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1295
Do Abnormalities of the Frontonasal Duct Cause Frontal Sinusitis? A CT Study in 198 Patients .
.
Bertrand Pierre
Duvoisin1 Schnyder
OBJECTIVE.
.
The
purpose
of
the
study
was
to
determine
the
.
correlation
between
frontonasal duct abnormalities (narrowing or obstruction caused by hypertrophic mucosa) and frontal sinusitis. This study was based on the hypothesis that abnormalities of the
frontonasal
duct
MATERIALS
diagnoses
AND
37
frontal
CT
sinusitis
by impairing
studies
of 198 consecutive
of chronic sinusitis were reviewed
(1) no history As
cause
METHODS.
of sinus
surgery
or facial
sinuses
were
undeveloped,
frontal
normal
retrospectively.
trauma
and
of 359
of the
patients
with
sinus.
clinical
Criteria for inclusion were of polyps
(2) absence
a total
drainage
sinuses
at rhinoscopy.
were
evaluated.
CT
scans were obtained in oblique were assessed: (1) the frequency
axial and coronal planes. The following CT features of detection of the frontonasal duct, (2) the appearance of the frontonasal duct: normal vs abnormal (narrowed or obstructed), and (3) the correlations between abnormalities of the frontonasal duct and frontal sinusitis. RESULTS. The frontonasal duct was detected in all 359 cases, either in both CT planes (8i%) or only in the axial oblique plane (19%). In 267 (74%) of 359 cases, the duct appeared normal; among these, isolated frontal sinusitis was detected in five cases
(2%). In 92 (26%) (5%)
and
92 cases lations
of 359 cases,
obstructed
in 74 cases
of frontonasal
between
the duct was abnormal; (21%).
Frontal
duct abnormalities.
frontonasal
duct
sinusitis
The sensitivity
abnormalities
and
frontal
it was narrowed was
noted
and specificity sinusitis
in 18 cases
in 78 (85%) were
of the of the corre-
98%
and
85%,
respectively. Because
our
of the
CONCLUSION. frontonasal
duct
and
frontal
of the
frontonasal
duct
cause
AJR
159:1295-1298,
results frontal
December
show
sinusitis,
a strong
correlation
it seems
highly
between
probable
that
abnormalities abnormalities
sinusitis.
1992
In patients with chronic sinusitis, CT is needed to show the drainage pathways of the paranasal sinuses [1 2]. To the best of our knowledge, specific CT analysis of the drainage pathway of the frontal sinus, also called the frontonasal duct, has not been reported. ,
We postulated
Received April 27, 1992: June24, 1992.
accepted
after revision
1 Both authors: Department of Radiology, Centre Hospitalier Universitaire Vaudois (CHIN), 1 01 1 Lau-
sanne, Switzeriand.
that,
in patients
with
chronic
sinusitis,
abnormalities
of the
frontonasal duct cause frontal sinusitis. Abnormalities of the frontonasal duct are not congenital variations, but inflammatory lesions. Hypertrophic mucosa causes narrowing or obstruction of the frontonasal duct, with subsequent impairment of the drainage of the frontal sinus. Thus, when frontal sinusitis is detected by CT, the frontonasal duct also should be examined with CT. In this study, we (1) assess the frequency of CT detection of the frontonasal duct in patients with chronic sinusitis, (2) analyze the appearance of the frontonasal duct, and (3) correlate the
appearance
of the frontonasal
duct with that of the frontal sinus.
Address reprint requests to B.
Duvoisin.
0361 -803X/92/1 596-1 295 American Roentgen Ray Society
0
Materials CT studies
and
Methods
of 1 98 consecutive
patients
(74 males
and 1 24 females),
from
1 0 to 83 years
DUVOISIN
Downloaded from www.ajronline.org by 218.77.80.51 on 10/02/15 from IP address 218.77.80.51. Copyright ARRS. For personal use only; all rights reserved
1296
AND
SCHNYDER
AJA:159,
drainage
pathways
tion
demineralization
and
is unreliable
because
of their
December
of the characteristic
bony
structures.
