Technical nuances of the minimally invasive extreme lateral approach to treat thoracolumbar burst fractures.

PURPOSE: Contemporary minimally invasive techniques have evolved to enable direct access to the anterior spinal column via the extreme lateral approach. We have employed this access approach to treat selected burst fractures. We report our technique. Thoracolumbar burst fractures that require surgical intervention have traditionally been managed with anterior, posterior, or combined approaches. METHODS: We have applied the minimally invasive extreme lateral approach to perform vertebral corpectomy, cage placement, and lateral instrumentation to treat burst fractures. Indications for surgery were incomplete spinal cord injury with persistent neural element compression due to ventral fracture fragments in the canal. We present the technical nuances of this surgical approach for the treatment of thoracolumbar burst fractures with two case illustrations. RESULTS: There were no peri- or intra-operative complications. Both patients in our series remained neurologically intact at their last follow-up (11 and 29 months, respectively), and maintained their correction of kyphosis. CONCLUSION: The minimally invasive extreme lateral approach is an effective treatment option for the management of thoracolumbar burst fractures.

The transclival endoscopic endonasal approach (EEA) for prepontine neuroenteric cysts: report of two cases.

INTRODUCTION: The transclival endoscopic endonasal approach was used to completely remove a prepontine neuroenteric cyst in two different patients. CASE REPORTS: Full clinical improvement without postoperative complication was achieved in both cases. The postoperative hospital stay was limited to 2 and 3 days. DISCUSSION: In comparison to posterolateral skull base approaches, the transclival endoscopic endonasal approach allows direct access to the prepontine cistern without unnecessary manipulation of neurovascular structures at the cerebellopontine angle. In contrast to transoral surgery, patients may have decreased risk of infection and can be fed orally immediately without the risks of palatal and oropharyngeal dehiscence. CONCLUSION: Neuronavigation technology, strict adherence to microsurgical principles, and significant endoneurosurgical experience are strongly recommended when approaching these challenging lesions.

Stereotactic radiosurgery for convexity meningiomas.

OBJECT: Meningiomas of the cerebral convexity are often surgically curable because both the mass and involved dura mater can be removed. Stereotactic radiosurgery has become an important primary or adjuvant treatment for patients with intracranial meningiomas. The authors evaluated clinical and imaging outcomes in patients with convexity meningiomas after radiosurgery. METHODS: The patient cohort consisted of 125 patients with convexity meningiomas managed using radiosurgery at some point during an 18-year period. The patient series included 76 women, 55 patients who had undergone prior resection, and 6 patients with neurofibromatosis Type 2. Tumors were located in frontal (80 patients), parietal (24 patients), temporal (12 patients), and occipital (9 patients) areas. The WHO tumor grades in patients with prior resections were Grade I in 34 patients, Grade II in 15 patients, and Grade III in 6 patients. Seventy patients underwent primary radiosurgery and therefore had no prior histological tumor diagnosis. The mean tumor volume was 7.6 ml. Radiosurgery was performed using the Leksell Gamma Knife with a mean tumor margin dose of 14.2 Gy. RESULTS: Serial imaging was evaluated in 115 patients (92%). After primary radiosurgery, the tumor control rate was 92%. After adjuvant radiosurgery, the control rate was 97% for Grade I tumors. The actuarial tumor control rates at 3 and 5 years for the entire series were 86.1+/-3.8% and 71.6+/-8.6%, respectively. For patients with benign tumors (Grade I) and those without prior surgery, the actuarial tumor control rate was 95.3+/-2.3% and 85.8+/-9.3%, respectively. Delayed resection after radiosurgery was performed in 9 patients (7%) at an average of 35 months. No patient developed a subsequent radiation-induced tumor. The overall morbidity rate was 9.6%. Symptomatic peritumoral imaging changes compatible with edema or adverse radiation effects developed in 5%, at a mean of 8 months. CONCLUSIONS: Stereotactic radiosurgery provides satisfactory control rates either after resection or as an alternate to resection, particularly for histologically benign meningiomas. Its role is most valuable for patients whose tumors affect critical neurological regions and who are poor candidates for resection. Both temporary and permanent morbidity are related to brain location and tumor volume.

