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Biomedical subjects

E Zager

Publications and source records attributed to E Zager.

9 recordsLinked to original sources
PubMed1999

The calibration and validation of a phase-modulated near-infrared cerebral oximeter.

OBJECTIVE: This study was undertaken to compare the cerebral oxygenation measured by an experimental phase-modulated near-infrared (NIR) spectroscopy system with capillary saturation estimated from jugular venous oxygen saturation. METHODS: Jugular venous catheters were placed in 30 patients undergoing carotid endarterectomy and 194 measurements of venous oxygen saturation were obtained intra operatively. Simultaneous measurement of optical path length at 754, 785, and 816 nm was performed using a phase-modulated near-infrared spectroscopy system. Optical calibration was performed using both an optical bench and a scattering mold. Hemoglobin saturation was calculated from NIR measurements using equations derived from diffusion theory. Capillary saturation was calculated from the arterial and venous saturations. RESULTS: Jugular venous saturations ranged from 41 to 92%. When calibrated using the optical bench, the NIR estimates of hemoglobin saturation deviated from estimated capillary values by an average of 2.6% bias and 4.3% deviation. No systematic bias was noted. NIR values derived from mold calibration were less accurate and precise (4.6% bias and 6.9% deviation.) Use of the initial venous sample as an in vivo calibration improved the accuracy of the mold calibration but did not alter the performance of the bench calibration. CONCLUSIONS: Under the conditions tested, an experimental phase-modulated near-infrared spectroscopy system calibrated using an optical bench agreed with capillary saturation estimated from jugular venous samples. Further work is necessary to demonstrate valid performance of the system under other conditions.

Aged↗
PubMed1998

Endovascular stent treatment of cervical internal carotid artery aneurysms with parent vessel preservation.

BACKGROUND: Aneurysms involving the cervical portion of the internal carotid artery (ICA) frequently result from prior trauma or dissection. CASE DESCRIPTIONS: Two patients are reported with cervical internal carotid artery aneurysms. In both cases, disease involving the contralateral ICA precluded safe treatment of the aneurysms by ICA occlusion. Endovascular stents placed across the diseased portion of the artery resulted in thrombosis of the aneurysm with preservation of the parent artery. CONCLUSION: Endovascular stent placement should be considered for treatment of aneurysms involving the cervical ICA when preservation of the parent vessel is necessary.

Carotid Artery Diseases↗
PubMed1998

Carotid cavernous fistula associated with persistent trigeminal artery: endovascular treatment using coil embolization.

Carotid-cavernous fistula (CCF) associated with persistent trigeminal artery (PTA) is a rare but important clinical entity. We present a case treated by microcoil embolization with preservation of internal carotid, PTA, and hasilar artery flow following embolization. A 62-year-old female developed pulsatile tinnitus followed by left eye proptosis and diplopia. Examination revealed a cranial nerve VI palsy and an objective bruit over the left orbit. Angiographic evaluation revealed a carotid cavernous fistula originating from a persistent trigeminal artery. Placement of a detachable balloon across the fistula site while preserving the PTA proved impossible, and the fistula was treated with microcoils following placement of a microcatheter across the fistula into the cavernous sinus. Complete closure of the fistula was followed by resolution of the patient's symptoms. Preservation of all major vessels including the PTA was accomplished through the use of coil embolization. Careful evaluation of the angiogram is necessary to identify PTA associated with a CCF. Previous reports have described treatment of CCF with PTA by surgical or balloon ocolusion, some involving sacrifice of the PTA. Examination of the relevant embryology and anatomy reveals, however, that occlusion of the PTA must be approached with caution due to potential supply to the posterior circulation.

Case Reports↗
PubMed1998

Brainstem origins of the n18 component of the somatosensory evoked response.

Proposed generator sites for the N18 component of the somatosensory evoked potential (SEP) range in location from the medulla to the thalamus. Additional knowledge regarding the generators of the N18 will be important in interpreting the results of intra-operative monitoring during skull base surgery and providing the surgeon more specific information. The goal of this study was to use both intracranial electrical recording and the effects of acute brainstem ischemia in humans to further define the generators of N18. Monopolar electrodes were used to record SEP (after median nerve stimulation) from the brainstem surface in eight patients undergoing posterior fossa surgical procedures. Recordings were made from various locations, from the cervico-medullary junction to the level of the aqueduct of Sylvius. As the electrode moved rostrally on the brainstem surface, the difference in latencies between the scalp N18 potential and the electrode potential approached zero, suggesting an upper pontine-lower midbrain origin of the N18 potential. These findings were supported by the lack of change in the N18 potentials of ten patients with basilar tip aneurysms who experienced marked changes of their N20/P22 potentials during temporary occlusion of the distal basilar artery.

Journal Article↗
PubMed1998

Dementia resulting from dural arteriovenous fistulas: the pathologic findings of venous hypertensive encephalopathy.

