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Lesser occipital nerve damage after retrosigmoid craniotomy repaired with processed nerve allograft
Interdisciplinary Neurosurgery 19 (2020) 100592
Contents lists available at ScienceDirect
Interdisciplinary Neurosurgery journal homepage: www.elsevier.com/locate/inat
Case Reports & Case Series
Lesser occipital nerve damage after retrosigmoid craniotomy repaired with processed nerve allograft
T
⁎
John P. Andrews , Michael McDermott, Line Jacques University of California-San Francisco, Department of Neurological Surgery, USA
A R T I C LE I N FO
A B S T R A C T
Keywords: Retrosigmoid craniotomy Retrosigmoid incision Lesser occipital nerve Nerve graft, Occipital neuralgia
Background and importance: The retrosigmoid approach provides a robust corridor to cerebellopontine angle (CPA) pathology, but postoperative headache syndromes can cause significant patient distress. The lesser occipital nerve (LON) is in danger of injury during a retrosigmoid approach, and LON injury may present as occipital neuralgia with hypesthesia, dysesthesia and/or allodynia in the distribution of the LON. There are a number of treatment alternatives for refractory occipital neuralgia, but LON repair with processed nerve allograft has not previously been reported. Clinical presentation: A 42-year-old female was referred to peripheral nerve clinic for neuropathic pain, numbness and discomfort in a right LON distribution. Her history was significant for right retrosigmoid craniotomy for fenestration of a symptomatic CPA arachnoid cyst 2.5 years prior. Exam was significant for allodynia and reduced sensation. Exploration of the retrosigmoid incision revealed a damaged, scarred down LON. The nerve was trimmed and a 3 cm cadaveric, processed nerve allograft was interposed between the proximal and distal segments, secured without tension. The patient exhibited improvement in her neuropathic pain at follow-up. Conclusion: LON injury during retrosigmoid craniotomy can lead to occipital neuralgia and significant patient distress. Surgeons should be aware of the LON’s course relative to retrosigmoid incisions. Repair of the injured nerve with processed cadaveric nerve allograft deserves continued investigation for treating LON damage.
1. Background and importance The retrosigmoid approach provides a robust corridor to cerebellopontine angle (CPA) pathology, but carries high rates of postoperative headache syndromes [1–7]. There are multiple possible etiologies of the postoperative headache, including scalp adhesions to dura, cerebrospinal fluid leak, aseptic meningitis, and occipital nerve damage [4,7,8]. Occipital neuralgia involves pain in the distribution of the greater or lesser occipital nerves, characterized by lancinating or paroxysmal pain over the affected nerve, and may also feature Tinel’s sign and sensory changes [9,10]. During a retrosigmoid approach, the greater or lesser occipital nerves may be damaged either during incision, or secondarily from retraction of the tissue [2,7]. The lesser occipital nerve (LON) may lie in the path of the retrosigmoid incision, putting it in danger of incisional damage [11]. The incidence of occipital neuralgia from retrosigmoid craniotomy is unclear, but in one study of 113 patients who underwent acoustic neuroma surgery, 30 reported postoperative headache, of whom 5 had a pain syndrome fitting with occipital neuralgia [2]. One report of a
technique to preserve the LON during a suboccipital approach showed results suggesting that that preservation of the LON might significantly reduce postoperative occipital pain and sensory changes [11]. While prevention of nerve damage is optimal, a number of possible treatments for occipital neuralgia are in practice. Injection of local anesthetic can be both diagnostic and therapeutic, although the benefit is temporary [6]. Surgical interventions for refractory occipital neuralgia include neurectomy, neurolysis, radiofrequency ablation, posterior rhizotomy, peripheral nerve stimulation and C2-3 root decompression [12]. Nerve allograft interposition has been used with success for repair of injury to sensory, motor and mixed peripheral nerves [13,14]. To our knowledge, there have been no reports of cadaveric processed nerve allograft interposition being used for repair of the LON. 2. Clinical presentation 2.1. Patient information and clinical findings A 42-year-old female was referred to peripheral nerve clinic for
⁎ Corresponding author at: University of California, San Francisco, Department of Neurological Surgery, 505 Parnassus Ave Suite M779, San Francisco, CA 94143, USA. E-mail address: [email protected] (J.P. Andrews).
https://doi.org/10.1016/j.inat.2019.100592 Received 8 October 2019; Accepted 12 October 2019 2214-7519/ © 2019 Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/BY-NC-ND/4.0/).
