Incidence of microemboli and correlation with platelet inhibition in aneurysmal flow diversion

Flow-diverting stents have been associated with embolic and hemorrhagic complications, but the rate of procedure-related microemboli is unknown. Using transcranial Doppler sonography, we measured the rate of microemboli in 23 patients treated with flow-diverting stents. Patients received preprocedural dual antiplatelet medications and intraprocedural heparinization. Point-of-care platelet reactivity testing was performed before the procedure, and nonresponders (>213 P2Y12/ADP receptor reactivity units) received additional thienopyridine. Transcranial Doppler sonography was performed within 12-24 hours. Microemboli were detected in 3 patients (13%), 2 of whom were initially nonresponders. There was no association between the presence of microemboli and procedural or neurologic complications, aneurysm size, number of stents, or procedure time. Eight procedures (34.8%) required additional thienopyridine for inadequate platelet inhibition, and 3 required further treatment for persistent nonresponse to point-of-care platelet reactivity testing. There were 6 technical and 2 postoperative complications; none were associated with inadequate platelet inhibition or microemboli. The combination of routine point-of-care platelet reactivity testing and postprocedural microembolic monitoring may help identify patients at risk for thromboembolic complications after flow-diverting stents.

Endovascular management of cerebral bypass graft problems: an analysis of technique and results

BACKGROUND AND PURPOSE

Cerebral bypass grafts may develop generalized graft narrowing or focal stenosis during the perioperative period or later. Endovascular techniques such as PTA and stent placement of graft vessels are potential treatment options. Our objective was to review the safety, indications, technique, and results of endovascular management of graft problems.

MATERIALS AND METHODS

All patients with cerebral bypass procedures by using graft vessels from 2005 to 2009 were identified from a prospective registry and were studied retrospectively. Patient characteristics, bypass procedures, indications for endovascular interventions, graft patency, and clinical outcomes were reviewed from medical charts and imaging records.

RESULTS

A total of 79 patients underwent bypass procedures by using graft vessels. Seven patients of this group underwent endovascular interventions for the treatment of graft narrowing. Four of the 7 patients were treated for graft narrowing in the perioperative period (<1 month) with PTA; and 3 of the 7 patients, for late stenosis, 2 with PTA alone and 1 with PTA followed by stent placement. All procedures were immediately successful in improving flow through the graft. In late stenosis, PTA alone provided temporary improvement followed by recurrence, whereas PTA with a stent procedure was effective in the 1 patient long term.

CONCLUSIONS

PTA is safe and effective in the management of graft spasm in the perioperative period. For late graft stenosis, PTA alone provides only temporary respite, while PTA with stent placement may be an effective solution.

Paraseller meningiomas: incidence of involvement of extracavernous structures as determined by magnetic resonance and computed tomography

Parasellar meningiomas frequently extend beyond the cavernous sinus into adjacent structures. In order to determine the incidence of involvement of adjacent sites, we retrospectively evaluated the computed tomography and nuclear magnetic resonance scans of 65 consecutive patients with meningiomas invading the cavernous sinus. Thirteen nearby anatomic sites were analyzed for tumor involvement. The sites most frequently involved were the lateral sphenoid sinus wall (93%), the ipsilateral petrous apex (70%), the ipsilateral posterior petrous bone surface (59%), the sella (59%), the intracranial clival surface (44%), and the suprasellar cistern (41%). The sella, clival bone marrow, orbital apex, pterygopalatine fossa, and prestyloid parapharyngeal space were more commonly involved in recurrent tumors. Lesions were also subdivided into five groups according to whether or not they involved only one part of the cavernous sinus (grade 1), two parts of the cavernous sinus (grade 2), surrounded the cavernous carotid artery (grade 3), surrounded and narrowed the cavernous carotid artery (grade 4), or involved both sides of the cavernous sinus (grade 5). Among the 63 cases that could be assigned to a category, seven were grade 1 lesions, 13 were grade 2, 13 were grade 3, 16 were grade 4, and 14 were grade 5. Tumor grade is helpful in predicting the difficulty of resection of the cavernous component of the tumor. The incidence of involvement of adjacent sites is also helpful in assessment of imaging studies and in planning the most appropriate surgical approach.

Postoperative hydrocephalus in cranial base surgery

The incidence of postoperative hydrocephalus and factors relating to it were analyzed in 257 patients undergoing cranial base surgery for tumor resection. A total of 21 (8%) patients developed postoperative hydrocephalus, and all required shunting, Forty-two (17%) patients developed cerebrospinal fluid (CSF) leak that required placement of external drainage systems (ventriculostomy or lumbar drain, or both); 10 (23%) of these 42 patients eventually needed shunt placement to stop the leak because of hydrocephalus. Prior craniotomy, prior radiation therapy, and postoperative CSF infection were also associated with an increased risk of developing hydrocephalus (48% versus 6%, 19% versus 8%, and 14% versus 7%, respectively). Prior radiation and postoperative CSF infection increased the risk of CSF leak in patients with hydrocephalus (30% versus 18% and 30% versus 9%, respectively). CSF leak and hydrocephalus commonly occurred in patients who underwent resection of a glomus tumor. In conclusion, 8% of patients who underwent cranial base surgery for tumors developed de novo hydrocephalus; half of them also had CSF leak in addition to hydrocephalus; and all required shunt placement for CSF diversion.

A protocol for measuring ophthalmologic morbidity and recovery after cranial base surgery

Patients with cranial base tumors often have impairment in visual function, either due to the pathologic process itself or as a result of surgical treatment of the lesion. We conducted a pilot study in which we performed ophthalmologic evaluations on patients before and after cranial base surgery. The results of the study were used to develop a protocol and reporting form for longitudinal assessment of visual function in these patients. Use of the protocol and reporting form for the past 2(1/2) years has shown that they are easy for physicians to use and that the results provide a representative evaluation of the patient's ability to function visually in everyday life. The authors propose implementation of the protocol and reporting form as a means of collecting data for further research into visual function in patients with cranial base tumors.

Meningiomas with vertebrobasilar artery encasement: review of 17 cases

Seventeen patients with petroelival and foramen magnum meningiomas encasing the vertebral or basilar arteries and their branches were surgically excised over a 3-year period. All six cases with vertebral artery encasement were totally excised. One vertebral artery was occluded, one was repaired, and one was replaced with a vein graft. None of the patients had a permanent major neurologic deficit. In one patient with vertebral and basilar artery encasement, a hypoplastic vertebral artery was occluded and the tumor was totally excised. She had a transient worsening of hemiparesis, presumably due to the dissection of tumor from the brainstem. Among the ten patients with encasement of the basilar artery and branches, injury to the basilar artery occurred in two patients, both were repaired. Injuries to one superior cerebellar artery, one anterior inferior cerebellar artery, and one perforating vessel could not be repaired. Three patients sustained major neurologic deficits, but only in two did this result in permanent functional deterioration. Three of the ten patients had a gross total resection, five had subtotal resection (90% or more of tumor volume), and two had resection of 70% of the tumor volume. Eight patients had improvement in their Karnofsky scores. None showed recurrence or regrowth on follow-up ranging from 2 to 6 years. Greater difficulty with dissection was experienced in previously operated patients, and in patients who did not have an arachnoid plane between the brainstem and the tumor. Magnetic resonance imaging was the most useful preoperative test. It is concluded that meningiomas with vertebrobasilar artery encasement can be removed successfully with modern skull base surgery techniques. The surgeon needs to exercise caution and judgment in deciding how far the removal of these lesions should be pursued.

