Acoustic neuromas in the elderly.

OBJECTIVE: To determine if an "observation" protocol with serial scanning is a safe and effective management paradigm for acoustic neuromas in the elderly. STUDY DESIGN: A retrospective case review was performed. SETTING: This study was performed in an academic, tertiary care center. PATIENTS: Forty-one patients over the age of 65 years were identified with the primary diagnosis of unilateral acoustic neuroma, without prior treatment or observation. INTERVENTION: The patients were followed with serial, gadolinium-enhanced magnetic resonance imaging (MRI) scans performed at 6 months and then yearly, if no significant growth occurred. MAIN OUTCOME MEASURES: The patients were monitored for tumor growth, cranial nerve deficits, and hydrocephalus. RESULTS: The patients were followed for an average of 3.5 years (range, 6 months to 9 years). The average tumor size at presentation was 1.14 cm, with a range of growth rates from 0 to 1.2 cm per year. Twenty-one patients demonstrated tumor growth at an average rate of 0.322 cm per year. Only five patients (12%) required further intervention. Three patients underwent translabyrinthine excision, and two patients were treated with radiation. No patients developed significant complications during the observation period. CONCLUSIONS: Acoustic neuromas in the older population can be managed safely using serial MRI scanning. No correlation could be made between initial tumor size and subsequent growth rate.

A comparison of efferent suppression of compound action potentials by simultaneous and non-simultaneous contralateral noise paradigms.

The intent of this study was to compare the effectiveness of continuous versus gated contralateral noise in producing efferent suppression of CAPs in guinea pigs. The average contralateral suppression was 2.0 dB when using gated noise, with ipsilateral tone-pip rates of 2 s(-1), and 1.4 dB when using continuous noise at an ipsilateral tone-pip rate of 31 s(-1). When the ipsilateral tone-pip rate employed in the simultaneous paradigm with continuous noise was reduced to 2 s(-1), a rate equivalent to that employed in the non-simultaneous paradigm, the average attenuation was 2.1 dB, a magnitude comparable to the suppression achieved using gated noise. The present data suggest that, when equated for ipsilateral tone-pip pulse rate, simultaneous and non-simultaneous contralateral masking paradigms produce comparable levels of efferent suppression.

Rosai-Dorfman disease (extranodal sinus histiocytosis) in a patient with HIV.

Rosai-Dorfman disease, or sinus histiocytosis with massive lymphadenopathy (SHML), is a rare histiocytosis of unknown etiology that most commonly involves the cervical lymph nodes. Extranodal involvement occurs in 30-40% of cases, most often in the head and neck. Characteristic histologic findings include emperiopolesis (engulfment) of lymphocytes and S-100 protein positivity. Treatment of Rosai-Dorfman disease is unnecessary unless the disorder becomes life- or organ-threatening, since the disease will resolve spontaneously in most patients. We present what, to the best of our knowledge, is the first reported case of Rosai-Dorfman disease limited to the skin in a patient infected with human immunodeficiency virus. SHML is described and diagnostic and therapeutic measures are reviewed.

Attenuation of neomycin ototoxicity by iron chelation.

Increasing evidence suggests that aminoglycoside ototoxicity is mediated by the formation of an aminoglycoside-iron complex and that the creation of this complex is a preliminary step in generation of free radical species and subsequent hair cell death. In this study we have assessed the ability of the iron chelator deferoxamine to attenuate the hearing loss induced by an ototoxic dose of the aminoglycoside neomycin (100 mg/kg per day for 14 days). Experiments were carried out on pigmented guinea pigs weighing 250 to 300 g. Changes in auditory sensitivity were characterized by monitoring shifts in compound action potential (CAP) thresholds, recorded through indwelling electrodes implanted at the round window, vertex, and contralateral mastoid. Results show that animals receiving neomycin alone suffered a mean threshold shift exceeding 35 dB at all test frequencies (2.0, 4.0, and 8.0 kHz) 30 days after initiation of treatment. In comparison, all animals receiving cotherapy of neomycin and deferoxamine (150 mg/kg twice daily for 14 days) maintained their CAP threshold, suggesting significant protection from neomycin ototoxicity. A statistical comparison of treatment groups showed that in the animals receiving cotherapy with neomycin and deferoxamine, deferoxamine produced a significant protective effect against neomycin-induced ototoxicity (P < 0.001). These results provide further evidence of the intrinsic role of iron in aminoglycoside ototoxicity and suggest that deferoxamine may have a therapeutic role in attenuating the cytotoxic action of aminoglycoside antibiotics.

