Issues in Otology

Educational Objectives

The goals of this program are to improve the management of patients with acoustic neuromas and infants who require cochlear implantation. After hearing and assimilating this program, the clinician will be better able to:

1.   Choose appropriate treatment for the patient with an acoustic neuroma.

2.    Explain the various surgical approaches used in the operative management of an acoustic neuroma.

3.    Summarize recent technical advances in the intraoperative and postoperative care of the patient with an acous­tic neuroma.

4.    Describe tests used in newborn hearing screening and follow-up.

5.    Participate in the team providing preoperative testing and postoperative care for infants and young children who require cochlear implantation.

Faculty Disclosure

In adherence to ACCME Standards for Commercial Support, Audio-Digest requires all faculty and members of the planning committee to disclose relevant financial relationships within the past 12 months that might create any personal conflicts of in­terest. Any identified conflicts were resolved to ensure that this educational activity promotes quality in health care and not a proprietary business or commercial interest. For this program, the faculty and planning committee reported nothing to disclose.

Acknowledgements

Dr. Leonetti spoke at Innovations in Otolaryngology, presented March 14, 2009 in Maywood, IL, and sponsored by Loyola University Chicago Stritch School of Medicine, Department of Otolaryngology–Head and Neck Surgery, and the Division of Continuing Medical Education.  Dr. Evans addressed The Twenty-Ninth Annual James A. Harrill Lecture, presented April 24-25, 2009, in Winston-Salem, NC, by the Department of Otolaryngology, Wake Forest University, School of Medicine, Winston-Salem, NC.  The Audio-Digest Foundation thanks the speakers and the sponsors for their cooperation in the pro­duction of this program.

Acoustic Neuromas: Innovations in Treatment

John P. Leonetti, MD, Professor and Vice-Chair, Department of Otolaryngology–Head and Neck Surgery, and Director of Otology, Neurotology, and Skull-Base Surgery, Stritch School of Medicine, Loyola University, Chi­cago, IL

Natural history of acoustic neuroma (AN): benign tumors that grow slowly (»1 mm/yr); originate from vestibular nerve; enlargement compresses blood supply to cochlear nerve, causing presenting symptoms of progressive unilat­eral sensorineural hearing loss (SNHL) and tinnitus; do not cause dizziness or vertigo because vestibular system of contralateral ear compensates; as enlargement continues, AN can compress cerebellum, causing ataxia; incidence  —1 in 100,000 people per year; comprise 90% of tumors of cerebellopontine (CP) angle (meningiomas »5%; epidermoids 2%-3%)

Symptoms: after SNHL and tinnitus, facial numbness and decreased corneal response due to vertical growth of tu­mor; facial nerve rarely involved, so facial paralysis seldom seen; AN pushes nerve out, while meningiomas invade nerve, causing facial paralysis; many patients asymptomatic (AN discovered incidentally), especially younger pa­tients in whom neural tissue more elastic

Diagnosis: history and physical examination; audiometry; if audiogram shows unilateral SNHL, auditory brainstem response (ABR) next; if ABR normal, chance of having AN extremely low (repeat audiography in 1 yr); if ABR ab­normal, perform magnetic resonance imaging (MRI; can detect tumor as small as 2 mm); if hearing poor, ABR can­not be used (go directly to MRI); computed tomography (CT) used only if patient cannot tolerate MRI (due to, eg, claustrophobia, pacemaker); CT less accurate, requires contrast, and cannot detect small intracanalicular tumors

Complications: compression of brainstem and fourth ventricle may result in hydrocephalus and coma (emergent sur­gery indicated); acute SNHL  —  slowly growing tumor can acutely occlude cochlear artery; however, most acute SNHL due to viral inflammation or cochlear artery occlusion unrelated to tumor; treated with steroids (oral and in­tratympanic); other lesions  —  eg, hemangiomas, lipomas (majority benign); metastatic lesions (eg, from breast can­cer) cause facial paralysis and pain

Treatment options: MRI surveillance  —  for elderly patients with small tumors; no treatment needed; radiation therapy  —  educate patients about risks, advantages and disadvantages; tumor does not go away or shrink; may cause hearing loss, facial twitching, or facial paralysis; may cause tumor to become cystic and grow into brainstem; radiation failures make surgery more difficult because tumor now welded to facial nerve and planes obliterated; hearing cannot be saved after tumor irradiation; tumor histology does not change (no fibrosis); irradiation of fifth nerve causes relentless facial pain; incidence of postoperative infection increased; surgical resection  —  goals to save facial nerve, save hearing, and have low recurrence rate

Surgical Techniques

Middle cranial fossa approach: remove window of squamous portion of temporal bone above ear; extradurally ele­vate temporal lobe; reach down into internal auditory canal; saves hearing

Retrosigmoid approach: for tumors that extend into CP angle; open skull behind sigmoid sinus and drill off back, bottom, and top of internal auditory canal; teamwork  —craniotomy performed; otolaryngologist drills internal auditory canal and removes intracanalicular portion of tumor; neurosurgeon removes part of tumor next to brain­stem

