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Localised hypertrophic mononeuropathy (LHM) as a complication of peripheral nerve decompression surgery
Clinical Neurology and Neurosurgery 112 (2010) 921–923
Contents lists available at ScienceDirect
Clinical Neurology and Neurosurgery journal homepage: www.elsevier.com/locate/clineuro
Case report
Localised hypertrophic mononeuropathy (LHM) as a complication of peripheral nerve decompression surgery Esther S.T. Ng a , Ter Chyan Tan b , Aravind K. Therimadasamy c , Einar Wilder-Smith a,∗ a
Department of Medicine, Yong Loo Lin School of Medicine, Singapore Department of Hand and Reconstructive Microsurgery, Yong Loo Lin School of Medicine, National University Health System, Singapore c Neurodiagnostic Laboratory, National University Health System, Singapore b
a r t i c l e
i n f o
Article history: Received 15 October 2009 Received in revised form 14 July 2010 Accepted 16 July 2010 Available online 21 August 2010
a b s t r a c t Localised hypertrophic mononeuropathy is the progressive enlargement of a large peripheral nerve, which can lead to profound loss of function. In this case report, we describe the postoperative occurrence of this phenomenon and possible ways to monitor for this condition. © 2010 Elsevier B.V. All rights reserved.
Keywords: Localised hypertrophic mononeuropathy Ulnar nerve surgery Decompression Neurolysis
1. Introduction Localised hypertrophic mononeuropathy is a rare slowly progressive enlargement of a single large peripheral nerve such as the peroneal, sciatic, median, ulnar or radial nerve [1]. It mainly occurs in those below the age of 40 and presents as weakness that progresses to profound loss of motor function with or without sensory involvement. Intraoperatively, a well defined fusiform mass is observed, and treatment options include neurolysis or excision with autologous nerve graft interposition. We present the first recorded case which developed after prior instrumentation to the nerve.
2. Case report In March 2008, a right-handed 13-year-old Chinese boy presented with a 1-year history of progressive numbness and weakness of his right hand. This was not associated with any pain. His main complaint was the inability to fully straighten his ulnar 2 fingers. There was no history of trauma or repetitive hand movements. There were no symptoms in his left hand. He was still able to write with his right hand.
∗ Corresponding author at: Neurology, National University Hospital, 5 Lower Kent Ridge Road, Singapore 119074, Singapore. Tel.: +65 6772 4362; fax: +65 6779 4112. E-mail address: [email protected] (E. Wilder-Smith). 0303-8467/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.clineuro.2010.07.016
On examination, there was high right ulnar claw of little finger and ring finger. In addition, there was wasting of the hypothenar muscles and weakness of the intrinsic muscles. Froment’s sign was positive, with positive Tinel’s sign over elbow. However, sensation was intact. Both sensory and motor ulnar nerve conduction studies showed absent responses. Magnetic Resonance Imaging showed mild non-specific gadolinium uptake of the nerve at the elbow. High resolution ultrasonography showed focal enlargement at the sulcus ulnaris without subluxation of the nerve. Cross-sectional area of the nerve was 0.11 cm2 at the sulcus ulnaris, compared to 0.03 cm2 3 cm above the medial epicondyle. Ultrasonography of the rest of the nerve revealed no abnormalities. The patient underwent surgical decompression of the nerve in May 2008. The nerve was only marginally enlarged at the sulcus compared to above the medial epicondyle (see Fig. 1). Decompression from the medial intermuscular septum to the two heads of Flexor Carpi Ulnaris was performed. As there was subluxation of the ulnar nerve post-decompression, the ulnar nerve was transposed and placed within a fascial sling created from the fascia over the flexor pronator muscles. There was no observed point where the nerve could be kinked when the elbow was ranged through its full range of motion. After operation, the interossei and hypothenar muscles remained wasted. However the 1st dorsal interosseous muscle regained some bulk and power. His claw hand was less pronounced and the patient was able to actively abolish clawing of the ulnar two fingers suggesting recovery of ulnar intermetacarpal intrinsics and
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E.S.T. Ng et al. / Clinical Neurology and Neurosurgery 112 (2010) 921–923
Fig. 3. Enlarged ulnar nerve above the elbow. Fig. 1. Hypertrophic ulnar nerve at the elbow.
