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 Table of Contents  
CASE REPORT
Year : 2020  |  Volume : 34  |  Issue : 3  |  Page : 206-208

Superficial peroneal nerve entrapment: The eyes do not see what the mind does not know


Department of Anesthesiology and Pain Relief Service, Tata Motors Hospital, Jamshedpur, Jharkhand, India

Date of Submission24-Jul-2020
Date of Decision10-Aug-2020
Date of Acceptance05-Sep-2020
Date of Web Publication28-Dec-2020

Correspondence Address:
Dr. Ashok Jadon
Duplex-63, Vijaya Heritage, Phase-6, Marine Drive, Kadma, Jamshedpur - 831 005, Jharkhand
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/ijpn.ijpn_101_20

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  Abstract 


Entrapment of the superficial peroneal nerve (SPN) is common, but it can remain unrecognized. Due to variable topography of the nerve, the symptoms may vary from pain, tingling, and numbness to weakness in the foot. Therefore, anatomical knowledge is essential for early diagnosis and successful management. We report two cases of SPN entrapment where treatment was delayed due to incorrect diagnosis or inadequate treatment strategy. Both the patients were managed successfully by ultrasound-guided hydrodissection around the SPN and injection of a local anesthetic mixed with corticosteroids. The case reports highlight the importance of ultrasound in the correct diagnosis and early intervention to avoid unnecessary suffering and sequelae of delayed treatment.

Keywords: Hydrodissection, nerve entrapment, peroneal neuropathies, superficial peroneal nerve, ultrasonography


How to cite this article:
Jadon A, Chakraborty S, Sinha N, Singh B. Superficial peroneal nerve entrapment: The eyes do not see what the mind does not know. Indian J Pain 2020;34:206-8

How to cite this URL:
Jadon A, Chakraborty S, Sinha N, Singh B. Superficial peroneal nerve entrapment: The eyes do not see what the mind does not know. Indian J Pain [serial online] 2020 [cited 2021 Jan 18];34:206-8. Available from: https://www.indianjpain.org/text.asp?2020/34/3/206/305135




  Introduction Top


Peripheral nerve entrapments are common, but entrapment of the superficial peroneal nerve (ESPN) is often under-recognized.[1] ESPN results in neuropathic pain in the distribution of SPN. The most common site for ESPN is in the lower third of the leg where the superficial peroneal nerve (SPN) penetrates the deep fascia (crural fascia) and emerges into the subcutaneous tissue. However, SPN course in the middle third of the leg has four variants. This variable topography of the nerve leads to variable symptoms and causes difficulty in the diagnosis. Even if correct diagnosis is done, the identification of the site of entrapment and the early intervention is equally essential to avoid chronicity of the entrapment that may pose a challenge for proper treatment. We report two cases of ESPN. In the first case, ESPN was diagnosed early, but the correct site of entrapment was missed during the first treatment. In the second case, the specific treatment for ESPN was delayed because early treatment was based on acute traumatic pain. In both the cases, ultrasound-guided assessment helped in diagnosis and successful management by adhesiolysis through hydrodissection.


  Case Reports Top


Case 1

A 36-year-old male patient was referred to our pain clinic for the management of severe pain in his right foot. Few months ago, the patient had sustained an injury over his right foot which healed adequately, but 4 weeks later, the patient reported tingling pain over the dorsum of the right foot. He consulted an orthopedic surgeon who suspected ESPN. Injection triamcinolone 20 mg mixed with 6 ml 1% lidocaine was injected underneath the scar near the ankle joint by the treating orthopedic surgeon [Figure 1]a. The patient reported a 25%–30% reduction in pain which lasted for a period of 1 week. Unfortunately, the patient continued to suffer from severe pain despite taking multiple medications (pregabalin 75 mg, amitriptyline 10 mg/day, and tablet urgendol [paracetamol 325 mg + tramadol 37.5 mg] 8 hourly).
Figure 1: (a) Arrows marked the length of total scar, arrowhead marked the most prominent part of the scar where previous injection was given, star marked the most painful area and the point of positive Tinel's sign, (b) High-frequency ultrasound probe placed over painful area, (c) Sonoanatomy showing superficial peroneal nerve (arrowheads) surrounded by fibrous tissue, (d) Insertion of needle in the in-plane approach from anterior to posterior direction, (e) Needle in contact with nerve (arrowhead), (f) Hydrodissection above the nerve, small stars showing fluid spread, (g) Nerve surrounded by fluid all around after adhesiolysis. Ant: Anterior, EDL: Extensor digitorum longus, SPN: N-superficial peroneal nerve, PB: Peroneus brevis, Post: Posterior, ***(fluid spread used for adhesiolysis)

