Understanding Neurological Diagnosis: Tests and Procedures

If you’re experiencing neurological symptoms such as persistent headaches, unexplained sleep disturbances, or concerning memory loss, it’s crucial to seek medical advice. These symptoms could indicate a neurological disorder or another underlying health condition. Fortunately, advancements in medical science have significantly improved our ability to diagnose and manage a wide range of neurological disorders. This article serves as a comprehensive guide to the common tests and procedures doctors utilize in Neurological Diagnosis.

The Evolution of Neurological Diagnosis

In stark contrast to medical practices a century ago, where definitive neurological diagnosis often relied on post-mortem autopsies, modern medicine boasts sophisticated tools and techniques. Today, we can assess the living brain and monitor the intricate activity of the nervous system in real-time. This leap in technology empowers doctors with powerful and precise methods for accurate disease diagnosis and for evaluating the effectiveness of various treatment strategies.

Researchers and clinicians now leverage advanced imaging technologies alongside blood and cerebrospinal fluid analysis to effectively detect, manage, and treat brain disorders. Many of these diagnostic tests are minimally invasive and can be conveniently performed in a physician’s office or outpatient facility, posing little to no risk to the patient. While some specialized procedures might require a hospital setting, the overall landscape of neurological diagnosis has become significantly more accessible and patient-friendly.

The past decade has witnessed remarkable progress, particularly in the realms of genetic testing and diagnostic imaging. The mapping of the human genome has unlocked vast knowledge, leading to the development of innovative technologies capable of identifying genetic mutations with greater accuracy. Concurrently, enhancements in imaging techniques have yielded high-resolution visuals, enabling physicians to scrutinize the brain’s structure in unprecedented detail. Specialized imaging modalities can now even reveal subtle changes in brain activity and variations in brain chemistry. Scientists are continuously refining these methods to extract increasingly detailed diagnostic insights, pushing the boundaries of neurological diagnosis.

What to Expect During a Neurological Examination

A neurological examination is often the first step in neurological diagnosis when you present with certain symptoms. You might need a neurological exam if you are experiencing symptoms such as:

Persistent pain in the back, neck, head, or nerve pain like sciatica.
Involuntary tremors.
Muscle weakness or stiffness.
Difficulties with balance and coordination.
Numbness or tingling sensations in the skin.
Changes in senses such as hearing, vision, taste, smell, or touch.
Slurred speech.
Confusion or noticeable changes in mental abilities.
Seizures.

Image: A doctor examines a patient experiencing sciatica pain, a common neurological symptom.

Furthermore, a neurological examination is crucial after any injury that might have affected your peripheral nerves, spinal cord, or brain, such as a traumatic brain injury (TBI).

Levi’s Experience with a Neurological Exam

Image: A young boy, Levi, with his clinician in a medical clinic setting.

Consider Levi, a 14-year-old boy who was hit in the head with a soccer ball during a game. His coach, concerned about a possible concussion, immediately had him sit out. Following the coach’s advice, Levi’s parents took him to the doctor. During the consultation, the doctor inquired about Levi’s symptoms and carefully examined his head. To gain a clearer understanding of his condition, she conducted tests evaluating Levi’s memory, reflexes, and blood pressure. Based on the assessment and Levi’s medical history, the doctor ruled out a concussion but still recommended rest as a precautionary measure. Levi’s story illustrates how a neurological exam can be a crucial first step in neurological diagnosis, even for seemingly minor incidents.

The Process of a Neurological Examination

Image: A doctor uses a reflex hammer to examine a patient’s knee reflexes during a neurological exam.

A neurological examination is typically performed by a neurologist, a specialist in nervous system disorders. However, your general practitioner can also conduct an initial neurological assessment. It’s important to note that symptoms of nervous system disorders and mental health conditions can sometimes overlap. For instance, attention difficulties can be a symptom of both. In some cases, a mental health screening might be conducted before or after a neurological examination to differentiate between these possibilities and ensure accurate neurological diagnosis.

