SPH405

GOAL: Students will distinguish the communicative functions associated with the PERIPHERAL NERVOUS SYSTEM

OBJECTIVES :

Students will describe or identify the communicative and swallowing functions associated with each of the twelve CRANIAL NERVES on the section test at 90% accuracy.

Students will describe or identify the communicative functions associated with the SPINAL NERVES on the section test at 90% accuracy.

Students will demonstrate a satisfactory CRANIAL NERVE SCREENING appropriate to the speech/language evaluation to the instructor's standards before the end of the term.

THE PERIPHERAL NERVOUS SYSTEM

Our study of the Peripheral Nervous System will focus on the afferent and efferent functions of the cranial and spinal nerves as they apply to communication and swallowing. These are the domains of clinical Speech-Language Pathologists and Audiologists. Note, too, that some of the cranial nerves have functions that do not relate directly to communication. For example, Vagus Nerve supplies, "General Visceral Efferent impulses to the cardiac m.m. and to m.m of the esophagus, bronchi, lungs and intestines." (A. Foley, 1975). These functions are important, of course, but not to communication per se.

In addition, we will not look closely at the Autonomic Nervous System, a division of the Peripheral Nervous System, as you will recall, preferring to devote most of our attention to the aforementioned voluntary, conscious functions mentioned above.

COMMUNICATIVE FUNCTIONS OF THE CRANIAL NERVES

1. Let look at the CRANIAL NERVES overall and group their communicative functions into EFFERENT AFFERENT categories.
   
   
   1. EFFERENT functions are mainly motor to bulbar musculature. The musculatureas you may recall those which serve biological of eating and breathing overlaid function speaking. Nowbefore some claim swallowing automaticlet us point out that have phases voluntary conscious. Speaking is mostlyalthough we sometimes say things dont mean say.
      
      
      1. Perhaps we should mention the ANS again here. There are some glandular functions associated with digestion, and salivation would be particularly important to swallowing. Saliva contains enzymes that begin the chemical breakdown of food for digestion. Saliva also lubricates the oral cavity for easy movement of the speech articulators. However, salivation is not a voluntary function, and is, thus, not particularly subject to operant conditioning in a therapeutic context. Many will recall that Pavlov conditioned his dogs to salivate, but he used a classical paradigm.
      
      
      
      2. As food passes from the oropharynx into the esophagus, the muscular action propelling it becomes involuntary and autonomic. Before that, swallowing muscles function voluntarily. Dysfunction of visceral motor functions can lead to reflux. In that case, partially digested gastric material is propelled back up into the upper alimentary canal. The presence of digestive acids can cause voice problems as it irritates sensitive mucosal tissues.
      
      
      
   2. AFFERENT functions of the cranial nerves involve the special senses.
      
      
      1. Of these, touch, vision and hearing are probably the most important.
      
      
      
      2. In contrast to the efferent functions, unconscious input of somesthetic senses is extremely important for the smooth, normal function of bulbar musculature.
         
         
         1. All the motor nerves have afferent fibers that transmit impulses to the thalamus to coordinate with the actions of the other motor nerves.
         
         
         
         2. Unconscious input to the Central Nervous System links the muscles to the Cerebellum, Basal Nuclei and other Brainstem pools.
   
   
   
2. TESTING OR SCREENING OF CRANIAL NERVES is a standard way to assess function of the speech mechanism. We will use a general cranial nerve screening procedure as a central activity of this corse. In this way, students will apply the material they pickup in this course to their clinical practices.
   
   
   1. It is good to remember that we are learning a cranial nerve SCREENING. Remember, we are not neurologists. Cranial nerve testing is beyond the scope of our professional responsibility.
      
      
      1. We will not suggest we are testing cranial nerves There are many functions of the cranial nerves that we have no professional need to test.
      
      
      
      2. A neurologist is the professional best equipped to perform cranial nerve testing.
      
      
      
   2. Since the cranial nerves are involved in so many communicative and swallowing functions, we use the format of the cranial nerve screening to provide part of the structure for examining the peripheral speech mechanism.
      
      
      1. This structure is shared by other disciplines that work with our patients and who receive input from our evaluations. These disciplines include...
         
         
         1. Internal Medicine.
         
         
         
         2. ENT
         
         
         
         3. Neurology
         
         
         
         4. Physical therapy
         
         
         
         5. Occupational Therapy
         
         
         
         6. Can you name others?
         
         
         
      2. Thus, we are using a standard format, one that others use. We report our findings in order of the format, number one (olfactory) first and move on through number twelve (hypoglossal).
         
