Diffusion Tensor Imaging

Diffusion is a three-dimensional process and water mobility may be facilitated along one axis of a structure. The measured ADC along this orientation will be larger than in other directions. The directional dependence of diffusion is known as diffusion anisotropy and is especially apparent in brain white matter, in which diffusion mobility is greater along the nerve axon fibers. Along other directions, diffusion is considered as being restricted. The diffusion coefficient is therefore better...

Pathologic Findings In Temporal Lobe Epilepsy

Mesial Temporal Sclerosis Hippocampal Sclerosis Temporal lobe epilepsy is one of the most common medically intractable seizure disorders. Although often the most intractable, the outcome following surgery is best in this group. In such cases 70-80 of patients can expect to have a good seizure outcome seizure free or only occasional seizures 19, 21, 35, 54, 94, 109-124 . Mesial temporal sclerosis is the most common abnormality found in the temporal lobes of these patients 11, 22, 96-100, 125-129...

Info

Collateral Trigone

Sagittal section of the hippocampus. A. Three-dimensional drawing. B. T2-weighted MR image. C. Anatomic section. 1 Hippocampal head, comu ammonis 2 Hippocampal head, gyrus dentatus 1' Hippocampal tail, comu ammonis 2' Hippocampal tail, gyrus dentatus 11 Atrium of the lateral ventricle 12 Temporal horn of the lateral ventricle

Vascular Malformations

Although seizures and epilepsy are frequent presentations of vascular malformations of the brain, these lesions are less common 1-2 among the alien lesions in patients with intractable epilepsy referred to epilepsy surgery. These abnormalities are less frequent in the temporal lobes compared to other regions. Vascular malformations are a heterogenous group of lesions not only from the pathologic viewpoint but also as concerns the mechanisms associated with epilepsy 413-418 . These malformations...

Sclerosis of the Amygdala

Although most of the attention has been given to the hippocampus, we must not forget that the amygdala as well as the temporal pole and entorhinal cortex is also involved in the pathologic process in mesial temporal sclerosis 9, 88, 115, 127 . The amygdala sits on top of the hippocampal head at the level of the anterior commissure and it can be problematic to separate the hippocampal head from the lateral amygdaloid nucleus at that level 226 . As pointed by Jack et al. 208, 265 ,...

C

Pacemaker Zone Epileptogenic Region Epileptogenic Lesion FIG. 1.3. Cont'd. C. With a similar lesion, the electrophysiological data do not include the epileptogenic lesion, and the epileptogenic region is only at the margin of the lesion. D. The idealized case of mesial temporal epilepsy where there is left hippocampal sclerosis and good concordance between the pacemaker zone and the lesion and the epileptogenic region is well localized to this area. E. In another patient with left temporal lobe...

Magnetic Resonance Evidence of Seizureassociated Injury

Extracellular Edema Photos

Several MR sequences have been shown to be sensitive to acute seizure-induced changes for review see reference 197 . The initiation of cytotoxic edema restricts the free diffusion of water in the reduced volume of the extracellular space. This can be detected as an increase in the signal intensity of diffusion-weighted images or quantitatively by a reduction in the diffusivity a parameter that reflects the freedom of diffusion . The subsequent progression to vasogenic edema will result in...

How Imaging Has Helped Understanding Of The Epileptogenic Processes In Temporal Lobe Epilepsy

The Origins of Hippocampal Sclerosis Some facts about HS are undoubted. The histopathologic and MR features of this lesion have been recognized and are well described. The epileptogenic properties of this lesion have also been investigated. There is a broad consensus that HS is epileptogenic and that removal of this structure has a high chance of rendering the patient seizure-free. The clinical pattern of the epilepsy associated with HS has been described, and there has been some controversy...

Magnetic Resonance Imaging Of Temporal Lobe Epilepsy

Temporal Lobe Scar

Commissions of the International League Against Epilepsy Recommendations The Commission on Neuroimaging of the International League against Epilepsy ILAE 181, 182 recommends that i n the non-acute situation, the ideal practice is to obtain structural neuroimaging with MRI in all patients with epilepsy, except in patients with a definite electroclinical diagnosis of idiopathic generalized epilepsy benign myoclonic epilepsy of infancy, childhood absence epilepsy, juvenile absence epilepsy,...

Signal Changes In Epilepsy

Temporal Lobe Abnormalities

This is a severe example of signal change in the anterior temporal lobe and temporal pole. The T2-weighted image A shows high signal in the temporal white matter, in this case even greater than the gray matter long arrow . The heavily T1 -weighted IR sequence B shows decreased signal in temporal white matter. Abnormal signal is also in the atrophic hippocampus and was proved to be typical hippocampal sclerosis. There was no developmental abnormality in the resected temporal lobe....