Interdisciplinary Neurosurgery 19 (2020) 100592
J.P. Andrews, et al.
Fig. 1. Timeline. The patient originally presented with persistent nausea, vomiting and headaches in 2016. MRI showed right cerebellopontine angle arachnoid cyst causing brainstem compression. The patient underwent right retrosigmoid craniotomy for cyst fenestration, which relieved the presenting symptoms. Subsequently, the patient reported persistent numbness and dysesthesia in a lesser occipital nerve distribution, which was refractory to medical management. In 2019, she was taken to the operating room for exploration of her retrosigmoid incision and nerve repair.
Fig. 2. Surgical view of the left-sided C-shaped craniotomy incision re-opened for exploration and repair. The top of the pane is superior and the bottom is inferior. A) The damaged lesser occipital nerve (LON) is depicted, with distal (top) and proximal (bottom) aspects of the nerve isolated with vessel loops. The nerve clearly shows disruption and scarring down to the underlying titanium mesh. B) Post-repair, the graft is seen connecting the formerly discontinuous segments of the LON, secured without tension using 8-0 polypropylene sutures.
neuropathic pain in a right lesser occipital nerve distribution, which the patient reported causing significant distress. Her history was significant for right retrosigmoid craniotomy for fenestration of a symptomatic CPA arachnoid cyst 2.5 years prior (Fig. 1). The bone flap was replaced and secured using titanium plating during that surgery. Medical history was otherwise unremarkable. The patient reported persistent numbness and dysesthesia in right occipital distribution, including her incision site. These symptoms were refractory to pharmacologic management with common analgesics. On exam, she had allodynia over the midline of the retrosigmoid incision, a positive Tinel’s sign and dysesthesia over the sensory distribution of the right LON.
explored surgically and repaired using a processed cadaveric nerve allograft. Persistent headache syndromes following a retrosigmoid approach are well-documented phenomena. A number of procedural-based explanations have been proposed to underlie postoperative headache following such an approach [3,4]. Some of these include dural adhesions to scalp when bone flap is not replaced, drilling of the auditory meatis, and aseptic meningitis. For the patient discussed here, the bone flap was replaced during the first surgery, the internal auditory meatus was not drilled, and the postoperative pain syndrome was not consistent with aseptic meningitis. The observation of clearly damaged, scarred and thinned LON during surgical exploration of the wound, combined with the ipsilateral (unilateral) posterior sensory changes and pain in the distribution of the LON is highly suggestive of LON injury as the causal etiology. The LON originates primarily from the posterior rami of C2 (sometimes of C3) and pierces the superficial cervical plexus at the posterior border of the sternocleidomastoid (Fig. 3) [15]. A cadaveric study of 30 LON’s found that it emerges from behind the sternocleidomastoid roughly 5 ( ± 1.5) cm inferior to a line connecting bilateral external acoustic canals, and on average 6.5 ( ± 1.1) cm lateral to midline [15,16]. Cadaver studies suggest the LON ascends to the calvarium between 3 and 9 cm from midline [15,17], in a groove that may be palpated approximately two-thirds of the distance from the external occipital protuberance to the mastoid on the superior nuchal line [15,18]. Various incisions are used for retrosigmoid craniotomy, but no incision technique is certain to spare the LON (Fig. 3). The best way to avoid nerve damage may be careful dissection, identification and sparing of the LON during incision. In the treatment of painful neuroma, there is currently no unambiguous superior surgical treatment for neuroma pain [19]. When symptoms of occipital neuralgia are refractory to pharmacologic or non-invasive procedures, surgical treatment may be considered. Two examples of such treatments are peripheral nerve stimulation or neurectomy. Peripheral nerve stimulation for occipital neuralgia has been shown to be safe and effective [20,21]. A two-stage procedure can be employed, where electrodes are initially placed percutaneously through a guide-needle to attain a position over the greater or lesser occipital nerve targets. Stimulation can then be optimized prior to final surgical implantation. An inherent disadvantage of peripheral nerve stimulation
2.2. Therapeutic intervention Given the nature and location of the pain, as well of the history of retrosigmoid craniotomy, laceration of the LON during retrosigmoid incision with neuroma formation was suspected. Nerve laceration weighed against the use of peripheral nerve neurostimulation, so neuroma excision with possible nerve repair was considered. After discussing options, risks and benefits with the patient, she opted for neuroma excision with possible nerve repair. On the day of surgery, the patient was positioned supine, with her right shoulder elevated by a cushion and her head turned to the left. The prior C-shaped retrosigmoid incision was opened sharply and blunt dissection was used to identify the right proximal and distal aspects of the LON, which were isolated using vessel loops (Fig. 2A). At the level of the mesh plate—co-incident with the site of the patient’s Tinel sign—the nerve appeared to have been cut, and was scarred down. The LON was trimmed sharply at proximal and distal ends of the frayed portion, and these specimens were sent to pathology. Subsequently, a 3 cm processed cadaveric nerve allograft was interposed between the previously identified LON segments. The graft was secured without tension using two 8-0 polypropylene sutures at each site of anastomosis (Fig. 2B). The wound was then irrigated with bacitracin and hemostasis was achieved before closure. Pathology confirmed the diagnosis of neuroma. 2.3. Follow-up and outcomes At 2 months follow-up, dysesthesia was no longer present on physical exam, nor was there tenderness to palpation over the incision. 3. Discussion We report a case of occipital neuralgia following a retrosigmoid craniotomy, due to damage to the lesser occipital nerve, which was 2
Interdisciplinary Neurosurgery 19 (2020) 100592
J.P. Andrews, et al.