Effect of cortisporin otic suspension on cochlear function and efferent activity in the guinea pig.

To predict cochlear receptor cell insult from therapeutic aminoglycoside antibiotics, we sought to determine whether the presence of subtoxic concentrations of Cortisporin otic suspension in the cochlea can be detected by measuring changes in efferent suppression of compound action potentials recorded from the round window. Olivocochlear efferent suppression in an earlier study was reversibly inhibited by injections of gentamicin in guinea pigs. Using that same technique, we found that 2.0 microliter of Cortisporin otic suspension (neomycin, polymyxin B, hydrocortisone) placed on the round window of guinea pigs in varying concentrations causes a rapid, permanent alteration in thresholds. Solutions of Cortisporin otic suspension diluted to a concentration of 1:20 yield a reversible loss of efferent suppression without measurable changes in compound action potential. These data suggest that the presence of Cortisporin otic suspension can be detected functionally in the cochlea at very low concentrations prior to the development of a threshold shift.

Outcome-oriented managed care comparing efficacies of cefaclor and amoxicillin in acute and recurrent acute otitis media.

A study utilizing outcome-oriented cure is employed to show the effectiveness of a given medical treatment. A specific patient population is studied in order to determine the most effective treatment for a common clinical disorder. A total of 201 children were retrospectively studied to evaluate the efficacy and side effects of amoxicillin and cefaclor in the treatment of acute otitis media and recurrent acute otitis media. There were 456 episodes of acute otitis media; 245 episodes were treated with amoxicillin with an efficacy of 91%, while 211 episodes were treated with cefaclor with an efficacy of 97%. The dosage of 40 mg/kg/day, divided in three equal doses, was employed for both antibiotics in the treatment of acute otitis media, while half of this amount was given once daily for the chemoprophylaxis of recurrent acute otitis media. In the 87 courses of chemoprophylaxis with cefaclor for recurrent otitis media, the efficacy was found to be 53%; while amoxicillin was found to be effective in 30% of the 33 patients studied. There were fewer side effects noted in the cefaclor group than in the amoxicillin group (4% vs. 12%). Both drugs caused diarrhea, while cefaclor also caused a mild maculopapular rash in two patients (1.67%). While amoxicillin remains the drug of choice for acute otitis media (AOM), this study suggests that cefaclor may be a better selection in the chemoprophylaxis of recurrent acute otitis media.

The role of the leader sequence coding region in expression and assembly of bacteriorhodopsin.

Bacterio-opsin is made as a precursor in Halobacterium halobium, which has 13 additional residues at the amino terminus. The codons for these residues have been proposed to form a hairpin structure in the mRNA and play a role in ribosome binding; the leader peptide sequence also has been proposed to have a role in membrane insertion of bacteriorhodopsin (BR). We have made mutations in the bop gene region coding for the leader sequence and expressed the mutant genes in an H. halobium mutant lacking wild-type BR. The leader sequence coding region was found to be important for the stability of the mRNA and for its efficient translation. Single base substitutions in this region that did not affect the amino acid sequence caused significant reductions in protein expression. Deletion of the leader region resulted in unstable mRNA and almost no BR production. Introduction of a new ribosome-binding sequence within the coding region of the mature protein restored mRNA stability and some protein expression. Protein made without the leader peptide was properly assembled in the membrane.