Primary Repair of Posteriorly Located Anterior Skull Base Dural Defects Using Nonpenetrating Titanium Clips in Cranial Trauma

Abstract

Objective  Primary repair of posteriorly located anterior skull base (ASB) dural defects following cranial trauma is made difficult by narrow operative corridors and adherent dura mater. Inadequate closure may result in continued cerebrospinal fluid (CSF) leak and infectious sequelae. Here, we report surgical outcomes following the use of nonpenetrating titanium microclips as an adjunctive repair technique in traumatic anterior skull base dural defects extending from the olfactory groove to the tuberculum sellae.

Methods  All trauma patients who underwent a bifrontal craniotomy from January 2013 to October 2019 were retrospectively reviewed. Patients with ASB defects located at posterior to the olfactory groove were analyzed. Patients with isolated frontal sinus fractures were excluded. All patients presented with CSF leak or radiographic signs of dural compromise. Patients were divided according to posterior extent of injury. Patient characteristics, imaging, surgical technique, and outcomes are reported.

Results  A total of 19 patients who underwent a bifrontal craniotomy for repair of posteriorly located ASB dural defects using nonpenetrating titanium microclips were included. Defects were divided by location: olfactory groove (10/19), planum sphenoidale (6/19), and tuberculum sellae (3/19). No patients demonstrated a postoperative CSF leak. No complications related to the microclip technique was observed. Clip artifact did not compromise postoperative imaging interpretation.

Conclusion  Primary repair of posteriorly located ASB dural defects is challenging due to narrow working angles and thin dura mater. Use of nonpenetrating titanium microclips for primary repair of posteriorly located dural defects is a reasonable adjunctive repair technique and was associated with no postoperative CSF leaks in this cohort.

Introduction

Severe head injury resulting in basilar skull fractures is associated with cerebrospinal fluid (CSF) leak in 22 to 30% of patients. ^{1 2} The majority of anterior skull base (ASB) fractures result from closed head injuries with penetrating injuries being less common. ³ Posttraumatic CSF leak is associated with a 10 to 25% risk of developing meningitis, resulting in a 10% mortality risk in modern series. ^{1 2} Surgical repair of ASB dural defects is associated with a significant and durable risk reduction for development of meningitis. ⁴ Among all anatomic locations of the anterior skull base, fractures of the cribriform/fovea ethmoidalis are most commonly associated with CSF rhinorrhea. ⁴

The treatment of ASB fractures resulting in CSF leak is varied and often individualized to the patient or to surgeon practice patterns. At our center, simple posterior table fractures or less extensive anterior skull base fractures resulting in CSF leak are most commonly repaired via an expanded endoscopic endonasal or a supraorbital approach. Our indications for open surgical repair include open cranial trauma with or without penetrating ASB injury, extensive boney defects, or comminuted fractures of the ASB, traumatic destruction of nasal sinuses precluding the use of vascularized nasoseptal flaps, and large CSF leaks refractory to more conservative measures. Treatment discussion among neurosurgeons and rhinologists is paramount to offering the most appropriate repair technique for these patients. All patients in this manuscript underwent surgical repair as part of a joint case involving neurosurgery and ENT following a multidisciplinary discussion.

Primary repair of more posteriorly located ASB fracture-associated dural defects is uniquely challenging due to the limited operative corridor. In addition, within the narrow operative corridor lies densely adherent yet thin dura that is difficult to suture utilizing standard techniques. In cases of multiple defects or comminuted fractures resulting in extensive dural lacerations, simply identifying all defect sites may be challenging in some patients. Traditional techniques of ASB dural repair include a multilayered approach comprised of various autologous or synthetic materials via open and/or combined surgical approaches. ^{5 6 7 8} Despite the use of open and/or endoscopic techniques, reoperation rates for persistent CSF leak range from 0 to 12.5% with perioperative development of meningitis in 1 to 12.7%. ⁹

AnastoClip (LeMaitre Vascular, Burlington, Massachusetts, United States) are nonpenetrating titanium microclips originally designed for vascular anastomoses. ¹⁰ Here, we describe a technique for primary repair of traumatic posteriorly located ASB dural defects using nonpenetrating titanium microclips. We present outcomes following the use of this technique as an adjunct to traditional methods of ASB repair performed via a bifrontal approach. We chose to specifically examine more posteriorly located defects along the ASB, as we feel these are among the most difficult to manage.

