When a neurologic disorder is suspected, doctors usually evaluate all of the body systems during the physical examination, but they focus on the nervous system. They do a neurologic examination, which includes evaluation of mental status, cranial nerves, motor and sensory nerves, reflexes, coordination, balance, walking (gait), regulation of internal body processes (by the autonomic nervous system), and blood flow to the brain. Doctors may evaluate some areas more thoroughly than others depending on what type of disorder they suspect.
Doctors evaluate the following:
The evaluation consists of a series of questions and tasks, such as naming objects, recalling short lists, writing sentences, and copying shapes. The person's answers are recorded and scored for accuracy. If the person reports feeling depressed, doctors ask if there have been any thoughts of suicide.
There are 12 pairs of cranial nerves, which connect the brain with the eyes, ears, nose, face, tongue, throat, neck, upper shoulders, and some internal organs (see Cranial Nerve Disorders:Overview of the Cranial Nerves). How many nerves doctors test depends on what type of disorder they suspect. For example, the 1st cranial nerve (the nerve of smell) is not usually tested when a muscle disorder is suspected, but it is tested in people recovering from serious head trauma (because smell is often lost).
A cranial nerve may be damaged anywhere along its length as a result of injury, impaired blood flow, an autoimmune disorder, a tumor, or an infection. The exact site of the damage can often be identified by testing the functions of a particular cranial nerve.
Motor nerves carry impulses from the brain and spinal cord to voluntary muscles (muscles controlled by conscious effort), such as muscles of the arms and legs. Weakness or paralysis of a muscle may indicate damage to the muscle itself, a motor nerve, the nerve's connection to the muscle (synapse), the brain, or the spinal cord.
Doctors look for abnormalities such as the following:
The doctor inspects the muscles for size, unusual movements, tone, strength, and dexterity. A muscle wastes away (atrophies) when the muscle or the nerves supplying it are damaged or when the muscle has not been used for months for other reasons (such as being in a cast).
Muscles may move without the person meaning them to. For example, tiny muscle twitches (fasciculations) indicate nerve damage to that muscle. Other possible involuntary movements are tremor, twitches (tics), sudden flinging of a limb (hemiballismus), quick fidgety movements (chorea), or snake-like writhing (athetosis). All of these movements suggest damage in the areas of the brain (called basal ganglia) that control motor coordination.
To evaluate muscle tone, doctors first ask the person to completely relax muscles in a limb. Then doctors move the person's limb to determine how much the relaxed muscle involuntarily resists being moved—called muscle tone. Muscle tone that is uneven and suddenly increases as the relaxed muscle is moved (spasticity) may be due to a stroke or spinal cord injury. Muscle tone that is evenly increased may be due to a disorder of the basal ganglia, such as Parkinson disease. Muscle tone that is severely reduced (flaccidity) can indicate a disorder of the nerves outside of the brain and spinal cord (peripheral nerves), such a polyneuropathy (a disorder that affects many nerves throughout the body). However, flaccidity usually develops after injuries that cause paralysis, including spinal cord injuries. When flaccidity results from such a spinal cord injury, muscle tone often gradually increases, eventually resulting in spasticity. If people are afraid or confused during the examination, they may not be able to relax the muscles. In such cases, muscle tone may vary, making it hard for doctors to evaluate.
Doctors test muscle strength by asking the person to push or pull against resistance or to do maneuvers that require strength, such as walking on the heels and tiptoes or rising from a chair. Sometimes weakness is evident when a person uses one limb more than another (for example, when swinging the arms while walking or when holding the arms up with the eyes closed). Knowing which body parts are weak (the pattern of weakness) can help doctors identify what the problem is, as in the following cases:
Weakness may also occur in other patterns, such as the following: .
Sensory nerves carry information from the body to the brain about such things as touch, pain, heat, cold, vibration, the position of body parts, and the shape of objects. Abnormal sensations or reduced perception of sensations may indicate damage to a sensory nerve, the spinal cord, or certain parts of the brain. Information from specific areas on the body's surface, called dermatomes (see Spinal Cord Disorders: Dermatomes), is carried to a specific location (level) in the spinal cord, then to the brain. Thus, doctors may be able to pinpoint the specific level of damage to the spinal cord by identifying the areas where sensation is abnormal or lost.
