Jennifer
Rubin,
MD
#{149} Hugh
D. Curtin,
MD
Malignant External of CT in Diagnosis
Malignant external otitis is a severe bacterial infection of the bone and soft tissues of the base of the skull that is frequently difficult to diagnose. The effectiveness of antibiotic therapy is likewise difficult to assess. Serial computed tomographic (CT) scans were obtained in 11 consecutive patients with malignant external otitis at time of diagnosis and periodically after conclusion of antibiotic therapy. All patients demonstrated abnormalities of the external auditory canal, with or without bone destruction. Soft tissue or fluid in the middle ear and mastoid, around the eustachian tube, and in the parapharyngeal space (both pre- and poststyloid) was seen in greater than 50% of the cases. While remineralization of bone was not seen, soft-tissue disease improved dramatically, and recurrence or persistence could be conroborated by detection of more extensive soft-tissue changes. By delineating the extraand intracranial extent of disease, serial CT scans enable one to make the diagnosis, determine the extent of infection, document recurrence, exclude progression, and confirm resolution of malignant external otitis. Index
terms:
mation
CT,
and
Ear, infection,
214.1211
eases,
CT, 211.1211 211.20,
Mastoiditis,
Ear,
212.20
214.26
#{149}
inflam-
#{149}
#{149} Mastoid, #{149} Skull,
dis-
12.20
Radiology
1990;
174:391-394
I
From
the
Departments
D.B.K.),
(V.L.Y.), Medicine, 15261.
Radiology
M
of Pittsburgh
University 968 Received
Scaife July
ed August 9, revision accepted September quests to V.L.Y. C
RSNA,
1990
and School
Hall, Pittsburgh. 10, 1989; revision
received 12. Address
September reprint
Medicine of PA request-
11; re-
#{149} Donald
external otitis is an infection of bone and soft tissues almost always caused by Pseudomonas aeruginosa. It occurs almost exclusively in the elderly patient with diabetes mellitus. The disease is manifest by severe unrelenting otalgia, headache, and purulent otomnhea unresponsive to topical antibiotics (1,2). A markedly elevated erythrocyte sedimentation rate (ESR), granulation tissue in the extennal auditory canal, and evidence of bone destruction on computed tomography
ALIGNANT
(CT)
scans
are
important
objec-
tive data for making the diagnosis (3,4). The diagnosis is confirmed by recovery of P aeruginosa from the external canal or bone and exclusion of the presence of a malignant neoplasm. Beginning as an area of granulation tissue at the bone-cartilage junction of the
external
auditory
canal,
the
infec-
tion may progress to chondnitis and osteomyelitis extending posteriorly into the mastoid, anteriorly into the temporomandibular joint, or medially toward the petrous apex. Most commonly, however, the inflammation spreads infenionly via the fissures of Santorini to involve the soft tissues inferior to the temporal bone. The ability to delineate normal fat planes, particularly those of the area infenior to the temporal bone, makes CT an ideal tool for evaluating malignant external otitis (5). The sensitivity of CT in diagnosis and follow-up of the disease has not been established. Strashun et al reported that CT had a sensitivity of only 30% at the time of clinical presentation (6); however, their assessment was confined
to
elitis
and
not
of Otolaryngology
(H.D.C.),
L. Yu, MD
B. Kamerer,
MD
Otitis: Utility and Follow-up’
comitant potential (JR.,
#{149} Victor
permit
the
documentation
did
not
of
take
soft-tissue limitation
into
account
con-
abnormalities. of CT is that
A it does
differentiation
of
external otitis and carcinoma. two cases have been reported malignant
external
osteomy-
otitis
malignant
incided with or predated the presence of squamous cell carcinoma of the skull base (7,8). Most articles have reported that the
MATERIALS
AND
METHODS
Serial CT scans were obtained in i i consecutive patients with malignant external otitis seen at the Eye and Ear Hospital of Pittsburgh between 1986 and 88. CT was performed on a 9800 scanner (GE Medical Systems, Milwaukee) with use of intravenous contrast material. The section thickness was 1.5 mm through the temponal bones through
and skull base the nasopharynx.
and
3 mm Soft-tissue
and
bone algorithms were performed in all cases. Patients underwent an average of three examinations, including one at the time of initial presentation. Nine of the 1 1 patients (82%) were rescanned at least 8 months
after
therapy
(range,
months).