Emergent middle cerebral artery embolectomy: a useful technique for cranial base surgery

Given the poor natural history of untreated symptomatic acute middle cerebral artery occlusion, we have attempted emergent reperfusion in all three cases of acute embolic middle cerebral artery occlusion seen on our cranial base service over the last 10 years. One patient developed a massive stroke requiring a life-saving "strokectomy" within 48 hours, which left him permanently hemiplegic, hemianopic, and hemihypesthetic after a failed attempt at reperfusion by superselective endovascular injection of urokinase. The other two patients, who were aphasic and densely hemiparetic, underwent successful emergent embolectomy with reperfusion established within 5 and 12 hours, respectively. One of the two is now neurologically normal, and the second is left with a subtle monoparesis but is independent in activities of daily living. Since middle cerebral artery embolism in cranial base patients usually occurs in a closely monitored hospital setting, we are presented with a unique opportunity for early successful operative intervention. Principles for optimizing outcome include: early recognition and diagnosis, maximization of medical therapy during the diagnostic workup prior to embolectomy (induced hypertension, intravascular volume expansion, and pharmacologic cerebral metabolic demand reduction), confirmation that the involved region does not have absent blood flow by xenon/computed tomography, early operative intervention, and careful surgical technique.

Complications of preoperative balloon test occlusion of the internal carotid arteries: experience in 300 cases

Treatment of some tumors and aneurysms of the skull base may require internal carotid artery (ICA) sacrifice. Preoperatively to determine the dependence of the cerebral blood flow on a particular vessel, we perform a balloon test occlusion (BTO) by temporarily occluding the vessel in an awake patient. During occlusion, clinical evaluations and cerebral blood flow measurements are assessed. We have performed 300 BTOs. Eleven patients (3.7%) have had complications. Six (2%) were asymptomatic dissections. Five (1.7%) had neurologic deficits that persisted beyond the test period. Of these five, one was back to baseline in less than 24 hours, one recovered completely in a week, and one (0.33%) had a minimal but persistent dysphasia. These latter three cases are unexplained but might have resulted from unrecognized dissections or embolic events. Finally, one patient with a persistent deficit required energency surgery for reasons unrelated to the BTO and was therefore difficult to assess, and one required emergency middle cerebral artery embolectomy and repair of the dissection. The preoperative knowledge of carotid dependence in cases in which the ICA is at risk is essential, since vascular grafts or alternative surgical approaches are necessary in patients unable to tolerate carotid sacrifice. Since approximately 15 to 20% of the population falls into this category, a preoperative BTO appears justified.

Management of Zone III Missile Injuries Involving the Carotid Artery and Cranial Nerves

Carotid and cranial nerve injuries from zone III (high cervical/cranial base) missile injuries are rare and difficult to treat. We have treated five patients with such injuries. We present our management scheme, and compare it to the management of the same injuries in other reports. Five consecutive zone III missile injuries presented to our institution. Trauma assessment by the trauma team, followed by detailed neurological assessment and radiographs (angiogram and computed tomography) were obtained on admission. All patients presented with dysphagia and carotid artery injury with good collateral flow, documented by angiogram. Two patients had facial nerve injury, one had trigeminal nerve injury, one patient presented with tongue weakness, and one patient suffered conductive hearing loss. No patient had evidence of stroke clinically or radiographically. Carotid artery injury was managed with bypass (3 of 5) or ligation (2 of 5). Cranial nerve injuries were documented and treated aggressively with surgery if needed. All patients were discharged to home. Patients presenting with zone III missile injuries should receive an expeditious neurological exam and four-vessel angiogram after initial trauma survey and resuscitation. Bypass of the injured portion of carotid artery is a valid treatment in the hemodynamically stable patient. The unstable patient should undergo ligation to stop hemorrhage and protect against immediate risk for stroke, with the option to bypass later. Cranial nerve injuries should be pursued and aggressively treated to minimize morbidity and prevent mortality.

FACT-MNG: tumor site specific web-based outcome instrument for meningioma patients

To formulate Functional Assessment of Cancer Therapy-Meningioma (FACT-MNG), a web-based tumor site-specific outcome instrument for assessing intracranial meningioma patients following surgical resection or stereotactic radiosurgery. We surveyed the relevant literature available on intracranial meningioma surgery and subsequent outcomes (38 papers), making note of which, if any, QOL/outcome instruments were utilized. None of the surgveyed papers included QOL assessment specific to tumor site. We subsequently developed questions that were relevant to the signs and symptoms that characterize each of 11 intracranial meningioma sites, and incorporated them into a modified combination of the Functional Assessment of Cancer Therapy-Brain (FACT-BR) and SF36 outcome instruments, thereby creating a new tumor site-specific outcome instrument, FACT-MNG. With outcomes analysis of surgical and radiosurgical treatments becoming more important, measures of the adequacy and success of treatment are needed. FACT-MNG represents a first effort to formalize such an instrument for meningioma patients. Questions specific to tumor site will allow surgeons to better assess specific quality of life issues not addressed in the past by more general questionnaires.

Outcomes of ruptured intracranial aneurysms treated by microsurgical clipping and endovascular coiling in a high-volume center

BACKGROUND AND PURPOSE

The purpose of this study was to analyze the 3-month outcomes of patients with aneurysmal subarachnoid hemorrhage (SAH) treated from January 2005 to June 2006. This paper describes the outcomes after treatment of aneurysmal SAH and comparison between patients treated by clipping or coiling in a high volume center.

MATERIALS AND METHODS

A retrospective chart review was performed of records of 195 consecutive patients with SAH. The overall outcome and the pretreatment variables predicting outcomes and the difference between the clipping and coiling groups were analyzed by logistic regression analysis.

RESULTS

A total of 105 (55%) patients had microsurgical clipping and 87 (45%) had endovascular coiling. At 3 months, 69% of patients recovered with no or mild disability. The predictors of a 3-month modified Rankin Scale (mRS) were Hunt and Hess (HH) grade on admission and the presence of intracerebral hemorrhage (ICH). Patients in the coiling group had worse admission grades; they had worse 3-month mRS (2.28 vs 1.73), but this was not significant when the groups were matched (P = .38). Vasospasm rate was significantly higher in the clipping group (66% vs 52%). The immediate incomplete occlusion rate of aneurysms was higher (21.7% vs 7.6%) in the coiling group.

CONCLUSION

The overall results of treatment of aneurysmal SAH have improved. There is no significant difference in the outcomes between the patients in the clipping and coiling groups.

Outcome analysis of preoperative embolization in cranial base surgery

OBJECTIVE

Management of cranial base tumors requires an interdisciplinary approach. Supraselective angiography and embolization is an important adjunct to cranial base surgery. Though successful embolization facilitates resection, the morbidity of this procedure remains poorly defined. Therefore, we set out to define the morbidity associated with embolization of skull base meningiomas, thus allowing for informed decision making when considering this adjunct to tumor resection.

METHODS

A retrospective analysis was performed on our experience with embolization of 167 cranial base meningiomas. Cranial base meningiomas were defined as tumors originating from the olfactory groove, tuberculum sella, medial sphenoid wing, petro-clival region or foramen magnum.

