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

Abstract

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.

Development of Post-Traumatic Epilepsy after Controlled Cortical Impact and Lateral Fluid-Percussion-Induced Brain Injury in the Mouse

“…To further characterize the excitability changes in the brain, mice underwent a PTZ test that is commonly used to test seizure susceptibility or seizure threshold in rodents (Lö scher and Nolting, 1991), and has even shown some predictive value for the localization of an epileptic focus in humans (Wieser et al, 1979;Calcagni et al, 2002).…”

Correlation between Provoked Ictal SPECT and Depth Recordings in Adult Drug‐Resistant Epilepsy Patients

“…In our subjects, the injection of the tracer was performed within 30 s, because ictal SPECTs were obtained during provoked seizures (Calcagni et al, 2002). Recently, the need to obtain early SPECT injections during seizures to achieve unambiguous localization was emphasized in a study of postictal SPECT analyzed with SPM (McNally et al, 2005).…”

“…Provoked ictal SPECT confirmed its efficacy and accuracy in the presurgical evaluation because of the colocalization to the EZ. In a previous study (Calcagni et al, 2002), 22 of 33 patients submitted to provoked SPECT underwent ablative or palliative surgery. It was concluded that this new presurgical diagnostic procedure is safe and noninvasive, has no adverse effects, is inexpensive, and is a readily available clinical tool for localization of epileptogenic foci.…”

“…In our laboratory, provoked ictal SPECT scans were performed. For a detailed description of the procedure, see Calcagni et al (2002).…”

“…Because ictal SPECT is usually performed during spontaneous seizures, it faces technical problems, as it is difficult to obtain spontaneous seizures and to inject as early as possible after the beginning of ictal discharge or the occurrence of the first symptom or both. To resolve these issues, Calcagni et al (2002) performed ictal SPECT during seizures provoked by pentylenetetrazol, a central and respiratory stimulant with epileptogenic effects, thereby demonstrating that this technique is a readily available tool for the localization of the epileptic focus.…”