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Biomedical subjects

M R McLaughlin

Publications and source records attributed to M R McLaughlin.

At least 19 recordsLinked to original sources
PubMed2000

Single-stage anterior-posterior decompression and stabilization for complex cervical spine disorders.

OBJECT: To evaluate the applicability and safety of single-stage combined anterior-posterior decompression and fusion for complex cervical spine disorders, the authors retrospectively reviewed 72 consecutive procedures of this type performed using a uniform technique at a single center. METHODS: The indications for decompression and stabilization included: postlaminectomy kyphosis (15 patients), trauma (19 patients), spondylosis and congenital stenosis (32 patients), and ossification of the posterior longitudinal ligament (six patients). All patients underwent anterior cervical corpectomies in which allograft fibula and plates were placed, with 89% of patients undergoing two- or three-level procedures (range one-four levels). Lateral mass plating with autograft (morselized iliac crest) fusion was performed in all patients while the same anesthetic agent was still in effect. A hard cervical collar was used postoperatively in all patients (mean 13 weeks). All patients were followed for a minimum of 2 years (mean 29 months). Fusion was determined to be successful in all 72 patients (100%). Although the short-term morbidity rate reached 32%, the significant long-term morbidity rate was only 5%. At the 2-year follow-up examination, anterior cervical plate dislodgment was seen in one patient, and 16 of the 516 lateral mass screws implanted were observed to have partially backed out. However, there were no cases of nerve root injury, strut graft extrusion, or anterior plate or screw fracture. There were no clinically significant hardware complications and no patient required repeated operation. CONCLUSIONS: The combined single-stage anterior-posterior decompression, reconstruction, and instrumentation procedure represents a viable option in the treatment of a select group of patients with complex cervical spinal disorders. The technique provides immediate rigid stabilization of the cervical spine, prevents anterior plate failure or strut graft extrusion, and eliminates the need for halo immobilization postoperatively. Furthermore, a higher rate of fusion is achieved with this combined approach than with the anterior approach alone.

Adult↗
PubMed1999

Beneficial effects of the radioprotectant 21-aminosteroid U-74389G in a radiosurgery rat malignant glioma model.

PURPOSE: To evaluate the radioprotectant effects of the 21-aminosteroid U-74389G on the rat C6 glioma model after stereotactic radiosurgery. Because radiosurgery causes both tumor cytotoxicity, as well as regional brain edema, we hypothesized that this drug might exhibit advantageous or deleterious effects on healthy and neoplastic tissue. METHODS: Rats were implanted with 10(6) C6 glioma cells into the right frontal brain and randomized to a Control Group (n = 18), radiosurgery on Day 14 (50% isodose = 35 Gy) (n = 15), or radiosurgery preceded by a single 15 mg/kg intravenous dose of 21-aminosteroid (n = 27). All animals were killed by 90 days and evaluated for survival, tumor size, the presence or absence of regional parenchymal edema, or radiation-induced vasculopathy. RESULTS: After tumor implantation, median survival in the Control Group was 23 days. Significant improvements in median survival were noted after RS alone (median, 31 days; p = 0.02), and RS plus 21-aminosteroid (median, 59 days; p < 0.0001). In the Control Group, mean tumor diameter was 5.4 mm. After RS alone, the mean diameter was 3.2 mm (p = 0.002), and after RS plus 21-aminosteroid, 2.9 mm (p = 0.0002). In the Control Group, the tumor grew as a hypercellular, compact mass. Only 3 of 18 animals had peritumoral edema. In contrast, 7 of 15 animals in the RS group had evidence of edema (p = 0.006), but rats that received 21-aminosteroid showed no increase compared to controls (p = 0.38). Similarly, 6 of 15 animals that had radiosurgery alone showed evidence of vasculopathy (p = 0.005) compared to no animals in the control group and only 2 of 27 aminosteroid-treated animals. CONCLUSIONS: The 21-aminosteroid U-74389G exhibits a radioprotectant effect on normal brain tissue, but does not appear to protect the tumor in an in vivo rat radiosurgery model. We believe that the observed beneficial effects on healthy brain led to significant prolongation of animal survival; perhaps, by limiting the adverse effects of high-dose radiosurgery. This radioprotectant should now be evaluated in randomized clinical trials in patients with malignant brain tumors.

