Literature Review: A roundup of the most important recent studies

From: ENT Today, March 2010

by Gerard Gianoli, MD, Sue Pondrom

Cincinnati Criteria Identifies More Cases of Enlarged Vestibular Aqueduct

CLINICAL QUESTION
Are otolaryngologists underdiagnosing EVA?

Background: Enlarged vestibular aqueduct (EVA) is the most commonly identified CT scan anomaly found in children with sensorineural hearing loss (SNHL). Current radiographic criteria for EVA (defined by Valvassori and Clemis in 1978, using hypocycloidal polytomography), is a vestibular aqueduct larger than 1.5 mm at the midpoint. A new criteria, the Cincinnati criteria (proposed by Boston and colleagues), based on CT scan and statistical analysis, defined EVA as ≥1.0 mm at the midpoint or ≥2.0 mm at the operculum.

Study Design: Cohort study, retrospective review. This study represents the largest CT-based assessment of vestibular aqueducts ever published.

Setting: One hundred thirty cochlear implant recipients at St. Louis Children’s Hospital

Synopsis: Of 163 patients who underwent cochlear implantation at St. Louis Children’s Hospital between January 2003 and August 2007, 242 ears (130 patients) were included for review. Measurements of the vestibular aqueduct were performed at the midpoint and at the operculum at an angle of 90 degrees from the posterior wall of the petrous bone. EVA was identified using both the Valvassori criteria and the Cincinnati criteria. The Cincinnati criteria diagnosed 44 percent of patients with EVA, compared to 16 percent with the Valvassori criteria. The Cincinnati criteria were more likely than the Valvassori criteria to diagnose bilateral EVA (45 percent vs. 36 percent). Among the 70 ears defined as EVA by the Cincinnati criteria but judged normal by the Valvassori criteria, 59 had no other reason for their hearing loss.

Bottom Line: This study supports the Cincinnati criteria for the identification of EVA in children with SNHL. The Valvassori and Clemis criteria, based on older technology, likely underdiagnose EVA.

Reference: Dewan K, Wippold FJ II, Lieu JE. Enlarged vestibular aqueduct in pediatric sensorineural hearing loss. Otolaryngol Head Neck Surg. 2009;140(4):552-558.

—Reviewed by Gerard Gianoli, MD

 

Extracapsular Dissection a Valid Option for Benign Parotid Tumors

CLINICAL QUESTION
Is extracapsular dissection a better option for benign parotid tumors?

Background: While a superficial or total parotidectomy is considered the gold standard surgical intervention for benign parotid tumors, the surgery risks intraoperative damage to the facial nerve. In fact, the rate of temporary paresis of the facial nerve is 15 to 25 percent after superficial parotidectomy and 20 to 50 percent after total parotidectomy, with a 5 to 10 percent rate of permanent facial paresis. Extracapsular dissection without exposure of the facial nerve’s main trunk has recently been favored as an alternative. Data on the incidence of facial nerve lesions and other acute postoperative complications, however, is lacking.

Study Design: Retrospective analysis between 2000 and 2008 of 934 patients operated on for a newly diagnosed benign tumor of the parotid gland. Of these, 377 (40 percent) underwent extracapsular dissection. The authors provided a classification of techniques based on the extent of dissection of the facial nerve, with extracapsular dissection being the cases in which the tumor was removed without exposure of the main trunk of the facial nerve. The function of the facial nerve was assessed pre- and post-surgery using the House-Brackmann grading system.

Setting: University of Erlangen-Nuremberg, Germany

Synopsis: Of the 377 patients in the study who had extracapsular dissection, 18 (4.8 percent) developed a fluid accumulation in the form of a seroma, 13 (3.5 percent) a hematoma in the area of the wound, eight (2.1 percent) a salivary fistula, four (1 percent) lasting disturbances of sensation, and three (0.8 percent) secondary bleeding from the area of operation. The most commonly reported unwanted effect was hypoesthesia of the cheek or earlobe, reported in 38 (10.1 percent) patients. Normal facial nerve function was seen in 346 (91.8 percent) patients postoperatively. However, 31 patients (8.2 percent) showed facial nerve weakness immediately after the operation; of these, 23 patients had complete resolution in 14 days to three months. While some point to a higher recurrence rate with extracapsular dissection and partial parotidectomy, the authors said a clear distinction should be made between the modern technique of extracapsular dissection and the historical technique of enucleation and its recurrence rates.

