J Korean Neurosurg Soc.  2023 May;66(3):324-331. 10.3340/jkns.2022.0068.

Outcome Analysis of External Neurolysis in Posture-Induced Compressive Peroneal Neuropathy and the Utility of Magnetic Resonance Imaging in the Treatment Process

• Kim J
• Yang J
• Cho Y
• Kang S
• Choi H
• Jeon J

• KMID: 2542018
• DOI: http://doi.org/10.3340/jkns.2022.0068

Abstract

Objective
: We aimed to analyze the effectiveness of external neurolysis on the common peroneal nerve (CPN) in patients with posture-induced compressive peroneal neuropathy (PICPNe). Further, we aimed to examine the utility of magnetic resonance imaging (MRI) in assessing the severity of denervation status and predicting the postoperative prognosis.
Methods
: We included 13 patients (eight males and five females) with foot drop who underwent CPN decompression between 2018 and 2020. We designed a grading system for assessing the postoperative functional outcome. Additionally, we performed MRI to evaluate the denervation status of the affected musculature and its effect on postoperative recovery.
Results
: The median time to surgery was 3 months. The median preoperative ankle dorsiflexion and eversion grades were both 3, while the average functional grade was 1. Posterior crural intermuscular septum was the most common cause of nerve compression, followed by deep tendinous fascia and anterior crural intermuscular septum. There was a significant postoperative improvement in the median postoperative ankle dorsiflexion and eversion grades and average postoperative functional (4, 5, and 2.38, respectively). Preoperative ankle eversion was significantly correlated with denervation status. Additionally, the devernation status on MRI was positively correlated with the outcome favorability. However, denervation atrophy led to a less favorable outcome.
Conclusion
: Among patients with intractable PICPNe despite conservative management, surgical intervention could clinically improve motor function and functional ability. Additionally, MRI examination of the affected muscle could help diagnose CPNe and assess the postoperative prognosis.

Keyword

Peroneal nerve; Peroneal neuropathies; Nerve compression syndromes; Magnetic resonance image; Surgery

Figure

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  Fig. 1. The functional grade of the common peroneal nerve. Grade 1 was assigned if the patient could dorsiflex the ankle but could not raise it up to 0 degrees. Grade 2 was assigned if the ankle could be raised up to 0 degree but the full range of passive movement could not be achieved. Grade 3 was assigned if the patient could dorsiflex the ankle through the full range of passive movement. The preoperative and postoperative functional grades were obtained and compared. Authors modified an original artwork from "WIKIMEDIA COMMONS".

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  Fig. 2. Schematic description of the right knee muscles and compartments for diagnosis of common peroneal neuropathy. We focused on the appearances of these three muscle (TA, EDL, and PL). Reprinted with permission from The Nerve (2021, Choi et al.). T : tibia, anterior : anterior compartment, TA : tibialis anterior muscle, EDL : extensor digitorum longus muscle, lateral : lateral compartment, PL : peroneus longus muscle, F : fibular.

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  Fig. 3. Muscle appearance on axial magnetic resonance imaging was classified with four types. Type 0, normal signal (A); type 1 (B), increase water signal (edema); type 2 (C), fatty infiltration (with or without edema) and type 3 (D), muscle atrophy with decrease volume.

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  Fig. 4. Preoperative motor grades, functional grades, and time to surgery stratified according to the magnetic resonance imaging findings. Motor grade of ankle eversion and functional grade showed a decreasing trend along with the time course of denervation.

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  Fig. 5. Postoperative changes in motor and functional grades are stratified according to the magnetic resonance imaging types. Postoperative improvement in motor and functional grades was positively correlated with progression of muscle denervation, as long as muscle atrophy was absent.

Reference

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