Temperature-Dependent Development Modeling of the Phorid Fly Megaselia halterata (Wood) (Diptera: Phoridae)

The effect of temperature on the development of Megaselia halterata (Wood) (Diptera: Phoridae) on A15 variety of button mushroom in the stages of casing and spawn-running was investigated at eight constant temperatures (10, 12.5, 15, 18, 20, 22.5, 25, and 27°C) and developmental rates were modeled as a function of temperature. At 25 and 27°C, an average of 22.2 ± 0.14 and 20.0 ± 0.10 days was needed for M. halterata to complete its development from oviposition to adult eclosion in the stages of casing and spawn-running, respectively. The developmental times of males or females at various constant temperatures were significantly different. Among the linear models, the Ikemoto and Takai linear model in the absence of 12.5 and 25°C showed the best statistical goodness-of-fit and based on this model, the lower developmental threshold and the thermal constant were estimated as 10.4°C and 526.3 degree-days, respectively. Twelve nonlinear temperature-dependent models were examined to find the best model to describe the relationship between temperature and development rate of M. halterata. The Logan 10 nonlinear model provided the best estimation for T _opt and T _max and is strongly recommended for the description of temperature-dependent development of M. halterata.

Validation of multisociety combined task force definitions of abnormal disk morphology

BACKGROUND AND PURPOSE

The multisociety task force descriptively defined abnormal lumbar disk morphology. We aimed to use their definitions to provide a higher level of evidence for the validation of MR imaging in the evaluation of this pathology in patients who have undergone diskectomy by retrospectively classifying their preoperative MRI.

MATERIALS AND METHODS

This retrospective, institutional review board-approved study included 54 of 86 consecutive patients (47 men; average age, 44 years) enrolled in an ongoing prospective trial of surgically treated lumbar disk herniation who had preoperative MRI and documented intraoperative classification of the abnormal disk as protrusion, extrusion, or sequestration by the treating surgeon. Preoperative MRI was classified by 2 blinded radiologists; discrepancies were resolved by a third reader. Statistical analysis of interobserver agreement and imaging compared with surgical findings was performed.

RESULTS

The readers disagreed on only 1 of the 54 cases. The third reader resolved the disagreement. Eight protrusions and 46 extrusions were found on imaging, with no sequestrations. At surgery, there were 13 protrusions and 40 extrusions, with 2 of the extrusions also containing sequestrations; the remaining case had only sequestration. There were 16 discrepancies between imaging and surgery, resulting in 70% agreement.

CONCLUSIONS

This study, which was intended to validate the multisociety combined task force definitions of abnormal disk morphology by using MR imaging with a surgical criterion standard, found 70% agreement between imaging diagnosis and surgical findings. Although reasonable, this finding highlights differences that often exist between intraoperative and preoperative imaging findings of lumbar disk herniation.

Life parameters of Tetranychus urticae (Acari: Tetranychidae) on six common bean cultivars

It is well recognized that the quality of host plants affects the development and survival of twospotted spider mite Tetranychus urticae Koch. The life table parameters of T. urticae, on six cultivars of common bean (Phaseolus vulgaris L.) (chiti Khomein, chiti Ks21189, red Akhtar, red Ks31169, white Pak, and white G11867) were studied at constant laboratory conditions (27 +/- 2 degrees C, 70 +/- 5% RH and 16:8 L:D). Total development times of immature males and females were significantly influenced by bean cultivar. T. urticae laid significantly more eggs per day on red Akhtar (16.16) than on the other cultivars. The mean generation time ranged from 23.37 to 34.82 d, and a significant varietal effect was seen. Percentage of egg hatchability oftwospotted spider mite ranged from 88.25 to 94.20%. The highest intrinsic rate of increase, was recorded on red Akhtar (0.269 +/- 0.031) and the lowest value was obtained on white Pak (0.129 +/- 0.048). In addition, net reproductive rate and finite rate of increase of the twospotted spider mite had the highest value on red Akhtar: 62.38 +/- 1.05 and 1.30 +/- 1.02, respectively. The lowest values of these parameters were recorded on white Pak as 26.11 +/- 1.40 and 1.13 +/- 1.10, respectively. Doubling time varied significantly on different cultivars and the lowest and highest values were obtained on red Akhtar and white Pak, respectively. Our findings revealed that white beans (Pak and G11867) were less suitable cultivars, suggesting that they are more resistant to the twospotted spider mite than the other cultivars.

