Biomedical subjects

Raphael Guzman

Publications and source records attributed to Raphael Guzman.

8 recordsLinked to original sources

PubMed2006

Cerebral perfusion imaging in vasospasm.

Vasospasm following cerebral aneurysm rupture is one of the most devastating sequelae and the most common cause of delayed ischemic neurological deficit (DIND). Because vasospasm also is the most common cause of morbidity and mortality in patients who survive the initial bleeding episode, it is imperative not only to diagnose the condition but also to predict which patients are likely to become symptomatic. The exact pathophysiology of vasospasm is complex and incompletely elucidated. Early recognition of vasospasm is essential because the timely use of several therapeutic interventions can counteract this disease and prevent the occurrence of DIND. However, the prompt implementation of these therapies depends on the ability to predict impending vasospasm or to diagnose it at its early stages. A number of techniques have been developed during the past several decades to evaluate cerebral perfusion, including positron emission tomography, xenon-enhanced computed tomography, single-photon emission computed tomography, perfusion- and diffusion-weighted magnetic resonance imaging, and perfusion computed tomography. In this article, the authors provide a general overview of the currently available perfusion imaging techniques and their applications in treating vasospasm after a patient has suffered a subarachnoid hemorrhage. The use of cerebral perfusion imaging techniques for the early detection of vasospasm is becoming more common and may provide opportunities for early therapeutic intervention to counteract vasospasm in its earliest stages and prevent the occurrence of DINDs.

Cerebrovascular Circulation↗

PubMed2006

Propionibacterium acnes infections after cranial neurosurgery.

BACKGROUND: Propionibacterium acnes (P. acnes) is a relatively avirulent organism that is part of the normal skin flora. Most patient isolates are considered contaminants but, in a small subset of patients, particularly in the post-neurosurgery setting, the organism can cause significant infections. We reviewed our experience with the occurrence and management of P. acnes infections after cranial neurosurgical procedures over a five-year period. METHODS: Patients with positive cultures for P. acnes between 1996 and 2001 were identified by review of the Saskatoon Health Region microbiology laboratory database. Of the 141 positive cultures, a review of hospital records identified six patients with P. acnes infections after neurosurgical procedures. A review of the literature related to P. acnes associated CNS infections was conducted. RESULTS: All patients had undergone a craniotomy or burrhole placement, and one patient had received prior radiotherapy. There were no P. acnes-related ventriculoperitoneal shunt infections. All patients presented with scalp swelling and three had purulent discharge. Symptoms occurred more than two months after the initial surgery in five of six patients, while one patient developed symptoms three years post-operatively. Management for all patients included removal of the craniotomy flap and treatment with parenteral antibiotics, followed in most cases by oral antibiotics. A good response without relapse of infection was seen in five patients; one patient had recurrent infection after cranioplasty. CONCLUSIONS: P. acnes is a rare but important cause of infection after craniotomy. Wound debridement, removal of the bone flap and adequate antibiotic coverage result in cure in the majority of patients.

Child↗

PubMed2005

High-resolution three-dimensional T2-weighted sequence for neuronavigation: a new setup and clinical trial.

OBJECT: Conventional imaging for neuronavigation is performed using high-resolution computerized tomography (CT) scanning or a T1-weighted isovoxel magnetic resonance (MR) sequence. The extension of some lesions, however, is depicted much better on T2-weighted MR images. A possible fusion process used to match low-resolution T2-weighted MR image set with a referenced CT or T1-weighted data set leads to poor resolution in the three-dimensional (3D) reconstruction and decreases accuracy, which is unacceptable for neuronavigation. The object of this work was to develop a 3D T2-weighted isovoxel sequence (3D turbo-spin echo [TSE]) for image-guided neuronavigation of the whole brain and to evaluate its clinical application. METHODS: The authors performed a phantom study and a clinical trial on a newly developed T2-weighted isovoxel sequence, 3D TSE, for image-guided neuronavigation using a common 1.5-tesla MR imager (Siemens Sonata whole-body imager). The accuracy study and intraoperative image guidance were performed with the aid of the pointer-based Medtronic Stealth Station Treon. The 3D TSE data set was easily applied to the navigational setup and demonstrated a high registration accuracy during the experimental trial and during an initial prospective clinical trial in 25 patients. The sequence displayed common disposable skin fiducial markers and provided convincing delineation of lesions that appear hyperintense on T2-weighted images such as low-grade gliomas and cavernomas in its clinical application. CONCLUSIONS: Three-dimensional TSE imaging broadens the spectrum of navigational and intraoperative data sets, especially for lesions that appear hyperintense on T2-weighted images. The accuracy of its registration is very reliable and it enables high-resolution reconstruction in any orientation, maintaining the advantages of image-guided surgery.

