Auris Nasus Larynx 42 (2015) 113–118
Contents lists available at ScienceDirect
Auris Nasus Larynx journal homepage: www.elsevier.com/locate/anl
Fluorescence-assisted visualization of facial nerve during mastoidectomy: A novel technique for preventing iatrogenic facial paralysis Shao-Ching Chen a,d, Mao-Che Wang b,d, Wei-Hsin Wang a,d, Cheng-Chia Lee a,d, Tsui-Fen Yang c,d, Chun-Fu Lin a,d, Jui-To Wang a,d,**, Chih-Hsiang Liao a,d, Chih-Chang Chang a,d, Min-Hsiung Chen a,d, Yang-Hsin Shih a,d, Sanford P.C. Hsu a,d,* a
Department of Neurosurgery, Neurological Institute, Taipei Veterans General Hospital, Taipei, Taiwan Department of Otolaryngology, Taipei Veterans General Hospital, Taipei, Taiwan Department of Rehabilitation, Taipei Veterans General Hospital, Taipei, Taiwan d School of Medicine, National Yang-Ming University, Taipei, Taiwan b c
A R T I C L E I N F O
A B S T R A C T
Article history: Received 9 April 2014 Accepted 13 August 2014 Available online 6 September 2014
Objective: Mastoidectomy can be risky due to the chance of iatrogenic facial nerve dysfunction. Avoiding injuries to the mastoid segment of the facial nerve is mandatory when drilling the bone. With advancements in intraoperative near-infrared indocyanine green (ICG) video angiography, we describe the application of a novel fluorescent guidance technique during mastoidectomies to identify the facial canal with safety. Methods: Mastoidectomies were performed as the key step in the presigmoid, petrosal or translabyrinthine approaches in 16 patients with different pathologies located at the cerebellopontine angle or petroclival region. After the facial canal was drilled to paper thin, ICG was injected via the central venous catheter. Compared with the dark bony portion, the vessels inside the vasa nervorum were highlighted as a result. The fluorescence guides the operator through the course of the facial nerve and facilitates opening of the internal auditory canal and the dissection of tumors. Results: All 16 facial nerves were recognized during mastoidectomies under fluorescence guidance for varied periods of enhancing time (range, 23–50 s). In all, one to four attempts after repeated drilling works to enhance the facial nerve were required before these nerves could be clearly seen. The tumor resection procedure yielded the following results: grossly total removal in seven patients, near total removal in five, and subtotal removal in three. Complete obliteration of a giant vertebral artery aneurysm in one patient was seen in the follow-up angiogram. The post-mastoidectomy facial nerve function, examined by triggered EMG, was preserved in all 16 patients, and no patients had postoperative facial palsy worse than House–Brackmann grade IV after 6 months of follow-up. Conclusion: With this novel technique, the course of the facial nerve can be confirmed during mastoidectomy, which reduces the possibility of iatrogenic facial nerve dysfunction. This fluorescence technique is especially helpful in establishing confidence and shortening the learning curve for beginners at mastoidectomies. ß 2014 Elsevier Ireland Ltd. All rights reserved.
Keywords: Facial nerve Mastoidectomy Cerebellopontine angle Petroclival Fluorescence ICG Electrophysiological neuromonitoring
Abbreviations: CMAP, compound muscular action potentials; EMG, electromyography; IAC, internal auditory canal; ICG, indocyanine green. * Corresponding author at: Department of Neurosurgery, Neurological Institute, Taipei Veterans General Hospital, 17f, 201, Section 2, Shih-Pai Road, Taipei 112, Taiwan. Tel.: +886 2 2875 7491; fax: +886 2 2875 7588. ** Co-corresponding author at: Department of Neurosurgery, Neurological Institute, Taipei Veterans General Hospital, 17f, 201, Section 2, Shih-Pai Road, Taipei 112, Taiwan. Tel.: +886 2 2875 7491; fax: +886 2 2875 7588. E-mail addresses: [email protected], [email protected] (Sanford P.C. Hsu). http://dx.doi.org/10.1016/j.anl.2014.08.008 0385-8146/ß 2014 Elsevier Ireland Ltd. All rights reserved.
114
S.-C. Chen et al. / Auris Nasus Larynx 42 (2015) 113–118
1. Introduction
‘‘optical window’’ of tissue. It has a maximum absorption wavelength in water of 780 nm and demonstrates maximum fluorescence in human blood at an excitation wavelength of 820 nm. In a darkened operating room, the intravascular dye was visualized using an operating microscope (OPMI Pentero; Carl Zeiss Meditec) equipped with an additional fluorescent light source (wavelength 700–850 nm).
