Biomedical subjects

Terence J O'Brien

Publications and source records attributed to Terence J O'Brien.

23 records · Page 2Linked to original sources

PubMed2004

A computer-generated stereotactic "Virtual Subdural Grid" to guide resective epilepsy surgery.

BACKGROUND AND PURPOSE: In selected patients undergoing epilepsy surgery, subdural electrode grids play an important role in localizing the epileptogenic zone and identifying eloquent cortex. Determining the relationship of the electrodes to underlying brain architecture traditionally has been difficult. This report describes and validates the use of an original computer-aided method that displays a representation of the electrode positions, based on postimplantation CT or MR findings, coregistered with a 3D-rendered image of the brain, on an image-guided surgery system. METHODS: Seventeen patients underwent the procedure with visual verification of the actual and virtual grids undertaken during the second (postimplantation) surgery. The accuracy of the Virtual Grid electrode positions was further studied in a subgroup of five patients during surgery by plotting the distance from the actual electrode positions by using an infrared stereotactic probe. RESULTS: The accuracy of the Virtual Grid electrode positions by visual inspection was satisfactory in all 17 cases. In the five cases in which quantitative measurements were performed, the mean error for the CT derived electrode positions was 3.4 mm (range 0.5-5.4) compared with the mean error for the MR-derived electrode positions of 2.5 mm (range 0.5-5.2). CONCLUSION: The Virtual Grid electrode positions were highly accurate in localizing the actual position of the subdural electrodes with both CT- and MR-derived images. The MR-derived electrodes demonstrated a trend toward better accuracy, but the CT images were quicker and easier to process. This technology has the potential to minimize both human and technical errors, allowing for a more precise tailoring of the cortical resection in epilepsy surgery.

Brain Mapping↗

PubMed2003

The Australian registry of anti-epileptic drugs in pregnancy: experience after 30 months.

BACKGROUND: Most women with epilepsy need to take antiepileptic drugs (AEDs) in pregnancy to prevent the potentially harmful effects of seizures. Retrospective studies have demonstrated an increased chance of having a child with a birth defect (BD) in women with epilepsy taking AEDs. It is uncertain how much of this risk is directly caused by the AEDs and whether certain drugs or combinations are associated with a greater risk. AIMS: To establish a register to evaluate prospectively the incidence of adverse pregnancy outcomes in women exposed to specific AEDs; to determine whether certain AEDs or combinations were associated with a greater risk; and to determine whether other factors influenced the risk. METHODS: An Australia-wide, prospective, voluntary, telephone-interview based, observational register. Three groups of pregnant women were enrolled: those with epilepsy taking AEDs, those with epilepsy not taking AEDs, and those taking AEDs for a non-epileptic indication. The pregnancy outcomes were evaluated by follow-up interviews and by reference to hospital and treating doctors' records. RESULTS: Over the first 30 months of the study (till December 2001) 334 eligible women were enrolled, with all states and territories being represented. Two hundred and ninety two pregnancies had been completed, of which 256 (88%) resulted in a healthy live birth, 19 (6.5%) a live birth with a birth defect, four an induced abortion because of a detected malformation on ultrasound, one premature labour with a stillbirth and 12 (4%) spontaneous abortions. Of the completed pregnancies, 269 were exposed to at least one AED during the first trimester. The incidence of birth defects in relation to specific AEDs was: valproate (16.7%), phenytoin (10.5%), lamotrigine (7.7%) and carbamazepine (3.3%), none of which was significantly different from that in women with epilepsy not taking an AED (4.3%, n.s.). The dose of valproate taken was higher in pregnancies with BD compared to those without (mean 2081 mg vs. 1149 mg, p<0.0001). The incidence of folate supplementation being taken prior to conception did not differ for pregnancy outcomes with or without BD (70% vs. 66%, n.s.). CONCLUSIONS: The model for the Australian Pregnancy Register appears to be successful, with strong enrolment from all regions over the first 30 months. The study is prospective and includes reference to all new AEDs approved in Australia over the past decade. Analysis of the pregnancy outcomes to date may reveal early trends, but numbers are still to small for any definitive conclusions to be made regarding the relative risk in pregnancy of individual AEDs.

Abortion, Induced↗

PubMed2002

Age of meningitis or encephalitis is independently predictive of outcome from anterior temporal lobectomy.