1992
distor-
In our
series
of
1 98 patients (396 frontal sinuses), we found 37 undeveloped frontal sinuses (9%). Evaluation of the frontonasal duct, and correlation of its appearance with that of the frontal sinus, was thus feasible for 359 frontal sinuses. All CT examinations were performed with a CT Pace unit (General Electric Medical Systems, Milwaukee, WI), according to a protocol including
oblique
contrast
material.
sections
in the
The obliquity
the axis of the frontonasal relative
to the canthomeatal
was established
Fig. i.-Sagittal of frontonasal ferior aspect
CT scan of specimen
duct (arrows) and origin of frontal sinus.
of head shows obliquity of duct (arrowhead)
and tilting
at posteroin-
old (mean, 39 years), with chronic sinusitis were reviewed retrospectively. All examinations were done during a 2-year period, between January 1990 and December 1 991 . Chronic sinusitis was diagnosed clinically
on
the
basis
of a history
As sinus surgery or facial trauma impeding
its
detection
and
of mucopurulent
nasal
can alter the frontonasal
analysis,
history were not included in this study. nasosinusal polyposis were excluded,
patients
with
Furthermore, as analysis
such
discharge.
duct,
thus
a clinical
patients of their
with sinus
previously
axial
and
coronal
of the sections
plane,
was
without
determined
duct, which is tilted approximately line. This angle
of the frontonasal
on lateral radiographs
of cadaveric
IV
by
50#{176} duct
heads,
after opacification of the duct by a metallic probe introduced via the frontal sinus [3], and was also confirmed on sagittal CT scans of the specimen (Fig. 1). The sections obtained are perpendicular and parallel to the frontonasal duct, in the axial oblique plane and the coronal oblique plane, respectively. Two-millimeter-thick slices are obtained with 2-mm intervals through the whole sinus region in the axial oblique plane, and contiguous 2-mm-thick sections are centered on the anterior ethmoidal sinus in the coronal oblique plane. In the first 70 patients, routine milliampere-second settings (390 mAs) were used, whereas in 1 28 patients, low-dose CT was performed, as described
elsewhere
[4].
All sections
were
photographed
with
a large
window width (2000 H). All CT examinations were analyzed retrospectively by one of the authors. The only available information was that the patient had chronic sinusitis. No correlations were made with treatment or the patient’s outcome, as the study relied essentially on morphologic
Fig. 2.-Normal frontonasal duct in different patients. A, Coronal oblique CT scan shows medially situated frontonasal duct (straight arrows) on both sides. Note inflammation in both maxillary sinuses and small effusions (curved arrows). B, Coronal oblique CT scan in another patient shows lateral location of right frontonasal duct (straight arrow). Note obstruction of left maxillary drainage way, due to inflammation of left ostiomeatal complex (curved arrow). C, Axial oblique CT scan shows cleftlike right frontonasal duct (arrows). D, Axial oblique CT scan shows fusiform right frontonasal duct (straight arrow) and round left frontonasal duct (curved arrow).
C
D
AJA:159,
December
findings.
The
CT OF FRONTONASAL
1992
following
CT criteria
were
assessed:
(1) detection
of the
frontonasal duct, (2) appearance of the frontonasal duct: normal vs abnormal (i.e., narrowed or obstructed by hypertrophic mucO),(3) appearance of the frontal sinus: normal vs abnormal (i.e. , with hyper-
Downloaded from www.ajronline.org by 218.77.80.51 on 10/02/15 from IP address 218.77.80.51. Copyright ARRS. For personal use only; all rights reserved
trophic
mucosa
pearances abnormal) purposes obstructed
and/or
fluid),
and
(4) correlations
between
the
ap-
of the frontonasal duct (classified as either normal or and the frontal sinus. For clinical reasons and statistical (to diminish the number of classifications), narrowed and frontonasal ducts were combined into the abnormal group.
Sensitivity
and
specificity
of the
correlations
were
determined,
DUCT
1297
ABNORMALITIES
TABLE
i:
Frontonasal
CT Correlations
Between
Duct and Frontal
Appearances
of
Sinus
No. (% ) of Frontonas al Ducts Frontal
Sinus
Normal Sinusitis
Normal (n=267)
Narrow (n=18)
262 (98) 5 (2)
7 (39) 1 1 (61 )
Obstructed (n=74)
7 (10)
67 (90)
and
95% confidence interval (95% Cl) was calculated. The 95% CI was based on data relative to sinuses rather than to patients; actually, as there is no anatomic communication between right and left sinuses, correlations between frontonasal duct and frontal sinus are strictly homolateral. the
Discussion Recent developments in functional endoscopic sinonasal surgery have markedly increased the use of CT in the presurgical workup of chronic sinusitis [1 2, 5, 6]. CT is needed to assess the extent of the sinus abnormalities and to examine the drainage pathways, among which the ostiomeatal corn,
Results Among the 359 developed frontal sinuses, the frontonasal duct was visible on both axial oblique and coronal oblique CT scans in 289 cases (81 %), whereas it was recognized only on the axial oblique CT scan in 70 cases (1 9%). In 337 cases (94#{176}Io),the duct was medial (Fig. 2A), and in 22 cases (6%) it was lateral (Fig. 2B). In 320 cases (89%), the frontonasal duct appeared as a cleftlike (Fig. 2C) or fusiform (Fig. 2D) canal in the axial oblique plane, and in 39 cases (1 1 %), it was more
or less round (Fig. 2D). The CT correlations between the appearance of the frontonasal duct and that of the frontal sinus are summarized in Table 1 The frontonasal duct appeared normal in 267 cases .
