Auditory System Lamon Willis

Anatomy

Anatomy External ear tragus auricle or pinna The ears are sensory organs comprising the auditory system. The ear has three regions, external ear, middle ear and inner ear. All three regions are involved in hearing, only the inner ear is concerned with balance. You can see most of the external ear (external acoustic meatus, auricle or pinna); it serves to protect the eardrum and middle ear. It is also a sound collecting system funneling sound waves to travel through the ear canal to the tympanic membrane (or eardrum). It is composed of cartilage and loose fitting skin. The tragus is a small projection just in front of the ear canal. The lobule of the ear hangs inferiorly, piercing this structure is popular. The auricle opens into the external auditory canal providing a passageway for sound waves to enter the ear. The external auditory canal courses through the temporal bone of the skull approximately one inch in length and a half inch in diameter. This canal extends to the tympanic membrane or eardrum which separates the external ear from the middle ear. Tiny hairs and modified sweat glands line the canal; the glands secrete cerumen, or earwax preventing dust and other foreign objects from entering the ear. Too much earwax can impede sound transmission and hearing. The middle ear begins at the tympanic membrane. It is an air filled chamber in the temporal bone. Besides the tympanic membrane, the middle ear contains three tiny bones and the eustachian tube. The tympanic membrane is made of connective tissue with rich blood vessels and nerves. It is connected to the throat and nasopharynx via the eustachian tube. Connection of the ear and throat make the ears susceptible to infections like otitis media due to bacteria traveling up the Eustachian tube to the ear. The tympanic membrane vibrates in response to sound waves converted into mechanical vibrations. Vibrations are passed through the middle to the inner ear by the three tiny middle ear bones. Middle ear bones, or ossicles, are the smallest bones in the body and are called: malleus (hammer); incus (anvil); and stapes (stirrup) named for their shape. Vibration from the tympanic membrane is transferred to the ossicles and then to the oval window, a membrane separating the middle ear from the inner ear. The auditory or eustachian tube functions to equalize the pressure on both sides of the tympanic membrane, this allows air to pass from the pharynx into the middle ear. This tube is normally collapsed, with swallowing or chewing the tube opens allowing air to move as needed.

Anatomy Middle ear Oval window Tympanic membrane Ossicles – malleus, incus, stapes Eustachian tube Oval window The ears are sensory organs comprising the auditory system. The ear has three regions, external ear, middle ear and inner ear. All three regions are involved in hearing, only the inner ear is concerned with balance. You can see most of the external ear (external acoustic meatus, auricle or pinna); it serves to protect the eardrum and middle ear. It is also a sound collecting system funneling sound waves to travel through the ear canal to the tympanic membrane (or eardrum). It is composed of cartilage and loose fitting skin. The tragus is a small projection just in front of the ear canal. The lobule of the ear hangs inferiorly, piercing this structure is popular. The auricle opens into the external auditory canal providing a passageway for sound waves to enter the ear. The external auditory canal courses through the temporal bone of the skull approximately one inch in length and a half inch in diameter. This canal extends to the tympanic membrane or eardrum which separates the external ear from the middle ear. Tiny hairs and modified sweat glands line the canal; the glands secrete cerumen, or earwax preventing dust and other foreign objects from entering the ear. Too much earwax can impede sound transmission and hearing. The middle ear begins at the tympanic membrane. It is an air filled chamber in the temporal bone. Besides the tympanic membrane, the middle ear contains three tiny bones and the eustachian tube. The tympanic membrane is made of connective tissue with rich blood vessels and nerves. It is connected to the throat and nasopharynx via the eustachian tube. Connection of the ear and throat make the ears susceptible to infections like otitis media due to bacteria traveling up the Eustachian tube to the ear. The tympanic membrane vibrates in response to sound waves converted into mechanical vibrations. Vibrations are passed through the middle to the inner ear by the three tiny middle ear bones. Middle ear bones, or ossicles, are the smallest bones in the body and are called: malleus (hammer); incus (anvil); and stapes (stirrup) named for their shape. Vibration from the tympanic membrane is transferred to the ossicles and then to the oval window, a membrane separating the middle ear from the inner ear. The auditory or eustachian tube functions to equalize the pressure on both sides of the tympanic membrane, this allows air to pass from the pharynx into the middle ear. This tube is normally collapsed, with swallowing or chewing the tube opens allowing air to move as needed.