Fig. 3. Diagrams of 4 common incisions for a retrosigmoid approach, overlaid on relevant boney and neurovascular anatomy. As can be seen, all incisions put the LON at risk at some point in the course of the nerve. GON = Greater occipital nerve; TvS = Transverse Sinus; LON = Lesser occipital nerve; GAS = Great auricular nerve.
Acknowledgements
includes the presence of an implanted device, which may serve as a nidus for infection. The device will also eventually necessitate additional procedures for battery change. Moreover, rates of revision or electrode migration have been reported as over 30% [22]. Neurectomy and burying of the distal end of the damaged nerve into muscle is another treatment with therapeutic benefit. This tactic does not prevent neuroma formation, but rather the muscle supplies padding to the distal end of the damaged nerve [19,23]. Nerve function is neither rescued nor reassigned, but simply insulated. This is in contrast to a technique like targeted muscle reinnervation (TMR), in which a muscle is denervated before implantation of a rarified nerve tip [19,24]. TMR has also showed promise for reducing neuropathic pain of traumatic etiology, and in the future may be a good option for treatment of cases similar to the one discussed here [19]. The mechanisms of neuropathic pain following nerve injury are an area of ongoing investigation [25]. There is evidence to support spontaneous activity of these injured nerve fibers contributes to the neuropathic pain phenotype, and that allowing the nerve to re-form native (or native-like) connections might allay some pain symptoms [19,26,27]. Advances in repair of peripheral nerves have sought to use synthetic or processed alternatives to autografting [28,29]. Allograft, as opposed to autograft, avoids donor-site morbidity, such as new areas of sensory loss and donor-site pain [30]. Processed nerve allografts are a viable option for peripheral nerve repair, which avoid a donor site, while also not requiring immunosuppression that would be required for classic allografting with cellular elements intact [14]. Nerve allograft interposition has been used with some success in lower limb neuroma treatment and are a promising technique aimed at allowing a damaged peripheral nerve to reform native connections [27]. We report here a case of LON injury due to retrosigmoid craniotomy, repaired using a processed cadaveric nerve allograft. Followup is yet too preliminary to make strong recommendations based on this single case, but the intervention fits with a framework of treating neuroma restoring the injured nerve to as close a semblance of native connectivity as possible.