(74%). In five of these cases (2%), CT showed
chronic
frontal
sinusitis, which consisted in slight hypertrophy of the frontal sinus mucosa; these five cases were considered false-negative. In 92 cases (26%), the frontonasal duct showed abnormalities, with narrowing by hypertrophic mucosa (Fig. 3) in 18 cases (5%), and obstruction (Fig. 4) in 74 cases (21 %). Among these 92 cases, frontal sinusitis was noted on CT in 78 cases
(85%), whereas
the frontal sinus appeared
normal in 14 cases
(1 5%), which were considered false-positive. When the false-negative and false-positive grouped, the sensitivity and specificity of the
cases are correlations
between appearance of the frontonasal duct and appearance of the frontal sinus are 98% (95% CI: 96-1 00%) and 85% (95%
Cl: 78-92%),
Fig. 3.-Reduced
respectively.
diameter
of right
plex is a key area. The anatomy
complex
,
extends
from the posteromedial
portion of the sinus floor and
runs caudally through the anterior ethmoidal labyrinth to its orifice in the nasal cavity [8-1 0]. The inferior aspect of the frontonasal duct is a component of the ostiomeatal complex
fronto-
nasal duct due to hypertrophic mucosa. A, Coronal oblique CT scan shows right frontonasal duct (arrow) as almost obstructed. B, Axial oblique CT scan shows partial patency of right frontonasal duct (arrow).
A
of the ostiomeatal
and its importance in the pathogenesis of chronic sinusitis have already been well documented [1 2, 5, 6]. On the contrary, the CT anatomy of the drainage pathway of the frontal sinus and the correlation between the appearance of this structure and that of the frontal sinus have not been studied. Recently, a CT study of the relationship between frontal sinus drainage and ostiomeatal complex disease was reported [7]. The authors reported that 72% of cases with involvement of the ostiomeatal complex did not have frontal sinus disease and concluded that this finding was associated with a separate drainage of the frontal sinus, which was thus spared in maxillary or ethmoidal sinusitis. The exact drainage system of the frontal sinus depends on its embryologic development. The drainage usually occurs directly into the frontal recess [8] or, by way of rudimentary anterior ethmoidal cells, into the frontal recess [8, 9]. The frontal recess is a deep anterosuperior depression in the middle meatus, which forms a closed channel in its upper surface, named the frontonasal duct [8-1 0]. Usually, the frontonasal duct runs medially across the anterior ethmoidal sinus, and rarely it runs laterally [9]. The frontonasal duct
B
Fig. 4.-Obstruction
of frontonasal
duct in two
Downloaded from www.ajronline.org by 218.77.80.51 on 10/02/15 from IP address 218.77.80.51. Copyright ARRS. For personal use only; all rights reserved
different patients. A, Coronal oblique CT scan in patient with frontal sinusitis shows obstruction of frontonasal duct (straight arrow) and frontal effusion (curved arrow). Note extensive inflammation of left ostiomeatal complex (arrowhead). B, Coronal oblique CT scan in patient without frontal sinusitis shows obstruction of left frontonasal duct (arrows), but normal aeration of frontal sinus.
Recent papers have reported that abnormalities of the ostiomeatal complex are associated with frontal sinus disease in 27-39% of cases [1 7]. No reports mention any statistical study dealing with the CT visibility, route, or appearance of the frontonasal duct.
frontonasal duct abnormalities, which impair drainage of the frontal sinus, are significantly associated with frontal sinusitis. These data show a high correlation between frontonasal duct abnormalities and frontal sinusitis, which is illustrated by a sensitivity of 98% (95% Cl: 96-i 00%) and a specificity of 85% (95% CI: 78-92%). In all cases (1 00%) in which the frontonasal duct was
This is probably
abnormal,
[6, 7]. Thus
it can be affected
zone, with possible
by disease
subsequent
disease
in this key anatomic
of the frontal
sinus.