All
the
Each
study
(a) external
studies
same
head
was
suture
of antibiotic
months;
of the
mean, were
and
assessed
auditory
with or without tension beneath
crossing mastoid
completion
8-37
preted by the ogist (H.D.C.).
nadiol-
evidence
of
abnormality
bone destruction, the temporal
bone,
(b) ex(c)
(d) fluid in the (e) petrooccipital
(f) intracranial
involvement,
17.2
inter-
neck
for
canal
of the midline, or middle ear,
ex-
tension, (g) mass effect in the nasopharynx, (h) involvement of the clivus, (i) extension
into
parapharyngeal involvement, eustachian
In fact, in which
apparently
abnormalities on CT scans persist despite the obvious clinical remission of disease (4-6,9,10). However, Gold et al concluded that serial CT scans could aid in evaluating the effectiveness of therapy, given its ability to demonstrate the resolution of central soft-tissue disease (ii). We analyzed 33 sequential CT scans in 1 1 patients in an attempt to identify diagnostic features of this disease and to establish the radiologic features of both the eradication of disease as well as its persistence or recurrence.
the
pre-
and
poststyloid
space, (j) masticator and (k) disease around tube.
space
the
co-
Abbreviations: tion
ESR
erythrocyte
sedimenta-
rate.
391
Figure 1. (a) Axial section through the temporomandibular posterolateral margin of the condyle (arrow). (b) Fat planes to the temporomandibular joint have resolved. The appearance tamed at an angle different from that in a.)
RESULTS A total of 33 CT scans were obtained, with an average of three scans per patient (range, 1-5). Two patients did not undergo follow-up studies. One died of causes unrelated to malignant external otitis at 1 year after treatment. The othen had no evidence of clinical disease at 49 months after therapy, but because of hen general debilitated condition, she was unable to return for follow-up scanning. Findings at the time of diagnosis are listed in descending order of frequency in the Table. Clinical cure predated madiologic regression in all cases. Progressive resolution of soft-tissue disease (in contrast to osseous involvement) was noted at varying intervals after the completion of antibiotic therapy. One patient had severe temponomandibulan joint tenderness at presentation with extensive soft tissue in the area of the right temporomandibular joint on CT scans (Fig la). Hen joint tenderness progressively resolved, and CT scans obtained at 4 and 12 months after treatment showed progressive resolution of the inflammatory process (Fig ib). Two patients had evidence of obliter-
a.
(a) Scan
2. normal
the months
shows increased fat planes beneath the
after
therapy,
the
fat
planes
Progression
of disease
despite
antibi-
the
penitubal
therapy
fat
showed
planes
less
on
CT
obliteration
parapharyngeal
of fat in both the parapharyngeal and penitubal areas (Figs 2b, 3b). Soft tissue in the external auditory canal, with or without bone destruc-
junction
tion,
py
was
initial cessful
a near
finding
in
tissue
contour
restoration
masticator cases
of (Fig
space at
4b).
was
diagnosis
chitecture of the normal were initially inappanent cerned after treatment 392
#{149} Radiology
the
normal
Disease
noted (Fig
5a).
subtemporal
with
hyperbaric
oxygen
(Fig 3b). The patient well, with no evidence re-
softin
in
and
areas (Fig 3a). However, these findings improved after 12 weeks of tobnamycin and piperacillin administration in con-
at
CT examination (Fig 4a). Sucantibiotic therapy frequently
suited
the
universal
month around
The
midline
fat planes that could be dis(Fig Sb).
follow-up.
initially
the 27% of an-
at the
and (Section
lateral ob-
defined
biotic
the
soft tissue
tissue in the retropharyngeal area and obscuration of skull base, close to the eustachian tube (arrow). (b) At 12 immediately beneath the skull base (arrow) are better
scans obtained at the time of presentation (Figs 2a, 3a). Subsequent CT scans obtained following completion of anti-
of
shows
U.
