The versatile frontal sinus approach to the floor of the anterior cranial fossa. Technical note

Neurosurgery for the rhinologist

PURPOSE OF REVIEW

The purpose of this review is to provide a comprehensive anatomical appraisal of the neurosurgical anatomy exposed through the endonasal and paranasal sinuses routes, focusing on the most common expanded endonasal approaches (EEAs) as well as recent advances in this surgical field.

RECENT FINDINGS

The EEAs are redefining the management of skull base pathology. Neurovascular structures previously considered a limitation, can be now approached through these surgical corridors. Advances in this field include the development of new surgical techniques and routes that allow better visualization and access to pathologies located in the ventral skull base. Understanding the surgical anatomy related to EEAs is essential not only for neurosurgeons but also for rhinologists.

SUMMARY

Knowledge of the surgical anatomy of the most common EEAs that utilize paranasal sinuses as a surgical corridor enables more effective management of complex skull base pathologies. Comprehensive anatomical knowledge of these corridors and the surrounding neurovascular structures is crucial to maximize benefits of EEAs and improve outcomes.

TRANS-FRONTAL SINUS APPROACH FOR OLFACTORY GROOVE MENINGIOMAS: A 19 YEAR EXPERIENCE

INTRODUCTION

Olfactory groove meningiomas (OGMs) account for 8-13 % of all intracranial meningiomas. The gold standard of treatment is generally surgery, however various approaches have been used and the literature is still uncertain about the superiority of one treatment over the others. The most debated techniques are traditional microscopic open approaches versus the endoscopic endonasal ones. The aim of this paper is to prove a valid surgical route that gathers the benefits of both endoscopic and transcranial routes.

METHODS

Fifty consecutive patients underwent trans-frontal sinus surgical removal of an OGM between January 2000 and January 2019 at the Neurosurgical Departments in Torino, Brescia and Legnano (Italy). The clinical features were collected in a database and compared with neuroimaging and outcomes. All patients were investigated with neuroimaging techniques. Clinical evaluations were performed 3-4 months and 1 year after surgery, together with neuroradiological follow-up.

RESULTS

All patients with OGM underwent Simpson grade I resection. The most common neurological symptom leading to neuroradiological evaluations were headaches (36 %), followed by behavioural changes (30 %), hyposmia/anosmia (12 %), visual impairments (6%) and focal deficits (6%). At 3-4 months follow-up 48 patients underwent a brain MRI (2 patients underwent a brain CT), and a complete resection was confirmed in 45 patients (94 %).

CONCLUSIONS

Despite different techniques and studies supported by good evidence, there is no consensus on the best surgical approach for OGMs. The data shown in this article suggests that the trans-frontal sinus approach is a valid alternative to an endoscopic approach and the classical transcranial routes, collecting benefits from both approaches.

Frontal Sinus Pneumatization Affects Height of the Lateral Lamella and Position of Anterior Ethmoidal Artery

Preoperative evaluation of the frontal sinus (FS) and associated anatomical structures may reduce the risk of intraoperative complications and facilitate the management of potential complications. In this study, the authors aimed to evaluate relationship between FS pneumatization and critical anatomical structures. Paranasal sinus computerized tomography scans of 350 sides of 175 patients were evaluated. The pneumatization pattern of the FS, FS dimensions (on the axial, coronal, and sagittal slices), anterior ethmoidal artery, and depth of the of olfactory fossa were evaluated for every patient on both sides. There were 111 (63.4%) male and 64 (36.6%) female patients. The authors found a statistically significant correlation between the depth of olfactory fossa and the anterior ethmoidal artery position (P <0.001). As the FS pneumatization increases, the likelihood of the anterior ethmoid artery to run separately from the skull base also increases. Also, there was a statistically significant difference among the types in terms of the depth of the olfactory fossa (Kruskal-Wallis P = 0.002). The depth of the olfactory fossa increases depending on the increase of FS pneumatization.Our study shows that the olfactory fossa depth (skull-base depth) increases as FS pneumatization increases. In light of this information, the evaluation of the preoperative sinus computerized tomography scans will help in performing safer endoscopic sinus surgeries.

