Macroscopic anatomy and topography
The cerebellum is compactly located in the cavity of the posterior cranial fossa. Above it stretches a specific structure—the tentorium of the cerebellum (tentorium cerebelli). This formation is a double duplication of the dura mater, stretched in the manner of a specific tent. The tentorium performs a crucial barrier function, reliably isolating the cerebellum from the overlying occipital lobes of the cerebral hemispheres.
Unlike the cerebral hemispheres with their large gyri, the surface relief of the cerebellum has a completely different organization. Its entire surface is densely furrowed by numerous narrow, parallel horizontal folds. These folds are called cerebellar folia. The folia are separated from each other by deep grooves—sulci.
Anatomically, the cerebellum consists of two massive lateral hemispheres. Along the midline, they are connected by an unpaired, narrower structure called the vermis (vermis). It is the vermis that acts as the main connecting link ensuring the integration of the function of both hemispheres.
Relations with the IV ventricle
The inferior surface of the cerebellum is in close contact with the cerebrospinal fluid pathways of the brainstem. Directly between the massive cerebellar peduncles lies the upper half of the fourth ventricle.
This region is of critical importance for the circulation of cerebrospinal fluid. The cavity of the fourth ventricle is not closed—it communicates freely with the subarachnoid space surrounding the brain. This outflow occurs through a system of specific apertures:
- Median aperture: an unpaired opening, historically known as the foramen of Magendie.
- Lateral apertures: paired openings located laterally (foramina of Luschka).
On the inferior surface, another essential structure is distinguished—the flocculonodular lobe (lobus flocculonodularis). It consists of two elements:
- Flocculus (flocculus)—paired structures lying laterally and slightly below (caudal to) the middle and inferior cerebellar peduncles.
- Nodule (nodulus)—the median fragment of the vermis, which structurally unites the right and left flocculi into a single functional system.
Modern functional classification
In modern clinical neurology, the traditional, purely anatomical subdivision of the vermis into small fragments (such as the declive, culmen, etc.) is considered obsolete, as it carries no significant diagnostic value. It has been replaced by a functional-phylogenetic classification that distinguishes three main components.
Archicerebellum (vestibulocerebellum) This is the oldest evolutionary division of the cerebellum. Its second, clinically more precise name is vestibulocerebellum. The anatomical substrate of the archicerebellum is the flocculonodular lobe described above. Functionally, this zone is inextricably linked with the vestibular nuclei located in the brainstem, from which it receives the predominant part of afferent impulses.
Paleocerebellum (old part) The next stage of evolutionary development. This division formed later than the archicerebellum and takes on more complex tasks in processing proprioceptive information, receiving a massive stream of impulses from the spinal cord.
Briefly: answers to topical questions
What divisions are distinguished in the modern functional-phylogenetic classification of the cerebellum?
In the modern functional-phylogenetic classification of the cerebellum, three main divisions are distinguished.
- Archicerebellum (vestibulocerebellum)—the most ancient part, inextricably linked with the vestibular system (includes the flocculonodular lobe).
- Paleocerebellum—the old part, receiving afferentation from the sensorimotor cortex and spinal cord (includes the anterior lobe, simple lobule, and posterior part of the cerebellar body).
- Neocerebellum—the new part, receiving impulses from the cerebral cortex and receptors of the visual and auditory analyzers (includes the middle part of the body and the majority of the hemispheres).
What clinical symptoms are characteristic of a lesion of the archicerebellum (vestibulocerebellum)?
A lesion of the archicerebellum (vestibulocerebellum) is characterized by impairments in balance, gait, and oculomotor functions.
- Astasia—the inability to maintain balance while standing.
- Abasia — inability to maintain balance when walking.
- Truncal ataxia — unsteady gait with a wide base.
- Oculomotor disorders — saccadic pursuit eye movements and gaze-evoked nystagmus.
Which symptoms occur with lesions of the cerebellar hemispheres (neocerebellum)?
With lesions of the cerebellar hemispheres (neocerebellum), symptoms occur ipsilaterally and manifest as decomposition of voluntary movements.
- Dysmetria — inability to stop a movement in time (past-pointing, hypermetria).
- Asynergia — impaired precise cooperation of multiple muscle groups.
- Dysdiadochokinesia — impaired performance of rapid alternating movements.
- Intention tremor — tremor during goal-directed movements, worsening as the target is approached.
- Postural tremor — tremor when maintaining a posture.
When standing and walking, the patient's trunk leans toward the affected hemisphere.
What types of ataxia are distinguished in neurology depending on the lesion localization?
Depending on the localization of the pathological process, several types of ataxia are distinguished in neurology.
- Cerebellar ataxia — occurs with lesions of the cerebellum and its pathways.
- Sensory ataxia (posterior column) — with lesions of the posterior columns and roots of the spinal cord, thalamus, or peripheral nerves.
- Vestibular ataxia — with lesions of the vestibular apparatus, brainstem, and the area of the fourth ventricle.
- Cortical ataxia (frontal) — with lesions of the frontal and occipitotemporal cortical areas.
- Psychogenic ataxia — observed in distress syndrome.
To avoid confusing the eponyms of the fourth ventricle apertures, use the first-letter rule: Majendie's aperture is Median (in the middle, there is only one), Luschka's apertures are Lateral (on the sides, there are two).
Class and exam questions
Are the terms "clivus of vermis" or "apex of vermis" still used?
No, in modern neurology these individual anatomical names are considered outdated and of no clinical significance. They have been replaced by division into functional zones.
What structure physically separates the cerebellum from the cerebral hemispheres?
This role is performed by the tentorium cerebelli (tent) — a dense dual fold of the dura mater.
Which sensory system is most closely connected with the archicerebellum?
The archicerebellum (also known as the vestibulocerebellum) is most closely connected with the vestibular system and the vestibular nuclei of the brainstem.
What else to study on this topic
- Functions and anatomical substrate of the neocerebellum (new cerebellum)
- Afferent and efferent pathways of the paleocerebellum
- Specific symptoms of flocculonodular lobe lesions (vestibular ataxia)
- Clinical manifestations of cerebrospinal fluid circulation disorders at the level of the fourth ventricle apertures
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