Reynario C Ruiz Jr. DPEMr. Reynaldo Inocian<br />Module 1The Human-Environment Bridge<br />12 Cranial Nerves<br /><ul><li>Overview:
The physical world is separated by a dimensional gap to the human perception. Humans are “blind” in the sense that they are not capable of conceptualizing the environment around them without a connecting factor to bridge this gap. This connecting factors are the sensory instruments of humans in the form of human organs that capture stimuli from the outside becoming what we call sensations. Through sensations humans are able to live and appreciate and coin the term “world”. Responsible for this phenomenon are the embedded features of the human body that are capable of making connections of the sensation-perception process.
Do an internet search and readings about the 12 cranial nerves.
Download videos form the internet to facilitate understanding on the nature and functions of the 12 cranial nerves.
Read online journals and case studies about the 12 cranial nerve affectation.
Refer also to the following listed books:</li></ul>Berstein, R., Berstein, S., (1996) Biology, Times Mirror Higher Education Group Inc.: USA<br />Leonard, W., (2003) Biology: A Community Context, Mc Graw Hill Companies: USA<br />Estes, Mary Elen Zator (2006), Health Assessment and Physical Examination 3rd Edition, Thomson Learning Asia: Singapore.<br />Giddens, Jean Foret et.al. (2004), Mosby’s Nursing PDQ: Parctical, Detailed, Quick; Elsevier: Singapore.<br />Seley, R., Stephens T., Tate P. (2007) Essential of Anatomy and Physiology 6th Edition, Mc Graw Hill, Inc.: New York.<br />Smeltzer, Suzanne et.al. (2008), Brunner and Suddarth’s Textbook of Madical and Surgical Nursing 11th Edition Volume 2, Lippincott Williams and Wilkins: USA.<br />Smith, Tony (1995) The Human Body: An Illustrated Guide to its Structure, Functions and Disorders, Dorling Kindersley Publishing: London<br />Starr, Cecie (1997) Biology:Concepts and Application 3rd Edition, Wadsworth Publishing Company: USA.<br /><ul><li>Individual Lesson
Submit your answers on or before January 1, 2012.</li></ul>Exploration of the Text:<br />A typical mammalian nervous system is divided into two parts. The central nervous system is responsible for processing information and consists of the brain and the spinal cord. The peripheral nervous system lies outside the central nervous system which are nerves that extends to the rest of the body and is responsible for the sensory and motor functions.<br />Peripheral Nervous system includes thirty-one pairs of spinal nerves which connect to the spinal cord. The system also includes twelve pairs of cranial nerves which connect directly to the brain. Both the spinal and the cranial nerves can be further classified according to functions either sensory or motor. The sensory functions detect and notify spinal cord and the brain of specific changes outside and inside the body such as change in stimulus. The system all has sensory receptors, nerve pathways from receptors to brain, and brain regions that process and translate information into s sensation – a conscious awareness of a stimulus.<br />The motor system is responsible for maintaining body’s posture and balance; as well as moving the trunk, head limbs, tongue and eyes; and communicating through facial expressions and speech.<br />The 12 cranial nerves are usually assigned to Roman numerals I to XII for easy identification purposes. In the medical profession mnemonics are also provided to easily memorize the terms. Figure 1 shows the Roman numeral equivalent of each of the cranial nerve and a way to easily memorize them.<br />There are two general categories of cranial nerve function: the sensory and motor. The motor functions of the cranial nerves are further divided into somatic and parasympathetic. The sensory functions are also divided into special senses such as vision and the general senses such as touch and pain in the face.<br />MnemonicsRoman NumberCranial NerveOhIOlfactoryOhIIOpticOhIIIOcculomotorToIVTrochlearTouchVTrigeminalAndVIAbducent/AbducensFeelVIIFacialAVIIIAcoustic/VestibulocochlearGirl’sIXGlossopharyngealVaginaXVagusSoXISpinal Accessory/ AccessoryHeavenlyXIIHypoglossal<br />The somatic motor nerves innervate skeletal muscles in the head and neck. The parasympathetic cranial nerves innervate glands and smooth muscles. On the part of the cranial nerves some are only sensory and some are motor only. Other cranial nerves are mixed nerves with sensory and motor. Motor nerves can be either somatic or parasympathetic functions.<br /><ul><li>The Cranial Nerves: Functions and Disorders
The Olfactory Nerve is a sensory nerve responsible for olfaction or simply the sense of smell which occurs in response to airborne molecules called odorants that enter the nasal cavity.
