The subparaneurial compartment: A new concept in the clinicoanatomic classification of peripheral nerve lesions

Abstract

Based on our experience in treating peripheral non-neural sheath derived pathology, we have identified a novel pattern of lesion progression along the anatomic course of nerves. This report highlights the existence of a subparaneurial compartment around peripheral nerves. We first applied an anatomic framework to review MR images and intraoperative photographs of patients treated by the senior author in the last 10 years. After identifying a pattern that was consistent with subparaneurial lesion progression, we searched for other examples of cases that might exhibit this pattern. Four examples of subparaneurial pathology were identified, a hemangioma of the ulnar nerve, a ganglion cyst of the common fibular nerve, a lymphoma of the sciatic nerve and a lipoma of the ulnar nerve. All four patients were operated on and had intraoperative photographs; three had high resolution MR imaging. This report highlights the existence of pathology contained within a subparaneurial compartment, outside of the epineurium, that follows the course of the nerve and surrounds it circumferentially. The subparaneurial localization of peripheral nerve lesions has hitherto received little attention. Identification of this new pattern on preoperative MRI may have implications for surgical management.

Ultrasonographic and Imaging Appearance of Peripheral Intraneural Vascular Anomalies: Report of Two Cases and Review of the Literature.

“…According to our review, the current imaging techniques commonly used, US (high resolution gray scale US, Doppler) and MRI, demonstrated a close relation between the nerve path and the vascular anomaly, accurately indicating the diagnosis in 22 cases [23,[26][27][28][29][30][31][32][33][34][35]37]. Also, we found a single case in which postoperative histopathological examination confirmed the imaging diagnosis of hemangioma, established exclusively by using computed tomography [13].…”

“…Gender distribution. Three papers [8,19,33] reported a total of 9 cases presenting only the afflicted nerve and the histopathological diagnosis, without supplemental data. In these cases patient gender was labeled NA (not available) and they were not included in the calculation.…”

“…Pathology For 30 cases (55.55%) the final diagnosis was hemangioma, based on histopathological analysis. Of these tumors, 24 were located at the level of upper limb, affecting the median nerve (11 cases) [3,9,13,15,18,[23][24][25]30,32], ulnar nerve (8 cases) [8,16,19,26,31,33], digital branches of ulnar and radial nerves (4 cases) [7,20,29,31] and the inferior trunk of brachial plexus (1 case) [22]. The other 6 tumors were located at the level of lower limb, involving the sciatic nerve (2 cases) [27,31], peroneal nerve (3 cases) [5,11,19] and posterior tibial nerve (1 case) [14].…”

“…The other 6 tumors were located at the level of lower limb, involving the sciatic nerve (2 cases) [27,31], peroneal nerve (3 cases) [5,11,19] and posterior tibial nerve (1 case) [14]. These lesions were named differently by the authors: hemangioma [3,11,13,16,[18][19][20]22,24,26,31,33], intraneural hemangiomas [5,[7][8][9]15,23,29], endoneural hemangioma, intrinsic hemangioma [25] or capillary hemangioma [27,30,32]. Konet al [7] described one case in which the coexistence of an intraneural hemangioma and an extraneural cavernous hemangioma at the level of the digital branches of the ulnar nerve was observed.…”

“…Hemangiomas (17 cases) appear as tissue masses with hypo-or isosignal on T1 weighted sequences and T2 hypersignal, well delineated, with signal void due to multiple vessels, presenting early and heterogeneous enhancement after gadolinium [20,[22][23][24][25]27,29,[30][31][32][33].…”