Transcranial and direct cortical stimulation for motor evoked potential monitoring in intracerebral aneurysm surgery.

STUDY AIM: To analyse the parallel use of transcranial electrical stimulation (TES) and direct cortical stimulation (DCS) for eliciting muscle motor evoked potentials (MMEPs) in intracranial aneurysm surgery; to correlate permanent or transient TES- and/or DCS-MMEP changes with surgical maneuvers and clinical motor outcome. PATIENTS AND METHODS: TES and DCS were intraoperatively performed in 108 patients (51.5+/-14.7 years); MMEPs were obtained in muscles belonging to the vascular territory of interest. Monopolar, anodal stimulation was achieved with a train of five stimuli consisting of an individual pulse width of 0.5ms, an interstimulus interval of 4ms, a train repetition rate of 0.5-2Hz, and maximum stimulation intensities up to 200mA (TES) versus 25mA (DCS). RESULTS: In 95/108 (88%) patients, no changes in MMEPs occurred and none of these patients suffered a permanent severe motor deficit. In 14/108 (12%) patients, we observed nine (64%) temporary changes, four (29%) permanent deteriorations and one (7%) permanent MMEP loss. Out of 14 MMEP changes, nine (64%) occurred with TES, compared to 13 (93%) with DCS (Fishers'p=0.165). Parallel changes in TES- and DCS-MMEPs occurred in 8/14 patients (57%), in which case a permanent loss was always followed by a permanent severe motor deficit. Sixty-seven percent of all permanent changes occurred with DCS-MMEPs, compared to 33% with TES-MMEPs (p=0.567, NS). DISCUSSION AND CONCLUSIONS: In aneurysm surgery, provided that close-to-motor-threshold stimulation and the most focal stimulating electrode montage are used, TES- and DCS-MMEPs do not differ in their capacity to detect an impending lesion of the motor cortex or its efferent pathways. TES stimulation can cause significant muscular contraction during surgery, potentially disrupting the operating surgeon. DCS maintains the singular advantage of stimulating a very focal and superficial motor cortex stimulation that does not result in patient movement.

Fatal rebleeding following coil embolization of cerebral aneurysms: the role of long-term systemic anticoagulation.

Embolization of cerebral aneurysms has become a common technique. Its impact on subsequent medical management of the patient is not well known. We report two patients who presented in a poor neurological grade after subarachnoid hemorrhage from posterior communicating artery aneurysms. Both were treated by coil embolization and both developed subclavian vein thrombosis, requiring systemic anticoagulation, initiated 11 and 21 days after embolization, respectively. Both developed a large, fatal intracranial hemorrhage adjacent to the embolized aneurysm in the fourth week of anticoagulation. Systemic anticoagulation of patients who have had a ruptured aneurysm treated by coil embolization may carry a significant risk of rebleeding. Alternate management strategies should be considered in these patients.

History of diagnosis and treatment of aneurysmal subarachnoid hemorrhage.

The pioneers of microsurgery created a new world of neurosurgery through their efforts, including attention to anatomic details, physiologic principles, and technical maneuvers. The impact of microsurgery and the ability to teach it to successive generations of neurosurgeons during the last 25 years are surely the material from which the future history of neurosurgery will be written.

Extracranial aneurysms of the posterior inferior cerebellar artery.

OBJECTIVE: Extracranial aneurysms of the distal posterior inferior cerebellar artery (PICA) are extremely rare and sometimes difficult to diagnose without an adequate angiogram. We present the first series of 3 patients who were evaluated by the senior author and treated surgically. METHODS AND RESULTS: All 3 patients presented with subarachnoid hemorrhage (SAH). Clincial symptoms, included occipital headache, nuchal rigidity, abducens nerve palsy and rapid neurologic deterioration. A unilateral injection of the vertebral artery failed to show the distal contralateral PICA and the aneurysm in 1 patient. All patients underwent aneurysm clipping through a posterior fossa craniectomy and C-1 laminectomy. The aneurysms were located on the tonsillomedullary segment of the PICA, 10-12 mm below the level of the foramen magnum. CONCLUSIONS: It is important to adequately visualize the distal extent of both PICAs or these aneurysms may not be seen. Patients who present with SAH must have the entirety of both vertebral arteries evaluated to avoid missing these aneurysms. The aneurysms were located adjacent to the atlas necessitating an upper cervical laminectomy for adequate surgical exposure. In general, the patients did well postoperatively and none of the patients developed cerebral vasospasm.

