Studies of the brain and nerves: functional tests

Various functional tests are available for examining the brain and nerves, such as tests of motor skills or sensitivity. In the following we explain which tests are available and what is done with them.

Functional tests: cranial nerves

The twelve pairs of cranial nerves are important structures that connect the brain to the periphery. They contain various nerve fibers that are responsible for muscle movement, sensory perception, and other sensations that go to the face (including eyes, ears, nose, mouth), throat, and chest and abdominal organs.

Their function can be assessed, among other things, by the following tests and examinations:

  • eye tests
  • ear exams
  • Examination of skin sensitivity on the face, facial expressions and tongue movement

These are checked when the doctor asks you, for example,  to stick out your tongue  , frown and watch his fingers.

Motor function test

The ability to move voluntary muscles in a targeted and coordinated manner requires coordination of the brain, spinal cord, peripheral nerves, and muscles. That is why a wide variety of tests are used to test motor skills.

  • Coordination: Coordinated  interaction is checked during normal walking or tightrope walks, standing with closed eyes, on tiptoe and on heels or while virtually screwing in a light bulb. This can be impaired in very different disorders such as Parkinson’s disease or inner ear damage.
  • The doctor asks the patient to tense individual muscles or muscle groups against their resistance. He always judges the  strength in a side comparison  and also pays attention to pain. Holding your arms out in front of you with your eyes closed can also indicate slight disorders – namely when one arm slowly sinks down.
  • The  state of tension of the muscles  also provides important information about possible diseases. It can be increased (spasticity, rigidity), for example in Parkinson’s disease, or decreased, for example in muscle disorders.
  • Reflexes:  Almost everyone knows it: the rubber-coated, shiny little hammer with which the doctor hits under the knee or in the crook of the elbow, causing the leg or arm to twitch. He uses it to test how well a stimulus is transmitted to the muscle via nerve fibers. Reflexes can be diminished or extinguished or increased (clonus). Since the stimulus response is individually different, reflexes are always assessed in a side comparison. Strong differences are with high probability pathological. There are also reflexes that are normal in  babies  but later become pathological.

Test of Sensitivity

The examination of the different sensory qualities is also carried out in a side comparison. One after the other, the patient is given various stimuli with his eyes closed – first in healthy areas to compare how it feels normal, then in the presumably diseased areas.

Being checked:

  • Sensation of touch (e.g. with a cotton ball)
  • Vibration sensation (with a tuning fork placed on bony prominences)
  • Sensation of position and movement (“what is up and down” with the finger being moved by the doctor)
  • Sensation of pain (with a broken wooden stick) and
  • Temperature sensitivity (with cold and warm water in a test tube)

In addition, the patient should recognize numbers that are written on the skin, feel or grasp objects, and recognize when two stimuli are applied at the same time. Sensitivity disorders occur, for example, in the case  of a herniated disc  or nerve disorders as a result of  diabetes  .

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