Cranial Nerves, Parasympathetic Ganglia Of The Head And Cranial Nerves Clinical Testing

Cranial Nerves

Nerve Components Cell Bodies Peripheral Distribution Function I Olfactory SVA Olfactory epithelial cells Olfactory nerves Smell II Optic SSA Ganglion cells of retina Rods and cones Vision III Oculomotor GSE Nucleus III Levator palpebrae; recti: superior, medial, inferior; and inferior oblique Eye movement GVE Edinger-Westphal nucleus Ciliary ganglion—Ciliary body—Sphincter pupillae Contraction of pupil and accomodation GP Mesencephalic nucleus V Ocular muscles Kinesthetic sense IV Trochlear GSE Nucleus IV Superior oblique Ocular movement GP Mesencephalic nucleus V Superior oblique Kinesthetic sense V Trigeminal GSA Trigeminal ganglion Ophthalmic, maxillary, and mandibular divisions to mucous membranes and skin of face and head General sensation SVE Motor nucleus V Temporalis, masseter, pterygoids, anterior belly of digastric, mylohyoid, tensors palatini and tympani Mastication GP Mesencephalic nucleus V Muscles of mastication Kinesthetic sense VI Abducens GSE Nucleus VI Lateral rectus Eye movement GP Mesencephalic nucleus V Lateral rectus Kinesthetic sense VII Facial SVE Motor nucleus VII Muscles of facial expression, stapedius, stylohyoid, post, belly of digastric Facial expression GVE Salivatory nucleus Greater petrosal— pterygopalatine ganglion—nasal mucosa, lacrimal gland; chorda tympani—lingual nerve, submandibular ganglion—submandibular, sublingual glands Secretomotor SVA Geniculate ganglion Chorda tympani—lingual nervetaste buds anterior two-thirds tongue Taste GVA Geniculate ganglion Greater petrosal, chorda tympani Visceral sensation GSA Geniculate ganglion Auricular branch—ear and mastoid Cutaneous sensation VIII Vestibulocochlear SSA Spiral ganglion Organ of Corti Hearing SP Vestibular ganglion Vestibular mechanism Balance IX Glossopharyngeal SVA Inferior ganglion IX Lingual br.—taste buds posterior one-third tongue, circumvallate papillae Taste GVA Inferior ganglion IX Tympanic nerve—middle ear, pharynx, tongue, carotid sinus Visceral sensation GVE Salivatory nucleus Tympanic—lesser petrosal—otic ganglion auriculotemporal to parotid gland Secretomotor GSA Inferior ganglion IX External ear Cutaneous sensation SVE Nucleus ambiguns Stylopharyngeus Swallowing X Vagus GVE Dorsal motor nucleus X Cardiac nerves and plexus, ganglia on heart; pulmonary plexus, ganglia respiratory tract; esophageal, gastric, celiac plexus; myenteric and submucous plexus—to transverse colon Smooth muscle and glands SVE Nucleus ambiguus Pharyngeal br., superior, inferior laryngeal nerves Swallowing, speaking GVA Inferior ganglion X All fibers in all branches Visceral sensation SVA Inferior ganglion X Br. to epiglottis, base of tongue, taste buds Taste GSA Superior ganglion X Auricular br.—ear, meatus Cutaneous sensation XI Accessory SVE Nucleus ambiguus Communication to vagus—muscles of pharynx and larynx Swallowing, speaking SVE (Assuming branchiomeric origin) Upper spinal cord—lat. column Spinal portion—sternocleidomastoid, trapezius Movement, head and shoulder XII Hypoglossal GSE Nucleus XII Brs. intrinsic, extrinsic muscles of tongue Tongue movement GP, general proprioception; GSA indicates general somatic afferent; GSE, general somatic efferent; GVA, general visceral afferent; GVE, general visceral efferent; SP, special proprioception; SSA, special somatic afferent; SVA, special visceral afferent; SVE, special visceral efferent.

Parasympathetic Ganglia of the Head

Preganglionic Parasympathetic Postganglionic Parasympathetic Nucleus of Origin Cranial Nerve of Origin Preganglionic Nerve Parasympathetic Ganglion Trigeminal Nerve Association Delivery Nerve Target: Smooth Muscle, Gland Edinger-Westphal Oculomotor III Unnamed Ciliary (GVE) Ophthalmic (V1) Short ciliary from ganglion Sphincter pupillae, ciliary body Super salivatory Facial VII Greater petrosal Pterygopalatine (GVE) Maxillary (V2) Zygomaticotemporal to lacrimal of (V1) Lacrimal gland Superior salivatory Facial VII Greater petrosal Pterygopalatine (GVE) Maxillary (V2) Greater; lesser palatine; post. sup. nasal, nasopalatine; post., middle, ant. sup. alveolars Mucous glands of nasal cavity, max, sinus, and palate Superior salivatory Facial VII Chorda tympani Submandibular (GVE) Mandibular (V3) Lingual Submandibular and sublingual glands, minor glands in floor of mouth Inferior salivatory Glossopharyngeal IX Lesser petrosal Otic (GVE) Mandibular (V3) Auriculotemporal Parotid gland GVE indicates general visceral efferent.

