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James J. Brennan and Christopher M. Loftus

The study of carotid artery occlusive disease interventions can be divided clinically into the treatment of asymptomatic and symptomatic diseases. Clinical trials that have studied or are currently studying asymptomatic disease include: the Carotid Artery Stenosis with Asymptomatic Narrowing Operation Versus Aspirin study; the Mayo Asymptomatic Carotid Endarterectomy trial; Veterans Administration Cooperative Trial on Asymptomatic Carotid Stenosis; and the Asymptomatic Carotid Atherosclerosis Study. Trials for the treatment of symptomatic disease include: the North American Symptomatic Carotid Endarterectomy Trial; the European Carotid Surgery Trial; and the Veterans Administration Cooperative Study.

In the earliest trials conducted to study asymptomatic disease medical therapy was slightly favored; on close scrutiny these studies were flawed and the findings appeared to be equivocal. The more scientific and appropriate trial, which was ended due to ethical concerns, revealed a clear advantage in patients who underwent surgery for greater than 60% stenosis and when the surgical center demonstrated less than 3% surgical risks.

All trials studying symptomatic disease found a significant decrease in subsequent stroke when surgical intervention was performed. It is now judged that patients with greater than 50% stenosis receive significant benefit.

In this paper the authors review the data from all of these studies. They also review data for special circumstances, such as critical stenosis and patients with symptomatic and asymptomatic Hollenhorst plaques. It is their opinion that these data have allowed surgeons to make much more educated decisions when considering the treatment of patients with carotid artery occlusive disease.

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Eli M. Baron, Christopher M. Loftus, Alexander R. Vaccaro, and Devanand A. Dominique

✓ Although it was originally developed to address degenerative problems, including disc herniations and cervical spondylotic myelopathy in the adult population, the anterior approach to the subaxial spine has proven to be useful for select indications in the pediatric population. The authors review indications for surgery, bone grafting, and instrumentation as they pertain to children.

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Michael G. Muhonen, Scott C. Robertson, Jeffrey S. Gerdes, and Christopher M. Loftus

✓ Serotonin (5-HT) produces constriction of peripheral collateral blood vessels. Using an animal model, the authors tested the hypothesis that 5-HT constricts collateral vessels in the cerebrum. A branch of the middle cerebral artery (MCA) was occluded proximally and cannulated distally in anesthetized dogs. Blood flow to the area at risk for infarction was detected by perfusing the cannulated MCA branch with microsphere-free blood during systemic injection of radioactive microspheres (shadow flow technique). Blood flow to collateral-dependent and normal cerebrum was measured during intravenous infusion of 5-HT (10 and 40 mg/kg/minute). Serotonin produced a dose-related reduction of blood flow to collateral-dependent cerebrum, increased collateral vessel resistance in large cerebral arteries and collateral vessels, and decreased cerebral artery perfusion pressure. In contrast, blood flow to normal cerebrum was not altered because a decrease in small vessel resistance effectively compensated for a decrease in MCA perfusion pressure. These findings indicate that 5-HT produces constriction of collateral vessels in the cerebrum. This response is clearly different from normal small cerebral vessels, which dilate during 5-HT infusion.

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Robert A. Solomon, Christopher M. Loftus, Donald O. Quest, and James W. Correll

✓ In a consecutive series of 1930 carotid endarterectomies there were eight cases of postoperative intracerebral hemorrhage. One of these patients was operated on 2 weeks following cerebral infarction and had severe uncontrollable hypertension after surgery. A second patient had an intraoperative embolus and bled while fully heparinized on the 3rd postoperative day. Only one patient in the series bled into an area of documented cerebral infarction. The remainder of the cases represented hemorrhage into essentially normal brain.