RESULTS

280 feeding vessels were embolized with an average of 1.7 vessels per lesion. In 91% of patients embolized, good to excellent embolization was achieved without permanent neurological sequelae. In 20 patients no embolization was attempted due to the risk of new neurologic deficits or lack of an appropriate vessel for embolization. Twenty-one patients (12.6%) had transient worsening of their neurologic exam or a medical complication requiring hospitalization. Fifteen patients (9%) experienced permanent neurologic deficits or medical morbidity as a result of embolization. Four of the patients who experienced major complications had a decline in previously compromised cranial nerve function.

CONCLUSIONS

Embolization of cranial base tumors is an important part of the therapeutic armamentarium for the treatment of cranial base lesions. Recognition of the morbidity of this procedure will allow for the most appropriate use of this powerful adjunct to cranial base surgery.

Brain stem cavernoma excised by subtemporal-infratemporal approach

Brain stem cavernomas are most safely removed through the pial surface at which the cavernoma is surfacing. When a lower pontine or an upper medullary cavernoma comes to the surface of the anterior portion of the brain stem, it is difficult to reach by traditional approaches. We describe a case of mid- and lower pontine cavernoma, surfacing anteriorly, which was completely excised by the subtemporal-infratemporal approach. After making a small temporal craniotomy and a zygomatic osteotomy, the petrous carotid artery was mobilized anteriorly and the petroclival bone was drilled away to reach the anterior surface of the pons using the subtemporal-infratemporal approach. A small incision was made on the anterior surface of the pons, between the CN V and CN VI and the cavernoma was completely excised with the aid of the surgical microscope and the neuro-endoscope. Immediately after the operation, the patient had a complete abducens palsy and a mild increase of left hemiparesis, both of which resolved completely within 3 months. The patient returned to the full time work without any neurological deficit. A follow-up MRI 1 year later showed the complete excision of the cavernoma. The subtemporal-infratemporal approach is useful for anteriorly located mid to lower pontine and upper medullary cavernomas.

Brain-stem abscess successfully treated by microsurgical drainage: a case report

Brain-stem abscess is an uncommon condition associated with high mortality. The best method of treatment is not yet defined. It can be managed by medical treatment alone, stereotactic aspiration of the pus and medical treatment, or surgical excision/drainage of the abscess. We present a case of large brain-stem abscess, treated successfully by surgical drainage after the failure of medical treatment. The patient had a large brain-stem abscess extending from the mid-brain down to the lower pons. She was in a poor neurological condition pre-operatively, and was worsening despite intravenous antibiotics. The abscess was coming close to the surface in the lateral aspect of the mid-brain. The presumed source of infection was multiple dental abscesses. The brain-stem abscess was approached by a subtemporal transzygomatic approach and drained completely after making an incision on the lateral surface of the mid-brain. After the operation, the patient showed steady improvement. At six months after the surgery, the patient was fully conscious, talking fluently, and walking with the help of a walker. Her hemiparesis and co-ordination were improving. Surgical drainage of a brain-stem abscess is indicated when medical therapy fails. Proper anatomical knowledge of the brain-stem and the selection of appropriate surgical approach is important for safe drainage of the abscess.

Cerebral revascularization using radial artery grafts for the treatment of complex intracranial aneurysms: techniques and outcomes for 17 patients

OBJECTIVE

The goal of this report is to illustrate the use of radial artery grafts as bypass conduits in the management of complex intracranial aneurysms and to describe a new "pressure distension technique" to eliminate postoperative vasospasm, which was a common problem early in our experience.

METHODS

This study included a series of 17 patients who were surgically treated between 1994 and January 2001 for complex intracranial aneurysms. Five patients were surgically treated without the pressure distension technique; for 12 patients, the technique was used to reduce postoperative vasospasm. Fourteen of the patients had anterior circulation aneurysms, and three had posterior circulation aneurysms. Five of the patients had undergone previous attempts at direct clipping or excision and reconstruction of the aneurysm in question, and embolization had been performed for one patient with a carotid-cavernous fistula. Thirteen patients underwent permanent revascularization combined with proximal occlusion, trapping, or clipping, and four patients underwent temporary revascularization for cerebral protection during anticipated prolonged occlusion of the parent vessel during aneurysm dissection. Surgical techniques are described, with particular reference to vessel collection and bypass techniques.

RESULTS

The outcomes for this group of patients, considering the complexity of the aneurysms and their "inoperability," with respect to direct clipping, were satisfactory. The aneurysms were completely obliterated for all patients, and the grafts were patent for all except one patient on postoperative angiograms. There were two deaths, one attributable to systemic sepsis and the other attributable to cardiac arrest during a transbronchial biopsy. The postoperative Glasgow Outcome Scale scores were either better or the same for all other patients, compared with their preoperative scores. Three of the five patients treated before the institution of the pressure distension technique experienced vasospasm of the graft, with two of those patients requiring angioplasty. For one of those patients, angioplasty led to rupture of the graft. Vasospasm was not observed for any of the 12 patients for whom the pressure distension technique was used. We observed no morbidity related to radial artery collection.

CONCLUSION

Revascularization techniques are occasionally necessary for the surgical treatment of complicated intracranial aneurysms. The merits of the use of the radial artery as a bypass conduit are discussed. Radial artery grafts should be considered as alternatives to saphenous vein and superficial temporal artery grafts. The problem of vasospasm of the artery has been solved with the pressure distention technique.

Dural reconstruction with fascia, titanium mesh, and bone screws: technical note

OBJECTIVE

After the resection of cranial base tumors, there may not be enough free dural margin left for reconstruction after involved bone and dura have been removed. In such a situation, dural reconstruction becomes a problem. We propose a new technique of dural closure in such cases.

METHODS

A fascial graft is prepared from either fascia lata, abdominal fascia, pericranium, or temporal fascia and is trimmed to a size slightly larger than that of the dural defect. The fascial graft is placed over the dural defect and affixed to the underlying bone with a piece of titanium mesh, titanium screws, or both. The graft is then reinforced with fibrin glue.

RESULTS

This method of dural reconstruction has been used in five patients with basal meningiomas. Three were in the petromastoid area, and two were in the planum-ethmoid area. None of these patients experienced postoperative cerebrospinal fluid leak, and none experienced any complications related to the reconstruction.

CONCLUSION

This technique of dural reconstruction can be used in selected cases of basal tumors without enough free dural margin to sew into a fascial graft.

Cerebral revascularization in cranial base tumors

Certain cranial base tumors may involve intracranial arteries by encasement or invasion. In such patients, resection of the tumor along with the involved artery is an option for treatment. Techniques and results of vascular bypasses for such lesions are discussed in this article.

Posterior fossa meningiomas: surgical experience in 161 cases

BACKGROUND

We report the clinical, radiological, and surgical findings of patients with posterior fossa meningiomas surgically treated at our institution over the last 6 years.

METHODS

We reviewed 161 consecutive cases of posterior fossa meningiomas operated on between April 1993 and April 1999 at The George Washington University Medical Center.

