Cerebrospinal fluid signal intensity increase on FLAIR MR images in patients under general anesthesia: the role of supplemental O2.

PURPOSE: To determine whether increased cerebrospinal fluid (CSF) signal intensity is seen on fluid-attenuated inversion recovery (FLAIR) magnetic resonance (MR) images in patients under general anesthesia and to investigate the cause of these changes. MATERIALS AND METHODS: MR images from nine examinations performed in eight patients under general anesthesia were reviewed retrospectively. In phantom experiments, T1 measurements obtained with several inhaled anesthetic agents and propofol dissolved in saline were compared with those obtained with either 100% O2 or room air. To confirm phantom experiment results, a healthy volunteer underwent sequential FLAIR imaging while breathing high-flow 100% O2. RESULTS: Of the nine examinations performed with patients under general anesthesia, eight had resultant images that showed increased CSF signal intensity within the basal cisterns and sulci over the cerebral convexities. Anesthetic phantom measurements showed T1 shortening only when the agent was administered with high concentrations of oxygen. In the healthy volunteer, images obtained before and during administration of 100% O2 demonstrated increased CSF signal intensity after O2 administration; this was identical to the changes observed in patients under anesthesia. CONCLUSION: The paramagnetic effects of supplemental O2 administration result in shortened CSF T1. Radiologists should be aware of this phenomenon to avoid attributing increased CSF signal intensity on FLAIR images to abnormal CSF properties such as hemorrhage or elevated protein content.

Radiologic spectrum of craniocervical distraction injuries.

Injuries to the atlanto-occipital region, which range from complete atlanto-occipital or atlantoaxial dislocation to nondisplaced occipital condyle avulsion fractures, are usually of critical clinical importance. At initial cross-table lateral radiography, measurement of the basion-dens and basion-posterior axial line intervals and comparison with normal measurements may help detect injury. Computed tomography (CT) with sagittal and coronal reformatted images permits optimal detection and evaluation of fracture and luxation. CT findings that may suggest atlanto-occipital injury include joint incongruity, focal hematomas, vertebral artery injury, capsular swelling, and, rarely, fractures through cranial nerve canals. Magnetic resonance (MR) imaging of the cervical spine with fat-suppressed gradient-echo T2-weighted or short-inversion-time inversion recovery sequences can demonstrate increased signal intensity in the atlantoaxial and atlanto-occipital joints, craniocervical ligaments, prevertebral soft tissues, and spinal cord. Axial gradient-echo MR images may be particularly useful in assessing the integrity of the transverse atlantal ligament. All imaging studies should be conducted with special attention to bone integrity and the possibility of soft-tissue injury. Atlanto-occipital injuries are now recognized as potentially survivable, although commonly with substantial morbidity. Swift diagnosis by the trauma radiologist is crucial for ensuring prompt, effective treatment and preventing delayed neurologic deficits in patients who survive such injuries.

Balloon angioplasty for the treatment of vasospasm: results of first 50 cases.

OBJECTIVE: To report the results of the first 50 consecutive patients with vasospasm secondary to subarachnoid hemorrhage treated with balloon angioplasty after failure of medical management. METHODS: Retrospective uncontrolled study of 50 consecutive patients treated with balloon angioplasty between February 1988 and July 1992. Forty-six had objective clinical deterioration despite maximal medical therapy, whereas four were treated on the basis of rapidly accelerating transcranial Doppler velocities and decreased regional blood perfusion detected by technetium-99m-exametazime brain single photon emission computed tomography. All patients had evidence of marked vasospasm demonstrated by angiography. Thirty-two (64%) and 46 (92%) patients underwent angioplasty within 12 and 18 hours, respectively. RESULTS: Of the patients with clinical evidence of vasospasm-induced ischemia, 28 (61%) showed sustained neurological improvement within 72 hours of angioplasty. Three (6%) patients deteriorated within 72 hours after angioplasty, with two (4%) patients dying immediately after angioplasty as a result of vessel rupture and the other patient's Glasgow Coma Scale score decreasing by 2. Two additional patients in poor condition with Hunt and Hess Grade V at the time of angioplasty subsequently died during hospitalization. Two other patients died as a result of unclipped aneurysms that subsequently bled 4 and 12 days after angioplasty, respectively. The improvement demonstrated clinically, angiographically, and by transcranial Doppler after angioplasty was sustained, with only one patient requiring subsequent angioplasty of a previously dilated segment (total, 170 vessel segments dilated). Two patients developed vasospasm in previously undilated segments. CONCLUSION: Timely balloon angioplasty can reverse delayed ischemic deficit caused by vasospasm in patients for whom medical therapy has failed.

