When examining the brain and nerves, various neuropsychological tests may be required as well as imaging procedures, which include MRI and CT, for example. Measurements of brain waves or the speed of nerve conduction may also play a role in the diagnosis. We present various examinations.
Neuropsychological examination
Further part of the neurological examination is the examination of consciousness, memory and the state of the psyche. In this way, higher brain functions such as perception and thinking can be assessed and disorders such as dementia, mental illness or consequences of organic diseases such as a stroke can be detected. As described above, the detailed interview already provides significant clues. Speech and language disorders, for example, indicate – depending on their severity – the brain area affected. The comprehension of spoken and written language is assessed with certain tests, as is orientation to space, time and person, and memory (Mini-Mental-Status-Test). Intelligence tests or psychological examinations such as the Rorschach test are also sometimes used.
Other procedures: Imaging procedures
Often, what is hidden well protected behind the skull bones or vertebrae is of particular interest. Computed tomography (CT) is most commonly used to examine the brain and spinal cord. This is particularly good for detecting calcifications, tumors, inflammations and water retention, as well as bleeding and herniated discs. The bones themselves can also be assessed. Conventional X-rays are therefore only rarely used. With magnetic resonance imaging (MRI), soft tissues, tumors and cerebral infarcts in particular can be very well visualized. As with CT, certain questions can be answered by additional injection of a contrast agent. Angiography is used to visualize the vessels, for example if dilatation or constriction is suspected. For this purpose, a thin tube is inserted into the relevant vessels, contrast medium is injected and the image is displayed using X-ray fluoroscopy. The blood flow itself can be made visible in color and audible with the aid of an ultrasound examination. Single photon emission computed tomography (SPECT) and positron emission tomography (PET) not only have complicated names, but also involve complex technology. Therefore, they are quite expensive to use. They make use of radioactive substances that are injected and whose energy emitted in the body is displayed. The exciting thing is that they can be used to visualize the brain at work – active areas show more accumulation than inactive areas. This makes them a popular aid in brain research – which areas react when you are angry, hungry, or watching commercials? What happens when you fall asleep, watch TV, or learn?
Measuring electrical activity
Standard testing for certain neurological disorders, such as epilepsy, includes measuring brain waves (EEG). If one suspects that certain pathways (e.g., for vision or hearing) are damaged, specific stimuli can be applied to the periphery (for example, to the eyes or ears) and the resulting activity on the brain can be measured (evoked potentials). Electroneurography (ENG) can be used to measure the speed of nerve conduction. This is reduced, for example, in the case of injuries or diseases of the nerves. For this purpose, the corresponding nerve is activated with a small current stimulus, which causes the connected muscle to twitch. How long it takes for the stimulus to reach the muscle is measured. Electromyography (EMG) makes muscle activity visible visually and acoustically. This makes it possible to distinguish, in the case of muscle changes, whether the cause is the muscle itself or the nerve supplying it.
Looking into the future
Just recently, researchers from Munich and Vienna developed a novel laser microscope. With this, a previously specially treated brain can be scanned layer by layer and the images thus obtained can be assembled afterwards on the computer into a three-dimensional film. In contrast to computer tomography or magnetic resonance imaging, the thickness of the layers is not half a millimeter, but only a thousandth of that – thin enough to be able to reconstruct individual nerve cells.However, this technique of simulated 3D flights through the brain has one disadvantage: it can so far only be performed on dead tissue. Even if it therefore has no place in clinical diagnostics, it opens up exciting possibilities in brain and nerve research as well as in the training of future physicians.