Frontal Sinus Morphometry in Relation to Surgically Relevant Landmarks in the United States Population

BACKGROUND

Knowledge of frontal sinus morphometry is important in bifrontal, pterional, orbitozygomatic, and supraorbital craniotomies. Inadvertent frontal sinus violation can lead to infection, cerebrospinal fluid fistula, and mucocele formation. In particular, knowledge of anatomy in relation to surgically relevant landmarks can help surgeons perform these procedures more precisely and safely. We performed a descriptive radiographic analysis to better understand variations in frontal sinus anatomy.

METHODS

Using 3-dimensional reconstructive software, we analyzed 162 normal cranial computerized tomographic angiograms (from 80 men and 82 women). A line between the supraorbital notches (SONs) was used as a horizontal reference line (HRL). We recorded the maximum sinus height and width from the HRL and midline, respectively. In addition, sinus width was measured in relation to the SON at 0, 1, and 2 cm above the HRL.

RESULTS

The mean maximal sinus height from the HRL was 1.8 cm. The mean maximum sinus width was 2.6 cm (right and left) from midline and 0.46 cm (right) and 0.49 cm (left) from the SON. Less than 11% of sinuses were lateral to the SON at 2.0 cm above the HRL and <6% of sinuses were >1.5 cm lateral to the SON at 1.0 cm above the HRL.

CONCLUSIONS

Planned surgical corridors >1.5 cm lateral to the SON and/or >3.0 cm above the HRL are most likely to avoid the frontal sinus based on our radiographic measurements of normal sinus anatomy. Careful radiographic study and appropriate planning for more medial and/or inferior corridors is suggested.

Craniotomy for anterior cranial fossa meningiomas: historical overview

The surgical treatment of meningiomas located at the base of the anterior cranial fossa is often challenging, and the evolution of the surgical strategy to resect these tumors parallels the development of craniotomy, and neurosurgery in general, over the past century. Early successful operations to treat these tumors were pioneered by prominent figures such as Sir William Macewen and Francesco Durante. Following these early reports, Harvey Cushing made significant contributions, allowing a better understanding and treatment of meningiomas in general, but particularly those involving the anterior cranial base. Initially, large-sized unilateral or bilateral craniotomies were necessary to approach these deep-seated lesions. Technical advances such as the introduction of electrosurgery, the operating microscope, and refined microsurgical instruments allowed neurosurgeons to perform less invasive surgical procedures with better results. Today, a wide variety of surgical strategies, including endoscopic surgery and radiosurgery, are used to treat these tumors. In this review, the authors trace the evolution of craniotomy for anterior cranial fossa meningiomas.

A von Hippel-Lindau disease-associated microcystic adenoma of the ethmoid sinus: case report

BACKGROUND AND IMPORTANCE

We present a unique case of an anterior cranial base von Hippel-Lindau disease (VHL)-associated microcystic neoplasm. To determine the lesion's relationship with VHL and its appropriate management, we discuss its salient clinical, pathological, and molecular features.

CLINICAL PRESENTATION

A 36-year-old woman with VHL presented with a 3-month history of phantosmia. Serial magnetic resonance imaging studies revealed a lesion within the ethmoid and frontal sinus region that was first evident 18 months before symptom development and demonstrated progressive growth over the interval period. The lesion was resected via a transbasal approach. Histopathological and immunohistochemical analysis revealed a microcystic lesion composed of bland clear cells and underlying endothelial cells consistent with a VHL-associated microcystic neoplasm that are not known to metastasize. Molecular testing demonstrated loss of heterozygosity of the VHL locus, verifying the tumor as a VHL-related neoplasm.

CONCLUSION

Because primary VHL-associated microcystic tumors in the anterior cranial base have not been described previously, the natural history of these tumors remains unclear. Based on the benign features of these lesions, they can be managed conservatively with close observation and surgical intervention reserved for those that produce symptoms.

