SUDDEN SENSORINEURAL HEARING LOSS
I. DEFINITION:
A. Greater than 30 db NON-FLUCTUATING SNHL in three contiguous frequencies developing over a period of three days.
II. INCIDENCE:
A. Estimated at 1 in 10,000 although likely higher as many don’t seek immediate treatment.
B. No gender, geographic, or seasonal tendency
C. Mixed opinion on age (30 to 60 year olds)
D. No predominance from R v. L ear
E. Typically unilateral
III. PRESENTATION:
A. Usually notice hearing loss upon awakening in the morning. Can occur suddenly, over hours, or days. Some notice by using the telephone.
B. May c/o tinnitus.
C. May c/o vertigo.
IV. ETIOLOGY
(THREE MAJOR THEORIES)
A. Vascular
1. Sudden onset consistent w/ vascular type problems
2. Inner ear intolerant of ischemia
a. With 60 sec. of anoxia there is loss of cochlear microphonic and eighth nerve action potentials
b. With interruption of cochlear bloodflow for 30 min., cochlear potentials are permanently depressed.
3. Systemic vascular diseases or connective tissue disorders such as Buerger’s disease, Cogan’s syndrome, Waldenstrom’s macroglobulinemia, polyarteritis nodosa, polycythemia rubra vera, relapsing polychondritis, sickle cell disease, and diabetes mellitus all have had reported cases of Sudden SNHL.
4. Polycythemia rubra vera and Waldenstrom’s showed some response w/ phlebotomy
5. Bypass surgery w/ microemboli (0.1%)
6. Acoustic tumor w/ proposed vascular compromise
7. SSNHL has been associated w/ patients w/ cerebellar CVA
a. AICA or PICA are suspected vessels
b. Clinical evidence of cerebellar findings (i.e. past pointing)
8. Most tenuous blood supply is to cochlear apex so one would expect low frequencies to be affected the most, but not supported clinically.
a. Low frequency losses tend to recover better.–EVEN WITH TRAUMA
b. Would expect vascular lesions to be permanent.
9. Most patients don’t have systemic vascular problems which also refutes this theory.
a. Known vasculopaths don’t show correlation w/ Sudden SNHL
B. Infectious
1. 63% OF Patients w/ Sudden SNHL have higher incidence of seroconversion to mumps, rubeola, zoster, CMV, and influenza B as compared to controls.
2. 1/3 of patients remember having had URI one month prior to hearing loss.
3. Otosyphilis
4. Lyme disease
5. Mycoplasma Pneumonia
6. Infectious Mononucleosis
7. Shuknecht demonstrated temporal bone pathology SSNHL to be consistent w/ viral cochleitis.
a. Atrophy of Organ of Corti, stria vascularis, tectorial membrane, and preservation of neural population.
8. Sudden SNHL is not seasonal or epidemic which rules against it.
9. RAMSEY HUNT SYNDROME
C. Labyrinthine-Membrane Rupture
1. Theory introduced by Goodhill
a. Implosive results from increased pressure from the middle ear space to perilymph
b. Explosive results from increased pressure via CSF
2. Simmons postulated double leak theory
a. One leak at oval/round window, the other leak intracochlear
b. Hearing loss attributed to mixing endo/perilymph w/ ionic potential disturbances. Corrects w/ healing of the membrane.
3. Gussen reported T-bone findings of ruptured Reissner’s membrane w/ balloon-like healing from rupture into the scala vestibuli.
V. EVALUATION
A. Sudden SNHL needs a complete work up and evaluation by an Otolaryngologist
B. History should focus on onset, vertigo, tinnitus, recent infection, systemic disease, medication, barotrauma.
C. Exam to focus on CN exam, fistula test, nystagmus—-THINK FISTULA!!
D. Complete audiogram
E. Lab work up: ESR, HPD, Hyperlipidemia, MHA-TP, Lyme titers, T4/TSH, HIV, Hgb A1C
F. ENG
G. MRI w/ Gadolinium—–18% ON IOWA STUDY—MS OR ACOUSTIC NEUROMA
H. WHAT COULD IT BE????? (See Laundry list)
VI. TREATMENT
A. CORTICOSTEROIDS AND VALCYCLOVIR 80 MG PO Q D
1. Several studies have shown that steroids were beneficial as compared w/ placebo group.(Moderate Loss by audiogram were shown to do best)
B. CARBOGEN—-VASODILATOR—SHOWN TO BE OF BENEFIT
1. Inhaled mixture of 95% O2/5% CO2 to increase oxygenation in perilymph
2. One study showed carbogen had better hearing 1 year out compared w/ IV papaverine/dextran
C. VASODILATORS—-HEPARIN
1. No study support, some argue it has deleterious effect by shunting away
2. Histamine, papaverine, atropine, procaine have all been used
3. Sympathetic denervation w/ stellate ganglion block has been advocated
D. DIURETICS
1. Used to treat endolymphatic hydrops
2. Furosemide and ethanicrinic acid have both been associated w/ hearing loss.
E. ANTICOAGULANTS—-HEPARIN
1. Jaffe showed abnormal prothrombin consumption times in SSNHL pts.
2. Low dose Heparin was used but no improvement over controls found
F. PLASMA EXPANDERS
1. Low-molecular weight dextran has been used as a plasma expander for sludging (theoretically)
2. Adverse side effects include allergic reactions and renal failure
G. DIATRIZOATE MEGLUMINE (HYPAQUE)
1. Discovered incidentally by Morimitsu.
2. He then Rx 39 patients w/ Hypaque and compared to vasodilator treatment. Hypaque group did significantly better
3. Theories include a filling of the open membrane pore of the cochlear-blood barrier. This results in reactivation of the sodium pump and restoration of the DC potential.
4. Also felt that Hypaque causes release of natural vasodilators (Histamine and serotonin)
5. Downside is fatal reactions to Hypaque occur in 1 of 10,000
H. SHOTGUN
1. Combining several of the above treatments as you do not know the etiology of the hearing loss.
I. CONSERVATIVE
1. Bed rest, steroids, stool softeners, low salt-caffeine diet, no ETOH, no stimulants, elevate HOB, steroid Rx.
J. SURGERY
1. Exploration for fistula if suspicion is high.
VII. PROGNOSIS
A. Five Factors to consider
1. initial audiogram (see handout)
a. Upsloping or mid frequency loss do better than downsloping
b. Severity of hearing loss is proportional to rate of recovery
2. Age
a. <15 y.o. or >60 y.o. do worse.
3. Vertigo/ENG abnormalities
4. Time to onset of therapy
a. Pts seeking care within 10 days do better than those waiting 30 days
5. Type of therapy
a. Steroids seem to help some patients
B. Miscellaneous facts
1. 70% recover spontaneously–45% with complete return
2. >ESR of 25 do worse.
3. 1% of SSNHL will have acoustic neuroma
4. 13% of acoustic neuroma pts present with SSNHL
5. RULE OF THUMB—RULE OF 1/3RDS 1/3 RESOLVE COMPLETELY, 1/3 PERMANENT LOSS AND THE REST SOMEWHERE IN BETWEEN
Recent recommendations really just key on Steroids. 50% response vs a 30% without. A 50% improvement in outcomes. Intratympanic seems a bit superior. Microwick seems an interesting idea.
Bilateral Progressive or Fluctuating Hearing Loss —-CBC, RF, ESR, CRP, MHATP, Lyme Titers, and in kids Thyroid Labs and UA.