Superior aspect of the globe (SAG) rising characteristics describe a specific pattern in air‑bone gaps across speech frequencies that widens at higher frequencies, often reflecting conductive or mixed hearing loss with cochlear sparing. This evergreen explainer defines SAG configuration, outlines common causes such as otosclerosis, ossicular discontinuity, and chronic otitis media, and clarifies how to interpret SAG findings in clinical audiology. You will find practical context for pure‑tone and speech testing, differential diagnosis guidance, and implications for management, enabling more consistent identification and follow‑up of SAG patterns over time.
What Is a SAG Rising Configuration
A SAG rising configuration appears when air‑bone gaps increase across higher frequencies while bone‑conduction thresholds remain relatively flat or improve at low frequencies. Clinicians typically observe this pattern when speech frequencies (500–2000 Hz) show minimal air‑bone separation, but separation grows at 3000–8000 Hz. The term rising refers to the increasing magnitude of the gap as frequency rises, not to overall threshold elevation. This pattern is identified on an audiogram by plotting air and bone thresholds across speech and high‑frequency regions and noting the progressive divergence between the two curves. SAG configurations are most relevant in differential diagnosis of conductive, sensorineural, and mixed hearing loss.
Common Etiologies and Underlying Mechanisms
SAG configurations commonly arise from conditions that impede sound transmission in the middle ear while preserving cochlear function. Otosclerosis, particularly fixing the stapes at the oval window, often produces a pronounced SAG because low‑frequency bone conduction improves through bone‑skull resonance, whereas high‑frequency air conduction remains limited. Ossicular discontinuity, whether congenital, traumatic, or postsurgical, can yield a similar pattern by reducing middle‑ear leverage, especially at higher frequencies. Chronic otitis media with tympanic membrane perforation and ossicular erosion may also create a rising gap, particularly when granulation tissue or fibrosis further restricts mobility. Because cochlear function remains largely intact in these conditions, the SAG reflects conductive or mixed pathology rather than pure sensorineural loss.
Otosclerosis
Otosclerosis typically presents with bilateral, slowly progressive conductive or mixed hearing loss. Carhart notch at 2000 Hz is common but does not preclude a SAG pattern; the progressive air‑bone gap at higher frequencies can still be identifiable. The fixation of the ossicular chain limits high‑frequency airborne transmission while bone‑conduction thresholds may show subtle improvement at low frequencies due to inertial bone conduction mechanisms.
Ossicular Discontinuity
Disruption of the ossicular chain, from congenital anomalies to traumatic fractures, removes normal lever mechanics and impedance matching. High‑frequency airborne signals are disproportionately affected, widening the air‑bone gap as frequency increases. Bone conduction remains relatively preserved, producing a classic SAG configuration on audiometry.
Chronic Otitis Media
Chronic inflammation, tympanic membrane retraction, and ossicular erosion can gradually degrade middle‑ear transmission. The resulting audiogram often shows a SAG pattern, with more pronounced gaps at higher frequencies and variable conductive contributions at lower frequencies.
Clinical Assessment and Test Protocol
Consistent identification of a SAG rising characteristic requires a standardized protocol. Begin with otoscopy to rule out cerumen, foreign body, or tympanic membrane abnormality that could artificially elevate air conduction thresholds. Perform pure‑tone audiometry with both air and bone conduction across frequencies from 250 Hz to at least 8000 Hz. Verify air‑conduction thresholds using masked bone conduction when sensorineural loss coexists. Obtain speech‑threshold and word‑recognition scores at frequencies that highlight the rising separation. Record tympanometry and acoustic reflexes to further localize conductive versus cochlear components. When conductive or mixed loss is suspected, consider imaging or specialist referral to clarify the etiology.
Best Practices for Reliable Identification
- Use calibrated equipment and repeat thresholds to minimize measurement error.
- Ensure adequate masking to prevent cross‑hearing, which can obscure the true air‑bone gap.
- Include high‑frequency testing (up to 8–12 kHz) to capture the progressive gap that defines SAG.
- Correlate audiometric findings with immittance data and speech tests for convergent validity.
Interpretation and Differential Diagnosis
When you observe a SAG configuration, first confirm that the pattern is not an artifact from improper masking, patient movement, or equipment malfunction. If genuine, consider conductive and mixed causes before attributing the pattern to cochlear dysfunction. In mixed hearing loss, both conductive and retrocochlear components may coexist; the SAG reflects the conductive portion, while speech discrimination scores may reveal additional sensorineural deficit. Retrocochlear pathology typically shows symmetric air‑bone gaps with relatively flat bone‑conduction thresholds and reduced speech discrimination disproportionate to thresholds, which can help differentiate it from purely conductive SAG patterns. Central auditory disorders rarely produce a true SAG rising characteristic, making peripheral conductive or mixed loss the primary diagnostic consideration.
Prognosis, Management, and Follow‑Up
Management of SAG configurations depends on etiology and severity. Otosclerosis may be monitored medically or addressed with stapedectomy or hearing amplification. Ossicular discontinuity often benefits from ossiculoplasty or hearing aids that overcome loss of middle‑ear leverage. Chronic suppurative otitis media requires control of infection, tympanic membrane repair when indicated, and amplification as needed. Hearing aids with appropriate gain and frequency shaping can compensate for the air‑bone gap, particularly when high‑frequency signals are affected. For candidates for surgical or procedural intervention, high‑resolution temporal bone imaging and thorough preoperative counseling are recommended. Long‑term follow‑up with repeat audiometry helps track progression, adjust amplification, and evaluate surgical outcomes when applicable.
Practical Summary and Key Points
| Attribute | Verified Detail | Source Context |
|---|---|---|
| Frequency Range | Air‑bone gap widens at 3000–8000 Hz; speech frequencies relatively preserved | Audiometric convention |
| Typical Cause | Otosclerosis, ossicular discontinuity, chronic otitis media | Clinical otology literature |
| Bone Conduction | Relatively flat or shows low‑frequency improvement (Carhart notch region) | Audiometric patterns |
| Speech Testing | Discrimination often relatively preserved unless mixed loss present | Clinical best practice |
| Next Steps | Otoscopy, immittance, imaging when indicated, referral for surgery or amplification | Standard diagnostic pathway |
- Focus testing on the 250–8000 Hz range to capture the progressive air‑bone gap.
- Rule out artifacts by repeating thresholds and confirming adequate masking.
- Correlate audiometric SAG with tympanometry and speech scores to refine diagnosis.
- Consider conductive or mixed pathologies first when a rising air‑bone gap is present.
- Plan longitudinal follow‑up to monitor stability or progression and adjust management accordingly.