Bottom Line: Extracapsular dissection, which has a lower risk of postoperative complications, is a viable surgical alternative to superficial or total parotidectomy.

Reference: Klintworth N, Zenk J, Koch M, et al. Postoperative complications after extracapsular dissection of benign parotid lesions with particular reference to facial nerve function. Laryngoscope. 2010;120(3):485-491.

—Reviewed by Sue Pondrom

 

KTP and CO₂ Laser Fiber Stapedotomy Compared

CLINICAL QUESTION
What is the safety and efficacy of the OmniGuide handheld fiber for CO₂ laser stapedotomy as compared to the handheld potassium titanyl phosphate (KTP) laser in patients undergoing stapedotomy for otosclerosis?

Background: While both argon and KTP lasers can potentially have thermal effects on deep inner ear structures, CO₂ lasers have been considered safer. However, the CO₂ delivery system has been associated with damage resulting from missing the target. The new OmniGuide handheld CO₂ laser may replace the micromanipulator system.

Study Design: Prospective, nonrandomized clinical study

Setting: Jean Causse Ear Clinic, Colombiers, France

Synopsis: Surgery for otosclerosis with stapes fixation was performed in 214 patients between January 2008 and January 2009. Patients were divided into two equal groups: KTP laser fiber and flexible CO₂ laser fiber, with all procedures performed by the same surgeon. In the KTP laser group, the postoperative air-bone gap (ABG) was 4.3 dB compared to three dB in the CO₂ group. Of the patients in the KTP group, 92 percent (76 cases) had a postoperative ABG of 10 dB or less, compared to 97 percent (89 cases) in the CO₂ group. The postoperative ABG at 4 kHz was 4.9 dB in the KTP and 2.2 dB in the CO₂ group. The authors suggest that further study should look at outcomes such as tinnitus or dizziness and quality of life. Additionally, future studies might look at six and eight kHz frequencies, and a larger, randomized trial was recommended, including longer follow-up to show possible sensorineural hearing loss.

Bottom Line: The clinical safety and efficacy of both KTP and CO₂ laser for primary stapedotomy was reaffirmed, with the use of the new handheld CO₂ laser shown to be associated with slightly better hearing results, especially when assessed at the four kHz frequency.

Reference: Vincent R, Grolman W, Oates J, et al. A nonrandomized comparison of potassium titanyl phosphate and CO₂ laser fiber stapedotomy for primary otosclerosis with the otology-neurotology database. Laryngoscope. 2010;120(3):571-576.

—Reviewed by Sue Pondrom

 

BM-MSC and sECM for Vocal Fold Scarring Produces Favorable Outcome

CLINICAL QUESTION
What type of in vivo tissue engineering construct best facilitates tissue regeneration after vocal fold scarring?

Background: Vocal fold scarring is the cause of most cases of voice deficiencies after vocal fold injury. Current surgical and pharmaceutical interventions are often unsatisfactory and result in inconsistent short- and long-term outcomes.

Study Design: Stability and compatibility of bone marrow-derived mesenchymal stem cells (BM-MSC) transplanted in isolation or within an embedded synthetic extracellular matrix (sECM) were assessed with flow cytometry and immunofluorescence in 18 rats with vocal fold injury. Rats were treated with unilateral injections of saline or sECM hydrogel, along with green fluorescence protein (GFP) mouse BM-MSC or BM-MSC suspended in sECM.

Setting: University of Wisconsin-Madison

Synopsis: Comparison of flow cytometric studies of cell surface markers before and after growing mouse BM-MSC in sECM for three days indicated a preservation of extracellular marker expression, viability and mitotic activity. Combined injection of BM-MSC and sECM produced the most favorable extracellular matrix gene expression profile and a synergistic effect in hyaluronan-metabolizing enzymes gene expression compared to individual treatment. Immunofluorescence revealed persistence of GFP expression, cell proliferation, low cytotoxicity and low myofibroblast differentiation of the combined therapy. Physical constraints imposed on the study inhibited the acquisition of data from longer and shorter time points.