Clear cell pleomorphic xanthoastrocytoma: case report

Pleomorphic xanthoastrocytoma (PXA) is a well-described astrocytic neoplasm with distinctive clinical and pathological features. Although most patients with PXAs are cured by surgical excision, other patients experience malignant progression and tumor recurrence. We describe a 47-year-old woman with a left temporal lobe PXA that had classic histopathological characteristics as well as extensive clear cell and focal papillary changes, and some anaplastic findings. The patient has now suffered two recurrences after complete resection. The case illustrates a rare, previously undescribed histological variant of PXA, with a prominent clear cell and focal papillary morphology. The study of histologically similar cases is needed to determine whether this variant is always associated with a greater likelihood of recurrence.

Initial experience with intraoperative magnetic resonance imaging in spine surgery

STUDY DESIGN

A case series of 12 patients who underwent spine surgery in an intraoperative magnetic resonance imager (IMRI).

OBJECTIVES

To determine the advantages, limitations, and potential applications to spine surgery of the IMRI.

SUMMARY OF BACKGROUND DATA

Existing stereotactic navigational systems are limited because images are obtained before surgery and are not updated to reflect intraoperative changes. In addition, they necessitate manual registration of fiducial landmarks on the patient's anatomy by the surgeon to the previously obtained image data set, which is a potential source of error. The IMRI eliminates these difficulties by using intraoperative acquisition of MRI images for surgical navigation with the capacity for both image update and image-guided frameless stereotaxy. The IMRI is a novel cryogenless superconducting magnet with an open configuration that allows the surgeon full access to the patient during surgery and intraoperative imaging.

METHODS

T1- and T2-weighted fast spin echo images were obtained for localization, after surgical exposure and after decompression during the course of 12 spine surgeries performed in the IMRI.

RESULTS

The authors performed a series of 12 procedures in the IMRI that included three lumbar discectomies, three anterior cervical discectomies with allograft fusion, three cervical vertebrectomies with allograft fusion, two cervical foraminotomies, and one decompressive cervical laminectomy. The system provided rapid and accurate localization in all cases. The adequacy of decompression by MRI during surgery was confirmed in 10 of 12 cases.

CONCLUSIONS

The IMRI provided accurate and rapid localization in all cases and confirmed the adequacy of decompression in the majority of cases. Future applications of the IMRI to spine surgery may include intraoperative guidance for resection of spine and spinal cord tumors and trajectory planning for spinal endoscopy or screw fixation.

MR imaging of arthritides of the cervical spine

Indications for MR imaging have broadened with the development of multiplanar capability, superb soft tissue contrast, and high sensitivity for detecting pathologic alterations. These developments are especially valuable in the analysis of the spine, where multiple anatomic structures reside, each with varying physical properties. MR imaging is unsurpassed in demonstrating early structural and proliferative changes that occur in inflammatory and related arthritides, and in evaluating complications that can cause significant morbidity, and even death. The role of MR imaging in the evaluation of cervical spinal arthritis continues to evolve, as its role in identifying patients for surgical intervention becomes clearer.

Cerebellopontine angle tumors: role of magnetic resonance imaging

The cerebellopontine (CP) angle is bound anterolaterally by the posterior aspect of the petrous temporal bone and posteromedially by the cerebellum and pons. It contains important vascular structures and cranial nerves and is subject to a certain gamut of lesions, notably tumors with interesting radiological manifestations. Radiological investigation of these lesions has seen significant improvement in recent decades. Magnetic resonance is the imaging modality of choice for lesions of the CP angle and internal auditory canal. Lesions of the CP angles usually are divided into those native to the angle (vestibular schwannoma, meningioma, epidermoid, arachnoid cyst, metastases, lipoma, etc.) and those extending to the angle from adjacent structures (gliomas, ependymomas, choroid plexus papillomas, vascular malformations). Vestibular schwannomas are by far the most important lesion of the CP angle.

