Nerve Ultrasonography as an Additive Tool to Clinical Examination and Electrodiagnostics in Sporadic Mononeuritis – Imaging is the Key

Abstract

Purpose Sporadic mononeuropathies without trauma or compression are challenging to diagnose. Nerve ultrasound has recently proven its usefulness in the diagnosis of traumatic neuropathies, tumors and polyneuropathies. However, its role in mononeuropathies currently remains unclear. We describe ultrasonography follow-up results in 12 patients with suggested spontaneous, monophasic mononeuritis without signs of generalization.

Materials and Methods Nerve conduction studies (NCS), ultrasonography of the affected nerves and the contralateral side, laboratory analysis, and if possible magnetic resonance imaging (MRI) of the affected nerves were established in all patients at onset. In one patient, additive nerve biopsy was performed. In all patients, ultrasonography was repeated after immunotherapy.

Results An infectious pathogen of neuritis was not found in any patient. All but one patient showed predominant axonal nerve damage in NCS, whereas ultrasonography and MRI revealed fascicular and/or overall cross-sectional area (CSA) enlargement or T2 hyperintensity of the affected nerve segments, suggesting an inflammatory background of the neuropathy. Most patients showed significant clinical amelioration of symptoms under treatment (75.0 %) and consequently a decrease in CSA/fascicle enlargement over time (77.8 %).

Conclusion Ultrasonography and MRI of the nerves revealed enlargement in patients with mononeuropathy of axonal NCS pattern of unknown origin. Ultrasonography can facilitate the therapeutic decision for immunotherapy. Next to nerve trauma, nerve tumors and nerve entrapments, ultrasonography reliably shows nerve enlargement in the case of inflammation and therefore could further enrich neurophysiology. Nerve imaging might serve as a follow-up tool by observing a decrease in nerve enlargement and improved function.

Zusammenfassung

Zielsetzung Die Diagnosefindung bei sporadischen Mononeuropathien ohne Trauma oder Kompression in der Vorgeschichte ist eine Herausforderung. Der Nervenultraschall hat sich zwar in der Vergangenheit bei der Diagnostik von Nervenverletzungen, -tumoren und Polyneuropathien bewährt, seine Rolle bei sporadischen Mononeuropathien ist jedoch völlig unklar. Im Folgenden beschreiben wir 12 Fälle spontaner, vermutlich immunvermittelter sensibler, schmerzhafter und/oder motorischer Mononeuropathien, die keine Hinweise auf eine Generalisierung aufwiesen.

Material und Methoden Alle Patienten erhielten Elektrophysiologie, Nervenultraschall und wenn möglich ein Nerven-MRT der betroffenen und der Gegenseite sowie ausgedehnte Laboruntersuchungen. Ein Patient erhielt eine Nervenbiopsie. Die Untersuchungen wurden bei allen Patienten nach Immuntherapie wiederholt.

Ergebnisse Infektiöse Erreger einer Neuropathie fanden sich bei keinem Patienten; alle Patienten zeigten mit einer Ausnahme ein elektrophysiologisch axonales Schädigungsmuster. Alle Patienten zeigten fokale, faszikulär begrenzte oder ausgedehnte Nervenschwellungen, korrelierend mit T2-Hyperintensitäten im Magnetresonanztomogramm (MRT), hinweisend auf einen entzündlichen Prozess. Unter Immunbehandlung zeigten die meisten Patienten (75,0 %) eine klinische Besserung und einen Rückgang der Nervenschwellungen (77,8 %).

Schlussfolgerung Die periphere Bildgebung konnte Nervenschwellungen bei Patienten mit axonaler Neuropathie unklaren Ursprungs zeigen und somit die Entscheidung für eine immunmodulatorische Therapie erleichtern. Neben seiner Wertigkeit bei Nerventraumata, Nerventumoren und Engpass-Syndromen kann der Nervenultraschall in der Diagnostik entzündlicher Mononeuropathien die Elektrophysiologie somit sehr bereichern. Ferner kann er als Verlaufsbiomarker für ein Therapieansprechen genutzt werden.

Key words

nerve ultrasound - neuropathy - nerve inflammation - nerve imaging - nerve constriction

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