The core components of a neurological examination usually involve assessing:

Movement: Muscle strength, coordination, and gait.
Sensation: Response to touch, pain, temperature, and vibration.
Hearing and Speech: Auditory acuity and speech clarity.
Vision: Visual acuity, eye movements, and visual fields.
Coordination: Fine motor skills and balance.
Balance: Stability while standing and walking.
Mental Status: Cognition, memory, problem-solving, alertness, mood, and behavior.

The examination typically begins in a doctor’s office. In emergency situations, such as after a serious injury, the exam might take place in the emergency room or hospital. The initial steps usually include:

Symptom Inquiry: The doctor will ask detailed questions about your current symptoms.
Medical History Review: They will gather information about your past medical conditions and family history.
Physical Exam: A general physical examination, including checking your head, neck, heart, lungs, abdomen, and sometimes skin.

Following these initial steps, the doctor will perform specific tests to evaluate the functionality of different aspects of your nervous system. The specific tests will be tailored to your symptoms. Tools like a tuning fork (for hearing and sensory tests), a flashlight, and a reflex hammer may be used. The tests may evaluate:

Mental Status: This assessment evaluates cognitive functions like memory, problem-solving, alertness, and mood. You might be asked questions about the date, time, and location, recall a list of items, identify objects, repeat phrases, and draw shapes. These tasks help assess your cognitive abilities as part of neurological diagnosis.
Cranial Nerves: Twelve cranial nerves directly connect the brain to various parts of the head and body, including eyes, ears, nose, face, tongue, throat, shoulders, and internal organs. The doctor will test the cranial nerves relevant to your symptoms. For example, vision tests might involve reading an eye chart, and facial muscle tests could include smiling or tightly closing your eyes. Assessing cranial nerve function is vital in neurological diagnosis.
Movement and Strength: Muscles respond to signals from the brain and nervous system. Muscle strength and flexibility tests can reveal issues within the brain and spinal cord. You might be asked to resist pressure while keeping your fingers spread or to relax your arm while the doctor moves it. These tests are crucial for evaluating motor function in neurological diagnosis.
Coordination, Balance, and Walking: These tests assess how effectively your nervous system controls muscle movements. You might be asked to walk heel-to-toe in a straight line, test your handwriting, or touch your nose with your finger while your eyes are closed. These assessments are important for evaluating cerebellar function and coordination as part of neurological diagnosis.
Reflexes: Reflexes are involuntary movements in response to specific stimuli. For example, tapping your knee with a reflex hammer should cause your lower leg to jerk. Reflex tests demonstrate the functionality of nerve pathways between your spinal cord and muscles. Testing reflexes is a standard component of neurological diagnosis.
Sensory Nerves: Sensory nerve tests evaluate your ability to perceive touch, temperature (hot and cold), vibration, and pain. These tests involve gently touching your skin with different objects, such as a sharp object or cotton swab, and asking you to describe what you feel. Sensory testing is essential in neurological diagnosis to map sensory pathways.
Autonomic Nervous System: This part of the nervous system controls involuntary functions like breathing, heart rate, and digestion. Tests might include checking your blood pressure and heart rate. Evaluating the autonomic nervous system is sometimes necessary for a complete neurological diagnosis.

In infants and young children, the examination is adapted and often relies on observation and play-based activities to assess neurological function.

The results of the neurological examination, combined with your medical history, help the doctor formulate a differential diagnosis – a list of possible conditions. This list guides the decision on whether further diagnostic tests and procedures are needed for a definitive neurological diagnosis.

If any part of your neurological examination reveals abnormalities, your doctor will likely order additional screening tests to aid in reaching a precise neurological diagnosis. The specific screening tests will depend on the suspected conditions.

Common Screening Tests for Neurological Disorders

Following a neurological examination, several screening tests may be employed to further investigate potential neurological disorders. These tests fall into several categories, including laboratory tests, genetic testing, and brain scans.

