Surgical anatomy of the singular nerve

Anatomy of petrous face

The anatomy of the petrous face of the temporal bone, also known as the petrous pyramid, should be carefully examined to understand the location of, blood supply to, and venous drainage of meningiomas in this area (42%-59% of posterior fossa meningiomas). The petrous face is located in the skull base between the sphenoid and occipital bones. It consists of a base that joins the mastoid laterally and an apex that extends anteromedially to form the foramen lacerum. The anatomy can be divided into three surfaces: anterior/superior, posterior, and inferior. The anterior/superior surface is a continuation of the posteromedial portion of the middle cranial fossa with boundaries extending from the arcuate eminence to the petrous apex. The posterior surface is a continuation of the front part of the posterior cranial fossa with the internal auditory meatus at its center. The inferior surface contains foramina that transmit important vessels and cranial nerves. The vascular anatomy of the petrous face is also described, including branches of the carotid artery and vertebrobasilar systems. It is imperative to understand potential anastomotic routes between extracranial and intracranial arteries, as well as arterial supply to cranial nerves, to facilitate preoperative transarterial embolization of meningiomas and avoid neurologic complications during surgery.

Recent surgical options for vestibular vertigo

Vertigo is not a well-defined disease but a symptom that can occur in heterogeneous entities diagnosed and treated mainly by otolaryngologists, neurologists, internal medicine, and primary care physicians. Most vertigo syndromes have a good prognosis and management is predominantly conservative, whereas the need for surgical therapy is rare, but for a subset of patients often the only remaining option. In this paper, we describe and discuss different surgical therapy options for hydropic inner ear diseases, Menière's disease, dehiscence syndromes, perilymph fistulas, and benign paroxysmal positional vertigo. At the end, we shortly introduce the most recent developments in regard to vestibular implants. Surgical therapy is still indicated for vestibular disease in selected patients nowadays when conservative options did not reduce symptoms and patients are still suffering. Success depends on the correct diagnosis and choosing among different procedures the ones going along with an adequate patient selection. With regard to the invasiveness and the possible risks due to surgery, in depth individual counseling is absolutely necessary. Ablative and destructive surgical procedures usually achieve a successful vertigo control, but are associated with a high risk for hearing loss. Therefore, residual hearing has to be included in the decision making process for surgical therapy.

Surgical Treatment for Recurrent Benign Paroxysmal Positional Vertigo

Introduction Benign paroxysmal positional vertigo is a generally benign condition that responds to repositioning maneuvers and frequently resolves spontaneously. However, for some patients it can become a disabling condition in which surgery must be considered. Two different surgical techniques exist, singular neurectomy and posterior semicircular canal occlusion. Objective The objective of this study is to review the current status of singular nerve section and posterior semicircular canal occlusion as treatments for intractable benign paroxysmal positional vertigo, and to determine if there are published data available that favors one over the other. Data Sources MEDLINE and OLDMEDLINE databases of the National Library of Medicine. Data Synthesis Four studies regarding singular neurectomy and 14 reports on semicircular canal occlusion were analyzed. Both techniques are reported to provide similar symptomatic benefit, with low risk of hearing loss and balance impairment. However, anatomical and clinical studies of singular neurectomy show it to be a more challenging technique, and considering that it is indicated in a very small number of cases, it may be difficult to master. Conclusions Both singular neurectomy and semicircular canal occlusion can be safe and effective in those few patients that require surgery for intractable positional vertigo. Although semicircular canal occlusion requires a postauricular transmastoid approach, it is ultimately easier to learn and perform adequately, and thus may be considered the best alternative.

Surgical Therapy in Intractable Benign Paroxysmal Positional Vertigo

OBJECTIVES: Benign paroxysmal positional vertigo (BPPV) is the most frequent vestibular disorder. Although it is easily cured with canal repositioning maneuvers for the majority of patients, it can be disabling in rare cases. For these patients, surgical solutions may be proposed. The aim of this article is to review the techniques used, the reported cases in the literature, and to discuss their indication in intractable BPPV.

STUDY DESIGN: Literature review.

MATERIALS AND METHODS: All the articles from 1972 to 2005 that discussed a specific surgical therapy in BPPV were reviewed. Many of them reported cases of operated patients and described original techniques. Some others are anatomic studies that discussed the two techniques used: singular neurectomy and posterior semicircular canal occlusion.

RESULTS: Singular neurectomy (posterior ampullary nerve transsection) and posterior semicircular canal occlusion are the 2 specific techniques used in intractable BPPV surgery. The numbers of operated cases are 342 and 97, respectively. These small numbers indicate that the procedures are difficult and risk compromising hearing and that a very small population of patients require surgical treatment of BPPV. The operated cases have been decreasing since the early 1990s because of improved management in BPPV. This article summarizes the techniques and their results and proposes a currently recommended practice of surgical therapy in BPPV as well as new insights into intractable BPPVs’ physiopathology.

