# The Role of Ultrasonography in the Diagnostic Evaluation of Patients with Polyneuropathy
## 4 Discussion  
In this retrospective chart review, we explored the role of the US in the diagnostic evaluation of patients with EDx-confirmed polyneuropathy. Most patients in our polyneu \begin{table}
\begin{tabular}{l c c} \hline
**Findings** & **Number** & **Referal Diagnosis/Comment** \\ \hline Demyelinating polyneuropathy & 1 & tarsal tunnel syndrome \\ Expansive lesions & 2 & hereditary polyneuropathy \\ Multifocal CIDP & 2 & typical CIDP and MGUS \\ Thoracic outlet syndrome & 1 & radiation plexopathy \\ Proximal nerve enlargement & 1 & small fiber neuropathy \\ \hline \multicolumn{3}{l}{CIDP—chronic inflammatory demyelinating polyneuropathy; MGUS—monoclonal gammopathy of undetermined significance.} \\ \end{tabular}
\end{table} 
Table 6: Findings in 7 patients with new diagnoses revealed by peripheral nerve ultrasonography (US). ropathy cohort were referred to the US to improve their diagnostic formulation as obtained by clinical and EDx examination. US complements the EDx examination by providing precise anatomical location and information on the etiology of the nerve lesion, thereby increasing sensitivity. The US was first used in routine clinical practice for diagnosing focal monone neuropathies, such as median entrapment neuropathy at the wrist (i.e., carpal tunnel syndrome) and ulnar neuropathy. In the former, it is also used to guide therapeutic injections. In the latter, it is important in differentiating the cubital tunnel entrapment and the retrocondylar compression, which determines treatment [22; 23]. Later, it became clear that the US can also help in diagnosing polyneuroopathies, particularly demyelinating, and the detection of focal neuropathies superimposed on generalized polyneuroopathies. In our population, with a large majority (98%) of patients with abnormal EDx findings, the sensitivity of the US examination was moderate (64%). Sensitivity was found to be higher in patients with typical and multifocal CIDP, with uniform and proximal nerve thickening in the former and segmental nerve enlargement at non-entrapment sites in the latter. These findings are consistent with the literature and support the pathophysiology of segmental inflammation in both diseases [8; 9]. The sensitivity of the US in hereditary polyneuropathy was lower compared to the literature [9; 10]. This can be explained by the inclusion of other types of CMT, not only CMT 1A. The frequent diagnosis in this cohort was also hereditary neuropathy with liability to pressure palsies (HNPP). In that condition, nerve enlargement is less pronounced and frequent at the entrapment sites [7]. The sensitivity in diabetic polyneuropathy was similar to that reported in the literature. In this condition, nerve US generally shows normal or slightly enlarged nerves, particularly the proximal median and tibial nerve segments [10]. Sensitivity was lowest in idiopathic polyneuropathy, where focal nerve thickening at entrapment and non-entrapment sites was the most common finding. The US provided a novel diagnosis in 7 (3%) of our patients, including 2 patients with unexpected findings of peripheral nerve tumors reported elsewhere [24]. We also found nerve thickening at non-entrapment sites typical of focal demyelinating polyneuropathy in a patient with EDx findings typical of axonal polyneuropathy, a finding reported also by others [25]. This is useful in cases where EDx studies are unable to provide exact anatomical location. The US was regarded as contributive in 39 (19%) of our patients by providing information on the nerve size and structures outside the nerves. This is particularly important in patients with polyneuropathy and superimposed focal neuropathy (e.g., patients with diabetic polyneuropathy and suspected median entrapment neuropathy at the wrist). Focal nerve thickening was also found in several patients with amyloid polyneuropathy [20], other metabolic (uremic, vitamin B12 deficiency), autoimmune (rheumatoid arthritis) polyneuropathies, and polyneuropathy of unclear etiology.