Idiopathic pinealitis. Case report

This 63-year-old man presented with complaints of "having a feeling of falling backward" over a 3-month period. Results of his general physical examination, laboratory studies, and neurological examination were unremarkable. A magnetic resonance image revealed a 1.8 x 1.4 x 1.2-cm enhancing mass in the posterior third ventricle just above the corpora quadrigemina. The pineal gland was found to be diffusely enlarged at operation and separable from the posterior thalamus and was totally resected. The patient had an uneventful postoperative course but continues to be somewhat confused. The lesion consisted of a remarkable chronic inflammatory cell infiltrate permeating the pineal lobules and was composed of T and B lymphocytes, macrophages, eosinophils, and mast cells. Immunoperoxidase studies did not demonstrate Langerhans cells, and a search for microorganisms was unrevealing. There was no evidence of neoplasia; results of immunostaining for germ cell markers and other tumor-associated antigens were negative.

Intraoperative MR imaging guidance for intracranial neurosurgery: experience with the first 200 cases

PURPOSE

To review preliminary experience with an open-bore magnetic resonance (MR) imaging system for guidance in intracranial surgical procedures.

MATERIALS AND METHODS

A vertically oriented, open-configuration 0.5-T MR imager was housed in a sterile procedure room. Receive and transmit surface coils were wrapped around the patient's head, and images were displayed on monitors mounted in the gap of the magnet and visible to surgeons. During 2 years, 200 intracranial procedures were performed.

RESULTS

There were 111 craniotomies, 68 biopsies, 12 intracranial cyst evaluations, four subdural drainages, and five transsphenoidal pituitary resections performed with the intraoperative MR unit. In each case, the intraoperative MR system yielded satisfactory results by allowing the radiologist to guide surgeons toward lesions and to assist in treatment. In two patients, hyperacute hemorrhage was noted and removed. The duration of the procedure and the complication rate were similar to those of conventional surgery.

CONCLUSION

Intraoperative MR imaging was successfully implemented for a variety of intracranial procedures and provided continuous visual feedback, which can be helpful in all stages of neurosurgical intervention without affecting the duration of the procedure or the incidence of complications. This system has potential advantages over conventional frame-based and frameless stereotactic procedures with respect to the safety and effectiveness of neurosurgical interventions.

Parasagittal solitary fibrous tumor of the meninges. Case report and review of the literature

The clinical, radiologic and pathologic features of a case of parasagittal solitary fibrous tumor of the meninges are reported. The patient was a 44 year-old male who presented with a complex partial seizure and a history of headaches and confusion. Radiological studies showed a large extra-axial dural-based mass in the right parietal region, predominantly isointense with gray matter and hypointense with respect to white matter on T1-weighted images, and hypointense with respect to gray matter on T2-weighted images. At surgery, the mass was very vascular, quite firm and very adherent to the convexity. Histologically the tumor was composed of spindle-shaped cells growing in fascicles within a collagenous matrix. Solitary fibrous tumor of the meninges is a newly described entity, which should be kept in mind in the clinical and radiological differential diagnosis of extra-axial brain tumors.

Functional MRI of the lumbar spine in erect position in a superconducting open-configuration MR system: preliminary results

The purpose of this study was to determine the feasibility of obtaining, and findings in, functional MRI of the lumbar spine in an erect position and with flexion and extension. Thirty subjects (including 5 volunteers) were imaged in a sitting position and while performing flexion and extension. The alternations in posterior disk margin, size of neural foramina, and central canal were evaluated. In addition, routine supine imaging was accomplished in 15 of these subjects. The foraminal size and posterior disk margins did not change appreciably from supine to upright position. With extension, there was an increased disk bulge in 27% of disks (40% of those with desiccation). Central canal size (50%) and foraminal size (27%) decreased with extension, especially at levels with disk desiccation. Images obtained with our open-configuration MR unit were diagnostically adequate, although of inferior quality compared with those obtained with a conventional unit. Our preliminary results show the feasibility of obtaining diagnostic images of the erect lumbar spine with flexion and extension. The results are in agreement with those obtained with cadaveric studies. The utility of this method in diagnostic imaging of patients with low back pain remains to be determined.

