Otology and Neurotology

From Stanford Otology Course 2010

Steven A. Telian, MD, John L. Kemink Professor of Neurotology and Associate Chair and Director, Division of Otology-Neurotology, Department of Otolaryngology–Head and Neck Surgery, University of Michigan Medical School, Ann Arbor

Educational Objectives

The goal of this program is to improve the management of challenging vertigo patients, special groups of cochlear implant patients, and patients with vestibular schwannomas. After hearing and assimilating this program, the clinician will be better able to:

1.   Explain the nature, purpose, and limitations of the various vestibular neurodiagnostic tests.

2.   Review the symptoms associated with various vestibular lesions and cerebrospinal fluid abnormalities that can cause vertigo.

3.   Describe an algorithm for staging of cochlear implantation in patients with chronic otitis media.

4.   Choose the appropriate staging and surgical technique for cochlear implantation in patients with cochlear ossi­fication or inner ear malformations.

5.   Define hearing preservation in patients with vestibular schwannoma, and discuss the potential for hearing pres­ervation with various surgical approaches.

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 following has been disclosed: Dr. Telian is on the Medical Advisory Board of Cochlear Americas. The planning committee reported nothing to disclose.

Managing the Challenging Vertigo Patient

Vestibular disorders: know about vestibulo-ocular reflex (VOR), Ewald’s second law, velocity storage integrator, paramedian pontine reticular formation, vestibular compensation, and pitfalls and interpretation of vestibular test results; learn nature, purpose, and limitations of vestibular neurodiagnostics

Videonystagmography (VNG): document, lateralize, and measure severity of peripheral lesions by caloric irriga­tion; interpret in light of clinical history; if oculomotility testing normal, nystagmus peripherally generated; degree of vestibular compensation correlates with amplitude of nystagmus

Rotational chair testing: some centers use as first test for peripheral disorders; most useful for measuring severity of bilateral vestibulopathy (ie, frequencies affected by bilateral weakness); important for prognosis and patient counseling; used for evaluation of VOR in pediatric patients

Postural control testing: correlates with disability level; performed only when patient fails screening test; pattern of abnormality may direct physical therapy; exposes malingerers

Vestibular compensation: acute phase  —  brain recognizes asymmetry of peripheral inputs to vestibular nuclei; resets tonic discharge rate in weak vestibular nucleus; relieves vertigo and nystagmus within 2 to 3 days; patient continues to have chronic dysequilibrium and motion-provoked symptoms; chronic phase  —  through adaptive plasticity, brainstem responds to sensory deficits through learning process; repeated exposure to sensory conflicts provides necessary information; inactivity and sedating medications interfere with compensation

Categories of Vestibular Disorders

Peripheral lesions: uncompensated patient stable after previous vestibular crisis; fluctuating disorders – Meniere disease, delayed endolymphatic hydrops; intermittent disorders  —benign paroxysmal positional vertigo (BPPV), superior canal dehiscence; progressive disorders  —  associated with increased hearing loss (eg, perilymph fistula, autoimmune ear disease); bilateral vestibulopathy

Unstable vestibular lesions: Meniere disease  —  intense episodic vertigo spells; patient usually normal between spells; fluctuating or progressive hearing loss; vestibular testing results normal or may show caloric weakness or phased lead on rotational chair; candidates for surgery if not stabilized medically

Uncompensated stable lesions: history of previous intense vestibular crisis; ongoing symptoms of motion-provoked vertigo; no spontaneous vertigo spells; stable and sometimes normal hearing; abnormalities detected on vestibu­lar tests (eg, spontaneous and positional nystagmus, abnormal postural control); patients not good surgical candi­dates; treat with vestibular rehabilitation (»75% have complete or meaningful improvement)

Patterns in BPPV: nystagmus  —  both posterior and superior canal disease create torsional nystagmus toward down­ward ear in Hallpike position; must recognize vertical components, ie, whether upbeating or downbeating; canalithiasis  —  latent onset; transient in position testing and fatigues if position testing repeated; nystagmus not suppressed by vision; cupulolithiasis  —  caused by otoconia mass loading ampulla, making it gravity sensi­tive; immediate onset of nystagmus upon assuming position; not transient; not fatigable