Iatrogenic facial nerve injury can be the most devastating complication during mastoidectomy [1]. The reported incidence is from 0.6% to 3.6% [2,3]. To assure safe bone drilling while performing mastoid surgery, the focus previously was put on knowledge about anatomies and neuromonitoring [4,5]. With the recent advancement of the fluorescence technique, a new method has been developed to recognize nerve tissue intraoperatively [6]. Near-infrared indocyanine green (ICG) video angiography, one of the intraoperative fluorescence tools, demonstrates clear vascular flow dynamics that can provide real-time information during neurological surgeries. ICG helps neurosurgeons to confirm the patency of vessels and the obliteration of clipped aneurysms [7], and to identify venous sinus and tumor locations during meningioma and pituitary tumor surgeries [8,9], the presence of tiny early venous drainage in arteriovenous malformations [10], and other conditions [11]. The use of ICG may complement other techniques using fluorescent dyes, in that it provides information regarding regional blood flow and capillary density. In the current study, we report our pilot experience with an intraoperative fluorescence technique in the mastoidectomy procedure, and the first use of ICG as a fluorescent contrast dye to examine the tissue microvasculature of a facial nerve. Since iatrogenic facial nerve palsy often resulted from facial nerve injury during mastoidectomy [12], this simple and useful adjuvant tool may improve the quality of neurological or otological surgeries.
The patient is put in a supine position with the head turned toward the contralateral side relative to the lesion at about a 458 angle with the floor. The head is fixed by Mayfield skull clamp pins. Then, the subdermal needles are placed for electrophysiological monitoring. After positioning, the patient is tied to the table with towels to avoid the patient falling while turning the table intraoperatively. A C-shaped incision is planned about 2.5 cm behind the ear. The incision should cover the mastoid process, sigmoid sinus, transverse sinus and supratentorial region. It is then deepened with electrical cauterization until pericranium. The pericranium is preserved to use in wound closure as an additional layer to avoid CSF leakage. The temporalis muscle is separated and retracted anteriorly, and the sternocleidomastoid muscle is separated and retracted inferiorly. At the end of wound closure, part of the muscle can be harvested as a graft to seal the bony window (aditus) near the incus, which is created during mastoidectomy.
2. Materials and methods
2.4. Injection of indocyanine green
2.1. Patient population
After the bony structure of the facial canal is skeletonized until paper thin, the operative field is irrigated to remove the bone dust and to achieve meticulous hemostasis before ICG injection. The fluorescein is prepared with 5 cc pure ICG in a 10 cc syringe and the syringe is then connected to the central venous catheter. The microscope is turned to the infrared 800 mode and the light in the operation room is turned off to achieve better visualization of fluorescein. Then, after all preparations have been completed, the ICG is injected by intravenous push. On most occasions, the enhanced facial nerve can be seen within 1 min after injection. The thick bone that covers the facial nerve on the outer layer has very slow blood flow compared to the nerve fiber. The significant difference allows neurosurgeons to identify the facial nerve while drilling the mastoid bone, because the cortical bone will appear very dark. The course of the facial nerve will be highlighted because both the blood supply inside the perineurium and the gross blood supply inside the facial canal will be visualized after ICG injection (Fig. 1A and B, video). Sometimes, the thick bone that constitutes the facial canal in the outer layer is not sufficiently skeletonized, so the fluorescenceenhanced facial nerve cannot be seen. A second or multiple attempts of ICG injection and fluorescence examination can be performed after repeated drilling works until the course of the facial nerve is highlighted clearly. The recommended dose is 0.2– 0.5 mg/kg per day in humans, and the maximum recommended dose per day is 5 mg/kg.
This study was performed from June 2011 to March 2013. A total of 16 patients who had different pathologies with the main parts located at the cerebellopontine angle or petroclival region underwent craniotomies at Taipei Veterans General Hospital. There were 5 male and 11 female patients, with ages ranging from 16 to 63 years (median: 41 years). The main symptoms were related to hearing impairment and unsteady gait. All patients but four underwent the cerebellopontine surgeries as the primary treatment. One female patient with petroclival meningioma had surgery for removal of a tuberculum sellar part tumor in another hospital before being admitted to our ward. A 28-year-old male patient with craniopharyngioma involving the 3rd ventricular floor, right temporal base, and cerebellopontine angle had had a total of 5 craniotomies since he was 12 years old before coming to our hospital. A female patient had gammaknife radiosurgery to control her vestibular schwannoma, but it was in vain. And another female patient underwent surgical excision for her petroclival meningioma with subtotal removal. The 16 patients underwent certain surgical approaches involving mastoidectomy. The exclusion criteria consisted of patients with a serviceable hearing function, aged 90% resection (nearly total resection), and 3 in 15 (20%) had subtotal resection of around 70–90% of the original tumor size. The patient with a giant vertebral artery aneurysm experienced complete obliteration, as seen in the follow-up digital subtraction angiography. There was no perioperative morbidity or mortality, except progression of facial palsy in 5 patients. The surgical results and the postoperative facial nerve function of the investigated patients who completed the study procedure are summarized in Table 1.