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When the patient presented to us, we noticed that his right foot was swollen. On a numerical rating scale (NRS: 0 means no pain and 10 means worst pain imaginable), he described his pain as 7–8/10 at rest and 10/10 on walking (he was not able to walk even for few steps). A point of intense pain was present approximately 8–10 cm proximal to the ankle [Figure 1]a. When we applied light pressure over this point, it resulted in electric shock sensation all over the foot (positive Tinel's sign). The working diagnosis of ESPN was made, and ultrasound-guided hydrodissection of SPN was planned. After written informed consent, the patient was taken to the operation room for the procedure. The placement of ultrasound probe at the maximal tenderness area caused significant pain to the patient, which is known as sono-Tinel's sign. Hence, intravenous sedation was given with 1 mg midazolam and 25 μg fentanyl. With due aseptic precautions, high-frequency (6–13MHz) ultrasound probe (SonoSite M-Turbo®) was placed in transverse orientation over the most painful area [Figure 1]b. SPN was identified surrounded by thick fibrous tissue [Figure 1]c. After skin infiltration with 1 ml 1% lidocaine, a 50-mm long, 21G blunt insulated needle (Stimuplex®, B. Braun Medical, India) was inserted toward the nerve using in-plane approach. Hydrodissection with 10 ml 0.25% bupivacaine mixed with 20 mg triamcinolone was done by injecting all around the nerve and making it free from surrounding tissue [Figure 1]d, [Figure 1]e, [Figure 1]f, [Figure 1]g. After 10 min, the patient reported excellent pain relief (NRS: 1/10) and he was able to walk in the corridor without any pain. Medicines were slowly withdrawn over 2-week period. The patient revisited after 4 weeks, and later on telephonic contact at 14 weeks, he is symptom free and able to do his regular duty (heavy manual worker).

Case 2

A 25-year-old male patient presented with severe burning pain and occasional numbness over the dorsum of the left foot for more than 2 months. He sustained a cricket ball injury over the left shin while playing cricket. After 1 month of injury, he developed occasional needle and pricking sensation followed by numbness on the dorsum of the foot, especially after standing for long duration or playing. Later, he developed recurrent burning sensation and pain. He also experienced disturbed sleep and episodes of occasional but severe pain at night. On examination, his NRS pain score was 6–7/10 at rest and 9/10 on walking. He also had a tender area at the site of previous injury, and percussion at this point also gave an electric shock-like sensation in the foot (positive Tinel's sign). He was also managed by adhesiolysis through hydrodissection, as done in the first case. However, in this case, the nerve itself was swollen [Figure 2]a and [Figure 2]b. His immediate postprocedure NRS was 0/10 at rest and 1/10 on walking. He also responded to hydrodissection, and no further treatment was required. He was contacted over the phone after 4 weeks of the procedure and then after 3 months and he was symptom free.
Figure 2: (a) Beginning of hydrodissection, superficial peroneal nerve (arrowhead), fluid spread anterior to nerve (small stars), (b) After hydrodissection, nerve (arrowhead) surrounded by injected fluid (small stars). Ant: Anterior, EDL: Extensor digitorum longus, PB: Peroneus brevis, Post: Posterior

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  Discussion Top


An entrapment neuropathy (ENP) is defined as a pressure-induced segmental injury to a peripheral nerve due to an anatomical structure or pathologic process.[2]