hypothenar muscles. He was able to regain sufficient function to resume his hobby of classical guitar playing. He was followed up in the outpatient clinic on a 3 monthly basis. In the first 2 visits good improvement was noted however subsequent visits showed a plateau in recovery. There was no further increase in muscle bulk of the intrinsic muscles and the hand sensation remained the same. There was however no recurrence of the claw position. 9 months after the operation, a distinct Tinel’s sign developed, 2–3 cm above the medial epicondyle in the line of the repositioned nerve. This was persistent and grew more pronounced in the following visits. Repeat NCS in March 2009 showed absent sensory nerve conduction and small amplitude motor potentials consistent with persistent severe right ulnar neuropathy. Repeat ultrasound of the nerve showed continued enlargement of the ulnar nerve above the medial epicondyle, with cross-sectional area of 0.20 cm2 3 cm above the medial epicondyle compared to 0.05 cm2 at the sulcus (see Fig. 2). The patient underwent re-exploration of the ulnar nerve in June 2009, which showed severe traction and compression distal to the medial epicondyle segment up to the 2 heads of the FCU. There was paucity of vessels with scar adhesions over the ulnar nerve radiating to the surrounding tissue in a longitudinal fashion. There was nerve enlargement in the proximal segment with dilatation of vasa nevorum consistent with the pattern seen in the ultrasound (Fig. 3). The nerve was stable in flexion and extension, with no subluxation.
Fig. 2. Ultrasonography of the ulnar nerve 3 cm above the medial epicondyle.
The nerve was explored proximally up to 7 cm above the medial epicondyle and distally to the two heads of the flexor carpi ulnaris. It was mobilised proximally and distally but not at the medial epicondyle. Epineural endoneurolysis was performed distal to medial epicondyle to release the adhesions found encasing the nerve. To prevent further motor axonal loss, no biopsy was performed. After the second operation, the static Tinel’s sign was abolished, with the Tinel’s sign now progressing towards the ulnar aspect of his right hand, indicating good recovery. Intrinsic muscle power was improved at last follow-up April 2010 (Medical Research Council grade 4). 3. Discussion Localised hypertrophic mononeuropathy (LHM) has been postulated to be a result of trauma. Johnson et al found traumatic neuroma foci in 2 of his cases. However, an alternative explanation for the presence of neuromatous foci could be that the expanding mass of the hypertrophic nerve may in itself be the injuring entity. In previous case studies, the nerve had already hypertrophied at initial presentation, making it difficult to draw conclusions on causality [2–4]. This is the first documented case where LHM occurred after prior instrumentation to the nerve. At the first operation, there was only mild focal swelling at the sulcus ulnaris compatible with cubital tunnel syndrome. The nerve was transposed, and placed on the flexor pronator muscle mass. Over a time course of 1 year, he developed a fusiform nerve enlargement proximal to the medial epicondyle. He underwent a rapid growth phase consistent with puberty in this timeframe, growing a total of 10 cm in height during that 1 year. Due to his rapid growth, we postulate that there was a traction force applied to the nerve. We postulate that it was tethered and compressed by the scar tissue present after the first operation, likely resulting in the hypertrophy observed at the second operation. This can be explained via 2 mechanisms. The first has been postulated by previous authors—focal disruption of the perineural component of the blood nerve barrier resulting in proliferative stimulus to perineural cells [3]. We also hypothesise that this hypertrophy may be due to axoplasmic damming, which has previously been demonstrated by electron microscopy on single neurons [5]. However, intraneural perineurioma is a well-known cause of LHM in puberty and the possibility of his LHM being unrelated to the surgery should not be considered definitely ruled out [6]. Some previous authors have used intraoperative nerve conduction studies to decide on surgical management [6–8]. Where axonal continuity through the lesion was demonstrated, a conservative approach (neurolysis) was used, while failure to demonstrate axonal continuity through the lesion prompted resection or biopsy.