Craniofacial resection: decreased complication rate with a modified subcranial approach

The authors have successfully utilized a modified subcranial approach to the anterior skull base, based upon the procedure first described by Joram Raveh, as an alternative to standard craniofacial resection. The complication rate of this procedure in 31 consecutive cases (28 tumors, 2 congenital malformations, and 1 mucocele) has been 19.4% with no permanent complications, no deaths, no new neurological deficits, no brain injuries, no infections, and no seizures. Minor complications without permanent sequelae included two cases of tension pnenmocephalus, a subdural hygroma, two transient cerebrospinal fluid leaks, and a case of bacterial meningitis secondary to fecal contamination of a lumbar drain in a child. Average length of hospitalization was 7.1 days (range 2 to 16 days). The overall complication rate is considerably below the complication rate for other reported craniofacial procedures. We describe the technique we have used and the results. The subcranial approach as described herein provides wide exposure of the anterior cranial base without brain retraction, does not require prolonged operating times or hospitalization, and has a potentially lower complication rate than reported for other transfrontal transbasal approaches.

Trans-sinusal frontal approach for olfactory groove meningiomas

The authors report on their experience with the trans-sinusal frontal approach in removing olfactory groove meningiomas. Six tumors were operated on by the trans-sinusal frontal approach, using a bicoronal incision; two tumors developed on one side, and there were four bilateral olfactosellar tumors. Osteotomy of the anterior wall of the frontal sinus was performed with an oscillating saw without any burr hole. The posterior wall of the sinus was resected and the tumor was attacked through a real subfrontal route along the plane of the anterior skull base. Ethmoidal blood supply was controlled at the initial stages of the operation, allowing avascular tumor debulking. Olfactory nerves, invaded by the tumor, were removed along with the tumor. Tumor extensions toward the sella and the optic canals were removed without brain retraction, opening of the Sylvian fissure, or dissection of the carotid arteries. All patients made a good neurologic recovery; intellectual impairment disappeared within 1 month, and visual acuity normalized within 2 weeks. Olfactory nets were preserved on the contralateral side in unilateral tumors. The trans-sinusal frontal approach is technically easy and safe to achieve. Osteotomy and replacement of the anterior wall of the frontal sinus are rapidly performed. When the frontal sinus is small, imageguided surgery allows precise deliniation of its limits and the free bone flap, including the calvarial outer layer, tangentially cut from one supraorbital canal to the other. The cosmetic result is perfect, as the normal contour of the forehead is maintained without any scar or visible burr hole. The trans-sinusal frontal approach gives access to the orbital roofs and to the central anterior skull base from the crista galli to the tuberculum sellae and the anterior clinoid processes. The trans-sinusal frontal approach represents an alternative to conventional craniotomies for tumors developed in the central anterior skull base, especially for olfactory groove meningiomas, whatever their size.

Proposed classification for the transbasal approach and its modifications

The transbasal approach offers extradural exposure of the anterior midline skull base transcranially. It can be used to treat a variety of conditions, including trauma, craniofacial deformity, and tumors. This approach has been modified to enhance basal access. This article reviews the principle differences among modifications to the transbasal approach and introduces a new classification scheme. The rationale is to offer a uniform nomenclature to facilitate discussion of these approaches, their indications, and related issues.

Comparative analysis of extensions of transbasal approaches: effect on access to midline and paramedian structures

We sought to quantitate the effect of extensions of transbasal approaches (TBAs) on midline and paramedian targets of the cranial base. Eight silicone-injected cadaveric heads were dissected with extensions of TBA level I removal of the orbital bar. Objective measures were the comparisons of the accessibility of midline and paramedian targets with progressive dissections by level II detachment of the medial canthal ligaments and removal of the nasal bone and by level III removal of the lateral orbital walls with lateral orbital retraction. Mean areas of freedom increased for most targets with progressive bone removal. For midline targets, the most effective freedom increment was at the pituitary gland (level II: 28.8%, p = 0.05; level III: 107.1%, p < 0.001). For paramedian targets, the best freedom increment was for the foramen rotundum (level II: 56.4%; level III: 134.5%, all p < 0.001). Extensions of the TBA can increase the surgical corridor to midline and paramedian structures, especially for pituitary and maxillary regions. Level II exposure offers no clear benefit for most targets except the foramen rotundum. With level III exposure, all targets are effectively exposed compared with levels I and II.