Laboratory Tests in Neurological Diagnosis

Laboratory tests analyzing blood, urine, or other bodily fluids can provide valuable insights for neurological diagnosis. They can help:

Diagnose infections.
Detect toxins.
Identify clotting disorders.
Reveal the presence of antibodies indicative of autoimmune diseases.
Monitor medication levels, particularly for drugs used to treat epilepsy and other neurological conditions, ensuring correct dosage.

Routine blood tests, often part of a general checkup, offer broad health information, while specialized tests can pinpoint specific neurological concerns. Common laboratory tests used in neurological diagnosis include:

Blood Tests: Can detect infections, toxins, clotting abnormalities, and autoimmune markers. They are also crucial for monitoring drug levels in patients taking medication for epilepsy and other neurological disorders.
Genetic Testing (DNA Analysis): Analyzing DNA extracted from blood or saliva can diagnose hereditary neurological disorders. This is a powerful tool in neurological diagnosis for inherited conditions.
Cerebrospinal Fluid (CSF) Analysis: Examining CSF, the fluid surrounding the brain and spinal cord (obtained via lumbar puncture), can detect meningitis, encephalitis, inflammation (acute and chronic), viral infections, multiple sclerosis, and certain neurodegenerative disorders. CSF analysis is vital in neurological diagnosis for conditions affecting the central nervous system.
Chemical and Metabolic Testing: Blood tests can identify muscle disorders, protein or fat metabolism issues affecting the brain, and other metabolic problems that may manifest neurologically. Metabolic testing is an important aspect of differential neurological diagnosis.
Urine Tests: Urine analysis can reveal toxins, abnormal metabolic substances, disease-causing proteins, or signs of specific infections that can impact the nervous system. Urine tests can be a non-invasive adjunct to neurological diagnosis.

Genetic Testing for Neurological Disorders

Genetic testing plays an increasingly important role in neurological diagnosis. It can be used for individuals with or without a family history of neurological disease to determine if they carry genes known to cause specific disorders. Genetic counseling is often recommended to help individuals understand the purpose and implications of genetic testing results.

Genetic testing for neurological diagnosis should be performed in certified clinical laboratories. Testing can focus on specific genes known to be associated with a particular disease or employ broader approaches like gene panels or whole exome/genome sequencing.

Clinical Genetic Testing: Can target specific disease-causing mutations in known genes or examine panels of genes associated with specific neurological conditions (e.g., infant-onset epilepsy panels).
Whole Exome Sequencing: Analyzes the protein-coding regions of the genome (exomes) to identify mutations.
Whole Genome Sequencing: Sequences the entire genome, providing the most comprehensive genetic information. Exome and genome sequencing are often used to discover new disease-causing genes and can take several months for analysis.

Prenatal Genetic Testing for Neurological Disorders

Prenatal genetic testing offers the ability to detect many neurological disorders and genetic abnormalities before birth, aiding in prenatal neurological diagnosis.

Maternal Blood Screening: Screening a pregnant person’s blood can identify abnormalities suggesting an increased risk of genetic disorders in the fetus.
Quadruple Screen (Quad Screen): This blood test, performed between 15 and 20 weeks of pregnancy, measures levels of four substances (alpha-fetoprotein, human chorionic gonadotropin, estriol, and inhibin-A) to screen for certain genetic disorders, including trisomies like Down syndrome. Abnormal results may indicate conditions like spina bifida or chromosomal abnormalities, but further testing is often needed to confirm neurological diagnosis.
Amniocentesis: Typically performed between 14 and 16 weeks of pregnancy if there is a suspected fetal problem. Amniotic fluid is sampled and tested for genetic defects. Results take 1-2 weeks. Amniocentesis is a more invasive prenatal neurological diagnosis procedure.
Chorionic Villus Sampling (CVS): Done between 10 and 13 weeks of pregnancy, CVS involves taking a small sample of the placenta for genetic testing. CVS is usually reserved for pregnancies with a higher risk of genetic abnormalities (e.g., advanced maternal age or family history). Results are typically available within 2 weeks. CVS offers earlier prenatal neurological diagnosis compared to amniocentesis.

