CP2001 Neurological Examination Cranial Nerves Clinical Skills Laboratory 2023.pdf

Examination of the Neurological System Cranial Nerves Clinical Skills Laboratory CP2001 1 Learning Outcomes At the end of the teaching and learning activities on this topic the student should be able to: • Demonstrate a professional approach to physical examination of the patient • Consider what...

Examination of the Neurological System Cranial Nerves Clinical Skills Laboratory CP2001 1 Learning Outcomes At the end of the teaching and learning activities on this topic the student should be able to: • Demonstrate a professional approach to physical examination of the patient • Consider what has been presented so far in the neuroscience module regarding the cranial nerves and how clinical examination relates to this new knowledge • Recognise normal and abnormal neurological signs pertaining to the cranial nerves • Differentiate clinically between an upper and lower motor neuron lesion of the 7th cranial nerve CP2001 2 Preparing for this Session 1. Look at Learning Outcomes on CANVAS 2. Read information (PDFs) on examination of cranial nerves 3. Watch video demos of Systematic Examination of the Cranial Nerves 4. Read PDF on Selected Cranial Nerve Palsies 5. Prepare for supervised Practice of the Examination of the Cranial Nerves (CN I-VIII, CNXI with mask on, 2 m away from patient) 6. Prepare to explain to tutor how you would examine CN IX, X, XII CP2001 3 Introduction The brainstem can be divided into three levels, the midbrain, the pons and the medulla. The cranial nerves for each of these are: 2 for the midbrain (CN 3 & 4), 4 for the pons (CN 5-8), and 4 for the medulla (CN 9-12). It is important to remember that cranial nerves never cross and clinical findings are always on the same side as the cranial nerve involved. Cranial nerve findings when combined with long tract findings (corticospinal and somatosensory) are powerful for localizing lesions in the brainstem. CP2001 4 Cranial Nerve 1 Olfaction is the only sensory modality with direct access to cerebral cortex without going through the thalamus. The olfactory tracts project mainly to the uncus of the temporal lobes. Cranial Nerve 2 This cranial nerve has important localizing value because of its "x" axis course from the eye to the occipital cortex. The pattern of a visual field deficit indicates whether an anatomical lesion is pre- or post-chiasmal, optic tract, optic radiation or primary visual cortex. CP2001 5 CP2001 6 Cranial Nerve 3 and 4 These cranial nerves give us a view of the midbrain. The 3rd nerve in particular can give important anatomical localization because it exits the midbrain just medial to the cerebral peduncle. The 3rd nerve controls eye adduction (medial rectus), elevation (superior rectus), depression (inferior rectus), elevation of the eyelid (levator palpebrae superioris), and parasympathetics for the pupil. The 4th CN supplies the superior oblique muscle, which is important to looking down and in (towards the midline). Cranial Nerve 6 This cranial nerve innervates the lateral rectus for eye abduction. Remember that cranial nerves 3, 4 and 6 must work in concert for conjugate eye movements; if they don't then diplopia (double vision) results. The medial longitudinal fasciculus (MLF) connects the 6th nerve nucleus to the 3rd nerve nucleus for conjugate movement. CP2001 7 Major Oculomotor Gaze Systems Eye movements are controlled by 4 major oculomotor gaze systems, which are tested for on the neurological exam. They are briefly outlined here: Saccadic (frontal gaze center to PPRF (paramedian pontine reticular formation) for rapid eye movements to bring new objects being viewed on to the fovea. Smooth Pursuit (parietal-occipital gaze center via cerebellar and vestibular pathways) for eye movements to keep a moving image centered on the fovea. Vestibulo-ocular (vestibular input) keeps image steady on fovea during head movements. Vergence (optic pathways to oculomotor nuclei) to keep image on fovea predominantly when the viewed object is moved near (near triad- convergence, accommodation and pupillary constriction) CP2001 8 Cranial Nerve 5 The entry zone for this cranial nerve is at the mid pons with the motor and main sensory (discriminatory touch) nucleus located at the same level. The axons for the descending tract of the 5th nerve (pain and temperature) descend to the level of the upper cervical spinal cord before they synapse with