Materials and Methods

Patient Selection

We conducted a retrospective review of all patients who underwent a bifrontal craniotomy following cranial trauma from January 2013 to October 2019 at our institution. A total of 19 consecutive patients who suffered more posteriorly located ASB injuries (i.e., from the olfactory groove to the tuberculum sellae) were included for analysis. All patients underwent the microclip technique described below as part of a multilayered repair technique. Patients were chosen based on a prospectively collected database maintained by our department. All patients in this cohort suffered bilateral cribriform injuries with or without more posteriorly located skull base injuries. None of the patients included in our series received a trial of conservative management with lumbar drainage. Surgical management was deemed necessary due to the severity of facial and skull base injury. Determination of need for open repair was made as part of a joint discussion among the neurosurgeon and rhinologist and treatment was based on the extent of injury as determined by radiographic and physical examination findings including the presence of CSF rhinorrhea or brain herniation into the nasal cavity. Additional considerations for open repair included the need for open repair of skull and/or facial fractures as well as removing of foreign body. Clinical records, hospital charts, operative notes, and imaging studies were reviewed through the last available follow-up. This study was performed with approval from our institutional review board (IRB no.: 3199).

Surgical Technique

The clip applier used in the present series consists of an 8-cm rotatable hand piece with a curved tip allowing for enhanced visualization. Each hand piece contains 25 clips. We used the “extra-large” clips as the internal diameter measures 3 mm in all patients. Optimal spacing for clip placement is typically between 2 and 3 mm when feasible.

A standard bifrontal or extended bifrontal craniotomy was performed in all patients. This included harvesting of a bipedicled pericranial flap when able as part of our standard operative technique. Once the bifrontal bone flap was elevated, cranialization of the frontal sinuses was performed in all patients to allow retractorless exposure of the entirety of the ASB. Once this was completed, extradural dissection under microscopic visualization was performed. Fractured frontal sinus fragments were extracted with care and high speed drill was used to remove sinus mucosa down to the level of the nasal frontal duct.

Under microscopic visualization, the ASB dura was open as widely and posteriorly as required based on the size and location of the defects, extending as far posteriorly as the tuberculum sellae when necessary. For isolated or clustered defects, the durotomy was performed in such a way as to encompass the entirety of the dural defects. This was done primarily to simplify the repair technique. For additional or nonclustered dural defects, separate dural openings were performed in a similar fashion. Comminuted fracture fragments were removed under microscopic visualization.

Meticulous microsurgical technique was then used to elevate a circumferential margin of the durotomy to allow for mobilization without further lacerating the dura. Once the entirety of the dural and boney defects were identified, a free tissue synthetic dural graft was obtained and sized to match the durotomy(ies). Circumferential elevation of the durotomy margin with care not to extend the durotomy is critical to the use of this technique as it allows for apposition of the graft material to the dural cuff. Once the graft was sized, the nonpenetrating titanium microclip applicator was used to circumferentially repair the durotomy under microscopic visualization. Successful repair requires the presence of a dural cuff to which the graft may be secured. Following this primary repair, obliteration of the cranialized frontal sinuses was performed utilizing a high-speed drill with a diamond burr under microscopic visualization. The pericranial flap was then placed into the epidural space as an additional layer. Because the dura was freed from the olfactory groove at onset, the pericranial flap may then be tucked as far posteriorly as necessary as there is no midline dural impedance. Clips may also be used similarly to tacking sutures in this step to secure the position of the pericranial flap, minimizing the likelihood of postoperative flap migration. As the clips are nonpenetrating, this may be performed by “tacking” the pericranial flap directly to the dura mater. Depending on the extent of injury, a fascia lata graft may also be used to further bolster the repair. Similarly, nasal packing with or without free mucosal or vascularized pedicle flaps can be incorporated into the repair. Figs. 1 and 2 illustrate the use of this microclip technique intraoperatively. Further details on the microclip applicator are described in a prior publication. ¹¹ Patients without concern for active infectious process were treated with standard 24-hour postoperative coverage with a broad spectrum antibiotic such as cefazolin or clindamycin. Those patients with suspected or confirmed infection at the injury site or another body system were treated according to microbiology culture results. For more complicated clinical scenarios, infectious diseases were consulted for input regarding appropriate antibiotic selection and duration of treatment.

Fig. 1.

Sequential intraoperative photographs ( A, B ) illustrate the use of our novel dural closure technique following anterior skull base closure.

Fig. 2.

Intraoperative photographs demonstrating bifrontal resection cavity before ( A ) and after ( B ) dural repair with titanium microclips.