The authors would like to thank Kenneth X. Probst, Department of Neurological Surgery illustrator, for the manuscript artwork of Fig. 3. Conflict of interest None. Disclosure of funding None. Consent Patient consent was obtained prior to the submission of this manuscript. No IRB/ethics committee approval was required for this report. References [1] D.A. Schessel, J.M. Nedzelski, D. Rowed, J.G. Feghali, Pain after surgery for acoustic neuroma, Otolaryngol.—Head Neck Surg. 107 (3) (1992) 424–429. [2] C. Schankin, C. Gall, A. Straube, Headache syndromes after acoustic neuroma surgery and their implications for quality of life, Cephalalgia 29 (7) (2009) 760–771. [3] A. Sabab, J. Sandhu, S. Bacchi, A. Jukes, A. Zacest, Postoperative headache following treatment of vestibular schwannoma: a literature review, J. Clin. Neurosci. 52 (2018) 26–31. [4] B. Schaller, A. Baumann, Headache after removal of vestibular schwannoma via the retrosigmoid approach: a long-term follow-up-study, Otolaryngol.-Head Neck Surg. 128 (3) (2003) 387–395. [5] S.F. Ansari, C. Terry, A.A. Cohen-Gadol, Surgery for vestibular schwannomas: a systematic review of complications by approach, Neurosurg. Focus 33 (3) (2012) E14. [6] I. Ducic, J.M. Felder III, M. Endara, Postoperative headache following acoustic neuroma resection: occipital nerve injuries are associated with a treatable occipital neuralgia, Headache 52 (7) (2012) 1136–1145. [7] M.K. Teo, M.S. Eljamel, Role of craniotomy repair in reducing postoperative headaches after a retrosigmoid approach, Neurosurgery 67 (5) (2010) 1286–1292. [8] T.J. Lovely, The treatment of chronic incisional pain and headache after retromastoid craniectomy, Surg. Neurol. Int. 3 (2012). [9] W.F. Kuhn, S.C. Kuhn, H. Gilberstadt, Occipital neuralgias: clinical recognition of a complicated headache. A case series and literature review, J. Orofacial Pain 11 (2) (1997). [10] P. Vanelderen, A. Lataster, R. Levy, N. Mekhail, M. Van Kleef, J. Van Zundert, 8. Occipital neuralgia, Pain Practice 10 (2) (2010) 137–144. [11] F. Takamitsu, S. Jae-Hyun, T. Shigehiko, I. Teruyuki, F. Kazuhide, M. Toshihiro, et al., Preservation of the lesser occipital nerve during microvascular decompression for hemifacial spasm, J. Neurosurg. JNS 107 (6) (2007) 1235–1237 English. [12] R.R. Sharma, R.V. Devadas, S.J. Pawar, S.D. Lad, A.K. Mahapatra, Current status of
4. Conclusion Retrosigmoid craniotomy can lead to LON injury causing significant patient distress. To avoid the morbidity of nerve injury, surgeons should be aware of the course of the LON and spare it if possible during retrosigmoid incision. Repair of the traumatized nerve with processed cadaveric nerve allograft is a technique for treating LON neuroma that deserves continued investigation. 3
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[21] D.W. Dodick, S.D. Silberstein, K.L. Reed, T.R. Deer, K.V. Slavin, B. Huh, et al., Safety and efficacy of peripheral nerve stimulation of the occipital nerves for the management of chronic migraine: long-term results from a randomized, multicenter, double-blinded, controlled study, Cephalalgia 35 (4) (2015) 344–358. [22] S. Falowski, D. Wang, A. Sabesan, A. Sharan, Occipital nerve stimulator systems: review of complications and surgical techniques, Neuromodulation 13 (2) (2010) 121–125. [23] J. Bajaj, S.C. Dulebohn, Migraine, Surgical Interventions, StatPearls [Internet]: StatPearls Publishing, 2018. [24] T.A. Kuiken, L.A. Miller, R.D. Lipschutz, B.A. Lock, K. Stubblefield, P.D. Marasco, et al., Targeted reinnervation for enhanced prosthetic arm function in a woman with a proximal amputation: a case study, Lancet 369 (9559) (2007) 371–380. [25] R. Baron, Mechanisms of disease: neuropathic pain—a clinical perspective, Nature Clin. Practice Neurol. 2 (2006) 95. [26] J.N. Campbell, R.A. Meyer, Mechanisms of neuropathic pain, Neuron 52 (1) (2006) 77–92. [27] J.M. Souza, C.A. Purnell, J.E. Cheesborough, A.S. Kelikian, G.A. Dumanian, Treatment of foot and ankle neuroma pain with processed nerve allografts, Foot Ankle Int. 37 (10) (2016) 1098–1105 PubMed PMID: 27340257. PMCID: PMC5363503. Epub 2016/06/25. eng. [28] B. Schlosshauer, L. Dreesmann, H.-E. Schaller, N. Sinis, Synthetic nerve guide implants in humans: a comprehensive survey, Neurosurgery 59 (4) (2006) 740–748. [29] Y. Inada, S. Morimoto, Y. Takakura, T. Nakamura, Regeneration of peripheral nerve gaps with a polyglycolic acid-collagen tube, Neurosurgery 55 (3) (2004) 640–648. [30] F.F. IJpma, J.-P.A. Nicolai, M.F. Meek, Sural nerve donor-site morbidity: thirty-four years of follow-up, Ann. Plastic Surg. 57 (4) (2006) 391–395.
