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Biomedical subjects

A D Firlik

Publications and source records attributed to A D Firlik.

At least 19 recordsLinked to original sources
PubMed2001

Stereotactic radiosurgery for motor cortex region arteriovenous malformations.

OBJECTIVE: The optimal management of arteriovenous malformations (AVMs) in critical brain locations remains controversial. To reduce the risk of an AVM hemorrhage and to enhance the possibility of preserving neurological function, stereotactic radiosurgery was performed in 33 patients with newly diagnosed or residual AVMs located within the motor cortex. The role of embolization also was examined. METHODS: During a 9-year study period, 33 patients with AVMs located primarily in the motor cortex region were treated with stereotactic radiosurgery. These patients were followed up radiographically for a minimum of 36 months, or less if obliteration was documented before 36 months had elapsed. Of the 33 patients, 9 underwent embolization and 1 underwent microsurgery before radiosurgery. Nine patients required a second radiosurgery. The mean AVM target volume was 4.35 cc, and the average radiation dose to the AVM margin was 20 Gy. The median follow-up was 36 months (range, 10-91 mo), and angiographic follow-up of eligible patients was performed 24 or 36 months after radiosurgery. RESULTS: Results were stratified by radiosurgical target volumes: less than 3 cc (Group 1), 3 to 10 cc (Group 2), and greater than 10 cc (Group 3). Overall (including second radiosurgery), 13 (87%) of 15 patients in Group 1 had complete obliteration confirmed by angiography. Nine (64%) of 14 patients in Group 2 exhibited nidus obliteration, and one (25%) of four patients in Group 3 demonstrated obliteration on a magnetic resonance imaging scan. Eight patients (24%) underwent second-stage radiosurgery after angiography revealed a persistent AVM nidus; three patients demonstrated complete obliteration on follow-up angiography. The obliteration rate was higher (87%) for AVMs with less than 3 cc target volume and lower (56%) for those with target volumes larger than 3 cc. One patient experienced worsening neurological function after radiosurgery, and one died from delayed AVM hemorrhage during the latency period. No patient bled after angiographically confirmed AVM obliteration. CONCLUSION: Stereotactic radiosurgery is a successful and safe management option for patients with motor cortex AVMs. The obliteration of AVMs and the attendant low morbidity rates indicate a primary role for radiosurgery in these patients. Staged radiosurgery may be necessary to increase obliteration rates for larger AVMs or for those that are not obliterated after the first procedure.

Adolescent↗
PubMed2000

The neurosurgeon as innovator and entrepreneur.

INNOVATION IS THE driving force behind progress in neurosurgery. Most significant innovations require commercialization to ensure appropriate development and ultimate distribution to patients. There are several key factors that determine whether a particular innovation is likely to be commercially successful. Relationships between academic neurosurgeons and industry are likely to increase in the future. Stronger and more productive relationships between academic neurosurgeons and commercial ventures will provide new opportunities for neurosurgeons to bring innovations to patients more effectively and efficiently. The transfer of innovation from the academic environment to the commercial setting is consistent with the academic mission and can increase funding for basic and clinical neuroscience research.

Commerce↗
PubMed2000

Hyperthermia in the neurosurgical intensive care unit.

OBJECTIVE: In patients with traumatic or ischemic brain injury, hyperthermia is thought to worsen the neurological injury. We studied fever in the neurosurgical intensive care unit (ICU) population using a definition common to surgical practice (rectal temperature >38.5 degrees C). We sought to determine fever incidence, fever duration, and peak temperature and to quantify the use of antipyretic therapy. We also attempted to determine the patient subgroups that are at highest risk for development of fever. METHODS: In a retrospective chart review of a 6-month period, all febrile episodes that occurred in a consecutive series of neurosurgical ICU patients in a university hospital setting were studied. A febrile episode was defined as a rectal temperature of at least 38.5 degrees C; an episode lasted until the temperature fell below this threshold. RESULTS: The 428 patients studied had 946 febrile episodes. Fever occurred in 47% of patients, with a mean of 4.7 febrile episodes in each febrile patient. Fevers occurred in more than 50% of patients who were admitted to the ICU for subarachnoid hemorrhage, a central nervous system infection, seizure control, or hemorrhagic stroke, but they occurred in only 27% of patients admitted for spinal disorders. Fevers occurred in 15% of the patients who stayed in the ICU less than 24 hours, but in 93% of those who remained longer than 14 days. Despite the use of antipyretic therapy for 86% of the febrile episodes, 57% lasted longer than 4 hours and 5% lasted longer than 12 hours. CONCLUSION: Fever is common in critically ill neurosurgical patients, especially those with a prolonged length of stay in the ICU or a cranial disease. If hyperthermia worsens the functional outcome after a primary ischemic or traumatic injury, as has been suggested by several studies of stroke patients, treatment of fever is a clinical issue that requires better management.

