Key-words:
Pituitary adenoma - tension pneumatocele - transsphenoidal
Introduction
Tension pneumatocele is a rare but potentially fatal complication of transsphenoidal
surgery that can result from an influx of air into the intracranial cavity through
the cerebrospinal fluid (CSF) fistula which develops during the operation or after
the surgery.[[1]] It has been known that the prompt diagnosis and the management, most likely surgical
intervention, are required when the tension pneumocephalus causes neurologic deterioration
by a mass effect. We herein report tension pneumatocele after transsphenoidal surgery
for pituitary macroadenoma. Tension pneumocephalus can occur at any time after the
surgery and deterioration after transsphenoidal surgery should be instantaneously
evaluated. Tension pneumatocele following transsphenoidal surgery usually occurs after
the presentation of a CSF leak due to an incomplete sealing of the sphenoid sinus.
Postoperative insertion of lumbar drainage appears to be a predisposing factor for
this complication. Patients who develop this expanding pneumatocele usually present
with progressive vision loss and headache. If left untreated, this condition can lead
to permanent visual deficits.[[2]] We report a case of tension pneumatocele after transsphenoidal resection of a pituitary
macroadenoma that required treatment with CSF leak repair and lumbar spine drainage.
The patient was successfully treated endoscopically with a good clinical outcome.
We also discuss important strategies for managing this neurosurgical emergency.
Case Report
A 40-year-old male patient presented with vision loss and headache of 2 months. Preoperative
magnetic resonance images (MRI) revealed a large contrast-enhancing mass in sellar
and suprasellar regions abutting bilateral internal carotid arteries [[Figure 1]]. This finding suggested a pituitary macroadenoma. The neurological examination
revealed bilateral hemianopsia. Visual acuity was hand movement positive in the right
eye and 6/12 on the left eye. The level of pituitary hormones was within the normal
limits. He was diagnosed with a case of nonfunctional pituitary macroadenoma and underwent
transsphenoidal resection of pituitary macroadenoma. There was no CSF leak during
the surgery and it was confirmed with intraoperative Valsalva maneuver also. The sella
and sphenoid sinus were packed with pieces of fat and surgicel. On day 1 after the
surgery, patient reported significant subjective improvement in vision. Postoperatively,
on day 2, the patient had CSF rhinorrhea and an external lumbar drain catheter was
inserted to prevent CSF rhinorrhea. CSF was drained through the catheter at the rate
of 5–10 ml/h. On the 3rd postoperative day, the patient complained of severe headache
and decreased vision in both eyes to only perception of hand movements bilaterally.
An emergent computed tomography (CT) scan was obtained. It revealed a large amount
of air collection in the suprasellar region [[Figure 2]]a. The patient underwent immediate reoperation through an endonasal endoscopic approach.
After the trapped air was evacuated, the sella floor was subsequently repaired with
fascia lata graft and muscle using fibrin glue. Examination of the cavity was performed
with 0°and 30° nasal telescopes, and no residual tumor was appreciated. The pneumatocele
was endoscopically decompressed using a transnasal approach guided by intraoperative
fluoroscopy.
Figure 1: Preoperative sagittal (a) and coronal (b) gadolinium-enhanced magnetic resonance
images shows large pituitary tumor with suprasellar extension
Figure 2: On the postoperative day 3, the patient developed severe headache and sudden visual
deterioration. CT of the head (a) demonstrates suprasellar tension pneumatocele. The
patient underwent emergent endoscopic exploration and revision of the skull base repair
was performed to obliterate a ball-valve fistula. (b) Postoperative computed tomography
(CT) demonstrates resolution of the tension pneumatocele
Skull lateral films which were obtained during surgery revealed a decrease in the
air gradually [[Figure 3]]a and [[Figure 3]]b. A CT scan obtained after the second surgery showed that the intracranial air
decreased markedly [[Figure 2]]b. The patient's symptoms resolved and vision improved postoperatively.