Figure
otic therapy was also documented. One patient with persistent disease after two 6-week courses of oral therapy with ciprofloxacin and nifampin had, on CT scans, more extensive soft tissue around the eustachian tube as well as
ation
joint
abutting the condyle is now normal.
sels,
had the but
completion
veloped reelevation
with (Fig
The evidence tip
clear 6a).
One
at 24-
patient
disease
and
great
delineation
of antibiotic
recurrent of his
other of
mastoid
thera-
is currently of disease
month therapy,
yes-
of the after
fections
the he
tamed at this time showed crossing of the midline and obscuration of fat medial to the lateral pterygoid muscles (Fig 6b). We further divided our patients into two groups based on the severity of disease as defined by (a) evidence of cranial nerve palsies on examination, (b) an ESR greater than 80 mm/sec, and (c) symptoms present for 12 weeks on longer before the institution of definitive antibiotic therapy. The seven patients with more severe disease at the time of presentation had a greater number of abnormal findings (Table) on CT scans (range, 6-10; mean, 8) compared with the four patients whose in-
de-
symptoms as well as ESR. A CT scan ob-
appeared
less
2-4; mean, 3). There normal finding seen in those with severe presence of intracranial
virulent
(range,
was no single abmore frequently infection. The extension,
February
1990
however, indicated a particularly recalcitrant form of the disease, as seen in the one patient who required four courses of antibiotics in conjunction with hyperbaric oxygen treatments before clinical and bacteriologic cure could be demonstrated (Fig 7).
DISCUSSION
b. Figure ryngeal
3.
(a) Obscuration
of the normal fat planes around the eustachian tube and parapharegion (black arrow) (compare with opposite side). This image represents progression of disease compared with a previous CT scan (not shown). The torus tubarius on the normal side (white arrow) is seen posterior to the eustachian tube orifice. (b) Considerable improvement in the fat beneath the skull base is seen 15 months after the completion of antibiotic therapy. Some residual abnormality (arrow) persists in the area around the eustachian tube.
Much of the experience recounted in the literature with malignant external otitis has involved plain radiography and plunidirectional tomography. These techniques can demonstrate bone destruction, the presence of soft tissue in the external auditory canal, and increased density of the mastoid air cells, but they are inadequate for documenting infnatemponal or intracranial disease extension (5,12,13). Nuclear medicine studies, such as bone scanning with technetium-99m methylene diphosphate, have frequently been
used
to
confirm
the
clinical
di-
agnosis of malignant external otitis (6,9-ii,i3-i6). A mere 10% increase in osteogenic activity is sufficient for the detection of a lesion by means of bone scanning (6). The modality is extremely sensitive,
but
its
usefulness
is impaired
by its low specificity. Since the tracer accumulates at sites of any osteogenic activity, a “positive” scan may be seen in inflammatory disease, carcinoma, temponomandibular joint disorder, or fracture. In one study, radiologists blinded to the patients’ diagnosis were unable to differentiate scans of patients with malignant external otitis from those
with
simple
severe
external
otitis
Additionally, the bone scan memains positive despite the clinical nesolution of disease, limiting its utility in follow-up (4,6,9,13-15). (17).
a. Figure pare part
b. 4. (a) Soft with opposite of the external
tissue
(arrow)
fills
the
normally
air-filled
side). There is also more superficial ear. (b) After therapy, the external
external
soft-tissue canal is air
auditory
change filled
in the (arrow).
canal
(com-
Gallium
posterior
scanning
has
also
been
used
for evaluation because activity in malignant contrast to the minimal
of the intense external otitis in uptake of galli-
um
the
normally
seen
in
head
region.
