Neurological Assessment ABC’s
Neurological assessment is the evaluation of the structure and/or function of a person’s nervous system. A doctor or other health care professional performs it to determine the presence or absence of disease of that system, the need for therapy, the type of treatment needed, or a patient’s response to treatment. It consists of the obtaining of subjective and objective health data. The health care provider then interprets that data in the process of forming an impression.
Subjective data is the information which patients provide having to do with the signs and symptoms of nervous system diseases. It might be voluntary or in response to pertinent questions a health care provider might ask. Basic knowledge of some of the signs and symptoms of the more common disorders helps patient’s provide information that is most useful for the neurological assessment.
Objective data is information obtained from the neurological exam and tests. The more common neurological tests which doctors use are the cerebral arteriogram, electroencephalogram, electromyogram, lumbar puncture and the nerve conduction velocity study. CT scans and MRI scans are not exclusive to the evaluation of the nervous system, but when used to image the brain or spinal cord are important neurological assessment tools.
Internists and family practitioners receive basic training in neurology. Therefore, most can perform much of the neurological assessment that many patients require. But more complicated nervous system disorders might require the services of a neurologist.
Neurological Assessment Medical Terminology
Cerebral arteriogram – It is a special x-ray study of arteries of the brain using a special dye (contrast medium) to determine if there is blockage to blood flow. It will also show other structural abnormalities such as an aneurysm or malformation between an artery and a vein. Technical aspects of the procedure are as follows:
- A catheter (thin tube) is inserted into a large artery, preferably femoral artery, depending on the circumstances
- Threading of the catheter into a carotid artery
- injection of the contrast medium into the carotid artery
- Taking a series of x-rays as the dye flows to the brain arteries
Cognition – Is the global conscious mental process of thinking and the understanding that is a part of it. More simply put, it is one’s composite thinking skills. Aspects of it include, but are not limited to knowing, learning, remembering, reasoning and making judgments. – Cognitive –adj.
CT scan (Computerized tomography scan) – It is an x-ray test that produces a three-dimensional image of a part of the body being tested from the computerized conversion of several two-dimensional x-rays of slices of that part taken from different angles. Radiologists who perform the procedure will sometimes use special dye or contrast medium to improve the clarity of the images. CT scans are the test of choice for identifying bleeding in the brain or destruction of bone around the brain or spinal cord. A computerized axial tomography (CAT) scan is the same as a CT scan.
Deep tendon reflex (DTR) – Is the brisk contraction of a muscle in response to a sudden stretching of it resulting from the striking of its tendon with the reflex hammer. It is a test of the function of the motor unit of the muscle responding. The unit includes the muscle itself, the peripheral nerves, the nerve roots and the spinal cord.
Dermatome – An area of the skin that a specified spinal nerve supplies with sensation. There are 8 cervical, 12 thoracic, 5 lumbar and 2 sacral dermatomes matching the number of spinal nerves at those respective levels.
Electroencephalogram (EEG) – It is a test which records the electrical activity of the brain. Its primary uses are the diagnosis of epilepsy, the evaluation of brain function of persons in states of coma, and the identification of events associated with sleep apnea.
Electromyogram (EMG) – It is a test which measures electrical activity in muscles at rest and when they contract. Its use is in the diagnosis of disease or injury to muscle, nerves, or the junctions between muscles and nerves. It establishes the diagnosis of myasthenia gravis. When used in conjunction with a nerve conduction velocity study it also establishes or confirms a diagnosis of carpal tunnel syndrome, peripheral neuropathy and radiculopathy.
Lumbar puncture (LP) – It is a procedure consisting of the placing of a small needle into the subarachnoid space of the lower back and removing a small amount of cerebrospinal fluid. The usual purpose of the procedure is to diagnose or monitor some diseases of the nervous system. Treatment of a disease is a less common reason. Except when the purpose is treatment of a disease, a laboratory conducts test on the fluid based on what the doctor who performs the procedure orders. It is the main means of diagnosing infections of the central nervous system. They include meningitis and encephalitis. Spinal tap is another name for the procedure.
