- Email: [email protected]
Intraneural Ganglia of the Common Peroneal Nerve in Children: Case Report and Review of the Literature
Case Report
Intraneural Ganglia of the Common Peroneal Nerve in Children: Case Report and Review of the Literature Alessandro Consales1, Mattia Pacetti1, Alessia Imperato1, Maura Valle2, Armando Cama1
Key words Children - Cyst - Intraneural ganglia - Peroneal nerve - Surgery -
Abbreviations and Acronyms CPN: Common peroneal nerve DPN: Deep peroneal nerve EHL: Extensor hallucis longus muscle EMG: Electromyography IG: Intraneural ganglia MR: Magnetic resonance NCS: Nerve conduction studies PM: Peroneal muscles PN: Peroneal nerve TA: Tibialis anterior muscle TF: Tibiofibular US: Ultrasound From the Departments of 1Neurosurgery and 2Radiology, Istituto Giannina Gaslini, Genova, Italy To whom correspondence should be addressed: Alessandro Consales, M.D. [E-mail: [email protected]
- OBJECTIVES:
Intraneural ganglia are nonneoplastic cystic formations contained within the epineurium of peripheral nerves. The common peroneal nerve at the fibular neck is the most frequently affected site. Intraneural ganglia are not a frequent occurrence in the adult patients and are even rarer in children, with only 10 pediatric cases reported in the English language literature. We report on a new pediatric case of intraneural ganglion of common peroneal nerve and present a review of the English language literature on this topic in children.
- METHODS:
A 10-year-old girl was admitted to our institution because of pain referred to posterior and anterior aspects of the right leg and right foot drop. The radiologic investigations showed a wide (20 cm long) intraneural ganglion cyst of the right common peroneal nerve. The patient underwent surgical treatment according to the Spinner technique.
- RESULTS:
Postoperative course was uneventful. A gradual improvement of motor and sensory functions was observed, starting from the third postoperative day, with a complete motor function restoration registered 26 months after surgery.
- CONCLUSIONS:
Intraneural ganglia of the common peroneal nerve should always be considered in the differential diagnosis of foot drop in pediatric age since because early diagnosis and adequate surgical treatment play a crucial role in the patient’s motor and sensory outcomes.
Alessandro Consales and Mattia Pacetti are equally contributed. Citation: World Neurosurg. (2016) 86:510.e11-510.e17. http://dx.doi.org/10.1016/j.wneu.2015.10.023 Journal homepage: www.WORLDNEUROSURGERY.org Available online: www.sciencedirect.com 1878-8750/$ - see front matter ª 2016 Elsevier Inc. All rights reserved.
INTRODUCTION Intraneural ganglia (IG) are non-neoplastic, fluid-filled cystic formations contained within the epineurium of peripheral nerves. Although many peripheral nerves may be affected, the common peroneal nerve (CPN) at the fibular neck is by far the most frequently affected site.1-8 The pathogenesis of IG remained a controversial issue for a long time in the past, until a “unifying articular” or “synovial” theory was proposed by Spinner and colleagues.3,7,9 According to their theory, the formation of IG in peroneal nerve is a dynamic process starting in a degenerating superior tibiofibular (TF) joint and subsequently
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extending to the nerve along its articular branch intraepineurally via a path of least resistance determined by pressure fluxes. IG of the CPN are not a frequent occurrence in the adult population, prevailing in adult males, with a reported mean age of 34. They are even rarer in children.10-12 To our knowledge, only 10 pediatric cases of IG of the CPN have been reported in the English language literature.10,12-19 We report on a new pediatric case of intraneural ganglion of the CPN and present a review of the literature on this topic in pediatric age.
CASE REPORT History A 10-year-old girl was admitted to our observation on 13 July, 2008. Her clinical history began in April 2008. Immediately after a 2-hour flight, the patient complained of pain in the posterior aspect of the right leg, extending to the anterior aspect and
associated with slapping gait. She did not play any sport. No history of previous knee trauma was reported. The pain was reported as continuous, responding to nonsteroid anti-inflammatory drugs, and worsening in the supine position. It disappeared gradually in a few days, while the neurologic deficit persisted unchanged. The girl was examined by her family pediatrician and underwent diagnostic work-up at another institution, consisting of ultrasound (US) examination, magnetic resonance (MR) of the right lower limb, and electrophysiologic studies. On the first nerve conduction studies (NCS), made 3 weeks after the onset of symptoms, the right peroneal nerve motor study showed a decrease in amplitude of compound motor action potential (MAP) and in motor conduction velocity (MCV). It was confirmed by a second electrophysiologic evaluation, made 1 month later. The needle electromyography (EMG) study of the right anterior tibial muscle showed fibrillation
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CASE REPORT ALESSANDRO CONSALES ET AL.
INTRANEURAL GANGLIA OF COMMON PERONEAL NERVE IN CHILDREN
potentials (grade þ1), motor unit action potentials of normal amplitude and duration but with irregular morphology, and a marked reduction of recruitment. There was electrophysiologic evidence of a subacute right common peroneal neuropathy. MR and US examination suggested the presence of a CPN tumor. Thus the patient was referred to our institution for diagnostic and therapeutic management. Examinations Neurologic examination revealed paralysis of dorsiflexion, eversion of right foot, and extension of right toes (grade 0/5 of muscle strength of tibialis anterior [TA], extensor hallucis longus [EHL], and peroneal muscles [PM]), resulting in foot drop and characteristic slapping gait. Moreover, sensory loss extending to the anterolateral surface of the lower leg and the dorsum of foot and toes was observed. MR performed at the other institution was considered useless due to patient movement artifacts. It was therefore repeated at our hospital, showing a wide (20-cm long) intraneural ganglion cyst of the right CPN (see Figures 1, AeD and 2, A for further explanations). The decision to perform surgical treatment of the ganglion cyst was made. Operation The patient underwent surgical treatment on 25 July, 2008. With the patient in the left lateral decubitus position, an enlarged CPN was exposed through a curved incision over the posterolateral aspect of the proximal leg, extending from the popliteal crease posteriorly, the fibular neck laterally, and then distally as far as the anterior compartment. Under loupe magnification and after opening of the peroneus longus muscle (PL) fascia, the CPN articular branch, deep peroneal nerve (DPN), and superficial peroneal nerve (SPN) were identified and mobilized. Next, the CPN articular branch was completely dissected and exposed up to the superior TF joint. The articular branch was completely enlarged along its course. Once cyst dissection was completed (Figure 3, A), the following surgical steps were performed as described by Spinner et al.7: 1) resection of
Figure 1. Preoperative magnetic resonance imaging (MRI) examination of the right knee using (A) T1-weighted, (B) fat-suppressed T2-weighted, and (C) gadolinium-enhanced T1-weighted sequences. They demonstrate a swollen, fluid-filled common peroneal nerve (arrow) reflecting intraneural involvement by a large ganglion cyst that expands cranially within the nerve substance from the level of the superior tibiofibular joint. Transverse, fat-suppressed tSE-T2w MRI of the distal thigh (D) reveals the intraneural ganglion of the peroneal nerve reaching the sciatic bifurcation. The cyst (1) entered the sciatic tracking the fascicles of the peroneal nerve. The tibial nerve and tibial component (2) of the sciatic bifurcation were totally unaffected. The longitudinal extension of the cyst in the sciatic was approximately 8 cm without cross-over paths.