Contemporaneous Evaluation of Intraoperative Ulnar and Median Nerve Somatosensory Evoked Potentials for Patient Positioning: A Review of Four Cases.

Somatosensory evoked potentials (SSEPs) are a valuable tool for assessing changes in peripheral nerve pathways caused by patient positioning during spinal surgeries. These changes, when left undiagnosed, may lead to postoperative neurological sequelae. Why an upper extremity SSEP attenuates due to positioning is not necessarily clear and can be multifactorial, affecting the peripheral nerves or elements of the brachial plexus. A conduction block can occur at any point along the course of the nerve secondary to entrapment, compression, and ischemia. These mechanisms of injury may be caused by extreme body habitus, the length of the procedure, or the patient's metabolic underpinnings. The goal of neuromonitoring for positional injury is to predict and prevent both peripheral nerve and brachial plexus injuries. Using ulnar and median nerve SSEPs contemporaneously may lead to better identification of compromised structures when an SSEP change to one or both of the nerves occurs. The investigators provide four case reports where intraoperative SSEP assessment of contemporaneous ulnar and median nerves prevented postoperative upper extremity neural deficits.

Resolution of Chiari malformation after repair of a congenital thoracic meningocele: case report and literature review.

OBJECTIVE AND IMPORTANCE: Many theories have been proposed regarding potential causative factors for Chiari malformations. An unusual case is described in which regression of a congenital Chiari malformation was observed after repair of a thoracic meningocele without direct surgical intervention to decompress the craniocervical junction. This supports the importance of an in utero craniospinal pressure gradient as a potential cause for congenital, but reversible, cerebellar herniation. CLINICAL PRESENTATION: A newborn baby was observed to have a thoracic meningocele. Magnetic resonance imaging scan revealed a concomitant Chiari malformation. No neurological deficits were present at initial examination. INTERVENTION: The patient underwent surgical closure of the thoracic meningocele and untethering of the spinal cord at the site of the dural defect. A postoperative magnetic resonance imaging scan obtained 3 months after the operation revealed complete resolution of the cerebellar herniation. CONCLUSION: The resolution of the Chiari malformation in this child may have resulted from restoration of normal cerebrospinal fluid flow and elimination of the meningocele-related cerebrospinal fluid pressure gradient between the intracranial and intraspinal compartments.

Cerebral revascularization for difficult skull base tumors: a contemporary series of 18 patients.

OBJECTIVE: Cerebral revascularization has been used in treating difficult skull base tumors when the preservation of the involved native arteries is deemed challenging, and the patients are at risk of developing vascular complications. We aimed to evaluate a recent series of patients who needed high flow cerebral bypasses as part of the surgical treatment strategies for their difficult skull base tumors; to assess current indications and the results of such treatments. METHODS: A prospectively collected consecutive series of patients were studied. These patients received high flow cerebral bypasses in conjunction with surgical resections of the skull base tumors during a 9-year period. RESULTS: A total of 20 high flow bypasses on 18 patients were performed, as part of the treatment plan for skull base tumors. The mean age was 41 years. Four patients had preoperative transient ischemic attack symptoms, three of which had progressed to acute strokes preoperatively. Thirteen patients (72.2%) had gross total resection. There were no acute perioperative stroke or graft occlusions. The mean follow-up was 47 months (2-104 months). One patient developed asymptomatic graft stenosis 8 months after surgery, which was surgically corrected. Fifteen patients had achieved good clinical outcomes (modified Rankin scale, ≤ 2) at the latest follow-up; one patient died postoperatively and two died of their disease. CONCLUSIONS: High flow bypass for cerebral revascularization is a good surgical option for treating certain difficult skull base tumors. High rate of graft patency and low risk of perioperative stroke can be achieved in experienced hands with concurrent high rate of gross total resection of the tumor and good clinical outcome of the patients.

Endoscopic endonasal approach for nonvestibular schwannomas.