ICG is a near-infrared fluorescent tricarbocyanine dye that was approved by the Food and Drug Administration in 1956 for cardiocirculatory and liver function diagnostic uses, and in 1969 for research and diagnosis of subretinal processes in the choroid. The original applications of near-infrared ICG video angiography in the field of neurological surgeries were to detect larger vessel diseases or to confirm the treatment outcome, such as complete obliteration of a clipped intracranial aneurysm [13]. Several years later, some neurosurgeons began to use ICG video angiography to investigate the small vessels of brain tumors and attempted to clarify the margin of a tumor [8,9]. From the previous study, the overall rate of mild, moderate, and severe side effects of ICG were only 0.15%, 0.2%, and 0.05%. The rate of death is 3/1,000,000. The toxicity has been classified as low. Effects such as anaphylactic shock, or urticarial only occurred in few case reports. The risk of ICG allergy is related to chronic kidney impairment, and previous anaphylactic reaction to iodine [14–17]. In the current study, the authors further introduced the use of the novel fluorescent technique to visualize the facial nerve by enhancing the nutritional vessels of the nerve (vasa nervorum), and its accompanying vessels in the facial canal. The structure of
116
Table 1 Patients with cerebellopontine angle tumors underwent ICG video angiography for facial nerve localization during mastoidectomy. Age, sex
Pathology
Tumor size (cm)
IAC involvement
Prior management
Surgical approach
Fluorescein images emergence after ICG injection (min0 sec00 )
Times of ICG injection before definite facial localization
Triggered EMG for facial nerve recognition
MEP latency of facial nerve monitoring
Degree of resection
Facial nerve function (pre-op ! post-op)a
1 2
47, F 28, F
Vestibular Schwannoma Petroclival Meningioma
3.9 >10
Yes No
Translabyrinthine Transpetrosal
33 36
3 4
Yes Yes
No prolongation No prolongation
Near total Subtotal
Gr. 1 ! Gr.1 Gr. 2 ! Gr. 2
3 4 5
28, F 31, M 28, M
Vestibular Schwannoma Vestibular Schwannoma Craniopharyngioma
5.4 3.4 4.8
Yes Yes No
Translabyrinthine Translabyrinthine Transpetrosal
31 27 29
2 1 2
Yes Yes Yes
No prolongation No prolongation No prolongation
Subtotalb Grossly total Grossly totalc
Gr. 3 ! Gr 2. Gr. 1 ! Gr 2 Gr. 4 ! Gr 4
6 7 8 9 10 11 12 13 14 15
45, 54, 63, 38, 34, 40, 54, 42, 61, 54,
3.8 3.9 3.6 3.0 3.5 3.3 3.9 3.7 3.8 3.2
No Yes Yes Yes Yes Yes Yes Yes Yes No
Transpetrosal Translabyrinthine Translabyrinthine Presigmoid Translabyrinthine Translabyrinthine Translabyrinthine Translabyrinthine Transpetrosal Translabyrinthine
36 26 23 49 41 38 30 28 45 50
1 1 2 2 1 1 1 1 1 2
Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
No No No No No No No No No No
Near total Near total Grossly total Near total Near total Subtotal Grossly total Grossly total Grossly total Grossly total
Gr. Gr. Gr. Gr. Gr. Gr. Gr. Gr. Gr. Gr.
