ORL 2014;76:44–49 DOI: 10.1159/000358305 Received: July 29, 2013 Accepted after revision: December 27, 2013 Published online: April 3, 2014
© 2014 S. Karger AG, Basel 0301–1569/14/0761–0044$39.50/0 www.karger.com/orl
Original Paper
Endoscopic Optic Nerve Decompression for Patients with Traumatic Optic Neuropathy: Is Nerve Sheath Incision Necessary? Rui Xu a Fenghong Chen a Kejun Zuo a Jianbo Shi a Hexin Chen a Huabin Li a
Xingling Ye a
Qintai Yang b
Departments of Otolaryngology at a The First Affiliated Hospital of Sun Yat-sen University and b The Third Affiliated Hospital of Sun Yat-sen University, Guangzhou, China
Key Words Endoscopic optic nerve decompression · Traumatic optic neuropathy · Nerve sheath · Steroid · Efficacy · Complication Abstract Objective: To evaluate the necessity of nerve sheath incision for the treatment of patients with traumatic optic neuropathy (TON) during endoscopic optic nerve decompression. Methods: Seventy-four TON patients were enrolled and subjected to endoscopic optic nerve decompression. In 31 TON patients (group A), osseous decompression and nerve sheath incision were performed, and in 43 TON patients (group B), osseous decompression alone was carried out. Visual acuity was evaluated postoperatively. Results: After surgery, visual acuity was improved in 47 of 74 patients, with a total effectiveness ratio of 63.5%. The total ratio of improvement in groups A and B was 61.2 and 65.1%, respectively, and no significant difference was observed (p > 0.05). As to the patients with residual vision preoperatively, the ratio of improvement in groups A and B was 64.2 and 71.4%, respectively (p > 0.05), not favoring nerve sheath incision during endoscopic optic nerve decompression. Conclusion: Our preliminary results suggest that during endoscopic optic nerve decompression for the treatment of TON patients, nerve sheath incision is not obligatory for the improvement of visual acuity. © 2014 S. Karger AG, Basel
R.X. and F.C. contributed equally to the study. Huabin Li, MD, PhD Department of Otolaryngology The First Affiliated Hospital of Sun Yat-sen University No. 58, Zhongshan 2nd Road, Guangzhou 510080 (China) E-Mail allergyli @ 163.com
45
ORL 2014;76:44–49 DOI: 10.1159/000358305
© 2014 S. Karger AG, Basel www.karger.com/orl
Xu et al.: Endoscopic Optic Nerve Decompression for Patients with Traumatic Optic Neuropathy: Is Nerve Sheath Incision Necessary?
Introduction
Traumatic optic neuropathy (TON) is very common in young patients with closed head injuries. The most common causes of TON in adults are motor vehicle and bicycle accidents, falls and assaults [1]. It has been suggested that both direct and indirect mechanisms account for such optic nerve pathology. Direct optic injury usually results from optic nerve avulsion or laceration, or from direct fracture of the optic canal. Indirect optic injury is caused by increased intracanalicular pressure after an injury, which usually initiates a cascade of molecular and chemical mediators leading to secondary disorders such as intraneural oedema, haematoma, altered microvasculature or cerebrospinal fluid circulation, and interruption of direct axoplasmic transport [2]. Although the best treatment for TON remained elusive, it has been demonstrated by numerous published literatures that endoscopic optic nerve decompression is effective to a large proportion of TON patients by releasing intracanalicular tension on the optic nerve. In contrast to the intracranial optic nerve decompression, endoscopic optic nerve decompression is regarded as a safe, effective and minimally invasive procedure and is widely applied in the treatment of TON patients [3–7]. During optic nerve decompression, the bony optic canal is partially removed to decompress the nerve within the canal to limit the damaging effect of compression and to reestablish nerve function, namely osseous decompression. Subsequently, the optic nerve sheath and the annulus of Zinn have been traditionally suggested to be slit to reduce the pressure on the optic nerve [2]. Whereas osseous decompression has been widely adopted for the treatment of TON patients, nerve sheath incision during optic nerve decompression is controversial to some extent [6, 7]. To address this issue, we herein compare the effect of optic nerve decompression on visual acuity in two groups of TON patients. Group A comprised 25 TON patients who underwent osseous decompression and nerve sheath incision, and group B included 43 TON patients who underwent osseous decompression alone. The aim of the present study was to evaluate whether nerve sheath incision offered additional benefit for the improvement of visual acuity in TON patients in whom endoscopic optic nerve decompression was performed. Subjects and Methods Subjects Seventy-four TON patients were enrolled in this study during the past 2 years. Of these, 68 were male and 6 were female. The average age was 30.7 years (range 14–58). All