For more detailed information on prenatal genetic testing, resources are available from the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD).

Brain Scans for Neurological Diagnosis

Brain scans are crucial imaging techniques in neurological diagnosis. They can detect a wide range of neurological issues, including:

Tumors
Blood vessel malformations
Stroke
Inflammation
Injuries
Scars
Abnormal brain development
Hemorrhage

Common types of brain scans include:

CT (computed tomography)
MRI (magnetic resonance imaging)
PET (positron emission tomography)
SPECT (single-photon emission CT)

The choice of brain scan depends on the neurological examination findings and the patient’s symptoms. Brain scans are performed by trained technicians in hospitals or outpatient imaging centers.

Computed Tomography (CT Scan)

Image: A modern Computed Tomography (CT) scan machine used for medical imaging.

Computed tomography (CT) scans use X-rays to create detailed two- and three-dimensional images of organs, bones, and tissues. CT scans are valuable in neurological diagnosis because they can:

Pinpoint the affected brain region.
Rapidly detect brain bleeding, crucial in stroke diagnosis.
Determine eligibility for clot-dissolving treatments in stroke patients.
Identify bone and blood vessel irregularities.
Detect brain tumors and cysts.
Diagnose hydrocephalus (cerebrospinal fluid buildup in the brain).
Reveal brain damage from injury.
Spinal CT scans can show herniated discs, spine fractures, or spinal stenosis.

CT scans are particularly useful for patients who cannot undergo MRI scans. However, due to X-ray radiation, CT scans are used cautiously in pregnant women, typically only in emergencies.

During a CT scan:

The scan takes approximately 20 minutes and is usually performed in an outpatient center or hospital.
The patient lies on a table that slides into a doughnut-shaped CT scanner.
A communication system allows interaction with the staff.
X-rays are passed through the body at various angles, detected by a scanner, and processed into cross-sectional images (“slices”).
Sedation may be used for patients who cannot remain still.
Pillows are used for head and body stabilization.
Contrast dye may be injected intravenously to enhance tissue visualization. This may cause a warm or cool sensation or a metallic taste. Contrast-enhanced CT scans improve the accuracy of neurological diagnosis in certain cases.

Magnetic Resonance Imaging (MRI)

Magnetic resonance imaging (MRI) utilizes radio waves and a strong magnetic field to produce detailed images of body tissues. Different magnetic pulse sequences allow MRI to:

Image the brain and spinal cord in high detail.
Measure blood flow.
Reveal mineral deposits like iron.

MRI is a powerful tool in neurological diagnosis and can help diagnose:

Stroke
Traumatic brain injury
Brain and spinal cord tumors
Inflammation
Infection
Vascular problems
Scars
Abnormal brain development
Some neurodegenerative disorders, including multiple sclerosis.

MRI is painless and generally safe, although it can be uncomfortable for obese or claustrophobic individuals due to the enclosed machine and noise. Open MRI machines offer a less confining alternative but may have slightly lower image quality than standard MRI.

During an MRI:

Contrast dye (gadolinium-based) may be injected to enhance image clarity. Kidney function may be checked beforehand due to potential risks in patients with advanced kidney disease.
The patient lies inside a tube surrounded by a powerful magnet.
Jewelry, metal objects, and some clothing must be removed.
Sedation may be needed for young children or patients who cannot remain still.
A detector is placed over the head for brain MRI scans.
Grating or knocking noises are common due to magnetic field changes; ear protection is provided.
MRI creates a strong magnetic field to temporarily align water molecules, then radio waves detect molecule shifts.
A computer reconstructs 2D “slices” or 3D images.
MRI differentiates between bone, soft tissues, and fluid due to water content variations.
MRI scans can last up to an hour, depending on the body area being imaged.