Figure 3: Intraoperative fluoroscopy was used to verify adequate decompression of the tension
pneumatocele, (a) before starting surgery, (b) prior to closure of the operation
The external lumbar drain was clamped postoperatively and was removed after 3 days
when no CSF leak was observed. After these procedures, he showed a significant improvement
of his symptoms and his headache and CSF leakage resolved. At the time of 3 months
follow-up, the patient was free of symptoms, and his visual acuity was 6/18 in the
right eye and 6/6 in the left eye.
Discussion
Tension pneumatocele following transsphenoidal surgery is extremely rare and may arise
in the setting of a surgical sellar floor defect.[[3]] Patients with this complication specifically present with progressively deteriorating
vision and bitemporal hemianopsia and sometimes, a headache.[[4]] Tension pneumatocele may develop a few weeks, months, or years after the surgery.[[2]] Two factors which influence the development of tension pneumatocele after transsphenoidal
surgery are a one-way valve (ball-valve) mechanism and low intracranial pressure.[[3]],[[4]],[[5]],[[6]]
The predisposing factors which have been described for expanding pneumatocele includes
sub-optimal packing of the sella and sellar floor reconstruction, CSF leaks, large
pituitary tumor, and postoperative lumbar drainage catheter. Other factors which may
predispose to development of this complication include alteration of the pressure
gradient across CSF fistula with sneezing, vigorous nose blowing, nose bleeds, and
positive pressure ventilation, untreated obstructive sleep apnea, diminished CSF formation
by acetazolamide diuretic use, dehydration or systemic hypotension.[[1]],[[2]],[[7]] The factors predisposing to tension pneumatocele in the present case include CSF
leak, large pituitary tumor, and postoperative lumbar drainage catheter.
A plain skull X-ray can help in making the diagnosis. However, head CT is diagnostic
and may be superior when ruling out other complications, such as hemorrhage or infarction.
MRI may be required to evaluate tumor recurrence and to best visualize any distortion
of the optic chiasm.
Once diagnosed, clinical management of pneumatocele is dictated by the degree of mass
effect and clinical symptoms and should be managed promptly as it can lead to permanent
visual changes. The endoscopic approach offers a straightforward repair with minimal
trauma to the sphenoid and posterior nasal tissue. Intraoperative fluoroscopy can
be used to verify adequate decompression of the tension pneumatocele before closure
of the operation.
It has been postulated that air from the paranasal sinuses may be entrapped through
an anatomic one-way ball valve mechanism through the fascia lata graft and into the
intracranial compartment.[[7]] In the present case, the air accumulation probably occurred when fascia and fat
packing of the sphenoid sinus created a ball-valve effect. In our patient, incomplete
closure of the sellar floor, postoperative CSF leak and forced air entry due to the
negative pressure created by lumbar drainage probably played major roles in the development
of the tension pneumatocele.
It is important to be vigilant for the possibility of evolving pneumatocele in all
patients undergoing transsphenoidal surgery, who develop headache and/or the delayed
appearance of visual deterioration. This will remain a rare complication but should
be considered in a patient with postoperative deterioration with chiasmal compression.
A plain skull X-ray is usually sufficient for the diagnosis. This complication should
be added to the list of possible differential diagnoses after transsphenoidal surgery
in a patient who postoperatively develops headaches, becomes somnolent, and develops
visual difficulties.
Conclusion
Tension pneumatocele is an uncommon but potentially lethal complication of transsphenoidal
pituitary surgery, which can present anytime, even after years postoperatively. Prompt
identification and management of this condition can be lifesaving. As such, it could
be overlooked at the time of following up if one is not aware of this extremely rare
possibility. It is crucial to consider this as a differential diagnosis in patients
presenting with headaches or visual deterioration after transsphenoidal surgery. A
large number of factors can predispose to CSF leak and pneumocephalus and the prevention
of intraoperative CSF leak is important. It is important for neurosurgeons and otorhinolaryngologists
to be aware of this condition so that prompt treatment can be instituted.
