What is Neurodegenerative Disease?
Due to the increase in life expectancy, neurodegenerative diseases are increasingly common worldwide. The cause of neuronal death, which causes neurodegenerative diseases and leads to various neurological symptoms, primarily dementia, and impaired movement, is unknown. Symptoms in neurodegenerative diseases depend on which part of the central nervous system is affected. Modern treatment methods are symptomatic and aimed at increasing the activity of surviving neurons to minimize the clinical manifestations of the degenerative process.
Neurodegenerative diseases unite a large group of diseases of the human nervous system, the cause of which is the massive death of certain neurons; moreover, both internal and external factors of infection, intoxication, physical trauma, metabolic disorders, etc. Cases of hereditary predisposition to the emergence of this group have been noticed. Moreover, certain types of neurons often die irrevocably without affecting other parts of the nervous tissue.
Most often, such diseases appear in older people. Among neurodegenerative diseases, the most common are Parkinson’s disease, Alzheimer’s, cerebellar degeneration, spinal amyotrophies, etc.
Mechanisms of development of neurodegenerative diseases
The pathophysiological mechanisms of neurodegenerative diseases include the synthesis and aggregation of proteins with a pathological confirmation; this, in turn, triggers a cascade of immune and metabolic disorders, accumulation of metals in the central nervous system, impaired energy metabolism of cells, enzyme deficiency, etc. At the same time, genetic factors play a significant role in the development of the neurodegenerative process. There are monogenic neurodegenerative diseases (for example, Huntington’s disease, spinal amyotrophies, several variants of spinocerebellar ataxias, Wilson’s disease, monogenic variants of Parkinson’s disease, spastic paraplegia, paroxysmal dyskinesias, etc.). And there are also diseases that develop as a result of disorders in the functioning of whole ensembles with the action of unfavorable environmental factors (idiopathic Parkinson’s disease, atypical parkinsonism, Alzheimer’s disease, amyotrophic lateral sclerosis, frontotemporal dementia, etc.). At the same time, it is essential to remember that the absence of a burdened family history of the neurodegenerative disease does not exclude the presence of a genetic predisposition to its development.
Diagnosis of neurodegenerative diseases consists of a comprehensive assessment of the clinical picture, the nature of the onset and progression of the disease, instrumental laboratory studies, and neuroimaging data. Methods of genetic testing take a special place in the diagnostic process. Given the complex relationship between the genotype and phenotype of the disease, genetic testing is often not limited to analyzing one or two genes. In complex diagnostic cases, to reduce the cost and increase the efficiency of diagnostic search, the method of high-throughput sequencing is widely used, which allows analyzing up to several hundred genes at once.
Environmental health sciences specialists focus on improving public health by eliminating environmental risk factors and identifying the relationships and health risks of the physical environment.
Neurodegenerative diseases of the central nervous system
Neurodegenerative diseases are a conditionally isolated, heterogeneous group of relatively slow developing diseases with a predominant lesion of the gray matter of the central nervous system, and in most cases, characterized by the formation of abnormal cellular and/or extracellular inclusions (deposits) with subsequent death of neurons by the mechanism of apoptosis.
Unfortunately, for most neurodegenerative diseases, there are no radical methods of treatment that would completely stop the pathological process and ensure complete recovery. Therefore, early diagnosis of the disease and a timely start to treatment plays an essential role in influencing the course of the disease and improving the patient’s quality of life.
Among the majority of currently available research methods, only MRI can help the clinician make the correct diagnosis.
Among neurodegenerative diseases, Alzheimer’s disease and Parkinson’s disease are most common in clinical practice.
Considering this fact, for reliable diagnosis and differential diagnosis of these pathological processes in MRI, additional programs have been developed that allow for a targeted assessment of the area of interest.
- Parkinson’s syndrome. Parkinsonism is a slowly progressive neurological syndrome characterized by resting tremor, muscle rigidity, and hypokinesia.
The cause of parkinsonism syndrome can be cerebral atherosclerosis, craniocerebral trauma, epidemic encephalitis, toxic and metabolic disorders, the use of several drugs, and tumors (secondary parkinsonism).
Moreover, true parkinsonism is distinguished as a consequence of Parkinson’s disease.
Pathogenetically, with this disease, degeneration, and death of dopaminergic pigmented (melanin-containing) neurons, gliosis of these nuclear groups, atrophy of the adjacent parts of the midbrain lining, secondary degeneration of dopaminergic and noradrenaline pathways occur. In the substantia nigra, the deposition of iron ions in high concentrations is determined.
That is why in MRI centers, to accurately differentiate between real Parkinson’s disease and Parkinson’s syndrome caused by other causes, special programs are used to specifically study the area of the pathological process and assess the state of the midbrain nuclei.
In most examined patients with Parkinson’s disease, the disappearance of the normal decreased MR signal from the reticular part of the substantia nigra and red nuclei is noted.
In some patients, there is a fusion of normally hypointense zones into one due to iron deposition in the compact and reticular parts.
- Alzheimer’s disease. This neurodegenerative disease is one of the leading causes of dementia in modern society and is a socially significant problem.
Clinically, it is slightly more common in women. It is manifested by a progressive decay of cognitive functions, among which memory impairments occupy the first place. Acute psychotic episodes of delirium, hallucinations, delirium are possible. Less common are hyperkinetic disorders and parkinsonism syndrome.
In Alzheimer’s disease, unlike all other neurodegenerative diseases, the maximum changes are found in the hippocampus.
That is why MRI centers use special high-resolution programs with a targeted examination of the temporal lobes for the most accurate study of the state of the hippocampus.
At the same time, asymmetric atrophy of the hippocampus with thinning of the cortex, widening of Bichat’s gaps on both sides, and the temporal horns of the lateral ventricles is determined on coronal tomograms with a targeted study of the temporal lobes. These changes are the earliest. Also, atrophy of the parietal and occipital lobes with the expansion of the subarachnoid spaces is revealed.
Thus, the emergence of MRI diagnostics using special programs for the targeted study of areas of interest greatly facilitated the diagnosis of neurodegenerative diseases and allowed clinicians to make a correct diagnosis at an earlier stage of the disease, to prescribe the necessary drugs in a timely manner, which means to improve the prognosis of the disease and the patient’s quality of life.