الفهرس 
IntroductionOnly 14 pages are availabe for public view
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Abstract
Epilepsy is one of the most common disorders of the brain. One of every ten people will have at least one epileptic seizure during a normal lifespan, and a third of these will develop epilepsy. Worldwide, epilepsy affects 50 million people. In adults, Temporal Lobe Epilepsy (TLE) represents the most frequent form of localization related epilepsy. The most common cause of temporal lobe epilepsy is hippocampal sclerosis. About 30% of the patients are refractory to conventional anti-epileptic drugs and many experience side effects such as sedation and cognitive impairment. The majority of patients suffer from complex partial seizures, which have been shown to originate in many cases in the mesial temporal lobe structures, particularly in the hippocampal-amygdaloid region. Patients with medically uncontrolled partial seizures are possible candidates for surgery so the seizure focus must be correctly lateralized. EEG, video EEG, structural and metabolic imaging are used for lateralization. Preoperative MRI also is used to screen for the so called dual pathology, in which additional extrahippocampal lesions that are present in approximately 15% of patients diminish postsurgical prognosis unless the second lesion is also resected. MRI is the imaging procedure of choice for patients with epilepsy. It is useful in detecting several cerebral abnormalities related to epilepsy in adults and children, including MTS, tumors, and developmental malformations. MRS shows abnormal metabolite ratios even in MR negative patients. The most sensitive ratio is the NAA/Cho+Cr ratio. MRS can detect abnormal metabolite ratios in the affected temporal lobe concordant with the EEG lateralization with greater accuracy than conventional MRI. Diffusion tensor imaging (DTI) is a relatively new non-invasive imaging technique that allows for the detection and examination of composition, integrity, and orientation of discrete white matter fiber bundles not optimally evaluated with conventional magnetic resonance imaging (MRI). Brain fiber tractography allows depiction of white matter tracts, and comparison between normal and diseased fibers tracts enables quantification of white matter changes due to damage. DTI and tractography have been applied to the study of epilepsy and have demonstrated diffusion changes in gray and white matter tissue. Evaluation of white matter tracts connecting these various regions may provide useful information as to the diffuse changes in the brain that accompany TLE. Applications of DTI and tractography in the TLE patient population have focused on improved characterization (or detection) of the associated hippocampus pathology and understanding the impact of TLE on extrahippocampal white matter connectivity. Voxel-based morphometry (VBM) was originally developed to detect differences in brain morphology between two more groups of subjects, is a fully automated computerized quantitative magnetic resonance (MR) image analysis technique that does not rely on investigator expertise in neuroanatomy and is not restricted to the study of one brain region at a time. Although MTS may be evidenced in conventional MRI as hippocampal atrophy and abnormal signal characteristics, pathologic studies of MTS illustrated that damage and volume losses are not confined to the hippocampus but involve the amygdala and parahippocampal regions, and often extend to extratemporal cortical regions and subcortical structures as well. The damage to regions outside the hippocampus and amygdala are subtle and complex, and they are consequently not easily detectable with conventional MRI. VBM has illustrated that pathology in TLE extends beyond the mesiotemporal structures such as the frontal regions, cingulum, and thalamus. Therefore, VBM may help elucidate some unresolved important research questions such as how recurrent temporal lobe seizures affect hippocampal and extrahippocampal morphology using serial imaging acquisitions. Partial removal of the anterior temporal lobe (ATL) is the most commonly performed surgical procedure for intractable epilepsy. ATL resection is highly effective for seizure control, resulting in long-term cure rates of 60–80%. The undeniable benefit of ATL surgery is partially offset by the occurrence of neuropsychological morbidity in some patients receiving this treatment. Evidence suggests a 30–60% incidence of anomic aphasia and a similar risk for decline in verbal memory ability after left ATL surgery. Patients are generally aware of these deficits, which adversely affect quality of life and employability. fMRI help localizing the precise epileptic focus and structure involved in seizure activity, as well as prediction of language lateralization, naming outcome and verbal memory outcome which helps to accurately define the resected parts to avoid recurrence of seizures and at the same time minimize morbidity by avoiding removal of unaffected structures. MR Perfusion imaging is suited for detection the source of seizures that may remain undetected by traditional methods. It could be of benefit by targeting physiologic alterations, together with other techniques as MRS, Diffusion and Functional MRI. Other goals include preoperative planning for language or memory lateralization and assessing damage resulting from refractory seizures.