Advances in diagnostic imaging of epilepsy

Dr. Ruben Kuzniecky
University of Alabama-Birmingham, AL,
USA

Abstract:    The impact of new neuroimaging techniques in the investigation and treatment of patients with epilepsy has been enormous and parallels the introduction of EEG in epilepsy 50 years ago.  With the development of MRI and its application to epilepsy, major shifts in the conceptual framework of epilepsy classification and management have taken place. It is now over a decade ago that MRI was shown to be sensitive in the identification of medial temporal sclerosis.  This allowed for the first time, the identification of medial temporal lobe pathology of the most common epileptic substrate in intractable temporal epilepsy.  The development of new MRI based techniques has improved the sensitivity for the diagnosis of MTS to approximately 95%.  Similarly, the detection of developmental abnormalities causing epilepsy has had a major impact in the investigation of patients with extra-temporal seizures.  In spite of these advances. over half the patients with extra-temporal lobe seizures do have a normal MRI.  Efforts to increase the sensitivity and specificity of MRI have included surface coils, high-resolution imaging. post-processing techniques, etc.

Functional imaging techniques such as SPECT, PET, FMRI, and MR spectroscopy provide complementary information to MRI.  However in patients without evidence of structural pathology, these functional imaging techniques become important for localization.  Ictal SPECT in particular has become a very useful technique in patients than have otherwise no abnormalities on MRI studies and have poor localization by EEG.  Ictal SPECT is often available in most hospitals since these units are used for other purposes.  More recently, MSI or magnetic source imaging based on MEG and co-registration with MRI has been developed for clinical use.  MIS has the potential for accurate dipole localization and for functional mapping in a relatively easy setup.

Although new techniques are rapidly developing, the cost of implementing new imaging modalities is also escalating rapidly. Future studies should concentrate on the rational utilization of neuroimaging techniques in epilepsy and on the development of non invasive and reliable techniques for localization.