Animals↗
PubMed1999

Management of acute odontoid fractures with single-screw anterior fixation.

OBJECTIVE: Accepted management strategies for odontoid fractures include external immobilization and surgical stabilization using anterior or posterior approaches. Displaced Type II fractures and rostral Type III fractures are at high risk for nonunion. Anterior fixation of odontoid fractures with a single cortical lag screw is a relatively new technique that combines rigid internal stabilization with preservation of intrinsic C1-C2 motion. We retrospectively reviewed our series of 26 consecutive patients who underwent odontoid screw fixation, to further define the safety and efficacy of the technique. METHODS: During a 5-year period, 26 patients presented with acute traumatic Type II odontoid fractures. Ten patients were female and 16 were male, with a mean age of 35 years. All patients underwent anterior odontoid screw fixation by the senior surgeon (RWH), within a mean of 3 days after injury. All patients were postoperatively maintained in external orthoses, for a mean of 7.2 weeks, and were monitored with serial clinical and radiographic examinations. RESULTS: With a mean follow-up period of 30 months, radiographic fusion was documented for 25 of 26 patients (96%). No complications related to the surgical approach were identified, and all patients remained in neurologically stable condition. Two complications (8%) were related to the instrumentation; one patient required external immobilization because of suboptimal screw placement, and one patient required posterior atlantoaxial arthrodesis because of inadequate fracture reduction. CONCLUSION: Single-screw anterior odontoid fixation was associated with a relatively low complication rate and a high fusion rate in this study. We think that this should be the preferred treatment method for acute Type II odontoid fractures.

Adolescent↗
PubMed1999

Microvascular decompression of cranial nerves: lessons learned after 4400 operations.

OBJECT: Microvascular decompression has become an accepted surgical technique for the treatment of trigeminal neuralgia, hemifacial spasm, glossopharyngeal neuralgia, and other cranial nerve rhizopathies. The senior author (P.J.J.) began performing this procedure in 1969 and has performed more than 4400 operations. The purpose of this article is to review some of the nuances of the technical aspects of this procedure. METHODS: A review of 4415 operations shows that numerous modifications to the technique of microvascular decompression have occurred during the last 29 years. Of the 2420 operations performed for trigeminal neuralgia, hemifacial spasm, and glossopharyngeal neuralgia before 1990, cerebellar injury occurred in 21 cases (0.87%), hearing loss in 48 (1.98%), and cerebrospinal fluid (CSF) leakage in 59 cases (2.44%). Of the 1995 operations performed since 1990, cerebellar injuries declined to nine cases (0.45%), hearing loss to 16 (0.8%), and CSF leakage to 37 (1.85% p < 0.01, test for equality of distributions). The authors describe slight variations made to maximize surgical exposure and minimize potential complications in each of the six principal steps of this operation. These modifications have led to decreasing complication rates in recent years. CONCLUSIONS: Using the techniques described in this report, microvascular decompression is an extremely safe and effective treatment for many cranial nerve rhizopathies.

Arteries↗
PubMed1998

Long-term outcomes after radiosurgery for acoustic neuromas.

BACKGROUND: Stereotactic radiosurgery is the principal alternative to microsurgical resection for acoustic neuromas (vestibular schwannomas). The goals of radiosurgery are the long-term prevention of tumor growth, maintenance of neurologic function, and prevention of new neurologic deficits. Although acceptable short-term outcomes have been reported, long-term outcomes have not been well documented. METHODS: We evaluated 162 consecutive patients who underwent radiosurgery for acoustic neuromas between 1987 and 1992 by means of serial imaging tests, clinical evaluations, and a survey between 5 and 10 years after the procedure. The average dose of radiation to the tumor margin was 16 Gy, and the mean transverse diameter of the tumor was 22 mm (range, 8 to 39). Resection had been performed previously in 42 patients (26 percent); in 13 patients the tumor represented a recurrence of disease after a previous total resection. Facial function was normal in 76 percent of the patients before radiosurgery, and 20 percent had useful hearing. RESULTS: The rate of tumor control (with no resection required) was 98 percent. One hundred tumors (62 percent) became smaller, 53 (33 percent) remained unchanged in size, and 9 (6 percent) became slightly larger. Resection was performed in four patients (2 percent) within four years after radiosurgery. Normal facial function was preserved in 79 percent of the patients after five years (House-Brackmann grade 1), and normal trigeminal function was preserved in 73 percent. Fifty-one percent of the patients had no change in hearing ability. No new neurologic deficits appeared more than 28 months after radiosurgery. An outcomes questionnaire was returned by 115 patients (77 percent of the 149 patients still living). Fifty-four of these patients (47 percent) were employed at the time of radiosurgery, and 37 (69 percent) remained so. Radiosurgery was believed to have been successful by all 30 patients who had undergone surgery previously and by 81 (95 percent) of the 85 who had not. Thirty-six of the 115 patients (31 percent) described at least one complication, which resolved in 56 percent of those cases. CONCLUSIONS: Radiosurgery can provide long-term control of acoustic neuromas while preserving neurologic function.