RESULTS

There were 128 female and 33 male patients (mean age 47 years, range of 10-81 years). Meningiomas were classified as petroclival (110 cases), foramen magnum (21 cases), cerebellar hemispheric, lateral tentorial (14 cases), cerebellopontine angle (9 cases), and jugular foramen (7 cases). Mean tumor equivalent diameter (TED) = (D1xD2xDE)(1/3) was 3.1 cm (range of 0.53-8.95). Head pain (50% of cases) and disturbance of gait (44%) were the most common presenting symptoms, and cranial neuropathies the most common neurological signs on admission. Mean preoperative performance status (Karnofsky scale) was 80.2 (range 40-100). Surgical approaches to these tumors included partial labyrinthectomy petrous apicectomy, fronto-temporal/fronto-temporal orbitozygomatic osteotomy, retrosigmoidal, extreme lateral, transpetrosal, and combined. In 38 cases a staged procedure was performed. Gross-total resection was achieved in 57% of patients, and subtotal/partial in 43%. Surgical mortality was 2.5% and complications were encountered in 41% of patients. Postoperative CSF leak occurred in 22 cases (13.6%). The mean follow-up was 19 months, ranging from 0.2 to 63.6, and the mean performance status of patients with a follow-up of at least 12 months was 77 (range of 40-100). Recurrence or progression of disease was found in 13.7% of cases (follow-up 2 years or more).

CONCLUSION

Our experience suggests that although posterior fossa meningiomas represent a continuing challenge for contemporary neurosurgeons, such tumors may be completely or subtotally removed with low rate of mortality and acceptable morbidity, allowing most of these patients to achieve a good outcome in a long-term follow-up.

Chordomas and chondrosarcomas of the skull base: results and complications of surgical management

Object

Chordomas and chondrosarcomas are rare and difficult to treat tumors for which the optimum treatment modality remains controversial. The aim of this study was to evaluate the surgery-related results and complications in a series of patients in whom radical resection was the treatment of choice.

Methods

The authors conducted a retrospective analysis of the surgery-related results and complications associated with chordoma and chondrosarcoma in 64 patients of whom 33 (52%) had previously undergone some form of treatment. Total or near-total excision was achieved in 56% and this rate increased to 68% in patients without prior treatment. The main complications were postoperative cerebrospinal fluid leakage, intraoperative arterial injury, and new-onset cranial nerve deficits. Arterial injury occurred only and perioperative death occurred more often in patients who had undergone previous treatment.

Conclusions

Analysis of the results provides support for a policy of radical excision of chordomas and chondrosarcomas at the time of first presentation. A higher incidence of procedure-related complications is found in patients who have already undergone surgery and radiotherapy.

Intermittent vertebral artery compression caused by C1-root schwannoma: case report

Extradural schwannomas of the C1-root are extremely rare. As the tumor grows in size, it may compress surrounding neurovascular structures and cause symptoms. In the present case report, the left vertebral artery (VA) was severely compressed by the tumor, eliciting severe vertigo on turning the head to the right side and with neck extension. We report a 52-year-old man who presented with a history of intermittent episodes of severe vertigo on head movement that was caused by a C1-root schwannoma. The lesion was exposed through an extreme lateral transcondylar approach. At exposure the lesion was yellowish in color and was extradural in location lying between the markedly eroded C1-posterior arch and the compressed vertebral artery (V3) on the left side. The medial portion of the tumor was attached to the C1-nerve root. The tumor was excised enbloc with decompression of the VA. The patient's symptoms completely resolved immediately following surgery, with no recurrence of the symptoms at one year follow up. The vertebral artery may frequently be compressed by osteophytes in cervical spondylosis or due to other causes in the cervical spinal canal, but compression of the artery by C1 extradural schwannoma with vascular insufficiency is rare. Removel of the tumor and the resultant decompression of the artery can be facilitated by the extreme lateral approach as demonstrated by this case.

Vertebral artery to common carotid artery bypass in Takayasu's disease with delayed cerebral ischemia

Takayasu's Arteritis is a progressive occlusive disease of the aortic arch and its branches. It may need several bypass procedures along with or without endovascular techniques.

CASE DESCRIPTIONS

A twenty-six year old woman who had a history of Takayasu's Arteritis, and had a Gore-Tex Dacron Y-graft from the ascending aorta to the right subclavian and right common carotid arteries 18 years before, is presented. She presented with recurrent hemispheric ischemia and transient ischemic attacks and severe long segment stenosis in the left common carotid artery. She was successfully treated with a saphenous vein graft bypass from the left vertebral artery to the common carotid artery. The stenosis of the brachiocephalic graft was successfully treated by angioplasty. Three months follow up showed stenosis of the left VA immediately proximal to the proximal anastomosis which was managed successfully with angioplasty.

CONCLUSIONS

The surgical treatment of Takayasu's Arteritis with bypass procedures needs a complex overview and follow up. A regular follow up is mandatory for evaluation and planning of appropriate management, in view of the progressive nature of the disease process.

Occipitocervical fusion following the extreme lateral transcondylar approach

BACKGROUND

Modern cranial base approaches to the clivus and foramen magnum may threaten the stability of the cranio-cervical junction. This necessitates stabilization and fusion in some cases. We studied occipitocervical fusion after extreme lateral transcondylar approaches.

METHODS

Twenty-seven patients underwent an extreme lateral transcondylar approach over a 2-year period. Two patients were excluded because of prior occipitocervical fusion. The pathological diagnosis was meningioma in ten patients, chordoma in six patients, neurofibroma in two, and 10 patients had other tumoral and nontumoral pathologies.

RESULTS

Eight patients required occipitocervical fusion and stabilization. Five of six patients with chordomas required fusion, whereas no patient with a meningioma underwent fusion. All the patients who were fused had more than 70% resection of their occipital condyle. No patient with resection of less than 70% of the occipital condyle required fusion. Significant interference of the surgical construct with follow-up imaging was seen only in the patient in whom a stainless steel Steinman pin was used.

CONCLUSION

One third of patients will require fusion after extreme lateral transcondylar approaches. Most patients with less than 70% resection of the condyle remain stable without need for surgical intervention, whereas complete resection necessitates fusion in most cases.

Use of intra-aortic balloon pump counterpulsation for refractory symptomatic vasospasm

Delayed neurologic deficits secondary to vasospasm remain a vexing problem. Current treatments include: hypertensive hypervolemic hemodilution (Triple-H) therapy, angioplasty, and intra-arterial papaverine administration. Significant morbidity and mortality still result from vasospasm despite these therapies. We present two patients with symptomatic vasospasm who received intra-aortic balloon pump counterpulsation (IABP) to improve cerebral blood flow when they were unable to tolerate Triple-H therapy. One patient (L.T.) developed vasospasm after resection of a meningioma that encased the carotid and middle cerebral artery. The other patient (D.F.) suffered a subarachnoid hemorrhage (Fisher Grade III, Hunt/Hess Grade III) from a basilar tip aneurysm. Postoperatively, both patients developed vasospasm. Treatment with Triple-H therapy, angioplasty, and papaverine yielded modest results. When they experienced cardiac ischemia, Triple-H therapy was stopped, but their neurologic condition deteriorated markedly. Because of this, IABP was started. Both patients had an immediate improvement in cardiac function. IABP was able to reverse some of the neurologic deficits, and was weaned off after several days of support. Both patients had a substantial improvement in function, and are now capable of caring for themselves. We conclude that IABP may play an important role for improving cerebral blood flow in patients with vasospasm. It may be particularly useful in those patients with limited cardiac reserve.

Early arytenoid adduction for vagal paralysis after skull base surgery

OBJECTIVES

To evaluate the efficacy of early arytenoid adduction in the management of vagal paralysis after skull base surgery.

STUDY DESIGN

Retrospective evaluation at a tertiary care skull base center.

