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

What characteristics identify clinical types of childhood deafness? Which aspects of the otological evaluation best delineate them? To approach these related questions, a classification for deafness consistent with current medical concepts was constructed using a systematic nomenclature and then applied to a pediatric cohort of 168 children with sensorineural hearing loss (SNHL) who were referred for private consultation. A major aim of the analysis was to test the utility of SCALE, the new systematic nomenclature.

Patients with SNHL were identified through the office records of a single faculty member of the Department of Otolaryngology in a medical school situated in a major US city. Inclusion criteria required bone conduction thresholds above 30 dB or equivalent in at least one of the frequencies from 250 Hz to 4 kHz on either behavioral audiogram or on electrophysiological 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 confirm SNHL, or if further evaluation revealed that SNHL had been misdiagnosed. A formal nomenclature was designed to systematically encode clinical features with simple descriptive terms according to an acronym (SCALE [sidedness, component function, age of onset, lesion, and etiology]) for all included patients.

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 in 40% of children (67/168), either secondary to genotype (57/ 67), or to named congenital syndromes without known extrinsic cause (10/67). Recessive single gene mutations diagnosed by family history, recognition of syndrome, or determination of homozygous 35delG mutations in the gap junction protein gene, Connexin 26, accounted for bilateral sensory hearing loss in 33 children (24% of all bilateral cases). One girl had an X-linked dominant syndrome (Coffin-Lowry syndrome) with auditory brainstem response-documented childhood onset of SNHL. Nine patients (5%) had chromosomal aneuploidy, and 12 patients (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 only 13% of children (21/168) and included a relatively large number of referrals from neurosurgery (9/21). Three of these children had chronic middle ear disease and sensory hearing loss associated with inflammatory and bony changes on temporal bone imaging suggestive of chronic osteitis; all had a history of active otitis media during cranial irradiation. Congenital cytomegalovirus 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 idiopathic cause or origin was assigned to 36% of patients (61/168) including patients with unnamed syndromic patterns of multiple anomalies.

The SCALE nomenclature facilitated complete descriptions of hearing-impaired children 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 with chronic ear disease. Magnetic resonance imaging scan was a superior diagnostic modality in one child with a posterior fossa arachnoid cyst.