Journal Club: Pressure-sensor used to monitor pressure in the cochlea model

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Today's journal article

Kim R, Schürmann M, Scholtz LU, Todt I. Evaluation of Intracochlear Pressure and Fluid Distribution in 3D-Printed Artificial Cochlear Models and Human Petrous Bones. 

Why I picked this article

Our hearing organ, the cochlea, is a tiny spiral-shaped organ filled with inner ear fluid. The sound = vibration of the air oscillates the eardrum and the middle-ear bones, and eventually reaches the inner ear fluid. The inner ear has developed a highly sensitive system to detect very small oscillations of the inner ear fluid. 

Small changes in the pressure inside the cochlea can impact the delicate and sensitive inner ear space. At the same time, the pressure and fluid movement inside the inner ear is also very challenging to study, especially in the human or large animal ear. This research developed a model based on a human cochlea to study the pressure inside the cochlea in the context of the cochlear implantation approach. 

Some of the research findings

  • Linear Model: 
    • 3D-printed (MJP2500 Plus printer, 3D systems, USA) 
    • Material - VisiJet M2R-Clear 
    • Uncoiled cochlea 3 cm in length, with volume of 100 mm3. 
  • Coiled Model: 
    • Full-scale model with 87 mm3 volume. 
    • 3D System SLA 750 3D printer 
    • Accura 60 Clear (3D systems, USA) - acrylic resin
    • Has wholes to accommodate pressure sensors. 
  • Catheter: silicone-based device designed by MED-EL for delivering therapies. 
  • Pressure sensor: 
    • microoptical pressure sensor (FOP M200, FISO, Cuebec, Canada). 
    • Recording via Evolution software (FISO, Quebec, Canada). 
  • Human petrous bone was used as tissue analogue. 
  • Dye: 1% methyleye blue-stained saline
  • Distribution ratio (distance reached / total distance)
Findings: 

Uncoiled scala tympani model
  • At 0.2 mL/h with a second hole (n = 5), perfusion improved versus no second hole but did not reach full distribution (distribution ratio 0.54 vs 0.31).
  • At 0.4 mL/h with a second hole (n = 3), the test fluid reached a saturation-level distribution; the improvement was statistically significant as early as 8 min from injection start (Figure 5A).

Cochlear model

  • With a second hole (n = 4), complete distribution was achieved at both flow rates tested; time to full perfusion was 8.5 min at 0.4 mL/h and 12.5 min at 0.2 mL/h.
  • Without a second hole (n = 4), distribution remained limited, perfusing <30% of the cochlear volume across conditions (Figure 5B).

Intracochlear pressure — cochlear model

  • With a second hole, intracochlear pressure stayed low and stable, approximately 0 mmHg across the recording window.
  • Without a second hole, pressure rose progressively over time.
  • At 0.4 mL/h with a second hole, pressures were lower and more stable than the 0.2 mL/h traces (colors in Figure 6: red = without second hole, green = with second hole; p < 0.05).

Intracochlear pressure — human petrous bone

  • At 0.4 mL/h (n = 3), pressure increased over time in both configurations, but fluctuations were smaller with a second hole (1.0 mmHg) than without (2.20 mmHg) (p < 0.05).Figure 4B. The spiral mode. Kim et al. (2025). 

Haruna's takeaway

This was interesting for me, as we have been trying to develop a model for a while. Material is quite important, and it is helpful to check out other people's publications. One option to add to our "to make" list!!

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This is Haruna's 76/100 of the 100-day challenge to post a science blog article every day! I love inner ear biology & cochlear physiology.