Comparative study of interictal PET and ictal SPECT in complex partial seizures

Area of Science:

• Neurology
• Nuclear Medicine
• Epilepsy Research

Background:

• Medically intractable complex partial seizures (MI-CPS) often require surgical intervention.
• Accurate localization of the epileptogenic focus is critical for successful epilepsy surgery.
• Magnetic Resonance Imaging (MRI) can be normal in a significant proportion of patients with MI-CPS.

Purpose of the Study:

• To compare the diagnostic sensitivity of ictal technetium-99m-labeled hexamethylpropyleneamine oxime (99mTc-HMPAO) single photon emission computed tomography (SPECT) with interictal fluorine-18-fluorodeoxyglucose positron emission tomography (FDG-PET).
• To evaluate the utility of these neuroimaging modalities in localizing the epileptogenic focus in patients with MI-CPS.

Main Methods:

• Retrospective analysis of 67 patients (38 female, 29 male) with MI-CPS who underwent anterior temporal lobectomy.
• Interictal FDG-PET was assessed for focal hypometabolism.
• Ictal 99mTc-HMPAO SPECT was evaluated for focal perfusion abnormalities (hyperperfusion or hypoperfusion).

Main Results:

• In 36 patients with both studies, PET showed hypometabolism in 32, while ictal SPECT demonstrated hyperperfusion in 27 and hypoperfusion in 7.
• The sensitivity of ictal SPECT was 34/36 and interictal PET was 32/36; the difference was not statistically significant (P = 0.67).
• The two imaging techniques were complementary in six patients, providing additional localizing information.

Conclusions:

• Ictal SPECT and interictal PET demonstrate equal sensitivity and reliability in localizing the epileptogenic focus in MI-CPS.
• These functional neuroimaging techniques play a vital role in localizing the seizure focus, particularly in MRI-negative cases.
• Their use can facilitate surgical resection, potentially avoiding the need for more invasive electrographic monitoring.