Anosmia

The surgical technique described above involves disconnection of the olfactory groove dura, which would result in anosmia in an otherwise healthy patient. The decision to perform this surgical technique was not taken lightly. Multidisciplinary discussions between the neurosurgical and craniofacial teams were held for each patient. Patients were chosen based on bilateral involvement of the cribriform or if no other feasible repair options were available. Counseling of the patient or family by the surgical team was performed prior the procedure.

Outcome Assessment

Patients underwent a full neurological examination by the attending neurosurgeon immediately after surgery and at follow-up. Immediate postoperative imaging was obtained in all patients. New or worsened neurologic deficits were documented as complications. Complications were deemed temporary if they had resolved by the 1-month postoperative visit. Inpatient and outpatient records were used to report new postoperative neurological deficit, persistent CSF leak, postoperative infection, and other surgically relevant complications. Complications are displayed in Table 1 . CSF leak was defined as a positive β-2 transferrin test, imaging findings consistent with CSF leak, or clinically appreciable rhinorrhea.

Table 1. Bifrontal craniotomy patient characteristics.

Subject	Age (y)	Gender	Mechanism of Injury	Arrival Glasgow coma scale	Posterior extent of defect	Time presentation to surgery (d)	Pre-op clinically evident CSF leak	Post-op CSF leak	Post-op complications	Length of stay (d) a	Time to follow-up (wk)	Disposition
1	21	M	Motorcycle	14	Olfactory groove	4	+	−	−	13	136	Rehab
2	16	F	ATV	14	Planum sphenoidale	4	+	−	Diabetes insipidus	18	121	Home
3	34	M	ATV	15	Planum sphenoidale	5	−	−	−	10	103	Home
4	25	M	Assault	15	Planum sphenoidale	5	−	−	Cranial osteomyelitis	7	105	Home
5	25	M	MVC	15	Tuberculum sellae	2	+	−	−	11	184	Rehab
6	44	F	Bicycle	15	Planum sphenoidale	4	−	−	−	7	155	Home
7	48	F	MVC	15	Planum Sphenoidale	3	−	−	−	6	174	Home
8	23	M	Assault	11	Olfactory groove	23	−	−	−	7	5	Rehab
9	57	F	MVC	6	Olfactory groove	19	+	−	−	6	LTF	LTACH
10	64	M	MVC	8	Olfactory groove	11	−	−	−	12	133	Home
11	24	M	Motorcycle	15	Olfactory groove	5	−	−	−	7	83	Home
12	22	F	GSW	11	Olfactory groove	21	+	−	−	10	41	Home
13	21	M	MVC	8	Planum sphenoidale	11	+	−	−	14	17	Rehab
14	52	M	Auto-Ped	15	Tuberculum sellae	2	+	−	−	22	LTF	Home
15	25	M	GSW	3	Olfactory groove	17	+	−	−	13	LTF	LTACH
16	40	M	ATV	8	Tuberculum sellae	9	+	−	−	21	10	Rehab
17	24	M	Motorcycle	15	Olfactory groove	6	−	−	−	8	6	Home
18	17	M	Auto-Ped	14	Olfactory groove	3	−	−	−	6	5	Home
19	27	M	MVC	15	Olfactory groove	9	−	−	−	3	29	Home

Abbreviations: ATV, all terrain vehicle; Auto-Ped, auto-pedestrian collision; CSF, cerebrospinal fluid; ED, emergency department; F, female; GSW, gunshot wound; LTACH, Long term acute care hospital; LTF, lost to follow-up; M, male; MVC, motor vehicle collision; Post-op, postoperative; Pre-op, preoperative.

^aLength of stay following initial operation.

Results

Patient Population

Nineteen patients underwent a bifrontal craniotomy with clip repair as an adjunctive surgical technique. Of the 19 patients, 14 (74%) were men and 5 (26%) were women. The median age at operation was 25 years. Mean Glasgow coma score at presentation was 12. The mean length of time between presentation and surgery was 9 days. All patients in this series suffered comminuted displaced ASB fractures. All patients had defects of the frontobasal dura and fractures were located at or posterior to the cribriform plate. Nine of 19 (47%) patients demonstrated clinically appreciable CSF leaks in the preoperative setting. The posterior extent of dural repair was to the olfactory groove in 10/19 patients, the planum sphenoidale in 6/19 patients, and the tuberculum sellae in 3/19 patients. Patient characteristics including mechanism of injury, defect site, and outcomes are displayed in Table 1 .