the superior TF joint (when the capsule was penetrated, cyst fluid was seen; Figure 3, B); 2) disconnection of the articular branch from the superior TF joint by means of ligation and transection with preservation of the branch innervating the TA (Figure 3, C); 3) cyst decompression by means of limited longitudinal epineurotomy, performed away from the CPN fascicles previously identified intraoperatively with nerve stimulation. Abundant gelatinous material, released under some pressure, was evacuated (Figure 3, D). Finally, hemostasis was carried out and the wound was closed in anatomic layers with a subcuticular suture.
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Postoperative Course Postoperative course was uneventful. Three days postoperatively, some motor function was observed (right big toe extension: grade 1/5 of muscle strength). Physical therapy was started 2 weeks postoperatively. Postoperative MR was performed 3 months after surgery (see Figure 2, B). Four months after surgery, significant improvement of muscle strength (grade 3/5) of TA, EHL, and PM was observed. Moreover, concerning the sensory function, the light touch was restored. Seven months after surgery, further motor improvement of all previously mentioned muscles was observed (grade 4-/5 of
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Figure 2. Magnetic resonance neurography of the peroneal intraneural ganglion obtained (A) preoperatively and (B) postoperatively. In (A) the bulk of the ganglion (narrow arrow) is seen arising from the anterior aspect of the superior tibiofibular joint. The bulk of the ganglion communicates with the main trunk of the nerve (large arrow) through a long tubular process (arrowheads) representing the dilated articular branch of the peroneal nerve. (B) After ligation of the articular branch, fluid distension of the peroneal nerve is no longer appreciated.
muscle strength). Sensory function was completely normal. Physical therapy was continued until motor function was completely restored (grade 5/5 of muscle strength of TA, EHL, and PM) 26 months postoperatively. This clinical picture remained unchanged at the latest followup (6 years). DISCUSSION IG are non-neoplastic, fluid-filled cystic lesions contained within the epineurium of peripheral nerves. Many nerves may be affected; however, the CPN at the fibular neck is the most frequently affected site.1-8 First described by Beauchêne20,21 in 1810, IG affect predominantly male adults.11 The pathogenesis of these lesions was a matter of debate in the literature until the early 2000s. Starting from 2003, after reviewing a large cohort of patients and analyzing accurately the literature on the topic, Spinner and colleagues proposed, discussed, and substantiated the socalled “unified articular (synovial) theory”
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on the basis of clinical, anatomic, radiologic, and histologic data.1-9 According to this theory, the formation of intraneural ganglia is a dynamic process: Synovial fluid exits a neighboring capsular defect of a degenerating joint. Then, as Spinner et al. stated, “fluid tracks along the articular branch of a nerve intraepineurally via a path of least resistance along tissue planes” and “pressure fluxes determine the extent of dissection.”7 In CPN IG, the cyst fluid comes from the anterior portion of the superior TF joint, dissects tissue planes along the U-shaped articular branch, and finally reaches the deep peroneal portion of the CPN.6 In case of very high pressure, the cyst may extend more proximally up to the sciatic nerve.2 CPN IG are a rare entity and occur more frequently in adult male patients.11 Symptoms and signs include pain, motor, and/or sensory deficits in the CPN (DPN is particularly involved because of anatomic reasons) territory. A mass can be palpated in the anterolateral aspect of the knee. Moreover, the
Tinel sign can be elicited in the same region. History of knee trauma can also be present.7,22 EMG and nerve conduction studies (NCS) are useful to confirm CPN lesions (DPN lesions, more typically; however, also broader involvement of CPN and tibial division of sciatic nerve can occur7,22). Imaging studies (CT, US, MR) are important tools to make a correct preoperative diagnosis and to plan adequate surgical treatment. Among them, MR is the study of choice. It can show the cystic nature of the CPN lesion and its relationship with the superior TF joint. According to the unified articular theory, surgical treatment of CPN intraneural ganglia should be performed following these steps: 1) complete dissection of the cyst; 2) disarticulation, that is, resection of the superior TF joint to prevent extraneural cyst recurrence; 3) cyst decompression by means of limited epineurotomy to avoid neurologic injury; and 4) disconnection of CPN articular branch to prevent intraneural recurrence. Steps 2e4 can be carried out in any order.7 Concerning the outcome of patients affected by peroneal IG, it must be remarked that the best results are obtained in pain control.23 This is probably due to cyst decompression with consequent decrease in intraneural pressure.3,4 Motor recovery is less predictable. It may depend on several factors, including duration of symptoms, extent of compression, length of the cyst, neural anatomy of the TA, and intrinsic lower recovery ability of the PN compared with many other nerves.3,4 IG involving the only CPN in pediatric age are extremely rare. PubMed was searched for key words including intraneural ganglia, common peroneal nerve, and peroneal nerve cyst. Only studies in which patients younger than 16 years old could be indentified were included in our review. Using these selection criteria, only 10 pediatric cases were found to date in the English language literature.10,12-19 Clinical and radiologic findings of these cases are summarized in Table 1. The age range varied from 4e15 years. Motor deficit, progressive or sudden, was documented in all the patients. Sensory
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INTRANEURAL GANGLIA OF COMMON PERONEAL NERVE IN CHILDREN
cases (outcome not reported in one of these cases), with full motor recovery occurring from 2 weeks to 14 months (see Table 1).10,13,14 In our case, clinical onset was sudden, as in only one previously published case. Our patient showed complete motor recovery at 26 months and the clinical picture remained unchanged at the last visit, after the longest follow-up (6 years) documented to date for pediatric cases. This can indirectly confirm the value of the recommendation by Spinner and colleagues about the importance of performing 4 steps in the surgical treatment of IG.7 In particular, steps 2 and 4 are of paramount importance to avoid, respectively, extraneural and intraneural recurrence of the ganglia. The range of techniques used by other practitioners for CPN IG were considerably different than Spinner7 (see Table 1). However, the reported follow-up duration (see Table 1) was probably not sufficient to adequately evaluate surgical outcome in the long term. Only Waldschmidt and Slongo19 reported a long follow-up of 24 months. In their case, differently from Spinner’s technique, the surgical approach lacked disarticulation of the TF joint and disconnection of the CPN articular branch. Of note, recurrence was observed at 2 years of follow-up, even if the patient remained asymptomatic. Motor recovery after surgery in pediatric patients affected by IG of the CPN is generally better compared with adult patients. Our case confirms this trend. On the basis of the pertinent literature, the recovery of the sensory function is less predictable (see Table 1).10,12-19 Anyway, our patient had a full sensory recovery.