BACKGROUND: Nonvestibular schwannomas of the skull base often represent a challenge owing to their anatomic location. With improved techniques in endoscopic endonasal skull base surgery, resection of various ventral skull base tumors, including schwannomas, has become possible. OBJECTIVE: To assess the outcomes of using endoscopic endonasal approach (EEA) for nonvestibular schwannomas of the skull base. METHODS: Seventeen patients operated on for skull base schwannomas by EEA at the University of Pittsburgh Medical Center from 2003 to 2009 were reviewed. RESULTS: Three patients underwent combined approaches with retromastoid craniectomy (n = 2) and orbitopterional craniotomy (n = 1). Three patients underwent multistage EEA. The rest received a single EEA operation. Data on degree of resection were found for 15 patients. Gross total resection (n = 9) and near-total (>90%) resection (n = 3) were achieved in 12 patients (80%). There were no tumor recurrences or postoperative cerebrospinal fluid leaks. In 3 of 7 patients with preoperative sensory deficits of trigeminal nerve distribution, there were partial improvements. Patients with preoperative reduced vision (n = 1) and cranial nerve VI or III palsies (n = 3) also showed improvement. Five patients had new postoperative trigeminal nerve deficits: 2 had sensory deficits only, 1 had motor deficit only, and 2 had both motor and sensory deficits. Three of these patients had partial improvement, but 3 developed corneal neurotrophic keratopathy. CONCLUSION: An EEA provides adequate access for nonvestibular schwannomas invading the skull base, allowing a high degree of resection with a low rate of complications.

Extreme-lateral, minimally invasive, transpsoas approach for the treatment of far-lateral lumbar disc herniation.

The authors present 2 cases of far-lateral lumbar disc herniations treated surgically via an extreme-lateral transpsoas approach. The procedure was performed using the MaXcess minimally invasive retractor system to access and successfully remove the disc fragments without complication. To the authors' knowledge, these are the first reported cases of using a minimally invasive retroperitoneal approach for the treatment of far-lateral disc herniations.

High-definition fiber tracking guidance for intraparenchymal endoscopic port surgery.

The authors have applied high-definition fiber tracking (HDFT) to the resection of an intraparenchymal dermoid cyst by using a minimally invasive endoscopic port. The lesion was located within the mesial frontal lobe, septal area, hypothalamus, and suprasellar recess. Using high-dimensional (256 directions) diffusion imaging, more than 250,000 fiber tracts were imaged before and after surgery. Trajectory planning using HDFT in a computer model was used to facilitate cannulation of the cyst with the endoscopic port. Analysis of the proposed initial surgical route was overlaid onto the fiber tracts and was predicted to produce substantial disruption to prefrontal projection fibers (anterior limb of the internal capsule) and the cingulum. Adjustment of the cannulation entry point 1 cm medially was predicted to cross the corpus callosum instead of the anterior limb of the internal capsule or the cingulum. Following cyst resection performed using endoscopic port surgery, postoperative imaging demonstrated accurate cannulation of the lesion, with improved quantitative signal from both the anterior limb of the internal capsule and the cingulum. The observed fiber preservation from the cingulum and the anterior limb of the internal capsule, with minor injury to the corpus callosum, was in close agreement with preoperative trajectory modeling. Comparison of pre- and postoperative HDFT data facilitated quantification of the benefits and costs of the surgical trajectory. Future studies will help to determine whether HDFT combined with endoscopic port surgery facilitates anatomical and functional preservation in such challenging cases.

Endoscopic endonasal resection of Rathke cleft cysts: clinical outcomes and surgical nuances.

