Facial nerve sacrifice in lateral approaches to the skull base: Simultaneous reconstruction by graft interposition

Contemporary Perspectives in Pathophysiology of Facial Nerve Damage in Oto-Neurological and Skull Base Surgical Procedures: A Narrative Review

“…At the same time, in patients whose facial nerve was anatomically discontinued and reconstructed with cable graft, a House-Brackmann grade III was achieved in up to 61-70% of cases [14]. The discrepancy between anatomical and functional preservation rates has also been highlighted in the more recent literature [5,15]; it might be explained by the multiple mechanical traumas caused to the FN over its whole intracranial length during surgical dissection despite a gross anatomical preservation.…”

“…Over the past decades in vestibular schwannoma surgery, an increasing level of ana tomical knowledge, refinement of surgical techniques [1], accurate planning of surgica corridors [2], as well as the implementation of nerve monitoring systems, have led to great improvement in FN outcomes, in terms of both anatomical and functional preserva tion. Moreover, the evolution of diagnostic tools, leading to earlier diagnosis, has allowed smaller tumors to be detected, thus contributing to the improvement of such outcome since the opportunity of early surgery may lead to very favorable outcomes on the FN [1,5], and low-to-zero surgical morbidity. In their retrospective series of 1000 vestibula schwannomas surgically treated between 1978 and 1993, Sami and Matthies [13] reported an overall anatomical preservation rate of 93%, which was even higher when considering only patients operated on after the routine introduction of FN monitoring techniques However, the same study [13] also stated that the FN functional preservation rate (consid ered as House-Brackmann grade I or II) was lower than the anatomical preservation rate accounting for a subgroup of patients with an anatomically preserved nerve, but signifi cantly impaired function.…”

“…The onset of intraoperative FN damage in oto-neurological and skull base surgery is related to various aspects, mainly concerning the anatomical relationship between tumor and nerve, the trajectory of the surgical corridor, and the boundaries of the resection margins in the case of malignant diseases [4]. Although benign from a pathological viewpoint, the most frequent tumors of the cerebello-pontine angle, such as vestibular schwannoma, meningiomas, and epidermoid cysts, in some cases display tight adherence to the FN, thus causing technical difficulties in finding a cleavage, and increasing the risk of nerve damage during dissection [5].…”

“…Particularly in vestibular schwannoma surgery, the FN preservation rate is negatively correlated to tumor dimensions [5,6]. Large tumors are associated with an increased risk of nerve damage because of the variable extent of nerve fiber involvement, which causes mechanical stress during surgical maneuvers of dissection.…”

“…Large tumors are associated with an increased risk of nerve damage because of the variable extent of nerve fiber involvement, which causes mechanical stress during surgical maneuvers of dissection. In skull base surgery, FN anatomy renders the nerve itself intrinsically at risk of traction damage, especially while working at the interface between the extensible part (the cisternal tract) and the inextensible one (labyrinthic tract), which is fully constrained within the bony fallopian canal [5,6]. Moreover, the anatomical relationship of the intracranial FN, from its root exit zone to its intrameatal tract, with major vascular structures, including the antero-inferior and (less frequently) posterior-inferior cerebellar arteries, makes surgical dissection difficult at these points, while extensive coagulation of the vasa nervorum may lead to ischemic damage [7].…”