Preventing internal auditory artery vasospasm using topical papaverine: an animal study.
BACKGROUND
Internal auditory artery (IAA) spasm is thought to be one of the causes of postoperative sensory hearing loss after attempted hearing preservation removal of an acoustic neuroma. The use of topical papaverine, a nonspecific vasodilator, to prevent vascular insufficiency to the inner ear and to improve hearing outcomes has been suggested but not proven.


METHODS
Vasospasm was mechanically induced by compressing the IAA in the control ears of six rabbits after application of topical saline. The subsequent reduction of cochlear blood flow (CBF) was measured using a laser-Doppler (LD) flow-monitoring technique. Functional loss of cochlear activity was verified with distortion product otoacoustic emissions (DPOAE). The contralateral experimental ears were treated with the topical application of papaverine directly to the IAA and cochleovestibular nerve complex. CBF and DPOAE were compared between the control and papaverine treated ears for 3-minute and 5-minute IAA compressions.


RESULTS
Every control ear demonstrated some degree of postcompression IAA vasospasm (i.e., reduced CBF) and reduction of DPOAE. Nearly complete recovery of CBF and DPOAE to baseline was observed in all of the papaverine treated ears.


CONCLUSIONS
An animal model of IAA vasospasm was described. Mechanically induced vasospasm of the IAA was prevented by the topical application of papaverine. These findings have clinical implications for surgical procedures involving the internal auditory canal/cerebellopontine angle such as acoustic neuroma removal.
ENT Department, Silesian Medical Academy, Zabrze, Poland.
Krzysztof
K
Morawski
Fred F
FF
Telischi
Faisal
F
Merchant
Grzegorz
G
Namyslowski
Grazyna
G
Lisowska
Brenda L
BL
Lonsbury-Martin
D000287:Administration, Topical; D000818:Animals; D002530:Cerebellopontine Angle / Q000601:surgery*; D003051:Cochlea / Q000187:drug effects; D004195:Disease Models, Animal; D017078:Laser-Doppler Flowmetry; D008279:Magnetic Resonance Imaging; D017084:Otoacoustic Emissions, Spontaneous; D010208:Papaverine / Q000627:therapeutic use*; D011183:Postoperative Complications / Q000209:etiology / Q000517:prevention & control; D011817:Rabbits; D013997:Time Factors; D014665:Vasodilator Agents / Q000627:therapeutic use*; D020301:Vasospasm, Intracranial / Q000175:diagnosis* / Q000209:etiology / Q000503:physiopathology / Q000517:prevention & control*
D014665:Vasodilator Agents; D010208:Papaverine