Basic Principles

The cerebellum lies in the Posterior Fossa posterior to the brainstem. It is seperated from the occipital lobe by the tentorium cerebelli.

It contains of two lateral hemispheres and the midline called the vermis.

An important structure on the inferior surface of the cerebellum called the cerebellar tonsils. The cerebellar tonsils herniate through the foramen magnum causing brainstem compression acutely, or in patients with Arnold-Chiari malformations.

There are three further subdivisions of the cerebellum

An anterior lobe: receives afferent fibres from the spinocerebellar tracts. They are important for the functioning of gait

A Posterior Lobe: importance in regulation of motor tone

Flocculonodular lobe- receives input from the vestibular system

The two tracts responsible are the dorsal spinocerebellar tract relay input from Clarkes column (T1-L4) and ventral spinocerebellar tract (L1-L5). Both of these fibre tracts remain ipsilateral hence cerebellar signs are ipsilateral to the lesion not contra-lateral.

The blood supply includes: Superior Cerebellar, Anterior Inferior and Posterior Inferior cerebellar artery.

Clinical Examination

Note midline lesions to the flocculus or vermis will produce symptoms affecting the midline eg truncal ataxia and a broad base gait

Hemispheric Lesions always produce lesions that are ispilateral. The pneumonic DANISH P

Dysmetria and Dysdiadokinesia– past-pointing/rebound affect

Ataxia– broad base gait, or loss of balance towards the side of the lesion

Nystagmus

Intention Tremor

Slurred Speech– scanning dysarthria

Hypotonia and Hyporeflexia (typical pendular reflexes)

Postural Instability

Causes of Cerebellar Dysfunction

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Infectious- cerebellar abscess, viral cerebellitis

Neoplastic- GBM, Metastasis, Medulloblastoma, Haemangioblastoma

Vascular: haemorrhage, infarct

Autoimmune- MS

Trauma- traumatic posterior haemorrhage, or tonsillar herniation

Endocrine: hypothyroidism

Drugs: Alcohol, Anti-epileptics

Metabolic: vitamin B1 deficiency, hypoxia, hypoglyaemia

Degenerative/congenital: Arnold-chiari malformation