Serial MR in gene therapy for recurrent glioblastoma: initial experience and work in progress.

PURPOSE: To describe the MR imaging findings in a pilot study evaluating gene therapy for treatment of patients with recurrent glioblastoma. METHODS: Serial MR examinations were evaluated retrospectively in patients treated with gene therapy that included a retroviral vector containing the herpes simplex virus thymidine kinase gene and intravenous ganciclovir. Images were obtained after tumor resection and after each cycle of treatment, at approximately 40-day intervals. The volume of enhancing tissue was measured on serial MR images. RESULTS: Eleven patients with recurrent glioblastoma were entered into the clinical trial of gene therapy and seven patients completed at least two cycles of treatment. Of these seven, three patients had an early (between 40 and 80 days) increase in the volume of enhancing tissue followed by a decrease or plateau in enhancing tissue volume. A fourth patient had a stable volume of enhancing tissue for 132 days. The remaining three patients had continuous increases in volume of enhancement on all subsequent MR examinations. CONCLUSION: Although animal data show striking tumor regression in response to similar gene therapy, only limited regression was observed among the seven patients we studied. The transient increases in enhancement seen in three of seven patients might reflect an inflammatory response to local injection of the viral vector.

Prognostic significance of type 1 neurofibromatosis (von Recklinghausen Disease) in childhood optic glioma.

Although the association between optic glioma and neurofibromatosis is well recognized, few studies have systematically compared the outcomes of patients with optic gliomas and neurofibromatosis and patients with optic gliomas without neurofibromatosis. In the present study, patients with optic gliomas and Type 1 neurofibromatosis (NF-1) were compared with patients with optic gliomas without NF-1, with respect to survival, time to tumor progression, and tumor location. Forty-four patients with optic gliomas who were evaluated between 1949 and 1991 were studied retrospectively. Sixteen of 44 patients (36%) met the National Institutes of Health criteria for NF-1. The medical records of all patients were examined, and letters of inquiry were sent to every living patient to ascertain current health statuses. Death certificates were obtained to determine causes of death. Follow-up averaged 7.2 years (10.2 yr for patients with NF-1, 5.4 yr for patients without NF-1). The 5- and 10-year survival rates for patients with optic gliomas and NF-1 were 93 and 81%, respectively. For those patients with optic gliomas who did not have NF-1, 5- and 10-year survival rates were 83 and 76%, respectively. Seventeen patients experienced tumor progression (5 with NF-1, 12 without NF-1). A difference was observed in the mean time to tumor progression (first relapse) between the two groups (mean time with NF-1, 8.37 yr; without NF-1, 2.39 yr [P < 0.01]). However, no significant difference in overall survival, as evaluated by a log-rank test of the respective Kaplan-Meier survival curves, was observed between the two groups. A significant difference in distribution of tumor location between the group with NF-1 and the group without NF-1 was also noted (Fisher's exact test, P = 0.0338), although the number of patients evaluated in this series was too small to determine whether this difference in tumor location influenced relapse rate. We conclude that optic gliomas in patients with neurofibromatosis have a different distribution of location as opposed to those in patients without neurofibromatosis, and, for first relapse, the presence of neurofibromatosis is a significant favorable factor.

The effect of extent of resection on recurrence in patients with low grade cerebral hemisphere gliomas.