Cranial Nerves—Clinical Testing

Cranial Nerve Modality    Assessment Technique Perceived Dysfunction I Olfactory SVA Patient is asked to differentiate distinct odors (coffee, vanilla) with eyes covered. Test each side independently. Damage such as an ethmoid fracture may result in anosmia (loss of sense of smell). II Optic SSA Eye charts are used to assess visual acuity. Visual fields are determined by examining when patient observes an object moving from lateral to medial. Ophthalmoscope used for observing retina, optic disc, and blood vessels. Damage to the retina usually results in blindness to the affected eye. Damage beyond the optic chiasma will present partial visual losses. III Oculomotor GSE Patient is asked to follow with his or her eyes the examiner's finger as it moves up and down vertically and medially and laterally. Watch for crossing of eyes during convergence. Damage to this modality may cause paralysis of all extraocular muscles except the superior oblique and lateral rectus. This produces lateral strabismus and inability to look vertically. Also ptosis (eyelid drooping). GVE Examine patient for pupillary reflex with light shining on and off in each eye. Observe and compare contractions and dilations in affected and unaffected eyes. Damage to this modality will produce lack of pupillary reflex, dilated pupils, and lack of changes in pupil at close focus. IV Trochlear GSE Analysis of function is performed during testing of the oculomotor nerve. Damage to this nerve causes double vision and inability to rotate the eye inferolaterally. V Trigeminal Ophthalmic division (V1) GSA Test for corneal reflex with whisp of cotton. Prick forehead with pin (pain), apply warm and cold objects (temperature). Damage to this division will inhibit the corneal reflex and will reduce or inhibit sensation over the (V1) zone. Maxillary division (V2) GSA Stroke sensory zone of (V2) with eyes closed (light touch), prick with pin (pain), apply warm and cold objects (temperature). Damage to this division will reduce or inhibit sensation over the (V2) zone. Mandibular division (V3) GSA Stroke sensory zone of (V3) with eyes closed (light touch), prick with pin (pain), apply warm and cold objects (temperature). Damage to this division will reduce or inhibit sensation over the (V3) zone. Mandibular division (V3) SVE Ask patient to clench jaws, open, then move jaw side to side with resistance. Muscle strength in the temporalis and masseter should be compared from side to side by palpation. Damage in this modality may cause paralysis of the muscles of mastication, thus causing the jaw to deviate same side as the lesion. VI Abducens GSE Analysis of function is performed during testing of the oculomotor nerve. Damage to this nerve causes double vision and paralysis of the lateral rectus muscle, thus the eye remains rotated medially on the affected side. VII Facial SVA Test for taste for sweet and salty on anterior 2/3 of tongue. Damage to this modality will reduce or inhibit the sensation of taste on the anterior 2/3 of the tongue. GVE Observe tearing with pungent fumes (ammonia). Damage to this modality will reduce or inhibit the ability to secrete tears from the affected side. Mucus production in the nasal cavity and salivary gland secretions from the submandibular and sublingual glands is more difficult to evaluate. SVE Observe symmetry of face when asked to close eyes, frown, smile, whistle, raise eyebrows. Look for flacid sagging of face. Damage to this modality, such as in stroke, causes a paralysis of the muscles of facial expression, which causes the face to sag and an inability to make facial expressions on the affected side. VIII Vestibulocochlear Cochlear division SSA Test with a tuning fork by air and bone conduction. Loss of hearing by air conduction indicates a lesion or damage to the middle ear. Loss by bone conduction indicates nerve deafness. Vestibular division GSA (SP) Test walking a straight line, dizziness. Watch for rapid eye movements. Damage to the vestibular division elicits dizziness, nausea, vomiting, and uncontrolled rapid eye movement. IX Glossopharyngeal GVA Test for gag reflex and swallowing and position of the uvula during this procedure. Test touch reception on the posterior 1/3 of the tongue.b Damage to this modality would reduce or inhibit the gag reflex and produce difficulty in swallowing. It would also reduce or inhibit general sensation on the posterior 1/3 of the tongue. Sensation to the carotid body and sinus would also be lost, thereby altering blood pressure and oxygen tension in the bloodstream. SVA Test for bitter and sour taste on the posterior 1/3 of the tongue and on circumvallate papillae. Damage to this modality would reduce or inhibit the sense of taste over the posterior 1/3 of the tongue and on the circumvallate papillae. GVE Observe saliva flow from the parotid duct. Damage to this modality would reduce or inhibit saliva secretion from the parotid gland. X Vagusc SVE Have patient elevate the palate by saying “aahhhh,” swallow, and speak. Damage to this component will prevent the palate from being elevated and will make swallowing and speech difficult. XI Accessoryd SVE Have patient shrug shoulders and rotate head against resistance. Damage to this modality would reduce or inhibit the movement of the head and shoulders. XII Hypoglossal GSE Have patient protrude and retract tongue. Damage to this nerve will cause the tongue to deviate toward the affected side on protrusion, and that side will appear shrunken and wrinkled. GSA, general somatic afferent; GSE, general somatic afferent; GVE, general visceral efferent; SP, special proprioception; SSA, special somatic afferent; SVA indicates special visceral afferent; SVE, special visceral efferent. aNote that some modalities associated with certain cranial nerves are not represented in this table because some areas of the head and neck receive overlapping innervation from more than one cranial nerve, thus complicating definitive testing. For example the area about the ear/auditory meatus receives sensory innervation from several cranial nerves in addition to contributions from the cervical plexus, thereby making assessment extremely difficult. b Because there is close association and intermingling of nerve fibers of the glossopharyngeal, vagus, and accessory nerves, it is difficult to distinguish the affected nerve in clinical testing procedures. However, the gag reflex is generally considered the definitive test for glossopharyngeal nerve damage. c Although the vagus nerve serves visceral structures in the thorax and abdomen, the contents of the table are restricted to its functions in the head and neck. d This assumes that the SVE component of the accessory nerve that serves the sternocleidomastoid and trapezius muscles is from the cranial root of the accessory nerve. Remember that the SVE component of the vagus is also part of the cranial root of the accessory nerve. Therefore, damage to this root would affect both areas served by the vagus and the accessory nerves.

Cranial Nerve Examination Video...