Figure 3. (A) Exposition of intraneural ganglion of the common peroneal nerve (CPN); see also the CPN articular branch (hollow arrowhead), superior tibiofibular joint (hollow arrow), the deep peroneal nerve (d), and the superficial peroneal nerve (s); (B) resection of the superior TF joint (arrow); (C) disconnection of the articular branch (arrow) from the superior TF joint; and (D) cyst decompression with release of gelatinous material (arrow).
CONCLUSION symptoms and signs are variable, as reported in adult patients. Two cases presented with a history of knee trauma12,13 and 5 with a palpable mass around the fibular neck.10,13,16,18,19 Early presentation of the clinical findings suggests a possible capsular laxity or defect. Every patient was operated after the diagnosis of intraneural cyst.
In 5 cases, a connection between the CPN articular branch and the superior TF joint was suspected at imaging and/or documented at surgery, requiring ligation, section, and disconnection of the nervous branch from the previously mentioned joint (see also Table 1).13-15,18 Neurologic outcome (strength) was excellent in 4 out of 10 previously published
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IG is an uncommon disease in adult age, and it is even rarer in children. Any nerve may be affected, but the CPN at the fibular neck is the most frequently affected side. IG of CPN should always be considered in the differential diagnosis of foot drop in pediatric age. Clinical features are similar in adults and in children, except for the outcome, which is better in children. Early diagnosis and treatment play a crucial role
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Authors & Year
Age (years), Sex
8, F Al Mufargi et al., 201113
Side Left
Clinical Findings Post-traumatic foot drop; palsy of foot dorsiflexion
Preoperative Neurophysiology
Radiology
Operation
Postoperative Neurophysiology
EMG: compressive lesion of US: hypoechogenic lesion over Cyst excision and articular CPN Not reported the PN at the fibular head the fibular head with suspected branch disruption connection with the proximal TF joint
Follow-up (weeks/ months)/Clinical Outcome 2 months/ complete motor recovery
Not Cystic swelling in the knee near EMG: mixed lesion of the reported the fibular head; progressive CPN at the fibular head foot drop; decreased sensation over the dorsum of the foot
US þ MR: cystic lesion communicating with the proximal TF joint
Aprin et al., 200710
4,5 M
Left
MR: 2 x 1,8 x 2, 5-cm cystic Nerve sheath incision, fluid mass at the fibular head, no drainage, cyst excision, TA and connection between the cyst and fascia incision the proximal TF joint
Aulisa et al., 199814
15, F
Not Sudden foot drop; intermittent reported knee pain; deficit of DPN muscles
NCS: slowing of conduction US þ MR: mass at the neck of Incision of the lesion and its Signs of in DPN; EMG: fp mild on TA the fibula excision from the nerve sheaths, rearrangement of and EHL, absent on PL; VA section of the stalk of motor unit potential absent on TA, normal on PL, connection with the proximal TF so on EHL joint
12 months/Full motor recovery and absence of sensory deficits
Johnston & Lyne, 200715
4, F
Left
Progressive foot deformity; mild leg atrophy; drop-foot gait; deficit of ankle dorsiflexion and great toe extension
NCS: prolonged latency of CPN at the knee. EMG: denervation in EDB, decreased recruitment in TA and EDB
12 months/ Improved strength (grade 4/5)
Leijten et al., 12, M 199216
Right
Foot drop; knee pain spreading EMG: marked conduction to the great toe; deficit of foot slowing at the head of the and toes extension and eversion; fibula hypoesthesia of the medial aspect of the foot and anesthesia of the great toe; string-like structure at the head of the fibula
Luigetti et al., 11, M 201217
Left
Progressive foot drop
Nicholson 4, M et al., 199518
Left
Deficit of foot eversion and dorsiflexion and of great toe extension; firm mass at the fibular neck
Foot drop; no ankle or great toe Not performed dorsiflexion; soft painful mass behind the neck of the fibula
Ganglion and articular nerve branch resection
MR: 4 x 1 cm cystic mass at the Nerve sheath incision, fluid fibular neck, connection (tail drainage, articular branch sign) between proximal TF joint ligation and transection and the cystic mass, anterior and lateral compartment muscles hyperintensity (denervation) US: 8 cm fusiform echolucent lesion along the CPN
Not reported
2 weeks/ Complete motor and sensory recovery
EMG (2 months): 14 months/full isolated motor recovery involvement of CPN with 63% reduction in amplitude
Not reported
1 month/No functional improvement (patient fitted with footextension device)
No signs of PN entrapment MR: CPN thickening (about 15 cm) and hyperintensity
Resection of the ganglion cyst
Not reported/mild improvement of the symptoms
NCS: no compound MAP US: hypoechoic mass around the from the CPN at ankle. EMG: neck of the fibula denervation on the PL and TA
Nerve sheath incision and cyst Not reported excision; adjunctive excision of a smaller cyst connecting the main cyst with the proximal TF joint
Not reported
6 months/ Improved global strength
CASE REPORT
Epineurium longitudinal incision Not reported and cyst excision with a sacrifice of about 40% of the nerve fascicles
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9, M
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Table 1. Intraneural Ganglia of the Common Peroneal Nerve in Children: Literature Review
CASE REPORT
EMG, electromyography; US, ultrasound; CPN, common peroneal nerve; MR, magnetic resonance; TF, tibiofibular; DPN, deep peroneal nerve; NCS, nerve conduction studies; Fp, Fibrillation potential; TA, tibialis anterior; EHL,extensor hallucis longus; PL, peroneus longus; VA, maximal voluntary activity; TA, tibialis anterior; EDB, extensor digitorum brevis; PN, peroneal nerve.