Due to the strong magnetic field, MRI is generally contraindicated for patients with implanted medical devices like pacemakers unless specific protocols are followed. Fetal MRI, which is safe for the fetus as it avoids radiation and contrast dye, may be used when prenatal ultrasound suggests a problem. MRI is a cornerstone of modern neurological diagnosis due to its detailed soft tissue imaging capabilities.

Functional MRI (fMRI)

Functional MRI (fMRI) is a specialized MRI technique that measures blood flow changes to create real-time images of brain activity. fMRI can:

Identify active brain areas and their duration of activity.
Pinpoint brain regions crucial for language, motor function, or sensation before epilepsy surgery.
Be used in research to study head injury and degenerative disorders like Alzheimer’s disease.

fMRI enhances neurological diagnosis by providing information about brain function in addition to structure.

Positron Emission Tomography (PET)

Positron emission tomography (PET) scans create 2D and 3D images of brain activity by detecting radioactive isotopes injected into the bloodstream. PET scans in neurological diagnosis can:

Detect or highlight tumors and diseased tissue.
Show blood flow patterns.
Measure cellular and tissue metabolism.
Evaluate patients with epilepsy or memory disorders.
Show brain changes after injury.
Be used as a follow-up to CT or MRI for a more comprehensive understanding of brain activity.

During a PET scan:

A small amount of radioactive tracer is injected.
The patient lies still while sensors detect gamma rays emitted by the tracer.
A computer processes the data into images displayed on a monitor or film.
Multiple brain functions can be traced simultaneously using different tracers.
PET scans are painless and use low levels of radioactivity.
Scan duration varies depending on the body part being scanned.

PET scans offer metabolic and functional information, complementing structural imaging in neurological diagnosis.

Single Photon Emission Computed Tomography (SPECT)

Single photon emission computed tomography (SPECT) is another nuclear imaging test that assesses brain function. Similar to PET, it involves injecting a tracer. SPECT scans in neurological diagnosis may be used as a follow-up to MRI to diagnose:

Tumors
Infections
Brain regions involved in seizures
Degenerative spine disease
Stress fractures

During a SPECT scan:

The patient lies on a table while a gamma camera rotates around the head, detecting the tracer’s location.
A computer converts the data into cross-sectional slices, creating a 3D image of tracer distribution within the brain.

For seizure evaluation, SPECT scans may be performed twice – a baseline scan and a scan after tracer injection during or shortly after a seizure.

A specialized SPECT scan, the dopamine transporter SPECT scan (DaTscan), is used to aid in the neurological diagnosis of Parkinson’s disease by assessing dopamine transporter levels in the brain.

Image: Lisa, a woman experiencing symptoms that led to a neurological diagnosis, sits with her head in her hand.

Lisa’s Journey to Neurological Diagnosis

Lisa, a 30-year-old woman, experienced muscle stiffness and dizziness, making it difficult to maintain balance while walking. Concerned, Lisa consulted her doctor, who performed a physical examination. Based on her symptoms, the doctor referred her to a neurologist for an MRI scan. The MRI results revealed signs of multiple sclerosis. Lisa was prescribed medication to manage her symptoms and advised to make lifestyle adjustments. Lisa’s story highlights the role of advanced imaging like MRI in achieving accurate neurological diagnosis and guiding treatment.

Additional Tests for Neurological Disorders

Beyond common screening tests, several less frequent procedures are used in neurological diagnosis when standard tests are inconclusive or to investigate specific neurological conditions in more detail.

Angiography

Angiography involves injecting contrast dye into arteries or veins to visualize blood vessels and detect blockages or narrowing.

Cerebral Angiogram: Visualizes arteries and veins in the brain, head, and neck. It can identify aneurysms, vascular malformations, and arterial narrowing or blockages, particularly relevant in stroke neurological diagnosis.
Spinal Angiogram: Detects blood vessel problems in the spinal cord, such as malformations or blockages.
Angiograms can also map tumor blood supply before surgery.

