Audiology Outline PDF

AUDIOLOGY NIXON SEE, MD – March 1, 2022 OUTLINE TUNING FORK TESTS I. Audiology Measured in hertz (cycl...

AUDIOLOGY NIXON SEE, MD – March 1, 2022 OUTLINE TUNING FORK TESTS I. Audiology Measured in hertz (cycle per second) A. Types of Hearing Problems 128, 256, 512, 1024, 2048, 4096 and 8192 Hz II. Tuning Fork Tests ○ (Red) Part of Speech frequency A. Weber Test ○ 128,256 - Called low frequency B. Rinne’s Test C. Schwabach’s Test ○ 4096,8192 - Called high frequency D. Bing’s Test III. Audiometry Dampers A. Poor Tone Audiometry B. Impedance Audiometry 1. Tympanometry Prongs/Tines 2. Acoustic Reflex C. Speech Audiometry 1. Speech Reception Thresholds 2. Speech Discrimination Body D. Auditory Brainstem Evoked Response E. Pediatric Audiometry Stem/Neck IV. Anatomy and Disorders of the facial Nerve A. Facial Nerve Heel/Base B. Degree of Injury C. Neuropathology and Spontaneous Recovery of Facial Nerve Dampers prevent production of overtones when the tuning Injury fork is hit too much D. Diseases of the Facial Nerve The fork is held close to the ear, and the patient is asked to References: report when the sound is no longer audible. Boies Fundamentals of Otolaryngology Fork is placed next to the examiner’s ear and the interval Lecture between that time and the time at which the sound is no longer Notes audible to the examiner is measured. WEBER TEST AUDIOLOGY Test of lateralization Science of hearing Extends the familiar experience of hearing one’s own voice Is a subspecialty of otolaryngology that deals with the louder when an ear is blocked evaluation of hearing and rehab of individuals with The stem of the vibrating fork is held to the midline of the communication problems forehead, and the patient is asked to report whether the sound is heard in the left, right, or both ears REASONS TO EVALUATE Most useful in instances of unilateral impairment Medical diagnosis of locations and types of disease Result: if tone lateralize to: Assess impact of hearing problem TYPES OF EVALUATION ○ Better ear – sensory loss ○ Poor ear – conductive loss Tuning fork – can test for: ○ Conductive hearing impairment RINNE’S TEST ○ Sensory hearing impairment Compares bone against air conduction ○ EXCEPT FOR mix type The hilt of the vibrating fork is held against the patient’s Pure tone audiometry mastoid (bone conduction) until sound is no longer heard; the Speech audiometry tines are then placed close to the same ear (air conduction) Special tests: If the result is: ○ Impedance ○ (+): AC > BC Normal or Sensory hearing loss ○ BERA ○ (-): BC > AC Conductive hearing loss TYPES OF HEARING PROBLEMS Conductive type hearing loss SCHWABACH’S TEST ○ Problem lies in the external and middle ear Compares patient’s bone with the examiner (assuming the Sensorineural type Hearing Loss examiner is normal) ○ Problem lies in the inner ear and the whole auditory The stem of the vibrating fork is held against the mastoid, the pathway patient reports when the sound becomes inaudible ○ Auditory pathway: (COLIMA) Cochlea Then, the examiner applies the fork stem to his own mastoid Superior Olives and measures the time (in seconds) the examiner can still Lateral lemniscus perceive the sound. Result Inferior colliculus ○ Equal with examiner: Normal Medial geniculate body ○ Prolonged: Conductive Auditory cortex ○ Diminished: Sensory Mixed type ❗️USE AT YOUR OWN RISK ❗️ page 1 of 8  AUDIOLOGY BING’S TEST ○ Most likely occurs through the skull via bone “Occlusion test” conduction even though the signal is presented Fork is heard louder as the normal ear is occluded through air conduction receivers If the auditory meatus is alternately occluded and left open, as the vibrating fork is held to the mastoid, an increase and MASKING decrease in loudness will be perceived by the normal ear Obscuring one sound by another sound (hissing sound) (positive Bing) Elevation of one signal produced by introduction of a 2nd Result sound ○ Positive: increasing and decreasing hearing ; Narrow band noise is the most efficient masker of pure tones normal or sensory loss ○ Consists of energy in a limited band of frequencies ○ Negative: no change in variation or conductive loss whose center frequency is the same as the pure tone signal being tested AUDIOMETRY POOR TONE AUDIOMETRY AUDIOMETER An electronic device w/c produces sound free of noise (sound energy or overtones) ,hence “pure” tones Parts: ○ Attenuator: variation of sound intensity; measured in decibels (typically in 5 dB steps) ○ Frequency oscillator: changes the frequency pitch; measured in hertz THRESHOLD ○ Transducers: earphones, headphones and Lowest intensity/loudness (dB) that patient can hear in vibrators to convert electrical to acoustic energy different frequencies (Hertz) Headphone - for air conduction testing ○ Air Conduction Testing Bone vibrator - for bone conduction ○ Bone Conduction testing testing Intensity: loudness, sound intensity (db) Frequency: audible sound cycles per second (Hertz) PROCEDURE Hughson Westlake Technique Also known as 5 up 10 down technique INTERAURAL ATTENUATION Most universally accepted Is the reduction of a signal’s intensity as it is transmitted from one ear to the other 1. Test better ear always at 1KHz, 2KHz, 4KHz, 8KHz, Estimates: 500Hz, 250Hz - Air Conduction ○ In Bone conduction testing: Negligible or 0 dB 2. Starting at 0 dB level and ascend by 10 dB increment ○ In Air conduction testing: 45 db 3. Follow the 5 up 10 down rule 4. Successive ascent of 5 dB increment until a typical response is obtained 5. Enter appropriate symbol 6. Proceed to the next frequency 15-20dB below the previous threshold 7. Same procedure done with Bone testing In air conduction, if you stimulate the right ear(tested ear) with 50 dB, 5 dB can be heard on the left ear(non-tested ear), the patient will respond but is false-positive For bone conduction testing, since we are vibrating the right mastoid, the whole skull will vibrate as well as the non-tested left ear thus, the patient will respond to the test, also false- positive Cross Hearing ○ Patient respond to the test signal on the non-tested ear 8. ❗️USE AT YOUR OWN RISK❗️ page 2 of 8  AUDIOLOGY Use Red pen for Right ear, Blue pen for Left ear MIXED TYPE HEARING LOSS: Both AC and BC thresholds are reduced but BC thresholds are still better than AC by 10 dB or more ○ Cannot diagnose by tuning fork test Audiometric Keys Normal: 0 – 20 dB (WHO:0-25 dB) Speech frequency: 512 Hz, 1024 Hz, 2048 Hz INTERPRETATION Normal: When bone conduction and air conduction thresholds are between 0-20 dB DEGREE OF HEARING LOSS ○ Quantify or qualify the degree of hearing impairment. 25-45 dB = mild hearing impairment 45-60 dB = moderate 60-70 dB = severe ○ Bone conduction threshold is joined by a dotted line 70-100 dB = profound and Air conduction threshold is joined by a solid line Diagnosis for example mild conductive type , moderate sensorineural type or severe, profound, severe to profound mixed type hearing loss. CONDUCTIVE TYPE HEARING LOSS: BC thresholds are normal and better than AC by more than 10 dB ○ SENSORINEURAL HEARING LOSS: Both BC and AC are the same and neither is normal but without a gap of more than 10 dB ❗️USE AT YOUR OWN RISK❗️ page 3 of 8  AUDIOLOGY IMPEDANCE AUDIOMETRY TYMPANOGRAM Tympanometry Is a graphic representation of relative compliance in the Acoustic reflex tympano-ossicular system while air pressure changes are produced in the external meatus. RA 9709 Universal Newborn Hearing and Intervention Act of 2009 By Philippine law, it is obligatory to test all newborns for TYPE A: NORMAL hearing screening 24 hours after birth. ○ Maximum If the patient fails on this test, it can be repeated after 1 month compliance at an air ○ OAE - Otoacoustic emission test pressure difference ○ AABR - Automated Auditory Brainstem Response of 0 mm H2O Audiometry ○ Graph peaks at 0 CONFIRMATORY TEST ABR - Auditory Brainstem Evoked Response ASSR - Auditory Steady State Response Audiometry TYPE Ad ○ Very highly compliance at ambient pressure ○ Seen in ossicular discontinuity or monomeric tympanic membrane. ○ Has the same IMPEDANCE AUDIOMETRY pressure both external and middle ear, but the The external ear is totally sealed off. tympanic membrane will move very loosely at zero No