Neurosurgical considerations in supratentorial low-grade gliomas: experience with 175 patients

The authors reviewed 175 low-grade hemispheric gliomas surgically treated by one surgeon (P.B.) between 1987 and 1996: 74 astrocytomas (42%), 35 oligodendrogliomas (20%), 52 mixed gliomas (30%), 12 gangliogliomas (7%), and two ependymomas (1%). Patient age ranged from 7.5 to 81.9 years (mean 39.2 years); 84 patients (48%) were males and 91 (52%) females. Postsurgical follow-up review ranged from 0.1 to 225.2 months (mean 36.2 months, median 24.9 months). Either T2-weighted or contrast-enhanced T1-weighted magnetic resonance (MR) images were used to evaluate the percentage of resection achieved and volume of residual disease postoperatively. The majority of patients (55%) had seizures as the presenting symptom, and 45% experienced preoperative symptoms for more than 12 months. Tumor enhancement was present in 21% of cases. In 66% of surgical procedures at least one of the following technical adjuncts was used: monitored local anesthesia, real-time MR imaging, stereotactic guidance with computerized tomography, three dimensional reconstruction, cortical mapping with cortical stimulation, somatosensory or visual evoked potential recording, corticography, or intraoperative ultrasound. Intraoperative MR imaging was used for 40 (22.9%) of the craniotomies and nine (5.14%) biopsies. There were no surgery-related deaths. Complications appeared in 6% of the patients. Progression to a higher-grade tumor occurred in 9.2% of patients within the 3-year follow-up period.

Clinical and neuroradiographic manifestations of eastern equine encephalitis

BACKGROUND

Eastern equine encephalitis occurs principally along the east and Gulf coasts of the United States. Recognition of the neuroradiographic manifestations of eastern equine encephalitis could hasten the diagnosis of the illness and speed the response to index cases.

METHODS

We reviewed all cases of eastern equine encephalitis reported in the United States between 1988 and 1994. The records of 36 patients were studied, along with 57 computed tomographic (CT) scans and 23 magnetic resonance imaging (MRI) scans from 33 patients.

RESULTS

The mortality rate was 36 percent, and 35 percent of the survivors were moderately or severely disabled. Neuroradiographic abnormalities were common and best visualized by MRI. Among the patients for whom MRI scans were available, the results were abnormal for all eight comatose patients as well as for all three noncomatose patients who subsequently became comatose. The CT results were abnormal in 21 of 32 patients with readable scans. The abnormal findings included focal lesions in the basal ganglia (found in 71 percent of patients on MRI, and in 56 percent on CT), thalami (found in 71 percent on MRI and in 25 percent on CT), and brain stem (found in 43 percent on MRI and in 9 percent on CT). Cortical lesions, meningeal enhancement, and periventricular white-matter changes were less common. The presence of large radiographic lesions did not predict a poor outcome, but either high cerebrospinal fluid white-cell counts or severe hyponatremia did.

CONCLUSIONS

Eastern equine encephalitis produces focal radiographic signs. The characteristic early involvement of the basal ganglia and thalami distinguish this illness from herpes simplex encephalitis. MRI is a sensitive technique to identify the characteristic early radiographic manifestations of this viral encephalitis.

Correlation of vascular endothelial growth factor messenger RNA expression with peritumoral vasogenic cerebral edema in meningiomas

Intracranial meningiomas are often complicated by peritumoral vasogenic cerebral edema, which appears to result from increased microvascular permeability and extravasation of proteinaceous and plasma fluid into the adjacent peritumoral space. The source of such edema has long been mysterious. The contents of this paper support the concept that vascular endothelial growth factor (VEGF) production plays a significant role in edema formation. Vascular endothelial growth factor messenger RNA expression has been found in a wide range of intracranial neoplasms, including malignant gliomas, metastatic melanomas, meningiomas, and other benign tumors. Several studies have confirmed the importance of VEGF in tumorigenesis, neovascularization, and edema production. This study tests the hypothesis that the presence of peritumoral edema in meningiomas is positively correlated with increased expression of VEGF mRNA. To investigate this hypothesis, 31 meningioma specimens were subjected to Northern blot analysis, hybridization with a complementary DNA VEGF probe, and laser densitometry to determine the relative levels of VEGF mRNA expression. Magnetic resonance imaging was then used in a double-blind fashion to correlate the neuropathological tissue samples with the presence of preoperative peritumoral edema. Of 31 patients studied, 14 exhibited no edema and 17 exhibited some level of peritumoral fluid accumulation. There was a marked increase in VEGF expression in patients with edema (p = 0.0004, Wilcoxon-Mann-Whitney rank-sum test). Meningiomas with peritumoral edema exhibited 3.4 times the level of VEGF mRNA as those without edema. These data demonstrate a strong link between VEGF mRNA expression and peritumoral edema and indicate that VEGF expression is an important factor in the etiology of edema around meningiomas.