Adult↗
PubMed1998

Current management of pediatric atlantoaxial rotatory subluxation.

STUDY DESIGN: A retrospective clinical review of 20 children seen during a 7-year period who had atlantoaxial rotatory subluxation. OBJECTIVE: To define the effectiveness of imaging and treatment measures and to identify risk factors for recurrence, the series was reviewed to analyze cause, management, and outcome. SUMMARY OF BACKGROUND DATA: Rotatory subluxation of the atlantoaxial complex remains a poorly understood entity. Despite many reports in the literature, there is no consensus about which imaging studies should be used for diagnosis and which patients benefit from collar immobilization, traction, or surgical fusion. METHODS: Between August 1990 and April 1997, 20 children with atlantoaxial rotatory subluxation were treated. Fourteen patients (70%) were girls and six (30%) were boys (mean age, 6.4 years). All patients had torticollis and neck pain with decreased cervical motion for a mean of 11.2 days before diagnosis. Seven patients (35%) had a history of pharyngitis or otitis media, four (20%) had recently undergone head or neck surgery, and four (20%) had sustained a traumatic injury; in five patients (25%), no clear cause was determined. All patients were neurologically intact and underwent plain cervical radiographs and dynamic cervical computed tomography to document atlantoaxial rotatory subluxation. Patients were then treated with a rigid cervical collar and anti-inflammatory agents (n = 5) or with cervical traction followed by immobilization (n = 15). RESULTS: In four of the five patients in collars, reduction occurred spontaneously, whereas the fifth required cervical traction and eventual fusion for recurrence. In the 16 patients treated with traction (median, 1.8 kg), the normal atlantoaxial alignment was restored in 15 patients (94%) within a mean of 4 days. Of the 20 patients treated overall, conservative management failed in 6 (30%), and they required posterior fusion because of recurrence of the atlantoaxial rotatory subluxation or unsuccessful reduction. The major factor predicting the failure of conservative management was the duration of subluxation before initial reduction. Patients with long-standing subluxation were more likely to experience recurrence and require surgery. There were no complications noted. At follow-up, all patients who were treated conservatively remained neurologically intact with a normal atlantoaxial relation. All patients who underwent surgery remained neurologically intact and had radiographic documentation of fusion. CONCLUSION: Optimal management of atlantoaxial rotatory subluxation entails early diagnosis with plain cervical radiographs and dynamic computed tomography. Closed reduction with cervical traction followed by rigid immobilization accomplished reduction in 15 of 16 patients (94%) and was curative in 10 of 16 patients (63%). Although reduction was achieved more rapidly and effectively with traction than with a collar, there may be a role for simple immobilization without reduction in patients with a short duration of symptoms. There does not appear to be a correlation between cause of atlantoaxial rotatory subluxation, age, or sex and the likelihood of recurrence.

Atlanto-Axial Joint↗
PubMed1998

Medulloblastoma and glioblastoma multiforme in a patient with Turcot syndrome: a case report.

BACKGROUND: Turcot syndrome (TS) or the glioma-polyposis syndrome, is a rare, heritable disorder thought by some authors to be a variant of familial adenomatous polyposis (FAP). It is characterized by central nervous system (CNS) neoplasms and gastrointestinal polyposis. METHODS: We present a case report of a patient who developed a medulloblastoma at age 5 years. Ten years later, she developed adenocarcinoma of the colon. Seven months after resection of this Dukes' C2 adenocarcinoma, she presented with a second primary CNS tumor, a glioblastoma multiforme. The patient's colonic adenocarcinoma and glioblastoma were evaluated histologically and cytogenetically. RESULTS: Cytogenetic analysis revealed the presence of chromosomal instability in both tumors. This unusual case of two primary CNS neoplasms in a patient with TS is presented with a review of the literature. CONCLUSIONS: The implications of the cytogenetic analysis are discussed in conjunction with the present knowledge of the molecular biology of TS.