The Olfactory nerve is one pair of the nerves. The area in which olfactory nerve arise is situated in the most superior part of the mucous membrane that covers the superior nasal concha. The Olfactory sensory endings are modified epithelial cells and the least specialized of the special senses. The Olfactory nerves connect with the olfactory bulb and the olfactory tract which are components of the part of the brain associated with the sense of smell.
Anosmia is the loss of sense of smell. Total loss of sense of smell may be caused by trauma to the cribriform plate, sinusitis, colds or heavy smoking. Unilateral anosmia (temporary or persistent) may be a result of intracranial neoplasm such as meningioma of the sphenoid compressing the olfactory nerve or bulb.
The Optic nerve is a sensory nerve responsible for vision or the sense of sight. This includes.
Optic nerve is one pair of cranial nerves that transmit visual impulses. It consists mainly of coarse myelinated fibers that arise in the retinal ganglionic layer, , traverse the thalamus and connect with the visual cortex. It functions in the perception of light, shade and objects. The optic nerve fibers correspond to a tract of fibers within the brain.
Myopia (nearsightedness) the axial length of the eyeball is longer than normal, resulting in the image not being focused directly on the retina. This condition can be changed with corrective lenses.
Amblyopia is the permanent loss of visual acquity resulting from strabismus that has not been corrected in early childhood or certain medical conditions.
Color Blindness or Color Vision Defect is designated as red/green, blue/yellow or complete when the person sees only shades or gray. Defects can result from diseases from the optic nerve, macular degeneration, pathology of the fovea centralis, nutritional deficiency or heredity.
The confrontation technique is used to test visual fields of each eye. The visual fields of each eye are divided into quadrants and a stimulus is presented in each quadrant. A normal finding is that a person is able to see that stimulus at about 90° temporarily, 60° nasally, 50° superiorly and 70° inferiorly.
If a person is unable to identify a movement that you perceive, a defect in the visual field is presumed. Defects in the visual field can be associated with tumors or strokes or neurological disease such as glaucoma or retinal detachment.
Normal findings should reveal red reflex. The optic disk is pinkish orange in color, with yellow white excavated center known as the physiologic cup. Light often produces a glistening “light reflex” from the anterior vessel.
Leukocoria or white reflex also referred to as the cat’s eye reflex. The optic disc is pale, there is optic atrophy, edema. The normal hypertensive changes manifest copper wire appearance of the retinal arteries.
Retinal Arteriolar Sclerosis occurs as the walls become thickened and obscure portions of the veins lie underneath. Hypertension causes several abnormalities in the posterior eye.
The retina is pale with the macular region appearing as cherry red spots. This can be indicative of Tay-Sach’s disease. Sharply defined, small red spots are found in and around the macula. These are pathognomonic of diabetes mellitus.
Occulomotor nerve is the nerve responsible for the extraoccular movement or the four of the six extrinsic muscles and upper eyelid; and the puppilary constriction and the control of the lens shape.
