Evaluation of the Role of Neurodegeneration in Schizophrenia

Schizophrenia is a progressive and complex psychiatric disorder with a lifetime prevalence of 1%, usually diagnosed between the ages of 20-25, its etiology is not fully understood, and it progresses with relapses. In addition to positive symptoms such as delusions, hallucinations, disorganized speech and behavior, and negative symptoms such as affective blunting, anhedonia, and avulsion, impairment in social and occupational functionality and cognitive impairment can be observed.

The incidence of schizophrenia in relatives of individuals with schizophrenia is higher than in the general population. Although heredity is a strong component in the etiology of schizophrenia, environmental exposures and stressors such as maternal immune infection, obstetric complications, childhood trauma and cannabis exposure also play a role in the development and neuropathology of the disease. Hereditary risk and the interactions of these exposures with the genomic sequence form the basis of the neurodevelopmental hypothesis of schizophrenia.

The neurodevelopmental hypothesis proposes that disruption of brain development early in life is responsible for the onset of symptoms. According to the neurodevelopmental hypothesis, although the biological changes and other features of the disease are present in the patient long before the onset of the characteristic symptoms of schizophrenia, these symptoms will not appear in the patient until a certain level of development is reached by interacting with some factors.

Detection of some brain findings such as decreased cortical volume, ventricular enlargement, and altered gyrification patterns in the imaging findings in the initial period of schizophrenia supports the view that some changes in the brain can be seen even before the onset of schizophrenia, but in this view, no worsening of the damage in the brain is expected. Therefore, the neurodevelopmental model falls short of addressing the progressive brain damage observed in patients with chronic schizophrenia Studies show a worsening clinical course in 60% of patients with schizophrenia. The neurodegenerative hypothesis focuses on the fact that biochemical changes in schizophrenia are characterized by chronic and progressive impairment of the nervous system, leading to different clinical syndromes, loss of neurological function and behavioral disorders. It is thought that the presence of changes in the brain morphology of patients with schizophrenia in various studies indicates degeneration. In brain imaging, changes such as decrease in temporal lobe and frontal lobe volume, enlargement in the lateral ventricles and third ventricle, hippocampal atrophy have been detected. Changes in these areas of the brain indicate loss of white and gray matter. Detection of these differences in the first psychotic attacks and early-onset patients; suggests that the degenerative process starts from the earliest stages of the disorder. In addition, it has been shown that the difference between brain imaging of healthy controls and patients with schizophrenia increases with age.

Following the clinical onset of schizophrenia, patients differ significantly in disease course. Relapse is associated with significant psychological and social distress as well as increased economic burden in patients with schizophrenia and their families. Good response to antipsychotic drug and low optimal antipsychotic dose in patients with first episode schizophrenia; This suggests that relapse reduces drug response, and that the increase in the number of attacks is associated with resistance to treatment in schizophrenia. The state of not responding adequately to treatment is defined as resistance to treatment, and the most comprehensive definition of the concept of Treatment-Resistant Schizophrenia (TFS) was made by Kane, and it was named "Kane Criteria". Kane Criteria Criteria for resistance to treatment applied in the past; Failure to respond to at least three antipsychotic treatments at 1000mg/day chlorpromazine or equivalent dose for six weeks in the previous five years. Lack of a good functioning period in the last five years. Criterion of severity of psychopathology; A Brief Psychiatric Rating Scale (BPRS) score of 45 and above, At least two of the 4 positive symptoms of BPRS (thought disorientation, skepticism, hallucinatory behavior, unusual thoughts) are 4 and above, Clinical General Impression (CGI) score is 4 and above Prospective treatment non-response criteria; Unresponsive to haloperidol therapy up to 60 mg/day. (Response to treatment was defined as a BPRS score of more than 20% and a CGI score of 3 or less, or a BPRS score of 35 or less). Diagnosis of Treatment-Resistant Schizophrenia in Clinical Practice - A history of two antipsychotic treatments - At least 6 weeks on an antipsychotic and at least 600 mg Chlorpromazine equivalent dose - Brief Psychiatric Rating Scale (CPRS) ≥45 - Positive and Negative Syndrome Global Scale (PANNS) ≥75 - Clinical Impression Scale-Severity of Disease (CGI-HȘ) ≥ 4 - General Evaluation of Functioning (IGD) ≤50 In psychiatry, the diagnosis is made based on the evaluation of signs and symptoms in the clinical interview, and there is no biological "gold standard" diagnosis. It has been shown that in patients with first episode schizophrenia, each episode lasts longer than the previous episode, and relapse is associated with progressive loss of cortical tissue and brain volume. Relapse is an expression of worsening psychopathology and it is thought that some neurobiological pathways may cause relapse. The glial fibrillary acidic protein GFAP, which is one of the reactive astrocyte-specific biomarkers indicating astrogliosis, is not released from the healthy astrocyte. The increase in GFAP indicates damage and inflammation in the astrocyte. It is also secreted in different amounts from different parts of the brain. GFAP can be measured in serum in proportion to the degree of damage by passing into the blood circulation as a result of astrocyte damage. One of the cytoskeletal components (GFAP), it has been associated with neurodegenerative diseases such as Alzheimer's and amyotrophic lateral sclerosis, and is thought to play a role in the etiology of schizophrenia and is one of the potential markers of neurodegeneration and progression in schizophrenia. In a study measuring the amount of serum GFAP in patients with schizophrenia and healthy volunteers, GFAP was found to be high in the schizophrenia group, but it was noted that it was higher especially in patients using clozapine.

The S100B protein is a member of the calcium-binding protein group and is secreted from many cells, such as astrocytes, oligodendrocytes, certain neuronal populations, adipocytes, or lymphocyte populations. This protein is released from stimulated or damaged astrocytes into the cerebrospinal fluid (CSF) and crosses the blood-brain barrier and enters the peripheral circulation. The S100B protein (depending on its level) can have a trophic or toxic effect on surrounding neurons, astrocytes, or microglia. At low concentration, S100B ensures neuron survival, but at higher level it leads to neuronal cell apoptosis and is associated with brain damage or neurodegeneration. Various brain tumors, neuroinflammatory and neurodegenerative disorders, psychiatric diseases and even major cardiac events have been investigated. Serum and cerebrospinal concentrations of S100B are found to be high in schizophrenia, which is thought to indicate activation of astrocytes or loss of oligodenrocytes. Studies in cell culture and experiments with ligands have shown that S100B can increase dopaminergic neurotransmission. With the pathogenesis of the disease, varying concentrations of S100B in patients with schizophrenia; It is thought that the binding of S100B to the D2 receptor leads to a decrease in glutamate concentration at synapses as a result of increased signal transduction and increased glutamate uptake in astrocytes, and may also be related to the role of S100B in neuronal apoptosis in many different ways.

Data Collection and Evaluation Scales

1. Sociodemographic and Clinical Data Form:
2. The Brief Psychiatric Rating Scale (BPRS)
3. Positive and Negative Syndrome Scale (PANSS)
4. Clinical Global Impression (CGI)
5. General Evaluation of Functioning (IGD)
6. STANDARDIZED MINI MENTAL TEST (SMMT) or MODIFIED MINI MENTAL TEST (MMSE-E) FOR THE UNEDUCTED