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Biomedical subjects

R L Grubb

Publications and source records attributed to R L Grubb.

At least 37 records · Page 2Linked to original sources
PubMed1998

Autoregulatory vasodilation of parenchymal vessels is impaired during cerebral vasospasm.

Impaired CBF autoregulation during vasospasm after aneurysmal subarachnoid hemorrhage (SAH) could reflect impaired capacity of distal vessels to dilate in response to reduced local perfusion pressure or simply indicate that the perfusion pressure distal to large arteries in spasm is so low that vessels are already maximally dilated. Autoregulatory vasodilation can be detected in vivo as an increase in the parenchymal cerebral blood volume (CBV). Regional CBV, CBF, and oxygen extraction fraction in regions with and without angiographic vasospasm obtained from 29 positron emission tomography studies performed after intracranial aneurysm rupture were compared with data from 19 normal volunteers and five patients with carotid artery occlusion. Regional CBF was reduced compared to normal in regions from SAH patients with and without vasospasm as well as with ipsilateral carotid occlusion (P < .0001). Regional oxygen extraction fraction was higher during vasospasm and distal to carotid occlusion than both normal and SAH without vasospasm (P < .0001). Regional CBV was reduced compared to normal in regions with and without spasm, whereas it was increased ipsilateral to carotid occlusion (P < .0001). These findings of reduced parenchymal CBV during vasospasm under similar conditions of tissue hypoxia that produce increased CBV in patients with carotid occlusion provide evidence that parenchymal vessels distal to arteries with angiographic spasm after SAH do not show normal autoregulatory vasodilation.

Adult↗
PubMed1998

Increased oxygen extraction fraction is associated with prior ischemic events in patients with carotid occlusion.

BACKGROUND AND PURPOSE: The purpose of our study was to investigate the relationship between misery perfusion (increased oxygen extraction fraction, OEF) and baseline risk factors in patients with carotid occlusion. METHODS: One-hundred seventeen patients with atherosclerotic carotid occlusion were studied prospectively by clinical evaluation, laboratory testing, and positron emission tomography (PET). PET measurements of cerebral blood flow (CBF), cerebral blood volume (CBV), and OEF were made on enrollment in the study. Increased ipsilateral OEF was identified by comparison with 18 normal control subjects. Twenty-five baseline clinical, epidemiological, and arteriographic risk factors were assessed on study entry. Student t tests, chi(2) tests, and Fisher exact tests with Bonferroni correction were used to assess statistical significance (P<.05). RESULTS: Of 117 patients, 44 had increased OEF distal to the occluded carotid and 73 had normal OEFs. Thirty-nine of the 81 patients with prior ipsilateral ischemic symptoms had high OEFs (42%), whereas only 5 of the 31 asymptomatic patients had high OEFs (16%, P<.001). All of the other baseline risk factors were similar between the two groups of patients. CONCLUSIONS: Investigations of the relationship between hemodynamic factors and stroke risk must take into account the lower frequency of hemodynamic abnormalities in asymptomatic patients.

Adult↗
PubMed1998

Hemodynamic effects of middle cerebral artery stenosis and occlusion.

BACKGROUND AND PURPOSE: Middle cerebral artery (MCA) stenosis and occlusion may cause ischemic symptoms through both hemodynamic and embolic mechanisms. The purpose of this investigation was to determine the hemodynamic effects of these lesions. METHODS: Ten patients with angiographically confirmed symptomatic occlusion (n = 5) or stenosis (n = 5) of the M1 segment of the MCA were studied by clinical examination, arteriography, and positron emission tomography (PET). Arterial supply to the distal MCA territory was classified from a review of the angiogram as being through the stenosis or from pial collaterals from anterior or posterior cerebral arteries. Regional measurements of cerebral blood flow, cerebral blood volume, cerebral rate of oxygen metabolism, oxygen extraction fraction, and ratio of cerebral blood volume/cerebral blood flow (mean vascular transit time, MTT) were obtained using PET. Hemodynamic status was categorized from PET scans as stage 0, normal hemodynamics; stage 1, autoregulatory vasodilatation (increased MTT); or stage 2, increased oxygen extraction fraction. RESULTS: Of five patients with MCA occlusion, three had autoregulatory vasodilatation (stage 1) and two had increased oxygen extraction fraction distal to the lesion (stage 2). The MCA territory was supplied solely by pial collaterals in all five patients. Four of the five patients with focal MCA stenosis had normal hemodynamics (stage 0). One patient had stage 1 hemodynamic status. Blood flow to the MCA territory was through the stenosis in all patients; no pial collaterals were identified. CONCLUSION: The frequency of hemodynamic compromise in patients with MCA occlusion is high. Pial collateralization is not a specific sign of increased oxygen extraction fraction in patients with MCA occlusion.