Postoperative Course

No complications related to microclip repair technique were observed. No patient developed a postoperative CSF leak or required perioperative CSF diversion. No patients required intraoperative use of a brain retractor. One patient with a penetrating injury developed a delayed postoperative infection requiring reoperation for wound breakdown. This patient developed scalp wound breakdown along the previous site of penetrating injury and was found to have cranial osteomyelitis of the bifrontal bone flap. Following reoperation with bone flap removal and wound repair, the patient eventually underwent cranioplasty with a custom cranial implant. Another patient undergoing repair of an extensive defect extending to the tuberculum sellae developed central diabetes insipidus postoperatively which was transient in nature. Although this is more likely related to traumatic brain injury, we have included it here. No new or worsening neurological deficits were observed postoperatively.

Postoperative Imaging Interpretation

Microclips are readily identifiable on postoperative computed tomography/magnetic resonance imaging (CT/MRI). The clips have limited artifact and have not confounded imaging interpretation. ¹¹ Examples of preoperative and postoperative imaging for microclip dural repair are displayed in Figs. 3–6 .

Fig. 3.

Preoperative coronal 3D reconstructions ( A, B ), sagittal bone window CT ( C ), and coronal bone window CT ( D ) showing extensive craniofacial trauma. Postoperative sagittal ( E ) and coronal ( F ) bone window CT following bifrontal approach to anterior skull base reconstruction and dural repair with titanium microclips.

Fig. 4.

Preoperative coronal 3D reconstructions ( A ), sagittal bone window CT ( B ), and coronal bone window CT ( C ) showing extensive craniofacial trauma. Postoperative coronal reconstruction ( C ), sagittal bone window CT ( E ) and coronal bone window CT ( F ) following bifrontal approach to anterior skull base reconstruction and dural repair with titanium microclips.

Fig. 5.

Preoperative sagittal ( A ) and coronal ( B ) bone window CT showing anterior skull base defects). Postoperative sagittal ( C ) and coronal ( D ) bone window CT following dural repair with titanium microclips (indicated by white arrows).

Fig. 6.

Preoperative sagittal ( A ) and coronal ( B ) bone window CT showing anterior skull base defects. Postoperative sagittal ( C ) and axial ( D ) bone window CT following dural repair with titanium microclips (indicated by white arrows).

Discussion

Separation of the intracranial space from the nasal cavity while minimizing morbidity is the most critical step in surgical treatment of ASB defects. ^{7 12 13 14 15} Newer developments, such as expanded endoscopic endonasal repair techniques and the use of bipedicled pericranial flaps, have proven useful in achieving this goal. ^{8 16 17 18 19} In our opinion, there is little doubt in the effectiveness of endoscopic techniques for repair of well-defined defects. Trauma patients commonly present unique challenges compared with those presenting with spontaneous CSF rhinorrhea. This is especially true for penetrating injuries that have disrupted the nasal anatomy. However, the majority of trauma patients presenting with CSF rhinorrhea have sustained a closed head injury. ³ While some defects are clearly visualized, distorted and edematous anatomy with complex fracture patterns makes comprehensive identification of dural defects difficult from an endoscopic perspective without significant takedown of nasal mucosa and associated underlying bone. Even when performed, lateral fracture extension with dural involvement beyond the margin of the orbital lamina is a limitation of the endoscopic approach. In addition, commonly associated fracture patterns often include calvarial and/or facial fractures which may necessitate an open approach as well.

The bifrontal approach provides excellent access to the anterior skull base. However, this may be at the cost of increased surgical morbidity in some patients. Common indications include persistent CSF leak following conservative treatments for less complicated fractures. Endoscopic endonasal approaches to anterior skull base repair demonstrate decreased morbidity and mortality compared with open approaches. ²⁰ Therefore, at our institution, we prefer to approach CSF rhinorrhea from an endoscopic endonasal approach. However, for trauma patients with extensive skull base defects or in those requiring an open approach for different reasons, the bifrontal approach is utilized as it allows for both extensive exposure of the anterior skull base and harvesting of a vascularized pericranial flap. ^{19 21} Vascularized pedicled flaps appear to be more effective than free tissue grafts in repairing anterior skull base defects, especially in cases with high-flow CSF leak or defects larger than 1 cm. ¹⁹ Vascularized pedicled pericranial flaps are typically supplied by the supraorbital and supratrochlear arteries and are effective in reaching most sellar defects. ¹⁹ However, in some patients, the integrity of the pericranium may be disrupted or the vascular pedicle may be injured. However, the challenge remains in repairing complex dural lacerations in this region. We have previously reported the use of this technique in a diverse patient cohort consisting of both oncologic and trauma patients. ¹¹ In subgroup analysis, we realized that the leak rate in our trauma patients was zero. Here we have expanded our investigation in a retrospective analysis of prospectively collected trauma patients. Furthermore, we have chosen to limit our examination to those patients with what we feel to be the most difficult injuries to repair. The dura mater overlying the cribriform, planum, and tuberculum is classically thin and adherent. This makes even small fractures with limited displacement more likely to result in a dural laceration. In more complex fractures, the dura may be so disrupted that traditional suturing methods are not feasible.

