Analysis of a cohort of children with sensory hearing loss using the SCALEsystematic nomenclature

Objectives: What characteristics identify clinical types of childhood deafn ess? Which aspects of the otological evaluation best delineate them? To app roach these related questions, a classification for deafness consistent wit h current medical concepts was constructed using a systematic nomenclature and then applied to a pediatric cohort of 168 children with sensorineural h earing loss (SNHL) who were referred for private consultation. A major aim of the analysis was to test the utility of SCALE, the new systematic nomenc lature. Methods: Patients with SNHL were identified through the office reco rds of a single faculty member of the Department of Otolaryngology in a med ical school situated in a major US city. inclusion criteria required bone c onduction thresholds above 30 dB or equivalent in at least one of the frequ encies from 250 Hz to 4 kHz on either behavioral audiogram or on electrophy siological testing. All identified patients had initial visits during an 8- year period from late 1990 to early 1999. Patients were excluded if age at first consultation was 19 years or more, if records were insufficient to co nfirm SNHL, or if further evaluation revealed that SNHL had been misdiagnos ed. A formal nomenclature was designed to systematically encode clinical fe atures with simple descriptive terms according to an acronym (SCALE [sidedn ess, component function, age of onset, lesion, and etiology]) for all inclu ded patients. Results: One hundred sixty-eight study patients were analyzed ; sensory hearing loss was bilateral in 82% (137/168) and unilateral in 18% (31/168). The etiology of this impairment was determined to be intrinsic i n 40% of children (67/168), either secondary to genotype (57/67), or to nam ed congenital syndromes without known extrinsic cause (10/67). Recessive si ngle gene mutations diagnosed by family history, recognition of syndrome, o r determination of homozygous 35delG mutations in the gap junction protein gene, Connexin 26, accounted for bilateral sensory hearing loss in 33 child ren (24% of all bilateral cases), One girl had an X-linked dominant syndrom e (Coffin-Lowry syndrome) with auditory brainstem response-documented child hood onset of SNHL. Nine patients (5%) had chromosomal aneuploidy, and 12 p atients (7%) had either a family history of dominant deafness (7/ 12) or a recognizable autosomal dominant syndrome (5/12), most commonly, Waardenburg syndrome type 1 (4/5). Extrinsic causes of deafness were identified in onl y 13% of children (21/168) and included a relatively large number of referr als fp om neurosurgery (9/21). Three of these children had chronic middle e ar disease and sensory hearing loss associated with inflammatory and bony c hanges on temporal bone imaging suggestive of chronic osteitis; all had a h istory of active otitis media during cranial irradiation Congenital cytomeg alovirus infections were documented in only 4 cases, but 41 patients could have had this as a cause or did not have this cause ruled out. An idiopathi c cause or origin was assigned to 36% of patients (61/168) including patien ts with unnamed syndromic patterns of multiple anomalies. Conclusions: The SCALE nomenclature facilitated complete descriptions of hearing-impaired ch ildren and provided a classification scheme applicable to broad categories of human disease. The single most useful diagnostic test was screening for Cx26 mutations. Computed tomography scan of the temporal bones was helpful in establishing etiology for selected patients and invaluable in patients w ith chronic ear disease. Magnetic resonance imaging scan was a superior dia gnostic modality in one child with a posterior fossa arachnoid cyst.