Superior canal dehiscence: more common than previously thought; suspect in patients with vertigo and conductive hearing loss, especially if bone conduction supranormal; tuning fork on ankle test, when positive, corresponds 100% to superior canal dehiscence; summating potential to action potential ratio (SP/AP) elevated on electroco­chleography (ECoG)

Cerebrospinal Fluid (CSF) Abnormalities

Intracranial hypertension: symptoms  —  pulsatile tinnitus; bilateral ear fullness; vague nonspecific dizziness; con­firmed by opening pressure measurement on lumbar puncture; occasionally requires treatment with acetazolamide (Diamox) or, in severe cases, shunt

Intracranial hypotension: symptoms  —  headache when upright and episodic vertigo in some; caused by low lumbar arachnoid defect that ruptures spontaneously, leading to CSF pressure and low-pressure headache; patients have diffuse thickening and enhancement of dura without chronic meningitis; treated with epidural blood patch

Vestibular migraine: common; patient history  —  hormonal influences (eg, menarche, premenstrual period, preg­nancy, perimenopause, postmenopause); family or personal history of migraine; history of motion intolerance; vi­sual auras; unexplained ear pain; not necessary to have headache; manage acute attacks with benzodiazepines (eg, sublingual lorazepam [Ativan]); triptans effective in »1 in 10 patients, and possibly dangerous; lifestyle modifications  —  regulate sleep/wake cycle and exercise; identify dietary triggers; prophylactic daily medication  —  b-blockers, calcium channel blockers, selective serotonin reuptake inhibitors, and tricyclic antidepressants; imag­ing studies  —  review and possibly repeat magnetic resonance imaging (MRI)

Chiari malformations: consider if sagittal MRI cut shows cerebellar tonsils hanging down below foramen magnum; can cause downbeating nystagmus without torsional component

Challenges in Cochlear Implantation

Chronic otitis media: dry perforation or atelectasis of tympanic membrane (TM); draining ear; cholesteatoma or chronically infected mastoid cavity; potential for intracranial spread of infection, device infection requiring re­moval, or electrode exposure; staged procedure  —  start with routine chronic ear operation to obtain more normal ear or to obliterate mastoid cavity; place implant later; single-stage procedure  —  repair perforation at time of im­plantation; in case of mastoid cavity, elevation of dense lining, resection of ear canal, followed by meatal closure and/obliteration of middle ear and mastoid; middle cranial fossa approach  —  to gain access to cochlea

Algorithm: single stage — 1) in case of thick blunted mastoid cavity with dense scar (3-4 mm) over bone, make postauricular incision and carefully elevate scar; if facial ridge low, can usually expose round window without dissecting over tympanic segment of facial nerve; gain access and place implant; 2) in case of dry TM perforation or clean mastoid cavity, single-stage external auditory canal closure and implantation possible; 3) 2-stage  —  for cholesteatoma or chronically infected mastoid cavity, eradicate infection in first stage; close external auditory ca­nal and let ear recover for »2 mo, then perform cochlear implantation

Technique for closure of ear canal: do not use blind-sac umbilicated closure; modified Rambo closure  —  incisions at 6 and 12 o’clock; carry out to conchal bowl; resect posterior ear canal skin and some conchal bowl skin; resect anterior canal bony skin; elevate anterior cartilaginous skin off tragus and suture to create curved incision closed within conchal bowl; verify removal of all squamous epithelium in ear canal; speaker performs limited canal­plasty to ensure visualization of anterior sulcus; obtain computed tomography (CT) 1 to 2 yr after surgery to check for iatrogenic cholesteatoma; avoid obliteration — easier access to ear for second stage; easier to detect developing cholesteatoma; only disadvantage possibility of infection by contamination through patent eustachian tube; in small children, acute otitis media may occur

