Negative Summating Potential in 
Meniere’s Disease - Before and After 
Treatment

Orchik,D.J., Shea,J.J. and Xianxi,G.
Shea Clinic, Memphis, Tennessee, USA

The negative summating potential 
(SP)is the essential component of 
electrocochleography (ECoG) which is 
an objective test to asses the 
presence of endolymphatic hydrops in 
Meniere’s disease in a clinic 
setting.  The purpose of the present 
study was to compare the SP in 
Meniere’s patients before and after 
various treatments as an indication 
of changes in endolymphatic hydrops 
in response to those treatments.  
Transtympanic ECoG was performed on 
88 ears of 84 Meniere’s patients 
before and after various treatments.  
Treatments included medical 
treatment in 18 ears, endolymphatic 
shunt in 12 ears, streptomycin 
perfusion of the lateral 
semicircular canal (SMPLSC) in 9 
ears, streptomycin perfusion of the 
middle ear (SMPME) in 33 ears, and 
dexamethasone perfusion of the 
middle ear (DMZME) in 16 ears.  
Overall an enlarged summating 
potential and action potential 
ration (SP:AP > 40%) was found in 
75% before treatment and 78.4% 
after.  Enlarged SP ears remained 
enlarged in 90.9% of ears.  A non-
enlarged SP before treatment became 
enlarged after treatment in 40.9%.  
In early Meniere’s disease (hearing 
< 25dB), an enlarged SP was found in 
58.3% before treatment and 79.2% 
after.  Overall, 72 of 84 patients 
(85.7%) were dizzy-free after 
treatment.  These findings indicate 
that endolymphatic hydrops, 
evidenced by an enlarged SP, tends 
to develop according to the natural 
history of Meniere’s disease.  
Endolymphatic hydrops may not be 
reversible, no matter what treatment 
is received, probably due to the 
degeneration of Reissner’s membrane.