Angiography is typically performed in a hospital or outpatient facility.

During an angiogram:

The patient lies on an imaging table.
A local anesthetic is administered in the groin area.
A catheter is inserted into a major leg artery and guided to an artery in the neck.
Contrast dye is injected, and a series of X-rays are taken as the dye flows through blood vessels. Patients may feel warmth or slight discomfort during dye injection.
The procedure can take up to 3 hours, followed by a 6-8 hour recovery period.

In many cases, less invasive techniques like MR angiography (MRA) or CT angiography have replaced cerebral angiograms for neurological diagnosis.

Biopsy

Biopsy involves removing and examining a small tissue sample.

Muscle or Nerve Biopsies: Help diagnose neuromuscular disorders.
Skin Biopsy: Can measure small nerve fibers or detect metabolic disorders.

Biopsies are usually outpatient procedures.

During a biopsy:

A small muscle, skin, or nerve sample is removed under local anesthesia.
Muscle biopsies can be surgical (small incision) or needle biopsies (thin needle insertion).
Nerve biopsies usually involve a small incision near the ankle or wrist.

Brain biopsy is a more invasive surgical procedure to remove a small piece of brain tissue or tumor for diagnosis, particularly to determine tumor type or identify infections. It carries inherent risks.

Cerebrospinal Fluid (CSF) Analysis (Lumbar Puncture/Spinal Tap)

Cerebrospinal fluid (CSF) analysis, often obtained via lumbar puncture (spinal tap), is crucial in neurological diagnosis. It involves removing a small amount of CSF for examination. CSF analysis can detect:

Brain hemorrhage (bleeding)
Infections (meningitis, encephalitis)
Multiple sclerosis
Metabolic diseases
Other neurological conditions

Lumbar puncture can be inpatient or outpatient.

During CSF analysis:

The patient lies on their side with knees to chest or leans forward while sitting.
The back is cleaned and locally anesthetized.
A special needle is inserted between vertebrae into the spinal canal to withdraw CSF (about 3 teaspoons).
Patients may feel pressure during needle insertion.
Lying flat for 1-2 hours post-procedure is usually recommended to minimize headache risk due to CSF leakage.

Lumbar puncture carries a small risk of nerve root injury or infection. The procedure takes about 45 minutes. CSF analysis is a valuable tool in neurological diagnosis, especially for inflammatory and infectious conditions of the nervous system.

Electroencephalography (EEG)

Electroencephalography (EEG) monitors the brain’s electrical activity through the skull. EEG is a key test in neurological diagnosis for:

Seizure disorders (epilepsy)
Other disorders affecting brain electrical activity
Sleep disorders
Monitoring brain activity during anesthesia or unconsciousness

EEG is painless, low-risk, and can be performed in a doctor’s office, hospital, or testing facility.

During an EEG:

The patient reclines in a chair or bed.
Small electrodes are attached to the scalp with conductive paste.
Electrodes transmit brain electrical signals to an EEG machine.
Stimuli like flashing lights or certain drugs may be administered.
Patients may be asked to open/close eyes or change breathing patterns.
Brain wave patterns are recorded and analyzed.
Standard EEG tests take about an hour, including setup.

Longer EEGs (4 hours or more), including sleep EEGs, are used for diagnosing seizure or sleep disorders.

In epilepsy surgery evaluations, intracranial electrocorticography (ECoG) may be used. Electrodes are surgically implanted directly on the brain surface to reduce signal interference and precisely locate seizure origins. Patients are monitored in a hospital epilepsy monitoring unit during ECoG. ECoG aids in surgical planning for epilepsy by mapping seizure foci and essential brain areas.

Electromyography (EMG)

Image: A patient undergoing an Electromyography (EMG) test on their arm.