         
         1. We can infer certain functional limitations or potentials from our knowledge of bulbar musculature functions, but must remember these are only inferences.
         
         
         
         2. We do not infer that there is something wrong with the nerve. Indeed, there is usually nothing wrong with the nerve, but, rather, with the collection of CNS tracts that aggregate from various CNS components to impinge upon the peripheral cranial nerve.
         
         
         
         3. What speech-Language Pathologists are most interested in is function. Our framework is useful to examine function. Inferences as to cause are important in planning treatment, including referral to other professionals.
         
         
         
         4. Medical Charts contain the evaluation notes of attending physicians. A cranial nerve screening will often be found under the heading "HEENT"
            
            
            1. These initials refer to "Head, Eyes, Ears, Nose and Throat." Does that sound like something a Speech-Language Pathologist or Audiologist would find interesting? Well, it usually boils down to a cranial nerve screening, just like the one we're going to learn. The items tested will be indicated by the simple notation of a Roman numeral for each nerve/function screened.
            
            
            
            2. If you should find this information in a patient's chart, you might elect to bypass doing your own screening. I recommend against this for two reasons.
               
               
               1. We're interested in focusing on communicative functions and in swallowing, and may want information the physician has left up to us to determine.
               
               
               
               2. It's not a bad idea to follow up on the physician's findings. Maybe the patient recovered some function between the time the physician first saw him/her and your evaluation visit. This would be valuable information and would have implications for treatment.
   
   
   
3. THE CRANIAL NERVES: the cranial nerves each are identified by a name and a Roman numeral. You should learn both the name and the numeral, and associate both with their communicative and swallowing functions.
   
   
   1. I : OLFACTORY, is for SMELL.
      
      
      1. What is the communicative function of smell? This is a question I ask in my face to face classes. Here are some ideas.
         
         
         1. Smell can attract or repel, having a mitigating effect on the communicative environment
         
         
         
      2. SCREENING: Ask the patient if she/he has noticed any changes in the way things smell or taste.
         Remember, taste and smell are pretty difficult to distinguish. One good way to think about it is to recall how things taste when you have a stuffy nose.. Most often I skip this one, unless there is a good reason to ask the question. For managing deglutition problems, the sense of smell may be important. Remember, the olfactory sense is the only one that does not relay through the Thalamus.
      
      
      
   2. II. OPTIC, is for VISION. Is vision an asset to communication? Don't forget the importance of facial expression or other gestural means in communication, not to mention the role of vision in graphic communication. What is the role of vision when you are talking on the telephone? I read once that people can tell if you smile when you answer the telephone.
      As we examine the patient's visual function, we are interested here in vision as a sense, beyond cranial nerve function. Notice that we simply arrange our screening in order of the nerve arrangement in a caudal direction along the brainstem: I - II - -III and so on. If our patient has difficulty with vision, there are many possible etiologies apart from II dysfunction. Part of our task is to determine the extent to which vision is a functional modality for the patient and what, if any, aspects of it are detracting from that modality.
      
      One frequent culprit is the need for corrective lenses. Most older folks, your humble professor included, need a little visual help to see things close-up. This condition, "Hypermetropia," requires "'Reading Glasses." It is real easy to forget to find out whether your patient uses reading glasses, and often your patient cannot tell you. In cases like that, you may find yourself wondering if the patient is able to recognize spoken words, when, in fact, he is unable to recognize the pictures you are using to represent those words. Of course, this problem is easy to address. It has nothing to do with the Optic Nerve.
      
      Again, we are examining the general visual sense within the context of Cranial Nerve arrangement.
   
   
   
   3. III; IV; VI control the orbital movements of the eye. III controls the INTRINSIC eye muscles as well as the Medial Rectus, and extrinsic muscle, and the Levator Palpebrae Superiorus muscle (the one that lifts the eyelid). IV and VI provide motor impulses for other extrinsic eye muscles.
      
      Intrinsic muscles have both attachments on the organ of question, in this case, the eye. Extrinsic muscles have one attachment on the organ, and the other somewhere else. In the case to the extrinsic eye muscles, that somewhere else is the orbit.
   
   
   
   4. Disorders of the extrinsic eye muscles cause variations in the smooth, consensual, movement of the eyes. These variations are of great interest to Neurologists and, of course, ophthalmologists.

      Question: Why are variations in ocular control of interest to Speech-Language Pathologists?