peripheral neurectomy for occipital neuralgia, Neurosurg. Q. 15 (4) (2005) 232–238 PubMed PMID: 00013414-200512000-00005. M.S. Cho, B.D. Rinker, R.V. Weber, J.D. Chao, J.V. Ingari, D. Brooks, et al., Functional outcome following nerve repair in the upper extremity using processed nerve allograft, J. Hand Surg. 37 (11) (2012) 2340–2349. D.N. Brooks, R.V. Weber, J.D. Chao, B.D. Rinker, J. Zoldos, M.R. Robichaux, et al., Processed nerve allografts for peripheral nerve reconstruction: a multicenter study of utilization and outcomes in sensory, mixed, and motor nerve reconstructions, Microsurgery 32 (1) (2012) 1–14. E. Rawner, D.M. Irwin, A.M. Trescot, Lesser occipital nerve entrapment, in: A.M. Trescot (Ed.), Peripheral Nerve Entrapments: Clinical Diagnosis and Management, Springer International Publishing, Cham, 2016, pp. 149–158. K.S. Dash, J.E. Janis, B. Guyuron, The lesser and third occipital nerves and migraine headaches, Plastic Reconstructive Surg. 115 (6) (2005) 1752–1758. N. Becser, G. Bovim, O. Sjaastad, Extracranial nerves in the posterior part of the head: anatomic variations and their possible clinical significance, Spine 23 (13) (1998) 1435–1441. D.L. Brown, G.Y. Wong, Greater and lesser occipital nerve block, Pain Management, Elsevier, 2007, pp. 1140–1144. G.A. Dumanian, B.K. Potter, L.M. Mioton, J.H. Ko, J.E. Cheesborough, J.M. Souza, et al., Targeted muscle reinnervation treats neuroma and phantom pain in major limb amputees: a randomized clinical trial, Ann. Surg. (2018) PubMed PMID: 30371518. Epub 2018/10/30. eng. S.D. Silberstein, D.W. Dodick, J. Saper, B. Huh, K.V. Slavin, A. Sharan, et al., Safety and efficacy of peripheral nerve stimulation of the occipital nerves for the management of chronic migraine: results from a randomized, multicenter, doubleblinded, controlled study, Cephalalgia 32 (16) (2012) 1165–1179.
4
Contents lists available at ScienceDirect
Interdisciplinary Neurosurgery journal homepage: www.elsevier.com/locate/inat
Case Reports & Case Series
Lesser occipital nerve damage after retrosigmoid craniotomy repaired with processed nerve allograft
T
⁎
John P. Andrews , Michael McDermott, Line Jacques University of California-San Francisco, Department of Neurological Surgery, USA
A R T I C LE I N FO
A B S T R A C T
Keywords: Retrosigmoid craniotomy Retrosigmoid incision Lesser occipital nerve Nerve graft, Occipital neuralgia
Background and importance: The retrosigmoid approach provides a robust corridor to cerebellopontine angle (CPA) pathology, but postoperative headache syndromes can cause significant patient distress. The lesser occipital nerve (LON) is in danger of injury during a retrosigmoid approach, and LON injury may present as occipital neuralgia with hypesthesia, dysesthesia and/or allodynia in the distribution of the LON. There are a number of treatment alternatives for refractory occipital neuralgia, but LON repair with processed nerve allograft has not previously been reported. Clinical presentation: A 42-year-old female was referred to peripheral nerve clinic for neuropathic pain, numbness and discomfort in a right LON distribution. Her history was significant for right retrosigmoid craniotomy for fenestration of a symptomatic CPA arachnoid cyst 2.5 years prior. Exam was significant for allodynia and reduced sensation. Exploration of the retrosigmoid incision revealed a damaged, scarred down LON. The nerve was trimmed and a 3 cm cadaveric, processed nerve allograft was interposed between the proximal and distal segments, secured without tension. The patient exhibited improvement in her neuropathic pain at follow-up. Conclusion: LON injury during retrosigmoid craniotomy can lead to occipital neuralgia and significant patient distress. Surgeons should be aware of the LON’s course relative to retrosigmoid incisions. Repair of the injured nerve with processed cadaveric nerve allograft deserves continued investigation for treating LON damage.