BACKGROUND: The occurrence of meningitis or encephalitis in early childhood, i.e., < or =4 years of age, may be associated with both the development of medial temporal lobe epilepsy (MTLE) and an excellent operative outcome following an anterior temporal lobectomy (ATL). However, whether the predictive value of this risk factor for partial epilepsy is independent of the finding of mesial temporal sclerosis (MTS) on MRI is not known. METHODS: Consecutive patients (n = 39) with a remote history of meningitis or encephalitis who underwent an ATL were compared with 78 sex- and age-matched control subjects who had not experienced a CNS infection before ATL. All patients in both groups had nonlesional temporal lobe epilepsy and were followed up for at least 12 months postoperatively. RESULTS: There was a trend for the patients with a history of meningitis or encephalitis to have a lower frequency of class I postoperative outcome (61.5% vs 73.1%, p = 0.21). In the meningitis or encephalitis group, a class I outcome was more frequent in those with a history of meningitis or encephalitis at a young age (<4 years) (19/23 vs 5/16, p = 0.002), those with MTS detected on a preoperative MRI (22/31 vs 2/8, p = 0.04), and those with a history of meningitis (16/21 vs 8/18, p = 0.05). Multivariate logistic regression analysis found that a history of meningitis or encephalitis at a young age (b = 2.0, O.R. = 7.5, p = 0.048) was predictive of a class I outcome independent of the presence of MRI-identified MTS (b = 2.0, O.R. = 7.3, p = 0.07). CONCLUSION: The age of occurrence of a remote history of meningitis or encephalitis, but not the type of infection, is predictive of outcome after an ATL independent of the finding of MTS on the preoperative MRI.

Adolescent↗

PubMed2002

Focal ictal beta discharge on scalp EEG predicts excellent outcome of frontal lobe epilepsy surgery.

PURPOSE: To determine whether a focal beta-frequency discharge at seizure onset on scalp EEG predicts outcome of frontal lobe epilepsy (FLE) surgery. METHODS: We identified 54 consecutive patients with intractable FLE who underwent epilepsy surgery between December 1987 and December 1996. A blind review of EEGs and magnetic resonance images (MRIs) was performed. Lesional epilepsy is defined as presence of an underlying structural abnormality on MRI. RESULTS: Overall, 28 (52%) patients were seizure free, with a mean follow-up of 46.5 months. Presence of a focal beta-frequency discharge at seizure onset on scalp EEG predicted seizure-free outcome in lesional (p = 0.02) and non-lesional (p = 0.01) epilepsy patients. At least 90% of patients who had either lesional or non-lesional epilepsy were seizure free if scalp EEG revealed a focal beta discharge at ictal onset. Moreover, logistic regression analysis showed that focal ictal beta pattern and completeness of lesion resection were independently predictive of seizure-free outcome. Ictal onset with lateralized EEG activity of any kind and postresection electrocorticographic spikes did not predict surgical outcome (p > 0.05). CONCLUSIONS: Only about 25% of FLE surgical patients have a focal beta-frequency discharge at seizure onset on scalp EEG. However, its presence is highly predictive of excellent postsurgical seizure control in either lesional or non-lesional FLE surgical patients.

Child↗

PubMedDate not supplied

Aggravation of absence seizures by carbamazepine in a genetic rat model does not induce neuronal c-Fos activation.

The mechanisms underlying carbamazepine aggravation of absence seizures are uncertain but are thought to involve enhancement of neuronal activity within the thalamocortical circuitry. We used c-Fos immunohistochemistry (cFos-ir) to examine patterns of neuronal activation and the relationship to seizure expression following administration of carbamazepine in a rat model of absence epilepsy (Genetic Absence Epilepsy Rats of Strasbourg, GAERS). Female ovariectomized GAERS implanted with extradural EEG electrodes received either 20 mg/kg carbamazepine or vehicle IP. Seizure expression was quantified by measuring the total number and duration of spike-wave discharges (SWD) and with the individual burst discharge lengths over a 90-minute EEG. This was correlated with cFos-ir in thalamocortical slices from rats killed 180 minutes after carbamazepine administration. Carbamazepine-treated rats (n = 5) had a significantly greater total duration of SWD than vehicle-treated rats (17.9% versus 8.8%, P = 0.04). Despite this aggravation of seizures, the level of cFos-ir did not differ between the treatment groups. A positive correlation was found between cFos-ir in the reticularis thalami (Rt) and the total seizure duration (R = 0.66, P = 0.04) and mean burst length (R = 0.68, P = 0.03) but not total number of seizures. The lack of difference in cFos activation patterns between carbamazepine and vehicle-treated animals suggests that the mechanism for carbamazepine aggravation of absence seizures may not involve neuronal activation but rather enhanced neuronal synchronization. The association between increased neuronal activation in the Rt and seizure burden in GAERS provides further support for the critical role of this structure in the maintenance, but not initiation, of absence seizure activity.

Animals↗