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Younger Patients Have a Higher Rate of Recovery of Taste Function After Middle Ear Surgery
Mieko Sone, MD;
Masafumi Sakagami, MD, PhD;
Kojiro Tsuji, MD;
Yasuo Mishiro, MD
Arch Otolaryngol Head Neck Surg. 2001;127:967-969.
ABSTRACT
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Background Although the chorda tympani nerve (CTN) is frequently damaged during
tympanoplasty, little attention has been given to the patients' symptoms and
taste function.
Objective To investigate patients' symptoms and the functional recovery of taste
after surgery using electrogustometry (EGM).
Design Prospective study.
Patients Analysis of 163 ears of 156 patients who underwent middle ear surgery
from April 1997 through December 1999. There were 18 ears with noninflammatory
diseases, 80 with chronic otitis media, and 65 with cholesteatoma. The patients'
taste functions were examined 2 days before surgery and 2 weeks and 6 months
after surgery.
Main Outcome Measures The taste disturbance before and after middle ear surgery and the relationship
between age and the recovery rate of CTN function.
Results Two weeks after surgery, the mean EGM threshold was elevated in all
groups regardless of preservation or section of the CTN. Numbness in the tongue
and taste disturbance were more frequently found in patients with preservation
of CTN than in those with section of the CTN (P =
.008 and P = .001, respectively). In patients with
preservation of the CTN, 6 months after surgery, the recovery rate of EGM
threshold was 83% in those aged 20 years or younger (P
= .008 compared with the 2 older groups), 53% in the those aged 21 to 40 years,
and 44% in those aged 41 to 60 years.
Conclusion Age is an important factor for recovery of taste function after middle
ear surgery, which is useful information when explaining complications to
patients.
INTRODUCTION
THE CHORDA tympani nerve (CTN) controls taste in the anterior two thirds
of the tongue on each side; it runs close to the annulus of the tympanic membrane,
crossing the tympanic cavity between the incus and the malleus. The CTN is
initially encountered at this location when elevating the annulus, and it
is frequently damaged by traction, stretching, and cutting during surgical
procedures.
Because many surgeons consider hearing improvement to be the most important
postoperative result, taste disturbance has rarely been focused on in the
last 4 decades, and, if reported, the results have not been clarified. Moon
and Pullen1 reported that 67 (28%) of 242 patients
with otosclerosis complained of taste disturbance 6 months after stapes surgery.
Dawes2 reported a similar complaint from 38
(26%) of 145 patients who underwent surgery for chronic otitis media. Other
studies have shown that cutting or preserving the CTN made little difference
in symptoms3-4 and signs.5 However, our otologists have often encountered patients
complaining of numbness in their tongue and taste disturbance after surgery,
even though the otologists were unfamiliar with the issues concerning functional
recovery of CTN after surgery.
We examined the changes of CTN function before and after the middle
ear surgery using electrogustometry (EGM)6-7
and analyzed the relationship between the patient's age and the recovery rate
of CTN function.
PATIENTS AND METHODS
One hundred sixty-three ears of 156 patients with middle ear diseases
were examined 2 days before surgery and 2 weeks and 6 months after surgery
from April 1997 through December 1999. Subjects with previous ear operations
were not included. Subjects consisted of 77 males and 79 females with ages
ranging from 5 to 60 years (mean, 40.4 years). Patients older than 60 years
were excluded because taste function naturally deteriorates with aging.8-10 Electrogustometry was
performed according to the method of Tomita et al.7
The stimulation range of EGM threshold was –8 to 34 dB (normal range,
<8 dB). Cases that were not measured by electrogustometry were statistically
analyzed as 36 dB. The point measured with EGM was the ridge 2 cm behind the
tip of the tongue. Electrogustometry was measured by only one physician (M.S.)
who was skillful in the procedure.
After the patient's consent and permission were obtained, symptoms such
as tongue numbness and taste disturbance were investigated by only one physician
(M.S.) during the first 2 postoperative weeks.
The middle ear diseases were classified into noninflammatory diseases
such as posttraumatic perforation and otosclerosis (18 ears), chronic otitis
media (80 ears), and cholesteatoma (65 ears). Patients with no response to
EGM bilaterally and those with bilateral section of the CTN were excluded.
The statistical analysis of postoperative symptoms was performed using
the  2 test, and the relationship between the recovery rate
and age was evaluated using the Jonckheere-Terpstra trend test.
RESULTS
Before surgery, the mean ± SD EGM threshold was 4.2 ±
9.4 dB in the noninflammatory group, 10.6 ± 13.5 dB in the chronic
otitis media group, and 10.3 ± 12.6 dB in the cholesteatoma group (Figure 1). No patients complained of taste
disturbance except for one patient who had facial palsy.
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Figure 1. Mean ± SD electrogustometry
(EGM) thresholds for all subjects (n = 163) 2 days before surgery and 2 weeks
after surgery (normal range,  8 dB). CTN indicates chorda tympani nerve.
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Two weeks after surgery, the EGM threshold was elevated regardless of
preservation or section of the CTN in all groups: 24.7 ± 13.5 dB and
29.0 ± 9.2 dB in the noninflammatory group, 16.8 ± 14.4 dB and
35.0 ± 2.0 dB in the chronic otitis media group, 22.8 ± 14.3
dB, and 30.3 ± 11.0 dB in the cholesteatoma group for those with preservation
and section of the CTN, respectively (Figure
1). We asked about the presence of symptoms in 104 cases; the other
52 patients did not report clear symptoms. Taste disturbance occurred in 37
(55%) of 67 cases with preservation and in 8 (22%) of 37 cases with section.
