in diagnostic imaging of epilepsy
Dr. Ruben Kuzniecky
of Alabama-Birmingham, AL,
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
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.