Diagnostic Value of Sural Nerve Biopsy: Retrospective Analysis of Clinical Cases From 1981 to 2017

Abstract

Nerve biopsy represents the conclusive step in the diagnostic work-up of peripheral neuropathies, and its diagnostic yield is still debated. The aim of this study is to consider the impact of nerve biopsy on reaching a useful diagnosis in different peripheral neuropathies and its changing over time. We retrospectively analyzed 1,179 sural nerve biopsies performed in the period 1981-2017 at Neurological Clinic of Policlinico San Martino (Genoa). We relied on medical records and collected both clinical and pathological data in a database. Biopsy provided univocal diagnoses in 53% of cases (with an increase over time), multiple diagnostic options in 14%, while diagnosis was undetermined in 33% (undetermined reports decreased during the years). In 57% of patients, the pre-biopsy suspicion was confirmed, while in 43% sural biopsy modified the clinical diagnosis. The highest yield was in axonal neuropathies (29% undetermined reports vs. 40% in demyelinating and 48% in mixed neuropathies). In 68% of patients with vasculitic neuropathy, this etiology was already suspected, whereas in 32% nerve biopsy modified the clinical diagnosis. During the years, the number of annually performed biopsies decreased significantly (p = 0.007), with an increase in the mean age of patients (p < 0.0001). The percentage of hereditary neuropathies had a significant decrease (p = 0.016), while the rate of vasculitic and chronic inflammatory neuropathies increased (p < 0.0001). This is the largest Italian study addressing the yield of sural nerve biopsy. During the years, we observed a progressive refinement of the indication of this procedure, which confirms its utility for interstitial neuropathies, particularly if non-systemic vasculitic neuropathy is suspected.

Keywords: amyloidotic neuropathy; axonal neuropathies; demyelinating neuropathies; neuropathy; sural nerve biopsy; vasculitic neuropathy.

Figure 1

Selection criteria.

Figure 2

Number of sural nerve biopsies performed during each year from 1981 to 2017. There is a statistically significant decrease in the number of annually performed histological investigations, with r² = 0.19 and p = 0.007. **p < 0.01.

Figure 3

(A) Average age of patients undergoing sural nerve biopsy during each year from 1981 to 2017. The increase in mean age is statistically significant with r² = 0.64 and p < 0.0001. (B) Percentage of minors compared to all the patients undergoing sural nerve biopsy year by year. The decrease in the percentage of biopsies performed on minors is statistically significant, with r² = 0.35 and p = 0.0001. ***p < 0.001.

Figure 4

(A) Percentage of definite diagnoses year by year, from 1981 to 2017. There is a statistically significant increase in univocal diagnoses, with r² = 0.12 and p = 0.04. (B) Percentage of undetermined reports over the years. The decrease in the percentage of undetermined reports is statistically significant, with r² = 0.3010 and p = 0.0004. *p < 0.05 and ***p < 0.001.

Figure 5

(A) Percentage of genetic neuropathies compared to the total of univocal diagnostic indications over the years. The decrease is statistically significant, with r² = 0.26 and p = 0.016. (B) Percentage of chronic inflammatory neuropathies compared to the total of unique diagnostic indications over the years. The percentage increase is statistically significant, with r² = 0.38 and p < 0.0001. (C) Percentage of vasculitic neuropathies compared to the total of unique diagnostic indications year by year. The percentage increase is statistically significant, with r² = 0.60 and p < 0.0001. (D) Percentage of toxic-deficient and metabolic neuropathies compared to the total of univocal diagnostic indications year by year. The percentage decrease is statistically significant, with r² = 0.22 and p = 0.004. *p < 0.05, **p < 0.01, and ***p < 0.001.

Figure 6

Simplified histological diagnostic pathway in the evaluation of suspected vasculitic neuropathy. The percentages derive from the analysis of 111 biopsies suggestive of vasculitis reported at the Neurological Clinic in the period 1981–2017.