Seven of the eight patients with intracerebral hemorrhage had high-grade internal carotid artery stenosis preoperatively. Although several factors have contributed to the brain hemorrhages in this series of patients, postoperative cerebral hyperperfusion which often follows endarterectomy may have played an important role. Defective cerebrovascular autoregulation in chronically ischemic brain regions may predispose patients to intracerebral hemorrhage after removal of a high-grade stenosis of the internal carotid artery.

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Karl N. Detwiler, Christopher M. Loftus, John C. Godersky, and Arnold H. Menezes

✓ Eleven patients with ankylosing spondylitis and traumatic fracture/dislocation of the spine were identified in a retrospective review of all cases of cervical spine injury treated on the neurosurgical service over a 10-year period. Injury was most often secondary to minor trauma or a motor-vehicle accident, and the level of vertebral involvement was most frequently between C-5 and T-1. Neurological symptoms at presentation ranged from neck pain alone to complete loss of function distal to the level of injury. Initial routine treatment consisted of axial traction for realignment with the minimal weight needed to accomplish this, taking into account the flexion deformity. All patients underwent pluridirectional tomography and/or computerized tomography to delineate the exact sites of injury. Three patients died shortly after admission due to pulmonary complications. The remaining eight patients underwent early posterior stabilization and mobilization in a halo or cervicothoracic brace to achieve fusion. Neurological improvement was achieved in six of these eight cases. The experience described here supports the initiation of axial traction as initial therapy for cervical injuries followed by early surgical stabilization in patients with ankylosing spondylitis. The difficulty of maintaining spinal alignment and the devastating pulmonary problems attendant on conservative management may be obviated by early fusion.

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Nicholas M. Wetjen, P. Charles Garell, Nicholas V. Stence, and Christopher M. Loftus

There have been few investigations of moyamoya disease in the United States and no systematic description of the management practices or outcome from this population. The authors reviewed their experience with this disease to gain a better understanding and improve the treatment of patients with moyamoya disease in the United States. Over a 25-year period 30 patients with moyamoya disease have been treated at the University of Iowa. The cases were divided into patients who had classic, probable, and akin moyamoya disease.

Results indicated that there was a bimodal age distribution and a female predominance of cases. In estimating the referral pattern of our institution, the authors determined that there were greater numbers of epidemiological characteristics than previously anticipated. Patients were treated either surgically or nonsurgically, and different management strategies were utilized in each of the major groups: superficial temporal artery to middle cerebral artery anastomosis and encephalodurosynangiosis in the surgical group; or antiplatelet, anticoagulation, or nonpharmacological intervention in the nonsurgical group.

The authors conclude that there is a higher prevalence and incidence of moyamoya disease in the United States than previously reported and that there are some clinical characteristics of this disease that differ from the cases reported in southeast Asia. These differences may be due to genetic or environmental factors but can also be partly explained by the lower index of suspicion for this disease and, thus, a delay in or complete absence of the correct diagnosis.

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Scott C. Robertson, Nicholas M. Wetjen, Bradley J. Beer, and Christopher M. Loftus

✓ The authors studied the effects of pre- and postischemic administration of dizocilpine maleate (MK-801) on collateral and regional cerebral blood flow (CBF). The ischemic penumbra appears to benefit most from the neuroprotective effects of MK-801. The precise mechanism by which MK-801 provides this neuroprotection remains controversial. Alterations in CBF have been demonstrated with MK-801 administration, but whether the response is an increase or decrease in flow has remained unclear.

A left-sided craniectomy was performed in 20 dogs. A branch of the middle cerebral artery (MCA) was cannulated and collateral blood supply—dependent tissue (CDT) was identified using the “shadow flow” technique. Regional CBF was measured using radiolabeled microspheres. Six dogs received MK-801 (1 mg/kg administered intravenously) before they underwent MCA branch occlusion; the remaining 14 dogs received MK-801 after they underwent MCA occlusion. Cerebral blood flow and vascular pressures were measured 30 and 60 minutes after MK-801 administration. In animals that received MK-801 before MCA occlusion, CBF did not change significantly from baseline values before or after occlusion. In contrast, in animals that received MK-801 after MCA occlusion, CBF was significantly reduced in all regions of the brain, including the CDT. Collateral blood supply—dependent tissue showed a 51.7% reduction in flow, whereas normal CBF was reduced by 29.7%. The MK-801 induced cerebral vasoconstriction in both groups. The neuroprotective effects of MK-801 do not appear to be caused by the augmentation of collateral or global cerebral circulation and, in fact, may block the glutamate-mediated vasodilation that occurs during ischemia.

