Skull Base Reconstruction Using a Temporoparietal Galeal Flap in Simultaneous Transnasal and Transcranial Surgery for the Prevention of Carotid Blowout Syndrome: A Report of 3 Cases

Abstract

Background  Carotid blowout syndrome (CBS) is a rare complication that usually occurs after removal of head and neck tumors. Since transnasal skull base surgery allows a wide exposure of the ventral skull base, neurosurgeons should pay attention to prevent this devastating complication. We present, three cases involving exposure of the internal carotid artery (ICA) at the skull base during the simultaneous transnasal and transcranial approach.

Case Description  The first patient was a 69-year-old man with a recurrent chordoma. The exposed ICA was covered by an abdominal fat graft and nasoseptal flap, but he experienced CBS 2 months later and died. The second patient was a 66-year-old man with an intraosseous cavernous angioma of the petrous bone. The exposed ICA was covered by a temporoparietal galeal flap (TPGF), abdominal fat graft, and nasoseptal flap. The third patient was a 73-year-old man with skull base radiation necrosis and intracerebral abscess after proton beam therapy for orbital adenoid cystic carcinoma. The exposed ICA was covered by TPGF. The second and third patients' postoperative courses were uneventful.

Conclusion  Based on our experience, a nasoseptal flap alone may be insufficient to protect ICA. TPGF is therefore another available reconstruction option that may help prevent CBS.

Introduction

With the development of the endoscopic transnasal approach (eTNA), various ventral skull base lesions are being treated more frequently via eTNA-based protocols. However, some large skull base tumors may involve vital structures, rendering complete removal through the transnasal route alone difficult. For such cases, we use simultaneous transnasal and transcranial surgery. One of the good indications for such combined surgery is a lesion that extends around the internal carotid artery (ICA). This multidirectional approach increases the extent of tumor resection and allows wide exposure of ICA at the skull base. Carotid blowout syndrome (CBS) is an uncommon but devastating complication in patients with head and neck tumors and is associated with high mortality. ¹ Potential causes of CBS include carotid exposure, radiation therapy, wound breakdown, and wound infection. ^{2 3} In patients at high risk of CBS, protection of the carotid artery using a muscle flap is recommended. ⁴ If the ICA is likely to be exposed to the nasal cavity after skull base tumor resection, the neurosurgeon should take extra measures to prevent this fatal complication. To prevent wound breakdown and infection from the extracranial side, it is important to cover the exposed ICA using well-vascularized tissue.

To demonstrate the clinical characteristics and prevention method of CBS after simultaneous transnasal and transcranial approach, we, herein, present three illustrative cases. The surgical technique is demonstrated through illustrations and intraoperative photos.

Case Reports

Case 1

The patient was a 69-year-old man with a recurrent chordoma. Fifteen years prior, he had experienced right facial paresthesia and right abducens nerve palsy caused by a right middle fossa tumor, which involved the cavernous sinus. He underwent craniotomy for partial tumor resection and diagnosed chordoma. He underwent 50-Gy focal irradiation for a residual tumor. After radiation therapy, the tumor size remained stable for 10 years. Subsequently, however, the tumor demonstrated regrowth. Four years ago, he underwent the second craniotomy, and the tumor was completely resected. Stereotactic radiotherapy was performed for the resection cavity. The tumor recurred again a year ago, and he underwent a third craniotomy for the recurrent tumor, leaving a small residual tumor. The residual tumor exhibited rapid growth, and he was referred to our hospital. The tumor extended from the right Meckel's cave to the infratemporal fossa, clivus, and jugular tuberculum ( Fig. 1A–C ). To achieve complete resection, we planned a simultaneous transnasal and transcranial approach. The eTNA team removed the extracranial part of the tumor using a binostril approach ( Fig. 1D, E ). The transcranial approach team performed epi- and subdural subtemporal approach with zygomatic osteotomy and removed the intracranial part of the tumor ( Fig. 1F, G ). After tumor resection, the petrous ICA was widely exposed but not injured.