      Some of these conditions are:
      

      1. NYSTAGMUS is the condition in which the movement of the eyes is not smooth.
         
         
         1. It can be voluntary or involuntary. If it is voluntary, the eyes will "Wiggle" as the patient tries to converge on an object. If "Involuntary," the eyes will be in constant movement.
            
            
         2. It is tested by caloric means. The audiologist or other specialist fills the ear canal with hot or cold water and observes its effect.

         
         Question: Why is an audiologist interested in Nystagmus?
         

      2. EXOPHORIA is when the eye deviates outward (to temporal half)
      
      
      
      3. ESOPHORIA is when the eye deviates inward to nasal half.
      
      
      
      4. Vol. eye field is important for reading and tracking.
      
      
      
      5. Following movement is not the same as directed eye movement.
      
      
      
   5. V: TRIGEMINAL, has efferent and afferent functions:
      
      EFFERENT: controls MOTOR FUNCTION TO THE MUSCLES MASTICATION (except the buccinator).
      
      
      1. Especially muscles mandibular elevation and lateralization
      
      
      
      2. Vowels and consonants that require elevation of the mandible.
      
      
      To examine this function, ask the patient to make "Chewing Movements" with her/his mandible. The alert clinician will notice whether these movements are VERTICAL and ROTARY. Vertical mandibular movement is simple, straight up mandibular elevation. Vertical movement is essential for articulation of certain phonemes (Question: what phonemes?) And biting. Gravity lowers the mandible, as long as the patient is upright. "Rotary" chewing is necessary to thoroughly grind food up and mix it with saliva. Rotary chewing is very important in nutrition and food bolus management.
      
      So, back to the screening. We want to know if the mandibular elevators are functional, and we are using the cranial nerve screening format to do so. Why?
      
      AFFERENT: conveys SOMESTHETIC IMPULSES from the FACIAL DERMATOMES.
      
      Dermatomes are areas of somesthetic sensitivity on the skin. The Trigeminal Nerve conveys "General Somatic Afferent" (GSA) impulses from theses dermatomes to the Brain, via the "Trigeminothalamic" tracts. There are three dermatomes on the face, one to go with each of the three branches of the TRIgeminal Nerve. Remember: there are two Trigeminal nerves, one on each side. That makes for six facial dermatomes.
      
      OPHTHALMIC DIVISION: ("V -1" (Stands for Roman Numeral, "V" and first branch.): fibers convey afferent impulses from several areas of the anterior/superior skull, including, the skin of the face at the V-1 dermatome (orbital region, forehead, scalp to the vertex of the skull.
      
      If you can't elicit a voluntary response from your patient, you may want to examine a PALPEBRAL reflex. Take a wisp of cotton or other light tissue, and brush the lateral angle of each eye. Be sure to make contact with the skin at the angle. You don't really have to try to touch the sclera of the eye, (and, in fact, you probably don't really want to). You are trying to elicit a blink. If you do, you may infer that the patient felt, on some level, the touch of the tissue.
      
      If your patient blinked before you actually made contact with the skin, it was probably a protective, automatic blink, elicited by the approach of the tissue, implicating the visual modality for the input. If you made contact, it may have been either vision or touch that elicited the blink. It there was no blink, either the input or the output limb of the reflex is implicated. It is your job to infer which.
      
      MAXILLARY DIVISION (V-2): The face about the upper lip, nose, lower eyelids, and zygomatic regions; mucous membranes of the palate, nasal septum and underlying tissues and the upper teeth.
      
      MANDIBULAR DIVISION (V-#) somesthetic impulses come from, among others, from the lower jaw and cheek, anterior 2/3 of the tongue; Mandible and lower teeth.
      
      To assess the important function of somesthesis from the face and anterior oral cavity, tell the patient what you are going to do, and what you expect him to do. Next, take a sterile object, such as a tongue blade, and touch the patient at one of the dermatomes. Ask him to touch where you just touched. Repeat the process until you feel confident that he knows what to do. Now, you have to get your patient to close his eyes, since you don't really want interference from the visual modality. Touch the patient at each of SIX (three on each side) facial dermatomes, and observe his response. Does he have difficulty "Crossing the Midline?" Note if there is any failure to respond and at which dermatome such failure occurs.
      
      Failure to respond may not mean any difficulty with somesthetic perception at the facial dermatomes. It may mean paralysis of some sort which prevents the patient from touching his face. It may mean lack of cooperation. It is your job to infer which.
   