Mesencephalic clefts with associated eye movement disorders

OBJECTIVE

To describe two patients with mesencephalic midline clefts and associated eye movement disorders.

DESIGN

Case reports.

RESULTS

The first patient developed bilateral internuclear ophthalmoplegia with exotropia, reduced convergence, right ptosis, right fourth-nerve palsy, and right elevator palsy several years after meningitis with hydrocephalus. The second patient had bilateral internuclear ophthalmoplegia with exotropia, reduced convergence, bilateral ptosis, limited upward gaze, and right hypertropia since childhood. In both patients, magnetic resonance imaging showed a midline cleft extending from the cerebral aqueduct into the midbrain.

CONCLUSION

It is likely that the clefts affected the oculomotor nuclei and medial longitudinal fasciculi, accounting for the eye movement disorders.

Anatomic-radiologic basis of Lhermitte's sign in multiple sclerosis

OBJECTIVE

To test the presumption that Lhermitte's sign in multiple sclerosis is the result of a lesion in the cervical spinal cord.

DESIGN

The radiologic files of 887 patients with multiple sclerosis were reviewed. A detailed questionnaire regarding Lhermitte's sign was sent to 75 patients who had undergone magnetic resonance imaging of the brain and cervical spinal cord. Of the 64 patients who responded, 55 patients who had complete magnetic resonance imaging files were studied. The cases of two illustrative patients are presented.

RESULTS

A strong association between Lhermitte's sign and abnormalities of the cervical spinal cord seen on magnetic resonance imaging was noted. Most of the abnormalities were in the posterior part of the cervical spinal cord.

CONCLUSIONS

The findings confirm the presumption that a lesion in the posterior columns of the cervical spinal cord is the cause of Lhermitte's sign in multiple sclerosis.

Lacunar thalamic stroke with pure cerebellar and proprioceptive deficits

Case reports of two patients with cerebellar ataxia and proprioceptive sensory loss are presented. MRI of the brain revealed lesions of the ventroposterior part of the thalamus. These patients illustrate clinically the anatomical independence of cerebellar and sensory pathways in the thalamus. We suggest that the ataxic deficit is caused by interruption of cerebellar outflow pathways in the thalamus and not secondary to sensory deafferentation.

Ependymoma of filum terminale: metrizamide-enhanced CT evaluation

Two cases of surgically proven myxopapillary ependymomas of filum terminale are reported. In both, myelography and metrizamide-enhanced computed tomographic (CT) scans were performed. An intramedullary tumor in the lower thoracic spine, soft-tissue masses in the neural foramina and enlarged bony spinal canal in the lower thoracic and upper lumbar spine were noted in one case and, in the other, an intradural extramedullary tumor at T12-L1 level. Both patients had normal cranial CT scans, and both presented with similar symptoms--low back pain and weakness and paresthesia of leg or legs for up to 3 years' duration. Myelography and metrizamide-enhanced CT scans were performed in order to evaluate disc disease in one patient and spinal stenosis in the other. Ependymoma was an incidental finding, which was then removed by surgical resection. Pathology confirmed the diagnosis.

Thoracic spinal metastasis from unexpected cerebellar medulloblastoma: the value of MRI

A 28-year-old male was found on CT metrizamide myelography to have an intradural extramedullary tumor at the T8-T9 level. This was seen to compress the spinal cord, and on surgery it was proven to be medulloblastoma. Cranial CT scans disclosed only mild hydrocephalus and minimal anterior displacement of the inferior fourth ventricle on the right. However, magnetic resonance imaging (MRI) which was performed after the spinal surgery demonstrated an inferior cerebellar vermian tumor.

Intradural herniation of thoracic disc: CT metrizamide myelography

A case of intradural herniation of a thoracic (T12-L1) intervertebral disc is reported. On metrizamide myelography, this lesion resembled an intradural extramedullary tumor with an extradural component. A computed tomographic (CT) scan taken immediately after the myelogram, showed gas in the spinal canal and in the intervertebral disc. In addition, it showed a high-density mass located in the ventral epidural space and also intradurally. The density of this soft-tissue mass was identical to that of the intervertebral disc. CT provided very important information regarding the precise location and probable etiology of the lesion, and the success of surgery.

