Cervical spine dermatomes and myotomes Each cervical nerve contributes specific sensory and motor func- tion to the upper extremities. In addition, specific upper extrem- ity reflexes correlate with cervical spine levels. Knowledge of the dermatomes, myotomes, and reflexes by segmental level is im- portant in differential diagnosis, as it allows the clinician to better determine the source of dysfunction. C-Spine Level Dermatome Myotome Reflex C1 -- -- -- C2 Temple, forehead, occiput. -- -- C3 -- --
cases of both headache and neck pain. As such, a thorough physi- cal examination should include assessment of the cranial nerves.
Evidence-based practice: A thorough evaluation of the cervical spine should include assessment of crani - al nerve function. Six of the cranial nerves have been shown to be more frequently affected by serious pa- thologies of the neck. These include cranial nerve V (trigeminal nerve), cranial nerve VI (abducens nerve), cranial nerve VII (facial nerve), cranial nerve IX (glos- sopharyngeal nerve), cranial nerve I (olfactory nerve), and cranial nerve XII (hypoglossal nerve) (Mourad et al., 2021). Cranial nerve function The cranial nerves have sensory functions, including vision, smell, hearing, taste, and facial sensations. The also contribute to eye movement; head, neck, and shoulder function; and jaw, tongue, and throat functions such as speech, swallowing, and gagging. As such, some of the cranial nerves have motor functions, some have sensory functions, and some have both (Taylor et al., 2021). Testing the cranial nerves The cranial nerves can be tested easily and quickly in the clinic as follows. Smell and hearing Cranial nerve I, olfactory nerve: Ask the patient to close their eyes and one nostril, introduce a familiar smell (a Sharpie marker works well in the clinic), and ask them to identify it. Repeat on the op- posite side and note any side- to-side differences. Cranial nerve VIII, vestibulocochlear nerve: Rub your fingers near each of the patient’s ears and note any side-to-side differences. Eyes Cranial nerve II, optic nerve: Ask the patient to cover one eye. Then bring a pen or finger in from four directions diagonally to- ward the center of the visual field. The patient reports when the pen/finger becomes detectable and any visual field cuts are not- ed. Cranial nerve III, oculomotor nerve: Ask the patient to outstretch their arm and raise their index finger. Now have them move the finger toward their nose, following it with their eyes (accommoda- tion or convergence). Side-to-side differences should be noted. Cranial nerves III, IV, and VI, oculomotor, trochlear, and abducens nerves: Move a pen in an H pattern 30 to 40 cm in front of the patient. Ask the patient to follow the target without moving their head. Observe the eyes for symmetry of movement, deviations, lag, or nystagmus. Face, jaw, throat, and tongue Cranial nerve V, trigeminal nerve (sensory): Using a cotton ball, stroke the client’s skin along the ophthalmic division (scalp, fore- head, upper eyelid) and mandibular division (chin, jaw, lower lip). Note any side-to- side differences. Cranial nerve V, trigeminal nerve (motor): Examine the function of the temporalis, masseteric, and pterygoid muscles by palpating the masseter muscles while the patient clenches their teeth and then asking them to open their mouth against resistance. If the pterygoid is weak, the jaw deviates to the side when the mouth is opened. Cranial nerve VII, facial nerve: Ask the patient to smile, frown, raise their eyebrows, and puff out their cheeks while you check for symmetry. Cranial nerve IX, glossopharyngeal nerve: Touching a tongue de- pressor gently to the back of the throat on one side to test the ipsilateral gage reflex can be used to assess for unilateral lesion in the glossopharyngeal nerve.
Entire neck, posterior cheek, temporal area, prolongation forward under mandible. Shoulder area, clavicular area, upper scapular area. Deltoid area, anterior aspect of entire arm to base of thumb. Anterior arm, radial side of hand to thumb and index finger. Lateral arm and forearm to index, long, and ring fingers. Medial arm and forearm to long, ring, and little fingers.
C4
--
--
C5
Shoulder abduction.
Biceps.
C6
Elbow flexion, wrist extension.
Biceps; brachioradialis.
C7
Elbow extension.
Triceps.
C8
Finger abduction.
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Healthcare consideration: Involvement of level-specific neu- ral structures involves assessment of myotomes, dermatomes, and reflexes. Manual muscles testing is often the most com- mon assessment strategy employed to distinguish nerve root involvement. Dermatome testing is ideally done with a pin or with a cotton ball. Testing of specific dermatomes is done and compared bilaterally. In addition, reflex testing in the upper ex- tremity should include the biceps, triceps, and brachioradialis Self-Assessment Quiz Question #30 A common location for cervical radiculopathy is the C6–C7 level. What are the possible sensory and motor radicular symp- toms related to this spinal level? a. Numbness in the shoulder area, weak shoulder abduc- tion, and decreased triceps reflex. b. Numbness on the anterior arm and radial side of the hand, weak shoulder abduction, and decreased triceps reflex. c. Numbness on the anterior arm and radial side of the hand, weak finger abduction, and decreased biceps and brachioradialis reflexes. d. Numbness on the anterior arm and radial side of the hand, weak elbow flexion and wrist extension, and de- creased biceps and brachioradialis reflexes. Cranial nerves Serious pathologies of the neck can potentially result in cranial nerve palsy, especially cranial nerves V, VI, VII, IX, I, and XII (Mou- rad et al., 2021). Subtle cranial nerve palsy is known to be a pre- ischemic feature of carotid artery dissection due to the proximity of the lower cranial nerves (IX, X, XII) to the carotid sheath (Taylor et al., 2021). The lower cranial nerves should be considered in
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