patients were treated by an ophthalmologist and underwent a complete examination to evaluate visual impairment. A fine-cut CT scan was then performed to evaluate the orbit and optic canal. Once the diagnosis of TON had been established by the ophthalmologist, all 74 TON patients were treated with high-dose methylprednisolone (10 mg/day/kg) for more than 7 days and obtained poor response. They were thus transferred to the otolaryngologic unit for surgical intervention. After written consent was signed, these patients were submitted to endoscopic optic nerve decompression. In order to assess the effect of nerve sheath incision on the efficacy of surgical decompression, 74 TON patients were unselectively categorized into two groups. Group A comprised 31 TON patients with osseous decompression and nerve sheath incision performed by senior rhinologists (R.X., F.C., J.S., H.C.). Group B comprised 43 TON patients with osseous decompression alone, which was specifically performed by one senior rhinologist (H.L.) to assess the necessity of nerve sheath incision. After surgery, methylprednisolone continued to be used with a step-down procedure. The patient demographics are listed in table 1. The study was approved by the Ethical Committee of the First Affiliated Hospital of Sun Yat-sen University. Surgical Procedure TON patients were prepared in the routine manner for endoscopic sinus surgery under general anaesthesia. Cotton pledgets soaked in adrenaline solution were placed in the nasal cavity to ensure vasocon-
46
ORL 2014;76:44–49 © 2014 S. Karger AG, Basel www.karger.com/orl
DOI: 10.1159/000358305
Xu et al.: Endoscopic Optic Nerve Decompression for Patients with Traumatic Optic Neuropathy: Is Nerve Sheath Incision Necessary?
Table 1. Clinical characteristics
of TON patients
p
Group A
Group B
(with nerve
(without nerve value
sheath incision) sheath incision)
Subjects Males Mean age, years Mean days of lapse before surgery Optic canal fracture No light perception Light perception or better
31 29 29.4 9.6 5 17 14
43 39 31.8 10.9 7 22 21
n.s. n.s. n.s. n.s. n.s. n.s. n.s.
Values represent n, unless otherwise specified.
striction. In case of nasal septal deviation, submucosal septoplasty was firstly performed to gain wide access to the optic apex and canal. The surgical procedure was modified as we described elsewhere [4]. For patients in whom osseous decompression alone was performed, routine endoscopic ethmoidectomy and sphenoidotomy were first performed. When the sphenoid sinus was opened and the ostium was enlarged, the optic nerve canal and carotid artery canal were identified. The orbital apex and optic ring were then dissected. Under endoscopic observation, a long-hand microdrill with a diamond burr was used to remove the medial wall of the bony optic canal. With this technique, the optical canal was drilled 180o medially from the optic tubercle to near the optic chiasm until the bony canal became very thin. A special elevator was then used to elevate the thin bony canal from over the optic nerve. Extreme care was taken not to exert pressure on the optic nerve with the elevator. For patients in whom osseous decompression and nerve sheath incision was performed, the optic nerve sheath and the annulus of Zinn were incised with a delicate sickle knife, exposing the fasciculus opticus proper, as the optic nerve sheath and the annulus of Zinn may potentially contribute to the pressure on the optic nerve. Finally, an absorbable gelatin sponge was placed in the cavity. Evaluation and Statistics All patients received regular inspection including visual acuity and field chart testing 10 days after surgery. A patient’s vision was considered to have improved if (a) there was an increase of two lines or more on the Snellen visual chart, (b) a 10% improvement in his/her visual field occurred, (c) an improvement from no light perception to light perception or better, (d) an improvement from light perception to hand motion or better, or (e) an improvement from hand motion to finger counting or better occurred. Student’s t test was used to analyze the differences between the continuous variables, and the χ2 test was used to evaluate differences between group A and group B. A p value 0.05). Moreover, based on whether residual vision existed preoperatively, the patients were again divided into subgroup 1 (without residual vision preoperatively, 17 cases in group A and 22 cases in group B) and 2 (with residual vision preoperatively, 14 cases in group A and 21 cases in group B). Consequently, the ratio of improvement in groups A1 and B1 was 58.8% (10/17) and 59.0% (13/22), respectively, and there was no significant difference (p > 0.05). Similarly, the ratio of improvement in groups A2 and B2 was 64.2% (9/14) and 71.4% (15/21), respectively, and there was a significant difference (p > 0.05). Discussion