Analgesics, Non-Narcotic↗
PubMed2000

The utility of XeCT cerebral blood flow in the management of acute stroke.

The fundamental pathophysiologic event underlying acute ischemic stroke is a reduction in cerebral blood flow (CBF). Over 100 patients with acute stroke have been studied with xenon-enhanced computed tomography (XeCT) during the past three years. A retrospective analysis of these patients has revealed several important observations. XeCT is very sensitive in detecting acute ischemia. The pattern and depth of ischemia can be correlated with the physical examination, CT findings, and angiographic results. Patients with large volumes of severely ischemic tissue are more likely to suffer herniation, hemorrhagic conversion, and death than patients with small volumes of less ischemic tissue. Patients with normal CBF studies are more likely to have their deficits resolved within 24 hours that patients with abnormal CBF maps. It is likely that future prospective studies will better define the precise utility of XeCT in the acute management of cerebral ischemia.

Brain Ischemia↗
PubMed2000

Xenon-enhanced computed tomography in the management of cerebral vasospasm following aneurysmal subarachnoid hemorrhage.

At the University of Pittsburgh, xenon-enhanced computed tomography (XeCT) serves numerous critical roles in the management of patients following aneurysmal subarachnoid hemorrhage (SAH). Routine baseline XeCT studies are obtained within 24 hours of surgery and are used for comparison to later studies. In the setting of a delayed neurological deficit, XeCT is used emergently to distinguish vasospasm from other possible causes and to triage patients to appropriate non-invasive or invasive therapies. In cases of a delayed neurologic deficit without CBF changes, regardless of transcranial doppler results which can be unreliable, XeCT can prevent unnecessary angiography and potentially harmful invasive treatments. For patients demonstrating territorial ischemia diagnostic of symptomatic vasospasm, XeCT is used to monitor the efficacy of both invasive and non-invasive interventions. This paper summarizes the results and significance of clinical studies of XeCT in the management of patients after SAH at our institution.

Humans↗
PubMed1999

Intra-arterial papaverine for the treatment of cerebral vasospasm following aneurysmal subarachnoid hemorrhage.

BACKGROUND: Intra-arterial papaverine (IAP) has been described as a treatment for cerebral vasospasm refractory to standard therapy. METHODS: We report a series of 15 consecutive patients with aneurysmal subarachnoid hemorrhage in which IAP was employed for the treatment of symptomatic vasospasm. All patients exhibited delayed ischemic neurologic deficits, focal cerebral hypoperfusion on stable xenon-enhanced computerized tomography cerebral blood flow studies, and angiographically defined arterial narrowing. Papaverine was infused into 32 arteries on 23 occasions. Six patients required multiple treatments between 1 and 8 days apart. In five instances, IAP was combined with angioplasty. RESULTS: Angiographically defined vasospasm was at least partially reversed immediately following treatment on 18 of 23 occasions. The associated clinical improvement was major on 6 occasions, and either minor or none on 17. Post-treatment cerebral blood flow was assessed on 13 occasions and showed improvement in previously ischemic areas on six occasions and no improvement on seven. Complications were encountered on four occasions. Systemic hypotension and transient brain-stem depression were seen with vertebral artery infusions; a generalized seizure and paradoxical aggravation of vasospasm resulting in hemispheric infarction occurred with internal carotid artery infusions. CONCLUSIONS: Intra-arterial papaverine resulted in reversal of arterial narrowing in the majority of cases (78%). However, this angiographic improvement was associated with cerebral blood flow augmentation in only 46% of cases analyzed, and major clinical improvement in 26%.

