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Biomedical subjects

Wendy C Ziai

Publications and source records attributed to Wendy C Ziai.

11 recordsLinked to original sources
PubMed2006

Brainstem stroke following uncomplicated cervical epidural steroid injection.

BACKGROUND: Cervical epidural steroid injection treatment of radicular pain has become a common procedure. OBJECTIVES: To describe the clinical, radiologic, and autopsy findings of a 41-year-old patient treated with methylprednisolone acetate cervical epidural steroid injection, who developed a fatal hemorrhagic brainstem infarction and to discuss the possible mechanisms involved. DESIGN: Case report. SETTING: Pain management center and tertiary care hospital. RESULTS: Immediately following a seemingly uncomplicated epidural steroid injection at C5-6, the patient developed progressive symptoms of extensive brainstem and thalamic infarction (documented by magnetic resonance imaging and autopsy) with hemorrhagic conversion and hydrocephalus. Hemorrhage within the adventitia of the left vertebral artery, but no dissection, was found at the C5 vertebral level at necropsy. CONCLUSIONS: This case report shows the possibility of serious intracranial pathology resulting from cervical epidural steroid injection despite use of fluoroscopic guidance. Vascular spasm distant to the site of injection is a possible mechanism.

Adult↗
PubMed2005

Target-specific catecholamine elevation induced by anticonvulsant thalamic deep brain stimulation.

PURPOSE: Anterior thalamic nucleus (AN) deep brain stimulation (DBS) is effective in raising EEG and clonic seizure threshold in experimental models. Little is known about the specific properties of DBS that afford its anticonvulsant effect. We sought to test the hypothesis that experimental seizures and the anticonvulsant action of AN DBS alter the underlying regional neurochemistry of AN, specifically with facilitation of the serotonergic system to local electrical stimulation. METHODS: Halothane-anesthetized adult Sprague-Dawley male rats underwent stereotactically guided bilateral placement of bipolar stimulating steel electrodes and dialysis probes-guide cannulae in AN and posterior thalamus (PT), and placement of four epidural EEG screw electrodes 48 h before experiments. Both stimulated (AN DBS) and nonstimulated (NO DBS) animals (n=7 per group) were infused with i.v. pentylenetetrazol (PTZ, 5.5 mg/kg/min). Simultaneous thalamic and cortical EEG were recorded, and microdialysis samples were collected from AN and PT in 20-min epochs. AN stimulation was delivered (150 microA; 0.1-ms pulse duration) 40 min before and continued during PTZ infusion. RESULTS: Bilateral AN stimulation delayed the onset of EEG seizures compared with controls: 82+/-8 vs. 58+/-5 min (p=0.02). PTZ infusion alone, or together with stimulation, resulted in a steady increase in norepinephrine (NE), but not dopamine, at AN and PT sites (p<0.001). Although extracellular serotonin was measured at very low levels, the metabolite, 5-hydroxyindoleacetic acid (5-HIAA) increased selectively in AN after stimulation and during preconvulsant infusion of PTZ (p<0.001), returning to baseline after the first generalized seizure. CONCLUSIONS: These data suggest that PTZ and DBS together enhance the nonselective release of NE in thalamic nuclei while specifically stimulating AN-localized serotonin. Low serotonin levels at baseline and during STIM alone or PTZ infusion may indicate efficient reuptake systems for serotonin, with 5-HIAA serving as a surrogate marker for serotonergic activity. Modulation of the AN-specific serotonergic activity may be critical in altering PTZ seizure threshold and be an important neurotransmitter system underlying the efficacy of AN DBS.

Animals↗
PubMed2005

Quantitation of contrast TCD in patients with and without atrial septal aneurysm.

BACKGROUND AND PURPOSE: Patients with a combination of atrial septal aneurysm (ASA) and patent foramen ovale (PFO) have a substantially higher rate of recurrent ischemic events as compared to PFO alone. One possible explanation is a greater degree of right-to-left shunting with the combination. METHODS: Retrospective study using contrast transcranial Doppler ultrasonography (c-TCD) to study the degree of shunting in 46 patients with PFO with either transient ischemic attack or cryptogenic ischemic stroke. Eight patients with PFO+ASA identified on transesophageal echocardiogram were compared to 38 patients with PFO but without ASA. RESULTS: The number of embolic counts was no different with or without an ASA. Valsalva maneuver increased number of emboli, especially in patients with large PFOs. CONCLUSIONS: Patients with ASA in addition to PFO do not appear to have an increased risk of right-to-left shunting as measured by c-TCD as compared to PFO alone.