Fig. 1.

Magnetic resonance (MR) images, computed tomography (CT) images, intraoperative photographs, and angiographic images of Case #1. ( A–C ) Preoperative contrast-enhanced T1-weighted axial ( A ) and coronal ( B ) MR images. Blue arrowheads: tumor. ( C ) Preoperative three-dimensional (3D) CT image. Blue: tumor encasing petrous internal carotid artery (ICA). ( D–I ) Intraoperative photographs. ( D ) The surgical field of the transnasal approach team during tumor resection, showing the widely exposed petrous ICA ( black arrowheads ). Blue arrowhead: tumor around petrous apex, green arrowhead: sella turcica. ( E ) The surgical field of the transnasal approach team after tumor resection showing the preserved petrous ICA ( black arrowheads ). Area surrounded by blue dotted line: petrous bone defect connecting cranial and nasal cavities. ( F ) The surgical field of the transcranial approach team during tumor resection, showing the widely exposed petrous ICA ( black arrowheads ). Blue arrowhead: tumor around petrous apex. ( G ) The surgical field of the transcranial approach team after tumor resection showing the preserved petrous ICA ( black arrowheads ). Area surrounded by blue dotted line: petrous bone defect connecting cranial and nasal cavities. ( H ) The surgical field of the transnasal approach team during skull base reconstruction. Infratemporal dead space was packed with the abdominal fat graft ( yellow arrowhead ). Black arrowheads: petrous ICA. ( I ) The surgical field of the transnasal approach team after skull base reconstruction. A nasoseptal flap ( surrounded by green dotted line ) covered the bony borders of skull base defect, petrous ICA ( black dotted line ), and abdominal fat graft ( yellow dotted line ). ( J ) 3D-CT angiography revealed a rupture of the petrous ICA pseudoaneurysm ( red arrowhead ). ( K, L ) The bleeding was immediately halted by endovascular trapping of petrous ICA. Red arrowheads: petrous ICA pseudoaneurysm.

Skull Base Reconstruction

After tumor resection, the dural defect was closed using of a piece of the fascia lata. Infratemporal dead space was packed with the abdominal fat graft ( Fig. 1H ) and separated from the nasal space using a nasoseptal flap ( Fig. 1I ).

Postoperative Clinical Course

He was discharged from our hospital without postoperative wound infection or cerebrospinal fluid leakage. After 2 months, he experienced sudden massive nasal bleeding. Examination by three-dimensional computed tomographic angiography revealed a rupture of the petrous ICA pseudoaneurysm ( Fig. 1J ), and he underwent endovascular trapping of the petrous ICA ( Fig. 1K, L ). He had epidural abscess formation at the skull base and a foul-smelling purulent nasal discharge. Hemostasis was achieved, but his general condition worsened, and he died in the hospital.

Case 2

The patient was a 66-year-old man with an intraosseous cavernous angioma of the petrous bone. The tumor gradually grew, and he was referred to our hospital. As the tumor extended from the left petrous apex to the clivus and sphenoid sinus ( Fig. 2A–D ), we planned a simultaneous transnasal and transcranial approach. The eTNA team performed bilateral sphenoidotomy with harvesting of a vascularized nasoseptal flap. The tumor revealed a soft consistency, and tumor resection was mainly performed by eTNA using micro curettes and dissectors. The transcranial approach team performed the epidural subtemporal approach with zygomatic osteotomy, preserving the temporoparietal galea. The middle cranial fossa was drilled, and the tumor was separated from the maxillary, mandibular, and vidian nerves ( Fig. 2E ). Then, the petrous bone was drilled, and the tumor was separated from ICA ( Fig. 2F ). The surgical field after tumor resection showed the preserved nerves and widely exposed ICA ( Fig. 2G, H ).

Fig. 2.

