Biomedical subjects

Kelly A McNally

Publications and source records attributed to Kelly A McNally.

4 recordsLinked to original sources

PubMed2005

Localizing value of ictal-interictal SPECT analyzed by SPM (ISAS).

PURPOSE: The goal of neuroimaging in epilepsy is to localize the region of seizure onset. Single-photon emission computed tomography with tracer injection during seizures (ictal SPECT) is a promising tool for localizing seizures. However, much uncertainty exists about how to interpret late injections, or injections done after seizure end (postictal SPECT). A widely available and objective method is needed to interpret ambiguous ictal and postictal scans, with changes in multiple brain regions. METHODS: Ictal or postictal SPECT scans were performed by using [99mTc]-labeled hexamethyl-propylene-amine-oxime (HMPAO), and images were analyzed by comparison with interictal scans for each patient. Forty-seven cases of localized epilepsy were studied. We used methods that can be implemented anywhere, based on freely downloadable software and normal SPECT databases (http://spect.yale.edu). Statistical parametric mapping (SPM) was used to localize a single region of seizure onset based on ictal (or postictal) versus interictal difference images for each patient. We refer to this method as ictal-interictal SPECT analyzed by SPM (ISAS). RESULTS: With this approach, ictal SPECT identified a single unambiguous region of seizure onset in 71% of mesial temporal and 83% of neocortical epilepsy cases, even with late injections, and the localization was correct in all (100%) cases. Postictal SPECT, conversely, with injections performed soon after seizures, was very poor at localizing a single region based on either perfusion increases or decreases, often because changes were similar in multiple brain regions. However, measuring which hemisphere overall had more decreased perfusion with postictal SPECT, lateralized seizure onset to the correct side in approximately 80% of cases. CONCLUSIONS: ISAS provides a validated and readily available method for epilepsy SPECT analysis and interpretation. The results also emphasize the need to obtain SPECT injections during seizures to achieve unambiguous localization.

Adolescent↗

PubMed2004

Positive and negative network correlations in temporal lobe epilepsy.

Temporal lobe seizures are accompanied by complex behavioral phenomena including loss of consciousness, dystonic movements and neuroendocrine changes. These phenomena may arise from extended neural networks beyond the temporal lobe. To investigate this, we imaged cerebral blood flow (CBF) changes during human temporal lobe seizures with single photon emission computed tomography (SPECT) while performing continuous video/EEG monitoring. We found that temporal lobe seizures associated with loss of consciousness produced CBF increases in the temporal lobe, followed by increases in bilateral midline subcortical structures. These changes were accompanied by marked bilateral CBF decreases in the frontal and parietal association cortex. In contrast, temporal lobe seizures in which consciousness was spared were not accompanied by these widespread CBF changes. The CBF decreases in frontal and parietal association cortex were strongly correlated with increases in midline structures such as the mediodorsal thalamus. These results suggest that impaired consciousness in temporal lobe seizures may result from focal abnormal activity in temporal and subcortical networks linked to widespread impaired function of the association cortex.

Adolescent↗

PubMed2004

Focal network involvement in generalized seizures: new insights from electroconvulsive therapy.

Generalized seizures are commonly thought to involve the entire brain homogeneously. However, recent evidence suggests that selective cortical-subcortical networks may be crucial for the initiation, propagation, and behavioral manifestations of generalized seizures, while other brain regions are relatively spared. Here we review previous studies, and describe a new human model system for the investigation of generalized seizures: single-photon emission computed tomography, ictal-interictal difference imaging of generalized tonic-clonic seizures induced by electroconvulsive therapy (ECT). Bitemporal ECT activates focal bilateral frontotemporal and parietal association cortex, sparing other regions; bifrontal ECT activates mainly prefrontal cortex; while in right unilateral ECT the left frontotemporal region is relatively spared. Associated midline subcortical networks are also involved. Focal verbal memory deficits parallel the focal regions involved in these neuroimaging studies. Further studies of this kind may elucidate specific networks in generalized tonic-clonic seizures, providing targets for new therapeutic interventions in epilepsy.

Brain Mapping↗

PubMed2003

Targeted prefrontal cortical activation with bifrontal ECT.

The anatomical brain regions involved in the therapeutic and adverse actions of electroconvulsive therapy (ECT) are unknown. Previous studies suggest that bifrontal vs. bitemporal ECT differ in therapeutic efficacy and cognitive side effects. We therefore performed cerebral blood flow (CBF) imaging during bitemporal vs. bifrontal ECT-induced seizures to identify regions crucial for the differences between these treatments. Patients with major depression, undergoing bitemporal or bifrontal ECT, were studied. Ictal-interictal SPECT images were analyzed with statistical parametric mapping for bitemporal (n=11 image pairs in 8 patients) and bifrontal (n=4 image pairs in 2 patients) ECT-induced seizures to identify regions of ictal CBF changes. Bifrontal ECT was found to cause increases in CBF in prefrontal and anterior cingulate regions. Bitemporal ECT, however, caused CBF increases in the lateral frontal cortex and in the anterior temporal lobes. In bifrontal ECT, a greater increase in prefrontal activation, while sparing the temporal lobes, may result in a better therapeutic response and fewer adverse effects on memory than bitemporal ECT.

Cerebrovascular Circulation↗