Multifactorial analysis of surgical outcome in patients with unruptured middle cerebral artery aneurysms.

OBJECTIVE: To build a predictive tool for assessing both favorable outcome and morbidity in a large series of unruptured aneurysms. SUMMARY BACKGROUND DATA: Some well-known predictors of clinical outcome for patients with ruptured aneurysms are not useful in forecasting outcome for patients with unruptured aneurysms. METHODS: The authors analyzed 93 patients with a total of 101 unruptured middle cerebral aneurysms who underwent surgical clipping. Intraoperative data was reviewed and seven factors that might influence outcome were identified: 1) aneurysm size > 10 mm, 2) presence of a broad neck, 3) presence of intraaneurysmal plaque, 4) clipping of more than one aneurysm during the same surgery, 5) temporary occlusion of the middle cerebral artery, 6) multiple clip applications and repositionings, and 7) use of multiple clips. The entire group of unruptured middle cerebral artery aneurysms was divided into two subgroups on the basis of outcome. Each patient was subsequently analyzed for the Factor Accumulation Index (FAI), the sum of different factors observed in a given patient. RESULTS: The expected outcome subgroup was represented by 86 patients, with a total of 92 aneurysms, and demonstrated the following results: no factors were found in six patients; FAI of 1: 24 patients; FAI of 2: 23 patients; FAI of 3: 12 patients; FAI of 4: 11 patients; FAI of 5: 8 patients; FAI of 6: one patient; FAI of 7: one patient. Seven patients represented the subgroup of unexpected outcomes with total morbidity of 7.5%. There were no deaths. None of the patients in this subgroup accumulated FAI of 0, 1, 2, or 5; otherwise: FAI of 3: two patients; FAI of 4: two patients; FAI of 6: one patient; FAI of 7: two patients. CONCLUSION: It is possible to predict outcome in patients with unruptured middle cerebral artery aneurysm by calculating FAI. The postoperative morbidity increases with an FAI within a range of 3 to 4.

Neurosurgery at the University of Pennsylvania Medical Center.

The University of Pennsylvania Medical School was the nation's first medical school, and its Department of Neurosurgery is one of the nation's oldest. The history of the Department of Neurosurgery at Penn is recounted, beginning with the pioneer surgeon Charles Harrison Frazier. The evolution of the current department, its contemporary status, and its residency program are described.

Orbital drainage from cerebral arteriovenous malformations.

OBJECTIVE: To describe the neuro-ophthalmic findings in patients with orbital drainage from cerebral arteriovenous malformations (AVMs). METHODS: We reviewed the records of 100 consecutive adult patients with cerebral AVMs who presented to our institution during a 4-year period. All patients with orbital drainage were identified, and their neuro-ophthalmic evaluations were reviewed. RESULTS: Three patients (3%) were identified with orbital drainage from a cerebral AVM. The first patient presented with typical chiasmal syndrome (reduced visual acuity, bitemporal hemianopia, and optic atrophy). Magnetic resonance imaging demonstrated a large left temporal and parietal lobe AVM with compression of the chiasm between a large pituitary gland and a markedly enlarged carotid artery. The second patient presented with headaches and postural monocular transient visual obscurations. Examination revealed normal visual function with minimal orbital congestion and asymmetrical disc edema, which was worse in the left eye. Magnetic resonance imaging revealed a large right parietal and occipital lobe AVM without mass effect or hemorrhage and an enlarged left superior ophthalmic vein. The third patient had no visual symptoms and a normal neuro-ophthalmic examination; a right parietal lobe AVM was discovered during an examination for the cause of headaches. CONCLUSION: Orbital drainage from cerebral AVMs is rare. Manifestations may include anterior visual pathway compression, dilated conjunctival veins, orbital congestion, and asymmetrical disc swelling.