Adenocarcinoma↗
PubMed1998

The origin and evolution of the University of Pittsburgh Department of Neurological Surgery.

Neurological surgery at the University of Pittsburgh began more than 60 years ago with the arrival of Stuart Niles Rowe. During the years, the department has been led by four men, each of whom guided the department into the future in his unique way. These men and many other dedicated physicians, nurses, and staff members have contributed to this organization and created an environment where neurosurgery flourishes. This article describes the development of neurosurgery within the "Steel City" and outlines the origin and growth of the Department of Neurological Surgery at The University of Pittsburgh Medical Center.

Academic Medical Centers↗
PubMed1998

Microvascular decompression of the left lateral medulla oblongata for severe refractory neurogenic hypertension.

OBJECTIVE: To demonstrate that microvascular decompression of the left medulla oblongata is a safe and effective modality for treating elevated blood pressure in patients with severe medically refractory "essential" hypertension (HTN). METHODS: Twelve patients with medically intractable HTN with or without autonomic dysreflexia underwent microvascular decompression of the left rostral ventrolateral medulla oblongata. Causes such as pheochromocytoma, carcinoid syndrome, and renal disease were ruled out before surgery. Indications for surgery included systolic blood pressures greater than 180 mm Hg refractory to three or more medications, severe blood pressure lability, or medically resistant HTN at systolic pressures greater than 160 mm Hg associated with autonomic dysreflexia and/or magnetic resonance images demonstrating left medullary compression. The median age and follow-up duration were 51 years and 4.1 years, respectively. RESULTS: Ten of 12 patients experienced reductions in systolic blood pressure greater than 20 mm Hg. Of these 10 patients, pressure reductions were temporary (6 mo) in two. Seven of eight patients experienced improvement in blood pressure lability and/or autonomic dysreflexia, with five patients showing sustained improvements. CONCLUSION: Microvascular decompression of the left rostral ventrolateral medulla oblongata may be an effective treatment modality for patients suffering from severe HTN and/or autonomic dysreflexia refractory to medical management.

Adult↗
PubMed1998

The prospective natural history of cerebral venous malformations.

OBJECTIVE: A 10-year prospective clinical and magnetic resonance imaging study was undertaken to determine the natural history of venous malformations. We assessed the hemorrhage rate and morbidity associated with venous malformations of the brain. PATIENTS AND METHODS: From 1986 to 1996, 80 patients with venous malformations were referred to the University of Pittsburgh multidisciplinary vascular malformation study group for evaluation. Observation was recommended for all patients. Follow-up clinical information was obtained from patients or their referring physicians through questionnaire or phone conversation. RESULTS: Twenty-two patients presented with neurological signs or symptoms that were thought to be related to the malformations (nine with headaches, four with seizures, three with sensory symptoms, three with motor deficits, two with trigeminal neuralgia, and one with an extrapyramidal disorder). Twenty-three patients presented with headaches that were not considered to be related to the malformations. The retrospective hemorrhage rate (from birth to study entry) was 0.61% (18 bleeds in 2,949 patient-years). Sixteen patients had sustained previous brain hemorrhage in the region of the venous malformations, two of whom had suffered subsequent hemorrhage. During the prospective follow-up period totaling 298 patient-years of clinical observation, two patients suffered hemorrhage (0.68% per year), but only one had a symptomatic bleed (0.34% per year). This patient had not hemorrhaged previously. One of these patients remained asymptomatic, whereas the second developed temporary worsening of facial paresthesias. No patient died as a result of the venous malformations. CONCLUSION: The hemorrhage rate of a patient with venous malformations is similar to the rates presented in previous reports for patients with cavernous malformations without previous symptomatic hemorrhage. We think that hemorrhage in a patient with venous malformations may be related to an underlying but not yet documented cavernous malformation. Because of the low risk for new neurological events, we advocate conservative management. The risks associated with surgical intervention greatly exceed the low risk of morbidity related to venous malformation hemorrhage.