ENP of peripheral nerves is common; however, ESPN is rarely recognized due to topographic variability of SPN and variable symptoms, which may lead to misdiagnosis.[1],[3] Symptoms of ESPN include pain, numbness, or paresthesia over the distribution of the nerve. Symptoms usually increase with activity such as running, walking, and often relieved by rest. The history of our patients also showed a similar pattern at the onset of symptoms. However, with increasing duration, burning and pain became continuous in nature.[1] Tinel's sign is an easy and valid method for clinical diagnosis.[4] It is also a reliable indicator of successful outcome after intervention like nerve decompression.[4] In our first case, the patient had a large thick scar at the level of ankle which was suspected incorrectly as the site and cause of nerve entrapment by the orthopedic surgeon. However, the actual site of entrapment was approximately 8–10 cm above the ankle where the nerve pierces the crural fascia to travel within the subcutaneous tissue.[5] In this case, the diagnosis of ESPN was correct; however, the correct site of the entrapment was not addressed as injection was given without any image guidance and at incorrect place. The second case also came after 2 months of suffering and was treated initially as acute traumatic pain and later on the line of neuropathic pain. However, the ultrasound guidance helped us to confirm the diagnosis and treat it adequately. Ultrasound is an essential tool for nerve entrapment diagnosis and management.[6] The entrapment may occur due to fibrous tissue leading to tethering of the nerve (as seen in the first case) or due to posttraumatic edema (seen in the second case) to cause a “mini-compartment syndrome.” The correct anatomy of the nerve and site of the entrapment can easily be diagnosed by the ultrasound.[5],[7] Hydrodissection by the injected fluid separates the constricting tissues and flush out the inflammatory mediators. In addition, the injection of corticosteroids provides the anti-inflammatory effect.[8],[9] However, precise and atraumatic injection techniques are essential for a better outcome.[7],[8],[9] When relief of the symptoms is short lived with the injection therapy, the pulsed radiofrequency treatment of SPN may provide effective relief of symptoms for the longer duration.[10]


  Conclusion Top


Ultrasound essentially helps in the diagnosis and the correct localization of the site of entrapment which is essential for the successful treatment. ESPN can be managed successfully with the ultrasound-guided hydrodissection around the SPN.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form, the patients have given their consent for their images and other clinical information to be reported in the journal. The patients understand that names and initials will not be published, and due efforts will be made to conceal identity, but anonymity cannot be guaranteed.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
  References Top

1.
Tzika M, Paraskevas G, Natsis K. Entrapment of the superficial peroneal nerve: An anatomical insight. J Am Podiatr Med Assoc 2015;105:150-9.  Back to cited text no. 1
    
2.
Toussaint CP, Perry EC 3rd, Pisansky MT, Anderson DE. What's new in the diagnosis and treatment of peripheral nerve entrapment neuropathies. Neurol Clin 2010;28:979-1004.  Back to cited text no. 2
    
3.
Adkison DP, Bosse MJ, Gaccione DR, Gabriel KR. Anatomical variations in the course of the superficial peroneal nerve. J Bone Joint Surg Am 1991;73:112-4.  Back to cited text no. 3
    
4.
Rinkel WD, Castro Cabezas M, van Neck JW, Birnie E, Hovius SER, Coert JH. Validity of the tinel sign and prevalence of tibial nerve entrapment at the tarsal tunnel in both diabetic and nondiabetic subjects: A cross-sectional study. Plast Reconstr Surg 2018;142:1258-66.  Back to cited text no. 4
    
5.
Canella C, Demondion X, Guillin R, Boutry N, Peltier J, Cotten A. Anatomic study of the superficial peroneal nerve using sonography. AJR Am J Roentgenol 2009;193:174-9.  Back to cited text no. 5
    
6.
Krol A. Role of ultrasound in diagnosis and assessment of nerve injury in regional anaesthesia, trauma and chronic pain. In: De Andrés J, editor. Pdate on Regional Anesthesia and Pain Management. Barcelona: MRA Editorial; 1578. p. 764-81.  Back to cited text no. 6
    
7.
Chin KJ. Ultrasound visualization of the superficial peroneal nerve in the mid-calf. Anesthesiology 2013;118:956-65.  Back to cited text no. 7
    
8.
Trescot AM, Brown M. Peripheral nerve entrapment, hydro-dissection, and neural regenerative strategies. Techniques in regional anesthesia and pain management 2015;19:85-93.  Back to cited text no. 8
    
9.
Santoso WM, Rakhmatiar R, Reakhmani AN, Sahidu MG. Comparison of the effectiveness of therapy in hydro-dissection injection using ultrasonography guidance between normal saline and triamcinolone in carpal tunnel syndrome patients. Malang Neurol J 2020;6:5-9.  Back to cited text no. 9
    
10.
Chae WS, Kim SH, Cho SH, Lee JH, Lee MS. Reduction in mechanical allodynia in complex regional pain syndrome patients with ultrasound-guided pulsed radiofrequency treatment of the superficial peroneal nerve. Korean J Pain 2016;29:266-9.  Back to cited text no. 10
    


    Figures

  [Figure 1], [Figure 2]



 

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