Anatomy Inner ear Labyrinth Membranous labyrinth – hair cells Vibrations into nerve impulse Cochlea, Vestibule, Semicircular canal Balance – utricle, saccule Oval window, round window The inner ear is an intricate maze of fluid-filled tubes running through the temporal bone of the skull. This bony labyrinth is filled with fluid called perilymph. Inside this bony labyrinth is a second set of tubes called the membranous labyrinth filled with endolymph. This membranous labyrinth contains the actual hearing cells, or hair cells of the Organ of Corti. Movement of these hair cells converts the vibrations into a nerve impulse. The bony labyrinth has three parts; the front portion is the snail-shaped cochlea, the rear portion the semicircular canal; interconnecting the cochlea and the semicircular canal is the vestibule. The vestibule contains sense organs responsible for balance called the utricle and the saccule. The inner ear has two membrane covered outlets into the air filled middle ear, the oval window and the round window. The stapes in the middle ear vibrates on the oval window affecting fluid in the inner ear transmitting that vibration. The round window serves as the pressure valve bulging outward as fluid pressure rises in the inner ear. Nerve impulses from the inner ear travel along the cochlear nerve (8th cranial nerve) for hearing and to the vestibular nerve (8th cranial nerve) for equilibrium. The semicircular canals and vestibule function to sense movement as an acceleration or deceleration with position changes.

CPT Procedures Removal foreign body from external auditory canal (69200-69205) - both ears (69210)

CPT Procedures Middle Ear (69400-69799) Tympanostomy (69433-69436) Mastoidectomy; complete (69502) modified radical (69505) radical (69511) Tympanoplasty (69635-69646) Middle Ear (69400-69799) is a larger section of codes. It is grouped by Introduction, Incision, Excision, Repair and Other Procedures. Tympanostomy (69433-69436) is demonstrated very well with an illustration showing the tubes. Tympanostomy is synonymous with myringotomy which is creating a passageway through the tympanic membrane. Discussed earlier, placement of tubes in ears has become controversial. Previously children with recurrent middle early infections received “tubes” to help drain the ears and prevent recurrent infections. For many, it not only prevented repeated visits to the E.R. and pediatrician offices, it saved their hearing. Repeated infections cause scarring and damage to delicate structures in the middle ear impacting hearing. Mastoidectomy; complete (69502) is removal of the mastoid bone. Malignancy or extremely serious infection necessitate this procedure. Listed next are more extreme procedures, modified radical (69505) and radical (69511). Repair of the tympanic membrane, tympanoplasty (69635-69646) codes contain notes and instructions to be reviewed carefully. CPT® contains a good illustration of this in the Repair section of the middle ear.

CPT Procedures Inner Ear (69801-69949) Labyrinthectomy (69905) Temporal Bone, Middle Fossa Approach (69950- 69979) Microsurgery Inner Ear (69801-69949) is grouped by Incision and/or Destruction, Excision, Introduction and Other Procedures. Few codes are listed here. These are extremely small structures. An excision code (69905) labyrinthectomy reports removal of the labyrinth in the middle ear. This is a very small, well protected structure, very difficult to get to.   Temporal Bone, Middle Fossa Approach (69950-69979) contains five codes. Decompression usually refers to a nerve that is under pressure. Decompression procedures are performed to relive the pressure. At the end of this section is a long discussion in green writing (new this year) regarding the Operating Microscope. Microsurgery is of critical importance regarding the procedures performed in the ear and on the eyes. These instructions are worth review