Transcanal Approach to the Singular Nerve

OBJECTIVES/HYPOTHESIS

Intractable benign paroxysmal positional vertigo is rare, and surgery is indicated in only a very small number of cases. Transcanal singular neurectomy is considered a difficult and risky procedure possibly leading to hearing loss and vertigo. The objective of this study was to evaluate the feasibility of the singular neurectomy through the external ear canal in an attempt to explain the contradictory results of previous reports of anatomists and of surgeons who abandoned the technique, considering that the singular neurectomy could not be reached via the external auditory canal without damaging the labyrinth.

MATERIALS AND METHODS

Anatomical study on 100 halves of human heads in which the canal of the singular nerve (SN) was identified and opened at its extremities, the internal auditory canal and the ampulla of the posterior semicircular canal, via a posterior fossa approach. Next, the canal of the SN was dissected via the external auditory canal, at the floor of the round window (RW) niche. The relation of the SN canal to the ampulla of the posterior semicircular canal was evaluated.

RESULTS

In 90 cases, the canal was transected medially to and away from the ampulla of the posterior semicircular canal, and in 8, at its emergence from the posterior ampullary recess. In these 98 cases, the RW membrane and the bony labyrinth were kept intact. In two cases, the canal of the SN could not be reached at the floor of the RW niche.

CONCLUSION

Singular neurectomy is feasible via the external auditory canal, without damaging the RW membrane or the labyrinth in 98% of the cases. Because singular neurectomy is indicated in a very small number of cases, it is difficult to master this particular surgical procedure. This may explain why most surgeons abandoned the technique after a few attempts, followed by an unacceptable rate of sensorineural hearing loss.

CT of the normal temporal bone: comparison of multi- and single-detector row CT

PURPOSE

To evaluate multi- and single-detector row computed tomographic (CT) depiction of anatomic landmarks of temporal bone.

MATERIALS AND METHODS

Institutional review board approval and written informed consent were obtained. In 50 temporal bones, transverse and coronal single-detector row CT images were compared with transverse and reformatted coronal multi-detector row CT images obtained of additional 50 temporal bones. Two radiologists evaluated images. Visibility of 50 landmarks was scored with a five-point quality rating scale. Fisher exact test, kappa statistics, and Mann-Whitney U test were used to evaluate imaging technique and landmark visibility.

RESULTS

In delineating landmarks, total interobserver agreement was higher (P < .001) for transverse multi- than for single-detector row CT images. In 60% of landmarks, interobserver agreement was higher (P < .001) for transverse multi- than for single-detector row CT images. In 20% of landmarks, there was no difference, and in another 20% of landmarks, interobserver agreement was higher (P < .01) for single-detector row CT. Total interobserver agreement was higher (P < .01) for coronal multi-detector row reformations than for coronal single-detector row images. In 58% of landmarks, interobserver agreement was higher (P < .001) for coronal multi-detector row reformations than for coronal single-detector row images, while there was no difference in 8%. In 34% of landmarks, interobserver agreement was higher (P < .001) for coronal single-detector row images. Frequency of detected landmarks was higher for transverse (82%) and coronal (88%) multi-detector row images than for corresponding single-detector row images. In 72% of landmarks, transverse multi-detector row images were (P < .05) superior to corresponding transverse single-detector row images in landmark delineation. In 56% of landmarks, reformatted coronal multi-detector row images were (P < .05) superior to coronal single-detector row images in landmark delineation.

CONCLUSION

Multi-detector row CT images, including reformations, better delineate temporal bone anatomy than do single-detector row CT images.

Long-term results of posterior semicircular canal occlusion for intractable benign paroxysmal positional vertigo

Benign paroxysmal positional vertigo (BPPV) is a common condition which is usually managed conservatively, surgical intervention being recommended only for those small number of patients in whom it becomes persistent and incapacitating. The results of surgery in 13 patients who underwent posterior semicircular canal occlusion for intractable (> 12 months duration) and incapacitating BPPV are presented with special emphasis on their long-term follow-up. The mean follow-up was 66 months (range, 29-119 months). All patients reported complete and immediate resolution of their positional vertigo, which has been maintained in the long term. Most patients, however, reported some postoperative transient unsteadiness which lasted up to 4 weeks. All patients developed a transient mild conductive hearing loss secondary to a middle ear collection, which usually resolved within 4 weeks. Five patients developed a transient mild high frequency sensorineural hearing loss which resolved in all cases within 6 months. There were no reports of sensorineural hearing loss nor tinnitus in the long term. All patients believed that the operation was beneficial and would undergo it again. Our findings indicate that posterior semicircular canal occlusion is an effective and safe operation in the long term and is the procedure of choice for intractable and incapacitating BPPV rather than singular neurectomy.