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To The Editor: We read with interest the article by Matsushima et al.3 on using the so-called suprajugular extension of the retrosigmoid approach (Matsushima K, Kohno M, Komune N, et al: Suprajugular extension of the retrosigmoid approach: microsurgical anatomy. Laboratory investigation. J Neurosurg 121:397–407, August 2014). This study is about extension of the classic retrosigmoid approach to remove cerebellopontine angle lesions extending to the upper part of the jugular foramen. They explained suprameatal drilling to expose the area limited above by the internal acoustic meatus, cranial nerves (CNs) VII and VIII, and the labyrinthine artery and the area limited below by CNs IX–XI and the jugular bulb. Traditionally, the retrosigmoid, far lateral with transcondylar or paracondylar extensions, postauricular transtemporal, and preauricular subtemporal-infratemporal approaches have been used for lesions located inferior to the internal acoustic meatus with extension into the jugular fossa.1,2 This approach is an alternative for more extensive approaches that have been traditionally used to expose the jugular foramen and the caudal end of the petroclival fissure.
In our recent article,4 we explained the successful application of the “retrosigmoid intradural inframeatal (RSIM) approach” in 3 cases. As we discussed in the article, the area of bone drilling in this approach is inferior to the internal auditory canal and above the exit of the lower cranial nerves (Fig. 1). The amount of bone removed is not fixed in this approach and depends on the location and extension of the tumor. Under the control of neuronavigation and micro-Doppler ultrasonography, the resection can be safely extended medially to the petrous apex and anteriorly to the petrous internal carotid artery. Adding an operative endoscope, the surgeon can determine if there is a remaining part extracranially or inside the jugular foramen.
Considering the above-mentioned details, we believe that suprajugular extension of the retrosigmoid approach and the RSIM approach have significant overlap, and that the suprajugular bone drilling can be considered as a variant of the RSIM approach tailored to the lesions of the upper part of the jugular foramen. We prefer the term “retrosigmoid inframeatal approach” because it reminds us that it is an evolution of the well-known retrosigmoid “meatal” approach, which is commonly used for the resection of vestibular schwannomas, and because the term “inframeatal” is more specific for the bone drilling area than the general term of “suprajugular.”
We find anatomical studies like this very valuable in clarifying the details of this approach and for educating young neurosurgeons. However, we emphasize that the real intraoperative anatomy may be much more variable according to distortion of the anatomical landmarks because of the presence of the lesions and alterations in the relations between different neurovascular elements as compared with those observed in healthy subjects.
The authors report no conflict of interest.
This article contains some figures that are displayed in color online but in black-and-white in the print edition.
We are well acquainted with Dr. Samii and colleagues' excellent paper on the RSIM approach.1 The focus of their paper on the inframeatal approach and our paper on the suprajugular extension of the retrosigmoid approach are different. The lesions they described were between the internal auditory canal and the jugular tubercle with variable extension into the petrous apex. The lesion that we described extended into the upper part of the jugular foramen. The drilling areas of the inframeatal approach and the suprajugular extension may have some overlap, but the focus of their paper was the inframeatal area, while our focus was the roof of the jugular foramen, intrajugular process and ridge, and pyramidal fossa.
We believe that basic anatomical studies like ours will aid in understanding the complicated anatomy and pathologies involving these areas. We appreciate their comments and congratulate Dr. Samii's group on the excellence of their many contributions to posterior fossa surgery. We believe that neurosurgeons operating in this anatomical area will benefit by gaining an understanding of both the inframeatal approach they describe and the suprajugular extension described in our paper.