Like Tc-99m bone scanning, Ga-67 citrate studies are characterized by low specificity and imprecision in the anatomic localization of disease. Although it has been suggested that serial gallium scans may help in predicting clinical resolution (13-15), recurrent on persistent disease has been documented in patients with normal gallium studies (9,iO,18). This is especially true in deeper lesions close to the nasopharynx and central skull base. Magnetic resonance (MR) imaging has
been
nant
used
external
limited.
Ghenini
imaging a.
Figure space planes
Volume
b.
5.
(a) Axial
(arrow) (arrow).
174
section shows obscuration (compare with opposite side).
of the normal (b) Posttreatment
tion fat planes in the masticator return of the normal fat
although sponse imaging
#{149} Number
2
in
of
is
found
extent difficult
to antibiotics alone.
malig-
experience MR
to CT in demonstra-
anatomic it was
of
but
et al (19)
superior the
evaluation
otitis,
with Further
of to
disease,
establish use
of
neMR
experience
Radiology
#{149} 393
with MR imaging evaluation is needed, including investigation of the role of gadolinium and comparison with CT. CT has been reported to be insensitive in early cases of malignant external otitis (6), although in that study diagnostic criteria were restricted to the documentation of bone changes. In our study, all i 1 patients had abnormal findings on CT scans at the time of presentation as required for inclusion into the study; thus, the utility of CT in diagnosis was not assessable. Features on the initial CT scans included nonspecific findings such as aneas of soft-tissue density in the external canal (Fig 4a) and fluid in the mastoid or middle ear (Fig 5a). More specific and ominous findings included bone erosion, obliteration of fat planes beneath the temporal bone, parapharyngeal space involvement (Fig 3a), masticaton space disease (Fig Sa), mass effect in the nasopharynx, clivus erosion, and intracranial extension (Fig 7) (Table). As in earlier studies, we confirmed that certain abnormalities on CT scans, particularly bone destruction, did not return to normal despite the remission of infection and symptoms. However, there appeared to be a distinct subset of CT findings that did resolve with eradication of the bacterial infection. Specifically, fluid in mastoid or middle ear, as well as soft-tissue abnormalities beneath the temporal bone and skull base, disappeared or substantially improved within several months following antibiotic therapy. Since symptoms are frequently alleviated soon after the institution of antibiotics, there is uncertainty about the optimal duration of antimicrobial therapy. Thus, the resolution of soft-tissue disease on CT scans is an important objective marker in the symptom-free patient that may assist physicians
in
deciding
when
to
discon-
tinue antibiotic therapy. Malignant external otitis is notoriously difficult to eradicate, with a recurnence rate of approximately 20% in the larger clinical series (3). Our two patients with recurrent or persistent disease
as manifest
by
recurrence
of
headache and neelevation of ESR showed progressive soft-tissue changes at CT (Figs 3a, 6b). Thus, static CT scans may
be
useful
disease,
in
while
excluding
of disease
diagnosis
otitis
but
the
severity
394
S
of
also
further of
Radiology
the
malignant aid infectious
external in
assessing process.
b.
Figure 6. (a) Scan shows obscuration area of the great vessels (single arrow),
of fat planes around the mastoid tip (two arrows) and but the midline is clear, as are the fat planes medial
to the
arrow).
lateral
toid
tip
to the
pterygoid
has
muscles
improved,
lateral
sion
pterygoid
be obtained disease.
repeat
to rule In
the
posttherapy
is obscured
out
scans
auditory
tiguous.
findings
canal
are
is often
Clinically, of
whereas sent
ma.
the
severe
malignant
pain in
is usually early
2.
3.
4. 5.
6.
7. 8.
9.
arrow).
abnormality (arrow),
around and
the
the fat
mas-
medial
of
unlikely
not
to
exexter-
possible.
stages
pain external minimal
is charotitis,
Figure
10.
1 1.