In this retrospective, nonrandomized, interventional study, we demonstrated that endoscopic optic nerve decompression is a safe, effective and minimally invasive strategy for the treatment of TON. By comparing the clinical outcome of patients with or without nerve sheath incision (groups A and B), our results provided evidence that there was no significant difference in the ratio of improvement in groups A and B in which different surgical procedures were performed, suggesting that nerve sheath incision is not obligatory during endoscopic optic nerve decompression. TON is very common in patients with blunt or penetrating head trauma with a reported incidence of 0.7–2.5%, but its pathophysiology remains unclear [1]. It has been suggested that both direct and indirect mechanisms can contribute to optic nerve damage in spite of a clear distinction that is not usually possible in TON patients. Theoretically, direct optic injury usually results from optic nerve avulsion or laceration or from direct fracture of the optic canal (with bony fragments injuring or transecting the optic nerve) [2]. The prognosis of direct optic injury is usually poor. Patients with a complete disruption of the optic nerve will not recover, regardless of the medical or surgical treatment. Indirect optic injury is caused by increased intracanalicular pressure after an injury, which usually initiates a cascade of molecular and chemical mediators leading to secondary disorders such as intraneural oedema, haematoma, altered microvasculature or cerebrospinal fluid circulation, and interruption of direct axoplasmic transport. Conversely, these secondary injuries such as oedema, haematoma or moderate bony optic nerve compression may benefit from treatment. For this reason, surgical decompression has been postulated to be effective in TON patients by releasing the compartmental syndrome [3]. In the present study, we enrolled 74 patients with TON to evaluate the efficacy of endoscopic optic nerve decompression by successful surgical decompression. In response to surgical decompression followed by intravenous high-dose steroid treatment, visual acuity was improved in 47 of 74 patients, with a total effectiveness ratio of 63.5%. Except for 1 male patient in group A who died of a severe cranial infection 4 days after surgery, no other severe complication (cranial infection, cerebrospinal fluid leakage, severe epistaxis, etc.) occurred.
48
ORL 2014;76:44–49 DOI: 10.1159/000358305
© 2014 S. Karger AG, Basel www.karger.com/orl
Xu et al.: Endoscopic Optic Nerve Decompression for Patients with Traumatic Optic Neuropathy: Is Nerve Sheath Incision Necessary?
These findings suggest that endoscopic optic nerve decompression is safe and effective in the treatment of TON. Currently, the best treatment for TON patients remains controversial [8–13]. Although meta-analysis has shown that both administrations of high-dose steroid and/or surgical decompression contributed to the prognosis of TON, a spontaneous visual recovery rate of 20–38% has also been reported for indirect TON cases [8–10]. Moreover, whether nerve sheath incision should be performed during endoscopic optic nerve decompression is still under debate [6, 13]. It is known that the optic nerve sheath is an anterior extension of the middle cranial fossa dura, which envelopes the canalicular optic nerve and condenses at its anterior end to a concentric fibrous ring known as the annulus of Zinn. Proponents of decompression of the nerve sheath note that the post-traumatic compartmental syndrome is best relieved by releasing the constricting sheath enveloping the nerve [3]. Thaker et al. [6] previously reported that the quantum of recovery was greater in patients with residual vision before surgery who underwent combined osseous decompression and optic nerve sheath incision than in patients of osseous decompression alone (46 and 33%, respectively). This suggests that the addition of optic nerve sheath incision to osseous decompression may improve the recovery in optic nerve injury, especially in subjects without optic canal fracture. In our previous studies, we routinely performed nerve sheath slitting during endoscopic optic nerve decompression without severe complication such as cerebrospinal fluid leakage and ophthalmic artery injury [4]. However, considering nerve sheath slitting may cause an increase in the risk of an occasional cerebrospinal fluid leakage and ophthalmic artery injury or a decrease in the efficacy by potentially disrupting the pial vessels contributing to nerve vascularity or disrupting the nerve fascicles, the efficacy of nerve sheath slitting has also been doubted by some authors. In this study, we sought to evaluate the efficacy and safety of osseous decompression alone. In contrast, we found that the ratio of improvement in subjects with osseous decompression and nerve sheath incision and subjects without nerve sheath incision was 61.2 and 65.1%, respectively, and there was no significant difference. These findings indicated that