PURPOSE: Dural arteriovenous fistulas (DAVFs) are acquired arteriovenous shunts located within the dura. The highly variable natural history and symptomatology of DAVFs range from subjective bruit to intracranial hemorrhage and are related to the lesion's pattern of venous drainage and its effect on the drainage of adjacent brain. We examined the prevalence and features of DAVFs in patients with progressive dementia or encephalopathy. METHODS: The records and radiologic studies of 40 consecutive patients with DAVFs treated at our institution were reviewed. RESULTS: Five (12.5%) of 40 consecutive patients with DAVFs had encephalopathy or dementia. In each patient, high flow through the arteriovenous shunt combined with venous outflow obstruction caused impairment of cerebral venous drainage. Hemodynamically, the result was widespread venous hypertension causing diffuse ischemia and progressive dysfunction of brain parenchyma. Results of CT or MR imaging revealed abnormalities in each patient, reflecting the impaired parenchymal venous drainage. Pathologic findings in one patient confirmed the mechanism of cerebral dysfunction as venous hypertension. The hemodynamic mechanism and resulting abnormality appeared identical to that seen in progressive chronic myelopathy resulting from a spinal DAVF (Foix-Alajouanine syndrome). Remission of cognitive symptoms occurred in each patient after embolization. CONCLUSION: Venous hypertensive encephalopathy resulting from a DAVF should be considered a potentially reversible cause of vascular dementia in patients with progressive cognitive deficits.

Aged↗
PubMed1996

Functional magnetic resonance imaging of regional brain activity in patients with intracerebral gliomas: findings and implications for clinical management.

Functional magnetic resonance imaging (fMRI) was performed in seven patients harboring intracerebral gliomas proven by histological analysis using a noninvasive blood oxygen level-dependent technique based on the documented discrepancy between regional increases in blood flow and oxygen use in response to regional brain activation. We combined fMRI with conventional magnetic resonance imaging (MRI) during motor or language task activation experiments to investigate the potential usefulness of mapping regional brain activity as part of treatment planning in patients with intracerebral gliomas, in whom preservation of areas of functioning brain tissue is critical. Statistical fMRI maps were generated and directly mapped onto conventional MRI scans obtained at the same session. Of the five patients cooperative enough to remain motionless for the study and perform the task, the location of activation in the primary sensorimotor cortex on the side of the tumor was clearly displaced compared with that in the normal contralateral hemisphere in four patients. Four of the five tumors in these patients showed fMRI activation within the periphery of (or immediately adjacent to) areas of presumed tumor based on spin-echo MRI. In some patients with neurological deficit, the extent of activation was reduced on the side of the tumor as compared with the normal hemisphere. The supplemental motor area and the ipsilateral primary motor cortex were also reproducibly activated during motor tasks. We conclude that blood oxygen level-dependent fMRI can localize areas of cortical function in patients undergoing treatment planning for gliomas so that therapy can be directed away from regions of residual function. Our preliminary data suggest that functioning cortex within or adjacent to tumor margins can be demonstrated, which may correspond to partial preservation of clinical function. Our preliminary data also suggest that there may be a quantifiable difference on fMRI between activation in tumor-bearing cortex and activation in corresponding normal cortex in the contralateral hemisphere. We postulate that the magnitude of this difference may relate to the severity of patient deficit.

Adolescent↗
PubMedDate not supplied

Erythromelalgia: diagnosis and classification.

Erythromelalgia is not a commonly recognized or diagnosed condition that affects the lower extremities. The first reported case was in 1878, when Mitchell suggested the term "erythromelalgia." This condition is characterized by a burning sensation with erythema of the involved extremity. When the extremity is lowered, or heat is applied, the pain is intensified. The application of cold or elevation of the extremity will have the opposite effect of decreasing the pain. Erythromelalgia is classified as primary or idiopathic if there is no accompanying disease process. Secondary erythromelalgia is associated commonly with myeloproliferative syndrome-related thrombocythemia, and is mostly evident in adult onset of the condition. Treatment for adults with erythromelalgia includes a single daily dose of aspirin, but children who have no associated underlying disorder find little to no relief with acetylsalicylic acid.

Adult↗
PubMedDate not supplied

Residue chemistry guidelines.

Residue chemistry guidelines are designed to determine what the potential residues in food are and how much may be present as a result of pesticide application, so that a tolerance level may be established. Some requirements are established to assist in the enforcement of tolerances by the USDA, FDA, and the states. I realize I have given you a quick overview of the residue chemistry requirements. There are many documents which are available if you should require more information, such as the Subdivision O Residue Chemistry Guidelines, Standard Evaluation Procedures (which are used by reviewers when evaluating the studies), the Data Reporting Guidelines (which provide guidance on preparing final reports), and the Technical Guidance from Phase III of Reregistration. We have also released various papers on studies when additional guidance is required. Most of these documents are available from NTIS. I hope you will consider this information when auditing residue chemistry studies. As I see the efforts that you, the QA professionals, have made to educate yourselves on residue chemistry studies through programs such as this meeting, I have a little more confidence in answering the question "Do you trust them?" with a "Yes." Thank you.

Data Collection↗