OBJECT: Rathke cleft cysts (RCCs) are benign lesions that can be diagnosed as an incidental finding associated with headaches, pituitary dysfunction, or vision deterioration. Typically, they occur in a sellar or suprasellar location. The aim of this study was to review the clinical presentation and outcomes associated with endoscopic endonasal resection of these lesions. METHODS: The authors retrospectively reviewed a series of 35 patients with a diagnosis of RCC after endoscopic endonasal resection at the University of Pittsburgh between January 1998 and July 2008. RESULTS: All 35 patients underwent a purely endoscopic endonasal approach (EEA). The average patient age was 34 years (range 12-67 years), and the average follow-up was 19 months (range 1-60 months). Clinical follow-up data were available for 32 patients, and radiographic follow-up data were accessible for 33 patients. All of the patients underwent complete removal of the cyst contents, and according to radiography studies 2 patients had a recurrence, neither of which required reoperation. The mean cyst volume was 1052.7 mm(3) (range 114-6044 mm(3)). Headache was a presenting symptom in 26 (81.2%) of 32 patients, with 25 (96.1%) of 26 having postoperative improvement in their headaches. Fifteen (57.7%) of the 26 patients had complete pain resolution, and 10 (38.5%) had a > 50% reduction in their pain scores. Six (18.8%) of 32 patients initially presented with pituitary dysfunction, although 2 (33.3%) had postoperative improvement. Three (9.4%) of 32 patients had temporary pituitary dysfunction postoperatively, although there was no permanent pituitary dysfunction. Neither were there any intraoperative complications, postoperative CSF leaks, or new neurological deficits. The average hospital stay was 1.8 days (range 1-5 days). CONCLUSIONS: The EEA is a safe and effective approach in the treatment of RCCs. None of the patients in this study experienced any worsening of their preoperative symptoms or pituitary function, and 96% of the patients who had presented with headache experienced complete or significant pain relief following treatment.

Avoiding injury to the abducens nerve during expanded endonasal endoscopic surgery: anatomic and clinical case studies.

BACKGROUND: Understanding the course of the most medially located parasellar cranial nerve, the abducens, becomes critical when performing an expanded endonasal approach. OBJECTIVE: We report an anatomoclinical study of the abducens nerve and describe relevant surgical nuances to avoid its injury. METHODS: Ten anatomic specimens were dissected using endoscopes attached to an high-definition camera. A series of anatomic measurements and relationships of the abducens nerve were noted. Illustrative clinical cases are described to translate those findings into practice. RESULTS: Cisternal, interdural, gulfar, and cavernous segments of the abducens were identified intracranially. The mean distance from the vertebrobasilar junction (VBJ) to the pontomedullary sulcus (PMS) was 4 mm; horizontal distance between both abducens nerves at the PMS was 10 mm, and between both abducens at the interdural segment was 18.5 mm. The upper limit of the lacerum segment of the internal carotid artery was at the same level of the dural entry point of the sixth cranial nerve posteriorly. The sellar floor at the sphenoid sinus marks the level of the gulfar segment in the craniocaudal axis. At the superior orbital fissure, the abducens nerve and V2 were at an average vertical distance of 11.5 mm. CONCLUSION: Anatomic landmarks to localize the abducens nerve intraoperatively, such as the VBJ for the transclival approach, the lacerum segment of the carotid, and the sellar floor for the medial petrous apex approach, and V2 for Meckel's cave approach, are reliable and complementary to the use of intraoperative electrophysiological monitoring.

"Far-medial" expanded endonasal approach to the inferior third of the clivus: the transcondylar and transjugular tubercle approaches.

OBJECTIVE: The endoscopic endonasal transclival approach is a valid alternative for treatment of lesions in the clivus. The major limitation of this approach is a significant lateral extension of the tumor. We aim to identify a safe corridor through the occipital condyle to provide more lateral exposure of the foramen magnum. METHODS: Sixteen parameters were measured in 25 adult skulls to analyze the exact extension of a safe corridor through the condyle. Endonasal endoscopic anatomic dissections were carried out in nine colored latex-injected heads. RESULTS: Drilling at the lateral inferior clival area exposed two compartments divided by the hypoglossal canal: the jugular tubercle (superior) and the condylar (inferior). Completion of a unilateral ventromedial condyle resection opens a 3.5 mm (transverse length) * 10 mm (vertical length) lateral surgical corridor, facilitating direct access to the vertebral artery at its dural entry point into the posterior fossa. The supracondylar groove is a reliable landmark for locating the hypoglossal canal in relation to the condyle. The hypoglossal canal is used as the posterior limit of the condyle removal to preserve more than half of the condylar mass. The transjugular tubercle approach is accomplished by drilling above the hypoglossal canal, and increases the vertical length of the lateral surgical corridor by 8 mm, allowing for visualization of the distal cisternal segment of the lower cranial nerves. CONCLUSION: The transcondylar and transjugular tubercle "far medial" expansions of the endoscopic endonasal approach to the inferior third of the clivus provide a unique surgical corridor to the ventrolateral surface of the ponto- and cervicomedullary junctions.