Adolescent↗
PubMed1998

Death from a malignant cerebellopontine angle triton tumor despite stereotactic radiosurgery. Case report.

Malignant vestibular nerve tumors are rare: to date, only three cases have been reported in the literature. The authors report a case of an eighth cranial nerve tumor that progressed 5 years after stereotactic radiosurgery. The patient was a 44-year-old man who underwent stereotactic radiosurgery for a 27-mm cerebellopontine angle tumor that was discovered on investigation of tinnitus and hearing loss. He developed facial weakness after 5 years, and repeated imaging revealed tumor enlargement. Despite complete microsurgical excision, the tumor rapidly recurred locally and subsequently disseminated within the neuraxis. The patient died 1 year after tumor progression was detected. Histopathological analysis revealed a malignant spindle cell neoplasm with frequent mitotic figures. The presence of positive rhabdoid elements on immunohistochemical studies confirmed that it was a triton tumor. The authors review the relevant literature concerning the classification and management of malignant vestibular nerve tumors and discuss the implications of tumor progression after stereotactic radiosurgery.

Adult↗
PubMed1997

Incidence of postlaminectomy kyphosis after Chiari decompression.

STUDY DESIGN: In this retrospective study, a 5-year series of a pediatric population undergoing Chiari decompressions is reviewed. OBJECTIVES: To review the experience with children treated with suboccipital craniectomy and uni- or multilevel cervical laminectomy for Chiari malformation, to determine the incidence of kyphosis and to identify factors predictive of cervical instability. SUMMARY OF BACKGROUND INFORMATION: Upper cervical laminectomy in the pediatric population has a significant risk of postoperative kyphosis. To decrease the incidence of this complication, a concerted effort was made to avoid violation of the facet joint during cervical laminectomy. METHODS: Thirty-two patients (mean age 4.9 years, range 1 day to 18 years) had surgical decompression of Chiari I or II malformations throughout a 5-year period (1989-1994). Radiographs and operative records were analyzed to determine the number of cervical levels decompressed and extent of laminectomy. RESULTS: Mean follow-up was 3.7 years (range 9 months to 7 years). Only one patient had clinical and radiographic evidence of kyphosis and required C2-C3 fusion. Two others had radiographic signs of mild cervical kyphosis but remained asymptomatic. These three patients had two-level complete laminectomies. Twenty-nine patients had no clinical or radiographic evidence of cervical instability. A mean of three cervical levels were decompressed (range 0-4), including partial laminectomies, complete laminectomies, and one osteoplastic laminotomy to drain a lower cervical syrinx. The overall frequency of kyphosis in this series (9%) was substantially lower than in previous reports. Although the number of cervical levels decompressed did not correlate with cervical instability, the one patient with clinical instability had inadvertent violation of the facet joint, suggesting that overaggressive laminectomy may be a critical factor that predisposes patients to postoperative kyphosis. CONCLUSION: Cervical kyphosis after Chiari decompression is a recognized complication of cervical laminectomy in children, the frequency of which may be decreased by careful attention to operative technique.

Adolescent↗
PubMed1997

Anterior thoracic corpectomy without sternotomy: a strategy for malignant disease of the upper thoracic spine.

BACKGROUND: With increasing frequency, spine surgeons are being asked to provide decompression and stabilization in patients with spinal metastases. While no region of the spine is easily treated, the upper thoracic spine is perhaps the least accessible. Traditional approaches to this region involve either thoracotomy or at least limited sternotomy. The authors present an approach to anterior pathology of the upper thoracic spine that obviates the need for sternotomy. METHODS: Within the past two years, two patients with cervicothoracic metastases underwent anterior decompression and fusion without sternotomy. In both patients, the bodies of C7, T1, and T2 were removed. While both patients were prepared and draped for sternotomy, each required a neck dissection only. In both patients, left-sided incisions were made along the leading edge of the sternocleidomastoid. The platysma was divided with the overlying skin. With further dissection, the strap muscles were tagged and divided approximately one centimeter above their sternal attachments. The loose areolar tissue of the superior mediastinum was then bluntly dissected. Along the entire length of the incision, the vascular plane medial to the carotid sheath was developed to facilitate exposure of the anterior spine. A Farley-Thompson retractor system was then employed to retract and protect the superior mediastinal structures. With this exposure, corpectomies were carried out using a high speed drill. Fusion was accomplished through insertion of Steinmann pins into the adjacent intact bodies above and below. This was followed by application of methyl methacrylate. Both patients had immediate postoperative stability with preservation of spinal cord function. Both patients subsequently underwent removal of dorsally located tumor with posterior fusion. CONCLUSIONS: The goal of cancer surgery is to provide for increased functional survival without undue morbidity. The authors feel that when possible, the pain of sternal and clavicular osteotomies should be avoided. The described approach works well in conjunction with a methyl methacrylate/Steinmann pin construct. Because of the intact sternum, the surgeon has a downward angle to access the superior endplate of T3. With adequate soft tissue dissection and retraction as described, however, T3 and perhaps even T4 are easily accessible. While this downward angle would likely not permit an anterior plating procedure, it lends itself nicely to Steinmann pin/methyl methacrylate fusion and spares the patient the pain and potential morbidity of sternotomy.