METHODS

Aggressive surgical management of skull base lesions has become increasingly popular owing to advances in surgical technique and intraoperative monitoring. Temporary and permanent lower cranial neuropathies occur frequently, especially after the surgical management of lesions involving the vertebrobasilar system and the jugular foramen. An injury to the proximal vagus nerve is usually associated with dysphonia and swallowing dysfunction. An early arytenoid adduction has been employed in 26 patients with a vagal paralysis after skull base surgery. Most commonly, the neurosurgical patient underwent an arytenoid adduction under general anesthesia on postoperative day 2.

RESULTS

Videostroboscopy after arytenoid adduction demonstrated 76% of patients had complete glottic closure. Of those with inadequate glottic closure, all demonstrated a well-medialized posterior glottis with a persistent anterior glottal gap. These patients were easily treated with a secondary type I thyroplasty under local anesthesia with sedation resulting in complete glottic closure. Despite excellent voice outcomes, 66% of these patients had dysphagia requiring enteral feedings for nutritional support.

CONCLUSIONS

An early arytenoid adduction is an excellent medialization technique that can be performed safely in the early postoperative period under general anesthesia after skull base surgery.

The rubber dam interposition technique during intracranial aneurysm clipping under deep hypothermic circulatory arrest

OBJECTIVE

We describe a technique for isolating perforating arteries by use of a rubber sheet during the clipping of intracranial aneurysms under deep hypothermic circulatory arrest.

METHODS

After meticulous dissection of the perforating arteries from the aneurysm, a rubber sheet, cut from a surgical glove to the proper shape, is inserted between the aneurysm and the arteries to prevent arterial reattachment to the aneurysmal neck.

RESULTS

Even when perforators are invisible at the time of neck clipping because of a large aneurysmal body, the blade of the clip slides along the rubber sheet without injuring the vessels.

CONCLUSION

With this method, an aneurysm, especially a large or giant one, can be clipped easily and safely even when the patient is in deep hypothermic circulatory arrest.

Vasospasm after cranial base tumor resection: pathogenesis, diagnosis, and therapy

OBJECTIVE

Cerebral vasospasm is well known to occur after various cerebral neurosurgical events that cause subarachnoid hemorrhage. However, cerebral vasospasm can occur after cranial base tumor resection. We present a series of nine patients with angiographically evident vasospasm that was clinically symptomatic in eight of them.

METHODS

A total of 470 consecutive patients with cranial base tumors were operated in our institution between April 1993 and December 1996. Nine had evidence of cerebral vasospasm postoperatively (1.9% of the total population), of whom eight were asymptomatic. There were seven males and two females with an age range of 33 to 65 years (average 48.5 years). There were seven meningiomas, one chordoma, and one trigeminal schwannoma.

RESULTS

Vasospasm manifested clinically 1 to 30 days postoperatively in eight patients. Most patients were symptomatic within 7 days. In the ninth case, surgery was delayed when asymptomatic vasospasm was noted on an angiogram before second stage surgery. Symptoms included altered mental status in four patients, hemiparesis in three patients (one patient had both hemiparesis and altered mental status), and monoparesis in two patients. Factors that were found to correlate with a higher incidence of vasospasm were tumor size, total operative time, vessel encasement, vessel narrowing, and preoperative embolization. All eight patients with symptomatic vasospasm were treated with hypertensive, hypervolemic, hemodilutional (HHH) therapy. Five patients also underwent intraluminal angioplasty, in conjunction with papaverine in one case. One patient received intraarterial papaverine alone. Angiographic results were good in all patients. Significant clinical improvement was seen in six of the eight symptomatic cases.

CONCLUSION

Delayed neurological deterioration in a patient who has undergone cranial base tumor surgery not explained by an intracranial mass lesion should be promptly investigated with angiography. If vasospasm is diagnosed, it should be treated aggressively with hypertensive, hypervolemic, hemodilutional therapy and early angioplasty.

Proposed grading system to predict the extent of resection and outcomes for cranial base meningiomas

OBJECTIVE

This investigation was performed to construct a grading system for cranial base meningiomas that augments the current system of topographic labeling. This new system classifies cranial base meningiomas based on predicted surgical resection and patient outcomes.

METHODS

Two hundred thirty-two consecutive patients with cranial base meningiomas were surgically treated by the two senior authors between April 1993 and August 1997. Using standard statistical tests, a large number of preoperative, intraoperative, and follow-up findings were analyzed for correlation with the extent of resection. These included the presence of previous radiotherapy, Cranial Nerve III, V, and VI palsies, multiple fossa involvement, and vessel encasement.

RESULTS

Analysis revealed that each variable tested was independently and inversely correlated with total tumor resection (P < 0.002). We were able to construct a grading system based on these variables; when more variables are present, the grade is higher. With the grading system, lower-grade tumors were correlated with increased probabilities of total resection (r2 = 0.9947) and better patient outcomes, as measured by Karnofsky performance scale scores (r = 0.9291). We also found that, as a group, patients who underwent subtotal resection exhibited worse Karnofsky performance scale scores and had longer hospital stays.

CONCLUSION

The current system of classifying cranial base meningiomas provides no information regarding the tumor except location and no information concerning patient prognosis. We present a more useful system to categorize these tumors. Our scheme must be tested at other centers to corroborate our findings. This new grading system should serve to guide surgical treatment, inform patients, and improve communication among surgeons.

Surgical management of cavernous malformations of the brain stem

Different surgical approaches to the brain stem with results of excision of brain stem cavernous malformations are reported. Nine patients with brain stem cavernous malformations were operated with six different approaches. The patients were evaluated neurologically, and by magnetic resonance imaging (MRI) examination. All patients had at least one and often more episodes of haemorrhage. Seven patients underwent the total removal of the malformation, without recurrence. One patient with a large medullary cavernoma had recurrence, but without further growth. One patient with a large pontomesencephalic malformation and partial resection, suffered rebleeding due to residual cavernoma. The mean follow-up period was 49 months (range 3-112). The results of surgery were excellent or good in eight patients, and poor (worsening) in one. It is concluded that surgical resection is recommended for the cavernous malformations of the brain stem which are symptomatic, have bled or are growing, and are approachable through one of the pial surfaces of the brain stem. Different skull base approaches are useful for this procedure. Radiosurgery is not recommended in such cases.

Subtonsillar-transcerebellomedullary approach to lesions involving the fourth ventricle, the cerebellomedullary fissure and the lateral brainstem

We describe the use of the subtonsillar-transcerebellomedullary approach to laterally placed fourth ventricle and brain-stem lesions. The subtonsillar-transcerebellomedullary approach to the fourth ventricle and the lateral brainstem was used in six patients: three patients with tumours of the fourth ventricle and brainstem (two ependymomas and one papillary thyroid carcinoma metastasis), two patients with cavernous angiomas of the brainstem and one patient with a distal posterior inferior cerebellar artery (PICA) aneurysm. The microsurgical anatomy of this approach was studied in five cadaveric head specimens. The tumours and cavernous angiomas were removed and the distal PICA aneurysm was clipped successfully. In all patients the Karnofsky performance scale (KPS) was equal to or better than the preoperative status on follow-up examinations. The anatomical studies also revealed the extensive exposure provided with this approach. The subtonsillar-transcerebellomedullary approach is recommended for lesions occupying the cerebellomedullary fissure, and the lateral aspect of the fourth ventricle.