Cochlear ossification: causes  —  bacterial labyrinthitis related to meningitis; advanced otosclerosis; temporal bone fractures that go through ear often cause ossification; autoimmune inner ear disease; vascular occlusion; ossifica­tion correlates with decreased spiral ganglion cell survival, particularly after meningitis; degree of ossification can vary; most cases minimally ossified and allow drilling through near round window  to achieve adequate lu­men and full insertion of standard electrode; major degrees of ossification require variation in technique; for pa­tients with evidence of ossification or previous meningitis, obtain MRI and CT to evaluate cochlear lumen; plan and counsel patient

Meningitic hearing loss: study  —  prelingually deaf children with cochlear ossification who had ³2 yr follow-up af­ter cochlear implantation; group with minimal ossification (<7 mm) performed only marginally better than those with major ossification on tests of speech perception; study  —  in matched-pairs analysis of children with ossifica­tion vs those without ossification, those with ossification of any degree lagged behind in speech perception; chil­dren with cochlear ossification who receive cochlear implants have improved speech perception relative to before surgery but lag behind children who do not have ossification; study  —  full electrode insertion in children deaf­ened by meningitis (some with minimal ossification, others with none) vs children with congenital hearing loss; meningitis of any kind affected outcome; performance in children without ossification tended to  equal that of children with congenital hearing loss; children with minimal ossification performed less well (suggests relation­ship to survival of spiral ganglion cells)

Inner ear malformations: implant not contraindicated; prognosis correlates with severity of malformation; need to know if stimulable neural elements present in ear; obtain MRI and CT in all cases; can also obtain electrical au­ditory brain stem responses (ABR); associated abnormalities in temporal bone development and facial nerve lo­cation often present; address CSF control; consider device selection in terms of nature of implant electrode and complication of internal auditory canal (IAC) insertion in widely patent IACs; speaker performs ABR test in all children with normal temporal bone development but no measurable behavioral responses to amplification; “re­ally bad” IACs narrow and do not go near cochlea; however, better cochlea associated with really bad IAC; Mon­dini dysplasia with healthy IAC usually correlates with good response and near complete insertion

Study: tested open-set sentence recognition in children with various levels of severity; open-set discrimination more likely to occur in Group 1 (mild malformation; 73% at 36 mo); 3 of 8 patients in Group 3 had open-set dis­crimination

Hearing Preservation in Vestibular Schwannoma Surgery

Retrosigmoid approach: advantages  —  possible hearing preservation; reliable facial nerve outcomes; disadvantages  —intradural drilling; poor IAC access

Middle fossa approach: advantages  —  may provide better IAC exposure; better hearing results; disadvantages  —  technically demanding; possibility of facial paralysis

Stereotactic radiation: easier on patient and physician; avoids most surgical risks; long-term control rates uncertain

Surgical considerations: preservation of auditory nerve; no violation of otic capsule; preservation of cochlear blood supply (most likely association with hearing loss); monitor facial nerve intraoperatively with ABR or direct co­chlear nerve recording; patient selection critical to hearing results; failure to preserve hearing is disappointment, not complication; estimate likelihood of success to help patient make decision; ideal candidate has intracanalicular tumor, not impacted into IAC, excellent residual hearing, robust ABR waves, and perhaps caloric weakness (does not improve prognosis)

Definition of hearing preservation: American Otological Society guideline  —  adopted Gardner-Robinson hearing scale; Class A defined as speech reception threshold (SRT)  >30 dB and speech discrimination  >70%; Class B de­fined as SRT >50 dB and speech discrimination >50%; surgical successes  —patients with Class A or B hearing be­fore and after surgery; Class C patients who remain Class C (or better) after surgery; Class D patients who remain Class D (or better)

Hearing results with retrosigmoid approach: in patients with Class A hearing before surgery speaker successfully preserved hearing in 44% of cases (53% with tumors <15 mm); in patients with Class B hearing, speaker preserved hearing in 2 patients with small tumors

