Diagnosis of neurodegenerative diseases: how modern medicine detects brain disorders

Neurodegenerative diseases are one of the most complex problems in modern neurology. They develop slowly, affecting nerve cells and gradually impairing cognitive, motor and behavioral functions. According to WHO, the number of patients with dementia is increasing every year, and early diagnosis remains the main tool that allows you to extend the quality of life and delay complications.

Unlike many acute conditions, neurodegenerative processes rarely manifest themselves immediately. Therefore, modern diagnostics are based on a combination of biomarkers, instrumental methods, and assessment of functional changes in the brain.

What processes underlie neurodegeneration?

Before choosing diagnostic methods, doctors consider what mechanisms may be involved in the development of the disease. These include:

• accumulation of pathological proteins (amyloid, tau, alpha-synuclein)
• mitochondrial damage
• chronic inflammation of nerve cells
• impaired blood supply to the brain
• genetic mutations
• disruptions in intercellular communication

It is important to understand that each neurodegenerative disease has its own “molecular signature.” That is why the approach to diagnosis cannot be universal.

How diagnostics begin: first level of assessment

In the early stages, symptoms are often subtle. Initial signs that require examination include:

• slowed thinking and drowsiness
• decreased flexibility of thinking
• difficulty with orientation or word finding
• gait changes, muscle rigidity
• micromotor disorders
• decreased sense of smell (typical of Parkinson's disease, according to the Mayo Clinic)
• frequent mood swings or changes in behavior

The patient may not notice this, but the doctor should assess how these changes affect daily functions.

Biochemical markers: the key to early detection

In the last 10 years, laboratory indicators that reflect the state of nervous tissue have been actively integrated into diagnostics.

Markers in the blood

The FDA notes their promise in the early detection of Alzheimer's disease and other forms of dementia. They are being studied:

• NfL (neurofilaments light chain) — an indicator of neuronal destruction
• Amyloid proteins
• Phosphorylated tau protein

The advantage of these tests is that they allow you to assess the progression of the condition without invasive procedures.

Markers in cerebrospinal fluid

CSF gives a more accurate picture of early pathological changes:

• reduction of amyloid β42
• increase in total and phosphorylated tau
• changes in the tau/amyloid ratio

According to the Alzheimer's Association, these markers are the "gold standard" for confirming Alzheimer's disease.

Instrumental methods: how brain structure and function are assessed

Diagnosis is not limited to tests alone. Neuroimaging plays a significant role.

Brain MRI

Allows you to evaluate:
• cortical atrophy
• hippocampal changes
• white matter damage
• consequences of microstrokes

For Parkinson's disease, MRI helps rule out other causes of movement disorders.

PET scan

PET with fluorine-labeled or amyloid markers helps detect the accumulation of pathological proteins.
According to the NIA, PET can confirm the presence of amyloid plaques even before symptoms appear.

SPECT

Assesses blood flow in the brain, which makes it possible to differentiate types of dementia, including dementia with Lewy bodies.

EEG

Shows the electrical activity of the brain. Used as an additional method when epileptic manifestations or changes in electrical activity are suspected in dementia.

Cognitive protocols and neuropsychological tests

Diagnosis of neurodegenerative diseases necessarily includes an assessment of cognitive functions. In practice, the following are used:

• MMSE
• MoCA
• FAB (fronto-orbitofrontal test)
• clock test
• assessment of executive functions

These tests allow you to assess not only memory, but also speech, attention, logic, information processing speed, and behavioral reactions.

Genetic tests: when are they needed?

In most patients, neurodegenerative diseases are not a direct result of mutations. However, genetic testing is recommended if:

• there were early cases of dementia or Parkinson's in the family
• symptoms appeared before the age of 50
• Huntington's disease is suspected
• combined neurological and psychiatric symptoms are observed

Genetic analysis helps determine the prognosis and choose an individualized surveillance program.

Comparison of methods: what is used and when

A comprehensive approach allows you to get the most accurate picture.

Why early diagnosis is critical

Neurodegenerative diseases cannot be completely cured, but their progression can be slowed. According to Mayo Clinic research, early detection of disorders allows for:

• choose personalized treatment
• prevent rapid deterioration of cognitive functions
• reduce the risk of complications
• adapt lifestyle and minimize symptoms
• facilitate care and improve quality of life

For some diseases (such as Parkinson's), early treatment provides a significantly better prognosis.

FAQ: answers to frequently asked questions about diagnosing neurodegenerative diseases

Is it possible to detect neurodegenerative disease at a very early stage?
Yes, but only with a comprehensive examination. Biomarker tests (NfL, amyloid, tau) along with MRI or PET can show changes even before the onset of severe symptoms. This is confirmed by studies by the National Institute on Aging.

Is an MRI alone sufficient to make a diagnosis?
No. MRI is important for assessing brain structure, but it does not detect molecular changes characteristic of Alzheimer's or Parkinson's disease. A complete diagnosis includes laboratory tests, cognitive evaluation, and sometimes PET scans.

When can a doctor order a cerebrospinal fluid test?
This is done in cases where it is necessary to confirm Alzheimer's disease, clarify the type of dementia, or rule out other conditions. CSF allows for accurate measurement of beta-amyloid and tau protein levels.

Is genetic testing mandatory?
No. Genetic testing is only indicated for patients with suspected hereditary forms of the disease, as well as those who have symptoms before the age of 50 or have a strong family history. Most cases of neurodegeneration are not associated with mutations.

Can stress, trauma, or chronic illness "trigger" the neurodegenerative process?
They are not a direct cause, but they can accelerate the manifestation of latent disorders or worsen the course of existing disorders. According to the Mayo Clinic, chronic stress affects the brain structures responsible for memory.

Are cognitive impairments always a sign of dementia?
No. They can be caused by depression, vitamin B12 deficiency, thyroid disorders, infections, or medication side effects. That's why it's important to get a lab test done before making a diagnosis.

Is it necessary to repeat the diagnosis if the condition is stable?
Yes. Neurodegenerative diseases are progressive, so monitoring methods (NfL in the blood, cognitive tests, MRI every 1–2 years) help assess the dynamics and adjust treatment.

How long does a full diagnosis take?
Depending on the methods: from a few days (analyses and tests) to two weeks if MRI, PET or genetic consultation is required. For complex cases, the process may be longer.

Neurodegenerative diseases require a careful and consistent approach to diagnosis. Modern methods make it possible to see changes even before they begin to significantly affect the patient's life. The combination of laboratory indicators, instrumental studies and cognitive tests creates a complete picture, on the basis of which the doctor can choose an individual strategy of observation and therapy. Early diagnosis makes it possible to preserve brain functionality and maintain quality of life in the long term.