History of Neuroimaging - Early Uses of Brain Imaging

Early Uses of Brain Imaging

The desire to understand the human mind has been one of the main desires of philosophers throughout the ages. Questions about thoughts, desires, etcetera have drawn psychologists, computer scientists, philosophers, sociologists and the like together into the new discipline of cognitive science. Non-invasive imaging of the human brain has proven invaluable in this context.

Structural imaging began with early radiographic techniques to image the human brain. Unfortunately, because the brain is almost entirely composed of soft tissue that is not radio-opaque, it remains essentially invisible to ordinary or plain x-ray examination. This is also true of most brain abnormalities, though there are exceptions such as a calcified tumour (e.g.meningioma, craniopharyngioma, some types of glioma); whilst calcification in such normal structures as the pineal body, the choroid plexuses, or large brain arteries may indirectly give important clues to the presence of structural disease in the brain itself.

In 1918 the American neurosurgeon Walter Dandy introduced the technique of ventriculography whereby images of the ventricular system within the brain were obtained by injection of filtered air directly into one or both lateral ventricles of the brain via one or more small trephine holes drilled in the skull under local anaesthesia. Though not usually a painful procedure, ventriculography carried significant risks to the patient under investigation, such as haemorrhage, infection, and dangerous changes in intracranial pressure. Nevertheless the surgical information given by this method was often remarkably precise and greatly enlarged the capabilities and accuracy of neurosurgical treatment. Dandy also observed that air introduced into the subarachnoid space via lumbar spinal puncture could enter the cerebral ventricles and also demonstrate the cerebrospinal fluid compartments around the base of the brain and over its surface. This technique was called pneumoencephalography. It further extended the scope for precise intracranial diagnosis, but at a similar cost of risks to the patient as well as being, in itself, a most unpleasant and often painful ordeal.