Translabyrinthine approach: in front of sigmoid sinus; drill through semicircular canals; most direct route to inter­nal auditory canal for patients who have profound hearing loss or tumors so large that attempt to save hearing un­realistic

Combined retrosigmoid and translabyrinthine approach: for very large tumors

Technical advances

Improved MRI: contrast (gadolinium) makes definitive diagnosis; screening MRI  —  coronal section only, with and without contrast; less expensive; used for follow-up after surgery to detect recurrence

Monitoring of facial nerve: performed throughout surgery; electrodes inserted in facial musculature (real time mon­itoring)

Monitoring of hearing: audiologist performs equivalent of ABR during surgery; if wave forms start to alter, surgeon can modify technique to save hearing

Modification of surgical technique: before surgery, depending on individual patient parameters (eg, size and loca­tion of tumor)

Postoperative advances

Screening for deep venous thrombosis: protocol to prevent pulmonary embolism

Early balance therapy: starts in operating room; surgery severs vestibular nerve; patients with smaller tumors have more problems with balance than those with larger tumors, because larger tumors have already forced compensation by contralateral vestibular apparatus; since balance function maintained on side with small tumor, these patients have more nausea, vomiting, and vertigo; reduces recovery time (most patients return to work after 1 mo

Facial retraining physical therapy: patients seldom have facial paralysis, since facial nerve stretched but not cut, and paralysis always temporary; stretched nerve may take £6 mo to recover; therapy starts at first sign of return of fa­cial movement; this reduces length of recovery and amount of synkinetic movement

Hearing preservation: achieved two-thirds of time; if hearing lost, bone anchored hearing aid may be used

Cerebrospinal fluid leaks: rate 4% at speaker’s institution; if leak through nose via eustachian tube, patient returned to operating room for repair to prevent meningitis

Follow-up: 9 yr; MRI 1 yr, 4 yr, and 9 yr after surgery; most recurrences small and intracanalicular and do not re­quire surgery

Challenges: improvement of monitoring of hearing (signal-averaged ABR not real time; 4-10-sec lag); prevention of delayed facial weakness; maintenance of cochlear blood flow  —  gives better chance for hearing preservation; co­chlear nerve not cut, but cochlear artery small, and if spasm, kink or occlusion occurs, hearing damaged

Neurofibromatosis type 2 (NF2): patients have multiple tumors and bilateral AN; deafness inevitable; remove tumor in ear with worst hearing first; when surgery required in second ear, auditory brainstem implant placed; if hearing still lost, bone anchored hearing aid used

Cochlear Implantation in Babies

Adele K. Evans, MD, Assistant Professor, Department of Pediatric Otolaryngology, Wake Forest University Baptist Medical Center, Brenner Children’s Hospital, Winston-Salem, NC

Congenital hearing loss: incidence  —  profound congenital hearing loss seen in 1 in 1000 live births (50% genetic; 50% environmental); 400 hereditary syndromes; majority of nonsyndromic hereditary hearing loss due to autoso­mal recessive disorders, followed by autosomal dominant and X-linked disorders

Etiology of acquired hearing loss: infection; intrauterine exposure to drugs or alcohol; noise in neonatal intensive care unit (NICU); antibiotics; perinatal meningitis; metabolic disorders (eg, glycogen storage disorder)

Audiometric evaluation: passive testing  —  mandatory in newborn; includes ABR and otoacoustic emissions (OAE); active testing  —  in older infants; include behavioral audiometry; visually reinforced audiometry; play audiometry; standard pure tone audiometry

Universal newborn hearing screening: in most states, required before infant leaves hospital or NICU; choice of ABR (preferred at speaker’s institution) or OAE; data available to audiologists in state; infants with referred ear must see audiologist; further testing  —  OAE used to supplement and confirm information from ABR; tympano­grams show whether debris in ear canal or fluid in middle ear contributing to problem; facilitates early medical evaluation; »3 in 1000 have hearing loss of ³30 decibels (dB); sedation  —  in young infants, ABR performed during natural sleep; sedation needed for older infants; if sedation required for medical procedure, eg, tube placement, ABR done at same time in operating room; hearing aid fitting  —  ear molds also made while child sedated in OR; hearing aids made, and child reevaluated after trial period

Medical evaluation: imaging, primarily CT; MRI secondary mode; electrocardiography; urinalysis; ophthalmologic evaluation; genetic assessment  —  genes for connexin 26; genes for aminoglycoside sensitivity; genes linked to auditory neuropathy and ability to respond to cochlear implantation; gives parents prognosis for patient and helps them with family planning

Findings on CT: anatomy of inner ear; cochlear aplasia or hypoplasia consistent with SNHL; enlarged vestibular aqueduct may indicate progressive SNHL and need for follow-up; locates facial nerve in patients with craniofa­cial anomalies; ossicular abnormalities also determined from CT

MRI findings: for further investigation of patients in whom presence of nerves in internal auditory canal not certain, eg, patients with flat ABR since birth; important in patients with developmental delay; helpful in patients with coloboma, heart defects, choanal atresia, retardation of growth, genital and/or urinary abnormalities, and ear ab­normalities (CHARGE syndrome) to determine symmetry and presence of nerves in inner ear; MRI used to fol­low children with developmental delay for demyelinating disorders and multiple infarcts, and to determine stability of infarcts