Bottom Line: In rats with injured vocal folds, injections with BM-MSC are beneficial in the context of an sECM in promoting ECM deposition and growth factor production without increasing myofibroblast differentiation, thereby preserving the qualities and biological competence of the replaced tissue.

Reference: Quinchia Johnson B, Fox R, Chen X, et al. Tissue regeneration of the vocal fold using bone marrow mesenchymal stem cells and synthetic extracellular matrix injections in rats. Laryngoscope. 2010;120(3):538-546.

—Reviewed by Sue Pondrom

 

A Longer Shelf Life for Antimicrobial Ear Drops

CLINICAL QUESTION
What can physicians tell patients about the shelf life of antimicrobial ear drops and when bottles might become contaminated after use in the infected ear canal?

Background: Little evidence exists regarding the shelf life of antimicrobial ear drops after opening or when patients should discard the bottle. Additionnally, little is known about contamination after use in the infected ear.

Study Design: A prospective experimental design over a four-month period. Agar plates inoculated with both Staphylococcus aureus and Pseudomonas aeruginosa were used to assess effectiveness of ear drops containing gentamicin and ciprofloxacin. Bottles were assessed for contamination once opened, and drops used for one week on patients with otorrhea were analyzed for contamination.

Setting: Vancouver, British Columbia, Canada

Synopsis: The antibiotic drops remained effective over the four-month testing period without significant reduction in the zone of inhibition measured on the inoculated agar plates. None of the unused bottles of drops became contaminated. All of the patient ear cultures were positive, but neither the bottle tip cultures nor the bottle content samples grew organisms. One limitation was that only two ear drops were analyzed. However, the two drops studied were effective against the most common microorganisms. The study did not try to differentiate between those patients with otitis externa or media, or those with granular myringitis, but instead concentrated on the symptom of otorrhea, which is common to all.

Bottom Line: Patients can keep antimicrobial ear drops for up to four months at least, for use in treating subsequent episodes of otorrhea.

Reference: Clark MP, Pangilinan L, Wang A, et al. The shelf life of antimicrobial ear drops. Laryngoscope. 2010;120(3):566-570.

—Reviewed by Sue Pondrom

 

Dehiscence Size in SSCD Correlates with Air-Bone Gap Size

CLINICAL QUESTION
Does the size of the dehiscence in SSCD correlate with the size of the air-bone gap?

Background: Patients with superior semicircular canal dehiscence (SSCD) present with a variety of symptoms that may include a low frequency conductive hearing loss on pure-tone audiometry. It has been postulated that this air-bone gap happens when the dehiscent superior canal acts as a third mobile window, dissipating acoustic energy. Not all patients exhibit an air-bone gap, however, and, to date, no study has correlated the size of the air-bone gap with the size of the dehiscence.

Study Design: Retrospective chart review of 23 patients (28 ears) diagnosed with SSCD

Setting: Tertiary referral center in Perth, Australia

Synopsis: Twenty-three patients (28 ears) met the study criteria of typical SSCD history; at least one physiologic test confirming SSCD (usually an abnormal vestibular evoked myogenic potential [VEMP]); and observation of SSCD on a high-resolution CT scan of the temporal bone. The dehiscent areas of the superior semicircular canal were measured to the nearest 0.5 mm and ranged from 1.0 - 6.0 mm (mean 3.5 ± 1.6mm). The air-bone gap was determined for 500, 1,000 and 2,000 Hz, both individually and as an average of the three frequencies. All six ears that did not have an air-bone gap had dehiscences measuring less than 3.0 mm. In the 22 ears that demonstrated air-bone gaps, the gaps ranged from 3.3 to 27 dB (mean 11.6 ± 5.7 dB). A linear regression analysis demonstrated a coefficient of 0.780 (p<0.001), suggesting that the larger the dehiscence, the bigger the air-bone gap.

Bottom Line: A low frequency air-bone gap was consistently documented in patients with SSCD where the dehiscence measures greater than 3 mm. The size of the air-bone gap increased with the size of the dehiscence.

Reference: Yuen HW, Boeddinghaus R, Eikelboom RH, et al. The relationship between the air-bone gap and the size of the superior semicircular canal dehiscence. Otolaryngol Head Neck Surg. 2009;141(6):689-694.

—Reviewed by Gerard Gianoli, MD

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