Cholesterol granulomas are inflammatory lesions that occur rarely in the petrous apex.[1] Initially, these lesions tend to remain asymptomatic. As they expand, headaches
and cranial neuropathies may arise.[1]
[2] The treatment of symptomatic petrous apex cholesterol granuloma (PACG) is surgical
drainage of the cyst and permanent aeration of petrous apex air cells to prevent recurrence.[1]
[3] Several transcranial approaches have been used to treat these lesions, the choice
of which depends on the patient's preoperative hearing status and the lesion's location
in relation to critical neurovascular structures.[2]
[3]
[4]
[5] These traditional lateral skull base approaches expose the inner ear and facial
nerve to potential structural damage as well as add morbidities of any intracranial
procedure.[4] They also have the shortcoming of often producing a relatively narrow bony opening,
potentially compromising long-term drainage and preventing the use of stents between
the aerated cavity and the sphenoid sinus. In addition to having recurrence rates
as high as 60%, repeat transcranial surgeries for recurrent lesions may be associated
with significant morbidities.[2]
[3] Recently, the endoscopic endonasal approach has gained popularity in the neurosurgical
community. This less invasive approach is attractive for the initial surgical management
of symptomatic PACG and possibly even more so for symptomatic recurrent PACG.
In this report, we describe a case of recurrent symptomatic PACG treated by an expanded
endonasal approach. We review all reported cases treated by an endoscopic endonasal
approach and attempt to establish management pearls regarding the endoscopic endonasal
management of PACG.
CASE REPORT AND TECHNIQUE DESCRIPTION
A 19-year-old woman presented with an ongoing severe headache of subacute onset and
3-day history of diplopia. Physical examination was unremarkable except for right
abducens nerve palsy. Head computed tomography scan demonstrated expansion of the
right petrous apex. Magnetic resonance imaging showed a right petrous apex mass measuring
25 × 14 × 14 mm abutting the posterior wall of the sphenoid sinus. The lesion was
hyperintense on both T1- and T2-weighted images and did not enhance following gadolinium
administration (Fig. [1]). Given her rapid onset of symptoms, surgical drainage was recommended.
Figure 1 Preoperative and postoperative magnetic resonance T2-weighted axial images (A, D),
T1-weighted sagittal images (B, E), and T1-weighted postgadolinium coronal images
(C, F).
The patient underwent an endonasal transsphenoidal approach using intermittently the
operating microscope and the endoscope for visualization. The location of the lesion
was confirmed in the lower inferior right aspect of the sphenoid sinus with intraoperative
neuronavigation. After creating a wide bony opening to the face of the cholesterol
granuloma, its capsule was incised. Characteristic greenish fluid with cholesterol
crystals poured forth. After satisfactory drainage, the bony opening was widened and
multiple fragments of the capsule were removed. Final inspection of the cyst's cavity
showed complete drainage of the lesion. Postoperatively, symptoms progressively resolved.
Four months after initial surgery, clinicoradiological recurrence occurred and mandated
a repeat transsphenoidal and infrapetrous approach (Fig. [2]). After removing scar tissue from the prior bony opening in the sphenoid floor,
care was taken to identify the vertical and horizontal segments of the internal carotid
artery. The high-speed drill was used to widen the bony opening inferior to the petrous
carotid into the petrous apex in a medial and inferior direction. Once exposed on
a large surface, the anterior wall of the cyst was removed, the content of the cyst
was drained, and its lining partly removed. A 45-degree endoscope allowed visualization
of the empty cavity (Fig. [3]). A Doyle splint was inserted into the cyst's cavity on ∼1 cm and extended out into
the sphenoid sinus, maintaining patency during the healing process. At 3 months after
surgery, the Doyle splint was removed under endoscopic visualization. A healed cylindrical
communication between the involved petrous apex cells and the sphenoid sinus was appreciated
(Fig. [4]). A rubber catheter was used to irrigate the aerated cavity. The patient currently
remains symptom- and recurrence-free 15 months postoperatively.
Figure 2 Magnetic resonance images at clinical recurrence: T2-weighted axial image (A), T1-weighted
sagittal image (B), and T1-weighted postgadolinium coronal image (C).
Figure 3 Intraoperative view of the repeat transsphenoidal and infrapetrous approach. (A)
Exposure of the petrous apex and cyst on a large surface. (B) Widening of the bony
opening inferior to the petrous carotid into the petrous apex in a medial and inferior
direction. (C) Visualization of the emptied cavity with a 45-degree endoscope. (D)
Insertion of a Doyle splint into the cyst's cavity.