Left 12, M Waldschmidt and Slongo, 201019
Right
Progressive foot drop, PM and TA atrophy, foot pronation and dorsiflexion deficit, cystic mass at the fibular neck
EMG: loss of conductivity at MR: 4 cm mass at the fibular the fibular head; decreased neck amplitude of motoric sum potentials
Cyst opening and dismantling
Not reported
24 months/good recovery with minor deficit (9 months); recurrence at 24 months (pt. asymptomatic: no reoperation)
INTRANEURAL GANGLIA OF COMMON PERONEAL NERVE IN CHILDREN
Scherman 9, M et al., 198112
Post-traumatic knee swelling; EMG þ NCS: complete Not reported progressive foot drop; deficit of conduction block in the CPN foot and toes dorsiflexion and at the head of the fibula foot eversion; hypoesthesia along the medial aspect of the foot
1st surgery: small longitudinal Not reported cyst incision and fluid drainage; 2nd surgery: mass dissection and excision
Not reported
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in complete recovery of motor and sensory functions. REFERENCES 1. Spinner RJ, Amrami KK, Angius D, Wang H, Carmichael SW. Peroneal and tibial intraneural ganglia: correlation between intraepineurial compartments observed on magnetic resonance images and the potential importance of these compartments. Neurosurg Focus. 2007;22:E17. 2. Spinner RJ, Amrami KK, Wolanskyj AP, Desy NM, Wang H, Benarroch EE, et al. Dynamic phases of peroneal and tibial intraneural ganglia formation: a new dimension added to the unifying articular theory. J Neurosurg. 2007;107:296-307. 3. Spinner RJ, Atkinson JL, Scheithauer BW, Rock MG, Birch R, Kim TA, et al. Peroneal intraneural ganglia: the importance of the articular branch. Clinical series. J Neurosurg. 2003;99: 319-329. 4. Spinner RJ, Atkinson JL, Tiel RL. Peroneal intraneural ganglia: the importance of the articular branch. A unifying theory. J Neurosurg. 2003;99: 330-343. 5. Spinner RJ, Carmichael SW, Wang H, Parisi TJ, Skinner JA, Amrami KK. Patterns of intraneural ganglion cyst descent. Clin Anat. 2008;21:233-245. 6. Spinner RJ, Desy NM, Amrami KK. Cystic transverse limb of the articular branch: a pathognomonic sign for peroneal intraneural ganglia at the superior tibiofibular joint. Neurosurgery. 2006;59: 157-166. discussion 157-166. 7. Spinner RJ, Desy NM, Rock MG, Amrami KK. Peroneal intraneural ganglia. Part I. Techniques for successful diagnosis and treatment. Neurosurg Focus. 2007;22:E16. 8. Spinner RJ, Desy NM, Rock MG, Amrami KK. Peroneal intraneural ganglia. Part II. Lessons learned and pitfalls to avoid for successful diagnosis and treatment. Neurosurg Focus. 2007;22:E27. Review. 9. Spinner RJ, Scheithauer BW, Amrami KK. The unifying articular (synovial) origin of intraneural ganglia: evolution-revelation-revolution. Neurosurgery. 2009;65(suppl 4):A115-A124. 10. Aprin H, Weinberg J, Lustrin ES, Abrutyn D. Peroneal nerve palsy due to an intraneural ganglion: a case report of a 4 1/2-year-old boy. Am J Orthop (Belle Mead NJ). 2007;36:E40-E42. 11. Nucci F, Artico M, Santoro A, Bardella L, Delfini R, Bosco S, et al. Intraneural synovial cyst of the peroneal nerve: report of two cases and review of the literature [review] Neurosurgery. 1990; 26:339-344. 12. Scherman BM, Bilbao JM, Hudson AR, Briggs SJ. Intraneural ganglion: a case report with electron microscopic observations. Neurosurgery. 1981;8: 487-490. 13. Al Mufargi YS, Mouch CA, Ziebarth K, Joeris A, Slongo T. An unusual cause of paralysis of the peroneal nerve: a report of 3 cases. J Pediatr
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Orthop. 2011;31:e50e52. Retraction in: Hensinger RN, Thompson GH. J Pediatr Orthop. 2012;32:748. 14. Aulisa L, Tamburrelli F, Padua R, Lupparelli S, Tonali P, Padua L. Intraneural cyst of the peroneal nerve. Childs Nerv Syst. 1998;14:222-225. 15. Johnston JA, Lyne DE. Intraneural ganglion cyst of the peroneal nerve in a four-year-old girl: a case report. J Pediatr Orthop. 2007;27:944-946. 16. Leijten FS, Arts WF, Puylaert JB. Ultrasound diagnosis of an intraneural ganglion cyst of the peroneal nerve. Case report. J Neurosurg. 1992;76:538-540. 17. Luigetti M, Sabatelli M, Montano N, Cianfoni A, Fernandez E. Lo Monaco M. Teaching neuroimages: peroneal intraneural ganglion cyst: a rare cause of drop foot in a child. Neurology. 2012;78:e46-e47.
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18. Nicholson TR, Cohen RC, Grattan-Smith PJ. Intraneural ganglion of the common peroneal nerve in a 4-year-old boy. J Child Neurol. 1995;10: 213-215. 19. Waldschmidt U, Slongo T. An unusual cause of paralysis of the peroneal nerve-a case report. J Pediatr Surg. 2010;45:259-261. 20. Spinner RJ, Vincent JF, Wolanskyj AP, Scheithauer BW. Intraneural ganglion cyst: a 200-yearold mystery solved. Clin Anat. 2008;21:611-618. 21. Spinner RJ, Wolanskyj AP. The arduous journey to find a portrait of Beauchêne fils: a famous anatomist and surgeon. Clin Anat. 2012;25:683-686. 22. Young NP, Sorenson EJ, Spinner RJ, Daube JR. Clinical and electrodiagnostic correlates of peroneal intraneural ganglia. Neurology. 2009;72:447-452.
23. Harbaugh KS, Tiel RL, Kline DG. Ganglion cyst involvement of peripheral nerves. J Neurosurg. 1997; 87:403-408.
Conflict of interest statement: The authors declare that the article content was composed in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. Received 1 July 2015; accepted 7 October 2015 Citation: World Neurosurg. (2016) 86:510.e11-510.e17. http://dx.doi.org/10.1016/j.wneu.2015.10.023 Journal homepage: www.WORLDNEUROSURGERY.org Available online: www.sciencedirect.com 1878-8750/$ - see front matter ª 2016 Elsevier Inc. All rights reserved.