16
16, M
Petroclival Meningioma Vestibular Schwannoma Vestibular Schwannoma Vestibular Schwannoma Vestibular Schwannoma Vestibular Schwannoma Vestibular Schwannoma Vestibular Schwannoma Petroclival Meningioma Cerebellopontine Angle Meningioma Giant VA Aneurysm
Nil Surgical resection x 1 Nil Nil Surgical resection x 15 Surgical resection 1 Nil Nil Nil GKRS Nil Nil Nil Nil Nil
4
No
Nil
Transpetrosal
26
1
Yes
No prolongation
Complete Obliteration
Gr. 2 ! Gr 1
F F F F F M F M F F
prolongation prolongation prolongation prolongation prolongation prolongation prolongation prolongation prolongation prolongation
2 ! Gr 1 ! Gr 1 ! Gr 1 ! Gr 1 ! Gr 1 ! Gr 2 ! Gr 2 ! Gr 2 ! Gr 2 ! Gr
1 2 3 1 1 1 3 3 2 2
Abbreviation: cm: centimeter, EMG: electromyography, GKRS: gamma-knife radiosurgery, Gr: grade, m: month, IAC: intra-auricular canal, ICG: indocyanine green, MEP: motor evoke potential, No.: number, and op: operation. a House–Brackmann facial palsy grade system (pre-op ! 6 months post-op). b The tumor involved both cerebellopontine angle and infratemporal fossa. Only the cerebellopontine angle part was removed. c The tumor involved 3rd ventricular floor, right temporal base, and cerebellopontine area with brainstem compression. Total removal of tumor within posterior fossa was shown by follow-up MRI.
S.-C. Chen et al. / Auris Nasus Larynx 42 (2015) 113–118
Case no.
S.-C. Chen et al. / Auris Nasus Larynx 42 (2015) 113–118
these blood vessels includes branches both in the facial canal and the epineurium of the facial nerve, with formation of capillary networks from the perineurium to the endoneurium [18]; and from these, nerve roots are visualized by highlighting their nutritional vessels. In 1954, Blunt identified the fine vessels in the facial canal first, and most of them came from both the petrosal branch of the middle meningeal artery and the stylomastoid artery [19]. Then, several reports qualified and quantified the vascularity and spatial relationships of the content of the facial canals, including the size of the vessels in a canal [20–22]. In 2010, Gragnaniello et al. reported eight cadaver mastoidectomies, demonstrating facial nerve and semicircular canals under the guidance of fluorescence. During skeletonizing of the facial nerve and semicircular canals in the cadaver, the fluorescence guided the drilling, displaying air cells that were safe to remove [23]. In 2013, Kim et al. utilized ICG video angiography to identify nerves in superior cluneal entrapment neuropathy. They showed that the superior cluneal nerve was penetrated and was entrapped by the thoracolumbar fascia through the orifice just before crossing over the iliac crest in all patients. ICG video angiography demonstrated the vasa nervorum clearly and was the optimal technique to confirm release of peripheral nerve entrapment [6]. Based on these laboratory and clinical findings, we began to use near-infrared ICG video angiography in the mastoidectomy procedure. Mastoidectomy is a drilling procedure that facilitates exposing the middle and inner ear. The procedures can be as simple as a mastoidectomy and a translabyrinthine approach, or as complex as a transpetrosal approach. The indications include chronic otitis media, cholesteatoma, vestibular schwannoma, meningioma, and temporal bone paragangliomas. For neurosurgeons or neurotologists, intraoperative identification of facial nerve structures is a major challenge when attempting to approach cerebellopontine angle tumors. While drilling the mastoid, the operator may encounter several difficulties: the distorted mastoid resulted from the pathological lesions, and anomalies and variations in the temporal bone anatomy (dehiscence of the facial canal, poorly aerated mastoid, or post-mastoiditis mastoid) [24]. All these difficulties increase the possibility of iatrogenic facial nerve injury. The application of near-infrared ICG video angiography during mastoidectomy is based on the peculiar difference between cortical bone and facial nerve. The thick bone that constitutes the facial canal in the outer layer has a very slow blood flow compared to the nerve fiber. This peculiar difference allows neurosurgeons or otologists to recognize the facial nerve while drilling the mastoid bone, because the cortical bone will appear very dark. Although a report demonstrated the various diameters of the arteries in three portions of the facial canal (labyrinth, tympanic, and mastoid portions) [20], the fluorescene-enhanced nerve route can be easily traced. Therefore, utilizing nearinfrared ICG video angiography as a guide in the mastoidectomy procedure may help neurosurgeons or otologists find the facial nerve along with the anatomical landmark. In our practice, the anatomy of the mastoid, electrophysiological stimulation of the facial nerve, and enhancing the facial nerve by near-infrared ICG video angiography can work together to locate the facial nerve accurately, and eliminate the complication of facial nerve injuries. It is especially useful in cases with anatomical anomalies. Once such anomalies are suspected in preoperatively image study, double checking procedure should be recommended. This is valuable to confirm the location of facial nerve in temporal bone. For more than three decades, intravenous ICG dye has been used in ophthalmology with a clinically relevant complication rate of
