Cerebellar abnormalities

Cerebellar disorders have many causes, including congenital malformations, hereditary ataxias, and acquired diseases. Diagnosis is clinical and sometimes neuroimaging and/or genetic testing.

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Causes cerebellar disorders

The cerebellum is divided into 3 parts: the old part (vestibulocerebellum) includes the flocculonodular lobe, located in the medial zone, closely associated with the vestibular nuclei, helping to maintain balance and coordinate the movements of the eyes, head and neck; the ancient part (paleocerebellum) - the cerebellar vermis located in the midline, helps to coordinate the movements of the legs and trunk, its damage leads to disturbances in posture and gait; the new part (neocerebellum) - the cerebellar hemispheres control rapid and precisely coordinated movements of the limbs, mainly the arms.

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Congenital malformations

The malformations are almost always sporadic, often occurring as part of complex anomalies (eg, Dandy-Walker syndrome) that also involve other parts of the CNS. The malformations become apparent early in life and are non-progressive. Symptoms vary greatly depending on the structures involved; however, ataxia is usually present.

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Hereditary ataxias

Hereditary ataxias may be transmitted in an autosomal recessive or autosomal dominant manner. Among the autosomal recessive ones are Friedreich's ataxia (the most common), ataxia-telangiectasia, abetalipoprotenemia, hereditary ataxia due to vitamin E deficiency, and cerebrotendinous xanthomatosis.

Friedreich's ataxia is associated with a mutation in the gene responsible for the synthesis of the mitochondrial protein frataxin. Pathological expansion of GAA (glycine-alanine-alanine) DNA repeats leads to a decrease in frataxin levels, impaired mitochondrial function, and accumulation of iron in their matrix. Gait instability appears by the age of 5-15, accompanied by ataxia of the upper limbs, dysarthria, and paresis (especially of the arms). Cognitive functions often decline. Tremor is minimal or absent. Reflexes, vibration, and proprioceptive sensitivity are lost. Foot deformities, scoliosis, and progressive cardiomyopathy are typical.

Spinocerebellar ataxias (SCAs) are inherited predominantly in an autosomal dominant pattern. Fifteen different loci of gene mutations have been identified, and accordingly, 15 types of SCA are distinguished (SCA 1-8, 10-14, 16 and 17), 9 of which are characterized by expansion of DNA repeats. In 6 types, DNA repeats of CAG encoding the amino acid glutamine (as in Huntington's disease) have been identified. Symptoms vary. In SCA 1-3, multiple areas of the peripheral and central nervous system are most often affected, neuropathy, pyramidal symptoms, restless legs syndrome, and ataxia are characteristic. SCA 5, 6, 8, 11 and 15 usually manifest only with cerebellar ataxia.

Acquired ataxias

Acquired ataxias may occur in non-hereditary neurodegenerative diseases (eg, multiple system atrophy), systemic diseases, toxic exposures, and idiopathic diseases. Systemic disorders include alcoholism (alcoholic cerebellar degeneration), sprue, hypothyroidism, and vitamin E deficiency. Toxic substances include carbon monoxide, heavy metals, lithium, phenytoin, and some organic solvents.

In children, the cause may be primary brain tumors (medulloblastoma, astrocytoma), for which the median cerebellum is the most common localization. Rarely, reversible diffuse cerebellar dysfunction develops in children after a viral infection.

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Symptoms cerebellar disorders

Symptoms depend on the cause, but typically include ataxia (an abnormal, wide-legged gait due to poor coordination).

Ataxia is a typical sign of cerebellar dysfunction, and other movement disorders are also possible.

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Diagnostics cerebellar disorders

The diagnosis is made based on clinical data, taking into account the family history after excluding acquired systemic diseases and performing MRI. If the family history is positive, genetic testing is performed.

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Treatment cerebellar disorders

Treatment of cerebellar disorders is symptomatic unless the cause is acquired and reversible.

Some systemic diseases (for example, hypothyroidism, sprue) and intoxications are curable, sometimes surgery is effective (tumor, hydrocephalus), in other cases cerebellar disorders are treated symptomatically.