DISEASES OF THE CEREBELLUM: SYMPTOMS AND CAUSES - NEUROPSYCHOLOGY - 2024

The diseases of the cerebellum can produce a wide variety of deficits, affecting both the development of behaviors belonging to the motor sphere as other areas of intellectual functioning.

Since 1800, different clinical reports describe individuals with damage to the cerebellar territory, including the lack of development of this structure or atrophy. In these studies, intellectual and emotional deficits and even neupsychiatric disorders are described. Additionally, later clinical studies identified a relationship between the cerebellum and aggressive personality or behaviors.

Cerebellum (pink color)

On the other hand, in the central decades and the end of the 20th century, clinical research focused on the description of cognitive problems that were systematically presented in patients with cerebellar atrophy. These alterations included verbal intelligence, visuospatial skills, learning, memory, and frontal system functions.

A large number of pathologies that affect the cerebellum can compromise the proper and efficient functioning of this structure. Strokes, cerebellar infarcts, tumors or malformations are some of the pathologies that can involve focal cerebellar damage.

In general, many of these are expected to produce motor syndromes related to motor coordination and balance, although various current investigations have increased the evidence for the presence of emotional, behavioral or effective alterations.

At a cognitive level, cerebellar lesions can be associated with a fairly extensive group of symptoms, among which, due to their impact on the individual's functionality, symptoms and deficits in memory, learning, language, executive functions, inhibition stand out. and cognitive flexibility and even planning.

Diseases at the brain level

Ictus

Cerebellar vascular-cerebrovascular accident does not always involve motor damage or impairment, which provides preliminary evidence for motor topographic organization, versus non-motor functions in the human cerebellum.

In the study by Schmahmann et al. (2009) examined patients with cerebellar stroke, the starting hypothesis being the following:

• If the traditional view that the role of the cerebellum is limited to motor control is correct, then any acute stroke site in the cerebellum must, by definition, impair motor function.
• In contrast, if the topography hypothesis is correct, then there should be no non-motor regions of the cerebellum in which a considerable infarct would have no impact on motor control.

In this study, 33.3% of the patients examined who were examined between 6 and 8 days after the onset of the stroke were motorically normal, demonstrating that there is no sign of cerebellar motor syndromes characterized by gait ataxia, appendicular dysmetria or dysarthria.

In patients with motor signs, the lesions involved the anterior lobe (IV). In patients with fewer signs or no signs, the lesions spared the anterior lobe and were confined to the posterior lobe (VII-X). Patients with damage to VII-X + VI but without damage to the previous one had a lower degree of motor impairment.

This and other studies have shown that the cerebellar motor representation is located mainly in areas of the anterior lobe, especially in lobes III-V and to a lesser extent in the posterior area, specifically in lobe VI.

On the other hand, Baillieux et al. (2010), in a functional neuroimaging study showed that 83% of the patients examined showed significant cognitive or affective behavior impairment.

The analysis of the neuropsychological data revealed a clear tendency towards the lateralization of cognitive function within the cerebellum: D

• Left cerebellar damage is related to right hemispheric dysfunction, attention deficit and visuospatial alterations
• Right cerebellar damage is related to left hemispheric dysfunctions, such as disrupted language skills.

Tumors

Posterior fossa tumors represent 60% of intracranial tumors that appear during childhood and 20% of intracranial tumors in adults. Two types of tumors can appear fundamentally in the posterior fossa: those located anteriorly or those located posteriorly, affecting the cerebellum.

Within this area we can differentiate four types of tumors: medulloblastomas, cerebellar astrocytomas (which can affect the vermis or the cerebellar hemispheres), brain stem tumors and ependinomas.

Due to the enormous increase in survival of this type of patients due to the improvement of surgical and pharmacological treatments, different studies have investigated the possible cognitive sequelae of tumors, however, the possible relationship between cognitive deterioration and cerebellar injury, it has often been ignored.

Patients with this type of neoplasm may have cerebellar damage due to tumor growth, tumor resection, or due to chemotherapy and / or radiation therapy.

As in the case of cerebellar vascular-cerebral accidents, some studies have shown that lesions in the right areas of the cerebellum can imply linguistic or visuospatial deficits, while lesions in the contralateral hemisphere will imply the opposite effect. On the other hand, damage in the midline, in the vermis, would affect affective regulation.

Malformations

In general, cognitive and behavioral problems derived from cerebellar malformations have been studied in children with cerebellar agenesis (partial or complete absence of the cerebellum), as well as in cerebellar ataxia.

Traditionally, it has been thought that cerebellar malformation or absence did not imply any functional signs or symptoms, or that it was even asymptomatic, however, this view turns out to be wrong.

Gadner et al. Described different motor deficits and intellectual disability in several patients with almost complete agenesis.

On the other hand, Schmahmann (2004) described the appearance of motor and behavioral deficits in children with partial or complete absence of the cerebellum, associating the severity of the symptoms to the degree of severity of the agenesis.

These patients presented ataxic-type motor deficits, motor retardation or clumsiness, while the behavioral traits included autistic signs.

Other cognitive deficits affecting executive function (disinhibition or abstract reasoning), spatial cognition or language were also described.

Cerebellum and neuropsychiatric disorders

As we have reviewed previously, studies from the last two decades have shown that the cerebellum plays a key role in different cognitive domains.