Electromyography (EMG) diagnoses nerve and muscle disorders, spinal nerve root compression, and motor neuron diseases like amyotrophic lateral sclerosis (ALS). EMG measures electrical activity in muscles and is performed in a doctor’s office or clinic. EMG is important in neurological diagnosis of neuromuscular conditions.

During an EMG:

Fine needles or wires are inserted into muscles to detect electrical signal changes at rest and during movement.
Needles are connected to an EMG machine.
Testing lasts an hour or longer, depending on the number of muscles and nerves tested.
Patients are asked about aspirin or blood thinners due to a slight bruising/bleeding risk.
EMG can be somewhat uncomfortable.

Nerve Conduction Study (NCS)

Nerve conduction study (NCS) is often performed with EMG. NCS measures nerve signal transmission ability, speed (nerve conduction velocity), and signal size.

During an NCS:

Electrodes are taped to the skin over muscles.
Electrodes are connected to an EMG machine.
A small electrical pulse is applied to stimulate a nerve.
The nerve signal is displayed on the EMG machine.
Nerve response is analyzed to detect nerve damage or muscle disease.
NCS causes minimal discomfort and is low-risk. NCS complements EMG in neurological diagnosis of peripheral nerve disorders.

Electronystagmography (ENG)

Electronystagmography (ENG) is a group of tests used in neurological diagnosis of involuntary eye movements, dizziness, and balance disorders. ENG is done at a clinic or imaging center.

During an ENG:

Small electrodes are taped around the eyes to record eye movements.
Infrared photography may be used instead of electrodes, with special goggles to record eye movements.
Both methods are painless and low-risk.

Evoked Potentials (Evoked Responses)

Image: A man undergoing an evoked potentials test, assessing sight and hearing.

Evoked potentials, also called evoked responses, are three tests measuring brain electrical signals in response to sound, touch, or sight stimuli. Evoked potentials in neurological diagnosis are used to test:

Sight and hearing (especially in infants and children)
Diagnose multiple sclerosis, spinal cord injury, and acoustic neuroma (vestibular schwannoma).
Monitor brain activity in coma patients.
Confirm brain death.

Evoked potential testing can be done in a doctor’s office or hospital.

During evoked potential testing:

Electrodes are attached to the scalp with conductive paste. Electrodes may also be placed on ears, arms, or legs.
Electrodes measure brain electrical responses to auditory, visual, and electrical stimuli.
A machine records the time for stimuli-generated impulses to reach the brain.

Types of evoked potentials tests:

Auditory Evoked Potentials (Brain Stem Auditory Evoked Response – BAER): Assess hearing loss, acoustic nerve damage, brain stem auditory pathway damage, and acoustic neuromas. Clicks are presented to one ear at a time in a soundproof room with headphones. Each ear is tested twice; the procedure takes about 45 minutes.
Visual Evoked Potentials (VEP): Detect optic nerve damage-related vision loss (e.g., from multiple sclerosis). The patient views a shifting checkerboard pattern on a screen, one eye at a time. Each eye is tested twice; testing takes 30-45 minutes.
Somatosensory Evoked Potentials (SSEPs): Measure nerve responses to electrical stimuli. Electrodes are placed on the scalp, arms, legs, and back to measure signal transmission from peripheral nerves to the brain. Small electrical shocks are delivered to nerves in an arm or leg. SSEPs help diagnose multiple sclerosis, spinal cord compression or injury, and certain metabolic or degenerative diseases. SSEP tests usually take over an hour.

Myelography

Myelography involves injecting contrast dye into the spinal canal to enhance spine imaging via CT or X-ray. Myelography in neurological diagnosis is considered when CT or MRI are inconclusive in chronic back pain diagnosis. Myelograms can reveal:

Cysts in the brain
Tears in the dura mater (brain covering), which can be a surgical complication or injury consequence

Myelography is an outpatient procedure in a hospital or medical center.

