Cerebellum | Hindbrain

Cerebellum

CerebellumThe cerebellum lies in the posterior fossa below the occipital lobe and attaches itself to the brain stem from behind. It is divided into two hemispheres and a central part, the cerebellum (Vermis cerebelli). It can also be divided into cerebellar marrow (inside) and cerebellar cortex (outside).The cerebellar cortex contains three layers of cells: The molecular layer, the Purkinje cell layer and the granule cell layer (from outside to inside).

The cerebellum is connected to the brain stem by three so-called cerebellar peduncles, the upper, middle and lower (pedunculus cerebelli superior, medius and inferior). Between the front part of the cerebellum and the rear part of pons and medulla oblongata lies the fourth ventricle filled with cerebrospinal fluid (liquor). Four nerve cell nuclei are located on each side of the cerebellar medulla.

The nucleus fastigii, nucleus globosus, nucleus dentatus and nucleus emboliformis. In these nuclei, information about nerve cells is received, switched and transmitted. Thus, the cerebellum plays a central role in the fine tuning of movements.

It turns the “gross motor skills” initiated by the motocortex in the cerebral cortex into fine motor skills, so to speak. The cerebellum receives a great deal of information on this. Among other things, nerve fibers from the spinal cord, the cerebral cortex, the brain stem and the organs of equilibrium run into the cerebellum.

These nerve fibers run in the three cerebellar peduncles mentioned above. After processing and coordinating the information, the cerebellum sends its “revised version” to the thalamus, the reticular format, the nucleus ruber in the midbrain and nerve cell nuclei responsible for balance (vestibular nuclei). In addition to controlling and fine-tuning motor functions, the cerebellum also appears to play an important role in the storage of movement patterns learned once and automated over time.

It is also being discussed whether the cerebellum also plays a role in cognitive processes such as behavior and affect. In terms of function, the cerebellum can be further divided into three different sections. The vestibulocerebellum is mainly responsible for balance, uprightness and coordination of eye movements.

The spinocerebellum is responsible for standing and walking. The Pontocerebellum is the fine regulator for the entire motor function. Whether it is the grip of a coffee cup, the tweezer grip or playing the piano.

Lesions in the cerebellum sometimes result in relatively characteristic findings. The most typical symptom is cerebellar ataxia. This can be seen when sitting, standing or walking.

Without support, it is no longer possible to sit or stand securely upright, the gait pattern is broad-legged (broad-based) and choppy, it appears gross motor and clumsy. Other neurological symptoms are relatively characteristic for a lesion of the cerebellum, they can be detected by simple clinical examinations: Intention tremor is a tremor (trembling) that becomes more pronounced as the pointing finger approaches the target. It can be tested by bringing the patient’s index finger to his own nose.

If the finger swings out more and more rhythmically the closer it gets to the nose, this is an indication of an intention tremor. Another test for the diagnosis of a cerebellar problem is a rapid alternation of opposing movements, such as turning the hand so that first the palm of the hand and then the back of the hand is on top. If this is not possible or is clearly faltering and difficult, it is called dysdiadochokinesis, i.e. the inability to make rapid alternate (antagonistic) movements.

Another indication of cerebellar damage is the so-called rebound phenomenon. Here, the physician grasps the patient’s forearm bent in the elbow joint and pulls it towards him while asking the patient to hold against it. If the doctor now suddenly lets go, the patient cannot react quickly enough in a coordinated manner and would hit his forearm in the face.

This is prevented by the doctor by a safety handle. Damage to the cerebellum thus shows quite typical symptoms, which can initially be detected without much effort in clinical-neurological everyday life.