   
   Question: Of what importance to communication is somesthesis from the oral cavity?
   
   
   6. VII: Facial: Motor to the MUSCLES OF FACIAL EXPRESSION and Sensory to the taste buds on the anterior 2/3 of the tongue.
      
      Motor function of the muscles of facial expression are important to spoken as well as gestural communication. Several phonemes of English are formed completely or partially through action of the lips. (Question: Which ones?). A good exercise for you is to try to speak without moving your lips. Now try to speak without facial expression. What happened?
      
      To screen facial motor function, ask the patient to spread her lips as though she were saying /i_/ then have her prolong /u_/. Notice I didn't say, "Have the patient smile." Part of the screening is to distinguish between a "Voluntary" Smile" and a "Visceral" smile. The "Voluntary" smile is a function of the Corticobulbar ("Upper Motor Neuron") tracts. The "Visceral" smile originates in the Hypothalamus. It is not under voluntary control. Thus, a patient with upper motor neuron disease of the tract s of VII would show no "Voluntary" smile, yet would still smile "Viscerally."
      
      There is another hitch. The UPPER muscles of facial expression are innervated bilaterally (tracts run from each hemisphere to both sides of the face). The lower muscles of facial expression (Below the zygomatic region) are innervated unilaterally. The most frequently observed clinical manifestation is of unilateral upper motor neuron paralysis associated with a cerebral vascular accident (CVA; Stroke). Such patients have damage to the motor strip of one hemisphere. The other hemisphere is fine. In that syndrome, a patient will demonstrate unilateral, contralateral voluntary paralysis of the LOWER muscles of facial expression, but will present with a bilateral, full smile when emotionally stimulated. Upper muscles of facial expression will be unaffected, since they receive cortocobulbar innervation from an intact cortex.
      
      If a patient has Lower Motor Neuron disease, that is, disease of VII, there would be no movement of the muscles of facial expression.
      
      Another observation for the astute clinician would be whether there is a "Drool Line" around the angles of the mouth. This suggests weakness of the orbicularis oris. Of course, distortion, omission of labial consonants or rounded vowels would be a dead giveaway, too, and more a propos communication.
      
      At te risk of too mush redundancy, let my point out that we are examining the whole function of the facial muscles, not just examining the function of a cranial nerve. The muscles of facial expression are excellent examples of various CNS and PNS component output.
   
   
   NOW: Do you recall the somesthetic pathway from the face back to the brain? What nerve originates the sense of touch, movement and position?
   
   
   7. VIII is the VESTIBULOCOCHLEAR nerve: Its function is related to AUDITION and to maintenance of BALANCE sense.
      
      Function of this nerve may be screened by using a portable audiometer or the auditory pathways may be best tested by an Audiologist. Audiological evaluation is a thorough testing of auditory function. Neurologists test the equilibrium function.
      
      We can ask our patients if they have noticed any ringing (tinnitus) in their ears. Of course, we will observe their responses to auditory input. VIII, which is a part of the Peripheral Hearing System, connects to the auditory centers of the CNS at many levels. But before VII can do anything, it has to get the input from the environment. This means the rest of the peripheral hearing mechanism must be functioning fairly well. On more than one occasion, I have suspected a central auditory dysfunction in a patient who had impacted cerumen.
      
      The communicative function of audition is extremely important. Without hearing, we would not only be unable to discriminate phonemes that other people present us, but we would find it very difficult, if not impossible to monitor our own speech.
      
      To screen the vestibular portion of VIII, ask the patient if he has had any vertigo or dizziness. With out a sense of balance, we wo0uld find it very difficult to explore our worlds as we grow up. Interestingly, if we lost equlibrium in later life, we might very well find it hard to "think" the way we used to.
      
      Question: What is the contribution of our sense of space and position to our cognitive processes?
   
   
   
   8. IX is difficult to test. Its contribution to speech is minimal, but it has a role in deglutition. Since we can not isolate its function, we leave it out of our screening.
   
   
   
   9. X (Vagus) and XI (Accessory) are tested together. For the purposes of Speech Pathology, students would do well to think of them as "Ten-Eleven Complex,"instead of two different nerves. Here's why:
      
      
      1. First of all, they are difficult to separate, anatomically, in the brainstem.
      
      
      
      2. Aberrant fibers of XI join fibers of X to provide Corticobulbar innervation to most of the voluntary musculature of Pharynx. Put another way, Accessory fibers provide motor innervation to the intrinsic SKELETAL muscles of the pharynx. The motor tracts of the Vagus nerve (X) are all autonomic, providing innervation only to smooth or cardiac, or glandular muscles. This, of course, leaves the muscles of the larynx and pharynx right out.
         