U
Cohen D, Friedman P. The diagnostic critena of malignant external otitis. J Laryngol Otol 1987; 101:216-221. Cohen D, Friedman P. Eilon A. Malignant external otitis versus acute external otitis. Laryngol Otol 1987; 101:211-215. Rubin J, Yu VL. Malignant external otitis: insights into pathogenesis, clinical manifestations, diagnosis. and therapy. Am J Med 1988; 85:391-398. Rubin J, Yu VL, Stool S. Malignant external otitis in children. J Pediatr 1988; 113:965-970. Curtin HD, Wolfe P. May M. Malignant external otitis: CT evaluation. Radiology 1982; 145:383-388. Strashun A, Nejatheim M, Goldsmith SJ. Malignant external otitis: early scintigraphic detection. Radiology 1984; 150:541-545. Chandler JR. Pathogenesis and treatment of facial paralysis due to malignant external otitis. Ann Otol 1972; 81:648-658. Matucci KF. Setzen M, Galantich P. Necrotizing otitis externa occurring concurrently with epidermoid carcinoma. Laryngoscope 1986; 96:264-266. Gherini SG, Brackmann DE, Bradley WG. Magnetic resonance imaging and computerlied tomography in malignant external otitis. Laryngoscope 1986; 96:542-548.
12.
13.
Axial section through superior bone shows a small area of intrainvolvement (arrow).
7.
temporal cranial
on ab-
of cancino-
References 1.
(open
the midline
patient,
We have observed, however, that in malignant external otitis, bone erosion may occur in several areas with intervening “skip” regions, whereas, in cancinoma, bone erosions are usually conactenistic
the
should
progression
influence management. It should be noted that nadiologic differentiation between malignant ternal otitis and carcinoma of the nal
Although
crosses
If symptoms CT
asymptomatic CT
(b)
now
that CT scans be obof diagnosis prior to and at the conclutherapy.
on recur,
tissue
muscles
of antibiotic
persist
(open
abnormal
We recommend tamed at the time antibiotic therapy
recurrent
progression
on CT scans in a symptomatic patient can support the decision to continue or reinstitute antibiotics. When classifying our patients into groups based on the severity of disease, we found that those with a more virulent infection had more abnormalities of the initial CT scan than did those with a milder infection. Thus, the CT scan may not only contribute to the accurate
a.
Mendelson
MH,
Meyers
BR, Hirschman
SZ,
Shapiro ER, Parisier SC. Treatment of invasive external otitis with cefsulodin. Rev Infect Dis 1984; 6:698-704. Gold S. Som PM, Lawson W, Lucente FE, Mendelson M, Parisier SC. Radiographic findings in progressive necrotizing “malignant” external otitis. Laryngoscope 1984; 94:363-366. Mendez G, Quencer RM, Donovan Post MJ, Stokes NA. Malignant external otitis: a radiographic-clinical correlation. AJR 1981; 91:960-964. Ostfeld E, Aviel A, Pelet D. Malignant externat otitis: the diagnostic value of bone scmtigraphy. Laryngoscope 1981; 91:960-964.
14.
Garty
15.
clide diagnosis. evaluation and follow-up of malignant otitis externa (MOE): the value of immediate blood pool scanning. J Laryngol Otol 1985; 99:109-115. Parisier SC, Lucente FE, Hirschman SZ, Som
I. Rosen
PM, Arnold
16.
17.
18.
19.
G, Holdstein
LM, Riffman
Y.
JD.
The radionu-
Nuclear
scan-
ning in necrotizing progressive “malignant” external otitis. Laryngoscope 1982; 92:10161020. Reiter D, Bilaniuk LT, Zimmerman RA. Diagnostic imaging in malignant otitis externa. Otolaryngol Head Neck Surg 1982; 90:606609. Levin WJ, Shary JH, Nichols LT, Lucente FE. Bone scanning in severe external otitis. Laryngoscope 1986; 96:1193-1195. Kraus DH, Rehm SJ, Kinney SE. The evolving treatment of necrotizing external otitis. Laryngoscope 1988; 98:934-939. Gherini SC, Brackman DE, Bradley WG. Magnetic resonance imaging and computerized tomography in malignant external otitis. Laryngoscope 1986; 96:542-548.
February
1990