Mehmet Faik Ozveren

Meningovenous Structures of the Petroclival Region: Clinical Importance for Surgery and Intravascular Surgery

OBJECTIVE The goals of this investigation were to perform a detailed analysis of petroclival microanatomic features, to investigate the course of the abducens nerve in the petroclival region, and to identify potential causes of injury to neurovascular structures when anterior transpetrosal or transvenous endovascular approaches are used to treat pathological lesions in the petroclival region. METHODS Petroclival microanatomic features were studied bilaterally in seven cadaveric head specimens, which were injected with colored silicone before microdissection. Another cadaveric head was used for histological section analyses. RESULTS A lateral or medial location of the abducens nerve dural entrance porus, relative to the midline, was correlated with the course and angulation of the abducens nerve in the petroclival region. The angulation of the abducens nerve was greater and the nerve was closer to the petrous ridge in the lateral type, compared with the medial type. The abducens nerve exhibited three changes in direction, which represented the angulations in the petroclival region, at the dural entrance porus, the petrous apex, and the lateral wall of the internal carotid artery. The abducens nerve was covered by the dural sleeve and the arachnoid membrane, which became attenuated between the second and third angulation points. The abducens nerve was anastomosed with the sympathetic plexus and fixed by connective tissue extensions to the lateral wall of the internal carotid artery and the medial wall of Meckel’s cave at the third angulation point. There were two types of trabeculations inside the sinuses around the petroclival region (tough and delicate). CONCLUSION The petroclival part of the abducens nerve was protected in a dural sleeve accompanied by the arachnoid membrane. Therefore, the risk of abducens nerve injury during petrous apex resection via the anterior transpetrosal approach, with the use of the transvenous route through the inferior petrosal sinus to the cavernous sinus, should be lower than expected. The presence of two anatomic variations in the course of the abducens nerve, in addition to findings regarding nerve angulation and tethering points, may explain the relationships between adjacent structures and the susceptibility to nerve injury with either surgical or endovascular approaches. Venous anatomic variations may account for previously reported cases of subarachnoid hemorrhage with the endovascular approach.

Review of complications due to foramen ovale puncture

We aim to evaluate the mechanisms responsible for complications during trigeminal rhizotomy via foramen ovale puncture. Ten dry skulls and 10 skull-base specimens were investigated in the present study. In cadaveric skull-base specimens, the anatomical relationships between the foramen ovale, mandibular nerve and Gasserian ganglion and the surrounding neurovascular structures were investigated intradurally. The distance between the foramen ovale and Gasserian ganglion was measured as 6 mm. The abducent nerve, adjacent to the anterior tail of the petrolingual ligament, was observed passing along the lateral wall of the cavernous sinus. Advancement of the catheter more than 10 mm from the foramen ovale is likely to damage the internal carotid artery and the abducent nerve at the medial side of the petrolingual ligament. Thermocoagulation of the lateral wall of the cavernous sinus may damage the cranial nerves by heat, giving rise to pareses.

Microanatomical architecture of dorello's canal and its clinical implications

OBJECTIVE We investigated the membranous architecture of the abducens nerve at the petroclival region and describe the characteristics of this area in cadaveric specimen and two children with hydrocephalus and sixth nerve palsy using magnetic resonance imaging (MRI). MATERIALS AND METHODS Five adult cadaver heads were used to investigate the petroclival part of the abducens nerve. The heads were injected with colored latex for microsurgical dissection, and the length of the dural sleeve of the abducens nerve and its width at the apex were measured. In one cadaver head, the area between the petroclival entrance porus of the abducens nerve and the cavernous sinus was histologically studied under light microscopy. In two patients with hydrocephalus and abducens nerve palsy, the petroclival area was screened by using the MRI fat suppression technique. RESULTS In the cadavers, the arachnoid membrane on the clivus extended within the dural sleeve as far as the petrous apex, as an extension of the subarachnoid space. The average length of the dural sleeve was 9.5 mm and the average width was 1.5 mm at the apex, where the nerve entered the cavernous sinus. MRI scans showed that the cerebrospinal fluid distance of the petroclival region was 5 mm in the first patient and 7 mm in the second. CONCLUSION The subarachnoid space inside the dural sleeve of the abducens nerve can be defined by using thin-slice MRI scans. Enlargement of the dural sleeve at the petroclival region may coexist with the abducens nerve palsy. It has been documented in this study that the arachnoid membrane forms a membraneous barrier between the subarachnoid and subdural spaces within Dorellos canal.

