Discussion:
The effect of DM on NOE is not clearly understood. One may intuitively
speculate that glycemic control prior and during admission is of
paramount importance in the treatment of NOE. However,is this in fact
true? Is an uncontrolled patient more likely to be infected with a
certain pathogen or is he at a greater risk for a worse outcome? Perhaps
the main reason for not having a validated answer is the relative rarity
of the disease and the small case series published from different
centers, during the last few decades. Our group previously reported on
83 ears in 81 patients with NOE3. We found that
duration of complaints prior to admission and the presence of aural
discharge were associated with longer hospitalization length.
Additionally, advanced age was associated with conservative treatment
failure and the need for surgery. In this research, we have slightly
enlarged the study group, and focused on the effects of DM and glycemic
control on NOE progression, using the same end-point parameters- length
of admission and the need for surgery.To the best of our knowledge this
study represents the largest and most detailed research evaluating the
relationship between DM and NOE.
The diagnosis of NOE is still not in complete agreement and there are
more than 20classification systems4reported in the
literature. In our institute we diagnosed NOEbased on the Friedman and
Cohen criteria9, which uses obligatory and
occasionalclinical parameters. Although not all patients exhibited all
the required parameters at admission, repeated physical examination
during hospitalization revealed all obligatory criteria’s, confirming
the diagnosis of NOE.
Similar tothe findings in previous studies, our patients with NOE were
mostly elderly and 93.2% of themwere known diabetics. Also in agreement
with the literature, otalgia and aural discharge were the most common
complaints at admission, and edema of the external ear canal and
granulation tissue were the most common clinical findings at admission.
PA is considered the most common pathogen in NOE. Despite that, there
have been numerous publications indicating a shift in the incidence of
the offending pathogen and an increase in the rate of fungal NOE and
sterile NOE3,4. In the current study PA-NOE was the
most common pathogen (45.0%), followed by sterile culture (20.8%) and
fungal-NOE (15.3%). When comparing these results with previously
reported data,we have observed a continuing decline in PA-NOE and an
increased in fungal-NOE3.
Our understanding in regards to the effects of DM on NOE progression is
not clear, however several key elements in the pathophysiology and
treatment of NOE share resemblance to diabetic foot11,
which is caused due to DM related peripheral vascular pathology.
Initially, both NOE and diabetic foot occur as a result of direct spread
of soft tissue inflammation into the bone, causing local osteomyelitis.
Second, in both entities PA is a leading pathogen in the inflammatory
process. Last, treatment protocol is similar and comprised of long term
antibiotic treatment and surgery in selected cases. These similarities
support previous assumptions that microangiopathies are probably the
main pathology leading to NOE among DM patients7,11.
If this is the case, it is reasonable to assume that DM duration and
severity effects NOE progression.
There are limited studied on the relationship between DM and NOE, using
different parameters to assess both DM severity, and NOE progression.
Joshua et al6found that NOE patients that exhibited
all obligatory parameters by the Friedman and Cohen criteria, had a
higher incidence of DM, higher use of oral antidiabetic medications, and
higher incidence of DM related complications in comparison to NOE
patients that did not show all obligatory parameters. Duration of
diabetes prior to admission, HbA1c levels and microalbuminuria however,
were not evaluated. Stern-Shavitet al12reported on
patients from the same center and found that DM correlated and predicted
disease specific mortality, however DM duration and severity were not
analyzed. Leeet al.13reported that DM duration was
associated with uncontrolled NOE, but HbA1c was not associated with NOE
progression. Similarly, Lohet al.7reported that DM
severity, defined by HbA1c >7.0% was not associated with
the disease outcome. Our study focused on DM severity by analyzing three
parameters – DM duration, HbA1c levels and microalbuminuria, which is
commonly used to assess renal dysfunction as a result of long lasting
vascular pathology.
In contrast to previous studies our results found that HbA1c levels were
associated with a longer hospitalization duration among NOE patients
(p=.027). DM duration and microalbuminuriadid not correlate with need
for surgery and duration of hospitalization. This might indicate that
diabetic control at the time of disease onset plays a more substantial
role in the insemination of bacteria into the surrounding bone, in
comparison to overall DM duration, thus leading to a severe disease
requiring longer in hospital treatment.
Apart from DM severity, the importance of glycemic control during
hospitalization was also reported by several publications. Carfrae et
al.14 reported that strict glycemic control is an
essential principle in NOE treatment. Similarly,
Hollies5 reported that tight glycemic control is one
of the key management strategies for the treatment of NOE. In contrast,
Chen et al.15reported that average glycemic levels
among NOE patients were not associated with mortality in NOE patients.
Also, Lee et al.13 reported that mean glucose levels
were not statistically significant between controlled and uncontrolled
NOE. In the presented study, mean glycemic levels during hospitalization
were associated with DM duration (p=.005) and HbA1C levels (p-value
0.001), but were not associated with hospitalization duration or need
for surgery. This may show that strict glycemic control during
hospitalization is not as important as previously mentioned in the
treatment and outcome of NOE patients.
Interestingly, higher glycemic levels during hospitalization were
associated with PA-NOE (p=.045). This might be explained by the fact
that DM is known to cause a dysfunction in the phagocytotic activity of
polymonuclear cells and macrophages leading to increased sensitivity of
PA infection16, 17.The possible relevance of this
finding might be important in sterile NOE. In such patients, poor
glycemic control during hospitalization can support the continuing use
of anti-PA antibiotics