E.S.T. Ng et al. / Clinical Neurology and Neurosurgery 112 (2010) 921–923
We chose to perform neurolysis for our patient based on the fact that small amplitude motor potentials were still present. He has so far shown good recovery. However, in some patients, the natural progression of the disease still requires them undergoing nerve resection and grafting [3]. We are continuing to monitor our patient with nerve conduction studies and high resolution ultrasonography. This case highlights the importance of follow-up after peripheral nerve surgery in children, to detect unexpected postoperative complications, especially in patients with slow recovery or persistent symptoms. We feel that ultrasonography, coupled with electrophysiology, is an ideal method to monitor these patients. It is sensitive, non-invasive, and can examine in detail structural aspects of the nerve—including surrounding bone and soft tissue. Hence, it would be able to detect focal pathology and the possible cause, enabling the surgeon to plan the operation more effectively.
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References [1] Koszyca B, Jones N, Kneebone C, Blumbergs P. Localized hypertrophic neuropathy: a case report and review of the literature. Clin Neuropathol 2009;28((January–February) 1):54–8. [2] Gruen P, Kline DG. Hypertrophic mononeuropathy. Neurosurg Focus 2007; 22 (2207):23 [Review]. [3] Phillips 2nd LH, Persing JA, Vandenberg SR. Electrophysiological findings in localized hypertrophic mononeuropathy. Muscle Nerve 1991;14:335– 41. [4] Johnson PC, Kline DG. Localized hypertrophic neuropathy: possible focal perineural barrier defect. Acta Neuropathol 1989;77:514–8 [Review]. [5] Weiss PA. Neuronal dynamics and axonal flow V. The semisolid state of the moving axonal column. Proc Natl Acad Sci U S A 1972;69:620–3. [6] Iyer VG, Garretson HD, Byrd RP, Reiss SJ. Localized hypertrophic mononeuropathy involving the tibial nerve. Neurosurgery 1988;23:18–22. [7] Simpson DA, Fowler M. Two cases of localized hypertrophic neurofibrosis. J Neurol Neurosurg Psychiatry 1966;29:80–4. [8] Snyder M, Cancilla PA, Batzdorf U. Hypertrophic neuropathy simulating a neoplasm of the brachial plexus. Surg Neurol 1977;7:131–4.
Contents lists available at ScienceDirect
Clinical Neurology and Neurosurgery journal homepage: www.elsevier.com/locate/clineuro
Case report
Localised hypertrophic mononeuropathy (LHM) as a complication of peripheral nerve decompression surgery Esther S.T. Ng a , Ter Chyan Tan b , Aravind K. Therimadasamy c , Einar Wilder-Smith a,∗ a
Department of Medicine, Yong Loo Lin School of Medicine, Singapore Department of Hand and Reconstructive Microsurgery, Yong Loo Lin School of Medicine, National University Health System, Singapore c Neurodiagnostic Laboratory, National University Health System, Singapore b
a r t i c l e
i n f o
Article history: Received 15 October 2009 Received in revised form 14 July 2010 Accepted 16 July 2010 Available online 21 August 2010
a b s t r a c t Localised hypertrophic mononeuropathy is the progressive enlargement of a large peripheral nerve, which can lead to profound loss of function. In this case report, we describe the postoperative occurrence of this phenomenon and possible ways to monitor for this condition. © 2010 Elsevier B.V. All rights reserved.
Keywords: Localised hypertrophic mononeuropathy Ulnar nerve surgery Decompression Neurolysis
1. Introduction Localised hypertrophic mononeuropathy is a rare slowly progressive enlargement of a single large peripheral nerve such as the peroneal, sciatic, median, ulnar or radial nerve [1]. It mainly occurs in those below the age of 40 and presents as weakness that progresses to profound loss of motor function with or without sensory involvement. Intraoperatively, a well defined fusiform mass is observed, and treatment options include neurolysis or excision with autologous nerve graft interposition. We present the first recorded case which developed after prior instrumentation to the nerve.
2. Case report In March 2008, a right-handed 13-year-old Chinese boy presented with a 1-year history of progressive numbness and weakness of his right hand. This was not associated with any pain. His main complaint was the inability to fully straighten his ulnar 2 fingers. There was no history of trauma or repetitive hand movements. There were no symptoms in his left hand. He was still able to write with his right hand.