Magnetic resonance (MR) images, computed tomography (CT) images, and intraoperative photographs of Case #2. ( A–C ) Preoperative contrast-enhanced T1-weighted axial MR images. ( D ) Preoperative three-dimensional (3D) CT showing an intraosseous cavernous angioma of the left petrous bone. ( E–H ) Intraoperative microscopic photographs. ( E ) The surgical field of the transcranial approach team during tumor resection. Anterior part of the tumor was removed through the interval between the maxillary and mandibular nerves. Green arrowhead: vidian canal. ( F ) The surgical field of the transcranial approach team during tumor resection. Posterior part of the tumor was removed through the petrous bone defect. Blue arrowhead: greater superficial petrosal nerve, red arrowhead: petrous ICA. ( G ) Upper: the surgical field of the transcranial approach team after tumor resection showing the preserved nerves and widely exposed internal carotid artery (ICA). Lower: black and white version of the upper picture. Red: ICA, Yellow: trigeminal nerve, Green: vidian nerve, Blue: greater superficial petrosal nerve, Purple: dura mater of the internal auditory meatus. ( H ) Upper: the surgical field of the transnasal approach team after tumor resection showing the preserved nerves and widely exposed ICA. Lower: black and white version of the upper picture. Red: ICA, Yellow: trigeminal nerve, Blue: greater superficial petrosal nerve, Purple: dura mater of the internal auditory meatus. ( I, J ) Postoperative 3D-CT images. Red: fixed zygomatic arch, Blue: fixed bone flap. ( K–M ) Postoperative contrast-enhanced T1-weighted axial MR images. V2 = maxillary nerve, V3 = mandibular nerve.

Skull Base Reconstruction

The steps involved in protective galeal wrap for the petrous portion of the exposed ICA are outlined in Fig. 3 . After bone drilling and tumor resection, the cranial cavity was connected to the nasal cavity through the skull base defect ( Fig. 3A, B ). For the skull base reconstruction, a unilateral temporoparietal galeal flap (TPGF) with adequate length and width was harvested ( Fig. 3C ). Briefly, subfollicular dissection of the skin was performed on the temporoparietal area. The parietal portion of TPGF was elevated with the periosteum, whereas the temporal portion of TPGF was elevated above the deep temporal fascia. The vascular pedicle of TPGF was superficial temporal artery. The flap was introduced into the nasal cavity through the petrous bone defect ( Fig. 3D ), and the flap tip was inserted back into the cranial cavity through the sphenoid bone defect ( Fig. 3E ), wrapping the petrous portion of ICA and mandibular nerve and separating the cranial cavity from the nasal cavity ( Fig. 3F ). Fig. 3G–L shows the endonasal endoscopic images of reconstruction of the skull base defect. The thinned dura around the internal auditory meatus was covered with a piece of the fascia lata ( Fig. 3G ). The two teams worked together to wrap TPGF around ICA ( Fig. 3H–J ). Then, the infratemporal dead space was packed with the abdominal fat graft and separated from the nasal space using a nasoseptal flap ( Fig. 3K, L ).

Fig. 3.

Illustrations and the intraoperative photographs of skull base reconstruction in Case #2. ( A–F ) Red: internal carotid artery (ICA), Yellow: trigeminal nerve, Purple: tumor, Black: skull base defect opening into the nasal cavity, Shaded area: skull base defect lined with the pterygoid muscle and not connecting into the nasal cavity, Green: temporoparietal galeal flap (TPGF). ( A ) Before tumor removal. ( B ) After tumor removal. ( C ) TPGF ( green arrowheads ). ( D ) TPGF was introduced into the nasal cavity through the petrous bone defect. ( E ) Tip of TPGF was inserted back into the cranial cavity through the sphenoid bone defect. ( F ) TPGF wrapped the petrous portion of ICA and the mandibular nerve and separated the cranial cavity from the nasal cavity. ( G–L ) Upper: endonasal endoscopic photos. Lower: black and white version of the upper picture. Red: internal carotid artery (ICA), Yellow: trigeminal nerve, Blue: piece of fascia lata, Green: TPGF, Pink: abdominal fat graft, White: nasoseptal flap. ( G ) The thinned dura around the internal auditory meatus was covered with a piece of the fascia lata. ( H ) TPGF was introduced into the nasal cavity through the petrous bone defect. ( I, J ) The two teams worked together to wrap TPGF around the internal carotid artery. ( K, L ) Infratemporal dead space was packed with the abdominal fat graft and separated from the nasal space using a nasoseptal flap.