Figure 4 Intraoperative view of the removal of the Doyle splint with irrigation of the cavity.
DISCUSSION
Cholesterol granulomas rarely occur in the petrous apex because the petrous apex is
pneumatized in only 30% of temporal bones.[6] They result from obstruction of the normal aeration of petrous apex air cells. This
obstruction is believed to lead to negative pressure within the air cells, eventually
causing mucosal edema, tissue breakdown, and hemorrhage and accumulation of breakdown
products such as cholesterol.[1]
[2] The cholesterol crystals induce a granulomatous inflammatory reaction resulting
in the typical cholesterol granuloma.
For symptomatic patients, surgery is presently the only treatment option available.
Surgical treatment implies cyst drainage, with or without removal of its lining, and
restoration of air cell aeration. Some authors have also proposed complete excision
of the lesion followed by obliteration of the cavity with vascularized tissue.[2] Numerous transcranial approaches have been performed to treat PACG such as middle
cranial fossa approaches and lateral skull base approaches including the translabyrinthine,
infratrochlear, infralabyrinthine, transcochlear approaches.[2]
[3]
[4]
[5] The specific approach recommended depends on the patient's hearing status and the
cyst's location. Given the lateral trajectory of transcranial skull base approaches,
they inevitably expose the inner ear and facial nerve to potential structural damage
as well as add morbidities of any intracranial procedure.[4]
[7]
In addition, although satisfactory cyst drainage may be accomplished through these
external routes, the bony opening obtained is often relatively narrow, rendering difficult
intraoperative splinting techniques and potentially putting at risk chronic drainage.
Indeed, recurrences have been reported to be as high as 60% irrespective of the transcranial
approach used and degree of completeness of removal.[2]
[3] Stenosis of the opening used to exteriorize the cyst may result in reaccumulation
of its contents and recurrence of symptoms. Just as for initial procedures, revision
transcranial surgeries for recurrent lesions may also be associated with significant
morbidities.
Contemporary progresses in endoscopic surgery as well as in image-guidance technology
have allowed treatment of PACG through a less invasive route. Petrous lesions located
medial to the internal carotid artery (ICA) and that abut, protrude, or invade the
sphenoid sinus may be safely approached through a transsphenoidal approach[3]
[7]
[8]
[9]
[10]
[11]
[12]
[13] (Table [1]). The use of the endoscope as visualization technique has enabled a more complete
drainage of the cyst.[14] The cyst cavity may be closely inspected under endoscopic visualization to remove
septations between separate fluid loculations or any remote debris.[14]
Table 1 Summary of Reported Cases of Petrous Apex Cholesterol Granuloma Treated via the Endonasal
Endoscopic Approach
| Author |
Age, Sex |
Preoperative Symptoms |
Location of CG in Relation to Sphenoid Sinus (SS) |
Symptoms on Follow-Up (Length of Follow-Up, mo) |
Procedure |
Complication |
Symptomatic Recurrence |
| Griffith and Terrell (1996)[3]
|
34, M |
Disequilibrium |
Protruding into the posterior SS, bony erosion |
Asymptomatic (18) |
TS drainage of cyst; wide opening of the cyst cavity |
Transient epistaxis |
None |
| 24, M |
Hearing loss, V3 hypesthesia |
Protruding into SS |
Asymptomatic after 3rd OR (12) |
1st: subtemporal transzygomatic approach; 2nd: TS drainage of cyst; 3rd: TS drainage
of cyst and wide opening of the cyst cavity |
None |
Recurrence 2 mo after 1st OR; recurrence 2 mo follow-up after 2nd OR; no recurrence
after 3RD OR |
| Michaelson et al (2001)[8]
|
13, F |
H/A, VIth nerve palsy |
Abutting the posterior SS |
Asymptomatic (6) |
TS drainage of cyst; wide opening of the cyst cavity; marsupialization |
None |
None |
| DiNardo et al (2003)[9]
|
62, F |
Disequilibrium |
Abutting the posterior SS, separated by a thin layer of bone |
Asymptomatic (12) |
TS drainage of cyst; wide opening of the cyst cavity |
None |
None |
| Presutti et al (2006)[10]
|
38, M |
H/A, VIth nerve palsy, increasing vertigo |
Abutting the posterolateral wall of the SS |
Asymptomatic (3) |
TS drainage of cyst; wide opening of the cyst cavity; placement of T-shaped stent |
None |
None |
| Oyama et al (2007)[11]
|
28, F |
Hemifacial pain |
Protruding in the posterior SS, separated by a thin layer of bone |
Asymptomatic (24) |
TS drainage of cyst; wide opening of the cyst cavity |