Abducens schwannoma inside the cavernous sinus proper: case report

BACKGROUNDnOnly 2 cases of abducens nerve schwannoma solely inside the cavernous sinus have been reported. In both cases, abducens nerve palsy remained after operation. We report the first case of abducens nerve schwannoma inside the cavernous sinus proper with postoperative recovery from abducens nerve palsy.nnnCASE DESCRIPTIONnThe patient was a 47-year-old female who developed left abducens and trigeminal nerve palsies. Neuroradiological examination revealed left intra-cavernous sinus tumor. Total removal of the tumor was performed. The location of the tumor was confirmed intraoperatively inside the cavernous sinus itself, with no relation to the trigeminal nerve. Further, the relation of the tumor to one particular nerve fiber within the abducens nerve bundle was confirmed inside the cavernous sinus. After surgery, the patient had transient abducens nerve palsy. It had totally disappeared by 6 months.nnnCONCLUSIONnWhen the tumor origin is just within the spacious cavernous sinus rather than more posterior in the narrow dural tunnel of Dorellos canal, successful preservation of the nerve function is possible postoperatively through a thorough knowledge of the membranous anatomy and careful preoperative study of the radiographic findings.

Delayed Trigeminocardiac Reflex Induced by an Intraorbital Foreign Body

Objective: To emphasize the importance of the mechanism and surgical approach to trigeminocardiac reflex (TCR) developing 48 h after orbital trauma due to a foreign body. Case Report: After gunshot injury of a 17-year-old male patient, computerized tomography evaluation revealed a right globe perforation and an intraorbital metallic foreign body in the right orbita adjacent to the lateral wall. The ocular perforation was repaired, but the foreign body was not removed. Constant bradycardia (45/min) developed 48 h after the operation. Since there were no cardiological findings, a temporary cardiac pacemaker was inserted and on the 6th postoperative day, the foreign body was removed through orbitolateral approach. After the removal of the foreign body, bradycardia completely recovered. Conclusion: In the presence of an intraorbital foreign body accompanied by globe perforation, TCR may develop 48 h after the trauma and insertion of a temporary pacemaker may be required to control the cardiac rhythm. In this paper, the delayed TCR complication presented an indication for the removal of the intraorbital foreign body.

The significance of the percentage of the defect size in spina bifida cystica in determination of the surgical technique.

AbstractnAim. Our aim was to classify meningoceles and meningomyeloceles in terms of defect area as a percentage of the thoracolumbar region to make it possible to select the surgical technique accordingly.nMaterials and methods. Thirty-two cases were included in the study program. Any defect smaller than 8% of the thoracolumbar region was primarily sutured and classed as grade 1.nResults. The defects that it was not possible to handle with primary suture because of the broad base and thereby closed with muscle–skin flaps were those occupying more than 8% of the thoracolumbar region and these were classed as grade 2. It was not possible to perform primary repair of any defect occupying more than 8% of the thoracolumbar area.nConclusion. The use of combined latissimus dorsi+gluteus maximus muscle–skin flaps was found to be safe in broad-based meningomyelocele defects, as they provide wider closures and permanent bolstering of the meningomyelocele defect, thus protecting the region against multiple trauma.

Cellular schwannoma of the greater superficial petrosal nerve presenting with abducens nerve palsy and xerophthalmia: case report.

OBJECTIVECellular schwannomas (CS) are rare in the cranial space. This report is the first of a patient with a greater superficial petrosal nerve CS presenting with abducens nerve palsy and xerophthalmia. CLINICAL PRESENTATIONA 16-year-old female patient presented with a 1-month history of diplopia. Neurological examination was normal except for the presence of right abducens nerve palsy. Schirmers test revealed decreased tear secretion in the right eye. Computed tomography and magnetic resonance imaging showed a mass in the right petrous apex. It was thought that the schwannoma in our patient originated from the greater superficial petrosal nerve, based on the location of the tumor in addition to the absence of partial Horners syndrome and a persistent decrease in tear secretion. INTERVENTION: The tumor was exposed with the use of a right subtemporal extradural approach and removed entirely. Pathological evaluation of the tumor revealed a CS. CONCLUSIONThe abducens nerve palsy improved completely in the follow-up period, but the decreased tear secretion did not resolve. CS is one of the subtypes of ordinary schwannomas and exhibits malignant features on microscopic examination, although it has a good clinical prognosis. No adjuvant treatment was applied because of the tumors benign character. The greater superficial petrosal nerve schwannoma should be considered in the differential diagnosis of the abducens nerve palsy and petrous apex mass.