sound, pressure or stimulus can get in without being pressure, because there's no limitation or restriction on measured, and no sound or echoes can come out without the movement by the ossicles being measured as well. TYMPANOMETRY Is an indirect measure of the compliance (mobility) of the TYPE As tympanic membrane under conditions of (+), (-) or normal ○ Very low compliance at ambient pressure pressures ○ Seen in ossicular fixation because of recurrent middle ear infection. ○ Movement of the tympanic membrane is seen on zero pressure but is now limited or restricted. ○ If there is fluid, the tympanic membrane is bulging or under pressure, it will not be able to move either on positive or negative pressure. The tympanic membrane will be able to move freely if the pressure in the external ear is the same as the pressure in the middle ear because they are both open into the atmosphere. PURPOSE: ○ TM mobility ○ Middle ear pressure ○ TM perforation TYPE B - FLAT / DOME SHAPED ○ Patency of the Eustachian tube ○ Little or no change in middle ear compliance ○ Impacted cerumen middle ear fluid TM perforation PROCEDURE: ○ Acoustic energy (45 dB SPL) is introduced into the ear. ○ Some are absorbed, others are reflected back and measured by another channel ❗️USE AT YOUR OWN RISK❗️ page 4 of 8  AUDIOLOGY INTERPRETATION PRESENT ○ Normal hearing ABSENT ○ 8th cranial nerve lesion ○ Unilateral conductive ○ Bilateral conductive ○ Disarticulation ○ Facial paralysis ○ Stapedial fixation ○ Retrocochlear lesion ○ Congenital absence of the stapedius muscle ○ Surgical removal of stapes TYPE C SPEECH AUDIOMETRY ○ Maximum compliance at negative air pressure Ability to hear and understand speech greater than 100 mm H20 Speech is the stimulus itself ○ Poor ET function ○ Retracted eardrum, the tympanic membrane is adherent on the medial wall of the middle ear. SPEECH RECEPTION THRESHOLDS ○ Negative pressure should be applied on the AKA recognition threshold or speech threshold external ear to equalize the negative pressure in the It is the faintest presentation level in dB at which a patient can middle ear for theTM to go back to its normal identify 50% of test words correctly position. Utilizes spondee (2 syllable, equal stress) words Countercheck of pure tone audiometry Thresholds average of 500 Hz, 1000 Hz, 2000 Hz SPEECH DISCRIMINATION Speech Intelligibility Test ○ Number of lists developed are phonetically balanced. Also for vocabulary familiarity. ○ Words are presented 40 dB louder than the SRT patient is instructed to repeat each words ○ Percentage of response is recorded INTERPRETATION This can be the basis to choose which patient will benefit with the usage of hearing aids If the discrimination is more than 80% then they are good ACOUSTIC REFLEX candidates to wear hearing aids. Contraction of stapedius muscle in response to stimulation of 90-100% NORMAL sound of sufficient intensity 75-90% SLIGHT DIFFICULTY Connects the auditory nerve to both stapedial motor neurons. 60-75% MODERATE DIFFICULTY 70-100 dB stapedius muscle contract bilaterally and reflexibly 50-60% POOR DISCRIMINATION Very important protective reflex DIFFICULTY IN CONVERSATION ○ If a very loud sound is forced into the external ear, below 50% VERY POOR DISCRIMINATION pressure will be transmitted to the TM or eardrum which will over stimulate the ossicles, malleus, HEARING AIDS incus and stapes and force it inside the oval Depending on the types and the value, the cost will window. It could rupture the oval window that will incrementally increase. render the patient very dizzy for a long time and TYPES result to total deafness for life CIC - completely in the ear (cosmetics) ○ Because of acoustic/stapedial reflex this rarely ITE - in the ear (compact) happens. When the stapedius muscle contracts, it ITC - in the canal (small) limits the movement of the stapes inwards towards the oval window. BTE - behind the ear (compact) The smaller it is, the more expensive it will be. Every feature 1. AFFERENT LIMB you add on the hearing aid will entail another added expense Auditory fibers from the cochlea on the price of the hearing aid. 2. REFLEX CENTER Caudal portion of the Pons AUDITORY BRAINSTEM EVOKED RESPONSE 3. EFFERENT LIMB Represent electrical response of CN VIII and some portions Facial nerve of the brain to auditory stimulus after being sensed by the It is reflexive and bilateral, taking advantage to do acoustic inner ear reflex contralaterally or ipsilaterally. 