Adolescent↗
PubMed1997

Cerebral hemodynamic and metabolic changes caused by brain retraction after aneurysmal subarachnoid hemorrhage.

OBJECTIVE: The cerebral hemodynamic and metabolic effects of aneurysmal subarachnoid hemorrhage are complex. To investigate the impact of surgical retraction, we analyzed position emission tomography (PET) studies that measured the regional cerebral metabolic rate for oxygen, regional oxygen extraction fraction, and regional cerebral blood flow in four patients before and after right frontotemporal craniotomies for clipping of ruptured anterior circulation aneurysms. METHODS: Preoperative studies were conducted 1 day before surgery and postoperative studies 6 to 17 days after surgery. No patient had hydrocephalus or intracerebral hematoma. At the time of the second PET study, none of the patients had signs of clinical vasospasm. Regional measurements were obtained from the right ventrolateral frontal and anterior temporal regions corresponding to the area of retraction and compared to the same regions in the opposite hemisphere. To establish a quantitative means to differentiate between hemodynamic and metabolic changes related to arterial vasospasm and those caused by brain retraction, we studied a second group of preoperative patients, who had undergone PET during angiographic and clinical vasospasm. RESULTS: There was a 45% reduction in regional cerebral metabolic rate for oxygen (1.87 +/- 0.22 to 1.04 +/- 0.28 ml 100 g-1 min-1) and 32% reduction in regional oxygen extraction fraction (0.41 +/- 0.04 to 0.28 +/- 0.03) in the region of retraction but no change in the opposite hemisphere (paired t test; P = 0.042 and 0.003, respectively). There was no change in regional cerebral blood flow in any region. Brain retraction produced a focal area of tissue injury at the site of retractor blade placement, as compared to more diffuse vascular territory changes produced by vasospasm. CONCLUSION: This reduction in the cerebral metabolic rate of oxygen and the oxygen extraction fraction indicates a primary reduction in metabolism and uncoupling of flow and metabolism (luxury perfusion). Similar findings of luxury perfusion have been reported after ischemic stroke and traumatic brain injury. Further studies will be necessary to fully understand the clinical and pathophysiological significance of these observations.

Adult↗
PubMed1997

Calcium carbonate apatite deposition in the cervical spine with associated vertebral destruction. Case report.

This 52-year-old woman developed crystal deposition disease involving the cervical vertebrae. She presented with symptomatic spinal cord compression secondary to extensive calcified lesions in the posterior elements of the cervical spine. Surgical decompression with posterior fusion was performed. Histological examination showed hardened deposits of calcium carbonate involving the soft tissue, and dissolution of the vertebral bone trabeculae. There was no inflammatory response to these deposits. One year postoperatively the patient developed severe pulmonary disease associated with the collagen-vascular disorder, scleroderma (calcinosis, Raynaud's phenomenon, esophageal hypomotility, sclerodactyly, and telangiectasia [CREST] syndrome). Calcium carbonate deposition disease represents an unusual clinical entity that is possibly associated with scleroderma or other collagen-vascular diseases, and it is distinct from ligamentum flavum calcification, calcium pyrophosphate deposition disease, and hydroxyapatite deposition disease.

Apatites↗
PubMed1995

Intraoperative digital subtraction angiography: a review of 112 consecutive examinations.

