Effect of injection time on postictal SPET perfusion changes in medically refractory epilepsy

Avery, R. A.; Spencer, S. S.; Mv, Spanaki; Corsi, María; Jp, Seibyl; Ig, Zubal

doi:10.1007/s002590050456

Cited by 43 publications

(24 citation statements)

References 22 publications

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“…In 6/33 drug-resistant epileptic patients (18%), the hypo-hyperperfusion scintigraphic pattern was not found (patients [28][29][30][31][32][33]. In all these patients, brain SPET showed an area of hypoperfusion on both interictal and ictal studies.…”

Section: Resultsmentioning

confidence: 97%

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Ictal brain SPET during seizures pharmacologically provoked with pentylenetetrazol: a new diagnostic procedure in drug-resistant epileptic patients

et al. 2002

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Functional brain imaging plays an important role in seizure focus localisation. However, truly ictal single-photon emission tomography (SPET) studies are not routinely performed owing to technical problems associated with the use of tracers and methodological and logistical difficulties. In this study we tried to resolve both of these issues by means of a new procedure: technetium-99m ethyl cysteinate dimer (ECD) brain SPET performed during seizures pharmacologically provoked with pentylenetetrazol, a well-known central and respiratory stimulant. We studied 33 drug-resistant epileptic patients. All patients underwent anamnestic evaluation, neuropsychological and psychodynamic assessment, magnetic resonance imaging, interictal and ictal video-EEG monitoring, and interictal and ictal SPET with (99m)Tc-ECD. In order to obtain truly ictal SPET, 65 mg of pentylenetetrazol was injected every 2 minutes and, immediately the seizure began, 740 MBq of (99m)Tc-ECD was injected. The scintigraphic findings were considered abnormal if a single area of hyperperfusion was present and corresponded to the site of a single area of hypoperfusion at interictal SPET: the "hypo-hyperperfusion" SPET pattern. In 27 of the 33 patients (82%), interictal-ictal SPET showed the hypo-hyperperfusion SPET pattern. Video-EEG showed a single epileptogenic zone in 21/33 patients (64%), and MRI showed anatomical lesions in 19/33 patients (57%). Twenty-two of the 27 patients with hypo-hyperperfusion SPET pattern underwent ablative or palliative surgery and were seizure-free at 3 years of follow-up. No adverse effects were noted during pharmacologically provoked seizure. It is concluded that ictal brain SPET performed during pharmacologically provoked seizure provides truly ictal images because (99m)Tc-ECD is injected immediately upon seizure onset. Using this feasible procedure it is possible to localise the focus, to avoid the limitations due to the unpredictability of seizures, to avoid pitfalls due to late injection, to avoid intracranial EEG recording and to minimise costs. The clinical value of our method is confirmed by the good outcome after 3 years of follow-up in those patients submitted to ablative or palliative surgery.

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Section: Resultsmentioning

confidence: 97%

“…Only when the tracer is injected at that time does ictal SPET demonstrate the highest accuracy in localising the focus, as compared with postictal and interictal SPET [28,31,32,33]. In patients with short and well-localised seizures, delayed injection may fail to produce a hyperperfusion image.…”

Section: Discussionmentioning

confidence: 99%

Ictal brain SPET during seizures pharmacologically provoked with pentylenetetrazol: a new diagnostic procedure in drug-resistant epileptic patients

et al. 2002

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“…We and others have previously looked at the perfusion changes of short versus long seizures and noted that a return to baseline levels can occur more quickly for very short seizures (25). Likewise, for times later than 100 seconds after seizure onset, perfusion decreases of approximately 50% are noted and can persist for many minutes (26). Although it is not fully known how long after a seizure episode the perfusion (and metabolism) alterations persist, the ratio-images presented here are a result of interictal scans conducted after 24 hours of seizure-free activity.…”

Section: Discussionmentioning

confidence: 95%

Ratio‐Images Calculated From Interictal Positron Emission Tomography and Single‐Photon Emission Computed Tomography for Quantification of the Uncoupling of Brain Metabolism and Perfusion in Epilepsy

