Ziya Akar

Endoscopic endonasal approach to the orbital apex and medial orbital wall: anatomic study and clinical applications.

Objective: The objective of this study was to recognize the endoscopic anatomy of the orbital apex and medial orbital wall to understand the pure endoscopic endonasal approaches to this region and their clinical applications. These basic information will facilitate our surgical procedures and decrease the rate of surgical complications. Material and Methods: Five fresh adult cadavers were studied bilaterally (N = 10). We used Karl Storz 0- and 30-degree 4-mm, 18-cm, and 30-cm rod-lens rigid endoscopes in our dissections. After cadaver specimen preparation, we approached each orbital apex and medial orbital wall through each nostril. After resection of medial orbital wall, an endoscopic intraorbital approach was performed. Results: The orbita could be exposed by using 0- and 30-degree endoscopes. We preferred to start the approach from the sphenoid sinus instead of transethmoidal approaches that are less familiar to the neurosurgeons. The posterior and anterior ethmoidal arteries are in close relation to the supralateral wall of ethmoid sinus, thus care must be taken not to injure these arteries during dissection. In this way, we can safely expose the whole medial wall of the orbita. Optic canal decompression can be safely done by bone resection starting from the optic nerve toward the optic canal. We continued bone resection from the posterior to the anterior of the medial orbital wall, thus we can perform medial orbitotomy. The intraorbital approach can be done medially by introducing the endoscope between the medial and inferior rectus muscles. Conclusions: Our anatomic study offered the facility to learn the endoscopic anatomy of the orbital apex and the medial wall of the orbita and understand the appropriate approaches (such as medial orbitotomy and optic canal decompression) to some pathologic lesions of this region. With skilled and experienced hands, it can superimpose many traditional orbital approaches with minimal invasiveness and less postoperative complications.

Middle fossa approach: microsurgical anatomy and surgical technique from the neurosurgical perspective

BACKGROUND The purpose of this study was to call attention to the subtemporal approach directed through the petrous apex to the IAM. We studied the microsurgical anatomy of the middle floor to delineate a reliable angle between the GSPN and the IAM to precisely localize and expose the IAM from above. A new technique for the elevation of middle fossa floor in an anterior-to-posterior direction has also been examined in cadaveric dissections and performed in surgery. METHODS The microsurgical anatomy of the middle fossa floor was studied in 10 adult cadaveric heads (20 sides) after meatal drilling on the middle fossa. Five latex-injected specimens were dissected in a stepwise manner to further define the microsurgical anatomy of the middle fossa approach. The middle fossa approach is illustrated in a patient for the decompression of the facial nerve to demonstrate the surgical technique and limitations of bone removal. RESULTS Elevation of middle fossa dura in an anterior-to-posterior direction leads to early identification of the GSPN, where the nerve passes under V3. The most reliable and easily appreciated angle to be used in localizing the IAM is between the IAM and the long axis of the GSPN, which is approximately 61 degrees . Beginning drilling the meatus medially at the petrous ridge is safer than beginning laterally, where the facial and vestibulocochlear nerves become more superficial. The cochlea anteromedially, vestibule posterolaterally, and superior semicircular canal posteriorly significantly limit the bone removal at the lateral part of the IAM. CONCLUSIONS The surgical technique for the middle fossa approach which includes an anterior-to-posterior elevation of middle fossa dura starting from the foramen ovale and uses the angle between the IAM and the long axis of the GSPN to localize the meatus from above may be an alternative to previously proposed surgical methods.

Extended endoscopic endonasal approach to the clival region.

Objective: The objective of this study was to recognize the endoscopic anatomy of the clival region of the skull base and its neurovascular relations, which will make us able to perform safer and minimal invasive endoscopic approaches to this region with lower rate of complications. Materials and Methods: Six fresh cadavers were studied (n = 5). We approached the clivus by performing binostril extended endoscopic endonasal approach. After locating the sphenoid sinus as a key point, the vomer was totally removed to expose the clival region located inferiorly to the sphenoid sinus. Mucosal incision is done vertically from the sphenoidal portion the clivus caudally to the inferior portion of nasal cavity just medially to vidian nerve. The mucosal flap is then dissected and retracted. The clivus was resected until the foramen magnum inferiorly. The lateral limit of the resection is the paraclival portion of the internal carotid artery (ICA).The dura and the meningohypophyseal artery is exposed. A vertical dural incision was done and retracted laterally to expose the intradural structures. The prepontine cistern and basilar artery were visualized. Results: The clivus was best localized by orienting the endoscope +15 degrees rostrally. After resecting the inferior wall of the sphenoid sinus and vomer and the overlying mucosa is retracted laterally until the vidian nerve, we obtained sufficient exposure of the clivus. The safe lateral limit of the surgical corridor was the vidian nerve. The clivus is resected until the foramen magnum inferiorly. The safe lateral limit of the resection in this step was the proximal cavernous and the distal petrosal portions of the ICA. This resection provided us with a wide exposure of the clival dura. The basilar plexus, the abducens nerve (sixth cranial nerve) passing through the basilar plexus, and the paraclival portion of the ICA can be injured when careful dissection is not performed. After dural incision, the prepontine cistern and the basilar artery were able to be exposed widely. Conclusion: Binostril extended endoscopic endonasal approach is an appropriate approach to the clival region of the skull base. With good knowledge of the endoscopic anatomic features of this region and its neurovascular relations, surgical procedures can be performed safely with more minimal invasiveness.

