By localizing the portion of the brain responsible for seizures and envisioning long-term outcomes, this imaging combination helps guide clinical decision making.
A combination of ictally subtracted single photon emission tomography (iSPECT) and F-18 fluorodeoxyglucose positron emission tomography (FDG-PET) can help localize the portion of the brain responsible for epileptic seizures and predict long-term outcomes after epilepsy surgery, according to a new study.
“Concordance between noninvasive investigations iSPECT and FDG-PET is an important predictive factor for surgical outcomes in extra-temporal epilepsy,” stated the researchers led by Manjari Tripathi, MD, of Department of Neurology, CN Centre, All India Institute of Medical Sciences, Ansari Nagar, New Delhi, India.
Noninvasive techniques provide information for the localization of the epileptic focus in the majority of epilepsy. Recently, noninvasive neuroimaging techniques-such as simultaneous recording of functional MRI and electroencephalography (EEG-fMRI), PET, SPECT, electric and magnetic source imaging, and spectroscopy-have proved their usefulness in defining the epileptic focus.
The combination of these functional techniques can yield complementary information, and their concordance is crucial for guiding clinical decisions, such as the planning of invasive EEG recordings or respective surgery.
Imaging tools, such as MRI and computed tomography, are now recommended for all patients with epilepsy. However, sometimes no lesion is visualized on MRI in patients with location-related epilepsy and further neuroimaging is required for presurgical evaluation.
Dr Tripathi and colleagues prospectively evaluated 74 patients, mean age 19 years, who were undergoing surgery for temporal or extratemporal drug-refractory epilepsy and had at least 5 years follow up. The mean age of onset of seizures was about 10 years. Patients with MRI and video EEG concordance for the seizure focus underwent iSPECT and FDG-PET.
“When both FDG-PET and iSPECT were concordant with each other, this translated into an outcome of 62% for extratemporal epilepsies, provided they were also concordant with the lesion, as defined by MRI and video EEG,” the researchers stated.
This result was significant when compared with both FDG-PET/iSPECT not concordant with MRI/video EEG and only PET or iSPECT concordant with MRI/video EEG.
This correlation was not found for temporal epilepsies, where the MRI and video EEG provided the most important prognostic parameters, they noted.
“In both temporal and extratemporal epilepsies the concordance of the iSPECT/FDG-PET with the MRI/video EEG correlated with a better 5-year outcome,” the researchers stated.
Surgery is an option for patients with epilepsy who do not respond to medications or cannot tolerate the adverse effects. Surgery is considered only when the area to be removed is not responsible for critical functions.
“(SPECT) is a very useful technique in cases in which seizures are difficult to localize with an EEG or in which a patient’s MRI is normal,” said Jorge AsconapÃ©, MD, Professor in the Department of Neurology at Loyola University Medical Center, Maywood, IL, who specializes in epilepsy.
In addition, new software allows for 3-D modeling of the epileptogenic zone, he added.
The researchers published their results in the December 2014 issue of Epilepsy Research.