 50\% above ULN in 2 nerves \\  & - & Motor conduction velocity \textless{} 70\% of LLN in 2 nerves \\  & - & F-wave latency \(\geq\) 20\% above ULN in 2 nerves \\  & - & Motor conduction block \(\geq\) 30\% \\  & - & Abnormal CMAP temporal dispersion: \\  & - & >30\% duration increase \\  & - & Sensory nerve conduction velocity \textless{} 80\% of LLN \\ \hline \multirow{8}{*}{Axonal} & - & CMAP amplitude \textless{} 80\% of LLN in 2 nerves \\  & - & Normal or slightly reduced conduction velocity \\ \cline{1-1}  & - & SNAP amplitude \textless{} 80\% below LLN in 2 nerves \\ \cline{1-1}  & - & Reduced motor unit recruitment on needle EMG \\ \cline{1-1}  & - & Spontaneous denervation activity on needle EMG \\ \hline \multirow{2}{*}{Mixed} & - & Combined features of axonal and \\  & & demyelelinating polyneuropathy \\ \hline \multirow{8}{*}{Multifocal} & - & Motor conduction block \(\geq\) 30\% at non-entrapment \\  & & sites in \textgreater{}2 nerves \\ \cline{1-1}  & - & Asymmetric segmental demyelination \\ \cline{1-1}  & - & Chronic neurogenic changes on needle EMG \\ \hline \end{tabular}
\end{table}
Table 2: Electrodiagnostic (EDx) criteria for different types of polyneuropathies evaluated in the study.  
\begin{table}
\begin{tabular}{l c} \hline
**Nerve and Site** & **CSA (mm2)** \\ \hline Median & \\ \multicolumn{1}{c}{Wrist} & \textless{}12 \\ \multicolumn{1}{c}{Forearm} & \textless{}10 \\ \multicolumn{1}{c}{Antecubital fossa} & \textless{}12 \\ \multicolumn{1}{c}{Upper arm} & \textless{}13 \\ \hline \end{tabular}
\end{table}
Table 3: The upper reference values for the cross-sectional area (CSA) of the main limb nerves used in the present study.  
We established the contribution of US examination, based on the US criteria for the type of polyneuropathy (Table 4), to the evaluation of patients as one of the following four categories: (1) US revealed new previously unknown information important for diagnosis; (2) US contributive: enhancing clinical and EDx diagnosis by providing relevant additional information; (3) US confirmative: providing evidence confirming clinical and EDx diagnosis; or (4) US not revealing relevant additional information [21].