Postoperative Clinical Course

No newly developed or worsening deficits were found, and the patient's postoperative course was uneventful. No tumor recurrence, wound complication including the TPGF donor site, or CBS was observed during the 4-year follow-up period ( Fig. 2I–M ).

Case 3

The patient was a 73-year-old man with skull base radiation necrosis and intracerebral abscess. Twelve years prior, he had undergone proton beam therapy for orbital adenoid cystic carcinoma. One year ago, he had a history of pus discharge from the orbit and nasal cavity and underwent enucleation of his right eye to prevent the spread of infection. For the following year, he received multiple drainage procedures at the ophthalmology outpatient department. He exhibited progressive disturbance of consciousness and was consequently transported to the emergency department of our hospital by ambulance. He had trismus due to the pterygoid muscle fibrosis after the proton bean therapy and nasotracheal intubation was performed. As the infection extended from the extracranial space to the intracerebral space ( Fig. 4A–D ), we planned a simultaneous transnasal and transcranial approach. The eTNA team performed the debridement of infected and necrotic tissue in the nasal cavity and paranasal sinus via a uninostril approach. The nasal mucosal flap could not be harvested because of mucosal necrosis and thinning. The transcranial approach team performed the epi- and subdural frontotemporal approach and removed necrotic tissues around the skull base and intracerebral abscess. After the removal of infected and necrotic tissue at the skull base, the cavernous portion of ICA was exposed to the nasal cavity through the sphenoid bone defect ( Fig. 5A ).

Fig. 4.

Contrast-enhanced T1-weighted axial magnetic resonance (MR) images of Case #3. ( A–D ) Preoperative MR images. ( E–H ) Postoperative MR images.

Fig. 5.

Intraoperative photographs and illustrations of skull base reconstruction in Case #3. Upper: The surgical field of the transcranial approach team, Middle: the surgical field of the transnasal approach team, Lower, illustration depicting skull base reconstruction. ( A ) After the removal of infected and necrotic tissue at the skull base, the cavernous portion of internal carotid artery (ICA) ( black arrowheads in photos and red line in illustration ) was exposed to the nasal cavity through the sphenoid bone defect ( area surrounded by blue dotted line in photos and black area in illustration ) ( B ) Temporoparietal galeal flap ( green arrowheads in photos and green area in illustration ) was introduced into the extradural space of the middle cranial fossa to protect the naked ICA and to separate the cranial cavity from the nasal cavity.

Skull Base Reconstruction

A unilateral TPGF with adequate length and width was harvested, as described in case 2, and introduced into the extradural space of the middle cranial fossa to protect the naked ICA and to separate the cranial cavity from the nasal cavity ( Fig. 5B ).

Postoperative Clinical Course

No newly developed or worsening deficits were found. He received intravenous antibiotics therapy (cefepime hydrochloride, 2 g at a time, thrice daily, for 4 weeks). The patient gradually improved and was discharged 8 weeks after the surgery. No infection recurrence, wound complication including donor site of TPGF, or CBS was observed during the 30-month follow-up period ( Fig. 4E–H ).

Discussion

We present three cases involving the exposure of ICA at the skull base during simultaneous transnasal and transcranial surgery. Skull base defects resulting from this simultaneous combined surgery are complex, and their reconstruction is a challenging task. Case 1 was a recurrent chordoma, showing that CBS could occur after skull base surgery. Thus, TPGF was used to protect ICA exposed to the nasal cavity and to cover the complicated skull base defects in Case 2 and Case 3.