Clinoid and paraclinoid aneurysms: surgical anatomy, operative techniques, and outcome

BACKGROUND

Paraclinoid or ophthalmic segment aneurysms arise from the internal carotid artery (ICA) between the roof of the cavernous sinus and the origin of the posterior communicating artery. Clinoid aneurysms arise between the proximal and distal carotid dural rings. The complex anatomy of clinoid and paraclinoid ICA aneurysms often makes them difficult to treat by microsurgery. The natural history of these aneurysms varies, based on their location and anatomic relationships. Accurate preoperative assessment of the origin of these aneurysms is therefore a critical aspect of their management.

METHODS

The authors reviewed 35 clinoid and paraclinoid ICA aneurysms operated in 28 patients and classify them according to their anatomic location and angiographic pattern. The operative techniques, surgical outcomes, and indications for surgery are reviewed.

RESULTS

Based on surgical anatomy and angiographic patterns, the aneurysms were classified into two categories: clinoid segment and paraclinoid (ophthalmic) segment. The clinoid segment aneurysms consisted of medial, lateral and anterior varieties. The paraclinoid aneurysms could be classified topographically into medial, posterior and anterior varieties, or based on the artery of origin into ophthalmic, superior, hypophyseal, and posterior paraclinoid aneurysms. Ophthalmic aneurysms were most common (40%), followed by posterior ICA wall aneurysms (29%), superior hypophyseal aneurysms (14%), and clinoid aneurysms (17%). Twenty patients (71%) had single aneurysms. Of the remaining eight, six had bilateral aneurysms and two had unilateral multiple aneurysms. Of the 35 aneurysms, 32 were clipped satisfactorily, as confirmed by intraoperative or postoperative angiography. One small broad-based aneurysm was wrapped, and two others were treated by trapping and bypass techniques. Three patients who had bilateral aneurysms underwent successful clipping of four contralateral, left-sided aneurysms via a right frontotemporal, transorbital approach. On follow-up (mean, 39 months), 25 patients were in excellent condition (returned to their prior occupation), two were in good condition (independent, but not working), and one died postoperatively of vasospasm.

CONCLUSION

Our increased knowledge of anatomy and refinements in operative techniques have greatly improved the surgical treatment of clinoid and paraclinoid aneurysms.

Variations of the extreme-lateral craniocervical approach: anatomical study and clinical analysis of 69 patients

OBJECT

The aim of this study was to describe six variations of the extreme-lateral craniocervical approach, their application, and treatment results.

METHODS

During a 4-year period 69 patients underwent surgery in which six variations of the extreme-lateral craniocervical approach were performed. The variations included: the transfacetal approach (TFA), performed to treat four lesions in the upper cervical spine anterior or anterolateral to the spinal cord; the retrocondylar approach, to treat five intradural lesions located anterolateral to the medulla oblongata and six vascular lesions to expose the extradural segment of the vertebral artery (VA); the partial transcondylar approach (PTCA), to treat 18 intradural lesions located anterior to the medulla oblongata; the complete transcondylar approach (CTCA), to treat 13 extradural lesions that involved the lower clivus and anterior upper cervical spine; the extreme-lateral transjugular approach, to treat 14 jugular foramen tumors; and the transtubercular approach with or without division of the sigmoid sinus, to treat complex VA and vertebrobasilar junction aneurysms. An anatomical prosection was performed to study the surgical exposure of each of the six variations of the extreme-lateral craniocervical approach. Total removal was achieved in 35 (69%) of the patients with tumor; subtotal resection was achieved in 16 (31%) of those patients. In the 12 patients with VA aneurysms, seven underwent clipping, three underwent trapping and a vein graft bypass procedure, and two underwent trapping without the use of a bypass procedure. In five other patients, different cystic, inflammatory, and other vascular lesions were successfully treated. Fifty percent of the patients who underwent surgery via the TFA, 83% via the of the CTCA, and 11% via the PTCA required an occipitocervical fusion procedure. The mean Karnofsky Performance Scale score was 74.7 preoperatively and 76.4 postoperatively. Major complications were hydrocephalus (nine patients), cerebrospinal fluid leakage (seven patients), worsened cranial nerve function (seven patients), vertebrobasilar vasospasm (one patient), and sigmoid sinus thrombosis (one patient).

CONCLUSIONS

To treat lesions in the region of the foramen magnum and surrounding areas, the approach should be tailored to each specific lesion to provide the needed exposure without unnecessary operative steps.

Profound hypothermia and circulatory arrest with skull base approaches for treatment of complex posterior circulation aneurysms

OBJECTIVE

Cardiopulmonary bypass with profound hypothermia and circulatory arrest has seen a resurgence as an adjunct technique in neurological surgery. We report our experience with this technique in treating seven complex vertebro-basilar aneurysms.

METHODS

Skull base approaches were used in all cases, providing excellent exposure and minimizing brain retraction. There were six basilar artery aneurysms and one giant fusiform vertebro-basilar artery aneurysm. All aneurysms but one had an apparent neck, which could be clipped. The fusiform vertebro-basilar artery aneurysm was trapped, partially resected, and the circulation was reestablished with a saphenous vein graft from the cervical internal carotid artery to the mid-basilar artery.

RESULTS

Five patients had an excellent outcome and two had a good outcome at one year or at latest follow up. Two of the patients showed improvement of neurological deficits which were present before the surgical intervention.

CONCLUSION

Applying very strict selection criteria in this small series of patients with posterior circulation aneurysms, excellent or good results were achieved using the profound hypothermic circulatory arrest technique.

Partial labyrinthectomy petrous apicectomy approach to neoplastic and vascular lesions of the petroclival area

OBJECTIVE

To study the value of an improvement of the presigmoid petrosal approach to the petroclival area by the addition of partial labyrinthectomy and petrous apicectomy and to document hearing and other results.

METHODS

Thirty-six consecutive patients treated by this technique during a 2-year period were studied prospectively. The lesions treated included 33 petroclival neoplasms (25 meningiomas, 5 chordomas, 1 chondrosarcoma, 1 trigeminal schwannoma, and 1 epidermoid cyst) and 3 vertebrobasilar aneurysms. The patients underwent clinical, radiological, and neuro-otological examinations.

RESULTS

There was no perioperative mortality. Cranial nerve deficits involving Cranial Nerves III, IV, V, and VI occurred in 17 patients (47%) postoperatively. Cerebrospinal fluid leak occurred in 12 patients (33%). Four of these patients were treated by lumbar drainage, two patients were treated by lumboperitoneal shunt, and six patients required reoperation and repacking of the middle ear. Hydrocephalus occurred in five patients (13.9%). There was one case of meningitis and another of systemic sepsis. All 36 patients underwent postoperative audiometric evaluation. When serviceable hearing was present preoperatively (Gardner-Robertson Grades I or II), it was determined to be preserved at postoperative follow-up in 81% of the patients (26 of 32 patients).

CONCLUSION

The partial labyrinthectomy petrous apicectomy approach provided improved access to neoplasms of the clivus and petrous apex and the posterior cavernous sinus area and to vertebrobasilar aneurysms in the midclival area. This improvement in access permits more controlled and thorough treatment of these lesions, with reduced brain retraction and acceptable morbidity with respect to auditory function.