The occulomotor nerve is one pair of cranial nerve essential for eye movements, supplying certain extrinsic and intrinsic eye movements.</li></ul>Functioning<br />Cardinal Fields of Gaze<br />Normal<br />Both eyes should move smoothly and symmetrically in each of the six fields of gaze and on the held objects as it moves towards the nose. A few bits of nystagmus or involuntary movement, with extreme lateral gaze can be normal.<br />Disorder<br />Opthalmoplegia is paralysis of one or more of the optic muscles.<br />Doll’s Eye Phenomenon<br />Assess Doll’s eye phenomenon (occulocephalic reflex), test the intactness of the vestibular and occulomotor pathways<br />Normal<br />Normally, the eye should deviate in the direction opposite the head (e.g., head up, eyes look down; head turned to right, eyes look to left).<br />Disorder<br />A person with an abnormal response will have eyes that appear to be painted onto a doll’s head hence the term doll’s eye phenomenon. Loss of doll’s eye phenomenon is abnormal and is demonstrated when the eyes remain fixed with neither lateral nor vertical deviation in response to the head movement.<br />Eyelids<br />Normal<br />The eyelids should appear symmetrical with no drooping infections and tumors. Eyelids of Asians normally slant upwards. When the eyes are focused in the normal frontal gaze, the lid should cover the upper portion of the iris. The person can raise both eyelids symmetrically when the eye is closed, no portion of the cornea should be exposed. Normal lid margins are smooth with the lashes evenly distributed and sweeping upward from the upper lids and downward from the lower lids. Eyebrows are present bilaterally and symmetrical and without lesions or scaling.<br />Disorder<br />Wrinkling of the forehead above the affected eye in an attempt to compensate by using the frontalis muscle to lift the lid.<br />Congenital Ptosis is the failure of the elevator muscle to develop.<br />Lagopthalmus is the inability to bring about complete lid closure.<br />Exopthalmus or Proptosis is an apparent lid retraction, indicating protrusion of the eyeballs.<br />Entropion is the tutning inward or inversion of the lower lid.<br />Hordeolum is an acute localized inflammation, tenderness and redness with the person complaining of pain in the area.<br />Chalazion is the chronic inflammation of the meibomian gland in either of the upper and lower lid.<br />Blepharitis is the bilateral inflammation of the eyelids and are red rimmed with scales clinging to the upper and lower lids. There is itching and burning along the lid margins. There is loss of eyelashes.<br />Xanthelasma is a raised, yellow, non painful plaques are present on the upper and lower lids near the inner canthus.<br />Pupil<br />Normal<br />The pupils should be deep black, round, equal in diameter ranging from 2 to 6 mm. pupils should constrict briskly to direct and consensual light and to accommodation test. Accommodation occurs when pupils constrict and converge to focus on objects at close range.<br />Disorder<br />Amiscoria is the difference in pupil sizes.<br />Deaffernated pupil is damage on the optic nerve in the optic chiasm<br />Hippus phenomenon occurs after the pupils has been simulated by direct light. Light causes pupils to constrict, but the pupils appears to rhythmically vacillate in size from a larger to a smaller diameter.<br />Horner’s syndrome is a unilateral, small regularly shaped pupil. Both pupils react directly and consensually accommodate. Ptosis and absent sweating on the affected side.<br />Adie’s pupil is unilaterally, large regularly shaped pupil. It has a sluggish reaction to light and accommodation. There is blurring if vision accompanied by diminished knee and tendon reflex.<br />Argyil Robertson pupil are bilaterally small and irregularly shaped.<br />Occulomotor nerve damage shows fixed dilated pupil on one side.<br />Cranial Nerve No. IV (Trochlear)<br /><ul><li>The Trochlear nerve is a motor nerve. It is responsible for one of the extrinsic muscle of the eye.
The trochlear nerve is either of the smallest of the cranial nerves, essential for eye movement and muscle sensitivity.
Both eyes should move smoothly and symmetrically in each of the six fields of gaze and converge on the held object as it moves towards the nose. A few bits of nystagmus with extreme lateral gaze can be normal
The Trigeminal nerve is both motor and sensory in nature. It is responsible for the sensation of face, scalp, cornea, oral and nasal mucous membrane and the teeth. Its motor functions are to muscles of mastication of chewing. It has the greatest general sensory distribution of all the sensory nerves and it is the only nerve supplying the sensory information to the brain to the skin of the face. Injections of anesthetic administration carried through branches of the trigeminal nerve from the teeth.
The temporalis and Masseter muscles should be equally strong on palpation. The joint should not deviate and should be equally strong side-to-side movement against resistance. The value and bulk of muscles should be bilaterally equal. Sensation to light touch, superficial pain and temperature should be present on the sensory distribution areas of the trigeminal nerve. The corneal reflex should case bilateral blinking of eyes.