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Intraneural Ganglia of the Common Peroneal Nerve in Children: Case Report and Review of the Literature Alessandro Consales1, Mattia Pacetti1, Alessia Imperato1, Maura Valle2, Armando Cama1
Key words Children - Cyst - Intraneural ganglia - Peroneal nerve - Surgery -
Abbreviations and Acronyms CPN: Common peroneal nerve DPN: Deep peroneal nerve EHL: Extensor hallucis longus muscle EMG: Electromyography IG: Intraneural ganglia MR: Magnetic resonance NCS: Nerve conduction studies PM: Peroneal muscles PN: Peroneal nerve TA: Tibialis anterior muscle TF: Tibiofibular US: Ultrasound From the Departments of 1Neurosurgery and 2Radiology, Istituto Giannina Gaslini, Genova, Italy To whom correspondence should be addressed: Alessandro Consales, M.D. [E-mail: [email protected]
- OBJECTIVES:
Intraneural ganglia are nonneoplastic cystic formations contained within the epineurium of peripheral nerves. The common peroneal nerve at the fibular neck is the most frequently affected site. Intraneural ganglia are not a frequent occurrence in the adult patients and are even rarer in children, with only 10 pediatric cases reported in the English language literature. We report on a new pediatric case of intraneural ganglion of common peroneal nerve and present a review of the English language literature on this topic in children.
- METHODS:
A 10-year-old girl was admitted to our institution because of pain referred to posterior and anterior aspects of the right leg and right foot drop. The radiologic investigations showed a wide (20 cm long) intraneural ganglion cyst of the right common peroneal nerve. The patient underwent surgical treatment according to the Spinner technique.
- RESULTS:
Postoperative course was uneventful. A gradual improvement of motor and sensory functions was observed, starting from the third postoperative day, with a complete motor function restoration registered 26 months after surgery.
- CONCLUSIONS:
Intraneural ganglia of the common peroneal nerve should always be considered in the differential diagnosis of foot drop in pediatric age since because early diagnosis and adequate surgical treatment play a crucial role in the patient’s motor and sensory outcomes.
Alessandro Consales and Mattia Pacetti are equally contributed. Citation: World Neurosurg. (2016) 86:510.e11-510.e17. http://dx.doi.org/10.1016/j.wneu.2015.10.023 Journal homepage: www.WORLDNEUROSURGERY.org Available online: www.sciencedirect.com 1878-8750/$ - see front matter ª 2016 Elsevier Inc. All rights reserved.
INTRODUCTION Intraneural ganglia (IG) are non-neoplastic, fluid-filled cystic formations contained within the epineurium of peripheral nerves. Although many peripheral nerves may be affected, the common peroneal nerve (CPN) at the fibular neck is by far the most frequently affected site.1-8 The pathogenesis of IG remained a controversial issue for a long time in the past, until a “unifying articular” or “synovial” theory was proposed by Spinner and colleagues.3,7,9 According to their theory, the formation of IG in peroneal nerve is a dynamic process starting in a degenerating superior tibiofibular (TF) joint and subsequently
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extending to the nerve along its articular branch intraepineurally via a path of least resistance determined by pressure fluxes. IG of the CPN are not a frequent occurrence in the adult population, prevailing in adult males, with a reported mean age of 34. They are even rarer in children.10-12 To our knowledge, only 10 pediatric cases of IG of the CPN have been reported in the English language literature.10,12-19 We report on a new pediatric case of intraneural ganglion of the CPN and present a review of the literature on this topic in pediatric age.
CASE REPORT History A 10-year-old girl was admitted to our observation on 13 July, 2008. Her clinical history began in April 2008. Immediately after a 2-hour flight, the patient complained of pain in the posterior aspect of the right leg, extending to the anterior aspect and
associated with slapping gait. She did not play any sport. No history of previous knee trauma was reported. The pain was reported as continuous, responding to nonsteroid anti-inflammatory drugs, and worsening in the supine position. It disappeared gradually in a few days, while the neurologic deficit persisted unchanged. The girl was examined by her family pediatrician and underwent diagnostic work-up at another institution, consisting of ultrasound (US) examination, magnetic resonance (MR) of the right lower limb, and electrophysiologic studies. On the first nerve conduction studies (NCS), made 3 weeks after the onset of symptoms, the right peroneal nerve motor study showed a decrease in amplitude of compound motor action potential (MAP) and in motor conduction velocity (MCV). It was confirmed by a second electrophysiologic evaluation, made 1 month later. The needle electromyography (EMG) study of the right anterior tibial muscle showed fibrillation
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potentials (grade þ1), motor unit action potentials of normal amplitude and duration but with irregular morphology, and a marked reduction of recruitment. There was electrophysiologic evidence of a subacute right common peroneal neuropathy. MR and US examination suggested the presence of a CPN tumor. Thus the patient was referred to our institution for diagnostic and therapeutic management. Examinations Neurologic examination revealed paralysis of dorsiflexion, eversion of right foot, and extension of right toes (grade 0/5 of muscle strength of tibialis anterior [TA], extensor hallucis longus [EHL], and peroneal muscles [PM]), resulting in foot drop and characteristic slapping gait. Moreover, sensory loss extending to the anterolateral surface of the lower leg and the dorsum of foot and toes was observed. MR performed at the other institution was considered useless due to patient movement artifacts. It was therefore repeated at our hospital, showing a wide (20-cm long) intraneural ganglion cyst of the right CPN (see Figures 1, AeD and 2, A for further explanations). The decision to perform surgical treatment of the ganglion cyst was made. Operation The patient underwent surgical treatment on 25 July, 2008. With the patient in the left lateral decubitus position, an enlarged CPN was exposed through a curved incision over the posterolateral aspect of the proximal leg, extending from the popliteal crease posteriorly, the fibular neck laterally, and then distally as far as the anterior compartment. Under loupe magnification and after opening of the peroneus longus muscle (PL) fascia, the CPN articular branch, deep peroneal nerve (DPN), and superficial peroneal nerve (SPN) were identified and mobilized. Next, the CPN articular branch was completely dissected and exposed up to the superior TF joint. The articular branch was completely enlarged along its course. Once cyst dissection was completed (Figure 3, A), the following surgical steps were performed as described by Spinner et al.7: 1) resection of
Figure 1. Preoperative magnetic resonance imaging (MRI) examination of the right knee using (A) T1-weighted, (B) fat-suppressed T2-weighted, and (C) gadolinium-enhanced T1-weighted sequences. They demonstrate a swollen, fluid-filled common peroneal nerve (arrow) reflecting intraneural involvement by a large ganglion cyst that expands cranially within the nerve substance from the level of the superior tibiofibular joint. Transverse, fat-suppressed tSE-T2w MRI of the distal thigh (D) reveals the intraneural ganglion of the peroneal nerve reaching the sciatic bifurcation. The cyst (1) entered the sciatic tracking the fascicles of the peroneal nerve. The tibial nerve and tibial component (2) of the sciatic bifurcation were totally unaffected. The longitudinal extension of the cyst in the sciatic was approximately 8 cm without cross-over paths.
