The features of medical techniques in detail

We suggest watching these two videos in which some professionals explain in depth how the diagnostic techniques we have just spoken about work and what they are useful for.

If you do not have access to youtube or if you prefer not to watch the videos, each one is preceded by a short description.

In the video below you can see two epilepsy experts at the Beth Israel/Roosevelt Hospital, Patty McGoldrick and Steve Wolf, illustrating the best medical procedure to investigate the brain functioning underlying epilepsy. This is necessary before a surgical intervention to understand whether the patient is a good candidate for surgery. Video EEG looks for abnormal electricity of the brain through electrodes to specifically localize the seizure focus. The patient’s behaviour is simultaneously recorded in order to associate physical symptoms to their atypical observed neural substrates. Instead, MRI is used to identify the structural problems of the brain linked to epilepsy. In the case of discrepancy between video EEG and MRI, when a localized abnormal electricity is found but there are no structural damages in the same area, a PET scan may help to solve it. For example, the discovery of “cold spaces”, representing metabolic abnormalities, confirms the video EEG results. It is quite frequent that these tests converge. Before the surgical intervention “safety tests”, like fMRI and WADA, are used to map the specific brain areas associated to peculiar cognitive functions, such as memory and language, with the aim of not damaging them. The patients are asked to do some tasks, like counting and moving their fingers, to make doctors define the lateralization of language and of memory. Nowadays, fMRI is preferred because it is a non-invasive technique.

The following video shows a patient undergoing a WADA test, conducted by Dr. Yoshihide Wada, University of British Columbia. The aim of this procedure is to find the lateralization of cognitive functions in the patient’s brain. Through the left or right carotid artery, a barbiturate is injected in both hemispheres (one at a time) which silences the cognitive functions located there. The procedure requires the patient to begin counting or moving his/her hands before the injection, so the doctor can see whether these tasks are interrupted by the barbiturate and confirm that the anaesthetised hemisphere is responsible for the disrupted function. Although in 90% of people language is left-lateralized, it might be localized in the right hemisphere or in both. Both the WADA test and, more recently, the fMRI are used in surgical interventions to avoid damaging or removing the brain area responsible for speech.