Recently, different studies have shown a strong association between structural and functional abnormalities of the cerebellum and different psychiatric disorders, especially schizophrenia (Chen et al., 2013; Fatemi et al., 2013), bipolar disorder (Baldacara et al., 2011; Liang et al., 2013), depression, anxiety disorders (Nakao et al., 2011; Schutter et al., 2012; Talati et al., 2013), attention deficit hyperactivity disorder (ADHD) (An et al. al., 2013; Tomasi et al., 2012; Wang et al., 2013), and autism (Marko et al., 2015; Weigiel et al., 2014).

Attention deficit hyperactivity disorder

Approximately 5% of children and adolescents between 6 and 17 years of age are diagnosed with ADHD, while in a good part of individuals (between 30-50%) the disorder continues to persist into adulthood.

This type of disorder is characterized by three types or groups of symptoms: attention deficit, impulsivity and / or hyperactivity. In addition, in many cases, individuals with this type of disorder tend to have deficiencies in motor coordination, balance, or the execution of movements.

Little is currently known about how the brain of ADHD patients develops during the course of this disorder. A growing number of studies have begun to show evidence of abnormalities affecting areas such as the cerebellum and the corpus callosum. These studies show morphometric alterations related to cerebellar volume.

Castellanos et al. (2002), found volumetric abnormalities with a reduction in the size of the cerebellum. However, Ivanov et al. (2014) found that compared to healthy participants, young people with ADHD exhibit smaller regional volumes corresponding to the lateral surface of the left anterior part and the posterior area of ​​the right cerebellum.

On the other hand, stimulant drug intake was associated with larger regional volumes in the left cerebellar surface, while the severity of ADHD symptoms was associated with smaller regional volumes in the vermis.

In general, shrinkage of the cerebellum is a recurring theme in studies investigating the relationship between ADHD and the cerebellum. However, to date, these studies have uniquely explored and tested participants once they have been diagnosed with ADHD.

This means that we cannot determine whether the abnormalities in the cerebellum were present from birth or develop during the growth of the child, and how this affects the etiology of ADHD. (Philips et al., 2015).

Autism

Autism spectrum disorder or (ASD) is a developmental disorder characterized by a deterioration in social interactions, by partial or almost total verbal communication, and restricted behavior patterns and interests.

In addition, ASD includes a variety of motor symptoms, among which we can highlight stereotyped and repeated movements.

Different investigations have shown that several brain areas can be related to this disorder: prefrontal areas, cerebellum, limbic system and amygdala.

The cerebellum can influence the motor cortex and the prefrontal cortex, responsible for motor control and social cognition, so it would be possible that cerebellar abnormalities caused many of the symptoms seen in ASD.

Currently, three types of cerebellar abnormalities have been identified in individuals with ASD: reduced Purkinje cell function, reduced cerebellar volume, and disruption of connections between the cerebellum and different brain areas.

Although future research is still necessary to establish the key pathological features in the different anomalies described, the reduction in the volume of the upper vermis area may constitute the main anatomical substrate for the signs and symptoms that underlie ADHD.

Schizophrenia

Schizophrenia has a wide variety of symptoms belonging to different psychological domains, which also include cognitive deficits.

In many patients, deficits in learning, memory, and executive function are present. Furthermore, many of these symptoms are similar to those seen in patients with focal damage to the cerebellar cortex.

Neuroimaging studies carried out with schizophrenic patients propose that the variety of cognitive symptoms that are expressed in these are related to a dysfunction of the pathways between the cerebellum and the cerebral cortex.

Many suggest that alterations in the cortico-thalamic-cerebellar-cortical circuits play a role in cognitive functioning in schizophrenia. (Philips et al., 2015). In addition, a reduction in the volume of the vermis and the blood flow in the cerebellar cortex and the vermis has been described.

Different investigations tend to agree that, in patients with schizophrenia, a cerebellar dysfunction may appear, which could be causing many of the cognitive and neuropsychiatric symptoms present in this type of patient.

Bipolar disorder

The bipolar disorder is characterized by being chronic and by presenting variations in affect, emotion and energy level.

Neuroimaging studies show that the cerebellar region most associated with this type of disorder is the vermis. In the review of studies comparing the volume of the cerebellum in bipolar patients with healthy subjects, reductions in cerebellar regions are described.

Specifically, the volumetric reduction of the V3 region of the vermis is significantly present in patients. Furthermore, the severity of the symptoms is associated with broader lesions of the vermis. (Philips et al., 2015).

Depressive disorder

Depression is characterized as a mood and mood disorder and is delimited by different physical, cognitive, behavioral and psychophysiological disorders.

Patients with major depressive disorder (MDD) have also shown various abnormalities in the cerebellum. Yucel et al. Found a significant reduction in vermis.

Studies have also shown an overall cerebellar reduction, and reduced blood flow to areas of the vermis. In addition, with severe depression and also resistant to treatment, abnormal connections between the frontal lobe and the cerebellum have been described (Philips et al., 2015).

Anxiety disorder

It has also been shown that anxiety disorders could be related to an increase in excitability present in PTSD, GAD and SAD.). In sum, the majority of studies on anxiety and the cerebellum suggest overactive cerebellum (Philips et al., 2015).

Bibliography

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