Transfrontoethmoidal approach to medial intraconal lesions

Object The standard superior craniotomy approach through the orbital roof is obstructed by numerous muscles, nerves, and vessels. Accessing the medial intraconal space also involves considerable brain retraction. The authors present a modified approach through the frontal sinus that overcomes these limitations. Methods Seven fixed silicone-injected cadaveric specimens were dissected bilaterally. In addition to the superior orbital wall, the ethmoidal sinuses and medial orbital wall were removed. The anatomical relationships between the major neurovascular complexes in the medial intraconal space and the optic nerve were observed. Results Intraconally, working space was created both in a "superior window" between the superior oblique and levator palpebrae muscle and in a "medial window" between the superior oblique and medial rectus muscle. The superior window mainly created an ipsilateral trajectory to the deep target. The medial window, which created a contralateral trajectory, provided a more inferior view of the medial intraconal space. Removal of the medial orbital wall further widened the exposure obtained from the superior window. The combination of these working windows makes the medial surface of the optic nerve available for exploration from multiple angles. Most of the major neurovascular complexes of the posterior orbit can be retracted safely without impinging on the optic nerve. Conclusions This novel extradural transfrontoethmoidal approach affords a direct view to the medial posterior orbit without major conflicts with intraconal neurovascular structures and requires minimal brain manipulation. The approach appears to offer advantages for medially located intraconal lesions.

CT study on morphometry of frontal sinus

The aim of this study was to determine the prevalence and morphological characteristics of the frontal sinus in an adult population. This study was conducted retrospectively on paranasal CT scans in the axial and coronal planes of 300 cases (123 male and 177 female). The mean age was 40.74 +/- 13.34 (range 20-83). Measurements of the width, height and anteroposterior length for each sinus and total width were obtained from CT scans. Measurements were compared statistically with relation to side and sex. The cases were divided into subgroups according to age for each sex and each measurement parameter was also compared among the subgroups. All measurements tended to be larger on the left side and were significantly larger in males than females. There was a significant difference in the anteroposterior lengths of right and left sides in both males and females and height for males and width for females. In both sexes, the highest values of measurements were usually observed at the 31-40 age group and there was a tendency to decrease with aging. The larger diameters of the left frontal sinus imply that it may be more possibly violated during surgical interventions. Morphometric features differed significantly in the two sexes at different ages and comparison with previous studies presented great regional variability. The size of the frontal sinus was seen to be related to age and sex. The knowledge provided in the present study is useful for some surgical procedures and widens the anthropometric knowledge of humanity.

Skull Base Chordomas: Management and Results

Growth patterns of skull base chordomas are related to important neurovascular structures. Local invasiveness results in "clinically malignant" behavior. A high rate of transient neurological deficits occurs following radical surgery. At our institution, the principle of radical removal is not followed at any price. This study compared the results of our management with recent series. Eleven patients, five females and six males aged 24-65 years (mean 41 years), underwent removal of skull base chordoma with size one <3 cm, five 3-5 cm, and five >5 cm. Mostly, standard operative approaches were chosen. All patients underwent postoperative radiotherapy. Resection was subtotal/partial in seven patients and total in four with no mortality. Neurological deterioration occurred due to transient cranial nerve deficits in six patients. Temporary surgical morbidity (including cranial nerve deficits) was observed in seven patients. Median Karnofsky performance status score improved compared to preoperative (80), early postoperative (70), and latest assessment (90) (median 36 months). Five patients underwent reoperation due to tumor recurrence after 4-48 months (mean 24 months). Most patients undergoing removal of skull base chordomas suffer from transient neurological deficits which are mainly nonsignificant as the patients return to preoperative functional status. The apparently high rate of incomplete tumor resection (64%) reflects the infiltrative behavior and relationship with neurovascular structures. The operative strategy should not be excessively aggressive at any price, but rather take into account the options of radiotherapy and observation of residual tumor.