The major benefit of this simultaneous combined approach has been reported to be improvement of the tumor resection rate in a single stage. ^{5 6} Multidirectional tumor devascularization and mass reduction are particularly effective for highly vascular and fibrous tumors. In addition to tumor resection, we believe that it is beneficial to perform skull base reconstruction cooperatively from both the intracranial and extracranial directions. Recently, we reported the transsphenoidal transposition of TPGF, which augments endonasal skull base reconstruction when nasal mucosal flaps are inadequate or unavailable. ⁷ Some reports also described the effectiveness of transpterygoid or transmaxillary transposition of temporoparietal fascia flaps. ^{8 9 10 11} With the development of the eTNA-based protocols, it is expected that the opportunity to expose the ICA from the nasal cavity side will increase. ¹² As exposure of the ICA is a risk factor of CBS, neurosurgeons should pay attention to the protection of the exposed ICA. Wound breakdown and infection around the carotid artery were also reported to be risk factors for arterial rupture. ³ It is important to provide a vascularized separation between the ICA and nasal cavity.

In Case 1, we used a nasoseptal flap, the workhorse for most skull base reconstructions after eTNA, but could not prevent wound infection. Angiography revealed rupture of the pseudoaneurysm at the petrous ICA, consistent with typical CBS findings. ¹³ Case 1 was a case of recurrent tumor and had a history of radiotherapy, which was also reported to be the risk factor of CBS. ¹⁴ Therefore, Case 1 was judged to be a very high-risk case of CBS, and we had to be more careful in protecting the ICA. Based on the experience of Case 1, we believed that the nasoseptal flap may not be robust enough to protect the naked ICA against wound breakdown and infection in the patients at high risk of CBS.

Case 2 was judged to have a lower risk of CBS than Case 1. However, we used TPGF to protect the petrous ICA in Case 2, because the skull base defect was large, and the ICA exposure was extensive. TPGF is a pedicled scalp flap with well-established utility in transcranial surgery. ¹⁵ Since the galeal layer covers the entire head area, a desired size of TPGF can be elevated to cover any size of skull base defect. Its robust blood supply is derived from the superficial temporal artery. ¹⁶ Since it does not contain mucosa and epidermis, both sides of TPGF can be attached to the tissues for protection. Therefore, TPGF can be used in any layer of a multilayer reconstruction. ¹⁶ These properties of TPGF were considered suitable for the protection of the naked ICA and reconstruction of the complex skull base defect. Case 3 was patient irradiated with proton therapy and already had severe infection around ICA. He also had skull base osteoradionecrosis, which was reported to be a strong predisposing factor for CBS. ¹⁷ The successful postoperative course of Cases 2 and 3 demonstrated the robustness of TPGF to protect ICA against infection and to prevent CBS even in patients at high risk of CBS.

We reported that CBS can occur after neurosurgery and also reported the effectiveness of ICA protection using TPGF against CBS. CBS is a rare complication in patients with head and neck tumor, and there are few reports of CBS at the skull base. ¹⁷ With the development of transnasal skull base surgery, it is expected that the risk of encountering CBS at the skull base will increase in the future. This study was a report of only three cases with multiple perspectives: pathology, prior treatment, and treatment. Based on our experience, a nasoseptal flap alone may be insufficient to protect ICA. TPGF is therefore another available reconstruction option that may help prevent CBS. However, to date, the guidelines for choosing TPGF, based on the patient's condition, are still unclear. A disadvantage of skull base reconstruction using galeal flap is a delay in scalp healing, because the superficial cutaneous layer becomes thin. Ito et al reported that the most common complication is scalp necrosis after surgery, with a frequency of 5.9%. ¹⁵ It is desirable to be able to choose the skull base reconstruction method according to the CBS risk in each patient. Therefore, a large prospective study should be performed involving multiple medical centers to determine how to prevent CBS at the skull base in the future.