the superior TF joint (when the capsule was penetrated, cyst fluid was seen; Figure 3, B); 2) disconnection of the articular branch from the superior TF joint by means of ligation and transection with preservation of the branch innervating the TA (Figure 3, C); 3) cyst decompression by means of limited longitudinal epineurotomy, performed away from the CPN fascicles previously identified intraoperatively with nerve stimulation. Abundant gelatinous material, released under some pressure, was evacuated (Figure 3, D). Finally, hemostasis was carried out and the wound was closed in anatomic layers with a subcuticular suture.
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Postoperative Course Postoperative course was uneventful. Three days postoperatively, some motor function was observed (right big toe extension: grade 1/5 of muscle strength). Physical therapy was started 2 weeks postoperatively. Postoperative MR was performed 3 months after surgery (see Figure 2, B). Four months after surgery, significant improvement of muscle strength (grade 3/5) of TA, EHL, and PM was observed. Moreover, concerning the sensory function, the light touch was restored. Seven months after surgery, further motor improvement of all previously mentioned muscles was observed (grade 4-/5 of
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Figure 2. Magnetic resonance neurography of the peroneal intraneural ganglion obtained (A) preoperatively and (B) postoperatively. In (A) the bulk of the ganglion (narrow arrow) is seen arising from the anterior aspect of the superior tibiofibular joint. The bulk of the ganglion communicates with the main trunk of the nerve (large arrow) through a long tubular process (arrowheads) representing the dilated articular branch of the peroneal nerve. (B) After ligation of the articular branch, fluid distension of the peroneal nerve is no longer appreciated.
muscle strength). Sensory function was completely normal. Physical therapy was continued until motor function was completely restored (grade 5/5 of muscle strength of TA, EHL, and PM) 26 months postoperatively. This clinical picture remained unchanged at the latest followup (6 years). DISCUSSION IG are non-neoplastic, fluid-filled cystic lesions contained within the epineurium of peripheral nerves. Many nerves may be affected; however, the CPN at the fibular neck is the most frequently affected site.1-8 First described by Beauchêne20,21 in 1810, IG affect predominantly male adults.11 The pathogenesis of these lesions was a matter of debate in the literature until the early 2000s. Starting from 2003, after reviewing a large cohort of patients and analyzing accurately the literature on the topic, Spinner and colleagues proposed, discussed, and substantiated the socalled “unified articular (synovial) theory”
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on the basis of clinical, anatomic, radiologic, and histologic data.1-9 According to this theory, the formation of intraneural ganglia is a dynamic process: Synovial fluid exits a neighboring capsular defect of a degenerating joint. Then, as Spinner et al. stated, “fluid tracks along the articular branch of a nerve intraepineurally via a path of least resistance along tissue planes” and “pressure fluxes determine the extent of dissection.”7 In CPN IG, the cyst fluid comes from the anterior portion of the superior TF joint, dissects tissue planes along the U-shaped articular branch, and finally reaches the deep peroneal portion of the CPN.6 In case of very high pressure, the cyst may extend more proximally up to the sciatic nerve.2 CPN IG are a rare entity and occur more frequently in adult male patients.11 Symptoms and signs include pain, motor, and/or sensory deficits in the CPN (DPN is particularly involved because of anatomic reasons) territory. A mass can be palpated in the anterolateral aspect of the knee. Moreover, the
Tinel sign can be elicited in the same region. History of knee trauma can also be present.7,22 EMG and nerve conduction studies (NCS) are useful to confirm CPN lesions (DPN lesions, more typically; however, also broader involvement of CPN and tibial division of sciatic nerve can occur7,22). Imaging studies (CT, US, MR) are important tools to make a correct preoperative diagnosis and to plan adequate surgical treatment. Among them, MR is the study of choice. It can show the cystic nature of the CPN lesion and its relationship with the superior TF joint. According to the unified articular theory, surgical treatment of CPN intraneural ganglia should be performed following these steps: 1) complete dissection of the cyst; 2) disarticulation, that is, resection of the superior TF joint to prevent extraneural cyst recurrence; 3) cyst decompression by means of limited epineurotomy to avoid neurologic injury; and 4) disconnection of CPN articular branch to prevent intraneural recurrence. Steps 2e4 can be carried out in any order.7 Concerning the outcome of patients affected by peroneal IG, it must be remarked that the best results are obtained in pain control.23 This is probably due to cyst decompression with consequent decrease in intraneural pressure.3,4 Motor recovery is less predictable. It may depend on several factors, including duration of symptoms, extent of compression, length of the cyst, neural anatomy of the TA, and intrinsic lower recovery ability of the PN compared with many other nerves.3,4 IG involving the only CPN in pediatric age are extremely rare. PubMed was searched for key words including intraneural ganglia, common peroneal nerve, and peroneal nerve cyst. Only studies in which patients younger than 16 years old could be indentified were included in our review. Using these selection criteria, only 10 pediatric cases were found to date in the English language literature.10,12-19 Clinical and radiologic findings of these cases are summarized in Table 1. The age range varied from 4e15 years. Motor deficit, progressive or sudden, was documented in all the patients. Sensory
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INTRANEURAL GANGLIA OF COMMON PERONEAL NERVE IN CHILDREN
cases (outcome not reported in one of these cases), with full motor recovery occurring from 2 weeks to 14 months (see Table 1).10,13,14 In our case, clinical onset was sudden, as in only one previously published case. Our patient showed complete motor recovery at 26 months and the clinical picture remained unchanged at the last visit, after the longest follow-up (6 years) documented to date for pediatric cases. This can indirectly confirm the value of the recommendation by Spinner and colleagues about the importance of performing 4 steps in the surgical treatment of IG.7 In particular, steps 2 and 4 are of paramount importance to avoid, respectively, extraneural and intraneural recurrence of the ganglia. The range of techniques used by other practitioners for CPN IG were considerably different than Spinner7 (see Table 1). However, the reported follow-up duration (see Table 1) was probably not sufficient to adequately evaluate surgical outcome in the long term. Only Waldschmidt and Slongo19 reported a long follow-up of 24 months. In their case, differently from Spinner’s technique, the surgical approach lacked disarticulation of the TF joint and disconnection of the CPN articular branch. Of note, recurrence was observed at 2 years of follow-up, even if the patient remained asymptomatic. Motor recovery after surgery in pediatric patients affected by IG of the CPN is generally better compared with adult patients. Our case confirms this trend. On the basis of the pertinent literature, the recovery of the sensory function is less predictable (see Table 1).10,12-19 Anyway, our patient had a full sensory recovery.