Other tests: electrocardiography  —  helps prevent sudden cardiac death in patients with syndromic deafness (eg, prolonged QT syndrome) by allowing early start of medical treatment; urinalysis  —  to look for proteins asso­ciated with Alport’s syndrome; ophthalmologic examination  —  to detect retina and lens problems, and herita­ble myopias; coloboma, retinitis pigmentosa (suggests Usher’s syndrome)

Reasons for cochlear implantation: if otherwise healthy child receives implant by 1 yr of age, he or she will be able to join regular kindergarden class; if deafness not addressed, 30% of children with single-sided deafness fail one grade; aural rehabilitation dramatically reduces cost to education system and facilitates entry into social community

Implant team: at speaker’s institution, includes speech pathologist, 3 pediatric audiologists, and 2 pediatric otolaryn­gologists; meets monthly to discuss patients with hearing loss and those whose hearing status is changing; meets quarterly to discuss patients who have recently become candidates for implantation, those preparing for implanta­tion, and those in postimplantation stage; discussion includes medical status as well as supporting information, eg, ability to acquire language and communication skills, family circumstances, management of family problems in conjunction with pediatrician and social worker

Medical requirements for implantation: profound SNHL; minimal to no benefit from 3-mo trial of hearing aid; suf­ficiently patent cochlea; medical stability; Centers for Disease Control and Prevention require pneumococcal vacci­nation; speaker prefers that pneumococcal, influenza, and meningococcal vaccines be current

Preimplantation evaluation: speech and language  —speech pathologist reports on how babies appear to re­spond to environmental stimuli and on their efforts to begin oral communication; genetic testing  —  genetics experts communicate with team; developmental pediatrician  — determines whether patient is good candidate de­velopmentally, ie, whether development such that implant will make difference in child’s life; this allows parents to form realistic expectations for child’s progress; psychosocial evaluation of family  —  to determine whether parents or caregiver will follow through with child’s postoperative care and rehabilitation, eg, bring child back for appoint­ments, ensure that child wears device, properly maintain device

Surgery: preoperative work-up  —  address cardiac abnormalities, if present; ensure patient will be stable during sur­gery; plan to work around anatomic abnormalities that may affect implantation; neural response telemetry  —  used intraoperatively to assess implant function (ie, implant effectively stimulating nerve); gives audiologist idea of where to start programming

Postoperative care: device activated 2 to 4 wk after surgery; ongoing speech therapy; repeated audiologic mapping; electronic adjustments to device; preparing device for use in classroom; transition from body-worn pack used in in­fants to ear-level battery pack used in older children; modification of ear pieces for comfort, if necessary; checking of skin for magnet-associated tissue necrosis

Future trends: ear-level battery packs, even for small children; transcutaneous implantation using robotic guidance; auditory brainstem implant for absent or damaged cochlear nerve; bone-anchored hearing aids

Suggested Reading

Browne S et al: Patients' quality of life, reported difficulties, and benefits following surgery for acoustic neuroma. J Otolar­yngol Head Neck Surg, 37:417, 2008; Chadha NK et al: Bilateral cochlear implantation in children with anomalous co­chleovestibular anatomy. Arch Otolaryngol Head Neck Surg. 135:903, 2009; Kano H et al: Predictors of hearing preservation after stereotactic radiosurgery for acoustic neuroma. J Neurosurg, 111:863, 2009; Kondziolka D et al: Com­parison of management options for patients with acoustic neuromas. Neurosurg Focus, 14:e1, 2003; Kondziolka D et al: Future perspectives in acoustic neuroma management. Prog Neurol Surg. 21:247, 2008; Leonetti JP et al: Facial nerve monitoring in otologic surgery: clinical indications and intraoperative technique. Ann Otol Rhinol Laryngol, 99:911, 1990; Myrseth E et al: Vestibular schwannoma: surgery or gamma knife radiosurgery? A prospective, nonrandomized study. Neurosurgery, 64:654:61, 2009; Nelson HD et al: Universal newborn hearing screening: systematic review to update the 2001 US Preventive Services Task Force Recommendation. Pediatrics 122:e266, 2008 Erratum in: Pediatrics. 122:689, 2008; Ryzenman JM et al: Facial paralysis and surgical rehabilitation: a quality of life analysis in a cohort of 1,595 pa­tients after acoustic neuroma surgery. Otol Neurotol, 26:516, 2005; Scherf F et al: Three-year postimplantation auditory outcomes in children with sequential bilateral cochlear implantation. Ann Otol Rhinol Laryngol. 118:336, 2009; Timmer FC et al: Gamma knife radiosurgery for vestibular schwannomas: results of hearing preservation in relation to the cochlear radiation dose. Laryngoscope, 119:1076, 2009; Verma S et al: Evaluation of cost effectiveness for conservative and active management strategies for acoustic neuroma. Clin Otolaryngol, 34:438, 2009; Wiley S et al: Auditory skills development among children with developmental delays and cochlear implants. Ann Otol Rhinol Laryngol. 117:711, 2008.