80 dB above thresholds click stimulus at fixed repetitions e.g. 11/sec or 33/sec until 2000 click response have been average ❗️USE AT YOUR OWN RISK❗️ page 5 of 8  AUDIOLOGY Electrodes on mastoid vs. forehead EEG pattern The cerebral cortical tracts also innervate the contralateral Series of waves ( I-VIII) are produced I and II are from the portion of the remainder of the face. cochlea The motor nucleus innervates only the ipsilateral facial nerve. Results: latency of each wave and interwave As the nerve leaves the brain stem, a branch of the eighth nerve referred to as the nervus intermedius separates and joins the seventh nerve as it enters the internal auditory canal. The nerve turns anteriorly and enters the geniculate ganglion. Wave I – 1st order It is here, near the oval window, that the nerve can become neuron exposed and may be palpable in the middle ear. II – cochlea The nerve descends from the genus vertically and gives a III - superior olives branch to the stapedius muscle. Below this level, a second IV – V- inferior branch emerges and backtracks through the ear as the chorda colliculus tympani nerve. The chorda carries fibers of touch, pain, temperature, and taste to the anterior two thirds of the tongue. It also controls salivation from the submandibular glands. The major portion of the facial nerve carries motor fibers that exit from the stylomastoid foramen just dehiscent. medial to CLINICAL USES the mastoid process. The nerve subsequently turns anteriorly and divides into five Cerebellopontine angle tumors – 95% -very reliable test major branches—the temporal, zygomatic, buccal, Menniere’s disease and non-Meniere’s dizziness mandibular, and cervical. used as mandatory hearing test for Hearing threshold in infants FACIAL NERVE may have value in evaluating auditory processing disorders Five main functions: ○ Lacrimation PEDIATRIC AUDIOMETRY ○ Salivation Behavioral Audiometry ○ Impedance regulation of sound ○ Newborn to 24mos of age ○ Pain, touch and temperature ○ Difficult to handle and inconsistent ○ Taste ○ replaced by BERA Play audiometry -2-4 years old Speech audiometry Objective audiometry ○ Impedance Audiometry ○ BERA ○ Otoacoustic Emission test ANATOMY AND DISORDERS OF THE FACIAL NERVE This illustrates what facial nerve should be attended by the neurologist and which facial nerve paralysis needs to be treated by an otolaryngologist. Differentiation between Upper Motor Neuron Paralysis and Lower Motor Neuron Paralysis. ○ For all cranial nerves, the level of decussation of its fibers is at the level of the nucleus. ○ The nucleus of the facial nerve is in the pons. ○ Fibers of the facial nerve innervate the opposite upper and the opposite lower face. But it also receives an ipsilateral innervation to the lower face. ○ If the patient has UMN paralysis, it will block both innervation to the contralateral upper and contralateral lower face. But since it will have an ipsilateral innervation to the upper face, the upper The 7th cranial nerve begins at the brainstem and follows a face will remain intact, then it will be purely a course through the temporal bone, ending in the muscles of neurological case. the face. ○ If the patient has LMN, blocking both upper and There are at least 5 major branches. While the 7th cranial lower contralateral case, it will receive the same nerve carries innervation to facial motion, it also provides innervation on the ipsilateral upper face but since it lacrimation, salivation, impedance regulation of the middle will also be blocked, then the patient has a total ear, and the senses of pain, touch, temperature, and taste. paralysis on the opposite side. The 7th nerve nucleus is in the region of the pons. Here, it receives information from the precentral gyrus of the motor DIAGNOSTIC PROCEDURES cortex, which innervates the ipsilateral and contralateral Audiologic Evaluation forehead. ○ Pure Tone Audiometry ○ BERA ❗️USE AT YOUR OWN RISK❗️ page 6 of 8  AUDIOLOGY ○ Tympanometry NEUROPATHOLOGY AND SPONTANEOUS RECOVERY OF ○ Stapedial Reflex FACIAL NERVE INJURY ○ The function of the eighth cranial nerve can be evaluated using auditory brainstem evoked DEGREE PATHOLOGY RECOVERY response (ABR) tests. This test is most helpful in detecting pathology in the internal auditory canal. 