Reconstruction of the vein of Labbé by using a short saphenous vein bypass graft. Technical note

Protection of the vein of Labbé is a significant concern during surgery that involves retraction of the temporal lobe. A cranial base surgical approach, especially one via the presigmoid-petrosal route, carries considerable risk to this venous complex. A case is presented in which a large dominant vein of Labbé was injured during resection of a petroclival meningioma. This vein drained all the sylvian venous circulation as well as the lateral temporal surface; no connection to another venous system was noted. The vein was successfully reconstructed using a short saphenous vein bypass graft. Significant complications could have occurred without this reconstruction. The technique and benefits of this type of reconstruction are discussed.

Surgical anatomy of the infratemporal fossa: the styloid diaphragm revisited

INTRODUCTION

The infratemporal fossa (ITF) gives passage to most major cerebral vessels and cranial nerves. Dissection of the ITF is essential in many of the lateral cranial base approaches and in exposure of the high cervical internal carotid artery (ICA). We reviewed the surgical anatomy of this region.

METHODS

Direct foraminal measurements were made in seven dry skulls (14 sides), and the relationship of these foramina to each other and various landmarks were determined. Ten ITF dissections were performed using a preauricular subtemporal-infratemporal approach. Preliminary dissections of the extracranial great vessels and structures larger than 1 cm were performed using standard macroscopic surgical techniques. Dissection of all structures less than 1 cm was conducted using microsurgical techniques and instruments, including the operating microscope. The anatomic relationships of the muscles, nerves, arteries, and veins were carefully recorded, with special emphasis regarding the relationship of these structures to the styloid diaphragm. The dissection was purely extradural.

RESULTS

The styloid diaphragm was identified in all specimens. It divides the ITF into the prestyloid region and the retrostyloid region. The prestyloid region contains the parotid gland and associated structures, including the facial nerve and external carotid artery. The retrostyloid region contains major vascular structures (ICA, internal jugular vein) and the initial exocranial portion of the lower Cranial Nerves IX through XII. Landmarks were identified for the different cranial nerves. The bifurcation of the main trunk of the facial nerve was an average of 21 mm medial to the cartilaginous pointer and an average of 31 mm medial to the tragus of the ear. The glossopharyngeal nerve was found posterior and lateral to stylopharyngeus muscle in nine cases and medial in only one. The vagus nerve was consistently found in the angle formed posteriorly by the ICA and the internal jugular vein. The spinal accessory nerve crossed anterior to the internal jugular vein in five cases and posterior in another five cases. It could be located as it entered the medial surface of the sternocleidomastoid muscle 28 mm (mean) below the mastoid tip. The hypoglossal nerve was most consistently identified as it crossed under the sternocleidomastoid branch of the occipital artery 25 mm posterior to the angle of the mandible and 52 mm anterior and inferior to the mastoid tip.

CONCLUSION

The styloid diaphragm divides the ITF into prestyloid and retrostyloid regions and covers the high cervical ICA. Using landmarks for the exocranial portion of the lower cranial nerves is useful it identifying them and avoiding injury during approaches to the high cervical ICA, the upper cervical spine, and the ITF.

Persistent trigeminal artery: an anatomic study

INTRODUCTION

The most frequent embryonic communication between the vertebrobasilar and carotid systems is a persistent trigeminal artery (PTA). It has been observed in 0.1 to 0.2% of cerebral angiograms. We found this variation in an anatomic specimen, and after microscopic dissection, we performed an analysis of the course of the PTA and its relationship with the abducens nerve and the meningohypophyseal trunk.

METHOD

A PTA was incidentally encountered in an injected cadaver specimen during a transpetrosal approach. This embryonic variation and its anatomic relationship are discussed.

RESULTS

The PTA can take either a lateral or medial course regarding its relationship with the abducens nerve. When the PTA originates from the posterolateral aspect of the posterior bend of the cavernous carotid artery (C4 segment), it crosses underneath and distorts the abducens nerve, continuing between the abducens and trigeminal nerves. When taking a medial course, the PTA arises from the posteromedial aspect of the posterior bend of the cavernous carotid at the same segment and pierces the clival dura at the dorsum sellae. Cranial nerve displacement or distortion is less likely in this variation. In an analysis of carefully described anatomic studies, the PTA and meningohypophyseal trunk were found arising from either common or separated origins.

CONCLUSION

The most frequent embryological anastomosis between the carotid and vertebrobasilar system is the PTA. Its course and relationship with the cranial nerves may determine its clinical presentation.

The predictive value of intraoperative somatosensory evoked potential monitoring: review of 244 procedures

INTRODUCTION

There is some controversy regarding the value of intraoperative neurophysiological monitoring in predicting postoperative neurological deficits. We discuss our experience with the use of intraoperative somatosensory evoked potentials (SSEPs) during surgery of cranial base tumors.

METHODS

We retrospectively reviewed all of the procedures that had been performed for the resection of cranial base tumors from July 29, 1993, through March 16, 1995. One hundred ninety-three consecutive patients had undergone a total of 244 procedures. SSEP waveforms were classified as follows: Type I, no change; Type II, change that reverts to baseline; Type III, change that does not revert to baseline; and Type IV, complete flattening of the SSEP waveform without improvement. Two patients had no waveforms from the beginning of the case (Type V) and were excluded from further analysis. New immediate postoperative neurological deficits were recorded.

RESULTS

There were 64 male and 129 female patients, with a mean age of 46.6 years. One hundred seventy-seven patients had Type I SSEP waveforms, 13 of whom had postoperative deficits (7%). Fifty-six patients had Type II SSEPs, and nine (16%) of them had postoperative neurological deficits. Six patients had Type III SSEPs, and three had Type IV SSEPs, all of whom (100%) had postoperative deficits. There was a correlation between SSEP type and the results of the postoperative neurological examinations. The positive predictive value is 100%, and the negative predictive value is 90%. Although a change in the waveform that did not revert to baseline (Types III and IV) always predicted a postoperative deficit, a normal waveform did not always rule out postoperative deficits. Pathological abnormality, vessel encasement, vessel narrowing, degree of cavernous sinus involvement, brain stem edema, middle fossa location, final amount of resection, age, and tumor size correlated with a high predictive value of SSEP monitoring on univariate analysis (P < 0.05). None of these variables correlated significantly on multivariate analysis (P > 0.05), although brain stem edema was close (P = 0.0571).

CONCLUSION

Intraoperative SSEPs have a high positive predictive value during surgery for cranial base tumors, but they do not detect all postoperative deficits.

Anatomy of the frontotemporal branch of the facial nerve and indications for interfascial dissection

INTRODUCTION

Many studies have been conducted of the surgical anatomy of the frontotemporal branch of the facial nerve (FTBFN). However, very few have addressed the indications for interfascial dissection. When the zygomatic arch needs to be exposed, the interfascial approach is recommended to protect the FTBFN. With the transbasal or subfrontal approaches, however, when a bicoronal skin incision is used, the need for the interfascial approach is not clear.

METHODS

We studied 10 temporal regions (5 cadaveric heads). We dissected the recognized fascial layers of the temporal region and the FTBFN. We performed a histological study in a sixth specimen.

RESULTS

We observed the following. 1) The galea and the superficial layer of the deep temporal fascia become fused in a curved line from the lateral orbital border 2.8 cm above the zygomatic arch to a point 3 cm posterior to the inferolateral angle of the orbit. 2) After this transitional area of adherence, the subgaleal loose cellular layer is lost and is replaced by a fibrofatty tissue. 3) The FTBFN in its course above the zygomatic arch runs in this tissue layer without being protected by the galea. 4) Over the superolateral angle of the orbital rim, the galea protects FTBFN, and there are no subgaleal adhesions in that area.