Professor M. Gazi Yasargil: an appreciation by a former apprentice.

An appreciation of Professor M. Gazi Yasargil is presented as part of the celebration of his selection as Neurosurgery's Man of the Century. The early history of microneurosurgery and the immense contribution of Yasargil to the development of this methodology are reviewed. The impact of Professor Yasargil on the development of specific operations and instruments is an important aspect of his role in creating this change in neurosurgery. Without trying to predict what history will remember, it is safe to say that every neurosurgical procedure performed today has been affected by Yasargil's efforts. In the broadest way possible, he has dramatically changed for the better how neurosurgery is "thought, taught, and performed."

Spinal cord arteriovenous fistulas involving the conus medullaris: presentation, management, and embryologic considerations.

BACKGROUND: Spinal cord arteriovenous fistulas (SCAVF) are uncommon congenital lesions that usually involve the most caudal aspects of the cord. We present three cases of SCAVF that illustrate the clinical manifestations and possible management options. The characteristic involvement of the conus medullaris and an associated tethered spinal cord in one of our patient suggests that a disorder of secondary neurulation may be involved in the formation of these arteriovenous shunt lesions. METHODS: Review of records and radiologic studies in three consecutive patients with SCAVF's treated at this institution. RESULTS: All three patients had SCAVF involving the lower lumbar spinal cord segments or the conus. One of the conus lesions was associated with tethering of the spinal cord. One small lesion (Type A) was treated surgically, whereas the two larger lesions (Type B) were treated using interventional neuroradiologic techniques. CONCLUSIONS: Both surgical and endovascular method have a role in management of these unusual spinal cord vascular malformations. The association with tethered cord suggests that the propensity for SCAVM to occur in the most caudal portions of the spinal cord may result from failure of secondary neurulation to properly develop the unique and complex vascular anatomy of the region.

Hemangiopericytoma of the third ventricle. Case report.

The authors present the first reported case of a hemangiopericytoma (HPC) occurring in the third ventricle. Most of these lesions are based in the meninges. There is only one other reported case of an intraventricular HPC; in that case the lesion was found in the lateral ventricle. A 40-year-old right-handed man presented with a 3-month history of headaches. Clinical evaluation, including computerized tomography and magnetic resonance imaging studies, revealed a 1-cm enhancing lesion in the third ventricle. Given the findings on the preoperative imaging studies, the lesion was not consistent with some of the more commonly occurring tumors of the third ventricle, namely colloid cysts. A transcortical approach and resection of the lesion was performed without complication. The final pathological findings were consistent with those of an HPC. Hemangiopericytomas rarely occur in the ventricles and may pose a difficult diagnostic dilemma based on their radiographic and gross appearances, as shown in this case. Because of this difficulty, histological confirmation is required to make a definitive diagnosis. These lesions have a propensity to recur and metastasize in the central nervous system and periphery, thus making the goal of treatment a complete surgical resection followed by postoperative radiation therapy in most cases.

Dural arteriovenous fistulas of the craniocervical junction.

Dural arteriovenous fistulas (DAVF) involving the craniocervical junction are uncommon lesions that may result in neurological deficits referable to posterior fossa structures and/or the spinal cord. We report on two patients with craniocervical junction DAVF whose venous drainage involved the cervical spinal cord. Both cases presented with progressive quadriparesis and parenchymal magnetic resonance signal abnormality of the cervical spinal cord. Both patients improved following embolization of the fistulas. AVF of the craniocervical junction are an uncommon, but important cause of treatable neurological deficits referable to this region of the nervous system.

Endovascular stent treatment of cervical internal carotid artery aneurysms with parent vessel preservation.

BACKGROUND: Aneurysms involving the cervical portion of the internal carotid artery (ICA) frequently result from prior trauma or dissection. CASE DESCRIPTIONS: Two patients are reported with cervical internal carotid artery aneurysms. In both cases, disease involving the contralateral ICA precluded safe treatment of the aneurysms by ICA occlusion. Endovascular stents placed across the diseased portion of the artery resulted in thrombosis of the aneurysm with preservation of the parent artery. CONCLUSION: Endovascular stent placement should be considered for treatment of aneurysms involving the cervical ICA when preservation of the parent vessel is necessary.