None |
None |
| Georgalas et al (2008)[7]
|
30, M |
Facial palsy, sensorineural hearing loss, vertigo |
Abutting the posterolateral SS |
Asymptomatic (120) |
TS drainage of cyst; wide opening of the cyst cavity; marsupialization |
None |
None |
| 13, M |
H/A, VIth nerve palsy |
Sphenopetrous lesion, almost completely obliterating SS |
Asymptomatic (72) |
1st: middle fossa approach; 2nd: TS drainage of cyst; wide opening of the cyst cavity;
marsupialization |
None |
Recurrence after 1st OR (time to recurrence not specified); no recurrence after 2nd
OR |
| 44, F |
H/A |
Protruding into the posterior SS |
Asymptomatic (24) |
TS drainage of cyst; wide opening of the cyst cavity; marsupialization |
None |
None |
| Samadian et al (2009)[12]
|
28, F |
H/A, VIth nerve palsy, hearing loss |
Protruding in the posterior SS, separated by a thin layer of bone |
Asymptomatic (48) |
TS drainage of cyst; wide opening of the cyst cavity; marsupialization; placement
of a Silicone tube drain |
None |
None |
| Zanation et al (2009)[13]
|
8 patients |
All had H/A; 2 had occasional vertigo |
No detail |
No detail |
TS: 2; TS with carotid lateralization: 3; IP approach: 3; drainage of cyst and stenting |
None |
One recurrence at 2.5 y after 1st OR |
| Present case |
19, F |
H/A, VIth nerve palsy |
Abutting the posterior SS |
Asymptomatic to date (15) |
1st: TS drainage of cyst; wide opening of the cyst cavity; partial marsupialization;
2nd: TS and IP for drainage of cyst; very wide opening of the cyst cavity; marsupialization;
placement of a Doyle stent |
After 1st OR: delayed epistaxis |
Recurrence 4 mo after 1st OR; no recurrence yet after 2nd OR |
| CG, cholesterol granuloma; H/A, headache; IP, infrapetrous; mo, months; OR, operation;
SS, sphenoid sinus; TS, transsphenoidal. |
Including the present case, 19 cases of PACG have been treated through an endoscopic
endonasal approach (Table [1]).[3]
[7]
[8]
[9]
[10]
[11]
[12]
[13] Sixteen of the 19 patients have been drained initially through a medial transsphenoidal
approach (with or without lateralization of the ICA). Three of these 16 patients developed
a symptomatic recurrence that required repeat surgery. The remaining three patients
had been drained initially via an intrapetrous approach and did not develop a recurrence.[13] Accordingly, 3 of 19 patients (15.7%) with PACG treated via an endonasal route presented
a postoperative recurrence at 2, 4, and 30 months. This recurrence rate (15.7%) is
significantly lower than that reported following other approaches (up to 60%). Several
factors may contribute to this lower recurrence rate including a wider bony opening
and, consequently, a more extensive removal of the cyst's anterior or medial wall,
afforded by the endonasal endoscopic approaches (especially with the infrapetrous
approach). In addition, the superior visualization of the cavity using angled endoscopes
enables to assess and address remaining septations and/or debris and therefore optimizing
the drainage.[14] Furthermore, the use of a stent to preserve a drainage pathway throughout the healing
process may contribute to reducing recurrences. This is especially important with
the infrapetrous approach because the path of dissection is deeper than that performed
in the medial transsphenoidal approach and therefore may be at greater risk of scarring.[13] All of these considerations are of utmost importance when treating a recurrent PACG.
We favor the endonasal endoscopic infrapetrous approach for recurrent PACG regardless
of the initial surgical approach. In comparison to a transcranial surgery that may
be associated with significant morbidity, no complications have yet occurred following
endonasal endoscopic treatment for recurrent PACG.
CONCLUSION
Overall, the endoscopic endonasal route enables treatment of PACG through an anterior
trajectory, preserving hearing and vestibular and facial function. This approach is
significantly less invasive than traditional transcranial procedures with overall
reduced morbidity, shortened procedure time, reduced hospital stay, better cosmetic
results, and lower recurrence rates. It should be considered as the preferred surgical
alternative for initial treatment of symptomatic PACG but also for the treatment of
symptomatic recurrence, independently of the initial surgical route. Repeat endoscopic
endonasal surgery must be adapted to recurrent PACG. The infrapetrous approach with
wider bony opening, extensive anterior cyst wall removal, and use of a stent should
be the treatment of choice for recurrent PACG.