nerve sheath incision is not superior to osseous decompression alone in the efficacy of endoscopic optic nerve decompression in TON patients. Moreover, when we specifically compared the efficacy of endoscopic optic nerve decompression with and without nerve sheath incision in TON patients with residual vision preoperatively, we found that the ratio of improvement in the former group was slightly lower than in the latter group (64.2 and 71.4%, respectively), not favoring nerve sheath incision during endoscopic optic nerve decompression. Additionally, it is important to note the death of 1 TON patient after surgical decompression. In this young man with traumatic blindness, no cerebrospinal fluid leakage occurred in spite of nerve sheath incision during surgery. There was no evidence showing that the death-related cranial infection was caused by surgical decompression. After careful cadaver inspection and comprehensive consult, we postulate that the death of the TON patient who was just recovered from severe head injury and skull base fracture may have been hit by the cranial pathogens after administration of intravenous high-dose steroid. This complication reminded us of the fact that balancing the risk and benefit of surgical and medical treatment is important for TON patients with severe head injury and skull base fracture. We acknowledge that this study also contains some flaws. First, it was not a randomized, placebo-controlled clinical trial, so the effect of steroid cannot be completely excluded. Second, we failed to obtain a long-term outcome of this cohort on the prognosis of TON. This may weaken the power of our conclusion. However, since surgical decompression with nerve sheath incision did not show any additional advantage in this study, our findings may be beneficial to the establishment of a less invasive surgical decompression without nerve sheath incision. Further study is still required to validate our conclusion in this study.
49
ORL 2014;76:44–49 DOI: 10.1159/000358305
© 2014 S. Karger AG, Basel www.karger.com/orl
Xu et al.: Endoscopic Optic Nerve Decompression for Patients with Traumatic Optic Neuropathy: Is Nerve Sheath Incision Necessary?
In summary, our preliminary results suggest that nerve sheath incision is not obligatory for the improvement of visual acuity during endoscopic optic nerve decompression for the treatment of TON patients. Specifically, when compared with the efficacy of endoscopic optic nerve decompression with and without nerve sheath incision in TON patients with residual vision preoperatively, we found that the ratio of improvement favored no nerve sheath incision during surgery. Acknowledgements This study was supported by grants from the National Natural Science Fund of China (No. 81070771, 81070772) and a grant from the Ministry of Hygiene (No. 201202005) and Program for New Century Excellent Talents in University (No. NCET-10-0851).
Disclosure Statement The authors have no conflicts of interest to declare pertaining to this article.
References 1 2 3 4 5 6 7 8 9 10 11 12 13
Warner N, Eggenberger E: Traumatic optic neuropathy: a review of the current literature. Curr Opin Ophthalmol 2010;21:459–462. Steinsapir KD, Goldberg RA: Traumatic optic neuropathy: an evolving understanding. Am J Ophthalmol 2011; 151:928–933. Pletcher SD, Sindwani R, Metson R: Endoscopic orbital and optic nerve decompression. Otolaryngol Clin North Am 2006;39:943–958. Li H, Zhou B, Shi J, et al: Treatment of traumatic optic neuropathy: our experience of endoscopic optic nerve decompression. J Laryngol Otol 2008;122:1325–1329. Wang DH, Zheng CQ, Qian J, et al: Endoscopic optic nerve decompression for the treatment of traumatic optic nerve neuropathy. ORL J Otorhinolaryngol Relat Spec 2008;70:130–133. Thaker A, Tandon DA, Mahapatra AK: Surgery for optic nerve injury: should nerve sheath incision supplement osseous decompression? Skull Base 2009;19:263–271. Chen C, Selva D, Floreani S, et al: Endoscopic optic nerve decompression for traumatic optic neuropathy: an alternative. Otolaryngol Head Neck Surg 2006;135:155–157. Volpe NJ, Levin LA: How should patients with indirect traumatic optic neuropathy be treated? J Neuroophthalmol 2011;31:169–174. Samardzic K, Samardzic J, Janjetovic Z, et al: Traumatic optic neuropathy – to treat or to observe? Acta Inform Med 2012;20:131–132. Levin LA, Beck RW, Joseph MP, et al: The treatment of traumatic optic neuropathy: the International Optic Nerve Trauma Study. Ophthalmology 1999;106:1268–1277. Perry JD: Treatment of traumatic optic neuropathy remains controversial. Arch Otolaryngol Head Neck Surg 2004;130:1000. Yang WG, Chen CT, Tsay PK, et al: Outcome for traumatic optic neuropathy–surgical versus nonsurgical treatment. Ann Plast Surg 2004;52:36–42. Ropposch T, Steger B, Meço C, et al: The effect of steroids in combination with optic nerve decompression surgery in traumatic optic neuropathy. Laryngoscope 2013;123:1082–1086.
