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Definition: cranial nerves from Dictionary of Psychological Testing, Assessment and Treatment

nerves which enter and leave the brain without the intermediary of the spinal cord. The nerves are numbered (traditionally in Roman numerals) from 1 to 12: I Olfactory, II Optic, III Oculomotor, IV Trochlear, V Trigeminal; VI Abducens; VII Facial; VIII Auditory-vestibular, IX Glossopharyngeal; X Vagus, XI Spinal Accessory, and XII Hypoglossal. Often the nerves are referred to by their number (e.g. the facial cranial nerve is the ‘seventh nerve’). Compare with spinal nerves.


Summary Article: Neurological System and Cranial Nerves
From Nursing: The Ultimate Study Guide

Obtain a history (pretty repetitive, I know). The neurological system is very complex and coordinates many functions in the body. This section will cover the five main tests used to perform an accurate neurological exam: (a) level of consciousness (LOC), (b) cranial nerves, (c) motor function, (d) sensory function, and (e) deep tendon reflexes.

Level of Consciousness

Assess the patient's mental status. Ask the patient to identify self, place, and time. If there is no alteration in mental status, document the findings as “patient is alert and oriented times 3.” If the patient is slightly confused and cannot state the time or place, document the findings as “patient is alert and oriented times 2 or 1,” meaning they are slightly confused. Older patients with dementia (e.g., Alzheimer's) often show declines in mental status and the ability to answer questions appropriately. Assess for any new changes in mental status, slurred speech (sign of stroke), and, in older patients, urinary tract infections (UTI), which can alter a patient's mental status. It is always important to obtain labs and urine cultures.

Cranial Nerves

So sorry to break it to you, but you will be tested on the 12 ­cranial nerves! Cranial nerves originate from the brain and perform different functions in the body. The cranial nerves are:

  • Cranial nerve I: The olfactory nerve functions in the sense of smell.

  • Cranial nerve II: The optic nerve functions in the ability to see. Visual acuity and visual fields are assessed.

  • Cranial nerve III: The oculomotor nerve functions in pupil response and lid movement. Assess by the response of the eyes to light.

  • Cranial nerve IV: The trochlear nerve functions in eye movement. It is assessed by testing extraocular movements using the cardinal fields of gaze.

  • Cranial nerve V: The trigeminal sensory nerve is the largest cranial nerve and plays a role in the sensory function of the nose, eyes, tongue, and teeth. This is assessed by applying a light touch to the cheek, forehead, and jaw. Typically, the end of a cotton swab is used on the three dermatomes, while asking the patient if he or she is able to feel the sensation. The patient should also be asked to clench the jaw, to assess for muscle strength.

  • Cranial nerve VI: The abducens nerve performs the function of the lateral eye movement. It is assessed by using the cardinal field of gaze.

  • Cranial nerve VII: The facial motor nerve functions in the ability to perform facial expressions. It is assessed by having the patient smile, clench teeth, and wrinkle the forehead.

  • Cranial nerve VIII: The acoustic nerve functions in the ability to hear. Assess the patient's ability to hear by using the whisper test. This can determine whether the patient is hard of hearing.

  • Cranial nerve IX/X: The glossopharyngeal/vagus nerve controls the tongue and palate. Assess the patient's ability to swallow produce the gag reflex.

  • Cranial nerve XI: The spinal accessory nerve governs head control. Assess by having the patient turn his or her head and pressing against the shoulders, assessing for resistance and strength.

  • Cranial nerve X: The hypoglossal nerve controls the tongue function. Assess by having the patient stick his or her tongue out and making sure the tongue is midline.

Document any findings.

Motor Function

Motor function is the ability to evaluate the strength of muscles in the upper and lower extremities. To examine the upper extremities, ask the patient to press against your arms while assessing the strength of each arm. Strength should be equal in both arms. To assess the lower extremities, ask the patient to press his or her legs against your hands, assessing for strength and resistance. Strength should be equal in both legs.

To assess whether the patient has a steady or unsteady gait, ask the patient to walk in a straight line. While the patient is walking, assess for weakness or the inability to ambulate. Document any findings.

Sensory Function

Sensory function is the body's response to light touch, vibration, and pain sensations. Light touch is assessed by using a cotton ball to touch the major dermatomes while looking at the response to the sensation. Vibration is assessed by using a tuning fork to apply sensation, and asking the patient if he or she can feel the vibration. To elicit the sensations of pain, gently use a paper clip or the end of a tongue blade.

Document the findings.

Deep Tendon Reflexes

Deep tendon reflexes are the response of reflexes in the triceps, biceps, brachioradialis, patellar, and Achilles tendon. This response is assessed by gently tapping on the reflex to stimulate a response. The response of reflexes is graded as follows: 4+ ­indicates a brisk and hyperactive response, 2+ is a normal response, and 0 means no response. Document the findings.

© 2015 Springer Publishing Company, LLC.

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