2000

Epilepsia

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Summary:Purpose: Image processing techniques were applied to interictal positron emission tomography (PET) and single-photon emission computed tomography (SPECT) brain images to aid in the localization of epileptogenic foci by calculating a functional image that represents the degree of coupling between perfusion and metabolism. Uncoupling of these two functions has been demonstrated to be a characteristic of epileptogenic tissue in temporal lobe epilepsy and has the potential to serve as a diagnostic measure for localization in other areas as well.Methods: Interictal PET ( 18 F-FDG) and interictal SPECT ( 99m Tc-HMPAO) scans were acquired from 11 epilepsy patients. The metabolism and perfusion images were threedimensionally spatially registered, and a functional ratio-image was computed. These functional maps are overlaid onto a threedimensional rendering of the same patient's magnetic resonance imaging anatomy.Results: In all patients, an average uniform perfusion-tometabolism ratio showed approximately constant values throughout most of the whole brain. However, the epileptogenic area (confirmed on surgery) demonstrated an area of elevated perfusion/metabolism in the grey matter.Conclusions: Although hypometabolism in the PET image was observed in most of these patients, the calculation of a functional ratio-image demonstrated localized foci that in some cases could not be observed on the PET image alone. The ratio-image also yields a quantitative measure of the uncoupling phenomenon.

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“…Recent data suggests that if the seizure discharge lasts more then 100 seconds, then the pattern of perfusion becomes 'postictal' despite continuation of the discharge [19].…”

Section: The Ictal Phasementioning

confidence: 99%

“…A large body of evidence closely links the two in normal physiological situations, but there is some reason to doubt that the link is inviolate during seizures, where energy demand is so far in excess of that seen in physiological situations. Recent evidence has suggested that ictal hyperperfusion will only continue for a certain period of time in some brain regions, even if the ictal discharge carries on [19], again suggesting that perfusion declines relative to the level of neuronal activity.…”

Section: Ictal and Postictal Rcp Spect -Their Use In Localising Seizuresmentioning

confidence: 99%

SPECT in Focal Epilepsies

Duncan

2000

Behavioural Neurology

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Brain perfusion changes during seizures were first observed in the 1930s. Single Photon Emission Computed Tomography (SPECT) was developed in the 1970s, and tracers suitable for the imaging of regional cerebral perfusion (rCP) became available in the 1980s. The method was first used to study rCP in the interictal phase, and this showed areas of low perfusion in a proportion of cases, mainly in patients with temporal lobe epilepsies. However, the trapping paradigm of tracers such as hexamethyl propyleneamine oxime (HMPAO) provided a practicable method of studying changes in rCP during seizures, and a literature was established in the late 1980s and early 1990s showing a typical sequence of changes during and after seizures of mesial temporal lobe origin; the ictal phase was associated with large increases in perfusion throughout the temporal lobe, with first the lateral, then the mesial temporal lobe becoming hypoperfused in the postictal phase. Activation and inhibition of other structures, such as the basal ganglia and frontal cortex, were also seen. Studies of seizures originating elsewhere in the brain have shown a variety of patterns of change, according to the structures involved. These changes have been used practically to aid the process of localisation of the epileptogenic zone so that epilepsy surgery can be planned.Some neuroreceptors (e.g. benzodiazepine receptors) can be studied using SPECT, and have shown localised abnormalities. SPECT has also been used to study brain function during the intracarotid amytal test. SPECT images of all kinds can be analysed using numerical techniques such as statistical parametric mapping, and such techniques promise to improve the yield of information from ictal studies.

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Effect of injection time on postictal SPET perfusion changes in medically refractory epilepsy

Cited by 43 publications

References 22 publications

Ictal brain SPET during seizures pharmacologically provoked with pentylenetetrazol: a new diagnostic procedure in drug-resistant epileptic patients

Ictal brain SPET during seizures pharmacologically provoked with pentylenetetrazol: a new diagnostic procedure in drug-resistant epileptic patients

Ratio‐Images Calculated From Interictal Positron Emission Tomography and Single‐Photon Emission Computed Tomography for Quantification of the Uncoupling of Brain Metabolism and Perfusion in Epilepsy

SPECT in Focal Epilepsies

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