,
because
the plane used in routine
coronal
CT is not suitable for analyzing the frontonasal duct, which is tilted approximately 50#{176} relative to the canthomeatal line [3]. CT identification of the frontonasal duct was initially achieved
in our
on cadaveric
and
relations Society
heads,
with endoscopic
and macroscopic
cor-
(Duvoisin B et al., presented at the Radiological of North America meeting, December 1 988). In vivo
CT studies confirming
were then correlated the specimen
data
with endoscopic
on frontonasal
duct
findings, identifica-
tion (Duvoisin B, unpublished data). The route and morphology ofthe frontonasal duct vary among subjects. In our series, in most
cases
(94%),
the duct
crosses
the medial
aspect
of
the anterior ethmoidal sinus. Usually, the frontonasal duct has an ovoid or cleftlike appearance on oblique axial slices (89%). In 11 % of cases, its shape is roughly circular. The results of this retrospective study show that the frontonasal coronal
duct is consistently oblique CT scans.
depicted on axial oblique and It was well recognized on both
axial oblique and coronal oblique scans in 289 cases (81%) and only on the axial oblique scan in the other 70 cases (1 9%). visibility
For these 70 cases, we postulate that the lack of of the frontonasal duct in the coronal oblique plane
is due either to partial volume effects or to an unusual anatomic tilting of the duct relative to the canthomeatal line. In 267
Associated
cases
frontal
(74%),
the
frontonasal
sinus abnormalities
duct
was
were detected
normal.
in only
five cases (2%). In all five cases these abnormalities consisted in slight hypertrophy of the mucosa of the frontal sinus; this was considered to have been caused by an earlier case of frontal sinusitis, which could have been associated with a previous, now cured, inflammatory narrowing of the frontonasal duct. In 92 cases the frontonasal duct showed chronic inflammatory changes, with hypertrophic mucosa narrowing (n = 1 8) or obstructing (n = 74) the frontonasal duct. Associated frontal sinusitis was observed in 78 cases (85%). Thus,
disease
series,
of the ostiomeatal
abnormalities
complex
of the frontonasal
was noted. As duct
are usually
associated with CT signs of frontal sinusitis (85%); our results differ significantly from published studies, which report 39% 27%
prevalences
ostiomeatal
of frontal
complex
abnormalities
sinus
in cases
of
[6, 7]. The hypothesis
disease
of
a separate drainage of the frontal sinus, evoked by others [7], thus seems debatable. In conclusion, we recommend careful examination of the frontonasal duct on CT scans of patients with chronic sinusitis, because duct abnormalities seem to correlate strongly with frontal sinusitis. REFERENCES 1 . Zinreich
SJ,
Kennedy
DW,
Rosenbaum
SE,
Gaylor
BW,
Kumar
AJ,
Stammberger
H. Paranasal sinuses: CT imaging requirements for endoscopic surgery. Radiology 1987:163:769-775 2. Chow JM, Mafee MF. Radiologic assessment preoperative to endoscopic sinus surgery. Otolaryngol Clin North Am 1989:22:691-701 3. Duvoisin
B, Schnyder
P, Agrifoglio
A. Evaluation
tomodensitom#{233}trique
que
de l’ethmoide ant#{233}rieur par des sections parall#{232}les et perpendiculaires a l’axe du canal frontonasal: etude pre#{233}liminaire.J Radiol i988;69: 787-789 4. Duvoisin
B, Landry
M, Chapuis
CT and inflammatory 1991:33:403-406 5. Kennedy DW, scopic sinus
L, Krayenbuhl
disease of the paranasal
Zinreich surgery.
M, Schnyder
P. Low-dose
sinuses. Neuroradiology
SJ, Rosenbaum AE, Johns ME. Functional endoArch Otolaryngol Head Neck Surg 1985:1 1 1:
576-582 6. Rice
DH.