∗ Corresponding author at: Neurology, National University Hospital, 5 Lower Kent Ridge Road, Singapore 119074, Singapore. Tel.: +65 6772 4362; fax: +65 6779 4112. E-mail address: [email protected] (E. Wilder-Smith). 0303-8467/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.clineuro.2010.07.016
On examination, there was high right ulnar claw of little finger and ring finger. In addition, there was wasting of the hypothenar muscles and weakness of the intrinsic muscles. Froment’s sign was positive, with positive Tinel’s sign over elbow. However, sensation was intact. Both sensory and motor ulnar nerve conduction studies showed absent responses. Magnetic Resonance Imaging showed mild non-specific gadolinium uptake of the nerve at the elbow. High resolution ultrasonography showed focal enlargement at the sulcus ulnaris without subluxation of the nerve. Cross-sectional area of the nerve was 0.11 cm2 at the sulcus ulnaris, compared to 0.03 cm2 3 cm above the medial epicondyle. Ultrasonography of the rest of the nerve revealed no abnormalities. The patient underwent surgical decompression of the nerve in May 2008. The nerve was only marginally enlarged at the sulcus compared to above the medial epicondyle (see Fig. 1). Decompression from the medial intermuscular septum to the two heads of Flexor Carpi Ulnaris was performed. As there was subluxation of the ulnar nerve post-decompression, the ulnar nerve was transposed and placed within a fascial sling created from the fascia over the flexor pronator muscles. There was no observed point where the nerve could be kinked when the elbow was ranged through its full range of motion. After operation, the interossei and hypothenar muscles remained wasted. However the 1st dorsal interosseous muscle regained some bulk and power. His claw hand was less pronounced and the patient was able to actively abolish clawing of the ulnar two fingers suggesting recovery of ulnar intermetacarpal intrinsics and
922
E.S.T. Ng et al. / Clinical Neurology and Neurosurgery 112 (2010) 921–923
Fig. 3. Enlarged ulnar nerve above the elbow. Fig. 1. Hypertrophic ulnar nerve at the elbow.
hypothenar muscles. He was able to regain sufficient function to resume his hobby of classical guitar playing. He was followed up in the outpatient clinic on a 3 monthly basis. In the first 2 visits good improvement was noted however subsequent visits showed a plateau in recovery. There was no further increase in muscle bulk of the intrinsic muscles and the hand sensation remained the same. There was however no recurrence of the claw position. 9 months after the operation, a distinct Tinel’s sign developed, 2–3 cm above the medial epicondyle in the line of the repositioned nerve. This was persistent and grew more pronounced in the following visits. Repeat NCS in March 2009 showed absent sensory nerve conduction and small amplitude motor potentials consistent with persistent severe right ulnar neuropathy. Repeat ultrasound of the nerve showed continued enlargement of the ulnar nerve above the medial epicondyle, with cross-sectional area of 0.20 cm2 3 cm above the medial epicondyle compared to 0.05 cm2 at the sulcus (see Fig. 2). The patient underwent re-exploration of the ulnar nerve in June 2009, which showed severe traction and compression distal to the medial epicondyle segment up to the 2 heads of the FCU. There was paucity of vessels with scar adhesions over the ulnar nerve radiating to the surrounding tissue in a longitudinal fashion. There was nerve enlargement in the proximal segment with dilatation of vasa nevorum consistent with the pattern seen in the ultrasound (Fig. 3). The nerve was stable in flexion and extension, with no subluxation.
Fig. 2. Ultrasonography of the ulnar nerve 3 cm above the medial epicondyle.