Copyright: S. Karger AG, Basel 2014. Reproduced with the permission of S. Karger AG, Basel. Further reproduction or distribution (electronic or otherwise) is prohibited without permission from the copyright holder.
© 2014 S. Karger AG, Basel 0301–1569/14/0761–0044$39.50/0 www.karger.com/orl
Original Paper
Endoscopic Optic Nerve Decompression for Patients with Traumatic Optic Neuropathy: Is Nerve Sheath Incision Necessary? Rui Xu a Fenghong Chen a Kejun Zuo a Jianbo Shi a Hexin Chen a Huabin Li a
Xingling Ye a
Qintai Yang b
Departments of Otolaryngology at a The First Affiliated Hospital of Sun Yat-sen University and b The Third Affiliated Hospital of Sun Yat-sen University, Guangzhou, China
Key Words Endoscopic optic nerve decompression · Traumatic optic neuropathy · Nerve sheath · Steroid · Efficacy · Complication Abstract Objective: To evaluate the necessity of nerve sheath incision for the treatment of patients with traumatic optic neuropathy (TON) during endoscopic optic nerve decompression. Methods: Seventy-four TON patients were enrolled and subjected to endoscopic optic nerve decompression. In 31 TON patients (group A), osseous decompression and nerve sheath incision were performed, and in 43 TON patients (group B), osseous decompression alone was carried out. Visual acuity was evaluated postoperatively. Results: After surgery, visual acuity was improved in 47 of 74 patients, with a total effectiveness ratio of 63.5%. The total ratio of improvement in groups A and B was 61.2 and 65.1%, respectively, and no significant difference was observed (p > 0.05). As to the patients with residual vision preoperatively, the ratio of improvement in groups A and B was 64.2 and 71.4%, respectively (p > 0.05), not favoring nerve sheath incision during endoscopic optic nerve decompression. Conclusion: Our preliminary results suggest that during endoscopic optic nerve decompression for the treatment of TON patients, nerve sheath incision is not obligatory for the improvement of visual acuity. © 2014 S. Karger AG, Basel
R.X. and F.C. contributed equally to the study. Huabin Li, MD, PhD Department of Otolaryngology The First Affiliated Hospital of Sun Yat-sen University No. 58, Zhongshan 2nd Road, Guangzhou 510080 (China) E-Mail allergyli @ 163.com
45
ORL 2014;76:44–49 DOI: 10.1159/000358305
© 2014 S. Karger AG, Basel www.karger.com/orl
Xu et al.: Endoscopic Optic Nerve Decompression for Patients with Traumatic Optic Neuropathy: Is Nerve Sheath Incision Necessary?