CONCLUSION

Ahove the zygomatic arch, the FTBFN is not protected by the galea. During bicoronal approaches, if only the superolateral angle of the orbital rim needs to be exposed and not the zygomatic arch, there is no need to protect the FTBFN using an interfascial approach.

An increase in extracellular glutamate is a sensitive method of detecting ischaemic neuronal damage during cranial base and cerebrovascular surgery. An in vivo microdialysis study

All patients undergoing neurological surgery are at risk for serious complications. Ischaemic damage presenting with hemiparesis or speech difficulties occurs in up to 6% of patients undergoing cerebral bypass procedures and other complicated neurosurgical procedures. Currently available methods for detection of such damage include the use of somatosensory evoked potentials (SSEPs) and electro-encephalography (EEG). Unfortunately, these techniques have false positives and may remain normal in the presence of severe focal neurological deficits. Early detection of potential deficits may prevent or minimize damage through a change in operative or anaesthetic strategy. With the availability of several potential neuroprotective compounds, it is also possible to treat patients at risk of developing ischaemic complications if the individuals are identified early. The excitatory neurotransmitter glutamate is not only a metabolic product, but is also thought to promote ischaemia induced cell injury if released into the extracellular space. It may be a significant parameter for ischaemic brain metabolism. In this report we describe 10 patients who underwent extracranial-intracranial (EC-IC) high flow bypass procedures with routine intra-operative monitoring (IOM) as well as intra-operative in-vivo microdialysis measurement of glutamate. Our aim was to compare intra-operative microdialytic findings and IOM findings with respect to patients' early postoperative clinical courses. Three patients had significant intra-operative glutamate increases indicating ischaemia. Two of these patients awoke with a new neurological deficit (hemiparesis). Routine IOM findings were either normal or showed only transient changes during the time the glutamate levels were high. Our study shows that an increase in extracellular glutamate, as monitored by in-vivo microdialysis, is an excellent early market of neuronal damage. While our glutamate measurements were done off-line, it may be possible to get in future continuous on-line measurements to serve as an early warning system for potential ischaemic damage.

Endodermal cysts of the posterior fossa. Report of three cases and review of the literature

The pathogenesis of endodermal cysts of the posterior fossa is still incompletely understood. The authors reviewed three new cases and those reported in the literature to clarify the clinical, pathological, radiological, and surgical characteristics of these lesions. A total of 49 cases were reviewed. Details on demographic profiles, clinical characteristics, histopathological and radiological features, and surgical methods were collected. These cysts have a predominance in male patients (61%) and can occur at any age (birth-77 years). In patients with posterior fossa endodermal cysts there is a bimodal age distribution and headache is the most frequent complaint. On immunohistopathological examination, endodermal cysts were reactive for epithelial membrane antigen and for keratin immunostains whenever the latter were tested. The cysts were reactive for carcinoembryonic antigen in nine of 11 cases. Endodermal cysts were located anterior to the brainstem in 51% of cases and in the fourth ventricle in 21% of cases. They frequently appeared hypodense on computerized tomography scans, and in five cases, the lesion was missed. The cyst's appearance on magnetic resonance imaging is variable. Resection was complete in 19 cases and partial in 11; marsupialization was achieved in two cases. Three recurrences have been reported. Total excision with preservation of neurological function should be the goal. Cranial base approaches are helpful for surgical access in selected examples of these lesions.

The petrolingual ligament: the anatomy and surgical exposure of the posterolateral landmark of the cavernous sinus

The petrolingual ligament is the posteroinferior attachment of the lateral wall of the cavernous sinus, where the internal carotid artery enters the cavernous sinus. The petrous segment of the internal carotid artery finishes and the cavernous segment begins at the superior margin of this ligament. The ligament is surgically important due to its identification as a landmark for dissection of the internal carotid artery during the approaches to posterolateral intracavernous and extracavernous lesions. It can be well exposed after mobilization of the gasserian ganglion, or after the trigeminal root and ganglion have been split along the junction of V2 and V3 (the transtrigeminal approach). The petrolingual ligament was studied in five cadaveric head specimens from ten sides. The size of the ligament was measured, and its anatomical, clinical and surgical importance is discussed.

Extradural origin of the posteroinferior cerebellar artery: an anatomic study with histological and radiographic correlation

OBJECTIVE

The posteroinferior cerebellar artery (PICA) usually arises from the intradural segment of the vertebral artery (VA). The extradural origin of the PICA is infrequent. Its preoperatory identification is important in surgical strategy during the exposure of the VA.

METHODS

During an anatomic prosection, the VA was exposed at the craniocervical junction in cadaveric adult specimens. The extradural origin of the PICA was encountered bilaterally in one specimen and on one side in a second specimen. An anatomic study with histological and radiographic correlation was performed.

RESULTS

Perforating branches originate from the PICA. They supply the middle and inferior third of the olive and the lateral aspect of the medulla. The PICA has cortical branches that lead to the cerebellum. Injury to the PICA can produce an infarction of these neural structures that can be asymptomatic or cause major neurological deficits. Radiographic results obtained using a lateral projection provided the most reliable delineation of the extradural origin of the PICA. When this artery originates at, or posterior to, the posterior aspect of the occipital condyle, an extradural origin is likely.

CONCLUSION

Bilateral selective vertebral angiography should be performed with special attention to the relationships of PICA origins before any surgical exposure of the VA at the craniocervical junction, unless magnetic resonance angiography provides this information without question. A thorough understanding of the relative dominance of the VAs and PICAs, the location of the PICA origin, and the collateral circulation of the posterior fossa are prerequisites to surgery in this region. The preoperative identification of an extradural PICA is important in planning surgical strategy and in avoiding complications during operations near the foramen magnum.

Combined supra/infratentorial-transsinus approach to large pineal region tumors

OBJECT

The authors sought to confirm that the combined supra/infratentorial-transsinus approach offers a safer means of resecting large pineal region tumors than other approaches currently being used. The aforementioned method provides a wider exposure of the pineal region with less brain retraction than the infratentorial-supracerebellar or the occipital-transtentorial approach alone and is applicable to some large and giant tumors of this area. This combined approach was used in six patients to remove large pineal region tumors including four tentorial meningiomas, one pineocytoma, and one epidermoid cyst.

METHODS

The transverse sinus and tentorium were sectioned after review of preoperative angiographic studies, after taking intraoperative measurements of the venous pressure in the nondominant transverse sinus before and after clipping and while monitoring the somatosensory evoked potentials. The occipital lobe cortex and cerebellum were retracted slightly along the tentorium. Deep veins of the galenic system, the quadrigeminal area, and the tumor were well exposed. Before it was used for tumor resection the approach was studied in five cadaveric head specimens, and the projection of different approaches was compared radiologically. The tumors were removed in a gross-total manner in all patients, and none of the major veins of the galenic system was injured. Resuturing of the nondominant transverse sinus was performed postoperatively in one patient. One of the six patients experienced transient visual loss, and another suffered mild right sixth cranial nerve paresis; however, both recovered in 3 weeks. The wide exposure of the combined approach was also confirmed on radiological and anatomical studies.

CONCLUSIONS

The combined supra/infratentorial-transsinus approach is preferred for the resection of certain large pineal region tumors.