Peripheral neuropathy and the role of nerve biopsy: A revisit

Central and Peripheral Nervous System Complications of Vasculitis Syndromes from Pathology to Bedside: Part 2-Peripheral Nervous System

PURPOSE OF REVIEW

Peripheral nervous system vasculitides (PNSV) are a heterogeneous group of disorders with a clinical subset that may differ in prognosis and therapy. We provide a comprehensive update on the clinical assessment, diagnosis, complications, treatment, and follow-up of PNSV.

RECENT FINDINGS

Progress in neuroimaging, molecular testing, and peripheral nerve biopsy has improved clinical assessment and decision-making of PNSV, also providing novel insights on how to prevent misdiagnosis and increase diagnostic certainty. Advances in imaging techniques, allowing to clearly display the vessel walls, have also enhanced the possibility to differentiate inflammatory from non-inflammatory vascular lesions, while recent histopathology data have identified the main morphological criteria for more accurate diagnosis and differential diagnoses. Overall, the identification of peculiar morphological findings tends to improve diagnostic accuracy by defining a clearer boundary between systemic and non-systemic neuropathies. Therefore, the definition of epineurium vessel wall damage, type of vascular lesion, characterization of lymphocyte populations, antibodies, and inflammatory factors, as well as the identification of direct nerve damage or degeneration, are the common goals for pathologists and clinicians, who will both benefit for data integration and findings translation. Nevertheless, to date, treatment is still largely empiric and, in some cases, unsatisfactory, thus often precluding precise prognostic prediction. In this context, new diagnostic techniques and multidisciplinary management will be essential in the proper diagnosis and prompt management of PNSV, as highlighted in the present review. Thirty to fifty percent of all patients with vasculitis have signs of polyneuropathy. Neuropathies associated with systemic vasculitis are best managed according to the guidelines of the underlying disease because appropriate workup and initiation of treatment can reduce morbidity. Steroids, or in severe or progressive cases, cyclophosphamide pulse therapy is the standard therapy in non-systemic vasculitic neuropathies. Some patients need long-term immunosuppression. The use of novel technologies for high-throughput genotyping will permit to determine the genetic influence of related phenotypes in patients with PNSV.

Sural nerve biopsy: current role and comparison with serum neurofilament light chain levels

The diagnosis of peripheral neuropathies can be challenging with consequent difficulties in patients' management. The aim of this study was to explore the current diagnostic role of sural nerve biopsy and to compare pathological findings with serum neurofilament light chain levels (NfL) as biomarkers of axonal damage. We collected demographic, clinical, and paraclinical data of patients referred over 1 year to the Neurology Unit, University of Verona, Italy, to perform nerve biopsy for diagnostic purposes, and we analyzed NfL levels in available paired sera using a high sensitive technique (Quanterix, Simoa). Eighty-two patients were identified (37.8% females, median age 65.5 years). Neuropathy onset was frequently insidious (68.3%) with a slowly progressive course (76.8%). Lower limbs were usually involved (81.7%), with a predominance of sensory over motor symptoms (74.4% vs 42.7%). The most common neuropathological findings were a demyelinating pattern (76.8%), clusters of regenerations (58.5%), and unmyelinated fibers involvement on ultrastructural evaluation (52.4%). A definite pathological diagnosis was achieved in 29 cases, and in 20.7% of patients, the referral clinical diagnosis was modified. Coexistent hematological conditions and hepatitis were diagnostic confounding factors (p = 0.012 and 0.034, respectively). In the analyzed paired sera (n = 37), an inverse despite not significant relationship between NfL values and fiber density was observed (Spearman's rho - 0.312, p = 0.056). In addition, we noted increased serum NfL values of patients with active axonal degeneration. Nerve biopsy remains a useful diagnostic investigation to achieve a correct diagnosis and guide patients' management in selected cases of peripheral neuropathy. Serum NfL is an accessible and potential valuable marker of axonal damage in these conditions.