neurons of the nucleus of the descending tract of the 5th nerve. Second order neurons then cross over and ascend to the VPM of the thalamus CP2001 9 Cranial Nerve 7 This cranial nerve has a motor component for muscles of facial expression (and, don't forget, the strapedius muscle which is important for the acoustic reflex), parasympathetics for tear and salivary glands, sensory for taste (anterior two-thirds of the tongue). Central (upper motor neuron-UMN) versus Peripheral (lower motor neuron-LMN) 7th nerve weaknesswith a peripheral 7th nerve lesion all of the muscles ipsilateral to the affected nerve will be weak whereas with a "central 7th ", only the muscles of the lower half of the face contralateral to the lesion will be weak because the portion of the 7th nerve nucleus that supplies the upper face receives bilateral corticobulbar (UMN) input. CP2001 10 Cranial Nerve 8 This nerve is a sensory nerve with two divisions- acoustic and vestibular. The acoustic division is tested by checking auditory acuity and with the Rinne and Weber tests. The vestibular division of this nerve is important for balance. Clinically it be tested with the oculocephalic reflex (Doll's eye maneuver) and oculovestibular reflex (ice water calorics). Cranial nerves 9 and 10 These two nerves are clinically lumped together. Motor wise, they innervate pharyngeal and laryngeal muscles. Their sensory component is sensation for the pharynx and taste for the posterior onethird of the tongue. CP2001 11 Cranial Nerve 11 This nerve is a motor nerve for the sternocleidomastoid and trapezius muscles. The UMN control for the sternocleidomastoid (SCM) is an exception to the rule of the ipsilateral cerebral hemisphere controls the movement of the contralateral side of the body. Because of the crossing then recrossing of the corticobulbar tracts at the high cervical level, the ipsilateral cerebral hemisphere controls the ipsilateral SCM muscle. This makes sense as far as coordinating head movement with body movement if you think about it (remember that the SCM turns the head to the opposite side). So if you want to work with the left side of your body you would want to turn your head to the left so the right SCM would be activated Cranial Nerve 12 The last of the cranial nerves, supplies motor innervation for the tongue CP2001 12 Traps A 6th nerve palsy may be a "false localizing sign". The reason for this is that it has the longest intracranial route of the cranial nerves, therefore it is the most susceptible to pressure that can occur with any cause of increased intracranial pressure. Pearls Rules of Diplopia Diplopia is maximum in the direction of action of the paretic muscle The most peripherally seen image is the false image and comes from the eye with the paretic muscle. The diplopia is horizontal if the medial or lateral recti are involved and vertical if the elevator or depressor muscles are involved. CP2001 13 Abnormal clinical findings CP2001 14 http://cim.ucdavis.edu/EyeRelease/Interface/TopFrame.htm CP2001 15 Cranial Nerve 1- Olfaction This patient has difficulty identifying the smells presented. Loss of smell is anosmia. The most common cause is a cold (as in this patient) or nasal allergies. Other causes include trauma or a meningioma effecting the olfactory tracts. Anosmia is also seen in Kallman syndrome because of agenesis of the olfactory bulbs. CP2001 16 Cranial Nerve 2- Visual acuity This patientâs visual acuity is being tested with a Rosenbaum chart. First the left eye is tested, then the right eye. He is tested with his glasses on so this represents corrected visual acuity. He has 20/70 vision in the left eye and 20/40 in the right. His decreased visual acuity is from optic nerve damage. CP2001 17 Cranial Nerves 2 & 3- Pupillary Light Reflex The swinging flashlight test is used to show a relative afferent pupillary defect or a Marcus Gunn pupil of the left eye. The left eye has perceived less light stimulus (a defect in the sensory or afferent pathway) then the opposite eye so the pupil dilates with the same light stimulus that caused constriction when the normal eye was stimulated. CP2001 18 Convergence Light-near dissociation occurs when the pupils don't react to light but constrict with convergence as part of the near reflex. This is what happens in the Argyll-Robertson pupil (usually seen with neurosyphilis) CP2001 19 Cranial Nerve II- Visual fields The patient's visual fields are being tested with gross