The radical transbasal approach for resection of anterior and midline skull base lesions

OBJECT

Craniofacial surgery can be performed to treat midline and anterior skull base lesions by creating a bicoronal scalp incision without the need for an additional transfacial procedure. Originally described as the transbasal approach, several modifications for further exposure of the skull base have been described. The authors present data on the application and outcomes of a modified transbasal approach. The radical transbasal approach consists of a bifrontal craniotomy and a frontoorbitonasal osteotomy.

METHODS

Between 1992 and 2002, 41 patients (28 male and 13 female patients with a mean age of 38.3 years [range 7-77 years]) underwent 44 radical transbasal procedures. Twenty-three malignant and 18 benign lesions involving the midline skull base were treated. These cases were reviewed retrospectively. Gross-total resection of 30 lesions was achieved. Seven lesions were resected subtotally and six partially; one lesion was debulked. Complications occurred in 26 (59.1%) of the 44 operations and mostly consisted of cerebrospinal fluid leakage. The surgery-related mortality rate was 6.8% (three patients). Based on their pre- and postoperative Karnofsky Performance Scale scores, 86.4% of patients improved or remained the same.

CONCLUSIONS

The radical transbasal approach increases the midline craniofacial corridor by allowing the globes to be safely retracted laterally. It also enhances exposure of the maxillary sinus from above. The morbidity and mortality rates associated with this procedure are high but consistent with the known rates for craniofacial surgery. This approach is best suited for the treatment of anterior skull base tumors that extend into the nasal cavity, orbit, ethmoid sinus, nasopharynx, and upper clivus. The approach may allow resection of tumors involving the maxillary sinus area without the need for an additional transfacial approach.

Quantification of the advantages of the extended frontal approach to skull base

This anatomic study evaluated the extent that a fronto-orbital osteotomy (FOO) added to a bilateral frontal craniotomy widened the exposure to the midline compartment of the anterior, middle, and posterior cranial fossae. The goal was to determine if osteotomy would significantly increase angles for two targets: the foramen magnum (FM) and anterior clinoid process (ACP). Stepwise dissections were performed on five cadaveric heads. A bilateral frontal craniotomy was made, followed by FOO. After the ethmoids were removed, the planum sphenoidale was drilled to enter the sphenoid sinus. Further drilling exposed the anterior clivus, which was drilled down to FM. Excellent exposure of the basilar artery, vertebral artery, and brain stem was achieved. With and without FOO, angles of exposure were measured for two targets: the ACP and FM. The angle of exposure after FOO increased markedly with an average gain of 76% for the ACP and of 80% for FM. Compared with a conventional bifrontal craniotomy, the addition of FOO increased the surgical exposure and minimized frontal lobe retraction for accessing lesions of the anterior, middle, and posterior cranial fossae.

Advances in surgical management of malignancies of the cranial base: the extended transbasal approach

The extended transbasal approach combines a bifrontal craniotomy with an orbital nasal and potentially a sphenoethmoidal osteotomy to provide excellent access to malignancies of the anterior, middle and posterior skull base. The approach enables the en bloc resection of tumors within the frontal lobes, orbits, paranasal sinuses and sphenoclival corridors without brain retraction and may obviate the need for transfacial access. We present our 7-year experience during which 29 patients underwent surgery with the extended transbasal exposure. In 25 patients the extended transbasal approach was used alone; in the remaining four it was combined with additional approaches. With exception of two patients, all lesions were removed en bloc. Reconstruction was accomplished with the use of pericranium and in some instances a temporalis muscle pedicle or a gracilis microvascular free flap. There were no mortalities associated with this approach. Seven patients experienced infections, four patients experienced cerebral spinal fluid (CSF) leakage, two patients who had received adjuvant radiation experienced scalp necrosis, three patients experienced pneumocephalus, and 29 patients experienced cranial neuropathies, the majority of which were loss of olfaction. The average follow-up for our patients was 34 months with a range of 2--62 months.

