Lezak Neuropsychology

Posted on December 07, 2011 by Admin
Lezak Neuropsychology

Lezak Neuropsychology

Early History

Structural brain imaging began with early radiographic techniques to view the human brain. In 1918 American neurosurgeon Walter Dandy introduced ventriculography as a method of brain imaging by injecting filtered air directly into the lateral ventricles of the brain after drilling small holes into the skull. Later Dandy developed a process known as pneumoencephalography which consisted of radiography of fluid-containing structures of the brain after cerebrospinal fluid was withdrawn by a lumbar puncture and replaced by a gas. Both procedures carried risks and could be quite painful (White, Bell, & Mellick, 1973). Cerebral angiography was introduced in the late 1920’s by neurologist Egas Moniz. This technique injected positive contrast substances into the cerebrovasculature and resulted in good visualization of the vasculature of the brain, but similarly carried risks due to the nature of the contrast substances used at that time. However safer contrast measures were developed and cerebral angiography remains an important tool in neurosurgery.

More Recent Developments

While early techniques to visualize the brain held promise for treatment, these techniques did not allow for identification of lesion location in the brain or specific diagnosis and this assessment was primarily left up to behavioral methods. With the development computerized axial tomography (CT or CAT scans) in the 1970’s more detailed anatomic images of the brain became available. This technique also helped eliminate the need for purely behavioral techniques as the only methods to identify lesion location (as it turns out behavioral methods are often not accurate in identifying lesion location in the brain).

MRI

Other structural imaging techniques such as magnetic resonance imaging (MRI) were developed without the need for ionizing or x-rays and instead relied on signal variations created by protons in the brain when the head is placed in a magnetic field. These techniques allowed for greater resolution in the images they produced. The explosion of structural brain imaging techniques led to advancements in the diagnosis of brain pathology that would have nearly impossible a decade earlier using purely behavioral assessments. Physicists have also developed other MRI-based techniques such as diffusion tensor imaging to map white matter tracts in the living brain. The clinical benefits of mapping white matter tracts within the brain are just now being realized.