Figure 3. (A) Exposition of intraneural ganglion of the common peroneal nerve (CPN); see also the CPN articular branch (hollow arrowhead), superior tibiofibular joint (hollow arrow), the deep peroneal nerve (d), and the superficial peroneal nerve (s); (B) resection of the superior TF joint (arrow); (C) disconnection of the articular branch (arrow) from the superior TF joint; and (D) cyst decompression with release of gelatinous material (arrow).
CONCLUSION symptoms and signs are variable, as reported in adult patients. Two cases presented with a history of knee trauma12,13 and 5 with a palpable mass around the fibular neck.10,13,16,18,19 Early presentation of the clinical findings suggests a possible capsular laxity or defect. Every patient was operated after the diagnosis of intraneural cyst.
In 5 cases, a connection between the CPN articular branch and the superior TF joint was suspected at imaging and/or documented at surgery, requiring ligation, section, and disconnection of the nervous branch from the previously mentioned joint (see also Table 1).13-15,18 Neurologic outcome (strength) was excellent in 4 out of 10 previously published
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IG is an uncommon disease in adult age, and it is even rarer in children. Any nerve may be affected, but the CPN at the fibular neck is the most frequently affected side. IG of CPN should always be considered in the differential diagnosis of foot drop in pediatric age. Clinical features are similar in adults and in children, except for the outcome, which is better in children. Early diagnosis and treatment play a crucial role
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Authors & Year
Age (years), Sex
8, F Al Mufargi et al., 201113
Side Left
Clinical Findings Post-traumatic foot drop; palsy of foot dorsiflexion
Preoperative Neurophysiology
Radiology
Operation
Postoperative Neurophysiology
EMG: compressive lesion of US: hypoechogenic lesion over Cyst excision and articular CPN Not reported the PN at the fibular head the fibular head with suspected branch disruption connection with the proximal TF joint
Follow-up (weeks/ months)/Clinical Outcome 2 months/ complete motor recovery
Not Cystic swelling in the knee near EMG: mixed lesion of the reported the fibular head; progressive CPN at the fibular head foot drop; decreased sensation over the dorsum of the foot
US þ MR: cystic lesion communicating with the proximal TF joint
Aprin et al., 200710
4,5 M
Left
MR: 2 x 1,8 x 2, 5-cm cystic Nerve sheath incision, fluid mass at the fibular head, no drainage, cyst excision, TA and connection between the cyst and fascia incision the proximal TF joint
Aulisa et al., 199814
15, F
Not Sudden foot drop; intermittent reported knee pain; deficit of DPN muscles
NCS: slowing of conduction US þ MR: mass at the neck of Incision of the lesion and its Signs of in DPN; EMG: fp mild on TA the fibula excision from the nerve sheaths, rearrangement of and EHL, absent on PL; VA section of the stalk of motor unit potential absent on TA, normal on PL, connection with the proximal TF so on EHL joint
12 months/Full motor recovery and absence of sensory deficits
Johnston & Lyne, 200715
4, F
Left
Progressive foot deformity; mild leg atrophy; drop-foot gait; deficit of ankle dorsiflexion and great toe extension
NCS: prolonged latency of CPN at the knee. EMG: denervation in EDB, decreased recruitment in TA and EDB
12 months/ Improved strength (grade 4/5)
Leijten et al., 12, M 199216
Right
Foot drop; knee pain spreading EMG: marked conduction to the great toe; deficit of foot slowing at the head of the and toes extension and eversion; fibula hypoesthesia of the medial aspect of the foot and anesthesia of the great toe; string-like structure at the head of the fibula
Luigetti et al., 11, M 201217
Left
Progressive foot drop
Nicholson 4, M et al., 199518
Left
Deficit of foot eversion and dorsiflexion and of great toe extension; firm mass at the fibular neck
Foot drop; no ankle or great toe Not performed dorsiflexion; soft painful mass behind the neck of the fibula
Ganglion and articular nerve branch resection
MR: 4 x 1 cm cystic mass at the Nerve sheath incision, fluid fibular neck, connection (tail drainage, articular branch sign) between proximal TF joint ligation and transection and the cystic mass, anterior and lateral compartment muscles hyperintensity (denervation) US: 8 cm fusiform echolucent lesion along the CPN
Not reported
2 weeks/ Complete motor and sensory recovery
EMG (2 months): 14 months/full isolated motor recovery involvement of CPN with 63% reduction in amplitude
Not reported
1 month/No functional improvement (patient fitted with footextension device)
No signs of PN entrapment MR: CPN thickening (about 15 cm) and hyperintensity
Resection of the ganglion cyst
Not reported/mild improvement of the symptoms
NCS: no compound MAP US: hypoechoic mass around the from the CPN at ankle. EMG: neck of the fibula denervation on the PL and TA
Nerve sheath incision and cyst Not reported excision; adjunctive excision of a smaller cyst connecting the main cyst with the proximal TF joint
Not reported
6 months/ Improved global strength
CASE REPORT
Epineurium longitudinal incision Not reported and cyst excision with a sacrifice of about 40% of the nerve fascicles
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9, M
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Table 1. Intraneural Ganglia of the Common Peroneal Nerve in Children: Literature Review
CASE REPORT
EMG, electromyography; US, ultrasound; CPN, common peroneal nerve; MR, magnetic resonance; TF, tibiofibular; DPN, deep peroneal nerve; NCS, nerve conduction studies; Fp, Fibrillation potential; TA, tibialis anterior; EHL,extensor hallucis longus; PL, peroneus longus; VA, maximal voluntary activity; TA, tibialis anterior; EDB, extensor digitorum brevis; PN, peroneal nerve.