Lesions of the trigeminal nerve may give rise to either reduced sensory perception or facial pain.
Trigeminal Neuralgia (Tic Douloureux) characterized by brief paroxysmal, unilateral facial pain along the distribution of the trigeminal nerve. The pain can be provoked by touch or movement of the face such as in tooths brushing, yawning chewing or talking.
Post Thereptic Neuralgia is found most often in the elderly. Characterized by continuous pain which is constant stabbing, burning ache.
Tetanus is characterized by tonic spasms interfering with muscles that open the jaw (trismus). Dysphagia and spasms of the pharyngeal muscles are also observed in tetanus.
The Abducent or abducent nerve is a motor nerve responsible for the lateral eye movement. It is either of the pair of the 6th cranial nerve. It makes the eye turn outward. The term abducens relates to the tern abduct which means to move away from the central axis of the body.
Phoria is the misalignment of an eye. This condition is a mild weakness elicited by the cover-uncover etst and has two forms: Esophoria: nasal or inward drift and exophoria, a temporal or outward drift.
Truamatic Opthalmoplegia amy cause damage to the extraocular muscles.
Extaocular Muscle palsy and Nystagmus occurs late after the onset of increased intracranial pressure.
The Facial nerve is both a sensory and a motor nerve. The sensory function of the facial nerve is responsible for the taste on the posterior 1/3 of the tongue. The motor function of the facial nerve is responsible to muscles of facial expression, eye closure labial speech and salivary and tear glands.
The nerves arise from the brain stem at the base of the pons and divide in front of the ear into six branches, innervating the scalp, forehead eyelids, muscles of the facial expression, cheeks and jaws
Normal findings of he motor function of the facial nerve include symmetry between the right and the left sides of the face as well as the upper and the lower portions of the face at rest and while executing facial movements. There should be an absence of abnormal muscle movement.
The normal sensation would be accurate perceptions of sweet, sour, salty, bitter tastes.
Bell’s Palsy (idiopathic facial palsy) characterized by complete paralysis of the facial muscles on the involved side. The affected side of the face is smooth, the eye cannot close, the eyebrows droop, the labiofacial fold is gone and the mouth may droop. Loss of sensation of taste in the anterior two thirds of the tongue may occur.
Supranuclear facial palsy is the paralysis of the lower one third to two thirds of the face; the upper portion of the face is spared.
Ageusia (loss of taste), hypogeusia (diminution of taste)
Cranial Nerve No. VIII (Vestibulocochlear/Acoustic)
Vestibulocochlear or the acoustic nerve is responsible for hearing and balance. It is either of the pair of cranial nerves composed of fibers from the cochlear and the vestibular nerve in the inner ear, conveying impulses of both the sense of hearing and the sense of balance.
Normal</li></ul>In a voice whisper test, the person should be able to report words whispered from a distance of two feet.<br />In Weber’s test the person should receive the sound equally in both ears or in the middle. No lateralization of sound is known as a negative weber test.<br />In Rinne’s test, conduction is heard twice as long as bone conduction when the person hears the sound made through the external auditory canal (air) after it is no longer heard at the mastoid process (bone).<br />For its vestibular division, the person should not confess any experience of dizziness.<br /><ul><li>Disorder</li></ul>Whisper-Voice test - The person is unable to repeat the words correctly or states that he or she was unable to hear anything.<br />Weber’s Test – the sound lateralized to the affected ear. Unilateral conductive hearing loss is indicated because the sound is being conducted directly to the bone of the ear. If the sound lateralized to the unaffected ear, sensory hearing loss is present. Sensory hearing loss is related to nerve damage in the impaired ear.<br />In Rinne’s test abnormal results may indicate conductive hearing loss resulting from disease, obstruction or damage to the outer or middle ear. Otosclerosis is a middle ear disease.