Osteotomy design and execution

Craniofacial osteotomies are an integral part of contemporary neurosurgery because of their ability to provide substantially more exposure to deepseated lesions with reduced brain retraction. A systematic approach to the performance of these osteotomies coupled with meticulous bone work capitalizes on their advantages without producing any significant cosmetic defects. As their indications are progressively more clearly defined and familiarity and facility are gained by the surgeons performing them, operative time and morbidity should decrease. Lowering operative time and morbidity with excellent esthetic results is likely to be increasingly important when considering operative versus nonoperative management, particularly as nonsurgical modalities continue to develop.

Superficial surgical landmarks for the frontal sinus

OBJECT

There is a lack of reports in the literature that contain descriptions of superficial anatomical landmarks for the identification of the internally located frontal sinus. Neurosurgeons must often enter the cranium through the frontal bone and knowledge of the frontal sinus is essential to minimize complications.

METHODS

Seventy adult cadaveric frontal sinuses were evaluated. Measurements included both the lateral and superior extent of the frontal sinus in reference to a midpupillary line, and the superior extent of the frontal sinus from the nasion. Frontal sinuses were found bilaterally in all specimens. The mean height of the frontal sinus superior to the nasion was 2.8 cm. In 71.4% and 74.3% of specimens the lateral extent of the frontal sinus was found to be medial to the left and right midpupillary line, respectively. Distances superior to a plane drawn through the supraorbital ridges at a midpupillary line included a mean of 2.5 mm for the left side and 1.8 mm for the right side.

CONCLUSIONS

Of 70 sinuses, none extended more than 5 mm lateral to a midpupillary line. At this same midpupillary line and at a plane drawn through the supraorbital ridges, the frontal sinus was never higher than 12 mm. Finally, in the midline the frontal sinus never reached more than 4 cm above the nasion. These measurements will assist surgeons who must manipulate the frontal bone.

Cranial base kyphosis and the surface morphology of the anterior cranial fossa

We investigated the relationship between the surface morphology of the anterior cranial fossa and cranial base kyphosis (sphenoid angle) in 52 cephalometric craniograms. Among them there were 25 female (mean age 54 +/- 15; range 31-82) and 27 male (mean age 43 +/- 18, range 19-85) skulls. The sphenoid angle and the altitudes of the highest elevation of the endofrontal eminence (cranial base over the orbital roof in the anterior cranial fossa) and the middle point of the sphenoid planum, measured according to the Frankfort horizontal, were analysed using classical cephalometric and morphometric analysis. Statistical analysis was performed by Pearson's product-moment correlation and simple linear regression. The sphenoid angle ranged from 97 degrees to 137 degrees (mean 118 +/- 9 degrees). The altitude ratio of the highest elevation of the endofrontal eminence and the middle point of the sphenoid planum ranged from 1.5 to 1.8 (mean 1.6 +/- 0.1). A significant correlation was found between this ratio and the sphenoid angle (r = -0.65; p < 0.001; coefficient of determination = 0.43). The elevation of the endofrontal eminence relative to the sphenoid planum was higher in skulls with increased cranial base kyphosis, whereas reduced sphenoid angle was associated with an increase in the elevations of the endofrontal eminence. Although the sphenoid angle has a significant effect on the morphology of the anterior cranial fossa, only 43% of the variance in altitude of the endofrontal eminence is likely to be explained by its relationship with the sphenoid angle.

Early outcome and complications of the extended subcranial approach to the anterior skull base

OBJECTIVES

To present the technique of the extended subcranial approach to the anterior skull base and to review the results in 55 patients who underwent the procedure.

STUDY DESIGN

Retrospective review of the records of 55 patients who underwent the extended subcranial approach to the anterior skull base between 1994 and 1998 for the treatment of various neoplasms originating in the nasal cavity, nasopharynx, paranasal sinuses, orbit, or meninges, as well as for the repair of complex craniofacial trauma and/or cerebrospinal fluid (CSF) leak. Preoperative patient evaluation and the surgical technique are also reviewed.

METHODS

Patient records were retrospectively reviewed and tabulated for age, sex, and indications for procedure, with special focus on early outcome and complications.