Numbness in the tongue occurred in 28 (42%) and 6 (16%) cases, respectively
(Table 1). The patients with preservation
of the CTN had a significantly higher rate of symptoms than the patients with
section (P = .001 for taste disturbance; P = .008 for numbness; 2 test).
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Table 1. Symptoms of Patients With Preservation or Section of the Chorda
Tympani Nerve (CTN)
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Among the preservation patients, we selected those with a normal EGM
threshold before surgery and compared the EGM thresholds at 2 weeks and 6
months after surgery. Those aged 0 to 20 years had a higher rate of cholesteatoma
and a lower rate of noninflammatory disease than the other groups (Table 2). The recovery rate of EGM threshold
was higher at 6 months than at 2 weeks in all 3 groups. Six months after surgery,
the rate of complete recovery was 83% in those aged 0 to 20 years, 53% in
those aged 21 to 40 years, and 44% in those aged 41 to 60 years (Figure 2). The youngest group had a significantly
higher recovery rate of EGM threshold than the older groups (P = .008 for all, Jonckheere-Terpstra trend test).
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Table 2. Middle Ear Disease by Age in Patients With Preservation of
the Chorda Tympani Nerve and a Normal Electrogustometry Threshold Before Surgery
(n = 60)
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Figure 2. Rate of recovery of electrogustometry
thresholds by age group 2 weeks and 6 months after surgery. The youngest group
had a significantly higher rate of recovery than the older 2 groups (P = .008). No recovery indicates that the threshold level did not improve
or deteriorated; incomplete recovery, the threshold level improved but did
not reach the normal range (8 dB); and complete recovery, the threshold
level improved to within the normal range.
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COMMENT
Based on the results of orthopedic studies, it is well known that peripheral
motor and sensory nerves recover better and faster in children than in adults,
especially the digital, median, ulnar, and radial nerves.11
In the cranial nerves, the rate of recovery from idiopathic facial palsy decreased
from 83% for subjects in their 20s to 54% for subjects in their 80s.12 This study was concerned with the recovery of movement
in the extremities and the functional recovery of the sense of touch. However,
little attention has been paid to the correlation between age and the recovery
of special senses such as taste and olfaction, because most physicians do
not know when these nerves are injured or how to measure the recovery rate.
Fortunately, at our institution, our otologists have many chances to handle
the CTN during tympanoplasty and to know how to measure CTN function.
Patients older than 60 years were omitted because taste function deteriorates
with age and the threshold is elevated in elderly persons.8-10
In fact, 35 chronic otitis media patients between 61 and 70 years old were
operated on during the same period as this trial, and they had a mean ±
SD EGM threshold of 12.5 ± 11.8 dB on the healthy side and 18.5 ±
13.5 dB on the diseased side. The rate of abnormal EGM values ( 10 dB)
was 60% (21/35) on the healthy side. Thus, it is difficult to evaluate the
damage and recovery of CTN function in elderly patients.
The EGM findings before surgery showed that chronic inflammation elevated
the taste threshold to a little higher than the normal level, which meant
impaired CTN function, as shown in a previous study.13
However, no patients except for one with facial palsy complained of taste
disturbance. It is possible that damage to CTN function occurred gradually
as a result of chronic inflammation. In addition, most patients had unilateral
lesions, and in the 7 patients with bilateral lesions, the second ear was
operated on after the functional recovery of CTN in the first ear.
Although the EGM threshold 2 weeks after surgery was elevated in all
groups regardless of the preservation or section of the CTN, the incidence
of numbness or taste disturbance was significantly higher in the patients
with preservation than in those with section. It is possible that injury of
the CTN by traction or stretching produced abnormal stimulation that was transduced
to the peripheral organ, but this has not been established. Furthermore, since
most of the symptoms ceased by 6 months after surgery, numbness in the tongue
and taste disturbance were not serious problems.
Younger patients had a significantly higher recovery rate of CTN function
consistent with the rate of recovery of function of peripheral nerves11 and the facial nerve.12
The types of diseases were different among the 3 groups; ie, those in
the youngest group had a higher percentage of cholesteatoma and a lower percentage
of noninflammatory disease than those in the 2 older groups. Patients in all
3 groups had normal EGM thresholds before surgery, and, in general, more effort
is required to preserve CTN function in patients with cholesteatoma than in
patients with noninflammatory disease and chronic otitis media. Therefore,
we believe that the present finding of recovery of CTN function is a result
of the high regenerative nerve ability in young patients.
Because previous studies disregarded the patients' age,1-5
it has been controversial whether or not CTN function recovers after preservation
of the CTN. The present study helps resolve this issue and helps explain the
potential complications of surgery.
Preservation of the CTN was more important in the bilateral cases, because
loss of CTN function on both sides meant loss of taste in the anterior two
thirds of the tongue and impaired the patients' quality of life.1
In the present study, preservation of the CTN led to a functional recovery
in more than 80% of the young patients and more than 50% of the middle-aged
and older patients; thus, in bilateral cases, we recommend that surgeons attempt
to preserve the CTN in the operation on the first ear.
AUTHOR INFORMATION
Accepted for publication March 17, 2001.
This work was presented in part at the Fourth European Congress of Oto-Rhino-Laryngology,
Head and Neck Surgery, Berlin, Germany, May 16, 2000.
Corresponding author and reprints: Masafumi Sakagami, MD, PhD, Department
of Otolaryngology, Hyogo College of Medicine, Mukogawa, Nishinomiya, Hyogo
553-8501, Japan (e-mail: msakaga{at}hyo-med.ac.jp).
From the Department of Otolaryngology, Hyogo College of Medicine, Hyogo,
Japan (Drs Sone, Sakagami, and Tsuji); and the Department of Otolaryngology,
Osaka University Medical School, Osaka, Japan (Dr Mishiro).
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