Contents lists available at ScienceDirect
Auris Nasus Larynx journal homepage: www.elsevier.com/locate/anl
Fluorescence-assisted visualization of facial nerve during mastoidectomy: A novel technique for preventing iatrogenic facial paralysis Shao-Ching Chen a,d, Mao-Che Wang b,d, Wei-Hsin Wang a,d, Cheng-Chia Lee a,d, Tsui-Fen Yang c,d, Chun-Fu Lin a,d, Jui-To Wang a,d,**, Chih-Hsiang Liao a,d, Chih-Chang Chang a,d, Min-Hsiung Chen a,d, Yang-Hsin Shih a,d, Sanford P.C. Hsu a,d,* a
Department of Neurosurgery, Neurological Institute, Taipei Veterans General Hospital, Taipei, Taiwan Department of Otolaryngology, Taipei Veterans General Hospital, Taipei, Taiwan Department of Rehabilitation, Taipei Veterans General Hospital, Taipei, Taiwan d School of Medicine, National Yang-Ming University, Taipei, Taiwan b c
A R T I C L E I N F O
A B S T R A C T
Article history: Received 9 April 2014 Accepted 13 August 2014 Available online 6 September 2014
Objective: Mastoidectomy can be risky due to the chance of iatrogenic facial nerve dysfunction. Avoiding injuries to the mastoid segment of the facial nerve is mandatory when drilling the bone. With advancements in intraoperative near-infrared indocyanine green (ICG) video angiography, we describe the application of a novel fluorescent guidance technique during mastoidectomies to identify the facial canal with safety. Methods: Mastoidectomies were performed as the key step in the presigmoid, petrosal or translabyrinthine approaches in 16 patients with different pathologies located at the cerebellopontine angle or petroclival region. After the facial canal was drilled to paper thin, ICG was injected via the central venous catheter. Compared with the dark bony portion, the vessels inside the vasa nervorum were highlighted as a result. The fluorescence guides the operator through the course of the facial nerve and facilitates opening of the internal auditory canal and the dissection of tumors. Results: All 16 facial nerves were recognized during mastoidectomies under fluorescence guidance for varied periods of enhancing time (range, 23–50 s). In all, one to four attempts after repeated drilling works to enhance the facial nerve were required before these nerves could be clearly seen. The tumor resection procedure yielded the following results: grossly total removal in seven patients, near total removal in five, and subtotal removal in three. Complete obliteration of a giant vertebral artery aneurysm in one patient was seen in the follow-up angiogram. The post-mastoidectomy facial nerve function, examined by triggered EMG, was preserved in all 16 patients, and no patients had postoperative facial palsy worse than House–Brackmann grade IV after 6 months of follow-up. Conclusion: With this novel technique, the course of the facial nerve can be confirmed during mastoidectomy, which reduces the possibility of iatrogenic facial nerve dysfunction. This fluorescence technique is especially helpful in establishing confidence and shortening the learning curve for beginners at mastoidectomies. ß 2014 Elsevier Ireland Ltd. All rights reserved.
Keywords: Facial nerve Mastoidectomy Cerebellopontine angle Petroclival Fluorescence ICG Electrophysiological neuromonitoring
Abbreviations: CMAP, compound muscular action potentials; EMG, electromyography; IAC, internal auditory canal; ICG, indocyanine green. * Corresponding author at: Department of Neurosurgery, Neurological Institute, Taipei Veterans General Hospital, 17f, 201, Section 2, Shih-Pai Road, Taipei 112, Taiwan. Tel.: +886 2 2875 7491; fax: +886 2 2875 7588. ** Co-corresponding author at: Department of Neurosurgery, Neurological Institute, Taipei Veterans General Hospital, 17f, 201, Section 2, Shih-Pai Road, Taipei 112, Taiwan. Tel.: +886 2 2875 7491; fax: +886 2 2875 7588. E-mail addresses: [email protected], [email protected] (Sanford P.C. Hsu). http://dx.doi.org/10.1016/j.anl.2014.08.008 0385-8146/ß 2014 Elsevier Ireland Ltd. All rights reserved.
114
S.-C. Chen et al. / Auris Nasus Larynx 42 (2015) 113–118
1. Introduction
‘‘optical window’’ of tissue. It has a maximum absorption wavelength in water of 780 nm and demonstrates maximum fluorescence in human blood at an excitation wavelength of 820 nm. In a darkened operating room, the intravascular dye was visualized using an operating microscope (OPMI Pentero; Carl Zeiss Meditec) equipped with an additional fluorescent light source (wavelength 700–850 nm).