Introduction
Traumatic optic neuropathy (TON) is very common in young patients with closed head injuries. The most common causes of TON in adults are motor vehicle and bicycle accidents, falls and assaults [1]. It has been suggested that both direct and indirect mechanisms account for such optic nerve pathology. Direct optic injury usually results from optic nerve avulsion or laceration, or from direct fracture of the optic canal. Indirect optic injury is caused by increased intracanalicular pressure after an injury, which usually initiates a cascade of molecular and chemical mediators leading to secondary disorders such as intraneural oedema, haematoma, altered microvasculature or cerebrospinal fluid circulation, and interruption of direct axoplasmic transport [2]. Although the best treatment for TON remained elusive, it has been demonstrated by numerous published literatures that endoscopic optic nerve decompression is effective to a large proportion of TON patients by releasing intracanalicular tension on the optic nerve. In contrast to the intracranial optic nerve decompression, endoscopic optic nerve decompression is regarded as a safe, effective and minimally invasive procedure and is widely applied in the treatment of TON patients [3–7]. During optic nerve decompression, the bony optic canal is partially removed to decompress the nerve within the canal to limit the damaging effect of compression and to reestablish nerve function, namely osseous decompression. Subsequently, the optic nerve sheath and the annulus of Zinn have been traditionally suggested to be slit to reduce the pressure on the optic nerve [2]. Whereas osseous decompression has been widely adopted for the treatment of TON patients, nerve sheath incision during optic nerve decompression is controversial to some extent [6, 7]. To address this issue, we herein compare the effect of optic nerve decompression on visual acuity in two groups of TON patients. Group A comprised 25 TON patients who underwent osseous decompression and nerve sheath incision, and group B included 43 TON patients who underwent osseous decompression alone. The aim of the present study was to evaluate whether nerve sheath incision offered additional benefit for the improvement of visual acuity in TON patients in whom endoscopic optic nerve decompression was performed. Subjects and Methods Subjects Seventy-four TON patients were enrolled in this study during the past 2 years. Of these, 68 were male and 6 were female. The average age was 30.7 years (range 14–58). All patients were treated by an ophthalmologist and underwent a complete examination to evaluate visual impairment. A fine-cut CT scan was then performed to evaluate the orbit and optic canal. Once the diagnosis of TON had been established by the ophthalmologist, all 74 TON patients were treated with high-dose methylprednisolone (10 mg/day/kg) for more than 7 days and obtained poor response. They were thus transferred to the otolaryngologic unit for surgical intervention. After written consent was signed, these patients were submitted to endoscopic optic nerve decompression. In order to assess the effect of nerve sheath incision on the efficacy of surgical decompression, 74 TON patients were unselectively categorized into two groups. Group A comprised 31 TON patients with osseous decompression and nerve sheath incision performed by senior rhinologists (R.X., F.C., J.S., H.C.). Group B comprised 43 TON patients with osseous decompression alone, which was specifically performed by one senior rhinologist (H.L.) to assess the necessity of nerve sheath incision. After surgery, methylprednisolone continued to be used with a step-down procedure. The patient demographics are listed in table 1. The study was approved by the Ethical Committee of the First Affiliated Hospital of Sun Yat-sen University. Surgical Procedure TON patients were prepared in the routine manner for endoscopic sinus surgery under general anaesthesia. Cotton pledgets soaked in adrenaline solution were placed in the nasal cavity to ensure vasocon-
46
ORL 2014;76:44–49 © 2014 S. Karger AG, Basel www.karger.com/orl
DOI: 10.1159/000358305
Xu et al.: Endoscopic Optic Nerve Decompression for Patients with Traumatic Optic Neuropathy: Is Nerve Sheath Incision Necessary?
Table 1. Clinical characteristics
of TON patients
p
Group A
Group B
(with nerve
(without nerve value
sheath incision) sheath incision)
Subjects Males Mean age, years Mean days of lapse before surgery Optic canal fracture No light perception Light perception or better
31 29 29.4 9.6 5 17 14
43 39 31.8 10.9 7 22 21
n.s. n.s. n.s. n.s. n.s. n.s. n.s.