<br />A disorder in the vestibular function of the nerve may cause vertigo, an uncomfortable sensation to movement of the environment or the movement of self within stationary environment. It is often accompanied by nausea vomiting and nystagmus.<br />Menier’s Disease, characterized by vertigo tat lasts for minutes or hours, low pitched roaring tinnitus, progressive hearing loss, nausea and vomiting. The person also experiences pressure in the inner ear.<br />Cranial Nerve No. IX (Glossopharyngeal)<br />The glossopharengeal nerve is a sensory and a motor nerve. Sensorily its functions are responsible for the taste on the posterior 1/3 of the tongue, the gag reflex, sensation from the eardrum and the ear cannal. Its motor component is responsible for swallowing and phonation muscles of the pharynx<br />CN IX is either of the pair of cranial nerves which is also essential sensation of the viscera and secretion from certain glands<br />Functioning<br />Functioning of this nerve is discussed together with Cranial nerve number X since they are much related to each other.<br />Cranial Nerve No. X (Vagus)<br />The Vagus nerve is either of the longest pair of nerve mainly responsible for both sensory and motor functions. Its sensory function is for the sensation of the pharynx, viscera, carotid body and carotid sinus. Its motor function is for swallowing and talking of the palate, pharynx and larynx.<br />The Vagus nerve is probably the most important parasympathetic nerve in the body. It helps regulate the functions of the thoracic and abdominal organs such as the heart rate, respiration rate and digestion.<br />Functioning<br /> The Glossopharyngeal and vagus nerve are tested together because of their overlapping functions.<br />Normal<br />Hard and soft palates are concave and pink. The hard palate has many ridges, the soft palate is smooth. No lesions or malformations should be noted.<br />When the person says “ah”, the soft palate and the ovula should rise symmetrically. The ovula is midline. The throat is normally pink and vascular and without swelling, exudates and lesions. Normal tonsilar size is evaluated as +1 to +2. This indicates that the tonsils are behind the pillars. The person’s gag reflex should be present but is congenitally absent is same persons.<br />Speech is clear without hoarseness or nasal quality. The person is able to swallow water or oral secretions easily. Taste (sweet, salty, sour and bitter) is intact in the posterior one third of the tongue<br />Disorder<br />Viral Pharyngitis is the redness with white patches of the posterior pharynx.<br />Tonsillitis is the swelling of the tonsils.<br />Diptheria, acute tonsillitis or infectious mononucleosis if there is grayish, membrane covering the tonsils, ovula and soft palate.<br />Hoarseness of voice and indicates damage to CN IX and X especially after surgery.<br />Cranial Nerve No.DisordersIAnosmia (unilateral or bilateral)IIMyopia, Amblyopia, Presbyopia, Hyperopia, Color Blindness, Leukocoria, Retinal arteriolar Sclerosis, Coloboma, Diabetic RetinopathyIIIOpthalmoplegia, Congenital Ptosis, Lagopthalmus, Exopthalmus or Proptosis, Entropion, Hordeolum, Chalzion, Blepahritis, Xanthelasma Anisocoria, Differentiated Pupil, Hippus Phenomenon, Horne;s Syndrome, Adie’s Pupil, Argyil Robertson PupilIVTraumatic Opthalmoplegia, Extraocular Muscle Palsy, Parasellar MeningiomasVTrigeminal Neuralgia, Posthereptic Neuralgia, Trismus in TetanusVIStrabismus or Tropia (Estropia or Exoptropia), Phoria (Esophoria or Exophoria), Traumatic Opthalmoplegia, Extraocular Muscle Palsy, Parasellar Meningiomas, Skew DeviationVIIBell’s Palsy, Supranuclear Muscle Palsy, Ageusia, HypogeusiaVIIIUnilateral Conductive Hearing Loss, Sensoryneural Hearing Loss, Otosclerosis, Vertigo, Meniers’s DiseaseIX and XViral Pharyngitis, Tonsilitis, Diptheria, Unilateral Glossopharyngeal and Vagal Paralysis, Bilateral Vagal Nerve ParalysisXIUnilateral Paralysis of the Sternocleidomastoid, Unilateral Paralysis of the Trapezius Muscle, TorticollisXIIGlossitis, Candidiasis, Leukoplakia Aphthous Ulcer, Bilateral Paralysis of the Tongue, SyringobulbiaUnilateral glossopharngeal and vagal pharyngitis is the unilateral lowering and flattering of the palatine arch, weakness of the soft palate; deviation of the ovula to the normal side; mild dysphagia regurgitation of and inability of the palate to elevate on phonation.