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Biomedical subjects

H Lamm

Publications and source records attributed to H Lamm.

28 records · Page 2Linked to original sources
PubMedDate not supplied

Instrumental perforation of the round window. Animal experiments using cochleography and ERA.

The round window membrane of the inner ear of the guinea pig was perforated under Ketanest anaesthesia. A very rapid and almost total loss of cochlear microphonics, auditory nerve action potential and brain-stem response developed. Replacement of the perilymph with Ringer's solution and surgical closure of the membrane damage had no effect on auditory nerve action potential or brain-stem response. Further decline in the amplitude of cochlear microphonics was halted, however. When perfusion of the round window membrane was carried out whilst the bulla was full with Ringer's solution, no essential decline was seen in the amplitudes of microphonics and auditory nerve action. Only brain-stem response was reduced--temporarily by 40% of the original amplitudinal level--but this showed subsequent recovery. Preservation of cochlear microphonics and auditory nerve action after perforation in Ringer's solution, i.e. excluding air, indicates that air entering the scala tympani is the cause of the sudden hearing loss after round window perforation. Using a simple physical model, an attempt is made to demonstrate this process. The anatomic connections between the round window, cochlear aqueduct and scala tympani are discussed, as are the different ways in which the round window membrane can be perforated.

Action Potentials↗
PubMedDate not supplied

Long-term study after perforation of the round window. Animal experiments using electric response audiometry.

The round-window membrane of the inner ear of the guinea pig was perforated with a platinum wire under ketamine-xylazine anaesthesia. The latency times of waves I and V (Jewett) increased to 0.6 ms at 100 dB click HL stimulus loudness. The interpeak latencies did not change (4.0-4.2 ms). At 60 dB CHL stimulus loudness, no responses were discernible. Closure of the membrane damage by adhesive fibrin tissue had no effect on the auditory nerve potentials or the brain-stem responses. Normal latency times of waves I-V were seen 7 days after perforation. There was no difference between the animals with repaired and unrepaired membrane damage. We observed spontaneous healing of the round-window membrane 7 days after perforation, and a normal organ of Corti.

Acoustic Stimulation↗