Histopathologic Evidence of Seizureassociated Damage

Status Epilepticus Dog

The presence of seizure-associated damage has been documented in the histopathologic literature on animals and humans for review see reference 447 . In experimental studies, neuronal damage was most extensive in animals experiencing generalized convulsive status epilepticus, but was also found to a lesser degree after single short seizures. Neurons show selective vulnerability to the effects of status epilepticus the hippocampus is particularly vulnerable. Several factors have been associated...

Nb5i

Simple Partial Epilepsy

Photomicrograph showing hippocampal dysplasia with a collection of abnormal cells large arrow in the hippocampus peripheral to the dentate gyrus labeled in the striatum lacunosum moleculare radiata. B. Photomicrograph showing mesial temporal dysplasia with abnormal structure of cellular and sparse areas in the entorhinal region. This area normally has an unusual microarchitecture, but this structure is abnormal. C. Hippocampal dysplasia where there are abnormal cells in the...

References

Inferior Frontal Gyrus Anatomy

Surface, Blood Supply and Three-dimensional Sectional Anatomy, 2nd edn, New York Springer Verlag Wien, 1991. 2. Amaral DG, Campbell MJ. Transmitter systems in the primate dentate gyrus. Hum Neurobiol 1986 5 169-180. 3. Amaral DG, Witter MP. The three-dimensional organization of the hippocampal formation a review of anatomical data. Neuroscience 1989 3 571-591. 4. Angevine JB. Development of the hippocampal region. In Isaacson RL, Pribram KH, eds. The...

Clinical Features Of Temporal Lobe Epilepsy

The Temporal Lobe Development and Functions The temporal lobe is one of the last areas of the cortex to mature Table 4.1 . 50 of temporal lobes are myelinated at management. There are now attempts to include these data by considering the data available along a number of major axes. This is discussed in detail in Chapter 1. Temporal Lobe Epilepsy The Clinical Problem 80 weeks 1 . The temporal lobes are important for memory, hearing, and language, among other things. As Gloor has said, To be...

Neoplasms Astrocytic Tumors

Astrocytic Tumors

Bruton reported that astrocytic tumors constituted 3.6 of the total sample of patients and 18 of those with alien lesions. These lesions may present as discrete masses or as more extensive lesions. Interestingly, Bruton reported that most cases were pathologically localized and involved the parahippocampal gyrus and the amygdala. The histologic type consisted of predominantly fibrillary astrocytomas but protoplasmic type astrocytic tumors were also observed. It is difficult to compare the...

Brl

Jelly Roll Hippocampus

Coronal MR slices of a patient with postictal psychosis PIP left sides and a patient without postictal psychosis right sides . Both patients have left-sided hippocampal sclerosis. The arrows point to the ipsilateral hippocampus. B. The graphs demonstrate the posterior-to-anterior distribution of the hippocampal volume of the same two patients. The ipsilateral open squares and contralateral side black squares are expressed as a function of the slice position. In the posterior...

Graeme D Jackson Ruben I Kuzniecky and Samuel F Berkovic

John Hughlings Jackson

Today, epilepsy has more secrets to confide to the neurologist or neurosurgeon who can understand the 'tongue' she speaks.'' The origin of the modern view of epilepsy is generally considered to have been the studies and work of John Hughlings Jackson Fig. 1.1 . He was appointed assistant physician to the National Hospital for the Relief and Cure of the Paralysed and Epileptic now the National Hospital for FIG. 1.1. John Hughlings Jackson, London 1835-1911 . FIG. 1.1. John Hughlings Jackson,...

Signal

Sagittal Brain Mri Hippocampus

Increased T2-weighted signal intensity Decreased T1-weighted signal intensity FIG. 4.11. Parasagittal image showing the indentations of the dentate at the inferior border of the hippocampus. In very thin slices this can give apparent asymmetry. axial Fig. 4.10D , coronal Fig. 4.10E and parasagittal Fig. 4.10F orientation are shown. Note that the whole length of the hippocampus can be seen in a single axial slice. In some circumstances these can be very important images. The hippocampal axis is...

Inplane Spatial Resolution

The in-plane spatial resolution is determined by the matrix size and the size of the FOV that is how many voxels we divide the area we are imaging into. A typical matrix in clinical practice is 256 x 256, which means that the whole image is divided, in two dimensions, into an array of this many compartments or picture elements pixels . The actual size of the pixels will depend on the FOV. If we know the third dimension of the slice thickness as well we can determine the voxel volume, i.e. the...