Iatrogenic facial nerve injury can be the most devastating complication during mastoidectomy [1]. The reported incidence is from 0.6% to 3.6% [2,3]. To assure safe bone drilling while performing mastoid surgery, the focus previously was put on knowledge about anatomies and neuromonitoring [4,5]. With the recent advancement of the fluorescence technique, a new method has been developed to recognize nerve tissue intraoperatively [6]. Near-infrared indocyanine green (ICG) video angiography, one of the intraoperative fluorescence tools, demonstrates clear vascular flow dynamics that can provide real-time information during neurological surgeries. ICG helps neurosurgeons to confirm the patency of vessels and the obliteration of clipped aneurysms [7], and to identify venous sinus and tumor locations during meningioma and pituitary tumor surgeries [8,9], the presence of tiny early venous drainage in arteriovenous malformations [10], and other conditions [11]. The use of ICG may complement other techniques using fluorescent dyes, in that it provides information regarding regional blood flow and capillary density. In the current study, we report our pilot experience with an intraoperative fluorescence technique in the mastoidectomy procedure, and the first use of ICG as a fluorescent contrast dye to examine the tissue microvasculature of a facial nerve. Since iatrogenic facial nerve palsy often resulted from facial nerve injury during mastoidectomy [12], this simple and useful adjuvant tool may improve the quality of neurological or otological surgeries.
The patient is put in a supine position with the head turned toward the contralateral side relative to the lesion at about a 458 angle with the floor. The head is fixed by Mayfield skull clamp pins. Then, the subdermal needles are placed for electrophysiological monitoring. After positioning, the patient is tied to the table with towels to avoid the patient falling while turning the table intraoperatively. A C-shaped incision is planned about 2.5 cm behind the ear. The incision should cover the mastoid process, sigmoid sinus, transverse sinus and supratentorial region. It is then deepened with electrical cauterization until pericranium. The pericranium is preserved to use in wound closure as an additional layer to avoid CSF leakage. The temporalis muscle is separated and retracted anteriorly, and the sternocleidomastoid muscle is separated and retracted inferiorly. At the end of wound closure, part of the muscle can be harvested as a graft to seal the bony window (aditus) near the incus, which is created during mastoidectomy.
2. Materials and methods
2.4. Injection of indocyanine green
2.1. Patient population
After the bony structure of the facial canal is skeletonized until paper thin, the operative field is irrigated to remove the bone dust and to achieve meticulous hemostasis before ICG injection. The fluorescein is prepared with 5 cc pure ICG in a 10 cc syringe and the syringe is then connected to the central venous catheter. The microscope is turned to the infrared 800 mode and the light in the operation room is turned off to achieve better visualization of fluorescein. Then, after all preparations have been completed, the ICG is injected by intravenous push. On most occasions, the enhanced facial nerve can be seen within 1 min after injection. The thick bone that covers the facial nerve on the outer layer has very slow blood flow compared to the nerve fiber. The significant difference allows neurosurgeons to identify the facial nerve while drilling the mastoid bone, because the cortical bone will appear very dark. The course of the facial nerve will be highlighted because both the blood supply inside the perineurium and the gross blood supply inside the facial canal will be visualized after ICG injection (Fig. 1A and B, video). Sometimes, the thick bone that constitutes the facial canal in the outer layer is not sufficiently skeletonized, so the fluorescenceenhanced facial nerve cannot be seen. A second or multiple attempts of ICG injection and fluorescence examination can be performed after repeated drilling works until the course of the facial nerve is highlighted clearly. The recommended dose is 0.2– 0.5 mg/kg per day in humans, and the maximum recommended dose per day is 5 mg/kg.
This study was performed from June 2011 to March 2013. A total of 16 patients who had different pathologies with the main parts located at the cerebellopontine angle or petroclival region underwent craniotomies at Taipei Veterans General Hospital. There were 5 male and 11 female patients, with ages ranging from 16 to 63 years (median: 41 years). The main symptoms were related to hearing impairment and unsteady gait. All patients but four underwent the cerebellopontine surgeries as the primary treatment. One female patient with petroclival meningioma had surgery for removal of a tuberculum sellar part tumor in another hospital before being admitted to our ward. A 28-year-old male patient with craniopharyngioma involving the 3rd ventricular floor, right temporal base, and cerebellopontine angle had had a total of 5 craniotomies since he was 12 years old before coming to our hospital. A female patient had gammaknife radiosurgery to control her vestibular schwannoma, but it was in vain. And another female patient underwent surgical excision for her petroclival meningioma with subtotal removal. The 16 patients underwent certain surgical approaches involving mastoidectomy. The exclusion criteria consisted of patients with a serviceable hearing function, aged 90% resection (nearly total resection), and 3 in 15 (20%) had subtotal resection of around 70–90% of the original tumor size. The patient with a giant vertebral artery aneurysm experienced complete obliteration, as seen in the follow-up digital subtraction angiography. There was no perioperative morbidity or mortality, except progression of facial palsy in 5 patients. The surgical results and the postoperative facial nerve function of the investigated patients who completed the study procedure are summarized in Table 1.