1. Background and importance The retrosigmoid approach provides a robust corridor to cerebellopontine angle (CPA) pathology, but carries high rates of postoperative headache syndromes [1–7]. There are multiple possible etiologies of the postoperative headache, including scalp adhesions to dura, cerebrospinal fluid leak, aseptic meningitis, and occipital nerve damage [4,7,8]. Occipital neuralgia involves pain in the distribution of the greater or lesser occipital nerves, characterized by lancinating or paroxysmal pain over the affected nerve, and may also feature Tinel’s sign and sensory changes [9,10]. During a retrosigmoid approach, the greater or lesser occipital nerves may be damaged either during incision, or secondarily from retraction of the tissue [2,7]. The lesser occipital nerve (LON) may lie in the path of the retrosigmoid incision, putting it in danger of incisional damage [11]. The incidence of occipital neuralgia from retrosigmoid craniotomy is unclear, but in one study of 113 patients who underwent acoustic neuroma surgery, 30 reported postoperative headache, of whom 5 had a pain syndrome fitting with occipital neuralgia [2]. One report of a
technique to preserve the LON during a suboccipital approach showed results suggesting that that preservation of the LON might significantly reduce postoperative occipital pain and sensory changes [11]. While prevention of nerve damage is optimal, a number of possible treatments for occipital neuralgia are in practice. Injection of local anesthetic can be both diagnostic and therapeutic, although the benefit is temporary [6]. Surgical interventions for refractory occipital neuralgia include neurectomy, neurolysis, radiofrequency ablation, posterior rhizotomy, peripheral nerve stimulation and C2-3 root decompression [12]. Nerve allograft interposition has been used with success for repair of injury to sensory, motor and mixed peripheral nerves [13,14]. To our knowledge, there have been no reports of cadaveric processed nerve allograft interposition being used for repair of the LON. 2. Clinical presentation 2.1. Patient information and clinical findings A 42-year-old female was referred to peripheral nerve clinic for
⁎ Corresponding author at: University of California, San Francisco, Department of Neurological Surgery, 505 Parnassus Ave Suite M779, San Francisco, CA 94143, USA. E-mail address: [email protected] (J.P. Andrews).
https://doi.org/10.1016/j.inat.2019.100592 Received 8 October 2019; Accepted 12 October 2019 2214-7519/ © 2019 Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/BY-NC-ND/4.0/).
Interdisciplinary Neurosurgery 19 (2020) 100592
J.P. Andrews, et al.
Fig. 1. Timeline. The patient originally presented with persistent nausea, vomiting and headaches in 2016. MRI showed right cerebellopontine angle arachnoid cyst causing brainstem compression. The patient underwent right retrosigmoid craniotomy for cyst fenestration, which relieved the presenting symptoms. Subsequently, the patient reported persistent numbness and dysesthesia in a lesser occipital nerve distribution, which was refractory to medical management. In 2019, she was taken to the operating room for exploration of her retrosigmoid incision and nerve repair.
Fig. 2. Surgical view of the left-sided C-shaped craniotomy incision re-opened for exploration and repair. The top of the pane is superior and the bottom is inferior. A) The damaged lesser occipital nerve (LON) is depicted, with distal (top) and proximal (bottom) aspects of the nerve isolated with vessel loops. The nerve clearly shows disruption and scarring down to the underlying titanium mesh. B) Post-repair, the graft is seen connecting the formerly discontinuous segments of the LON, secured without tension using 8-0 polypropylene sutures.
neuropathic pain in a right lesser occipital nerve distribution, which the patient reported causing significant distress. Her history was significant for right retrosigmoid craniotomy for fenestration of a symptomatic CPA arachnoid cyst 2.5 years prior (Fig. 1). The bone flap was replaced and secured using titanium plating during that surgery. Medical history was otherwise unremarkable. The patient reported persistent numbness and dysesthesia in right occipital distribution, including her incision site. These symptoms were refractory to pharmacologic management with common analgesics. On exam, she had allodynia over the midline of the retrosigmoid incision, a positive Tinel’s sign and dysesthesia over the sensory distribution of the right LON.