Prolactinomas. Clinical presentation, radiologic assessment, and therapeutic options

Of the pituitary tumors, the prolactinoma is the most common, characteristically causing amenorrhea/galactorrhea in women and symptoms secondary to mass effect in men. Direct coronal CT scanning with rapid infusion contrast enhancement is now considered the most sensitive and specific method for evaluating the pituitary. Normally the gland is either homogeneous or heterogeneous in a repetitive fashion, and measures up to 9-10 mm in height. Adenomas typically are hypodense lesions in the anterior lobe associated with mass effect--superior surface convexity, gland enlargement, bony erosion, infundibulum displacement, or vascular "tuft" shift. High field superconductive MRI is thought to be superior to CT for evaluation of macroadenomas and may soon surpass CT in the evaluation of microadenomas. Treatment remains controversial. Perhaps surgery is the best alternative for women 15 to 30 years of age with microadenomas producing prolactin less than 100 ng/ml. Patients who are either beyond the child-bearing years, present with tumors greater than 10 mm in diameter, or have microadenomas producing prolactin greater than 100 ng/ml may be better served by medical therapy using bromocriptine or pergolide mesylate.

Computed tomography of aneurysmal bone cyst of the L1 vertebral body

A 31-year-old woman with an aneurysmal bone cyst of the L1 vertebral body proved by biopsy and studied by plain lumbar spine roentgenography, radionuclide studies, myelography, and CT is presented. The unusual location of involvement of the vertebral body alone and the difficulty in differential diagnosis between aneurysmal bone cyst and benign giant cell tumor are discussed.

Spinal cord or nerve root compression in patients with malignant disease: CT evaluation

Fifty patients with malignant disease were seen on an emergency basis because they showed clinical signs of spinal cord or nerve root compression. All were studied with high resolution computed tomography (CT) of the spine; in addition, myelography was performed on 10 of the patients. We found that 48 cases (96%) could be accurately diagnosed by CT alone. In two cases (4%) CT was inconclusive, but myelography was diagnostic; one proved to be cerebrospinal fluid seeding with nerve root involvement, and the other showed conus medullaris involvement. In the remaining eight cases studied by both techniques, correlation between CT and myelography was very good.

Cervical chordoma presenting with intervertebral foramen enlargement mimicking neurofibroma: CT findings

A cervical chordoma, confirmed at surgery, presented on plain spine films as a focal enlargement of the intervertebral foramen and mimicked the characteristic appearance of cervical neurofibroma. Computed tomography (CT) of the cervical spine was obtained immediately following metrizamide myelography; it demonstrated a soft-tissue mass in the enlarged intervertebral foramen that extended posteriorly to compress the spinal cord and anteriorly to compress the hypopharynx. The mass was sharply demarcated, inhomogeneous, and low in attenuation; CT density measured between those of cerebrospinal fluid and muscle. Although this CT appearance is not specific for cervical chordoma, it is unusual for neurofibroma. Cervical chordoma should be considered in the differential diagnosis of focal enlargement of cervical intervertebral foramina.

Computed tomography of spontaneous acute cervical epidural hematoma

Cervical spinal epidural hematoma is a rare cause of acute neurologic syndromes including paralysis of various types. Although devastating, it can be successfully treated surgically if recognized early. We report two cases of spontaneous cervical epidural hematoma diagnosed by computed tomography, the first with a plain scan and the second with a scan after intrathecal injection of metrizamide. In both patients the diagnosis was not clinically suspected. Surgery resulted in a dramatic improvement of the neurologic deficit in both cases.

Experimental treatment of cerebral vascular spasm secondary to subarachnoid hemorrhage

Cerebral artery spasm following subarachnoid hemorrhage (SAH) is a major cause of morbidity and mortality. Treatment or prevention methods are most desirable. Using the basilar artery of the rabbit, cerebral arterial spasm was induced with an injection of 4 ml of autologous blood via cisternal puncture in six treated, four pre-treated and six control animals. Vertebral angiography was performed before and at ten, twenty, thirty and sixty minutes after the injection of blood was carried out, and the presence of spasm and its cause were followed in these animals. Pre-treated and treated subjects received 2 mg/kg of diltiazem (a calcium antagonist) either before and after the injection of blood, respectively. Analysis of vessel diameters by computer assisted densitometry showed that the treated group had a significant reduction of basilar artery spasm when compared to the control group, while in the pre-treated group, spasm was prevented.