         
         1. Motor function to the to the muscles pharynx; larynx, levator Veli Palatini allow for...
            
            
            1. Swallowing;
            
            
            2. Phonation;
            
            
            3. /h/; /z/
            
            
            4. Velopharyngeal function
            
            
            Question: What are the communicative functions of these actions?
            
            
         2. Afferent fibers of X are sensory to the pharynx. Somesthetic input from the pharynx originates over X.
         
         
         
         3. To screen X-XI, observe the patient's phonation. You may do this while she is prolonging he /i/ and the /u/ during the VII phase of the screening. Otherwise, listen for breathy or harsh phonation during some other speech act. Listen for abnormal nasal resonance. The abnormality is usually hypernasality, since Velopharyngeal musculature is dysfunctional (Velopharyngeal Incompetence). See if your patient can retain intraoral air. Note tht some patients can retain air in the oral cavity by using the back of the tongue. This is cheating. If you patient insists on cheating, you'll have to look for other signs.
            
            Of course, the point is to examine any effects on communciative functions. The bottom line is there. If you, as a speech pathologist, feel that there is a disorder of resonance or phonation, then you must act on it. Relate your impressions to your patient. Does she want to try to do anything about it? Probably not, if she's cheating on the "Oral Air Retention" task. OK.
   
   
   Question: Who's speech is it, anyway?
   
   Question: What is the function of somesthesis from the pharynx?
   
   
   10. XII: HYPOGLOSSAL innervates INTRINSIC AND EXTRINSIC MUSCLES OF THE TONGUE.
       
       
       1. Intrinsic muscles elevate the tongue tip, retroflex the tip, fold blade. Hump up the body and, overall, provide a huge range of possible configurations for this muscular organ.
       
       
       
       2. Any consonant that is not "Bilabial" "Pharyngeal" or "Glottal" is formed by manipulating the tongue. All the vowels require configurations of the oral cavity, produced by altering the shape or position of the tongue. That's a lot of phonemes, huh?
       
       
       
       3. Extrinsic muscles change the position of the tongue body.
          
          
          1. Probably the most important of these for our screening purpose is the Geniohyoid muscles originates inside the mandible and inserts in the inferior tongue.
          
          
          
          2. Palatoglossus elevates back of tongue: / k/ /f/ and /_/, and for moving a bolus posteriorly during deglutition.
          
          
          
       4. SPINAL NERVES provide sensory and motor innervation to the segmants of the body. There are some important spinal nerve functions involved in communication.
          
          
          1. The PHRENIC NERVE is formed by an aggregation of Cervical Nerves C-3; C-4 and C-5. It innervates the DIAPHRAGM the most important muscle of respiration.
          
          
          
          2. The BRACHIAL PLEXUS arises from Cervical Segments 5; 6; 7; and T-1. It provides sensory and motor function to the upper extremities. Its communicative function involves writing and gesturing.
          
          
          
          
          3. THORACIC NERVES allow for function of the external intercostal muscles to assist in inhalation, and for the accessory muscles of inhalation, as well as the muscles of exhalation, to function in speech.
             
             To screen for respiratory function, observe the length of an adult patient's utterances. Does it seem as tough she is only able to get a few syllables in on one breath? Length of utterance depends, of course, on the patient's developmental stage below about age five. It also depends upon central language functions, affect, and whether the patient feels like talking to you. Some forms of Cerebral Palsy cause a reverse breathing pattern, in which the muscles of the Thorax and the Diaphragm act paradoxically. You'll notice the abdomen distend with Diaphragmatic contraction while the Thorax contracts.
          
          
          Question: What is the role of the muscles of exhalation in speech production?
          
          
          4. LUMBAR nerves provide sensory and motor innervation to the lower extremities. Their communicative functions are to allow the patient to ambulate, explore and relate to the world cor cognitive-linguistic development and functioning in later life. To screen for this, read the chart for the P.T. (preferred) notes, or observe your patient's ability to ambulate.
       
       
       
       5. ONCE WE HAVE MADE OUR OBSERVATIONS, we must interpret them. Any assessment should have at least four components: the subjective impressions of the patient, the observations of the examiner, the inferences of the examiner, and a plan regarding a course of action to take in response to the first three items.
          

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