BACKGROUND: To evaluate the role of radical resection for low grade cerebral hemisphere gliomas, the authors analyzed the preoperative and postoperative radiographic tumor volumes (computed tomography hypodensity, magnetic resonance imaging-T2 signal hyperintensity) in 53 patients. METHODS: Using a previously described method of computerized image analysis, the authors evaluated whether the percent of resection and volume of residual disease, postoperatively, influenced the incidence of recurrence, time to tumor progression, and histology of the recurrent tumor. Survival was not analyzed in this study. RESULTS: No recurrence was detected, regardless of percent of resection and volume of residual disease, in patients with preoperative tumor volumes less than 10 cm2 (mean follow-up, 41.7 months). Patients with tumors measuring 10-30 cm3 had an incidence of recurrence and time to tumor progression of 13.6% and 58 months, respectively, compared with tumors measuring greater than 30 cm3, which had an incidence of recurrence and time to tumor progression of 41.2% and 30 months, respectively (P = 0.016). All patients (n = 13) who underwent a 100% resection had a recurrence-free follow-up period (mean, 54 months). In the remaining patients (n = 40), as the percent of resection decreased, the incidence of recurrence increased along with a shorter time to tumor progression (P = 0.03). Patients with a volume of residual disease of greater than 10 cm3 had a higher incidence of recurrence (46.2%) and a shorter time to tumor progression (30 months) compared with patients with a tumor volume of residual disease of less than 10 cm3 (incidence of recurrence, 14.8% and time to tumor progression, 50 months) (P = 0.002). Forty-six percent of patients with a tumor volume of residual disease of more than 10 cm3 had a recurrence of higher histologic grade, and this was significantly more frequent than patients with a volume of residual disease less than 10 cm3 (3.7%) (P = 0.0009). Age, radiotherapy, and histologic subtype had no influence on recurrence patterns. CONCLUSION: For tumors greater than 10 cm3, the authors' data suggest that a greater percent of resection and a smaller volume of residual disease conveys a significant advantage, that is, terms of incidence of recurrence and the recurrent tumor phenotype, for patients with low grade cerebral hemisphere gliomas, compared with those who have a less aggressive resection or biopsy. While this may also be the case with tumors less than 10 cm3, further follow-up is necessary to determine the effect of surgery on recurrence patterns for this subset of patients.

Differential interactions of dimethyltryptamine (DMT) with 5-HT1A and 5-HT2 receptors.

The interactions of the indolealkylamine N,N-dimethyltryptamine (DMT) with 5-hydroxytryptamine1A (5-HT1A) and 5-HT2 receptors in rat brain were analyzed using radioligand binding techniques and biochemical functional assays. The affinity of DMT for 5-HT1A sites labeled by [3H]-8-hydroxy-2-(di-n-propylamino)tetralin ([3H]-8-OH-DPAT) was decreased in the presence of 10(-4) M GTP, suggesting agonist activity of DMT at this receptor. Adenylate cyclase studies in rat hippocampi showed that DMT inhibited forskolin-stimulated cyclase activity, a 5-HT1A agonist effect. DMT displayed full agonist activity with an EC50 of 4 x 10(-6) M in the cyclase assay. In contrast to the agonist actions of DMT at 5-HT1A receptors, DMT appeared to have antagonistic properties at 5-HT2 receptors. The ability of DMT to compete for [3H]-ketanserin-labeled 5-HT2 receptors was not affected by the presence of 10(-4) M GTP, suggesting antagonist activity of DMT at 5-HT2 receptors. In addition, DMT antagonized 5-HT2-receptor-mediated phosphatidylinositol (PI) turnover in rat cortex at concentrations above 10(-7) M, with 70% of the 5-HT-induced PI response inhibited at 10(-4) M DMT. Micromolar concentrations of DMT produced a slight PI stimulation that was not blocked by the 5-HT2 antagonist ketanserin. These studies suggest that DMT has opposing actions on 5-HT receptor subtypes, displaying agonist activity at 5-HT1A receptors and antagonist activity at 5-HT2 receptors.

5-Hydroxtryptamine1D receptor agonism predicts antimigraine efficacy.

The interactions of four abortive anti-migraine agents and four prophylactic anti-migraine agents with 5-HT1D receptors in bovine brain were analyzed using radioligand binding techniques and adenylate cyclase assays. In bovine caudate, the affinities of abortive anti-migraine agents (i.e. 5-hydroxytryptamine, ergotamine, dihydroergotamine, sumatriptan) for 5-HT1D receptors range from 4.0-34 nM while the affinities of prophylactic anti-migraine agents (i.e. methysergide, amitriptyline, (-)propranolol, verapamil) range from 46-11,000 nM. In adenylate cyclase studies in bovine substantia nigra, all four abortive anti-migraine agents dose-dependently inhibit forskolin-stimulated adenylate cyclase activity, a biochemical effect mediated by 5-HT1D receptors. No agonist effect on cyclase activity is observed with the four prophylactic anti-migraine agents. These data support the hypothesis that abortive anti-migraine agents are 5-HT1D receptor agonists and that this effect may underlie their anti-migraine efficacy.