Dementia refers to the most severe form of cognitive deficit. It is a neuropsychological defect based on chronic brain damage, or encephalopathy. According to the 10th Revision of International Classification of Diseases, dementia is a decrease of memory and other cognitive domains as compared to the baseline level, usually in combination with other mental disorders (emotional, behavioral), which is determined in patient with clear consciousness and is caused by organic brain damage. Most patients with dementia have a multiple deficits of higher cortical functions, which leads to a restriction of professional or social functioning and has a progressive course. The clinical presentation of dementia includes, along with cognitive deficits, neuropsychiatric and behavioral disorders that lead to more significant functional disorders. Patients have difficulty when performing social and professional activities, and their ability to self-serve is limited. Thus, most patients with dementia need physical assistance in daily living activities.
Typical symptoms of the initial stage of dementia may be lack of concentration, slowly progressing memory disorders, rapid fatigability, reduced interests and initiative, difficulties in performing complex household tasks and orientation in space, weakening and/or deterioration of thought processes, low mood background, general anxiety. Assimilation of new information is difficult, the existing skills are gradually lost. Patients may have speech disorders in the form of simplifying phrases, difficulties in understanding complicated turns of speech.
As disease progresses, the severity of mnestic disorders increases. As result, patients forget the names of household items, the names of close people, etc. Distinct manifestations of disorders of higher mental functions, motor, sensory aphasia, gross violations of praxis and gnosis occur. Patients loss not only ability to work but also to perform self-care. Patients cannot navigate even in the familiar environment (they are not able to walk to a nearby store on their own, they cannot find even a well-known route), in severe cases — within their own apartment. The ability to use household appliances, perform hygiene procedures, and dress is impaired.
At the advanced stage, mood instability, increased irritability, and agitation may develop. In half of the patients, depressive changes are noted.
At the stage of advanced dementia, there may be significant memory disorders (including agnosia), disorientation in time and space, decreased motivation for daily activity, neglect with personal hygiene, violation of social behavior, lack of criticism of one’s condition.
Depending on the features of the clinical picture, dementia can be divided into the following types:
With a predominant involvement of the cerebral cortex, cognitive disorders prevail, such as memory loss, speech disorders (aphasia) with a steady pace of mental activity. Subcortical dementia is associated with a significant slowdown in thought processes, apathy, forgetfulness, extrapyramidal disorders (muscle rigidity, bradykinesia, abnormal posture), elements of pseudobulbar paralysis (dysphonia or hypophonia, dysarthria, reflexes of oral automatism).
Currently, there is also a syndrome of mild cognitive impairment (MCI). Patients with MCI complaints of increased fatigue when performing mental work, decrease in memory, attention or learning ability that does not lead to problems with daily activity. In MCI, cognitive disorders cause anxiety to the patient and attract the attention of others. Objective evidence of mnestic disorders may occur. However, the general intellectual level remains intact. In most cases, MCI is thought to be a pre-dementia stage of cognitive deficit. The delineation of this form can contribute to the timely diagnosis of dementia and the early start of treatment.
Morphological substrate of dementia is a variety of types of organic brain damage. More than 100 causes of dementia are reported.
Dementia associated with the following processes are distinguished:
- degenerative neurological diseases, for example, a primary neurodegenerative process (Alzheimer’s disease) or cerebrovascular pathology;
- those developed against the background of various neurological and somatic conditions, such as cardiovascular and demyelinating diseases, chronic intoxication, dysmetabolic disorders, intracranial mass lesions (tumors, subdural hematoma), hydrocephalus, traumatic brain injury, epilepsy, neuroinfection.