Case-Control Studies↗
PubMed2003

Decompressive craniectomy for intractable cerebral edema: experience of a single center.

Several case reports and small clinical series have reported benefits of decompressive hemicraniectomy in patients with intractable cerebral edema and early clinical herniation. Specific indications and timing for this intervention remain unclear. We present our experience with this procedure in a subset of 18 patients with massive cerebral edema refractory to medical management, treated with decompressive craniectomy over a 3-year period (1997 to 2000). Computerized tomography (CT) scans were independently analyzed by a neuroradiologist blinded to clinical outcome. Eleven male and seven female patients, ages 20 to 69 years (mean +/- SEM, 46 +/- 14 years), underwent hemicraniectomy for the following diagnoses: 12 hemispheric infarcts, 3 traumatic intracerebral hemorrhages/contusions, 2 nontraumatic intraparenchymal hemorrhages (ICH), and 1 subdural empyema. This population included four patients with aneurysmal subarachnoid hemorrhage (SAH). Patients were followed for a mean of 10 months. Clinical factors including age, side of lesion, preoperative herniation signs, and early surgery (<12 or <24 hours) were not significantly associated with mortality or Glasgow outcome score (GOS). Preoperative CT evidence of transtentorial herniation (present in 5/17 patients) was associated with mortality ( = 0.04), while preoperative uncal herniation (8/17 patients) was associated with poor outcome (GOS > 1) ( = 0.01). Favorable outcome (GOS > 3) occurred in six patients, three with spontaneous or traumatic focal hematomas. Of four patients with SAH, one died while the others were severely disabled (GOS 3). Seven of nine patients with malignant MCA infarctions unrelated to SAH had poor outcomes. The overall mortality was 4/18 (22%). Patients with refractory cerebral swelling secondary to focal hematomas may have better outcomes following decompressive craniectomy. Patients with preexisting SAH seem to have poor outcomes, possibly related to other neurologic comorbidities. Hemicraniectomy requires definition of proper timing. Preoperative CT findings, especially transtentorial and uncal herniation may be useful in defining when decompressive surgery should not be performed.

Adult↗
PubMed2003

Neurologic intensive care resource use after brain tumor surgery: an analysis of indications and alternative strategies.

OBJECTIVE: Greater demand and limited resources for intensive care monitoring for patients with neurologic disease may change patterns of intensive care unit utilization. The necessity and duration of intensive care unit management for all neurosurgical patients after brain tumor resection are not clear. This study evaluates a) the preoperative and perioperative variables predictive of extended need for intensive care unit monitoring (>1 day); and b) the type and timing of intensive care unit resources in patients for whom less intensive postoperative monitoring may be feasible. DESIGN: Retrospective chart review. SETTING: A neurocritical care unit of a university teaching hospital. PATIENTS: Patients were 158 consecutive postoperative brain tumor resection patients admitted to a neurocritical care unit within a 1-yr period (1998-1999). INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Twenty-three patients (15%) admitted to the neurocritical care unit for >24 hrs were compared with 135 (85%) patients admitted for <24 hrs. Predictors of >1-day stay in the neurocritical care unit in a logistic regression model were a tumor severity index comprising radiologic characteristics of tumor location, mass effect, and midline shift on the preoperative magnetic resonance imaging scan (odds ratio, 12.5; 95% confidence interval, 3.1-50.5); an intraoperative fluid score comprising estimated blood loss, total volume of crystalloid, and other colloid/hypertonic solutions administered (odds ratio, 1.8; 95% confidence interval, 1.2-2.6); and postoperative intubation (odds ratio, 67.5; 95% confidence interval, 6.5-702.0). Area under the receiver operating characteristic curve for the model of independent predictors for staying >1 day in the neurocritical care unit was 0.91. Neurocritical care unit resource use was reviewed in detail for 134 of 135 patients who stayed in the neurocritical care unit for <1 day. Sixty-five (49%) patients required no interventions beyond postanesthetic care and frequent neurologic exams. A total of 226 intensive care unit interventions were performed (mean +/- sd, 1.7 +/- 2.6) in 69 (51%) patients. Ninety (67%) patients had no further interventions after the first 4 hrs. Neurocritical care unit resource use beyond 4 hrs, largely consisting of intravenous analgesic use (72% of orders), was significantly associated with female gender, benign tumor on frozen section biopsy, and postoperative intubation (chi-square, p <.05). CONCLUSIONS: A small fraction of patients require prolonged intensive care unit stay after craniotomy for tumor resection. A patient's risk of prolonged stay can be well predicted by certain radiologic findings, large intraoperative blood loss, fluid requirements, and the decision to keep the patient intubated at the end of surgery. Of those patients requiring intensive care unit resources beyond the first 4 hrs, the interventions may not be critical in nature. A prospective outcome study is required to determine feasibility, cost, and outcome of patients cared for in extended recovery and then transferred to a skilled nursing ward.

