Introduction: The treatment of skull base lesions located in the parapharyngeal space or craniocervical
junction (CCJ) is a challenge. The endoscopic endonasal approach (EEA) is limited
inferiorly by the hard palate and laterally by the Eustachian tubes (ET). Access to
the parapharyngeal space may require an extensive transpterygoid approach and resection
of the medial ET. The base of the odontoid process is the inferior limit of the EEA.
This study investigates the feasibility of a contralateral transcaruncular approach
(CTA) to access the parapharyngeal space more directly and to reach the lower levels
of the CCJ.
Material and Methods: Eight human heads with colored-latex injection and thin-sliced CT scans for navigation
were dissected (16 sides). The parapharyngeal space and the CCJ were dissected through
a CTA bilaterally. A right transcaruncular approach was used to dissect the left parapharyngeal
space. The working distances were measured from the caruncle for the CT and the anterior
nasal spine for EEA using navigation to compare the two approaches. The base of the
styloid process was the target point for the parapharyngeal space. The inferior limit
of each approach in the craniocervical junction was similarly measured.
Results: (Surgical Technique) A posterior ethmoidectomy and sphenoidotomy were performed contralateral to the
side to be approached. A conventional transcaruncular approach was made ipsilaterally.
The medial wall of the orbit was removed after sacrifice of the ethmoidal arteries.
From the CTA, dissection of the sphenoid sinus, the inferior clival region, and the
parapharyngeal space were sequentially performed. The fossa of Rosenmuller was fully
exposed on both sides; the parapharyngeal segment of the carotid artery, the contents
of the jugular foramen, and the styloid process were visualized. This exposure did
not remove the resection of the ET. The condyle, the lateral mass, and the anterior
arch of C1 were then identified. Removal of the anterior arch of C1 allowed resection
of the body of C2 and C3 in all specimens.
Measurements: The working distance of the CTA to the right parapharyngeal space was 96.1 (± 6.1)
mm and 94.2 (± 7.1) mm on the right and left sides respectively. The EEA showed a
working distance of 97.9 (± 5.4) mm and 97.8 (± 5.5) mm to the right and left parapharyngeal
spaces, respectively. The difference between these distances was not statistically
significant. While the body of C3 was accessed from the CTA, an EEA did not allow
dissection of the C3 body in any specimen.
Conclusion: The CTA is feasible and can be used to access the parapharyngeal space and the upper
cervical spine as low as the C3 body. The working distances of the CTA and EEA are
similar. In the scenario of extensive extradural lesions, the CTA may play a role
helping to avoid a separate surgery such as a transoral or a transcervical procedure
while preserving of the ET.