Adult↗

PubMed2005

Endovascular treatment of posterior circulation cerebral aneurysms by using Guglielmi detachable coils: a 10-year single-center experience with special regard to technical development.

BACKGROUND AND PURPOSE: The purpose of this study was to analyze the immediate and long-term angiographic and clinical results of endovascular treatment of posterior circulation aneurysms with special regard to technical development. MATERIALS: Between 1993 and 2003, 46 patients with 47 aneurysms of the posterior circulation were referred to our institution for endovascular treatment. Mean angiographic follow-up was 1.7 years. Clinical follow-up was determined at hospital discharge and by using a questionnaire for long-term follow-up (mean, 3.3 years). To analyze technical development, patients treated before (group 1) and after (group 2) implementation of 3D Guglielmi detachable coils (3D GDCs) in 1999 were compared. Multivariate analysis was performed to determine factors predictive of clinical and technical outcome. RESULTS: Overall, at initial treatment complete occlusion was achieved in 27 (57.4%) aneurysms, a neck remnant was present in 16 (34.0%) aneurysms, incomplete occlusion was achieved in 3 (6.4%) aneurysms, and in 1 (2.1%) case occlusion was not attempted. Procedure-related permanent morbidity was 4.3%, and the mortality rate was 0%. There was no rebleeding of treated aneurysms. Complete occlusion at initial treatment (P = .003) and recanalization rate (P = .008) correlated with aneurysm sac size. A statistically significant relationship between Hunt and Hess/World Federation of Neurologic Surgeons clinical grading scale score and clinical outcome (Glasgow Outcome Score) was found (P < .05). Subgroup analysis revealed that a higher initial obliteration rate of larger aneurysms was achieved in group 2 (3D GDC, 22 patients, 22 aneurysms) than in group 1 (23 patients, 24 aneurysms; P = .03). At angiographic follow-up, overall recanalization was 47.1% in group 2 and 47.6% in group 1. Aneurysm neck size was not found to be correlated with occlusion and recanalization rate. CONCLUSION: In our series, GDC technology was an effective and safe technique for the treatment of posterior circulation aneurysms. Aneurysm sac size was predictive for occlusion rate and the Hunt and Hess/World Federation of Neurologic Surgeons grade for clinical outcome. The introduction of 3D GDCs into our practice significantly improved the initial occlusion rate but did not affect the incidence of recanalization.

Adolescent↗

PubMed2004

Preoperative transarterial embolization of vertebral metastases.

The aim of this study was to evaluate the impact of preoperative devascularization of spinal metastases in relation to the preembolization tumor vascularization degree and in relation to the intraoperative blood loss. Twenty-four patients underwent preoperative transarterial embolization of hypervascular spinal metastases. Each tumor was assigned a vascularization grade (I-III) according to tumor blush after contrast agent injection in the main feeding artery. Embolization was performed with polyvinyl alcohol particles in all patients. Surgical reports were reviewed in terms of estimated blood loss. A mild hypervascularization was found in three patients (group I), medium in six patients (group II) and extensive in 15 patients (group III). In 22 out of 24 patients embolization could be performed with a complete devascularization. In two patients, only partial embolization could be performed, due to the main feeding artery arising from the artery of Adamkiewicz. In patients with complete devascularization the mean intraoperative blood loss was 1,900 ml, whereas in the two patients who were not embolized it was 5,500 ml. Intraoperative blood loss was not correlated to the vascularization grade. Angiography and embolization could be performed in all patients without causing permanent neurologic deficit, skin or muscle necrosis. The surgeons concluded that radical tumor resection after embolization was facilitated. Intraoperative blood loss is not correlated with the pre-interventional vascularization degree, if complete devascularization can be achieved with embolization. Preoperative embolization of vertebral hypervascular tumors is safe, effective and facilitates tumor resection.

Adult↗

PubMed2004

Insulin-like growth factor (IGF)-I obliterates the pregnancy-associated protection against mammary carcinogenesis in rats: evidence that IGF-I enhances cancer progression through estrogen receptor-alpha activation via the mitogen-activated protein kinase pathway.