Gamma knife radiosurgery for facial schwannomas.

OBJECTIVE: Patients who have a schwannoma of the facial nerve (facial schwannoma, facial neuroma) can be managed with observation, surgical resection, stereotactic radiosurgery, or fractionated radiotherapy. Attempted complete resection is associated with facial weakness. The role of radiosurgery in these patients remains to be defined. METHODS: We reviewed the clinical and imaging outcomes in patients who underwent gamma knife radiosurgery for a facial schwannoma. RESULTS: Six patients had radiosurgery and were followed for a mean and median of 46.6 and 61.5 months, respectively (21-85 months). Three had a previous resection, and in 3 the diagnosis was made based on clinical and imaging criteria. All patients had facial nerve symptoms (5 had weakness and 1 had muscle twitching). House-Brackmann grades before radiosurgery were as follows: 1 (n = 1), 2 (n = 3), 3 (n = 1), and 6 (n = 1). The radiosurgery margin dose was 12 or 12.5 Gy. On later imaging, 3 tumors had regressed (with the longest follow-up duration) and 3 were unchanged. All patients had preservation of their preradiosurgery facial function. No other adverse effects were noted and all patients maintained their preradiosurgery level of hearing. CONCLUSION: Over a mean of almost 4 years of follow-up, radiosurgery was shown to be a safe and effective management for residual and newly diagnosed facial schwannomas.

Stereotactic radiosurgery for radiation-induced meningiomas.

OBJECTIVE: Radiation-induced meningiomas of the brain are typically managed with surgical resection. Stereotactic radiosurgery (SRS) has become an important primary or adjuvant management for patients with intracranial meningiomas, but the value of this approach for radiation-induced tumors is unclear. METHODS: This series consisted of 19 patients (mean age, 40 years) with 24 tumors. The patients met criteria for a radiation-induced meningioma and underwent gamma knife radiosurgery. Seven patients had undergone a previous resection. The World Health Organization tumor grades for those with prior histology were Grade I (n = 5) and Grade II (n = 2). The median tumor volume was 4.4 cm3. Radiosurgery was performed using a median margin dose of 13 Gy. RESULTS: Serial imaging was evaluated in all patients at a median follow-up of 44 months. The control rate was 75% after primary radiosurgery. Delayed resection after radiosurgery was performed in 5 patients (26%) at an average of 39 months. The median latency between radiation therapy for original disease and SRS for radiation-induced meningiomas was 29.7 years (range, 7.3-59.0 years). The overall survival after SRS was 94.1% and 80.7% at 3 and 5 years, respectively. No patient developed a subsequent radiation-induced tumor. The overall morbidity rate was 5.3% (1 optic neuropathy). Asymptomatic peritumoral imaging changes compatible with an adverse radiation effect developed in 1 patient. CONCLUSION: SRS provides satisfactory control rates either after resection or as an alternative to resection. Its role is most valuable for patients whose tumors affect critical neurological regions and who are poor candidates for resection.

Middle turbinate flap for skull base reconstruction: cadaveric feasibility study.