Adult↗
PubMed1999

Development of obstructive hydrocephalus with lumboperitoneal shunting following subarachnoid hemorrhage.

Hydrocephalus is a frequent complication of subarachnoid hemorrhage (SAH). The optimum method of treating hydrocephalus in this setting has not been determined. We review our experience with patients developing communicating hydrocephalus secondary to SAH and subsequently treated with lumboperitoneal (LP) shunts. Following hospitalization for the treatment of SAH, patients who developed clinical symptoms and radiologic signs of hydrocephalus were treated with (ventriculoperitoneal) VP or LP shunting. Eighteen patients received an LP shunt, of which seven (28%) developed a non-communicating or obstructive hydrocephalus. These seven patients underwent replacement with a VP shunt and have not had further complications. In the setting of post-SAH communicating hydrocephalus, obstructive hydrocephalus may develop after LP shunt placement. Patients who develop this complication and have their LP shunts converted to VP shunts have a favorable prognosis.

Adult↗
PubMed1999

Factors affecting survival rates for acute vertebrobasilar artery occlusions treated with intra-arterial thrombolytic therapy: a meta-analytical approach.

OBJECTIVE: To determine whether recanalization, coma at presentation, or clot location in the basilar artery influences the relative mortality risk after intra-arterial thrombolytic therapy for acute vertebrobasilar artery occlusions. METHODS: Studies were identified using the MEDLINE database for January 1987 to November 1997. Series were included if they involved 10 or more patients with basilar or vertebrobasilar artery occlusions, used urokinase and/or recombinant tissue plasminogen activator, and were written in English. A fixed-effect meta-analysis approach was used to estimate the risk of death with the aforementioned risk factors. Each study was weighted according to sample size. Relative risks were calculated with 95% confidence intervals. RESULTS: As calculated from peer-reviewed published data, the relative mortality risk for patients for whom recanalization was attempted but not achieved was 2.34 (95% confidence interval, 1.48-3.71; n = 126). Coma at presentation was associated with a relative mortality risk of 1.95 (95% confidence interval, 1.26-2.99; n = 145). Clot locations in the distal one-third of the basilar artery were shown to favor survival, compared with clots located in the proximal and/or middle portions of the basilar artery (relative risk, 0.52; 95% confidence interval, 0.31-0.86; n = 126). CONCLUSION: The combined data suggest that coma at presentation has an independent and adverse effect on survival rates. Complete recanalization, distal clot location, and responsiveness at the time of presentation are statistically significant factors for increased patient survival rates.

Adolescent↗
PubMed1999

Ischemic core and penumbra in human stroke.

BACKGROUND AND PURPOSE: The ischemic core and penumbra have not been thoroughly characterized after acute cerebral thromboembolic occlusion in humans. Differentiation between areas of potentially viable and irreversibly injured ischemic tissue may facilitate assessment and treatment of stroke patients. METHODS: Cerebral blood flow (CBF) was measured in 20 patients with acute middle cerebral artery (MCA) occlusion between 60 and 360 minutes after stroke onset, with the stable xenon computerized tomography (CT) technique. Threshold displays were generated at a single level, and the percentages of hemisphere with CBF </=6, </=10, 11 to 20, 21 to 30, and >30 cm3. 100 g-1. min-1 were measured. The corresponding images on 12 available follow-up CT scans were similarly assessed to determine the area of final infarct. Comparisons were analyzed with a paired Student's t test and Pearson's correlation coefficient. RESULTS: Discrete and confluent areas of CBF </=20 cm3. 100 g-1. min-1 were identified in all patients, ipsilateral to the symptomatic MCA territory. The average area of CBF </=20 cm3. 100 g-1. min-1 within the ipsilateral hemisphere was 66+/-17% compared with 36+/-12% contralaterally (P<0.001). A difference in the extent of low CBF was due primarily to areas with CBF </=10 cm3. 100 g-1. min-1 (48+/-18% versus 16+/-7%, P<0.001). The area of most severe ipsilateral ischemia (</=6 cm3. 100 g-1. min-1) best corresponded to the final area of infarction (37+/-18% versus 40+/-24%; correlation coefficient, 0.866; P<0.01). The acute ischemic core destined to infarction was not surrounded by a widened rim of moderate ischemia because the area with CBF 11 to 20 cm3. 100 g-1. min-1 was similar bilaterally (19+/-4% versus 20+/-7%, P=0.792, thus not significant). CONCLUSIONS: Our study in acute human stroke involving MCA occlusion indicates that a severely ischemic core (CBF </=6 cm3. 100 g-1. min-1), observed between 1 to 6 hours after stroke onset, corresponds to the cerebral tissue destined to infarction. The ischemic penumbra with flow values between 7 and 20 cm3. 100 g-1. min-1 surrounding the ischemic core is very narrow. Therefore, strategies to improve the outcome of many patients with acute MCA occlusion must either include interventions to reverse the ischemic process within a few minutes of onset or increase the cerebral tolerance of ischemia and thereby prolong the potential therapeutic window.