INTRODUCTION: Pregnancy protects against breast cancer development in humans and rats. Parous rats have persistently reduced circulating levels of growth hormone, which may affect the activity of the growth hormone/insulin-like growth factor (IGF)-I axis. We investigated the effects of IGF-I on parity-associated protection against mammary cancer. METHODS: Three groups of rats were evaluated in the present study: IGF-I-treated parous rats; parous rats that did not receive IGF-I treatment; and age-matched virgin animals, which also did not receive IGF-I treatment. Approximately 60 days after N-methyl-N-nitrosourea injection, IGF-I treatment was discontinued and all of the animal groups were implanted with a silastic capsule containing 17beta-estradiol and progesterone. The 17beta-estradiol plus progesterone treatment continued for 135 days, after which the animals were killed. RESULTS: IGF-I treatment of parous rats increased mammary tumor incidence to 83%, as compared with 16% in parous rats treated with 17beta-estradiol plus progesterone only. Tumor incidence and average number of tumors per animal did not differ between IGF-I-treated parous rats and age-matched virgin rats. At the time of N-methyl-N-nitrosourea exposure, DNA content was lowest but the alpha-lactalbumin concentration highest in the mammary glands of untreated parous rats in comparison with age-matched virgin and IGF-I-treated parous rats. The protein levels of estrogen receptor-alpha in the mammary gland was significantly higher in the age-matched virgin animals than in untreated parous and IGF-I-treated parous rats. Phosphorylation (activation) of the extracellular signal-regulated kinase-1/2 (ERK1/2) and expression of the progesterone receptor were both increased in IGF-I-treated parous rats, as compared with those in untreated parous and age-matched virgin rats. Expressions of cyclin D1 and transforming growth factor-beta3 in the mammary gland were lower in the age-matched virgin rats than in the untreated parous and IGF-I-treated parous rats. CONCLUSION: We argue that tumor initiation (transformation and fixation of mutations) may be similar in parous and age-matched virgin animals, suggesting that the main differences in tumor formation lie in differences in tumor progression caused by the altered hormonal environment associated with parity. Furthermore, we provide evidence supporting the notion that tumor growth promotion seen in IGF-I-treated parous rats is caused by activation of estrogen receptor-alpha via the Raf/Ras/mitogen-activated protein kinase cascade.

Adenocarcinoma↗

PubMed2002

Fast contrast-enhanced MR whole-brain venography.

Our aim was to assess the value of a new fast contrast-enhanced MR venography (CE-MRV) sequence in the investigation of normal and diseased cerebral veins. Conventional time-of-flight (TOF) MRV is time consuming, with imaging for a single sequence taking many minutes. MRI was performed with a clinical 1.5-T scanner; conventional TOF MRV followed by CE-MRV was performed using a modified 3D first-pass MR angiography sequence. Ten control subjects without cerebral pathology were studied as well as ten patients with cerebral venous thrombosis for a total of 20 studies with both sequences. CE-MRV was able to provide a set of complete MRV images in a significantly shorter time than conventional MRV sequencing could. The field of view also provided greater coverage of the vessels of the head and neck. CE-MRV also provided more extensive small vein detail and provided a better demonstration of intraluminal defects, despite a slightly lower resolution. Both methods were equally suited for the demonstration of venous thrombosis and demonstrated all cases equally well; however, CE-MRV provided more detailed information by showing partially obstructed sinuses and by showing better the presence of cortical collateral venous drainage.

Adolescent↗

PubMed2002

Use of diffusion-weighted magnetic resonance imaging in differentiating purulent brain processes from cystic brain tumors.

OBJECT: Brain abscesses and other purulent brain processes represent potentially life-threatening conditions for which immediate correct diagnosis is necessary to administer treatment. Distinguishing between cystic brain tumors and abscesses is often difficult using conventional imaging methods. The authors' goal was to study the ability of diffusion-weighted (DW) magnetic resonance (MR) imaging to differentiate between these two pathologies in patients within the clinical setting. METHODS: Diffusion-weighted MR imaging studies and calculation of the apparent diffusion coefficient (ADC) values were completed in a consecutive series of 16 patients harboring surgically verified purulent brain processes. This study group included 11 patients with brain abscess (one patient had an additional subdural hematoma and another also had ventriculitis), two with subdural empyema, two with septic embolic disease, and one patient with ventriculitis. Data from these patients were compared with similar data obtained in 16 patients matched for age and sex, who harbored surgically verified neoplastic cystic brain tumors. In patients with brain abscess, subdural empyema, septic emboli, and ventriculitis, these lesions appeared hyperintense on DW MR images, whereas in patients with tumor, the lesion was visualized as a hypointense area. The ADC values calculated in patients with brain infections (mean 0.68 x 10(3) mm2/sec) were significantly lower than those measured in patients with neoplastic lesions (mean 1.63 x 10(3) mm2/sec; p < 0.05). CONCLUSIONS: Diffusion-weighted MR imaging can be used to identify infectious brain lesions and can help to differentiate between brain abscess and cystic brain tumor, thus making it a strong additional imaging modality in the early diagnosis of central nervous system purulent brain processes.

Adult↗