Aged↗
PubMed2003

Prediction of PTZ-induced seizures using wavelet-based residual entropy of cortical and subcortical field potentials.

Our proposed algorithm for seizure prediction is based on the principle that seizure build-up is always preceded by constantly changing bursting levels. We use a novel measure of residual subband wavelet entropy (RSWE) to directly estimate the entropy of bursts, which is otherwise obscured by the ongoing background activity. Our results are obtained using a slow infusion anesthetized pentylenetetrazol (PTZ) rat model in which we record field potentials (FPs) from frontal cortex and two thalamic areas (anterior and posterior nuclei). In each frequency band, except for the theta-delta frequency bands, we observed a significant build-up of RSWE from the preictal period to the first ictal event (p < or = 0.05) in cortex. Significant differences were observed between cortical and thalamic RSWE (p < or = 0.05) subsequent to seizure development. A key observation is the twofold increase in mean cortical RSWE from the preictal to interictal period. Exploiting this increase, we develop a slope change detector to discern early acceleration of entropy and predict the approaching seizure. We use multiple observations through sequential detection of slope changes to enhance the sensitivity of our prediction. Using the proposed method applied to a cohort of four rats subjected to PTZ infusion, we were able to predict the first seizure episode 28 min prior to its occurrence.

Algorithms↗
PubMed2003

Wavelet entropy for subband segmentation of EEG during injury and recovery.

In this paper, subband wavelet entropy (SWE) is used for the segmentation of electroencephalographic signals (EEG) recorded during injury and recovery following global cerebral ischemia. Wavelet analysis is used to decompose the EEG into standard clinical subbands followed by computation of the Shannon entropy. The EEG was measured from rodent brains in a controlled experimental brain injury model by hypoxic-ischemic cardiac arrest. Results show that while the relative EEG power failed to reveal the order of bursting activity associated with recovery, SWE was used to segment the EEG and delineate the initial bursting periods in each subband. Based on entropy variations obtained from a cohort of animals with graded levels of hypoxic-ischemic cardiac arrest, an intermittent pattern of bursting was observed in the high frequency bands.

Algorithms↗
PubMed2003

Stroke-free survival and its determinants in patients with symptomatic vertebrobasilar stenosis: a multicenter study.

OBJECTIVE: We sought to determine the long-term stroke-free survival of patients who present with ischemic events related to intracranial vertebrobasilar stenosis. METHODS: A retrospective cohort of patients diagnosed with symptomatic vertebrobasilar stenosis on the basis of magnetic resonance angiography and/or conventional angiography was identified at four academic medical centers. Patients' clinical and follow-up information was obtained through hospitalization records, clinic visits, and telephone interviews. Kaplan-Meier analysis was performed to determine the rate of stroke-free survival for a 5-year period. Cox proportional hazards analysis was performed to determine the effect of demographic and clinical factors on stroke-free survival. RESULTS: A total of 102 patients were included, whose mean age was 64 +/- 12 years. Fifty-five (54%) of the patients were men. The mean follow-up period was 15 +/- 15.9 months (range, 1-60 mo). During the follow-up period, 14 (14%) of the patients experienced recurrent stroke. The overall mortality rate was 21% (n = 21). Stroke-free survival, calculated by using the Kaplan-Meier curve, was 76% at 12 months (95% confidence interval [CI], 66-83%) and 48% at 5 years (95% CI, 27-65%). The risk of recurrent stroke was 10.9 per 100 patient-years, and the rate of recurrent stroke and/or death was 24.2 per 100 patient-years. Cox proportional hazards analysis revealed that increasing age (hazards ratio, 1.05; 95% CI, 1.00-1.09) decreased stroke-free survival. Treatment with either antiplatelet agents or warfarin (hazards ratio, 0.018; 95% CI, 0.003-0.11) had a protective effect on stroke-free survival after adjusting for age, sex, race, hypertension, diabetes mellitus, smoking, hyperlipidemia, and lesion location. CONCLUSION: A low rate of stroke-free survival is observed in patients with symptomatic vertebrobasilar stenosis. Further studies are required to evaluate new medical and endovascular treatment options for this group of patients to improve long-term stroke-free survival.

Aged↗