Section 6. Brain, Spinal Cord, and Nerve Disorders

Chapter 77. Diagnosis of Brain, Spinal Cord, and Nerve Disorders

Topics: Introduction | Medical History | Physical Examination | Diagnostic Procedures

Physical Examination

When a neurologic disorder is suspected, doctors usually evaluate all of the body systems during the physical examination but focus on the nervous system. The neurologic aspect includes evaluation of mental status, cranial nerves, motor and sensory nerves, reflexes, coordination, stance, gait, regulation of internal body processes (by the autonomic nervous system), and blood flow to the brain.

See the sidebar What Is a Neurologic Symptom?

Mental Status: Doctors evaluate the person's attention; orientation to time, place, and person; memory; and various abilities, such as thinking abstractly, following commands, using language, and solving math problems. 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. Mood is also evaluated. If the person reports feeling depressed, doctors ask if there have been any thoughts of suicide.

See the table Mental Status Testing.

Cranial Nerves: Doctors test the function of the 12 cranial nerves, which are connected directly to the brain (see Section 6, Chapter 96). How many nerves are tested depends on what type of disorder is suspected. For example, cranial nerve I (the nerve of smell) is not usually tested when a muscle disorder is suspected, but it is tested when a head injury has occurred. A cranial nerve may be damaged anywhere along its length as a result of an injury, a tumor, or an infection. The exact site of the damage must be identified.

Motor and Sensory Nerves: Motor nerves carry impulses from the brain to the voluntary muscles (muscles controlled by conscious effort), such as leg muscles. Weakness or paralysis of a muscle may indicate damage to a motor nerve. Doctors look for muscle wasting (atrophy), which results when a motor nerve is not stimulating the muscle, and then test for weakness in various muscles by asking the person to push or pull against resistance.

Sensory nerves carry information 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. Doctors may be able to pinpoint the specific location (level) of damage to the spinal cord by evaluating sensory nerves. Sensory nerves carry information from specific areas on the body's surface, called dermatomes (see Section 6, Chapter 93), to a specific level of the spinal cord. Therefore, loss of sensation in areas on the body's surface supplied by a specific level of the spinal cord and the levels below it indicates damage to that level of the spinal cord.

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 is used first, then a blunt object (such as the head of a safety pin) to see if the person can tell the difference between sharp and dull sensations. The person's ability to detect a gentle touch, heat, and vibration may be tested. To test position sense, doctors tell the person to close the eyes; then they move the person's finger or toe up or down and ask the person to describe its position.

Reflexes: 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) is a complete circuit, without involvement of the brain. Doctors test reflexes to determine whether the sensory nerve to the spinal cord, the nerve connections in the spinal cord, and the motor nerves back to the muscle are all functioning. The reflexes most commonly tested are the knee jerk and similar reflexes at the elbow and ankle.

See the figure Reflex Arc: A No-Brainer.

A test for Babinski's sign is performed 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.

Coordination, Stance, and Gait: To test coordination, doctors ask a person first to use the forefinger to reach out and touch their finger, then the person's own nose, and then to repeat these actions rapidly. The person may be asked to perform these actions first with the eyes open, then with the eyes closed. For the Romberg test, the person may be asked to stand still with both feet together and the eyes closed. Then the person may be asked to walk in a straight line, placing one foot in front of the other. These actions test the motor and sensory nerves as well as brain function. Other simple tests may also be performed.

Autonomic Nervous System: The autonomic (involuntary) nervous system regulates internal body processes that require no conscious effort. An abnormality of this system may cause such problems as a fall in blood pressure when a person stands (orthostatic hypotension), reduction or absence of sweating, or sexual problems such as difficulty initiating or maintaining an erection. Doctors may perform a variety of tests, such as measuring blood pressure while the person is sitting and after the person stands.

Blood Flow to the Brain: A severe narrowing of the arteries that carry blood to the brain reduces blood flow and puts a person at risk of stroke. The risk is higher for people who are older or who have high blood pressure, diabetes, or disorders of the arteries or heart. To evaluate the arteries, doctors place a stethoscope on the neck and listen for characteristic sounds caused by turbulent blood flow through a narrowed area (bruits). However, procedures such as color Doppler ultrasonography, magnetic resonance angiography, or cerebral angiography are needed for an accurate evaluation of narrowed arteries.