The microclips used in this cohort are from the AnastoClip Vessel Closure System (LeMaitre Vascular, Burlington). These clips were originally designed for vascular anastomoses; however, their use has evolved over time. Their use is described in neurosurgical, urological, and pediatric surgery literature. ²² The clip applier is a single shafted instrument with an angled tip. The shaft of the instrument is rotatable may be manipulated singlehandedly. For the purposes of dural repair, we prefer the extra-large sized clips with an internal diameter of 3 mm prior to being deployed. The nonpenetrating nature of the clips is especially beneficial for the thin dura in this region and offers an advantage over suturing. Rather than penetrating the dura as a suture would, the clips simply appose the repair edges. Traditional suturing requires repeated dural manipulation to obtain visualization of both the extradural and intradural space. In contrast, the ability to safely fixate graft material with low risk of iatrogenic injury during the process offers an additional advantage over suturing in this anatomic region. Furthermore, microclip application may be more ergonomic than suturing in narrow operative fields. This allows for a robust attachment of graft material without repeated dural penetration or suture traction of the dural cuff. In our opinion, this attribute minimizes the risk of inadvertent injury to the cerebral cortex or further disruption of the dura. We also feel, it is a technically easier surgical technique.

Our initial concerns utilizing this technique consisted of clip closure strength. However, we have this concern to be unfounded in clinical practice. In fact, hydrostatic pressure studies in bovine spines have no difference in CSF leak rates among braided sutures, monofilament sutures, and microclips. ²³ Lastly, concerns were initially expressed that the titanium clip artifact may disturb CT or MRI interpretation in the postoperative setting. However, it has been demonstrated that this is not the case on multiple reports. ^{11 24} The size of the extra-large clips are comparable to commonly use cranial fixation screws which are not commonly found to distort postoperative imaging interpretation.

CSF leak is clearly associated with complex ASB fractures as they occur in up to one-third of cases. ^{1 2 25 26} Other contemporary studies have reported a significant rate of persistent postoperative CSF leak. ^{12 ,27} In one study of 43 patients who received pedicled tissue flaps for repair of ASB fractures, 12% patients developed CSF leaks. ¹² The authors also reported a 9% rate of local wound infection. ¹² Another trauma study reported persistent CSF leaks of the ASB in 13% of patients following attempted surgical repair. ²⁷ The above-mentioned studies also included patients with fractures of the posterior table of the frontal sinus which we feel are technically easier to repair for numerous reasons. Our patient population consisted only of defects located more posteriorly which we feel are more difficult to repair. That being said, no patients in our cohort developed a postoperative CSF leak. None required reoperation except one patient who suffered a penetrating cranial injury, developing delayed osteomyelitis of the frontal bone flap which presented as scalp erosion through the penetrating injury site.

While achieving a watertight closure in always the goal, this is not feasible in all situations. The technique described above is not meant to replace standard techniques with a long track record of efficacy. Rather, this is meant to serve as an additional adjunctive repair technique. We chose to focus on trauma patients with what we consider difficult to repair dural injuries to highlight the usefulness of this technique. If nothing else, the technique may serve as a means to prevent graft migration. We would also like to emphasize that this technique is not necessary in the majority of patients who develop a cerebrospinal fluid leak following trauma. Limiting the scope of this patient population to those who suffered a minimum of bilateral cribriform injuries with several patients harboring defects extending posteriorly beyond the cribriform was chosen as these patients represent a different group than those with isolated injuries. Furthermore, we chose to employ this technique in this group as they were felt to be high risk for persistent leak requiring an open approach as determined by a multidisciplinary surgical team consisting of both neurosurgery and otorhinolaryngology. When possible, we feel that an endonasal approach should initially be considered. This technique should be reserved for those with extensive injuries not suitable for endonasal repair.

Conclusion

Primary repair of posteriorly located anterior skull base dural defects is challenging due to narrow working angles and relatively thin dura mater in this region. Use of nonpenetrating titanium microclips for primary repair of posteriorly located dural defects is a reasonable adjunctive repair technique and was associated with no postoperative cerebrospinal fluid leaks in this cohort.