Breast Neoplasms↗
PubMed1997

Cost advantages of two-level anterior cervical fusion with rigid internal fixation for radiculopathy and degenerative disease.

BACKGROUND: Conventional anterior cervical discectomy with fusion is thought to require postoperative neck immobilization for the promotion of bony fusion. Rigid internal fixation with anterior cervical plates may decrease graft-related complications and provide immediate stability. This stability may obviate postoperative external immobilization. METHODS: This report reviews one surgeon's experience with the use of rigid internal fixation for two-level anterior cervical discectomy and fusion for radiculopathy to promote early mobilization without external bracing. It compares outcomes and costs with a similar population of patients treated with anterior cervical discectomy and fusion who did not undergo rigid internal fixation. We compared patients who underwent two-level allograft anterior cervical discectomy and fusion with or without rigid internal fixation between 1989 and 1994 performed by a single surgeon (FJP) to evaluate the cost advantages and outcome of each procedure. All patients had clinical evidence of cervical radiculopathy unresponsive to medical therapy with magnetic resonance imaging confirmation of the appropriate nerve root impingement. Thirty-nine patients underwent two-level Cloward allograft fusion using Synthes anterior cervical locking plates, 25 underwent identical fusion without plating. Follow-up was 6 months to 4 years (mean, 31 months). RESULTS: Twenty-three of 25 patients in the nonplated group and 36 of 39 patients in the plated group achieved excellent or good outcomes using the Odom criteria. There were six complications (two major and four minor) in each group. Patients who underwent plating returned to light activities (mean, 17 vs. 29 days), driving (28 vs. 57 days), and unrestricted work (66 vs. 136 days) sooner than non-plated patients (p < 0.05, paired t test). No patient with plates was given external immobilization. CONCLUSIONS: Two-level anterior cervical discectomy and fusion with anterior plating for radiculopathy is safe, effective, and seems to provide shorter convalescence compared with conventional anterior cervical discectomy and fusion. Patients returned to unrestricted work sooner, thus reducing short-term disability. Rigid internal fixation may provide cost advantages to patients and insurance disability providers. The authors conclude that the increased cost of treatment for rigid internal fixation is more than offset by the benefits of earlier mobilization.

Bone Plates↗
PubMed1997

Traumatic basilar aneurysm after endoscopic third ventriculostomy: case report.

OBJECTIVE AND IMPORTANCE: This case illustrates that although endoscopic third ventriculostomy for patients with aqueductal stenosis is successful and minimally invasive, it can have severe, life-threatening complications. CLINICAL PRESENTATION: A 3-year-old girl presented with hydrocephalus and aqueductal stenosis. She underwent endoscopic third ventriculostomy with laser fenestration of the third ventricular floor. During the procedure, she developed a severe intraventricular hemorrhage that required prolonged external ventricular drainage and ultimately ventriculoperitoneal shunting. Despite having a negative angiogram after the procedure, she presented 1 month later with a subarachnoid hemorrhage and a traumatic basilar tip aneurysm. INTERVENTION: The patient underwent a right subtemporal approach with clip ligation of the aneurysm and subsequently had a good recovery. CONCLUSION: Hemorrhagic complications after endoscopic third ventriculostomy are rare. The formation of a traumatic basilar tip aneurysm after this procedure has not been reported in the literature. Laser fenestration of the third ventricular floor may increase the risk of this event.

Basilar Artery↗