Basic
surgical techniques and variations of endoscopic sinus Clin North Am 1989:22:713-726 7. Wallace R, Salazar JE, Cowles S. The relationship between frontal sinus drainage and osteomeatal complex disease: a CT study in 21 7 patients. AJNR i990;11 :183-186
surgery. Otolaryngol
8. Kaspar
KA. Nasofrontal
connections:
a study
based on one hundred
consecutive dissections. Arch Otolaryngol i936;23:322-343 9. Agrifoglio A, Terrier G, Duvoisin B. Etude anatomique et endoscopique de l’ethmoide ant#{234}rieur.Ann Otolaryngol Chir Cervicofac 1990: 1 07 :249-258 10. HeIler EM, Jacobs JB, Holliday RA. Evaluation of the frontonasal duct in frontal sinus fractures. Head Neck 1989:1 1 :46-50
1295
Do Abnormalities of the Frontonasal Duct Cause Frontal Sinusitis? A CT Study in 198 Patients .
.
Bertrand Pierre
Duvoisin1 Schnyder
OBJECTIVE.
.
The
purpose
of
the
study
was
to
determine
the
.
correlation
between
frontonasal duct abnormalities (narrowing or obstruction caused by hypertrophic mucosa) and frontal sinusitis. This study was based on the hypothesis that abnormalities of the
frontonasal
duct
MATERIALS
diagnoses
AND
37
frontal
CT
sinusitis
by impairing
studies
of 198 consecutive
of chronic sinusitis were reviewed
(1) no history As
cause
METHODS.
of sinus
surgery
or facial
sinuses
were
undeveloped,
frontal
normal
retrospectively.
trauma
and
of 359
of the
patients
with
sinus.
clinical
Criteria for inclusion were of polyps
(2) absence
a total
drainage
sinuses
at rhinoscopy.
were
evaluated.
CT
scans were obtained in oblique were assessed: (1) the frequency
axial and coronal planes. The following CT features of detection of the frontonasal duct, (2) the appearance of the frontonasal duct: normal vs abnormal (narrowed or obstructed), and (3) the correlations between abnormalities of the frontonasal duct and frontal sinusitis. RESULTS. The frontonasal duct was detected in all 359 cases, either in both CT planes (8i%) or only in the axial oblique plane (19%). In 267 (74%) of 359 cases, the duct appeared normal; among these, isolated frontal sinusitis was detected in five cases
(2%). In 92 (26%) (5%)
and
92 cases lations
of 359 cases,
obstructed
in 74 cases
of frontonasal
between
the duct was abnormal; (21%).
Frontal
duct abnormalities.
frontonasal
duct
sinusitis
The sensitivity
abnormalities
and
frontal
it was narrowed was
noted
and specificity sinusitis
in 18 cases
in 78 (85%) were
of the of the corre-
98%
and
85%,
respectively. Because
our
of the
CONCLUSION. frontonasal
duct
and
frontal
of the
frontonasal
duct
cause
AJR
159:1295-1298,
results frontal
December
show
sinusitis,
a strong
correlation
it seems
highly
between
probable
that
abnormalities abnormalities
sinusitis.
1992
In patients with chronic sinusitis, CT is needed to show the drainage pathways of the paranasal sinuses [1 2]. To the best of our knowledge, specific CT analysis of the drainage pathway of the frontal sinus, also called the frontonasal duct, has not been reported. ,
We postulated
Received April 27, 1992: June24, 1992.
accepted
after revision
1 Both authors: Department of Radiology, Centre Hospitalier Universitaire Vaudois (CHIN), 1 01 1 Lau-
sanne, Switzeriand.
that,
in patients
with
chronic
sinusitis,
abnormalities
of the
frontonasal duct cause frontal sinusitis. Abnormalities of the frontonasal duct are not congenital variations, but inflammatory lesions. Hypertrophic mucosa causes narrowing or obstruction of the frontonasal duct, with subsequent impairment of the drainage of the frontal sinus. Thus, when frontal sinusitis is detected by CT, the frontonasal duct also should be examined with CT. In this study, we (1) assess the frequency of CT detection of the frontonasal duct in patients with chronic sinusitis, (2) analyze the appearance of the frontonasal duct, and (3) correlate the
appearance
of the frontonasal
duct with that of the frontal sinus.
Address reprint requests to B.
Duvoisin.
0361 -803X/92/1 596-1 295 American Roentgen Ray Society
0
Materials CT studies
and
Methods
of 1 98 consecutive
patients
(74 males
and 1 24 females),
from
1 0 to 83 years
DUVOISIN
Downloaded from www.ajronline.org by 218.77.80.51 on 10/02/15 from IP address 218.77.80.51. Copyright ARRS. For personal use only; all rights reserved
1296
AND
SCHNYDER
AJA:159,
drainage
pathways
tion
demineralization
and
is unreliable
because
of their
December
of the characteristic
bony
structures.
