Contribution of intracranial vertebral artery asymmetry to vestibular neuropathy.

OBJECTIVES: To test the hypothesis that vertebral artery hypoplasia (VAH) may affect the lateralisation of vestibular neuropathy (VN), probably through haemodynamic effect on the vestibular labyrinth. METHODS: 69 patients with unilateral VN were examined with a magnetic resonance angiographic (MRA) and caloric test. 50 healthy subjects served as controls. The diagnosis of intracranial VAH was based on MRA if <0.22 cm in VA diameter and a diameter asymmetry index >40%. The authors then correlated the canal paretic side with the VAH side. RESULTS: MRA study revealed 29 VAH (right/left: 23/6) in VN subjects and six VAH in controls (right/left: 5/1). The RR of VAH in VN subjects compared with controls was elevated (RR=2.2; 95% CI 1.8 to 2.8). There was a high accordance rate between the side of VAH and VN. Among 29 patients with unilateral VAH, 65.5% (N=19) had an ipsilateral VN, in which left VAH showed a higher accordance rate (83.3%) than the right side (60.9%). VN subjects with vascular risk factors also had a higher VAH accordance rate (81%) than those without (25%). CONCLUSIONS: VAH may serve as a regional haemodynamic negative contributor and impede blood supply to the ipsilateral vestibular labyrinth, contributing to the development of VN, which could be enhanced by atherosclerotic risk factors and the left-sided location.

Healthy-side dominance of middle- and long-latency neuromagnetic fields in idiopathic sudden sensorineural hearing loss.

Any lesion along the neural axis may induce a subsequent functional reorganization at the level above. The present study used magnetoencephalography to investigate auditory-evoked magnetic fields [a component of the middle-latency auditory evoked fields peaking at approximately 50 ms (P50m) and a component of the long-latency auditory evoked fields peaking at approximately 100 ms (N100m)] on stimulation of both healthy and affected ears in patients with acute unilateral idiopathic sudden sensorineural hearing loss (ISSNHL) of moderate degree in order to elucidate the functional plasticity of the auditory system. Sixteen right-handed, previously untreated adult patients with acute unilateral left (n = 8) or right (n = 8) ISSNHL of moderate degree were studied. Sixteen right-handed healthy volunteers with normal hearing served as control. Auditory neuromagnetic responses, measured by a whole-head 306-channel neuromagnetometer, were detected by monaural tone stimulation applied to affected and healthy ears, respectively, in different sessions. Intragroup and intergroup interhemispheric differences of peak dipole strengths and latencies of P50m and N100m, respectively, to monaural tones were evaluated. Healthy-side amplitude dominance of both P50m and N100m was found in ISSNHL, i.e. contralateral dominance was preserved on affected-ear stimulation but ipsilateral dominance was seen on healthy-ear stimulation. The phenomena could be attributed to the combined contralateral attenuation and ipsilateral enhancement of P50m and N100m activity in response to healthy-ear stimulation. Our findings confirmed that functional modulation can occur within the first few tens of milliseconds of evoked response at the auditory cortex in ISSNHL. The mechanisms of healthy-side dominance might be ascribed to a functional retune of auditory pathways, i.e. conjoined contralateral inhibition and ipsilateral excitation of the auditory pathway in response to healthy-ear stimulation. The effect could be registered in cortical responses.

Malignant otitis externa.

BACKGROUND: Malignant otitis externa is an infrequent but severe infection of the external auditory canal, most often affecting elderly diabetic patients. Early diagnosis is necessary due to its high morbidity and mortality. METHODS: From 1990 to 1997, all patients with malignant otitis externa at the Veterans General Hospital-Taipei were reviewed retrospectively. The clinical features and the strategy of diagnosis and treatment are discussed. RESULTS: Twelve patients with an average age of 65.3 years were included. Eleven of these patients were diabetic. All had the presenting symptoms of otalgia and otorrhea at diagnosis. Bacterial cultures grew Pseudomonas aeruginosa in eight patients and methicillin-resistant Staphylococcus aureus in four patients. The mean duration of admission was 82 days. Appropriate antibiotics were given according to the results of bacterial culture and sensitivity test. 99Technetium scans and 67gallium scans were performed to evaluate the extent of involvement and monitor the effects of treatment. Eventually, four patients died due to renal failure, meningitis, pneumonia and upper gastrointestinal bleeding, respectively. CONCLUSIONS: Malignant otitis externa is a life-threatening infection arising from the external auditory canal. A high degree of suspicion for malignant otitis externa is mandatory. Vigorous local and systemic antimicrobial treatment should be initiated early in the course of the disease to achieve a satisfactory outcome. 99Technetium and 67gallium scans are important for the diagnosis and evaluation of the treatment results.

Acute necrotizing otitis media in an infant: a case report.