explored surgically and repaired using a processed cadaveric nerve allograft. Persistent headache syndromes following a retrosigmoid approach are well-documented phenomena. A number of procedural-based explanations have been proposed to underlie postoperative headache following such an approach [3,4]. Some of these include dural adhesions to scalp when bone flap is not replaced, drilling of the auditory meatis, and aseptic meningitis. For the patient discussed here, the bone flap was replaced during the first surgery, the internal auditory meatus was not drilled, and the postoperative pain syndrome was not consistent with aseptic meningitis. The observation of clearly damaged, scarred and thinned LON during surgical exploration of the wound, combined with the ipsilateral (unilateral) posterior sensory changes and pain in the distribution of the LON is highly suggestive of LON injury as the causal etiology. The LON originates primarily from the posterior rami of C2 (sometimes of C3) and pierces the superficial cervical plexus at the posterior border of the sternocleidomastoid (Fig. 3) [15]. A cadaveric study of 30 LON’s found that it emerges from behind the sternocleidomastoid roughly 5 ( ± 1.5) cm inferior to a line connecting bilateral external acoustic canals, and on average 6.5 ( ± 1.1) cm lateral to midline [15,16]. Cadaver studies suggest the LON ascends to the calvarium between 3 and 9 cm from midline [15,17], in a groove that may be palpated approximately two-thirds of the distance from the external occipital protuberance to the mastoid on the superior nuchal line [15,18]. Various incisions are used for retrosigmoid craniotomy, but no incision technique is certain to spare the LON (Fig. 3). The best way to avoid nerve damage may be careful dissection, identification and sparing of the LON during incision. In the treatment of painful neuroma, there is currently no unambiguous superior surgical treatment for neuroma pain [19]. When symptoms of occipital neuralgia are refractory to pharmacologic or non-invasive procedures, surgical treatment may be considered. Two examples of such treatments are peripheral nerve stimulation or neurectomy. Peripheral nerve stimulation for occipital neuralgia has been shown to be safe and effective [20,21]. A two-stage procedure can be employed, where electrodes are initially placed percutaneously through a guide-needle to attain a position over the greater or lesser occipital nerve targets. Stimulation can then be optimized prior to final surgical implantation. An inherent disadvantage of peripheral nerve stimulation
2.2. Therapeutic intervention Given the nature and location of the pain, as well of the history of retrosigmoid craniotomy, laceration of the LON during retrosigmoid incision with neuroma formation was suspected. Nerve laceration weighed against the use of peripheral nerve neurostimulation, so neuroma excision with possible nerve repair was considered. After discussing options, risks and benefits with the patient, she opted for neuroma excision with possible nerve repair. On the day of surgery, the patient was positioned supine, with her right shoulder elevated by a cushion and her head turned to the left. The prior C-shaped retrosigmoid incision was opened sharply and blunt dissection was used to identify the right proximal and distal aspects of the LON, which were isolated using vessel loops (Fig. 2A). At the level of the mesh plate—co-incident with the site of the patient’s Tinel sign—the nerve appeared to have been cut, and was scarred down. The LON was trimmed sharply at proximal and distal ends of the frayed portion, and these specimens were sent to pathology. Subsequently, a 3 cm processed cadaveric nerve allograft was interposed between the previously identified LON segments. The graft was secured without tension using two 8-0 polypropylene sutures at each site of anastomosis (Fig. 2B). The wound was then irrigated with bacitracin and hemostasis was achieved before closure. Pathology confirmed the diagnosis of neuroma. 2.3. Follow-up and outcomes At 2 months follow-up, dysesthesia was no longer present on physical exam, nor was there tenderness to palpation over the incision. 3. Discussion We report a case of occipital neuralgia following a retrosigmoid craniotomy, due to damage to the lesser occipital nerve, which was 2
Interdisciplinary Neurosurgery 19 (2020) 100592
J.P. Andrews, et al.
Fig. 3. Diagrams of 4 common incisions for a retrosigmoid approach, overlaid on relevant boney and neurovascular anatomy. As can be seen, all incisions put the LON at risk at some point in the course of the nerve. GON = Greater occipital nerve; TvS = Transverse Sinus; LON = Lesser occipital nerve; GAS = Great auricular nerve.
