Keywords Sternberg's canal - meningoencephalocele - transpterygoid repair - spontaneous CSF
leak - lateral craniopharyngeal canal
Case Report
A 27-year-old nonobese female patient who works as a sales executive presented to
our hospital with a 1-day history of vomiting, severe headache, diarrhea, neck stiffness,
and history of “sinus” disease. There was no past medical history of note, that is,
diabetes, hypertension, or asthma. She had no known allergies and had no occupational
exposure. Her examination was essentially normal, with blood pressure (BP) reading
of 114/78 mm Hg, pulse of 93 bpm, and normal cardiovascular and respiratory examination.
At the time of admission, it was suspected that she had acute bacterial meningitis
due to possible acute sinusitis. Lumbar puncture and examination showed turbid fluid,
increased proteins, neutrophils, and raised glucose level. She was referred for a
computed tomography (CT) scan of the brain and sinuses, which showed an opacified
left sphenoid sinus. She was referred to our department for further evaluation and
management. There was no anosmia or hyposmia with normal vision and normal voice.
Of note was history of persistent unilateral rhinorrhea of 2 years' duration. Ear,
nose, and throat (ENT) examination revealed pale enlarged turbinates, but no polyposis
or deviated nasal septum. There fluid was sent for β2 transferrin biochemistry, which
confirmed cerebrospinal fluid (CSF). A dedicated CT scan of the sinuses showed a dehiscence
in the lateral wall of the left sphenoid sinus ([Fig. 1 ]).
Fig. 1 Coronal computed tomography (CT) scan showing opacified sphenoid sinus and dehiscence
in the left lateral sphenoid sinus wall. The blue arrow depicts the foramen rotundum and the maxillary nerve. The yellow arrow shows the location of the dehiscence, medial to the foramen rotundum.
The patient was taken to the operating theater for closure of a suspected Sternberg's
canal (SC) defect and meningocele. The procedure was done endoscopically via endonasal
transpterygoid approach under general anesthesia. The anterior wall of the sphenoid
sinus and the rostrum were removed and the pterygoid plates drilled for access to
the lateral wall of the sphenoid sinus. An encephalomeningocele was exposed and reduced,
and the defect was identified ([Fig. 2 ]). The hole was plugged with a fat, covered by fascia, Gelfoam, and DuraSeal to complete
the multilayer closure.
Fig. 2 Intraoperative view of meningoencephalocele through an inferolateral dehiscence and
the defect after reduction.
The procedure was uneventful and the patient was discharged 48 hours later. It has
been 18 months since the procedure and there is no recurrence of the leak.
Discussion
Spontaneous CSF leaks with meningoencephaloceles in the sphenoid sinus are rare with
an incidence of 1 in 35,000 people.[1 ]
[2 ]
[3 ] These spontaneous cases have been reported in females in their fourth and fifth
decades of life.[2 ] CSF leaks are generally classified according to the underlying etiology and those
that do not have an obvious cause are referred to as idiopathic or spontaneous. Spontaneous
CSF leaks occur without history of trauma, tumors, or iatrogenic injuries.
One contentious area of these leaks is the area of SC. The canal was first described
by Maximillian Sternberg in 1888.[4 ]
[5 ] His description of the defect is the dehiscence is usually located medial to the
foramen rotundum and medial to the vidian canal. In his study, Sternberg identified
that the majority of 3- and 4-year-olds had a defect in the lateral wall of the sphenoid
but only 4% of adults showed the same.[5 ]
Our patient had a defect that was located medial to the foramen rotundum, which was
highly suggestive of a true SC ([Fig. 1 ]). There is disagreement in the literature as to whether SC is indeed a source for
CSF leaks. In their article, Koch et al disputed and attributed the leak to raised
intracranial pressure.[4 ] Illing et al also attributed the leak to other causes other than an SC.[3 ] However, cases have been documented showing this dehiscence as the source of the
leak.[1 ]
[2 ]
[5 ]
[6 ] Schick et al offer some explanation in the localization and classification of this
dehiscence: to differentiate between congenital and nontraumatic acquired skull base
defects and that fusion planes offer special resistance to pneumatization. As a result,
defects occurring at fusion planes within the sphenoid sinus are more likely to be
congenital in origin than acquired.[7 ]
We document here the case of a young lady with no predisposing factors presenting
with clear watery discharge from the nose and recurrent meningitis. She was treated
via the endoscopic transnasal transpterygoid approach where CSF leak and a protruding
encephalocele was demonstrated ([Fig. 2 ]). The importance of repairing these defects is to prevent further CSF rhinorrhea,
and prevent further growth of the defect and meningitis resulting in intracranial
complications.[8 ]
[9 ] Of significance, her CT scan showed wide pneumatization of the sphenoid sinus, which
enhanced the importance of pneumatization of the sphenoid sinus in the pathogenesis
of the leak. Since the procedure, the patient has been asymptomatic. Endoscopic approach
is considered less traumatic and has low morbidity compared to extracranial technique
and is the procedure of choice.[5 ] Time for surgery, hospitalization, and recovery is also markedly reduced.[1 ]
[10 ] Success rates in endoscopic repair approaches 90% as compared to the open approach.[10 ]
Some authors have sought to explain the causes for spontaneous CSF leak. Association
between middle-aged overweight females and central obesity as possible causes has
been made. The explanation is that raised intra-abdominal pressure increases intravenous
pressure and therefore raised intracranial pressure.[3 ]
[4 ] Our patient was not overweight and her body mass index (BMI) was 25 kg/m2 and did not demonstrate any radiological features of raised intracranial pressure,
namely, empty sella, attenuation of the skull base, posterior globe flattening, sulcal
effacement, ventricular effacement, arachnoid pits, and loss of gray–white differentiation.[3 ]
[10 ]
Another factor associated with spontaneous CSF leak is extensive sphenoid sinus pneumatization.
Our patient had extensive pneumatization of the sphenoid sinus with a large area of
the lateral sinus in contact with the middle cranial fossa.
Conclusion
Although SC is a source of controversy,[1 ]
[2 ] it should still be considered when assessing a patient for spontaneous CSF leak,
especially in patients with extensive sphenoid sinus pneumatization. Irrespective
of the cause, spontaneous CSF leaks need to be repaired to prevent rhinorrhea and
recurrent meningitis. The endoscopic transpterygoid approach is the procedure of choice
in view of its low morbidity, low complication rate, and decreased hospitalization.