ICG is a near-infrared fluorescent tricarbocyanine dye that was approved by the Food and Drug Administration in 1956 for cardiocirculatory and liver function diagnostic uses, and in 1969 for research and diagnosis of subretinal processes in the choroid. The original applications of near-infrared ICG video angiography in the field of neurological surgeries were to detect larger vessel diseases or to confirm the treatment outcome, such as complete obliteration of a clipped intracranial aneurysm [13]. Several years later, some neurosurgeons began to use ICG video angiography to investigate the small vessels of brain tumors and attempted to clarify the margin of a tumor [8,9]. From the previous study, the overall rate of mild, moderate, and severe side effects of ICG were only 0.15%, 0.2%, and 0.05%. The rate of death is 3/1,000,000. The toxicity has been classified as low. Effects such as anaphylactic shock, or urticarial only occurred in few case reports. The risk of ICG allergy is related to chronic kidney impairment, and previous anaphylactic reaction to iodine [14–17]. In the current study, the authors further introduced the use of the novel fluorescent technique to visualize the facial nerve by enhancing the nutritional vessels of the nerve (vasa nervorum), and its accompanying vessels in the facial canal. The structure of
116
Table 1 Patients with cerebellopontine angle tumors underwent ICG video angiography for facial nerve localization during mastoidectomy. Age, sex
Pathology
Tumor size (cm)
IAC involvement
Prior management
Surgical approach
Fluorescein images emergence after ICG injection (min0 sec00 )
Times of ICG injection before definite facial localization
Triggered EMG for facial nerve recognition
MEP latency of facial nerve monitoring
Degree of resection
Facial nerve function (pre-op ! post-op)a
1 2
47, F 28, F
Vestibular Schwannoma Petroclival Meningioma
3.9 >10
Yes No
Translabyrinthine Transpetrosal
33 36
3 4
Yes Yes
No prolongation No prolongation
Near total Subtotal
Gr. 1 ! Gr.1 Gr. 2 ! Gr. 2
3 4 5
28, F 31, M 28, M
Vestibular Schwannoma Vestibular Schwannoma Craniopharyngioma
5.4 3.4 4.8
Yes Yes No
Translabyrinthine Translabyrinthine Transpetrosal
31 27 29
2 1 2
Yes Yes Yes
No prolongation No prolongation No prolongation
Subtotalb Grossly total Grossly totalc
Gr. 3 ! Gr 2. Gr. 1 ! Gr 2 Gr. 4 ! Gr 4
6 7 8 9 10 11 12 13 14 15
45, 54, 63, 38, 34, 40, 54, 42, 61, 54,
3.8 3.9 3.6 3.0 3.5 3.3 3.9 3.7 3.8 3.2
No Yes Yes Yes Yes Yes Yes Yes Yes No
Transpetrosal Translabyrinthine Translabyrinthine Presigmoid Translabyrinthine Translabyrinthine Translabyrinthine Translabyrinthine Transpetrosal Translabyrinthine
36 26 23 49 41 38 30 28 45 50
1 1 2 2 1 1 1 1 1 2
Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
No No No No No No No No No No
Near total Near total Grossly total Near total Near total Subtotal Grossly total Grossly total Grossly total Grossly total
Gr. Gr. Gr. Gr. Gr. Gr. Gr. Gr. Gr. Gr.