PURPOSE: To examine the effect of intraoperative angiography on neurosurgery and angiographic technical success, safety, and accuracy. METHODS: Angiographic studies, surgical reports, and hospital records were reviewed retrospectively for 112 consecutive procedures in which intraoperative angiography was performed during neurosurgery. The results of conventional postoperative angiograms in 28 of the 112 procedures were also reviewed. A portable digital subtraction angiography unit was used for all patients. Decisions in the operating room were based on review of stored videotaped images. RESULTS: Eighteen studies were obtained in 14 patients after arteriovenous malformation resection. Unsuspected residual nidus was identified and resected in 3 patients. The intraoperative angiogram also altered therapy for 2 patients undergoing staged resections of arteriovenous malformations. Sixty-six studies were performed after aneurysm clipping, with clinically significant changes in surgical therapy made in 5 patients. Of 28 examinations after carotid endarterectomy, 3 led to revision. Two complications of angiography occurred. One led to a permanent neurologic deficit, yielding a complication rate of 1.5% for stroke. Two examinations could not be completed because of technical factors. Two false-negative examinations were identified on postoperative studies. One patient with a normal intraoperative study after carotid endarterectomy thrombosed the repaired internal carotid artery after surgery. CONCLUSIONS: Intraoperative angiography altered surgery in 13 of 112 procedures on 104 patients. This study supports the use of intraoperative angiography in arteriovenous malformation resection and in complex aneurysm surgery, but not for routine carotid endarterectomy.

Angiography, Digital Subtraction↗
PubMed1994

Closure of clival cerebrospinal fluid fistula with biocompatible osteoconductive polymer.

Cerebrospinal fluid fistula into the upper airway often results in meningitis. Closure of fistulas is usually effective using conventional surgical techniques to reconstruct the defect. We report a case of cerebrospinal fluid fistula into the sphenoid sinus and nasopharynx secondary to resection of a clivus chordoma that resisted conventional attempts at closure, including a rectus abdominus free flap. Closure of the fistula was accomplished with the use of a novel alloplast, biocompatible osteoconductive polymer. Follow-up for more than 1 year shows no evidence of rejection, infection, or recurrent cerebrospinal fluid rhinorrhea.

Adult↗
PubMed1992

Computerized electroencephalographic monitoring and selective shunting: influence on intraoperative administration of phenylephrine and myocardial infarction after general anesthesia for carotid endarterectomy.

During carotid endarterectomy (CEA), phenylephrine infusions are commonly used to induce hypertension during carotid clamping in an attempt to increase collateral cerebral blood flow and prevent cerebral ischemia. Although this practice appears to increase the incidence of intraoperative myocardial ischemia during CEA when general anesthesia is employed, whether the limited use of phenylephrine infusions in specific instances of cerebral ischemia, as shown on an electro-encephalogram, results in low perioperative rates of both myocardial infarction (MI) and cerebral infarction remains unclear. We studied 171 CEAs done under general anesthesia performed with selective shunting based on the identification of cerebral ischemia by a two-channel computerized electroencephalographic monitor. The use of a phenylephrine infusion was restricted to the following instances of cerebral ischemia: 1) ischemia associated with hypotension that did not resolve within 2 minutes of decreases in anesthetic administration and treatment with fluid and/or colloid; 2) ischemia poorly or slowly responsive to shunt placement, accompanied by either hypo- or normotension; and 3) ischemia poorly or slowly responsive to removal of the carotid clamp, accompanied by either hypo- or normotension. Two non-Q wave MIs (1.2%) occurred, both nonfatal. There were two cerebral infarctions (1.2%) and three deaths not related to MI (1.8%). Based on these findings, in order to decrease the incidence of both MI and cerebral infarction after general anesthesia for CEA, we recommend the restrictive use of phenylephrine-induced hypertension for specific instances of slowly or poorly reversible cerebral ischemia, as shown on the electroencephalogram.

Adult↗
PubMed1991

Cerebral oxygen metabolism after aneurysmal subarachnoid hemorrhage.