The surface of the body is tested for loss of sensation. Usually, doctors concentrate on the area where the person feels numbness, tingling, or pain. A pin and a blunt object (such as the head of a safety pin) are used to see if the person can tell the difference between sharp and dull. Doctors also test the person's ability to feel gentle touch, heat, and vibration. To test position sense, doctors move the person's finger or toe up or down and ask the person to describe its position without looking.
A reflex is an automatic response to a stimulus. For example, the lower leg jerks when the tendon below the kneecap is gently tapped with a small rubber hammer. The pathway that a reflex follows (reflex arc) does not directly involve the brain. The pathway consists of the sensory nerve to the spinal cord, the nerve connections in the spinal cord, and the motor nerves back to the muscle. Doctors test reflexes to determine whether all parts of this pathway are functioning. The reflexes most commonly tested are the knee jerk and similar reflexes at the elbow and ankle.
|Reflex Arc: A No-Brainer
A reflex arc is the pathway that a nerve reflex, such as the knee jerk reflex, follows.
A tap on the knee stimulates sensory receptors, generating a nerve signal.
The signal travels along a nerve to the spinal cord.
In the spinal cord, the signal is transmitted from the sensory nerve to a motor nerve.
The motor nerve sends the signal back to a muscle in the thigh.
The muscle contracts, causing the lower leg to jerk upward. The entire reflex occurs without involving the brain.
The plantar reflex may help doctors diagnose abnormalities in the nerve pathways involved in the voluntary control of muscles. It is tested by firmly stroking the outer border of the sole of the foot with a key or other object that causes minor discomfort. Normally, the toes curl downward, except in infants aged 6 months or younger. Having the big toe go upward and the other toes spread out is a sign of an abnormality in the brain or spinal cord.
Testing other reflexes can provide important information. For example, doctors learn the extent of injury in a comatose person by noting whether the pupils constrict when light is shined on them (pupillary light reflex), whether the eyes blink when the cornea is touched (corneal reflex), and how the eyes move when the person's head is turned or when water is flushed into the ear canal. Doctors also check whether the anus tightens (contracts) when it is lightly touched (called the anal wink). If this reflex is present in a person paralyzed after a spinal cord injury, the injury may be incomplete, and the chance of recovery is better than if the reflex were absent.
Coordination, balance, and gait:
Coordination and walking (gait) require integration of signals from sensory and motor nerves by the brain and spinal cord. To test these abilities, doctors ask a person to walk in a straight line, placing one foot in front of the other. They ask the person to use the forefinger to reach out and touch the doctor's finger, then the person's own nose, and then to repeat these actions rapidly. The person may be asked to do these actions first with the eyes open, then with the eyes closed.
For the Romberg test, the person stands still with both feet together as close as possible without losing balance. Then the eyes are closed. If balance is lost, information about position from the legs is not reaching the brain, usually because the nerves or spinal cord is injured.
Autonomic nervous system:
The autonomic (involuntary) nervous system regulates internal body processes that require no conscious effort, such as blood pressure, heart rate, breathing, and temperature regulation through sweating or shivering. An abnormality of this system may cause a fall in blood pressure when a person stands up (orthostatic hypotension), reduction or absence of sweating, or sexual problems such as difficulty initiating or maintaining an erection. Doctors may do a variety of tests, such as measuring blood pressure and heart rate while the person is lying down, sitting, and standing. Or they may remove and examine a small sample of skin (skin punch biopsy) to see whether the number of nerve endings has decreased, as occurs in some polyneuropathies that affect small nerves, including autonomic nerves.
Blood flow to the brain:
A severe narrowing of the arteries to the brain reduces blood flow and increases the risk of stroke. The risk is higher for people who are older, who smoke cigarettes, or who have high blood pressure, high cholesterol levels, diabetes, or disorders of the arteries or heart. Doctors place a stethoscope on the neck (over the carotid artery) and listen for turbulent blood flow through a narrowed or irregular artery (the sound of turbulent blow flow is called a bruit). However, the best way to diagnose disorders of the arteries is to use ultrasonography, magnetic resonance angiography (MRA), computed tomography angiography (CTA), or cerebral angiography (see Common Imaging Tests). Blood pressure may be measured in both arms to check for blockages in the large arteries that branch off from the aorta. Such blockages sometimes result in stroke.
Last full review/revision August 2012 by Michael C. Levin, MD