The nerve was explored proximally up to 7 cm above the medial epicondyle and distally to the two heads of the flexor carpi ulnaris. It was mobilised proximally and distally but not at the medial epicondyle. Epineural endoneurolysis was performed distal to medial epicondyle to release the adhesions found encasing the nerve. To prevent further motor axonal loss, no biopsy was performed. After the second operation, the static Tinel’s sign was abolished, with the Tinel’s sign now progressing towards the ulnar aspect of his right hand, indicating good recovery. Intrinsic muscle power was improved at last follow-up April 2010 (Medical Research Council grade 4). 3. Discussion Localised hypertrophic mononeuropathy (LHM) has been postulated to be a result of trauma. Johnson et al found traumatic neuroma foci in 2 of his cases. However, an alternative explanation for the presence of neuromatous foci could be that the expanding mass of the hypertrophic nerve may in itself be the injuring entity. In previous case studies, the nerve had already hypertrophied at initial presentation, making it difficult to draw conclusions on causality [2–4]. This is the first documented case where LHM occurred after prior instrumentation to the nerve. At the first operation, there was only mild focal swelling at the sulcus ulnaris compatible with cubital tunnel syndrome. The nerve was transposed, and placed on the flexor pronator muscle mass. Over a time course of 1 year, he developed a fusiform nerve enlargement proximal to the medial epicondyle. He underwent a rapid growth phase consistent with puberty in this timeframe, growing a total of 10 cm in height during that 1 year. Due to his rapid growth, we postulate that there was a traction force applied to the nerve. We postulate that it was tethered and compressed by the scar tissue present after the first operation, likely resulting in the hypertrophy observed at the second operation. This can be explained via 2 mechanisms. The first has been postulated by previous authors—focal disruption of the perineural component of the blood nerve barrier resulting in proliferative stimulus to perineural cells [3]. We also hypothesise that this hypertrophy may be due to axoplasmic damming, which has previously been demonstrated by electron microscopy on single neurons [5]. However, intraneural perineurioma is a well-known cause of LHM in puberty and the possibility of his LHM being unrelated to the surgery should not be considered definitely ruled out [6]. Some previous authors have used intraoperative nerve conduction studies to decide on surgical management [6–8]. Where axonal continuity through the lesion was demonstrated, a conservative approach (neurolysis) was used, while failure to demonstrate axonal continuity through the lesion prompted resection or biopsy.
E.S.T. Ng et al. / Clinical Neurology and Neurosurgery 112 (2010) 921–923
We chose to perform neurolysis for our patient based on the fact that small amplitude motor potentials were still present. He has so far shown good recovery. However, in some patients, the natural progression of the disease still requires them undergoing nerve resection and grafting [3]. We are continuing to monitor our patient with nerve conduction studies and high resolution ultrasonography. This case highlights the importance of follow-up after peripheral nerve surgery in children, to detect unexpected postoperative complications, especially in patients with slow recovery or persistent symptoms. We feel that ultrasonography, coupled with electrophysiology, is an ideal method to monitor these patients. It is sensitive, non-invasive, and can examine in detail structural aspects of the nerve—including surrounding bone and soft tissue. Hence, it would be able to detect focal pathology and the possible cause, enabling the surgeon to plan the operation more effectively.
923
References [1] Koszyca B, Jones N, Kneebone C, Blumbergs P. Localized hypertrophic neuropathy: a case report and review of the literature. Clin Neuropathol 2009;28((January–February) 1):54–8. [2] Gruen P, Kline DG. Hypertrophic mononeuropathy. Neurosurg Focus 2007; 22 (2207):23 [Review]. [3] Phillips 2nd LH, Persing JA, Vandenberg SR. Electrophysiological findings in localized hypertrophic mononeuropathy. Muscle Nerve 1991;14:335– 41. [4] Johnson PC, Kline DG. Localized hypertrophic neuropathy: possible focal perineural barrier defect. Acta Neuropathol 1989;77:514–8 [Review]. [5] Weiss PA. Neuronal dynamics and axonal flow V. The semisolid state of the moving axonal column. Proc Natl Acad Sci U S A 1972;69:620–3. [6] Iyer VG, Garretson HD, Byrd RP, Reiss SJ. Localized hypertrophic mononeuropathy involving the tibial nerve. Neurosurgery 1988;23:18–22. [7] Simpson DA, Fowler M. Two cases of localized hypertrophic neurofibrosis. J Neurol Neurosurg Psychiatry 1966;29:80–4. [8] Snyder M, Cancilla PA, Batzdorf U. Hypertrophic neuropathy simulating a neoplasm of the brachial plexus. Surg Neurol 1977;7:131–4.