Values represent n, unless otherwise specified.
striction. In case of nasal septal deviation, submucosal septoplasty was firstly performed to gain wide access to the optic apex and canal. The surgical procedure was modified as we described elsewhere [4]. For patients in whom osseous decompression alone was performed, routine endoscopic ethmoidectomy and sphenoidotomy were first performed. When the sphenoid sinus was opened and the ostium was enlarged, the optic nerve canal and carotid artery canal were identified. The orbital apex and optic ring were then dissected. Under endoscopic observation, a long-hand microdrill with a diamond burr was used to remove the medial wall of the bony optic canal. With this technique, the optical canal was drilled 180o medially from the optic tubercle to near the optic chiasm until the bony canal became very thin. A special elevator was then used to elevate the thin bony canal from over the optic nerve. Extreme care was taken not to exert pressure on the optic nerve with the elevator. For patients in whom osseous decompression and nerve sheath incision was performed, the optic nerve sheath and the annulus of Zinn were incised with a delicate sickle knife, exposing the fasciculus opticus proper, as the optic nerve sheath and the annulus of Zinn may potentially contribute to the pressure on the optic nerve. Finally, an absorbable gelatin sponge was placed in the cavity. Evaluation and Statistics All patients received regular inspection including visual acuity and field chart testing 10 days after surgery. A patient’s vision was considered to have improved if (a) there was an increase of two lines or more on the Snellen visual chart, (b) a 10% improvement in his/her visual field occurred, (c) an improvement from no light perception to light perception or better, (d) an improvement from light perception to hand motion or better, or (e) an improvement from hand motion to finger counting or better occurred. Student’s t test was used to analyze the differences between the continuous variables, and the χ2 test was used to evaluate differences between group A and group B. A p value 0.05). Moreover, based on whether residual vision existed preoperatively, the patients were again divided into subgroup 1 (without residual vision preoperatively, 17 cases in group A and 22 cases in group B) and 2 (with residual vision preoperatively, 14 cases in group A and 21 cases in group B). Consequently, the ratio of improvement in groups A1 and B1 was 58.8% (10/17) and 59.0% (13/22), respectively, and there was no significant difference (p > 0.05). Similarly, the ratio of improvement in groups A2 and B2 was 64.2% (9/14) and 71.4% (15/21), respectively, and there was a significant difference (p > 0.05). Discussion
In this retrospective, nonrandomized, interventional study, we demonstrated that endoscopic optic nerve decompression is a safe, effective and minimally invasive strategy for the treatment of TON. By comparing the clinical outcome of patients with or without nerve sheath incision (groups A and B), our results provided evidence that there was no significant difference in the ratio of improvement in groups A and B in which different surgical procedures were performed, suggesting that nerve sheath incision is not obligatory during endoscopic optic nerve decompression. TON is very common in patients with blunt or penetrating head trauma with a reported incidence of 0.7–2.5%, but its pathophysiology remains unclear [1]. It has been suggested that both direct and indirect mechanisms can contribute to optic nerve damage in spite of a clear distinction that is not usually possible in TON patients. Theoretically, direct optic injury usually results from optic nerve avulsion or laceration or from direct fracture of the optic canal (with bony fragments injuring or transecting the optic nerve) [2]. The prognosis of direct optic injury is usually poor. Patients with a complete disruption of the optic nerve will not recover, regardless of the medical or surgical treatment. Indirect optic injury is caused by increased intracanalicular pressure after an injury, which usually initiates a cascade of molecular and chemical mediators leading to secondary disorders such as intraneural oedema, haematoma, altered microvasculature or cerebrospinal fluid circulation, and interruption of direct axoplasmic transport. Conversely, these secondary injuries such as oedema, haematoma or moderate bony optic nerve compression may benefit from treatment. For this reason, surgical decompression has been postulated to be effective in TON patients by releasing the compartmental syndrome [3]. In the present study, we enrolled 74 patients with TON to evaluate the efficacy of endoscopic optic nerve decompression by successful surgical decompression. In response to surgical decompression followed by intravenous high-dose steroid treatment, visual acuity was improved in 47 of 74 patients, with a total effectiveness ratio of 63.5%. Except for 1 male patient in group A who died of a severe cranial infection 4 days after surgery, no other severe complication (cranial infection, cerebrospinal fluid leakage, severe epistaxis, etc.) occurred.
48
ORL 2014;76:44–49 DOI: 10.1159/000358305
© 2014 S. Karger AG, Basel www.karger.com/orl
Xu et al.: Endoscopic Optic Nerve Decompression for Patients with Traumatic Optic Neuropathy: Is Nerve Sheath Incision Necessary?