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Jason A. Heth, Christopher M. Loftus, John G. Piper, and William Yuh

✓ The authors report the case of a patient with transient ischemic attacks who was evaluated by duplex scanning, which demonstrated total carotid artery occlusion. Arteriography revealed what appeared to be a classic “string sign” in the cervical carotid artery, and a standard endarterectomy was planned. At surgery the internal carotid artery was found to be congenitally atretic, accounting for the string appearance of the arteriogram. The etiology, associated anomalies, differential diagnosis, and diagnostic evaluation of such lesions are discussed.

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Christopher M. Loftus, Julius A. Silvidi, Daniel D. Bernstein, Patrick W. Hitchon, and Todd Rosier

✓ Regional cerebral blood flow (rCBF) was measured with radiolabeled microspheres in a canine model of superficial temporal artery-middle cerebral artery (STA-MCA) bypass and acute ischemia. Ischemic zone flows in seven dogs with the bypass first closed and then open showed no significant contribution of bypass flow in the intact vascular system. Following acute proximal occlusion, rCBF was preserved by bypass flow. A significant flow decrease ensued when the bypass was then clipped, confirming the adequacy of the lesion and the protective effect of the bypass. Reopening the bypass after 15 minutes of ischemia restored 76% of the previous flow. This was a significant increase from the global ischemia values, and was not statistically different from preocclusive values. Preocclusion somatosensory evoked potentials (SSEP's) in these animals showed a consistent biphasic wave at 8 to 10 msec after stimulation. This wave, with some decrease in amplitude, was preserved by bypass flow following creation of the arterial lesion. Bypass clipping abolished these ipsilateral SSEP's. Variable return of SSEP's occurred following reopening of the graft, but the recordings never reached preischemic amplitudes. This experimental study shows that, in this model, a prophylactic bypass subjected to immediate demand (with no time for “maturation”) can adequately augment cortical rCBF and is superior to delayed revascularization. The data lend theoretical support to placement of a prophylactic STA-MCA bypass prior to elective carotid artery sacrifice or in surgery where the risk of acute vascular injury is high.

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P. Charles Garell, Roman Mirsky, M. Daniel Noh, Christopher M. Loftus, Patrick W. Hitchon, M. Sean Grady, Ralph G. Dacey, and Matthew A. Howard III

✓ Proper ventricular catheter placements are associated with improved shunt performance. When placing ventricular catheters via the posterior approach, the surgeon must determine an optimum trajectory and then pass a catheter along that trajectory. The incidence of optimal posterior catheter placements is increased by using a posterior catheter guide (PCG); however, errors may still occur because of poor selection of a posterior burr-hole site. In this report an easy-to-use posterior burr-hole localizer (Localizer) is described that defines the optimum burr-hole location based on geometric relationships involving the ear and supraorbital rims.

The basic design principle of the Localizer was formulated and tested by using neuronavigational imaging tools to examine normal adult ventricular anatomy in relation to surface landmarks and by reviewing imaging studies obtained in 50 adult patients with hydrocephalus. Subsequently, the Localizer was used in 28 consecutive patients scheduled to undergo shunt surgery performed by using the PCG. In all cases the catheter entered the ventricle on the first pass and postoperative imaging studies demonstrated successful placement in the ipsilateral anterior horn. There were no catheter-related complications. These early results indicate that the Localizer and PCG devices may be safe and effective when used in combination for placement of posterior ventricular catheters.