Degeneration of the brainstem.

Magnetic resonance imaging (MRI) is the most sensitive imaging technique for assessing brainstem involvement in neurodegenerative diseases. An MRI can assess the degree of atrophy of the brainstem and alterations in signal intensity on T2-weighted images in the affected areas, which are the main imaging findings found in these diseases. Besides, diffusion-weighted MRI and proton MR spectroscopy are tools that play an important role in the characterization of these entities.

Hippocampal sclerosis: histopathology substrate and magnetic resonance imaging.

The term hippocampal sclerosis was originally used to describe a shrunken and hardened hippocampus, which histologically displayed neuronal loss and glial proliferation. These alterations are mainly located in the hilus of the dentate gyrus and in the CA1 and CA3 pyramidal cell layers but all hippocampal regions may show neuronal cell loss to varying degrees. A number of morphologic and cytochemical findings are associated with mesial temporal sclerosis, especially within the dentate gyrus.

Macroanatomy and microanatomy of the temporal lobe.

Because of its different functions and organization, the temporal lobe may be divided into lateral and medial parts. This separation may be useful for teaching purposes, since the medial temporal lobe needs a separated and a more precise study because of its complex structure and because it is the substrate where some specific types of epilepsy originate. The use of certain magnetic resonance imaging (MRI) sequences and protocols has improved the diagnosis of some particular epilepsies, but this technical benefit must be accompanied by the accurate knowledge of the anatomy of the temporal lobe.