These findings suggest that endoscopic optic nerve decompression is safe and effective in the treatment of TON. Currently, the best treatment for TON patients remains controversial [8–13]. Although meta-analysis has shown that both administrations of high-dose steroid and/or surgical decompression contributed to the prognosis of TON, a spontaneous visual recovery rate of 20–38% has also been reported for indirect TON cases [8–10]. Moreover, whether nerve sheath incision should be performed during endoscopic optic nerve decompression is still under debate [6, 13]. It is known that the optic nerve sheath is an anterior extension of the middle cranial fossa dura, which envelopes the canalicular optic nerve and condenses at its anterior end to a concentric fibrous ring known as the annulus of Zinn. Proponents of decompression of the nerve sheath note that the post-traumatic compartmental syndrome is best relieved by releasing the constricting sheath enveloping the nerve [3]. Thaker et al. [6] previously reported that the quantum of recovery was greater in patients with residual vision before surgery who underwent combined osseous decompression and optic nerve sheath incision than in patients of osseous decompression alone (46 and 33%, respectively). This suggests that the addition of optic nerve sheath incision to osseous decompression may improve the recovery in optic nerve injury, especially in subjects without optic canal fracture. In our previous studies, we routinely performed nerve sheath slitting during endoscopic optic nerve decompression without severe complication such as cerebrospinal fluid leakage and ophthalmic artery injury [4]. However, considering nerve sheath slitting may cause an increase in the risk of an occasional cerebrospinal fluid leakage and ophthalmic artery injury or a decrease in the efficacy by potentially disrupting the pial vessels contributing to nerve vascularity or disrupting the nerve fascicles, the efficacy of nerve sheath slitting has also been doubted by some authors. In this study, we sought to evaluate the efficacy and safety of osseous decompression alone. In contrast, we found that the ratio of improvement in subjects with osseous decompression and nerve sheath incision and subjects without nerve sheath incision was 61.2 and 65.1%, respectively, and there was no significant difference. These findings indicated that nerve sheath incision is not superior to osseous decompression alone in the efficacy of endoscopic optic nerve decompression in TON patients. Moreover, when we specifically compared the efficacy of endoscopic optic nerve decompression with and without nerve sheath incision in TON patients with residual vision preoperatively, we found that the ratio of improvement in the former group was slightly lower than in the latter group (64.2 and 71.4%, respectively), not favoring nerve sheath incision during endoscopic optic nerve decompression. Additionally, it is important to note the death of 1 TON patient after surgical decompression. In this young man with traumatic blindness, no cerebrospinal fluid leakage occurred in spite of nerve sheath incision during surgery. There was no evidence showing that the death-related cranial infection was caused by surgical decompression. After careful cadaver inspection and comprehensive consult, we postulate that the death of the TON patient who was just recovered from severe head injury and skull base fracture may have been hit by the cranial pathogens after administration of intravenous high-dose steroid. This complication reminded us of the fact that balancing the risk and benefit of surgical and medical treatment is important for TON patients with severe head injury and skull base fracture. We acknowledge that this study also contains some flaws. First, it was not a randomized, placebo-controlled clinical trial, so the effect of steroid cannot be completely excluded. Second, we failed to obtain a long-term outcome of this cohort on the prognosis of TON. This may weaken the power of our conclusion. However, since surgical decompression with nerve sheath incision did not show any additional advantage in this study, our findings may be beneficial to the establishment of a less invasive surgical decompression without nerve sheath incision. Further study is still required to validate our conclusion in this study.
49
ORL 2014;76:44–49 DOI: 10.1159/000358305
© 2014 S. Karger AG, Basel www.karger.com/orl
Xu et al.: Endoscopic Optic Nerve Decompression for Patients with Traumatic Optic Neuropathy: Is Nerve Sheath Incision Necessary?
In summary, our preliminary results suggest that nerve sheath incision is not obligatory for the improvement of visual acuity during endoscopic optic nerve decompression for the treatment of TON patients. Specifically, when compared with the efficacy of endoscopic optic nerve decompression with and without nerve sheath incision in TON patients with residual vision preoperatively, we found that the ratio of improvement favored no nerve sheath incision during surgery. Acknowledgements This study was supported by grants from the National Natural Science Fund of China (No. 81070771, 81070772) and a grant from the Ministry of Hygiene (No. 201202005) and Program for New Century Excellent Talents in University (No. NCET-10-0851).
Disclosure Statement The authors have no conflicts of interest to declare pertaining to this article.
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