OBJECTIVES/HYPOTHESIS: Surgical resection of intradural pathology through an endonasal corridor creates defects that communicate the subarachnoid space with the sinonasal tract. Reconstruction of these defects with vascularized tissue is superior to any other method. The purpose of this study is to describe a novel vascularized pedicled flap from the middle turbinate (MT) mucosa and to assess its feasibility using a cadaveric model. METHODS: Twelve middle turbinate flaps (MTFs) were raised in six fresh cadaveric heads previously injected with colored silicone. Arteries supplying the MT were identified as the turbinate mucoperiosteum was harvested from both its medial and lateral aspects. Length and surface area of the flaps, as well as their ability to cover dural defects of the sella, planum sphenoidale, and fovea ethmoidalis reach were noted. RESULTS: All MTFs adequately covered defects of the planum and fovea ethmoidalis; however, two of the twelve MTFs were not suitable to cover a sellar defect. The mean surface area of the MTFs was 5.6 cm(2). As an independent factor surface area did not correlate with the ability of the flap to cover the sellar defects. However, those flaps that were not suitable for sellar repair were less than 4.0 cm in length. CONCLUSIONS: Harvesting of a vascular pedicle flap from the MT is feasible, albeit technically demanding. It should be considered as an alternative for the reconstruction of small defects of the fovea ethmoidalis, planum, and sella, particularly for patients for whom a reconstruction with vascularized tissue is desirable but the nasoseptal flap is not available.

Sphenoid septations and their relationship with internal carotid arteries: anatomical and radiological study.

OBJECTIVES/HYPOTHESIS: We sought to investigate the anatomical relation of the intrasphenoid septations to the internal carotid artery (ICA). METHODS: Twenty-seven preoperative high-resolution computed tomography angiographic (CTA) scans with 1 mm of separation acquisition were examined. In addition, an endoscopic endonasal approach and high-resolution computed tomography were done on 27 fresh-frozen cadaveric heads. The number of intrasphenoid septa and their relation to the ICAs were analyzed endoscopically and radiologically. Complete and incomplete septations were included in the analysis. A total of 54 sphenoid sinuses were studied. RESULTS: Out of 27 sphenoid sinuses radiologically studied from real patients, 23 (85%) and 11 (41%) had at least one or two septa, respectively, touching one of the ICA. Out of 27 sphenoid sinuses endoscopically examined from cadavers (excluding one conchal type), 24 (89%) had at least one septation inserted in the ICAs. Two or more septations were inserted in the carotid prominence in 48% of sphenoid sinuses. The radiological examination of the anatomical specimens revealed similar results, with discrepancy in just one case (1/27) where it did not identify an incomplete septation inserting at ICA. No significant differences were found between the groups. From a total of 54 sphenoid sinuses studied, 47 (87%) had at least one septum related to the ICA, and only 13% presented a typical isolated midline septation. CONCLUSIONS: As demonstrated both radiographically and endoscopically, most intrasphenoidal septa insert at the parasellar or paraclival carotid prominence. As such, extreme care should be taken when identifying and removing these septations intraoperatively.

Radiosurgery as definitive management of intracranial meningiomas.

OBJECTIVE: Stereotactic radiosurgery has become an important primary or adjuvant minimally invasive management strategy for patients with intracranial meningiomas with the goals of long-term tumor growth prevention and maintenance of patient neurological function. We evaluated clinical and imaging outcomes of meningiomas stratified by histological tumor grade. METHODS: The patient cohort consisted of 972 patients with 1045 intracranial meningiomas managed during an 18-year period. The series included 70% women, 49% of whom had undergone a previous resection and 5% of whom had received previous fractionated radiation therapy. Tumor locations included middle fossa (n = 351), posterior fossa (n = 307), convexity (n = 126), anterior fossa (n = 88), parasagittal region (n = 113), or other (n = 115). RESULTS: The overall control rate for patients with benign meningiomas (World Health Organization Grade I) was 93%. In those without previous histological confirmation (n = 482), tumor control was 97%. However, for patients with World Health Organization Grade II and III tumors, tumor control was 50 and 17%, respectively. Delayed resection after radiosurgery was necessary in 51 patients (5%) at a mean of 35 months. After 10 years, Grade 1 tumors were controlled in 91% (n = 53); in those without histology, 95% (n = 22) were controlled. None of the patients developed a radiation-induced tumor. The overall morbidity rate was 7.7%. Symptomatic peritumoral imaging changes developed in 4% of the patients at a mean of 8 months. CONCLUSION: Stereotactic radiosurgery provided high rates of tumor growth control or regression in patients with benign meningiomas with low risk. This study confirms the role of radiosurgery as an effective management choice for patients with small to medium-sized symptomatic, newly diagnosed or recurrent meningiomas of the brain.