Superior Occipital Gyrus

Transverse Temporal Gyrus

Frontal pole, anterior aspect. 3,3' Middle frontal gyrus F2 , superior and inferior parts 4 Middle frontal sulcus reaching 5 5 Frontomarginal sulcus 6,6',6 Superior, middle, and inferior transverse frontopolar gyri 7 Frontomarginal gyrus FIG. 3.8. Lateral aspect of the right frontal lobe. 3 Inferior postcentral sulcus ascending portion 4' Posterior subcentral sulcus 4 Anterior subcentral sulcus 5 Lateral fissure, middle segment 6 Lateral fissure, anterior segment a vertical and b...

Parahippocampal Gyrus Abnormalities

Parahippocampal Gyrus Mri

Other indirect features of mesial sclerosis commonly seen in these patients are the presence of parahippocampal gyrus atrophy and sometimes signal change. These changes are difficult to visualize but with optimized images one can evaluate the presence of thinning of the underlying white matter and blurring of the gray white matter pattern. This usually depends on having images that assess signal change well Fig. 4.41 . Similarly, changes of the collateral white matter, which is located between...

Indusium Griseum

Hippocampus Tail

Intraventricular aspect of the right hippocampus. The temporal horn of the lateral ventricle has been opened and the choroid plexuses have been removed. FIG. 3.18. Intraventricular aspect of the right hippocampus. The temporal horn of the lateral ventricle has been opened and the choroid plexuses have been removed. 2 Hippocampal head digltationes hippocampi 6 Splenium of the corpus callosum 7 Calcar avis in the occipital horn 10 Uncal recess of the temporal horn the amygdala...

Table 45 MRI Characteristics of Astrocytic Neoplasms

Tumor Posterior Temporal Lobe

adult Homogeneous intensity Variable adult Cystic Demarcated Common dense adult Heterogeneous Common irregular Oligodendrogliomas are histologically characterized by the presence of compact groups of large, rounded cells with empty cytoplasm Fig. 4.65 . In almost half the cases, the tumors are mixed with glial components. Calcifications are frequent, with calcium deposits in the intrinsic blood vessels 393, 397-399 . These tumors are less frequent than astrocytomas and also infrequent in our...

Hippocampal Dysplasia

Hippocampal dysplasia is a nonspecific term that is used to mean a developmental abnormality of the hippocampus see Chapter 6 for a full discussion of malformations of cortical development . In this context it is defined by the presence of distinct architectural and cellular abnormalities in the hippocampus. Although there is debate as to what the role of development is in the origins of HS, we do not include HS as dysplasia. We include hippocampal dysplasia here because of the imaging issues,...

Coronal Sections Of The Hippocampus

Hippocampus And Optic Tract

The coronal views show eight sections moving progressively from anterior to posterior levels. FIG. 3.24. Coronal section of the hippocampal head. A. Three-dimensional drawing. B. T1 -weighted MR image. C. Anatomic section posterior view . FIG. 3.24. Coronal section of the hippocampal head. A. Three-dimensional drawing. B. T1 -weighted MR image. C. Anatomic section posterior view . 1 Anterior apex of the hippocampal head cornu ammonis 2' Amygdala, lateral nucleus 2 Amygdala, basal nucleus 2'...

List of Contributors

Brain Research Institute, Melbourne, Victoria, Australia A. James Barkovich, M.D. Department of Radiology, Neuroradiology Section, University of California San Francisco, San Francisco, CA, USA Samuel F. Berkovic, M.D. Epilepsy Research Collaborative Centre, University of Melbourne, Melbourne, Victoria, Australia Andrea Bernasconi, M.D. Montreal Neurological Institute, McGill University, Montreal, Qu bec, Canada Jeffrey R. Binder, M.D. Department of Neurology, Medical...

Jex

Relaxometry

Measurement of T2-relaxometry times T2 relaxometry was acquired with a CPMG sequence with eight images per location 7 e 29-231 ms, TR 5000ms on a 3T GE LX Horizon scanner Milwaukee, USA . A. All eight acquired images are shown, with echo times between 29 and 231 ms, on one slice at the level of the hippocampus. Note the changing brightness of the images, reflecting the T2 decay. In the region within the red circle, the signal was measured on each image. This decay is shown...

Observing Hippocampal Sclerosis Development

Hippocampal Sclerosis

Acute Changes in Patients with Epilepsy Progressing to Hippocampal Sclerosis The presence of short-term, seizure-associated changes is an important issue. There is debate about whether seizures cause damage to the brain or whether all or a portion of the abnormalities seen in the brains of patients with epilepsy are due to pre-existing factors. A change in T2 relaxometry after a seizure would favor the idea that seizure-associated damage can occur. An early study suggested that recent seizures...