Background: Presigmoid approaches provide access to several structures anterior to the sigmoid
sinus and may be intended for the treatment of lesions located in the middle and posterior
fossa. The retrolabyrinthine approach is mostly used in combination with other approaches
like the anterior petrosal or as combined supra-infra-tentorial approaches to treat
lesions on the lateral brainstem or reach the retroclival region.[1]
[2]
[3]
Objective: To investigate the infratentorial presigmoid retrolabyrinthine suprameatal approach
(PRSA) as a standalone operative corridor. The typical anatomic-radiological characteristics
and variations were evaluated, and the related anatomical and radiological parameters
were analyzed to predict surgical accessibility.
Methods: Five adult, injected, cadaveric heads were operated on both sides, performing a total
of 10 surgical dissections. Twelve morphometric parameters were measured, analyzed,
and categorized into pre-procedural, intraprocedural, and additional parameters.
Results: Preoperative anatomic-radiological parameters provide valuable information to select
patients with favorable anatomy that may offer appropriate surgical accessibility
to the medial part of cerebellopontine angle cistern, lateral pons, and prepontine
cistern through a PRSA corridor. An obtuse petroclival angle of ≥144 degrees with
a more horizontally oriented petrous bone, a posterior sigmoid sinus position, and
a large mastoid cavity proved to be associated with the most effective PRSA corridor.
The superior petrosal sinus drainage and the degree of petrous apex pneumatization
were important to the fluency and the speed of the surgical technique. However, they
were not determinant factors in selecting the appropriate patient for the PRSA approach.
Conclusion: The PRSA represents a minimally invasive modification of the trans-labyrinthine approach.
It may be offered in patients who have lesions medial to the IAC, anterior and lateral
to the brainstem, with preservation of both vestibular and cochlear function. This
study highlights the importance of preoperative anatomic-radiological parameters for
selecting the most effective surgical approach on a patient-specific basis. The most
favorable presigmoid anatomy for obtaining optimal PRSA corridors with large and safe
anatomical exposure includes a more horizontally oriented petrous bone with an obtuse
petroclival angle and a more posterior position of the ipsilateral sigmoid sinus.