Relationship Between Clinical Grade, Cerebral Blood Flow, and Electroencephalographic Alterations in Patients With Chronic Subdural Hemorrhage

ObjectiveTo analyze the correlation between clinical grading, brain blood flow, and electroencephalographic (EEG) changes in cases with chronic subdural hemorrhage (CSH). Material and MethodsThirteen patients with unilateral CSH, who were treated in our clinic were selected. The preoperative peak systolic flow rate, mean flow rate, end-diastolic flow rate, resistive index, and pulsatility index (PI) of both middle cerebral arteries (MCA) were recorded in all participants by transcranial Doppler. In addition, EEGs of all cases were evaluated. ResultsClassification of the hemorrhage as hypodense, isodense, and mixed type by computed tomography scanning was not correlated with the brain blood flow. In cases with clinical grade 2 hemorrhage, the flow rate of the ipsilateral MCA was decreased. On the other hand, the ipsilateral PI had increased in the same cases. The thickness of the hemorrhage was below 2u2009cm in all patients with a normal EEG. The PI value was high in patients with an abnormal EEG. ConclusionsThe blood flow rate of the MCA on the hemorrhagic side in cases with CSH is lower than that of the contralateral artery. However, this decrease does not have a linear correlation with the thickness of the hemorrhage or clinical grade. The increase in the ipsilateral PI is more significant than the decrease in the MCA blood flow rate in determining the clinical grade. This suggests that hemorrhage should have an impact that is adequate to activate compensatory mechanisms to observe changes in the EEG recordings.

Total L1 Vertebrectomy With T12-to-L2 Fusion in a Case of Burst Fracture

Objective:To present a novel technique aiming at fusion of the upper and lower vertebrae by removal of the anterior and posterior elements of a lumbar vertebra. Methods:A 26-year-old male patient presented with a posttraumatic L1 vertebra fracture and total paraplegia. Three weeks after corpectomy plus otogenic bone grafting plus instrumentation by an anterolateral approach, the patient, who had 3-column injury, developed a treatment-resistant deep wound infection. In the fourth week of antibiotic treatment after the onset of the infection, there was no improvement, and the vertebral stabilization provided by the instrumentation was disrupted. Thus, the fixators and autograft were removed, the L1 posterior elements were totally excised, and compressive posterior instrumentation was performed. Results:Fusion stabilization was achieved in the patient with treatment-resistant postoperative deep wound infection after anterior instrumentation through a total vertebrectomy plus a posterior instrumentation technique.

Significance of Feeder-based Evaluation of Brain Arteriovenous Malformations

Background:Functional evaluation of the feeder vessels of the arteriovenous malformations (AVMs) through the super-selective cerebral angiography route reveals which tolerable and intolerable arteries are safe for embolization. Propofol is another agent, in place of amobarbital, for the provocative test. The purpose of this study was to show our experience using high doses of propofol as a reliable and effective drug in the neuroendovascular treatment of AVMs. Patients and Methods:A series of 23 patients with 54 feeder arteries were embolized using neuroendovascular techniques. All patients were embolized under general anesthesia. Preembolization neurological examination was performed following a 20 mg dose of propofol injected through an intra-arterial route following microcatheter placement, in or near the AVM nidus. Results:Among these 54 arteries, 4 vessels developed temporary neurological deficits after propofol injection, which were not occluded. None of the feeder arteries passing the provocative test showed a false tolerable result after embolization. Conclusions:Embolization of cerebral AVMs by means of a feeder provocative test with high-dose propofol has yielded reliable results in this series, in which the feeder artery tolerability allows an increase in the safety of the procedure and reduces complications.