Dementia resulting from dural arteriovenous fistulas: the pathologic findings of venous hypertensive encephalopathy.

PURPOSE: Dural arteriovenous fistulas (DAVFs) are acquired arteriovenous shunts located within the dura. The highly variable natural history and symptomatology of DAVFs range from subjective bruit to intracranial hemorrhage and are related to the lesion's pattern of venous drainage and its effect on the drainage of adjacent brain. We examined the prevalence and features of DAVFs in patients with progressive dementia or encephalopathy. METHODS: The records and radiologic studies of 40 consecutive patients with DAVFs treated at our institution were reviewed. RESULTS: Five (12.5%) of 40 consecutive patients with DAVFs had encephalopathy or dementia. In each patient, high flow through the arteriovenous shunt combined with venous outflow obstruction caused impairment of cerebral venous drainage. Hemodynamically, the result was widespread venous hypertension causing diffuse ischemia and progressive dysfunction of brain parenchyma. Results of CT or MR imaging revealed abnormalities in each patient, reflecting the impaired parenchymal venous drainage. Pathologic findings in one patient confirmed the mechanism of cerebral dysfunction as venous hypertension. The hemodynamic mechanism and resulting abnormality appeared identical to that seen in progressive chronic myelopathy resulting from a spinal DAVF (Foix-Alajouanine syndrome). Remission of cognitive symptoms occurred in each patient after embolization. CONCLUSION: Venous hypertensive encephalopathy resulting from a DAVF should be considered a potentially reversible cause of vascular dementia in patients with progressive cognitive deficits.

Hypertension, small size, and deep venous drainage are associated with risk of hemorrhagic presentation of cerebral arteriovenous malformations.

OBJECTIVE: To identify clinical and angiographic factors of cerebral arteriovenous malformations (AVMs) associated with hemorrhage to improve the estimation of the risks and help guide management in clinical decision making. METHODS: We conducted a retrospective analysis of 100 consecutive adults who have presented during the past 3 years to our institution with cerebral AVMs. Angiographic and clinical parameters were evaluated using multivariate logistic regression analysis to analyze factors associated with hemorrhagic presentation. RESULTS: The group had a mean age of 37.8 years; 53% were men, 48% presented with intracranial hemorrhage, and 40% presented with seizures. All 10 patients with cerebellar AVMs presented with hemorrhage. The following factors were independently associated with AVM hemorrhage: history of hypertension (P = 0.019; odds ratio [OR] = 5.36), nidal diameter <3 cm (P = 0.023: OR = 4.60), and deep venous drainage (P = 0.009: OR = 5.77). Dural arterial supply (P = 0.008; OR = 0.15) was independently associated with decreased risk of bleed. Location, nidal aneurysms, patient age, and smoking were not associated with increased or decreased bleeding risk. CONCLUSION: In this study, we found small AVM size and deep venous drainage to be positively associated with AVM hemorrhage. Dural supply was associated with a decreased likelihood of hemorrhagic presentation. Hypertension was found to be the only clinical factor positively associated with hemorrhage, a finding not previously reported. Smoking, although associated with increased risk of aneurysmal subarachnoid hemorrhage, was not associated with a higher risk of AVM hemorrhage.

Dural arteriovenous fistulas involving the superior sagittal sinus: acute presentation with intracranial hemorrhage.

BACKGROUND: Intracranial dural arteriovenous fistulas (DAVF) usually drain directly into large dural venous sinuses. Intracranial hemorrhage is therefore unusual with these lesions. Certain subgroups of DAVF may drain into cortical veins causing engorgement, venous hypertension, and hemorrhage. The region of the superior sagittal sinus (SSS), while an unusual location for DAVF, is one in which drainage typically occurs directly into cortical veins. METHODS: We report on three patients with dural arteriovenous malformations of the superior sagittal sinus, all of whom presented with intracranial hemorrhage. Intraparenchymal hemorrhage in two of the cases was surrounded by excessive edema, suggesting the presence of underlying venous hypertension. RESULTS: Interventional treatment of all three of the lesions was accomplished at the time of diagnostic angiography. CONCLUSIONS: SSS DAVF is an uncommon lesion whose presentation is usually with intracranial hemorrhage. Large amounts of edema surrounding an acute hemorrhage may suggest the diagnosis, which usually requires confirmation with angiography. Treatment of SSS DAVF can often be accomplished at the time of diagnostic angiography by embolization using interventional neuroradiologic techniques. When endovascular obliteration of the fistula is not feasible or is incomplete, surgical resection of the DAVF site may be achieved without difficulty.