16
16, M
Petroclival Meningioma Vestibular Schwannoma Vestibular Schwannoma Vestibular Schwannoma Vestibular Schwannoma Vestibular Schwannoma Vestibular Schwannoma Vestibular Schwannoma Petroclival Meningioma Cerebellopontine Angle Meningioma Giant VA Aneurysm
Nil Surgical resection x 1 Nil Nil Surgical resection x 15 Surgical resection 1 Nil Nil Nil GKRS Nil Nil Nil Nil Nil
4
No
Nil
Transpetrosal
26
1
Yes
No prolongation
Complete Obliteration
Gr. 2 ! Gr 1
F F F F F M F M F F
prolongation prolongation prolongation prolongation prolongation prolongation prolongation prolongation prolongation prolongation
2 ! Gr 1 ! Gr 1 ! Gr 1 ! Gr 1 ! Gr 1 ! Gr 2 ! Gr 2 ! Gr 2 ! Gr 2 ! Gr
1 2 3 1 1 1 3 3 2 2
Abbreviation: cm: centimeter, EMG: electromyography, GKRS: gamma-knife radiosurgery, Gr: grade, m: month, IAC: intra-auricular canal, ICG: indocyanine green, MEP: motor evoke potential, No.: number, and op: operation. a House–Brackmann facial palsy grade system (pre-op ! 6 months post-op). b The tumor involved both cerebellopontine angle and infratemporal fossa. Only the cerebellopontine angle part was removed. c The tumor involved 3rd ventricular floor, right temporal base, and cerebellopontine area with brainstem compression. Total removal of tumor within posterior fossa was shown by follow-up MRI.
S.-C. Chen et al. / Auris Nasus Larynx 42 (2015) 113–118
Case no.
S.-C. Chen et al. / Auris Nasus Larynx 42 (2015) 113–118
these blood vessels includes branches both in the facial canal and the epineurium of the facial nerve, with formation of capillary networks from the perineurium to the endoneurium [18]; and from these, nerve roots are visualized by highlighting their nutritional vessels. In 1954, Blunt identified the fine vessels in the facial canal first, and most of them came from both the petrosal branch of the middle meningeal artery and the stylomastoid artery [19]. Then, several reports qualified and quantified the vascularity and spatial relationships of the content of the facial canals, including the size of the vessels in a canal [20–22]. In 2010, Gragnaniello et al. reported eight cadaver mastoidectomies, demonstrating facial nerve and semicircular canals under the guidance of fluorescence. During skeletonizing of the facial nerve and semicircular canals in the cadaver, the fluorescence guided the drilling, displaying air cells that were safe to remove [23]. In 2013, Kim et al. utilized ICG video angiography to identify nerves in superior cluneal entrapment neuropathy. They showed that the superior cluneal nerve was penetrated and was entrapped by the thoracolumbar fascia through the orifice just before crossing over the iliac crest in all patients. ICG video angiography demonstrated the vasa nervorum clearly and was the optimal technique to confirm release of peripheral nerve entrapment [6]. Based on these laboratory and clinical findings, we began to use near-infrared ICG video angiography in the mastoidectomy procedure. Mastoidectomy is a drilling procedure that facilitates exposing the middle and inner ear. The procedures can be as simple as a mastoidectomy and a translabyrinthine approach, or as complex as a transpetrosal approach. The indications include chronic otitis media, cholesteatoma, vestibular schwannoma, meningioma, and temporal bone paragangliomas. For neurosurgeons or neurotologists, intraoperative identification of facial nerve structures is a major challenge when attempting to approach cerebellopontine angle tumors. While drilling the mastoid, the operator may encounter several difficulties: the distorted mastoid resulted from the pathological lesions, and anomalies and variations in the temporal bone anatomy (dehiscence of the facial canal, poorly aerated mastoid, or post-mastoiditis mastoid) [24]. All these difficulties increase the possibility of iatrogenic facial nerve injury. The application of near-infrared ICG video angiography during mastoidectomy is based on the peculiar difference between cortical bone and facial nerve. The thick bone that constitutes the facial canal in the outer layer has a very slow blood flow compared to the nerve fiber. This peculiar difference allows neurosurgeons or otologists to recognize the facial nerve while drilling the mastoid bone, because the cortical bone will appear very dark. Although a report demonstrated the various diameters of the arteries in three portions of the facial canal (labyrinth, tympanic, and mastoid portions) [20], the fluorescene-enhanced nerve route can be easily traced. Therefore, utilizing nearinfrared ICG video angiography as a guide in the mastoidectomy procedure may help neurosurgeons or otologists find the facial nerve along with the anatomical landmark. In our practice, the anatomy of the mastoid, electrophysiological stimulation of the facial nerve, and enhancing the facial nerve by near-infrared ICG video angiography can work together to locate the facial nerve accurately, and eliminate the complication of facial nerve injuries. It is especially useful in cases with anatomical anomalies. Once such anomalies are suspected in preoperatively image study, double checking procedure should be recommended. This is valuable to confirm the location of facial nerve in temporal bone. For more than three decades, intravenous ICG dye has been used in ophthalmology with a clinically relevant complication rate of