Previous studies of cerebral oxygen metabolism and extraction in patients with subarachnoid hemorrhage (SAH) have yielded conflicting results. We used positron emission tomography (PET) to measure the regional cerebral metabolic rate for oxygen (rCMRO2), oxygen extraction fraction (rOEF), and cerebral blood flow (rCBF) 16 times in 11 patients with aneurysmal SAH. All studies were performed preoperatively; no patient had hydrocephalus or intracerebral hematoma on brain CT. Eight patients with no arteriographic vasospasm who were studied on days 1-4 post-SAH had a significant 25% reduction in global CMRO2 compared to age-matched controls, and no significant change in global OEF, suggesting a primary reduction in CMRO2 caused by SAH. Four patients studied seven times during arteriographic vasospasm had significantly increased rOEF with unchanged CMRO2 in arterial territories affected by arteriographic vasospasm compared to territories without vasospasm, indicative of cerebral ischemia without infarction. No brain regions studied with PET were infarcted on follow-up CT. We conclude that the initial aneurysm rupture produces a primary reduction in CMRO2, and that subsequent vasospasm causes ischemia.

Adult↗
PubMed1990

The perioperative management of the petrous carotid artery in contemporary surgery of the skull base.

Optimal techniques for the preoperative assessment and intraoperative management of the petrous carotid artery remain undefined. While purposeful "avoidance" of this structure may result in partial tumor removal, limited exposure of the petrous carotid artery may lead to inadvertent injury with life-threatening neurovascular sequelae. Twenty-five cases are reported in which surgical manipulation of the petrous carotid artery was necessary to accomplish total tumor removal or gain operative exposure to the skull base. A standard diagnostic radiographic assessment consisted of high-resolution computed tomography, magnetic resonance imaging, and a 4-vessel angiography. Preoperative balloon occlusion of the involved internal carotid artery was performed in four patients. Surgical approaches used in this series were broadly classified as: infratemporal-anterolateral (14), pterional-infratemporal (6), or pterional-anterolateral (5). Intraoperative management of the carotid artery consisted of total decompression in 19 cases, decompression with mobilization in four patients, and resection in two instances. Major neurovascular complications included one stroke and death caused by arterial occlusion, one stroke and death caused by arterial spasm, one stroke caused by brain edema, and one death related to a postoperative carotid hemorrhage. Other nonvascular complications included brain swelling, cranial nerve palsies, dysphagia, ataxia, cerebrospinal fluid fistulae, flap necrosis with wound infection, and pneumocephalus. Invasive and noninvasive methods are outlined for the preoperative assessment of the petrous carotid in cases of advanced skull base disease and intraoperative management options are detailed.

Adolescent↗
PubMed1990

Combined pterional-anterolateral approaches to cranial base tumors.

Advanced tumors of the paranasal sinuses, parotid gland, orbit, parapharynx, and cranial cavity may invade the infratemporal fossa by direct extension or through natural anatomic pathways. The inability to control disease involving this region is reflected by the unacceptably high recurrence rates for both intracranial and extracranial neoplasms. Between 1983 and 1986, a pterional (or subtemporal) approach was combined with such conventional anterolateral procedures as a mandibulopharyngectomy, maxillectomy, orbitectomy, and parotidectomy in 13 patients with advanced skull base lesions. The tumor origin was extracranial in ten cases and intracranial in three patients. Seven of the neoplasms were malignant and six were histologically benign. Complete tumor removal was achieved in all patients. Repair of the ablative defect was achieved with a temporalis myogenous flap in ten patients, and primary closure or distant myocutaneous flaps in the remaining three patients. Postoperative complications included three lateral nasocutaneous fistulae secondary to temporalis myogenous flap necrosis and isolated cases of stroke, cerebral edema, pneumocephalus, and cerebrospinal fluid rhinorrhea. Twelve patients are alive without evidence of disease at a mean interval of 25 months. The remaining patient died from lung metastases 11 months after surgery.

Adolescent↗
PubMed1990

Meningiomas of the lateral skull base: neurotologic manifestations and patterns of recurrence.