RESULTS

Twenty-six patients underwent oncologic resections, 22 patients had reduction of complex fronto-naso-orbital and skull base fractures, and seven patients had repair of CSF leak. Significant complications in the oncologic group consisted of one hematoma requiring needle aspiration and two cases of temporary nontension pneumocephalus. In the fracture group, one patient died because of extensive intracerebral damage and multiorgan failure, and one patient had nontension pneumocephalus coupled with CSF leakage and one patient had temporary nontension pneumocephalus. The most common late complication in all three groups was anosmia.

CONCLUSIONS

Based on their review, the authors conclude that the extended subcranial approach to the anterior skull base is a safe, versatile, and effective procedure for the surgical treatment of various pathological conditions involving the anterior skull base.

Surgical approach to midline skull base tumors with olfactory preservation

Through the frontal approach, a skull base tumor in the deep midline region is obscured by the cribriform plate. This paper demonstrates our experience of operating on seven patients with midline skull base tumors posterior to the cribriform plate using a technique of maintaining the olfactory-cribriform anatomy. Following a bifrontal craniotomy and an orbitonaso-glabellar osteotomy, a circumferential osteotomy of the cribriform plate and horizontal incision of the nasal mucosa permitted mobilization of the cribriform plate unit along with the frontal lobe, providing a wide exposure of the posterior midline area. Tumors were resected from the posterior nasopharynx, ethmoid sinus, sphenoid sinus, and upper portion of the clivus. The skull base defects were repaired with the bipedicled temporoparietal galeal flap. Two patients lost olfaction because of poor preservation of the nasal mucosa and intradural dissection of the olfactory bulb. Five patients showed complete recovery of olfaction in 8 weeks. None of the patients developed cerebrospinal fluid leakage, infection, or increased neurologic deficits. En bloc mobilization of the cribriform plate and the bipedicled temporoparietal galeal flap are very useful for the management of midline cranial base tumors posterior to the cribriform plate as long as the olfactory unit is not involved with tumors.

Juvenile active ossifying fibroma. Report of four cases

Juvenile active ossifying fibroma is a rare lesion seldom seen by neurosurgeons. It originates in the paranasal sinuses during childhood, grows slowly, and encroaches on adjacent orbital and cranial compartments. In the past 3 years, four patients with this lesion were seen (three men and one woman; mean age 28 years). The clinical presentations were different with each patient: sinusitis, meningitis, periorbital pain, and a unique case of a juvenile active ossifying fibroma presenting with high-grade internal carotid artery stenosis and ischemic symptoms. Three patients were treated by transfacial approaches: two with a transfrontal-nasal approach and one with a transfrontal-nasoorbital approach. Two open resections resulted in gross-total excision and no recurrence as of the 2-year follow-up review. In the third patient, the tumor-encased carotid artery was preserved at the expense of a complete resection; that patient underwent superficial temporal artery-middle cerebral artery bypass and remains without ischemic symptoms or tumor recurrence at 2 years. The fourth patient underwent three subtotal endoscopic resections and is also without symptomatic recurrence at 2 years. Three points must be made concerning these lesions. First, the clinical and radiographic characteristics of juvenile active ossifying fibroma may not be easily recognized by neurosurgeons, which could lead to misdiagnosis and mismanagement of these lesions. Second, this tumor can encase the carotid artery and cause severe stenosis or occlusion. Third, complete resection of the tumor is required to effect a cure, and transfacial approaches, which give wide exposure of the sinuses, appear to yield better, more radical resections than endoscopic procedures.

Anterior transcranial (craniofacial) resection of tumors of the paranasal sinuses: surgical technique and results