Acute Disease↗
PubMed1999

The peer-review process of the Journal of Neurosurgery.

Peer review is the process by which scientific articles are evaluated and selected for publication. To clarify this procedure for readers and writers, the authors present a detailed description of peer review at the Journal of Neurosurgery (JNS) in the context of other journals. They discuss the unique characteristics of JNS's peer-review process and how it contributes to the quality of the JNS.

Neurosurgery↗
PubMed1999

Advanced CT imaging (functional CT).

Computed tomography can provide anatomic and functional information about the brain. The conventional CT of the brain can be coupled with a cerebral blood flow examination using the stable xenon CT technique and with a CT angiography. Distinct subgroups of patients based on variations in cerebral blood flow and vascular pathology have been demonstrated. The addition of the functional information has become extremely important in triaging and determining the appropriate intervention in the patient with an acute neurological deficit.

Brain↗
PubMed1998

Complications of stereotactic brain surgery.

The authors review iatrogenic complications of stereotactic surgery, including tumor biopsy, cyst or abscess aspiration, movement disorder surgery, and radiosurgery. The expected morbidities and steps taken to reduce complications are also discussed.

Biopsy, Needle↗
PubMed1998

Staged volume radiosurgery followed by microsurgical resection: a novel treatment for giant cerebral arteriovenous malformations: technical case report.

OBJECTIVE AND IMPORTANCE: We describe the successful treatment of symptomatic giant arteriovenous malformations (AVMs) using staged volume radiosurgery followed by microsurgical resection. CLINICAL PRESENTATION: A 57-year-old man presented with Spetzler-Martin Grade 5 AVMs, with persistent headaches and seizures. He had previously undergone eight attempts at AVM embolization and a craniotomy for attempted AVM resection; he had suffered four episodes of brain hemorrhaging but had made a good neurological recovery. INTERVENTION: Because of the persistent symptoms of the patient and his history of hemorrhaging, a treatment plan based on staged radiosurgical treatments of different portions of the AVMs (three sessions, spaced 6 mo apart), followed by delayed microsurgical removal of the much-reduced residual AVMs (3 years later), was undertaken. The patient did not suffer any additional hemorrhaging episodes, his AVMs were completely removed, and he has made a good recovery. CONCLUSION: Staged volume radiosurgery followed by microsurgical resection of the residual AVMs represents a novel treatment strategy for the management of Grade 5 AVMs that might be untreatable by any single treatment method used alone.

Cerebral Angiography↗
PubMed1998

Relation between cerebral blood flow and neurologic deficit resolution in acute ischemic stroke.

BACKGROUND AND OBJECTIVE: Early intervention remains the key to acute ischemic stroke therapy. Many patients whose deficits would later resolve without intervention are exposed to the risks of stroke treatment without benefit. The purpose of this study was to determine whether patients with transient deficits could be distinguished from patients with evolving strokes on the basis of acute cerebral blood flow (CBF) measurements before any clinical distinction could be made. METHODS: Fifty-three patients who presented with acute hemispheric stroke symptoms and who underwent xenon-enhanced CT (XeCT) CBF studies within 8 hours of onset of symptoms (and before any clinical improvement) were studied. RESULTS: Eight patients (15%) had a complete resolution of their symptoms within 24 hours (not related to treatment). All eight patients with deficits that resolved had normal CBF in the symptomatic vascular territories (mean time to XeCT = 3 hours, 51 min). Mean CBF in the regions of interest of the symptomatic vascular territories of patients who had deficits that resolved was 35.4 +/- 8.1 mL x 100 g(-1) x min(-1) compared with 17.3 +/- 9.3 mL x 100 g(-1) x min(-1) of patients with evolving strokes (p = 0.00058). CONCLUSIONS: Patients with ischemic neurologic deficits that will later resolve can be acutely distinguished from patients with evolving cortical infarctions using XeCT CBF measurements. CBF measurements may assist in the triage of patients for acute stroke therapy by selecting patients with a favorable prognosis and may not benefit from therapy but would still be exposed to the potential risks and expense of treatment.