confrontation. A right sided visual field deficit for both eyes is shown. This is a right hemianopia from a lesion behind the optic chiasm involving the left optic tract, radiation or striate cortex. CP2001 20 Cranial Nerves 3, 4 & 6- Inspection & Ocular Alignment This patient with ocular myasthenia gravis has bilateral ptosis, left greater than right. There is also ocular misalignment because of weakness of the eye muscles especially of the left eye. Note the reflection of the light source doesn't fall on the same location of each eyeball. CP2001 21 Cranial Nerves 3, 4 & 6- Versions • The first patient shown has incomplete abduction of her left eye from a 6th nerve palsy. • The second patient has a left 3rd nerve palsy resulting in ptosis, dilated pupil, limited adduction, elevation, and depression of the left eye. CP2001 22 Optokinetic Nystagmus This patient has poor optokinetic nystagmus when the tape is moved to the right or left. The patient lacks the input from the parietal-occipital gaze centers to initiate smooth pursuit movements therefore her visual tracking of the objects on the tape is inconsistent and erratic. Patients who have a lesion of the parietal-occipital gaze center will have absent optokinetic nystagmus when the tape is moved toward the side of the lesion. CP2001 23 Cranial Nerve 5- Sensory There is a sensory deficit for both light touch and pain on the left side of the face for all divisions of the 5th nerve. Note that the deficit is first recognized just to the left of the midline and not exactly at the midline. CP2001 24 Cranial Nerve 5- Motor • The first patient shown has weakness of the pterygoids and the jaw deviates towards the side of the weakness. • The second patient shown has a positive jaw jerk which indicates an upper motor lesion affecting the 5th cranial nerve. CP2001 25 Seventh Nerve Lower motor neuron ‘make a scary face’ CP2001 26 Seventh Nerve Lower motor neuron ‘close your eyes tight’ CP2001 27 Seventh Nerve upper motor neuron ‘Look up’ (wrinkle your forehead) CP2001 28 Seventh Nerve upper motor neuron ‘puff your cheeks full of air’ CP2001 29 Cranial Nerve 7- Sensory, Taste The patient has difficulty correctly identifying taste on the right side of the tongue indicating a lesion of the sensory limb of the 7th nerve. CP2001 30 Cranial Nerve 8- Auditory Acuity, Weber & Rinne Tests This patient has decreased hearing acuity of the right ear. The Weber test lateralizes to the right ear and bone conduction is greater than air conduction on the right. He has a conductive hearing loss. CP2001 31 Cranial Nerve 9 & 10- Motor When the patient says "ah" there is excessive nasal air escape. The palate elevates more on the left side and the uvula deviates toward the left side because the right side is weak. This patient has a deficit of the right 9th & 10th cranial nerves. CP2001 32 Cranial Nerve 9 & 10- Sensory and Motor: Gag Reflex Using a tongue blade, the left side of the patient's palate is touched which results in a gag reflex with the left side of the palate elevating more then the right and the uvula deviating to the left consistent with a right CN 9 & 10 deficit. CP2001 33 Cranial Nerve 11- Motor When the patient contracts the muscles of the neck the left sternocleidomastoid muscle is easily seen but the right is absent. Looking at the back of the patient, the left trapezius muscle is outlined and present but the right is atrophic and hard to identify. These findings indicate a lesion of the right 11th cranial nerve. CP2001 34 Cranial Nerve 12- Motor Notice the atrophy and fasciculation of the right side of this patient's tongue. The tongue deviates to the right as well because of weakness of the right intrinsic tongue muscles. These findings are present because of a lesion of the right 12th cranial nerve. CP2001 35 Acknowledgements Material used in this teaching session gratefully received from the following 1. Movies drawn from the NeuroLogic Exam and PediNeuroLogic Exam websites are used by permission of I. Paul D. Larsen, M.D., University of Nebraska Medical Center II. Suzanne S. Stensaas, Ph.D., University of Utah School of Medicine. 2. Additional materials were drawn from resources provided by I. Alejandro Stern, Stern Foundation, Buenos Aires, Argentina; II. Kathleen Digre, M.D., University of Utah; III. Daniel Jacobson, M.D., Marshfield Clinic, Wisconsin. 3. Neurological Teaching Videos http://www.ntv.wright.edu © 2004 Wright State University CP2001 36