The eradication of basicranial meningiomas by traditional surgical techniques is often hindered by neoplastic entanglement with critical neurovascular structures. Apparent, complete tumor resection is frequently followed by extensive, yet clinically silent, recurrent disease with local infiltration of bone, cranial nerves, and brain. Fifty-five cases of sphenoid wing or parasellar meningioma were analyzed to identify clinical manifestations suggestive of early tumor recurrence. Regrowth patterns were then defined according to preoperative radiographic and intraoperative surgical findings. Medial tumor regrowth, involving the cavernous sinus, caused neurapraxia of cranial nerves III, IV, or VI, with associated diplopia or ophthalmoplegia. Inferior (caudal) regrowth of disease involved the infratemporal fossa, pterygomaxillary space, or paranasal sinuses by bony erosion of the middle cranial fossa floor or through natural anatomic foramina and fissures. Such inferior extension was manifested clinically by facial hypesthesia, trismus, and referred otalgia caused by trigeminal nerve involvement and by autophony or serous otitis media related to eustachian tube obstruction. Posterior tumor regrowth occurred along the petrous bone and horizontal carotid canal, resulting in internal auditory meatus erosion and cerebellopontine angle extension with associated tinnitus, hearing loss, unsteadiness, and occasional facial twitching. While the clinical and radiographic evaluations of any patient with a suspected recurrent basicranial meningioma are critical in planning the method and magnitude of reoperation, an understanding of potential recurrence patterns can be used in devising more extensive, combined approaches that may allow complete tumor extirpation at the initial surgical intervention.

Adult↗
PubMed1990

Borderzone hemodynamics in cerebrovascular disease.

To investigate the possible existence of chronic selective hemodynamic impairment in the arterial borderzone regions of the brain, we used positron emission tomography (PET) to measure regional mean vascular transit time (rt, equal to the ratio of regional cerebral blood volume to cerebral blood flow) and regional oxygen extraction fraction (rOEF) in 32 patients with either severe internal carotid artery stenosis or occlusion and 11 normal controls. Twenty-four of the patients had had TIAs or amaurosis fugax from 1 to 60 days before PET; all had normal brain CT. We used a stereotactic localization method to locate the anterior and posterior borderzone regions of the middle cerebral artery (MCA) territory. We then calculated ratios of each borderzone to the ipsilateral MCA territory for both rt and rOEF. There was no significant difference from control ratios in any patient subgroup including those with greater than or equal to 75% stenosis or occlusion, those with or without contralateral greater than or equal to 50% stenosis, or those with abnormal hemodynamics in the MCA territory. We therefore found no evidence for selective borderzone hemodynamic impairment in this group of patients with severe carotid artery disease.

Adult↗
PubMed1990

Management of cerebrospinal fluid otorhinorrhea complicating the retrosigmoid approach to the cerebellopontine angle.

The retrosigmoid approach is currently used in the resection of small acoustic schwannomas or the vestibular nerve in selected patients with recurrent vertigo. Cerebrospinal fluid otorhinorrhea associated with the approach is often due to a failure to completely obliterate exposed air cells of the posteromedial and posterosuperior tracts of the temporal bone. A therapeutic protocol for managing a postoperative spinal fluid leak is outlined on the basis of these anatomic features and the status of the patient's hearing. If serviceable hearing has been preserved, the operative site is explored and incompletely obliterated or exposed cells are sealed with bone wax. If a leak persists, or if hearing is lost with the initial procedure, the mastoid cavity and middle ear cleft are obliterated with abdominal fat and the eustachian tube orifice occluded with Proplast through a facial recess approach.

Cerebellopontine Angle↗
PubMed1990

Control of bleeding in extended skull base surgery.

The resection of skull base neoplasms requires an intimate knowledge of basicranial vascular anatomy. Tumor distortion of surgical landmarks may increase the potential for inadvertent vascular injury with life-threatening intraoperative bleeding or delayed neurologic sequelae. Moreover, massive transfusion therapy may significantly alter the hemostatic mechanism in the perioperative period. On the basis of a review of hemorrhagic complications encountered in 154 consecutive skull base procedures, we describe techniques that are designed to avoid or efficiently control venous and arterial bleeding in extended skull base surgery. The management of complications resulting from blood replacement are reviewed.

Brain↗