Acute Disease↗
PubMed1998

Relationship between cerebral blood flow and the development of swelling and life-threatening herniation in acute ischemic stroke.

OBJECT: The purpose of this study was to determine whether cerebral blood flow (CBF) measurements in acute stroke could be correlated with the subsequent development of cerebral edema and life-threatening brain herniation. METHODS: Twenty patients with aggressively managed acute middle cerebral artery (MCA) territory strokes who underwent xenon-enhanced computerized tomography (Xe-CT) CBF scanning within 6 hours of onset of symptoms were retrospectively reviewed. The relationship among CBF and follow-up CT evidence of edema and clinical evidence of brain herniation during the 36 to 96 hours following stroke onset was analyzed. Initial CT scans displayed abnormal findings in 11 patients (55%), whereas the Xe-CT CBF scans showed abnormal findings in all patients (100%). The mean CBF in the symptomatic MCA territory was 10.4 ml/100 g/minute in patients who developed severe edema compared with 19 ml/100 g/minute in patients who developed mild edema (p < 0.05). The mean CBF in the symptomatic MCA territory was 8.6 ml/100 g/minute in patients who developed clinical brain herniation compared with 18 ml/100 g/minute in those who did not (p < 0.01). The mean CBF in the symptomatic MCA territory that was 15 ml/100 g/minute or lower was significantly associated with the development of severe edema and herniation (p < 0.05). CONCLUSIONS: Within 6 hours of acute MCA territory stroke, Xe-CT CBF measurements can be used to predict the subsequent development of severe edema and progression to clinical life-threatening brain herniation. Early knowledge of the anatomical and clinical sequelae of stroke in the acute phase may aid in the triage of such patients and alert physicians to the potential need for more aggressive medical or neurosurgical intervention.

Acute Disease↗
PubMed1997

Quantitative cerebral blood flow determinations in acute ischemic stroke. Relationship to computed tomography and angiography.

BACKGROUND AND PURPOSE: The advent of new modalities to treat acute ischemic stroke presents the need for accurate, early diagnosis. In acute ischemic stroke, CT scans are frequently normal or reveal only subtle hypodense changes. This study explored the utility and increased sensitivity of xenonenhanced CT (XeCT) in the diagnosis of acute cerebral ischemia and investigated the relationship between cerebral blood flow (CBF) measurements and early CT and angiographic findings in acute stroke. METHODS: The CT scans, XeCT scans, and angiograms of 20 patients who presented within 6 hours of acute anterior circulation ischemic strokes were analyzed. RESULTS: CT scans were abnormal in 11 (55%) of 20 patients. XeCT scans were abnormal in all 20 (100%) patients, showing regions of interest with CBF < 20 (mL/100 g per minute) in the symptomatic middle cerebral artery (MCA) territories. The mean CBF in the symptomatic MCA territories was significantly lower than than of the asymptomatic MCA territories (P < .0005). In patients with basal ganglia hypodensities, the mean symptomatic MCA territory CBF was significantly lower than that of patients who did not exhibit these early CT findings (P < .05). The mean symptomatic MCA territory CBF in patients with angiographic M1 occlusions was significantly lower than that of patients whose infarcts were caused by MCA branch occlusions (P < .01). CONCLUSIONS: These results show that XeCT is more sensitive than CT in detecting acute strokes and that CBF measurements correlate with early CT and angiographic findings. XeCT may allow for the hyperacute identification of subsets of patients with acute ischemic events who are less likely to benefit and more likely to derive complications from aggressive stroke therapy.

Acute Disease↗