Hearing results with middle fossa approach: House Ear Institute study  —  of 150 patients, large number had mea­surable hearing after surgery; facial nerve preservation rates similar to translabyrinthine and retrosigmoid ap­proaches; Arts et al (2006)  —  71 patients; 6 tumors >15 mm; among patients with Class A hearing preoperatively, 80% remained Class A or B postoperatively; among patients with Class B hearing, 75% in Class B or C postopera­tively; among patients with Class C hearing, 66% preserved hearing in that class; “pretty good” success for tumors >15 mm; published series to 2006  —demonstrated excellent hearing results by any measure; facial nerve preserva­tion rate (House-Brackmann Class 1 or 2) in 95% range; comparison study  —  retrosigmoid vs middle fossa ap­proach; middle fossa approach associated with dramatically improved hearing preservation rate; similar facial nerve results; slight reduction in CSF leak problems

Technical factors: use inferiorly based trap-door scalp flap; use instruments that allow attachment of low-profile re­tractor to retract brain; elevate scalp flap and temporalis muscle and take substantial bone flap; patient positioning critical; avoid over-rotating patient; do not flex head toward floor; adequate craniectomy in correct spot critical for access; safe areas deep to cochlea and vestibular system on both sides of IAC; 14% to 34% of lateral IAC obscured by transverse crest or facial nerve; after tumor removal, exposure into cerebellar pontine angle good; blue line semicircular canal and take bone all the way to that; work over IAC and anteriorly; low-profile retractor, vision of middle meningeal and some dural attachments near Meckel’s cave critical; preserving hearing in small acoustic neuromas with excellent hearing worthwhile goal

Patient education: inform patients properly, accurately, and fairly; consider surgery for small relatively asymptom­atic tumor (best and possibly only chance of retaining hearing in both ears); serious complications rare; potential risks with radiation  —  hearing loss earlier; dizziness hard to treat; rare complications from damage to adjacent brain structures; small risk for malignant degeneration of tumor; potential risks of surgery  —  may go deaf now rather than later; must compensate for loss of balance function in one ear; facial paralysis or serious complication; for patients who want to avoid surgery, speaker does not recommend immediate irradiation; if tumor small and hearing good, wait and watch; balance against increased risk as tumor grows

Acknowledgements

Dr. Telian was recorded at Stanford Otology Course 2010, held November 4-6, 2010, in Palo Alto, CA, and presented by Stanford University School of Medicine, Department of Otolaryngology–Head and Neck Surgery. The Audio-Di­gest Foundation thanks the speaker and Stanford University School of Medicine for their cooperation in the produc­tion of this program.

Suggested Reading

Arts HA et al: Reversible electrocochleographic abnormalities in superior canal dehiscence. Otol Neurotol. 2009;30(1):79-86; Arts HA et al: Hearing preservation and facial nerve outcomes in vestibular schwannoma surgery: results using the middle cranial fossa approach. Otol Neurotol. 2006;27(2):234-41; Carey JP, Della Santina CC. Principles of Applied Ves­tibular Physiology. In: Flint PW, et al, eds. Cummings Otolaryngology – Head and Neck Surgery. 5th ed. Philadelphia, PA: Mosby; 2010:2276-2304; Driscoll CL et al: Is the entire fundus of the internal auditory canal visible during the middle fossa approach for acoustic neuroma? Am J Otol. 2000;21(3):382-8; El-Kashlan HK et al: Cochlear implantation in chronic suppurative otitis media. Otol Neurotol. 2002;23(1):53-5; El-Kashlan HK et al: Cochlear implantation in prelin­gually deaf children with ossified cochleae. Otol Neurotol. 2003;24(4):596-600; Kim AH et al: Transient evoked otoacous­tic emissions pattern as a prognostic indicator for hearing preservation in acoustic neuroma surgery. Otol Neurotol. 2006;27(3):372-9; Kim AH et al: Role of electrically evoked auditory brainstem response in cochlear implantation of chil­dren with inner ear malformations. Otol Neurotol. 2008;29(5):626-34; Meyerhoff WL et al: Modified Rambo meatoplasty in translabyrinthine tumor removal. Otolaryngol Head Neck Surg. 1991;104(1):100-2; Meyerhoff WL et al: Rambo proce­dure: modification and application. Laryngoscope. 1988;98(7):795-6.