1992
distor-
In our
series
of
1 98 patients (396 frontal sinuses), we found 37 undeveloped frontal sinuses (9%). Evaluation of the frontonasal duct, and correlation of its appearance with that of the frontal sinus, was thus feasible for 359 frontal sinuses. All CT examinations were performed with a CT Pace unit (General Electric Medical Systems, Milwaukee, WI), according to a protocol including
oblique
contrast
material.
sections
in the
The obliquity
the axis of the frontonasal relative
to the canthomeatal
was established
Fig. i.-Sagittal of frontonasal ferior aspect
CT scan of specimen
duct (arrows) and origin of frontal sinus.
of head shows obliquity of duct (arrowhead)
and tilting
at posteroin-
old (mean, 39 years), with chronic sinusitis were reviewed retrospectively. All examinations were done during a 2-year period, between January 1990 and December 1 991 . Chronic sinusitis was diagnosed clinically
on
the
basis
of a history
As sinus surgery or facial trauma impeding
its
detection
and
of mucopurulent
nasal
can alter the frontonasal
analysis,
history were not included in this study. nasosinusal polyposis were excluded,
patients
with
Furthermore, as analysis
such
discharge.
duct,
thus
a clinical
patients of their
with sinus
previously
axial
and
coronal
of the sections
plane,
was
without
determined
duct, which is tilted approximately line. This angle
of the frontonasal
on lateral radiographs
of cadaveric
IV
by
50#{176} duct
heads,
after opacification of the duct by a metallic probe introduced via the frontal sinus [3], and was also confirmed on sagittal CT scans of the specimen (Fig. 1). The sections obtained are perpendicular and parallel to the frontonasal duct, in the axial oblique plane and the coronal oblique plane, respectively. Two-millimeter-thick slices are obtained with 2-mm intervals through the whole sinus region in the axial oblique plane, and contiguous 2-mm-thick sections are centered on the anterior ethmoidal sinus in the coronal oblique plane. In the first 70 patients, routine milliampere-second settings (390 mAs) were used, whereas in 1 28 patients, low-dose CT was performed, as described
elsewhere
[4].
All sections
were
photographed
with
a large
window width (2000 H). All CT examinations were analyzed retrospectively by one of the authors. The only available information was that the patient had chronic sinusitis. No correlations were made with treatment or the patient’s outcome, as the study relied essentially on morphologic
Fig. 2.-Normal frontonasal duct in different patients. A, Coronal oblique CT scan shows medially situated frontonasal duct (straight arrows) on both sides. Note inflammation in both maxillary sinuses and small effusions (curved arrows). B, Coronal oblique CT scan in another patient shows lateral location of right frontonasal duct (straight arrow). Note obstruction of left maxillary drainage way, due to inflammation of left ostiomeatal complex (curved arrow). C, Axial oblique CT scan shows cleftlike right frontonasal duct (arrows). D, Axial oblique CT scan shows fusiform right frontonasal duct (straight arrow) and round left frontonasal duct (curved arrow).
C
D
AJA:159,
December
findings.
The
CT OF FRONTONASAL
1992
following
CT criteria
were
assessed:
(1) detection
of the
frontonasal duct, (2) appearance of the frontonasal duct: normal vs abnormal (i.e., narrowed or obstructed by hypertrophic mucO),(3) appearance of the frontal sinus: normal vs abnormal (i.e. , with hyper-
Downloaded from www.ajronline.org by 218.77.80.51 on 10/02/15 from IP address 218.77.80.51. Copyright ARRS. For personal use only; all rights reserved
trophic
mucosa
pearances abnormal) purposes obstructed
and/or
fluid),
and
(4) correlations
between
the
ap-
of the frontonasal duct (classified as either normal or and the frontal sinus. For clinical reasons and statistical (to diminish the number of classifications), narrowed and frontonasal ducts were combined into the abnormal group.