Extradural Balloon Obliteration of the Empty Sella Report of Three Cases (Intrasellar Balloon Obliteration)

Summary Empty sella syndrome is an anatomical and clinical entity composed of intrasellar reposition of the CSF and compression of the pituitary tissue, resulting in a clinical picture of headache, visual field defect, CSF rhinorrhea and some mild endocrinological disturbances. While some cases are primary with no appreciable aetiology, secondary cases are associated with prior operation or radiotherapy of the region. In our series, 3 patients with primary empty sella syndrome were treated by the current approach of extradural filling of the sellar cavity. This technique was first described by Guiot and widely accepted thereafter. We used a detachable silicon balloon filled with HEMA or liquid silicone for obliteration of the sellar cavity and obtained clinically satisfactory results without complications. Visual symptoms regressed and headache disappeared. But at long term follow-up all the balloons were found to be deflated. Despite the facility and efficacy of the technique we do not recommend it in the treatment of the empty sella because the filling of the sella is only transient and relapses may occur.

Chiasmatic low-grade glioma presenting with sacral intradural spinal metastasis

Abstract Leptomeningeal metastasis of low-grade gliomas in children has been documented in several series, both at the time of diagnosis and at relapse. The authors report a unique case of chiasmatic low-grade astrocytoma presenting with signs and symptoms related to the metastatic site rather than the primary site. In this respect, the possibility of appearance of symptoms and signs related to leptomeningeal dissemination preceding the signs and symptoms belonging to the primary site should be considered in this type of benign tumours.

The effects of systemic and intratumoral interleukin-12 treatment in C6 rat glioma model

Abstract Objective: Cytokine based immunotherapy has long been an exciting field for many investigators aiming to provide an effective alternative treatment modality for glioma management. Among these cytokines, interleukin-12 (IL-12) plays a crucial role in mediating inflammatory and antitumoral activity on the host defence. We have investigated the therapeutic role of systemic and local delivery of IL-12 in C6 rat glioma model and compared these two modalities. Methods: The donor C6 glioma cells were injected stereotactically to 32 Wistar rats and right frontal tumor formation was established in all subjects. The rats were evenly divided into four groups as intratumoral (i.t.) control group (Group IA), intraperitoneal (i.p.) control group (Group IB), i.t. treatment group (Group II) and i.p. treatment group (Group III). Magnetic resonance imaging were performed to 12 rats (three from each group) on the seventh post-inoculation day. Recombinant mouse IL-12 (rmIL-12) was administered via i.t. (0.1 μg 5 μl/day/rat) and i.p. (0.1 μg 20 μl/day/rat) routes to treatment groups between days 9 and 11 following tumor inoculation, for 3 consecutive days. The rats which were unresponsive to the external stimuli, unable to feed themselves or having severe neurological impairment were decapitated and the specimens were histopathologically examined. Results: The subjects of Group III (i.p.) showed a statistically significant prolongation in survival time (mean=39 days) when compared to the control group (mean=31.7 days) (p=0.035) and Group II (i.t.) (mean=24.5 days) (p=0.005). Histopathologic examination of Group III revealed markedly increased intratumoral and peritumoral lymphocyte infiltration compared with the other groups. Conclusion: This study demonstrated that systemic administration of IL-12 in C6 glioma model in rats prolongs the survival, probably by stimulating the cellular immunity leading to lymphocytic infiltration.

Neuronal nitric oxide synthase expression in glial tumors: correlation with malignancy and tumor proliferation

Abstract Introduction: Increased vascular permeability, vasodilatation, neovascularization and free radical injury in malignant tumors and adjacent normal tissues are believed to be mediated by nitric oxide (NO). High levels of neuronal nitric oxide synthase (nNOS) have been demonstrated in cultured and intracerebral cells. Our aim was to investigate nNOS expression in human glial tumors and to assess its correlation with the histologic grade and proliferative potential. Methods: Tissue specimens were obtained from 29 patients with supratentorial astrocytomas [15 glioblastoma multiforme (GBM), six anaplastic astrocytomas (AA) and eight low grade astrocytomas (LGA)] diagnosed and classified according to the current WHO classification of nervous system tumors. Immunohistochemical staining was performed in paraffin embedded specimens with polyclonal anti-nNOS antibody, and the levels of nNOS expression was evaluated as slight, moderate or dense on the basis of intensity and the extent of distribution of nNOS immunoreactivity. Proliferative potential was evaluated with immunostaining for Ki-67. Results: There was a significant positive correlation between the histologic grade and nNOS expression in terms of intensity and the extent of distribution of nNOS immunoreactivity (p<0.05). Greater values of Ki-67 indices were demonstrated in tumors with higher nNOS expression, indicating a positive correlation between proliferative potentials and expression of nNOS immunoreactivity. Conclusion: Our study suggests that nNOS expression is increased in glial tumors, which was significantly correlated with histologic grade and proliferative potential. NO overproduction due to overexpression of nNOS activity, seems to have significant correlation with malignancy in glial tumors, and may provide another target for anti-proliferative therapy in the future.

