How to Assess CNS

The central nervous system (CNS) is the most important system in the human body. It includes only the brain and spinal cord. CNS damage can occur from a variety of conditions, including, but not limited to, physical trauma, infection, toxin ingestion, stroke, aneurysm, birth injury, congenital disease and an autoimmune disorder. Medical providers assess the CNS in numerous ways. In emergency situations, they use the Glasgow Coma Scale. In other situations, they use a neurological examination to assess both the CNS and peripheral nervous system (PNS).

Things You'll Need

• Pen light
• Reflex hammer

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Instructions

• 1

  Apply the Glasgow Coma Scale to assess a person's CNS in emergencies. It is an objective scale that quantifies the CNS functions of eye, verbal and motor response. A score of 15 indicates normal function of spontaneous eye opening, fluent verbal conversation and movement upon command. One point is removed for each degree of loss of function. A minimal score of 3 indicates no eye opening, no verbal sounds and no movements.

• 2

  Examine the patient's mental status. The best method is a combination of observation and directed questions to gauge the individual's general appearance, behavior, speech, thought content and mood. CNS disorders that the exam may suggest include Alzheimer's disease, stroke and dementia.

• 3

  Test the individual's cranial nerves. Twelve cranial nerves, CN I through XII, arise from the CNS and perform important and complex functions. CN I is involved with the sense of smell and is often omitted from testing. Test CN II, which is involved with vision, by having the patient read eye charts or count fingers, or use a pen light to look for pupil constriction in the patient. CN III, IV and VI are involved with eye movement; test them by asking the patient to follow your moving fingers. CN V is involved with face sensation, and you can test it by touching different parts of the individual's face. Examine CN VII, which is involved in facial movement, by asking the patient to show his teeth or raise his eyebrows. CN VIII is involved in hearing. CN IX and X are involved in speaking and swallowing. Test CN XI by asking the patient to shrug his shoulders. Examine CN XII, which controls the tongue, by having the patient move his tongue from side to side outside of his mouth.

• 4

  Measure the person's strength. Strength is measured on a scale from 0 to 5 for each major muscle movement. A score of 5 indicates full strength, 4 indicates movement against resistance but less than normal strength, 3 indicates movement against gravity but not resistance, 2 indicates movement at a joint but not against gravity, 1 indicates visible muscle movement but no movement at a joint and 0 indicates no muscle movement. Major muscle movements include elbow flexion and extension, wrist flexion and extension, knee flexion and extension, and ankle flexion and extension.

• 5

  Examine the patient's sensation of pain, temperature, touch, position and vibration. You may test each of these sensations separately, and the most common way to assess CNS sensory function is with touch. Sensation in each part of the body is supported by a nerve group called a dermatome. For example, the dermatome that supports the index finger differs from the dermatome that supports the middle finger. Sensation is tested best at the extremities, in fingers and legs.

• 6

  Test the individual's deep tendon reflexes with a reflex hammer. Reflexes are an important way to distinguish between CNS disorders and PNS disorders. Deep tendon reflexes are increased or stronger in CNS disorders, and they are decreased or weaker in PNS disorders. Common deep tendon reflexes that are tested include the knee, ankle, biceps and triceps.

• 7

  Examine the patient's coordination and gait to assess a special part of the CNS called the cerebellum. Test coordination in an individual's upper extremities by having her rapidly tap her nose and another person's finger with the index finger of each hand. Examine coordination in her lower extremities by asking her to stand straight with her eyes closed. To test her gait, watch her walk across a room.