Sensitivity
and
specificity
of the
correlations
were
determined,
DUCT
1297
ABNORMALITIES
TABLE
i:
Frontonasal
CT Correlations
Between
Duct and Frontal
Appearances
of
Sinus
No. (% ) of Frontonas al Ducts Frontal
Sinus
Normal Sinusitis
Normal (n=267)
Narrow (n=18)
262 (98) 5 (2)
7 (39) 1 1 (61 )
Obstructed (n=74)
7 (10)
67 (90)
and
95% confidence interval (95% Cl) was calculated. The 95% CI was based on data relative to sinuses rather than to patients; actually, as there is no anatomic communication between right and left sinuses, correlations between frontonasal duct and frontal sinus are strictly homolateral. the
Discussion Recent developments in functional endoscopic sinonasal surgery have markedly increased the use of CT in the presurgical workup of chronic sinusitis [1 2, 5, 6]. CT is needed to assess the extent of the sinus abnormalities and to examine the drainage pathways, among which the ostiomeatal corn,
Results Among the 359 developed frontal sinuses, the frontonasal duct was visible on both axial oblique and coronal oblique CT scans in 289 cases (81 %), whereas it was recognized only on the axial oblique CT scan in 70 cases (1 9%). In 337 cases (94#{176}Io),the duct was medial (Fig. 2A), and in 22 cases (6%) it was lateral (Fig. 2B). In 320 cases (89%), the frontonasal duct appeared as a cleftlike (Fig. 2C) or fusiform (Fig. 2D) canal in the axial oblique plane, and in 39 cases (1 1 %), it was more
or less round (Fig. 2D). The CT correlations between the appearance of the frontonasal duct and that of the frontal sinus are summarized in Table 1 The frontonasal duct appeared normal in 267 cases .
(74%). In five of these cases (2%), CT showed
chronic
frontal
sinusitis, which consisted in slight hypertrophy of the frontal sinus mucosa; these five cases were considered false-negative. In 92 cases (26%), the frontonasal duct showed abnormalities, with narrowing by hypertrophic mucosa (Fig. 3) in 18 cases (5%), and obstruction (Fig. 4) in 74 cases (21 %). Among these 92 cases, frontal sinusitis was noted on CT in 78 cases
(85%), whereas
the frontal sinus appeared
normal in 14 cases
(1 5%), which were considered false-positive. When the false-negative and false-positive grouped, the sensitivity and specificity of the
cases are correlations
between appearance of the frontonasal duct and appearance of the frontal sinus are 98% (95% CI: 96-1 00%) and 85% (95%
Cl: 78-92%),
Fig. 3.-Reduced
respectively.
diameter
of right
plex is a key area. The anatomy
complex
,
extends
from the posteromedial
portion of the sinus floor and
runs caudally through the anterior ethmoidal labyrinth to its orifice in the nasal cavity [8-1 0]. The inferior aspect of the frontonasal duct is a component of the ostiomeatal complex
fronto-
nasal duct due to hypertrophic mucosa. A, Coronal oblique CT scan shows right frontonasal duct (arrow) as almost obstructed. B, Axial oblique CT scan shows partial patency of right frontonasal duct (arrow).
A
of the ostiomeatal
and its importance in the pathogenesis of chronic sinusitis have already been well documented [1 2, 5, 6]. On the contrary, the CT anatomy of the drainage pathway of the frontal sinus and the correlation between the appearance of this structure and that of the frontal sinus have not been studied. Recently, a CT study of the relationship between frontal sinus drainage and ostiomeatal complex disease was reported [7]. The authors reported that 72% of cases with involvement of the ostiomeatal complex did not have frontal sinus disease and concluded that this finding was associated with a separate drainage of the frontal sinus, which was thus spared in maxillary or ethmoidal sinusitis. The exact drainage system of the frontal sinus depends on its embryologic development. The drainage usually occurs directly into the frontal recess [8] or, by way of rudimentary anterior ethmoidal cells, into the frontal recess [8, 9]. The frontal recess is a deep anterosuperior depression in the middle meatus, which forms a closed channel in its upper surface, named the frontonasal duct [8-1 0]. Usually, the frontonasal duct runs medially across the anterior ethmoidal sinus, and rarely it runs laterally [9]. The frontonasal duct
B
Fig. 4.-Obstruction
of frontonasal
duct in two
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different patients. A, Coronal oblique CT scan in patient with frontal sinusitis shows obstruction of frontonasal duct (straight arrow) and frontal effusion (curved arrow). Note extensive inflammation of left ostiomeatal complex (arrowhead). B, Coronal oblique CT scan in patient without frontal sinusitis shows obstruction of left frontonasal duct (arrows), but normal aeration of frontal sinus.