Brainstem origins of the n18 component of the somatosensory evoked response.

Proposed generator sites for the N18 component of the somatosensory evoked potential (SEP) range in location from the medulla to the thalamus. Additional knowledge regarding the generators of the N18 will be important in interpreting the results of intra-operative monitoring during skull base surgery and providing the surgeon more specific information. The goal of this study was to use both intracranial electrical recording and the effects of acute brainstem ischemia in humans to further define the generators of N18. Monopolar electrodes were used to record SEP (after median nerve stimulation) from the brainstem surface in eight patients undergoing posterior fossa surgical procedures. Recordings were made from various locations, from the cervico-medullary junction to the level of the aqueduct of Sylvius. As the electrode moved rostrally on the brainstem surface, the difference in latencies between the scalp N18 potential and the electrode potential approached zero, suggesting an upper pontine-lower midbrain origin of the N18 potential. These findings were supported by the lack of change in the N18 potentials of ten patients with basilar tip aneurysms who experienced marked changes of their N20/P22 potentials during temporary occlusion of the distal basilar artery.

Unusual aneurysms.

Cerebral aneurysms can present in a variety of special circumstances. Aneurysmal subarachnoid hemorrhage (SAH) can complicate systemic or neoplastic disease, head injuries, arterial dissection, and other cerebrovascular conditions. Aneurysms associated with non-saccular configuration or giant size can make surgical or endovascular intervention difficult if not impossible. This article will review these uncommon aneurysms and their management.

Cigarette smoking-induced increase in the risk of symptomatic vasospasm after aneurysmal subarachnoid hemorrhage.

Vasospasm following aneurysmal subarachnoid hemorrhage (SAH) is correlated with the thickness of blood within the basal cisterns on the initial computerized tomography (CT) scan. To identify additional risk factors for symptomatic vasospasm, the authors performed a prospective analysis of 75 consecutively admitted patients who were treated for aneurysmal SAH. Five patients who died before treatment or were comatose postoperatively were excluded from the study. Of the remaining 70 patients, demographic (age, gender, and race) and clinical (hypertension, diabetes, coronary artery disease, smoking, alcohol abuse, illicit drug use, sentinel headache, Fisher grade, Hunt and Hess grade, World Federation of Neurological Surgeons grade, and ruptured aneurysm location) parameters were evaluated using multivariate logistic regression to determine factors independently associated with cerebral vasospasm. All patients were treated with hypervolemic therapy and administration of nimodipine as prophylaxis for vasospasm. Cerebral vasospasm was suspected in cases that exhibited (by elevation of transcranial Doppler velocities) neurological deterioration 3 to 14 days after SAH with no other explanation and was confirmed either by clinical improvement in response to induced hypertension or by cerebral angiography. The mean age of the patients was 50 years. Sixty-three percent of the patients were women, 74% were white, 64% were cigarette smokers, and 46% were hypertensive. Ten percent of the patients suffered from alcohol abuse, 19% from sentinel bleed, and 49% had a Fisher Grade 3 SAH. Twenty-nine percent of the patients developed symptomatic vasospasm. Multivariate analysis demonstrated that cigarette smoking (p = 0.033; odds ratio 4.7, 95% confidence interval [CI] 2.4-8.9) and Fisher Grade 3, that is, thick subarachnoid clot (p = 0.008; odds ratio 5.1, 95% CI 2-13.1), were independent predictors of symptomatic vasospasm. The authors make the novel observation that cigarette smoking increases the risk of symptomatic vasospasm after aneurysmal SAH, independent of Fisher grade.