Transfacial approaches, traditionally used for malignant tumors of the paranasal sinuses, provide limited exposure when several sinuses are involved and are unsuitable for tumors that erode through the floor of the anterior cranial fossa. A transcranial approach may aid in the removal of such lesions. To better understand the risks and benefits of this surgical approach, we reviewed all patients (n = 76) who underwent a transcranial approach as part of the excision of paranasal sinus lesions between 1984 and 1993 at our institution. The spectrum of disease included adenocarcinoma (13 patients), squamous cell carcinoma and olfactory neuroblastoma (11 patients each), adenoid cystic carcinoma and poorly differentiated forms of carcinoma (6 patients each), melanoma (5 patients), and miscellaneous others (24 patients). Most patients had ethmoid sinus involvement; tumors were also commonly found in the cribriform plate, sphenoid sinus, and nasal fossa. In each patient, a bifrontal craniotomy was performed with extradural dissection to the floor of the anterior fossa and osteotomies for resection of involved elements. In 47 patients (62%), disease in the orbit, the anterior nasal cavity, or the soft tissues of the face required transfacial as well as transcranial resections. Bony defect in the anterior fossa floor was repaired with a pedicled pericranial flap. Patients with major complications included six patients with epipericranial and/or epidural hematomas requiring evacuation, three with transient cerebrospinal fluid leaks, two who developed bifrontal cerebral infarcts, and one who died soon after surgery. No meningitis was seen. To date, 26 patients (34%) have died; of those living (mean follow-up, 34 mo), 42 (84%) remain in full remission. The transcranial approach can achieve removal of erosive, invasive tumors from this area with predictable morbidity and may be considered whenever sinus tumors breach the anterior cranial base or extend beyond the reach of conventional transfacial approaches.

Preservation of olfaction in anterior craniofacial approaches

Through the combined efforts of neurosurgeons, head and neck surgeons, and craniofacial surgeons, the standard transbasal approach to the frontal fossa has been modified to include removal of the orbital roofs, nasion, and ethmoid sinuses. This approach has been combined further with facial disassembly procedures to provide extensive midline exposure to the midface and clival region. Extended frontal approaches, however, necessitate removal of the crista galli and sectioning of the olfactory rootlets with the associated risk of anosmia, cerebrospinal fluid (CSF) leak, and the need for complex reconstruction of the frontal floor. To avoid these problems, the authors have modified the technique of handling the cribriform plate to preserve the olfactory unit. Circumferential osteotomy cuts are made around the cribriform plate to allow an en bloc removal with its attachment to both the dura and underlying mucosa. Opening of the dura is avoided and the cribriform bone is used to reconstruct the floor. Four patients underwent this approach, for treatment of an angiofibroma in three and a fibrosarcoma in one. The mean follow-up period was 7 months. No patients developed a CSF leak, and within 8 weeks olfaction had returned in all patients. There was no other associated morbidity. These data suggest that this modification of the transbasilar approach can alleviate extensive reconstructive procedures and CSF leaks while preserving olfaction.

Modified supraorbital craniotomy: technical note

The authors present a surgical approach that incorporates the frontal sinus and extends a supraorbital craniotomy to include the lateral orbital rim and zygoma. The craniotomy provides wide exposure of the anterior fossa, orbit, ipsilateral middle fossa, and cavernous sinus. The procedure can be performed easily, and the bone flaps can be secured rapidly back into the anatomical position at the time of closure. This modified supraorbital craniotomy is ideal for large benign lesions originating along the sphenoid wing or orbit that expand into the anterior fossa.

The extended frontal approach to tumors of the anterior, middle, and posterior skull base

The extended frontal approach is a modification of the transbasal approach of Derome. The addition of a bilateral orbitofrontal or orbitofrontoethmoidal osteotomy improves the exposure of midline lesions of the anterior, middle, and posterior skull base, while minimizing the need for frontal lobe retraction. The authors present a 5-year experience with 49 patients operated on via the extended frontal approach. In seven patients, the extended frontal approach was used alone; in the remaining 42, it was combined with other skull base approaches. Highly malignant tumors were removed en bloc, whereas benign tumors and low-grade malignancies were removed either en bloc or piecemeal. Reconstruction was usually performed using fascia lata, a pericranial flap, and/or autologous fat. A temporalis muscle flap or a distant microvascular free flap was required for some patients. One patient died 1 month postoperatively due to superior mesenteric artery thrombosis. Three patients had postoperative infections, two had cerebrospinal fluid leaks requiring reoperation, and four had brain contusions or hematomas. All but two patients recovered to their preoperative functional level. After an average follow-up period of 26 months (range 6 to 56 months), 64% of patients with benign lesions, 64% of patients with low-grade malignancies, and 44% of patients with high-grade lesions were alive with no evidence of disease.