MRA (Magnetic resonance angiography) – It is an x-ray test which uses MRI technology to visualize blood vessels and blood flow. It produces very detailed images in all dimensions. In most parts of the body, the injection of dye produces even greater detail. The clarity of images of some blood vessels might be less than that of a traditional angiogram though. It is frequently the test of choice for individuals with a suspected stroke or aneurysm of the brain.
MRI (Magnetic resonance imaging) scan – It is an x-ray test that uses a strong magnetic field and radio waves to create detailed images of tissues and organs of the body. Subjection of the part of the body under investigation to the magnetic field causes an alignment of the protons of hydrogen ions. Those protons absorb radio waves which cause them to spin. The protons then release energy that sends signals to a coil in the MRI machine. The machine then sends the signals to a computer which processes them and converts them into a 3 dimensional image of the area examined. MRI is the test of choice for evaluating soft tissue of the brain and spinal cord. It gives clearer detail of those tissues than a CT scan. Unlike the CT scan, it does not involve exposure to radiation.
Gadolinium is a metallic contrast agent often used in magnetic imaging procedure to enhance the quality of the images. A contrast medium is an opaque (light does not enter and pass through it) substance. Hence, when introduced into the body it allows distinction of a structure(s) from surrounding tissue(s).
Muscle tone (Tonus) – The steady state of contraction (tension) of muscles and muscle groups caused by the successive flow of nerve signals to them. When normal it serves to maintain posture and prevent passive stretching of the muscles in the resting state.
Myelogram – It is a special x-ray of the spine and subarachnoid space. It consists of the injection of a special dye (contrast medium) into the fluid-filled space. The injection is through a needle inserted through the lower back after numbing of the area much like during the performance of a lumbar puncture. X-rays are then made of the patient’s spine with the patient in different positions so as to observe the flow of the dye within the fluid filled space. A CT scan of the spine is the final step of the procedure. Blockage of the flow of the dye or an abnormal pattern of its flow is indicative of disease conditions. Common diseases it identifies are a herniated disc(s), tumor, narrowing of the spinal canal (spinal stenosis), large bone spurs of the spine, or other conditions resulting in pressure to the spinal cord or nerve roots.
Nerve conduction velocity (NCV) study– It is a test of how well nerves conduct electrical impulses. During the procedure a peripheral nerve(s) is stimulated with an instrument so as to generate electrical signals. The amplitude and speed of those signals are then measured. A decrease in the intensity or speed of transmission of impulses signifies disease or injury of the nerve. When performed in conjunction with EMG it is the chief means of diagnosing peripheral neuropathy, carpal tunnel syndrome and radiculopathy.
Neurological exam – It is the part of a physical examination which a doctor performs that evaluates the status of the nervous system. Its points of focus are a patient’s mental status, cranial nerve function, movements and muscle strength, sensation, deep tendon reflexes, coordination and gait.
Neurology – It is the field of medicine which pertains to the diagnosis and medical treatment of diseases of the nervous system.
Visual evoked response (VER) or Visual evoked potential (VEP) – Is a test for assessing the integrity of the visual pathway from the eye to the brain. From a technical point of view, the test is an EEG of the calcarine cortex of the brain. The VER tests the visual pathway – the function of the optic nerve in particular – by recording brain wave activity in response to visual stimuli. An electrode attached to the scalp overlying the back portion of the brain sends the information to a machine which records it. The recording will show 2 types of spikes. The smaller one represents the stimulus. A larger one occurs when the signal from the stimulus reaches the visual cortex of the brain. The distance between the 2 spikes denotes the speed of conduction of the signal.
The main use of the VER test is in diagnosing multiple sclerosis (MS). It alone does not clinch the diagnosis. But along with other clinical and test data, serves as an aid for doing so. Abnormally slow conduction of signals is indicative of demyelination of the part of the visual pathway proximal to the optic chiasm (optic nerve). A decrease in the amplitude (size) of the second spike denotes inflammation and/or damage to the axons of the nerve.