During myelography:

Local anesthesia is injected into the lower back between vertebrae.
A small amount of CSF is removed via spinal tap.
Contrast dye is injected into the spinal column, followed by CT scan or X-rays.
Patients may experience pain during spinal tap and headache afterward.
Slight risks include CSF leakage or allergic reaction to dye.
The procedure takes about one hour.

Polysomnogram (Sleep Study)

Image: A patient in a sleep lab connected to polysomnography equipment for a sleep study.

Polysomnogram, or sleep study, measures brain and body activity during sleep. Sleep studies in neurological diagnosis help diagnose:

Sleep disorders: restless legs syndrome, periodic limb movement disorder, insomnia
Breathing disorders: sleep apnea

Polysomnograms are conducted overnight at a sleep center.

During a polysomnogram:

Electrodes are attached to the scalp, eyelids, leg, and/or chin.
Electrodes record brain waves, eye movements, breathing, leg/skeletal muscle activity, blood pressure, and heart rate throughout the night and sleep cycles.
Video recording may capture sleep movements.
Polysomnograms are noninvasive and painless. Skin irritation from adhesive is the most common side effect.

Ultrasound Imaging

Image: A woman receiving a carotid Doppler ultrasound to measure neck artery blood flow.

Ultrasound (ultrasonography) uses high-frequency sound waves to create internal body images. Ultrasound in neurological diagnosis can:

Assess soft tissue anatomy changes, including muscles and nerves.
Be more effective than X-rays for soft tissue changes like ligament tears or soft tissue masses.

Ultrasounds are performed in clinics or doctor’s offices.

During an ultrasound:

The patient lies on a table or reclines.
A gel lubricant is applied to the skin, and a transducer is moved over the body.
Sound wave echoes are recorded and displayed as real-time images.
Ultrasound is painless, noninvasive, and low-risk.
The test takes 15-30 minutes.

Types of neurological ultrasounds:

Carotid Doppler Ultrasound: Measures blood flow in neck arteries and blood vessels.
Transcranial Doppler Ultrasound: Shows blood flow in brain arteries and blood vessels within the skull. Carotid and transcranial Dopplers assess stroke risk.
Duplex Ultrasound: Uses two ultrasound types to visualize and hear blood flow in major arm and leg arteries and veins.

X-rays

Chest and skull X-rays may be part of a neurological diagnosis evaluation. X-rays can image bones and some organs but are less effective for soft tissues. X-rays are quick, noninvasive, and done in doctor’s offices or clinics.

During a conventional X-ray:

A low-dose radiation burst passes through the body onto a photographic plate.
Bones (high calcium content) appear white on film due to greater X-ray absorption than soft tissues.
Vertebral misalignment or fractures are visible within minutes.

Fluoroscopy is a type of X-ray using continuous low-dose radiation to produce real-time motion images of body parts. Fluoroscopy evaluates swallowing and is used in lumbar puncture, angiogram (clot removal), and myelogram procedures.

Latest Advances in Neurological Tests and Procedures

The National Institute of Neurological Disorders and Stroke (NINDS), a leading federal research funder, is dedicated to improving neurological diagnosis and treatment. NINDS-funded scientists are actively developing enhanced screening methods for more accurate and rapid diagnoses and investigating factors contributing to neurological diseases. Technological advancements in imaging are enabling better visualization inside the body with reduced procedural risks. These diagnostic tools remain crucial for clinical research, disease progression understanding, and treatment monitoring in neurological disorders.

Resources for Neurological Tests and Procedures

For further information on neurological disorders and NINDS-funded research, please contact:

National Institute of Neurological Disorders and Stroke
800-352-9424
https://www.ninds.nih.gov

Additional resources for information about neurological diagnosis are available from:

National Library of Medicine
301-496-6308
https://www.nlm.nih.gov/

American Association of Neurological Surgeons
888-566-2267
https://www.aans.org/

American College of Radiology
703-648-8900
https://www.acr.org/

Radiological Society of North America
630-571-2670
https://www.rsna.org/