Left 12, M Waldschmidt and Slongo, 201019
Right
Progressive foot drop, PM and TA atrophy, foot pronation and dorsiflexion deficit, cystic mass at the fibular neck
EMG: loss of conductivity at MR: 4 cm mass at the fibular the fibular head; decreased neck amplitude of motoric sum potentials
Cyst opening and dismantling
Not reported
24 months/good recovery with minor deficit (9 months); recurrence at 24 months (pt. asymptomatic: no reoperation)
INTRANEURAL GANGLIA OF COMMON PERONEAL NERVE IN CHILDREN
Scherman 9, M et al., 198112
Post-traumatic knee swelling; EMG þ NCS: complete Not reported progressive foot drop; deficit of conduction block in the CPN foot and toes dorsiflexion and at the head of the fibula foot eversion; hypoesthesia along the medial aspect of the foot
1st surgery: small longitudinal Not reported cyst incision and fluid drainage; 2nd surgery: mass dissection and excision
Not reported
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in complete recovery of motor and sensory functions. REFERENCES 1. Spinner RJ, Amrami KK, Angius D, Wang H, Carmichael SW. Peroneal and tibial intraneural ganglia: correlation between intraepineurial compartments observed on magnetic resonance images and the potential importance of these compartments. Neurosurg Focus. 2007;22:E17. 2. Spinner RJ, Amrami KK, Wolanskyj AP, Desy NM, Wang H, Benarroch EE, et al. Dynamic phases of peroneal and tibial intraneural ganglia formation: a new dimension added to the unifying articular theory. J Neurosurg. 2007;107:296-307. 3. Spinner RJ, Atkinson JL, Scheithauer BW, Rock MG, Birch R, Kim TA, et al. Peroneal intraneural ganglia: the importance of the articular branch. Clinical series. J Neurosurg. 2003;99: 319-329. 4. Spinner RJ, Atkinson JL, Tiel RL. Peroneal intraneural ganglia: the importance of the articular branch. A unifying theory. J Neurosurg. 2003;99: 330-343. 5. Spinner RJ, Carmichael SW, Wang H, Parisi TJ, Skinner JA, Amrami KK. Patterns of intraneural ganglion cyst descent. Clin Anat. 2008;21:233-245. 6. Spinner RJ, Desy NM, Amrami KK. Cystic transverse limb of the articular branch: a pathognomonic sign for peroneal intraneural ganglia at the superior tibiofibular joint. Neurosurgery. 2006;59: 157-166. discussion 157-166. 7. Spinner RJ, Desy NM, Rock MG, Amrami KK. Peroneal intraneural ganglia. Part I. Techniques for successful diagnosis and treatment. Neurosurg Focus. 2007;22:E16. 8. Spinner RJ, Desy NM, Rock MG, Amrami KK. Peroneal intraneural ganglia. Part II. Lessons learned and pitfalls to avoid for successful diagnosis and treatment. Neurosurg Focus. 2007;22:E27. Review. 9. Spinner RJ, Scheithauer BW, Amrami KK. The unifying articular (synovial) origin of intraneural ganglia: evolution-revelation-revolution. Neurosurgery. 2009;65(suppl 4):A115-A124. 10. Aprin H, Weinberg J, Lustrin ES, Abrutyn D. Peroneal nerve palsy due to an intraneural ganglion: a case report of a 4 1/2-year-old boy. Am J Orthop (Belle Mead NJ). 2007;36:E40-E42. 11. Nucci F, Artico M, Santoro A, Bardella L, Delfini R, Bosco S, et al. Intraneural synovial cyst of the peroneal nerve: report of two cases and review of the literature [review] Neurosurgery. 1990; 26:339-344. 12. Scherman BM, Bilbao JM, Hudson AR, Briggs SJ. Intraneural ganglion: a case report with electron microscopic observations. Neurosurgery. 1981;8: 487-490. 13. Al Mufargi YS, Mouch CA, Ziebarth K, Joeris A, Slongo T. An unusual cause of paralysis of the peroneal nerve: a report of 3 cases. J Pediatr
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Orthop. 2011;31:e50e52. Retraction in: Hensinger RN, Thompson GH. J Pediatr Orthop. 2012;32:748. 14. Aulisa L, Tamburrelli F, Padua R, Lupparelli S, Tonali P, Padua L. Intraneural cyst of the peroneal nerve. Childs Nerv Syst. 1998;14:222-225. 15. Johnston JA, Lyne DE. Intraneural ganglion cyst of the peroneal nerve in a four-year-old girl: a case report. J Pediatr Orthop. 2007;27:944-946. 16. Leijten FS, Arts WF, Puylaert JB. Ultrasound diagnosis of an intraneural ganglion cyst of the peroneal nerve. Case report. J Neurosurg. 1992;76:538-540. 17. Luigetti M, Sabatelli M, Montano N, Cianfoni A, Fernandez E. Lo Monaco M. Teaching neuroimages: peroneal intraneural ganglion cyst: a rare cause of drop foot in a child. Neurology. 2012;78:e46-e47.
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18. Nicholson TR, Cohen RC, Grattan-Smith PJ. Intraneural ganglion of the common peroneal nerve in a 4-year-old boy. J Child Neurol. 1995;10: 213-215. 19. Waldschmidt U, Slongo T. An unusual cause of paralysis of the peroneal nerve-a case report. J Pediatr Surg. 2010;45:259-261. 20. Spinner RJ, Vincent JF, Wolanskyj AP, Scheithauer BW. Intraneural ganglion cyst: a 200-yearold mystery solved. Clin Anat. 2008;21:611-618. 21. Spinner RJ, Wolanskyj AP. The arduous journey to find a portrait of Beauchêne fils: a famous anatomist and surgeon. Clin Anat. 2012;25:683-686. 22. Young NP, Sorenson EJ, Spinner RJ, Daube JR. Clinical and electrodiagnostic correlates of peroneal intraneural ganglia. Neurology. 2009;72:447-452.
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Conflict of interest statement: The authors declare that the article content was composed in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. Received 1 July 2015; accepted 7 October 2015 Citation: World Neurosurg. (2016) 86:510.e11-510.e17. http://dx.doi.org/10.1016/j.wneu.2015.10.023 Journal homepage: www.WORLDNEUROSURGERY.org Available online: www.sciencedirect.com 1878-8750/$ - see front matter ª 2016 Elsevier Inc. All rights reserved.
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