Recent papers have reported that abnormalities of the ostiomeatal complex are associated with frontal sinus disease in 27-39% of cases [1 7]. No reports mention any statistical study dealing with the CT visibility, route, or appearance of the frontonasal duct.
frontonasal duct abnormalities, which impair drainage of the frontal sinus, are significantly associated with frontal sinusitis. These data show a high correlation between frontonasal duct abnormalities and frontal sinusitis, which is illustrated by a sensitivity of 98% (95% Cl: 96-i 00%) and a specificity of 85% (95% CI: 78-92%). In all cases (1 00%) in which the frontonasal duct was
This is probably
abnormal,
[6, 7]. Thus
it can be affected
zone, with possible
by disease
subsequent
disease
in this key anatomic
of the frontal
sinus.
,
because
the plane used in routine
coronal
CT is not suitable for analyzing the frontonasal duct, which is tilted approximately 50#{176} relative to the canthomeatal line [3]. CT identification of the frontonasal duct was initially achieved
in our
on cadaveric
and
relations Society
heads,
with endoscopic
and macroscopic
cor-
(Duvoisin B et al., presented at the Radiological of North America meeting, December 1 988). In vivo
CT studies confirming
were then correlated the specimen
data
with endoscopic
on frontonasal
duct
findings, identifica-
tion (Duvoisin B, unpublished data). The route and morphology ofthe frontonasal duct vary among subjects. In our series, in most
cases
(94%),
the duct
crosses
the medial
aspect
of
the anterior ethmoidal sinus. Usually, the frontonasal duct has an ovoid or cleftlike appearance on oblique axial slices (89%). In 11 % of cases, its shape is roughly circular. The results of this retrospective study show that the frontonasal coronal
duct is consistently oblique CT scans.
depicted on axial oblique and It was well recognized on both
axial oblique and coronal oblique scans in 289 cases (81%) and only on the axial oblique scan in the other 70 cases (1 9%). visibility
For these 70 cases, we postulate that the lack of of the frontonasal duct in the coronal oblique plane
is due either to partial volume effects or to an unusual anatomic tilting of the duct relative to the canthomeatal line. In 267
Associated
cases
frontal
(74%),
the
frontonasal
sinus abnormalities
duct
was
were detected
normal.
in only
five cases (2%). In all five cases these abnormalities consisted in slight hypertrophy of the mucosa of the frontal sinus; this was considered to have been caused by an earlier case of frontal sinusitis, which could have been associated with a previous, now cured, inflammatory narrowing of the frontonasal duct. In 92 cases the frontonasal duct showed chronic inflammatory changes, with hypertrophic mucosa narrowing (n = 1 8) or obstructing (n = 74) the frontonasal duct. Associated frontal sinusitis was observed in 78 cases (85%). Thus,
disease
series,
of the ostiomeatal
abnormalities
complex
of the frontonasal
was noted. As duct
are usually
associated with CT signs of frontal sinusitis (85%); our results differ significantly from published studies, which report 39% 27%
prevalences
ostiomeatal
of frontal
complex
abnormalities
sinus
in cases
of
[6, 7]. The hypothesis
disease
of
a separate drainage of the frontal sinus, evoked by others [7], thus seems debatable. In conclusion, we recommend careful examination of the frontonasal duct on CT scans of patients with chronic sinusitis, because duct abnormalities seem to correlate strongly with frontal sinusitis. REFERENCES 1 . Zinreich
SJ,
Kennedy
DW,
Rosenbaum
SE,
Gaylor
BW,
Kumar
AJ,
Stammberger
H. Paranasal sinuses: CT imaging requirements for endoscopic surgery. Radiology 1987:163:769-775 2. Chow JM, Mafee MF. Radiologic assessment preoperative to endoscopic sinus surgery. Otolaryngol Clin North Am 1989:22:691-701 3. Duvoisin
B, Schnyder
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DH.
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surgery. Otolaryngol
8. Kaspar
KA. Nasofrontal
connections:
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consecutive dissections. Arch Otolaryngol i936;23:322-343 9. Agrifoglio A, Terrier G, Duvoisin B. Etude anatomique et endoscopique de l’ethmoide ant#{234}rieur.Ann Otolaryngol Chir Cervicofac 1990: 1 07 :249-258 10. HeIler EM, Jacobs JB, Holliday RA. Evaluation of the frontonasal duct in frontal sinus fractures. Head Neck 1989:1 1 :46-50