<br />Bilateral vagus nerve paralysis is marked with nasal quality of voice, difficulty with gustatural and palatal sounds, servere dysphagia, with liquids, inability of the palate to elevate on phonation.<br />Cranial Nerve No. XI (Spinal Accessory/Accessory)<br />Spinal accessory nerve is a motor nerve functions on the two neck muscles (sternocleidomastoid) and upperback muscles (Trapezius). Accessory nerve is either of a pair of cranial nerve, essential speech, swallowing and certain movement of the head and shoulders. Each nerve has a cranial and spinal part, communicates with certain cervical nerves and connects to the nucleus ambiguous of the brain.<br />Functioning<br />Normal<br />The person should be able to turn head against resistance with symmetrical motion. The person should also demonstrate the ability to shrug the shoulders against resistance with strong symmetrical movement of the trapezius muscles.<br />Disorder<br />Unilateral paralysis of the sternocleidomastoid muscle is present if there is an inability of the head to turn to the affected side and a flat non-contracting muscle on that side.<br />Unilateral paralysis of the trapezius muscle, may be suspected if there is inability to elevate one shoulder, asymmetrical drooping of the scapula and a depressed outline of the neck. The involved shoulder also shows atrophy and fasciculation of the muscles.<br />Troticollis is present if there is a slight or prominent lateral deviation of the person’s neck.<br />Cranial Nerve No. XII (Hypoglossa) <br />The hypoglossal nerve is a motor nerve for the tongue muscle. It is responsible for tongue movement for speech sound articulation and swallowing.<br />Functioning<br />Normal<br />Lingual speech is clear. The tongue is in the midline of the mouth, the dorsum of the tongue should be pink, moist rough (from taste buds) and without lesions. The tongue is symmetrical and without lesions. The ventral surface of the tongue has prominent blood vessels and should be moist without lesions. Wharton’s ducts are patent. The lateral aspect of the tongue should be pink smooth and lesion free.<br />Disorder<br />Enlarged tongue can be associated with myxedema, acromegaly, Down syndrome or amyloidosis.<br />Glossitis if the tongue is red and smooth with absent papillae.<br />Candidiasis if there is thick, white cordlike coating on the tongue that leaves a raw red surface when scraped.<br />Leukoplakia if there is thin, pearly white lesions that coalesce and became thick and palpable in the tongue.<br />Apthous Ulcer (canker sore) associated with stress marked by painful, small round like, ulcerated lesions on the boarders of the tongue.<br />Bilateral paralysis of the tongue if atrophy of the tongue is noted and the inability to protrude the tongue.<br />Syringobulbia or trauma to the CN XII may cause hypoglossal nerve paralysis.<br /><ul><li>Extension:</li></ul>Activity no. 1<br />Conduct an assessment of the 12 cranial nerves to one of your classmates or your colleagues. Record your assessment findings on a long sized bond paper and prepare a PowerPoint presentation and present it to the class.<br /><ul><li>Desired Responses:</li></ul>Learning Output No. 1 Essay<br />Relate the case of the actress Superstar Nora Onor to your knowledge of the cranial nerves. What do you think happened to one of her cranial nerve, what cranial nerve was affected? Support your answer.<br />Learning Output No. 2 Classification<br />Classify the 12 Cranial Nerves based on the criteria below. Use the format below.<br />Sensory NerveMotor NerveSensory-Motor NerveGeneralSpecialSomaticParasympathetic<br />Learning Output No. 3 Diagram Construction<br />Construct a schematic diagram, depicting the 12 cranial nerves, of the flow of the stimuli from the environment to the central nervous system as sensations. Use arrows to indicate direction of flow.<br />Learning Output No. 4<br />In a one long sized bond paper, write your perceived importance and appreciation of the 12 cranial nerves in human life.<br />Learning Output No. 5<br />Gather 1 article, news or clippings on each of the 12 cranial nerve depicting cases of its damage or affectation.<br />