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Introduction:
Sudden deafness (SSNHL) is relatively uncommon but when it occurs, causes much concern and anxiety for patients and is a diagnostic and therapeutic challenge for otolaryngologists/ENT surgeons. SSNHL is said to occur when there is inner ear sensorineural deafness of at least 30 dB over three contiguous frequencies on pure tone audiometry occurring in a short time-span (usually 72 hours from initial onset).There must be no known causes ( eg not from head injuries or scuba-diving). It is usually one-sided and may be related to vertigo and imbalance.The patient may just present as blocked sensation, ringing sounds (tinnitus) or with actual hearing difficulty. Even without any treatment, partial recovery rate has been documented from 32% - 79%,and these usually recover within two weeks of onset. Spontaneous complete recovery is present in up to 36%. However it is not possible to predict which patients will recover spontaneously and which require treatment. SSNHL presents as an emergency as early therapy is critical to recovery. Theories of Causes of Sudden deafness:
Although actual causes are still unknown, the following are postulated to be some causes:
- Vascular injury
- intracochlear membrane rupture
- viral etiology
- autoimmune
Other known causes of sudden deafness ( Differential diagnoses) include:
| - | Infectious causes : bacterial- meningitis, labyrinthitis, and syphilis or | | - | Viral-mumps and CMV. | | - | Inflammatory and autoimmune disorders - Cogan syndrome, systemic lupus, and multiple sclerosis. | | - | Traumatic injury: temporal bone fracture, acoustic trauma, and perilymph fistula possibly due to underwater diving or exposure to high pressure. | | - | Neoplastic disorders : cerebellopontine angle tumor, internal acoustic canal tumor, and metastasis to the temporal bone | | - | Toxicity: Medications- aminoglycosides, aspirin, and chemotherapeutic agents | | - | Vascular/hematologic causes : thromboembolism, cerebral infarct, transient ischemic attack, sickle cell disease, and macroglobulinemia. | | - | Congenital malformation : Mondini malformation and enlarged vestibular aqueduct |
Diagnosis and investigations:
Thorough investigation to determine any known causes of sudden hearing loss is required and includes:
| - | detailed history | | - | complete head and neck exam with attention to the ear exam | | - | Ear (otological) tests: Tuning fork testing, otoscopy and Tympanometry | | - | Audiologic tests: pure tone audiometry (PTA), speech reception threshold (SRT), and speech discrimination score (SDS); Auditory brainstem response and otoacoustic emission; electronystagmogram (ENG) | | - | Radiology: MRI with gadolinium is the best form of radiographic study to investigate IAC/CPA tumors; CT of temporal bones in younger patients | | - | Blood tests: FBC, electrolyte, erythrocyte sedimentation rate, autoantibodies (ANA, 68 kD antibody), rheumatoid factor, FTA-Abs to evaluate for syphilis, coagulation studies, thyroid function testing, and lipid profile |
Treatment
Steroids:
The treatment of choice for SSNHL is systemic steroids which may be taken orally or by intravenous route. Historically, steroids were believed to reduce inner ear inflammation and allow recovery of hearing. An important factor of therapy is to initiate systemic steroids as early as possible. The greatest rate of recovery has been found in patients who had treatment started within 2 - 4 weeks of onset of hearing loss. Patients with profound deafness (thresholds worse than 90 dB) tend to have a variable to poor response. Systemic Steroid therapy may not be possible for all patients. For example, diabetics, patients with peptic ulcers, TB, and glaucoma, and other systemic conditions may not be able to tolerate systemic steroid therapy. For these groups of patients, steroids can be introduced directly into the middle ear/inner ear through the ear drum ie Intra-tympanic injection of steroids. Intratympanic (IT) steroids (new treatment)
| - | IT steroids may be most beneficial as primary therapy in patients unable to take to systemic steroid therapy. | | - | In addition, IT steroids may be attempted to salvage hearing in those who do not respond to systemic steroids. Studies are being done now and most data show that a significant percentage of patients can still get further improvement in hearing after initial failed systemic steroid treatment. |
The procedure is done in the clinic under local anesthesia. The procedure takes less than half hour and the patient is able to go home after about another 1/2 hour's observation. The complications of using IT steroids include TM perforation, vertigo, infection, and acne in the studies reviewed Other treatment choices used with variable to no success include:
antivirals, volume expanders, vasodilators, anticoagulants, and carbogen inhalation. Conclusion:
SSNHL is a life-altering disorder for patients and can be a challenging disorder for otolaryngologists. It is an otologic emergency and required early therapy to save hearing. The best form of therapy continues to be systemic steroids. However, IT steroids may provide another means of treating this disorder esply for those unable to tolerate systemic steroids and as a salvage treatment for failed systemic therapy.
NB: The above material is summarised from the following publication (please click on link). Some of the investigations/treatment may not be available in all centres. Please read the original literature for a full understanding of the condition. Link: http://www.utmb.edu/otoref/Grnds/SNHL-060614/SNHL-060614.doc
TITLE: Sudden Sensorineural Hearing Loss and Intratympanic Steroids
SOURCE: Grand Rounds Presentation, UTMB, Dept. of Otolaryngology
DATE: June 14, 2006
RESIDENT PHYSICIAN: Murtaza Kharodwala, MD
FACULTY PHYSICIAN: Tomoko Makishima, MD, PhD
SERIES EDITORS: Francis B. Quinn, Jr., MD and Matthew W. Ryan, MD
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