1st Compression: damming of 1 – 4 weeks axoplasm no morphologic Schirmer’s Test changes ○ difference of 25% is Significant ○ tearing function of the eye can be evaluated 2nd compression persist with 1 – 2 months ○ These strips are placed over the lower lid into the increased intraneural conjunctival sac on both sides. After three minutes, pressure, loss of axon the length of the strip that is moist is compared to the opposite side. 3rd intraneural pressure 2 – 4 months ○ The side of less tearing is interpreted to represent increases; loss of myelin tubes greater superficial petrosal nerve activity due to loss of action in the parasympathetic nerve of Wrisberg. 4th above + disruption of 4 – 18 months perineurium partial Taste Sensation Stimulation transection ○ Measurement of taste is a reliable indicator of the interruption of the function of the chorda tympani 5th above + disruption of Never nerve. epineurium complete ○ Sweet and Sour – Tip transection ○ Salt – Lateral ○ Bitter – Base DISEASES OF THE FACIAL NERVE Salivation CONGENITAL ○ Cannulation of the Wharton’s Duct Moebius Syndrome – Fibrotic Facial nerve ○ 25% difference is significant ○ facial nerve forms but it is a fibrotic tract ○ can be performed by cannulating the ○ And while muscle development may be present in submandibular glands some cases, it usually rapidly degenerates to Nerve Function Tests: fibrosis ○ EMG – Electromyography Traumatic Birth normal ○ facial nerve paralysis is a result of childbirth trauma fibrillation - Fibrillation potentials are a ○ During the process of childbirth, fractures of the positive sign showing recovery of some temporal bone can occur. The use of forceps has fibers. These potentials are not seen been indicated as a potential cause of many of before 21 days. these lesions. denervation bizarre pattern INFECTIONS ○ ENog – Electoneurography can be done earlier than 3 weeks Herpes zoster Oticus persistence of paralysis 90% compare to Middle ear Infections the normal side in 10 days indicate poor prognosis TRAUMA ○ Maximal Stimulation Test - probe is pressed against Temporal Bone Fracture the face in the area of the facial nerve. It is quite ○ Longitudinal– parallel to the temporal bone painful to the patient. delayed complete paralysis full recovery DEGREE OF INJURY complete paralysis ○ Transverse - perpendicular fracture 25% full recovery 1st Degree Neuropraxia - partial disruption of axonal activity 2nd Degree Axonotmesis - wallerian degeneration ○ While longitudinal fractures are much more 3rd Degree Neurotmesis - aberrant regeneration can common, transverse fractures injure the nerve occur many times more frequently. 4th Degree Perineural disruption – intraneural scarring NEOPLASM INVOLVING THE FACIAL NERVE 5th Degree Complete Transection – no regeneration Cerebellopontine Angle Tumors Acoustic Neuroma We classify them according to its prognosis. Meningioma Middle Ear Lesions: ○ Glomus jugulare ○ Histiocytosis - formerly a benign tumor ❗️USE AT YOUR OWN RISK❗️ page 7 of 8  AUDIOLOGY ○ Rhabdomyosarcoma - aggressive tumor ○ Squamous cell carcinoma - aggressive tumor IDIOPATHIC CAUSE Bell’s Palsy ○ Most common cause of unilateral facial paralysis ○ Unilateral weakness or paralysis of the face with no readily identifiable cause and virtually always has some recovery of function within six months ○ Onset is acute, with a progressive course reaching the stage of greatest muscle weakness within three weeks ○ Treatment Corneal Protection Steroids Fascial Slings Nerve Grafting: Spinal Accessory nerve & Hypoglossal Nerve Muscle Slings: Temporalis Muscle & Masseter Muscle - ❗️USE AT YOUR OWN RISK❗️ page 8 of 8