Idiopathic granulomatous hypophysitis: are there reliable, constant radiological and clinical diagnostic criterias?

Abstract Idiopathic granulomatous hypophysitis is a rare inflammatory disease of unknown aetiology; few cases are reported. We review the clinical presentation and radiological characteristics of these cases and our own experience with three new surgical cases, to determine diagnostic criteria. MRI of three cases revealed sellar lesions extending into the chiasmatic cistern. Their shape varied, from dumbbell to spherical and elliptical. All were isointense with the brain on T1-weighted images and gave heterogeneously high signal on T2-weighted images. Contrast enhancement was homogeneous in one case and heterogeneous in another. The pituitary stalk could not be identified. There was no dural enhancement. The sphenoid sinus mucosa was thickened in two cases and normal in one.

Endoscopic anatomy of the oculomotor nerve: defining the blind spot during endoscopic skull base surgery

ObjectiveThe objective of this study is to define the endoscopic anatomy of the oculomotor nerve (CN III) and its neurovascular relations in order to facilitate surgical procedures and avoid injury to this nerve during endoscopic endonasal approach to the skull base.Materials and methodsEndoscopic anatomy of the cavernous sinus was studied in seven fresh adult cadavers bilaterally and the basal cisterns in five fresh adult cadavers. Extended endoscopic endonasal suprasellar approach was performed to expose the oculomotor nerve in the interpeduncular cistern and the endoscopic endonasal transethmoidopterygoidosphenoidal approach to expose the oculomotor nerve within the cavernous sinus.ResultsThe extraorbital part of the oculomotor nerve can be divided into three segments in regard to the cisterns and venous spaces that are being transected: the interpeduncular segment, the cisternal segment, and the intercavernous segment. Of these segments, only the cisternal segment could not be exposed since this segment was located at the initial part of the roof of the cavernous sinus, anterolateral to the posterior clinoid, and posteroinferior to the anterior clinoid processes. Thus, cisternal segment of the oculomotor nerve was considered a blind spot during endoscopic approaches to the skull base.ConclusionWe defined the endoscopic anatomy of the CN III and the related neurovascular structures and proposed a new segmental classification of extraorbital oculomotor nerve. Awareness of the endoscopic anatomy and the new segmental classification of the CN III may prove helpful in avoiding the risk of nerve injury during endoscopic endonasal surgery for skull base pathologies.

Lateral sublabial endoscopic approach to foramen ovale: a novel endoscopic technique to access infratemporal fossa.

Objective: Our aim was to define a novel endoscopic approach to selectively access the foramen ovale through the lateral sublabial route. Methods: Lateral sublabial endoscopic approach to the foramen ovale was studied in 3 fresh cadavers. A 2.5-cm sublabial submucosal incision gained access to the foramen ovale through the corridor under the zygomatic process of maxilla and lateral to the pterygoid plate. To display the anatomic principles of the lateral sublabial endoscopic approach, the surgical anatomy of the endoscopic corridor and the neurovascular structures around the foramen ovale were studied and documented. Results: Lateral sublabial endoscopic approach provided access to the foramen ovale and related neurovascular structures at the posterolateral part of the sphenoid bone without any bone resection. The branches of the pterygoid segment of the maxillary artery superficial to the lower and upper heads of the pterygoid muscles were exposed initially through the endoscopic corridor under the zygoma and lateral to the pterygoid plate. The buccal nerve, passing in between the 2 heads of the lateral pterygoid muscle and the lingual and inferior alveolar branches of the V3 segment of the trigeminal nerve, emerging from under the cover of the lower head of the lateral pterygoid muscle were exposed deep to the branches of the maxillary artery. Following the inferior alveolar nerve backward proximally under the lower head of the pterygoid muscle exposes the foramen ovale. Conclusions: Lateral sublabial endoscopic approach, a minimally invasive route to the foramen ovale, requires no bone removal and provides adequate exposure to a hard-to-reach area in the infratemporal fossa. With the advantage of visualizing the distal segment of the maxillary artery and the segments of the mandibular nerve, early in the procedure, the approach can provide a controlled endoscopic manipulation for accessing this region.