Acute necrotizing otitis media (ANOM), an uncommon but severe form of bacterial otitis media, frequently causes distressing sequelae if not properly diagnosed and treated. A four-month-old female infant initially became ill with intermittent fever, followed by left facial nerve paralysis and left otorrhea four days later. Microscopic examination of the left ear revealed congestion and swelling of the external ear canal, perforation of the eardrum and erosions on the malleus. Culture of pus from the otic lesion grew Pseudomonas aeruginosa. The patient's condition did not improve despite systemic administration of antibiotics; thus, surgical intervention was arranged. During the operation, near-total perforation of the eardrum, a dislodged incus, cholesteatoma-like matrix around the stapes, and granulation tissue occupying the middle ear and mastoid cavities were noted. Radical mastoidectomy was conducted and pathologic examination of the surgical specimen disclosed necrotic changes in both soft and bony tissues. The patient recovered soon after surgery. Her fever subsided one day after surgery and the patient was discharged in a stable condition 12 days later. However, she still had left facial nerve paralysis six months later.

Effects of acute brainstem compression on auditory brainstem response in the guinea pig.

BACKGROUND: The purpose of this study was to establish the norm for parameters of auditory brainstem response (ABR) in the guinea pig and to investigate if acute brainstem compression results in significant changes to these parameters. METHODS: Thirty-six guinea pigs with positive Preyer's reflex were anesthetized. A craniectomy was performed to remove the right occipital bone and the dura mater was opened to expose the brain, cerebellum and cerebellopontine angle (CPA). A small inflatable balloon was placed into the CPA precisely and slowly. ABR was recorded before incision of the skin as a baseline value, after placement and after inflation of the balloon with water at 0.1-ml intervals. RESULTS: Five stable peaks were recorded in 27 experimental animals. When the balloon was inflated with 0.1 ml water, the absolute latency (AL) of peaks IV and V and the interpeak latency (IPL) of peaks III and IV, and IV and V were prolonged. The amplitude ratios (AR) of peaks II, III, IV and V to peak I decreased. Inflation of the balloon with 0.2 ml of water caused further elongation of ALs of peaks IV and V and decreases in each AR. When the balloon volume increased to 0.3 ml, peak V became unrecognizable and peaks III and IV showed significant elongation of AL; peaks I and II did not show significant change in ALs. Further increase of the balloon volume to 0.4 ml resulted in disappearance of peaks III, IV and V; AL of peak II was also elongated. However, the amplitude and AL of peak I remained unchanged. Similar changes were observed in IPLs. CONCLUSIONS: This study establishes the norm of parameters of ABR in guinea pigs and demonstrates that acute brainstem compression causes elongation of ALs and IPLs of peaks II, III, IV and V. This suggests that peaks II, III, IV and V come from the brainstem and that peak I is not generated from the brainstem in the guinea pig.

Infant hearing screening with an automated auditory brainstem response screener and the auditory brainstem response.

From 1653 babies hospitalized in the Veterans General Hospital-Taipei from 1993 to 1995, 260 infants at risk of hearing impairment were selected. The risk criteria of hearing impairment for neonates were based on the recommendation of the US Joint Committee on Infant Hearing, 1990 Position Statement. All these infants were screened with the Algo-1 Plus, an automated auditory brainstem response (ABR) screener at a mean postconceptional age of 40.7 +/- 4.5 weeks. Thirty-nine cases (39/260, 15%) involving 57 ears (57/520, 11%), failed the screening. Except for one infant who died, the babies had an ABR test for both air- and bone-conducted stimuli and an otological examination. The case-specific incidence of conductive hearing deficit at the initial ABR test was 5.4%. The prevalence of sensorineural hearing deficits was between 2.3% confirmed and 3.1% including infants who did not have follow-up tests. The kappa-value that indicated agreement between the Algo-1 and ABR results was 0.64, and the overall efficiency of using Algo-1 to correctly identify pass or failure of the ABR was 83%.

[Function endoscopic sinus surgery in children].

Sinusitis is commonly seen in children. There is evidence that both acute and chronic sinusitis in children is a dynamic, multifactorial disease. Generally most patients will be cured by medical treatment. Surgery is indicated when medical treatment fails. Functional endoscopic sinus surgery (FESS), the procedure of ostiomeatal reconstruction, had become a popular surgical treatment for sinus diseases in the world. We collected 22 children with chronic sinusitis who received FESS between June, 1990 and September, 1991. The children's age ranged from 6 to 16 years. Postoperative follow-up was from 3 to 18 months. All patients tolerated the procedure well, and there were no major complications. Synechia between the middle turbinate and lateral nasal wall occurred in 47% children. Fair results were obtained in 86% patients. Well-trained functional endoscopic sinus surgery is a safe procedure and benefits in treatment of pediatric sinusitis.