Acknowledgements
includes the presence of an implanted device, which may serve as a nidus for infection. The device will also eventually necessitate additional procedures for battery change. Moreover, rates of revision or electrode migration have been reported as over 30% [22]. Neurectomy and burying of the distal end of the damaged nerve into muscle is another treatment with therapeutic benefit. This tactic does not prevent neuroma formation, but rather the muscle supplies padding to the distal end of the damaged nerve [19,23]. Nerve function is neither rescued nor reassigned, but simply insulated. This is in contrast to a technique like targeted muscle reinnervation (TMR), in which a muscle is denervated before implantation of a rarified nerve tip [19,24]. TMR has also showed promise for reducing neuropathic pain of traumatic etiology, and in the future may be a good option for treatment of cases similar to the one discussed here [19]. The mechanisms of neuropathic pain following nerve injury are an area of ongoing investigation [25]. There is evidence to support spontaneous activity of these injured nerve fibers contributes to the neuropathic pain phenotype, and that allowing the nerve to re-form native (or native-like) connections might allay some pain symptoms [19,26,27]. Advances in repair of peripheral nerves have sought to use synthetic or processed alternatives to autografting [28,29]. Allograft, as opposed to autograft, avoids donor-site morbidity, such as new areas of sensory loss and donor-site pain [30]. Processed nerve allografts are a viable option for peripheral nerve repair, which avoid a donor site, while also not requiring immunosuppression that would be required for classic allografting with cellular elements intact [14]. Nerve allograft interposition has been used with some success in lower limb neuroma treatment and are a promising technique aimed at allowing a damaged peripheral nerve to reform native connections [27]. We report here a case of LON injury due to retrosigmoid craniotomy, repaired using a processed cadaveric nerve allograft. Followup is yet too preliminary to make strong recommendations based on this single case, but the intervention fits with a framework of treating neuroma restoring the injured nerve to as close a semblance of native connectivity as possible.
The authors would like to thank Kenneth X. Probst, Department of Neurological Surgery illustrator, for the manuscript artwork of Fig. 3. Conflict of interest None. Disclosure of funding None. Consent Patient consent was obtained prior to the submission of this manuscript. No IRB/ethics committee approval was required for this report. References [1] D.A. Schessel, J.M. Nedzelski, D. Rowed, J.G. Feghali, Pain after surgery for acoustic neuroma, Otolaryngol.—Head Neck Surg. 107 (3) (1992) 424–429. [2] C. Schankin, C. Gall, A. Straube, Headache syndromes after acoustic neuroma surgery and their implications for quality of life, Cephalalgia 29 (7) (2009) 760–771. [3] A. Sabab, J. Sandhu, S. Bacchi, A. Jukes, A. Zacest, Postoperative headache following treatment of vestibular schwannoma: a literature review, J. Clin. Neurosci. 52 (2018) 26–31. [4] B. Schaller, A. Baumann, Headache after removal of vestibular schwannoma via the retrosigmoid approach: a long-term follow-up-study, Otolaryngol.-Head Neck Surg. 128 (3) (2003) 387–395. [5] S.F. Ansari, C. Terry, A.A. Cohen-Gadol, Surgery for vestibular schwannomas: a systematic review of complications by approach, Neurosurg. Focus 33 (3) (2012) E14. [6] I. Ducic, J.M. Felder III, M. Endara, Postoperative headache following acoustic neuroma resection: occipital nerve injuries are associated with a treatable occipital neuralgia, Headache 52 (7) (2012) 1136–1145. [7] M.K. Teo, M.S. Eljamel, Role of craniotomy repair in reducing postoperative headaches after a retrosigmoid approach, Neurosurgery 67 (5) (2010) 1286–1292. [8] T.J. Lovely, The treatment of chronic incisional pain and headache after retromastoid craniectomy, Surg. Neurol. Int. 3 (2012). [9] W.F. Kuhn, S.C. Kuhn, H. Gilberstadt, Occipital neuralgias: clinical recognition of a complicated headache. A case series and literature review, J. Orofacial Pain 11 (2) (1997). [10] P. Vanelderen, A. Lataster, R. Levy, N. Mekhail, M. Van Kleef, J. Van Zundert, 8. Occipital neuralgia, Pain Practice 10 (2) (2010) 137–144. [11] F. Takamitsu, S. Jae-Hyun, T. Shigehiko, I. Teruyuki, F. Kazuhide, M. Toshihiro, et al., Preservation of the lesser occipital nerve during microvascular decompression for hemifacial spasm, J. Neurosurg. JNS 107 (6) (2007) 1235–1237 English. [12] R.R. Sharma, R.V. Devadas, S.J. Pawar, S.D. Lad, A.K. Mahapatra, Current status of
4. Conclusion Retrosigmoid craniotomy can lead to LON injury causing significant patient distress. To avoid the morbidity of nerve injury, surgeons should be aware of the course of the LON and spare it if possible during retrosigmoid incision. Repair of the traumatized nerve with processed cadaveric nerve allograft is a technique for treating LON neuroma that deserves continued investigation. 3
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