title: Endoscopic endonasal medial-to-lateral and transorbital lateral-to-medial optic nerve decompression: an anatomical study with surgical implications.
abstract: OBJECTIVE Different surgical routes have been used over the years to achieve adequate decompression of the optic nerve in its canal including, more recently, endoscopic approaches performed either through the endonasal corridor or the transorbital one. The present study aimed to detail and quantify the amount of bone removal around the optic canal, achievable via medial-to-lateral endonasal and lateral-to-medial transorbital endoscopic trajectories. METHODS Five human cadaveric heads (10 sides) were dissected at the Laboratory of Surgical Neuroanatomy of the University of Barcelona (Spain). The laboratory rehearsals were run as follows: 1) preliminary preoperative CT scans of each specimen, 2) anatomical endoscopic endonasal and transorbital dissections and Dextroscope-based morphometric analysis, and 3) quantitative analysis of optic canal bone removal for both endonasal and transorbital endoscopic approaches. RESULTS The endoscopic endonasal route permitted exposure and removal of the most inferomedial portion of the optic canal (an average of 168°), whereas the transorbital pathway allowed good control of its superolateral part (an average of 192°). Considering the total circumference of the optic canal (360°), the transorbital route enabled removal of a mean of 53.3% of bone, mainly the superolateral portion. The endonasal approach provided bone removal of a mean of 46.7% of the inferomedial aspect. This result was found to be statistically significant (p < 0.05). The morphometric analysis performed with the aid of the Dextroscope (a virtual reality environment) showed that the simulation of the transorbital trajectory may provide a shorter surgical corridor with a wider angle of approach (39.6 mm; 46.8°) compared with the simulation of the endonasal pathway (52.9 mm; 23.8°). CONCLUSIONS Used together, these 2 endoscopic surgical paths (endonasal and transorbital) may allow a 360° decompression of the optic nerve. To the best of the authors' knowledge, this is the first anatomical study on transorbital optic nerve decompression to show its feasibility. Further studies and, eventually, surgical case series are mandatory to confirm the effectiveness of these approaches, thereby refining the proper indications for each of them.
authors: Division of Neurosurgery, Department of Neurosciences, Reproductive and Odontostomatological Sciences, Università degli Studi di Napoli Federico II, Naples.
authors: Alberto
authors: A
authors: Di Somma
authors: Division of Neurosurgery, Department of Neurosciences, Reproductive and Odontostomatological Sciences, Università degli Studi di Napoli Federico II, Naples.
authors: Luigi Maria
authors: LM
authors: Cavallo
authors: Department of Neuroscience, G. Rummo Hospital, Neurosurgery Operative Unit, Benevento, Italy.
authors: Matteo
authors: M
authors: de Notaris
authors: Division of Neurosurgery, Department of Neurosciences, Reproductive and Odontostomatological Sciences, Università degli Studi di Napoli Federico II, Naples.
authors: Domenico
authors: D
authors: Solari
authors: Department of Neurosurgery, Hospital Clinic, Faculty of Medicine.
authors: Thomaz E
authors: TE
authors: Topczewski
authors: Rhinology and Skull Base Unit, Department of Otorhinolaryngology, Hospital Clínic de Barcelona; and.
authors: Manuel
authors: M
authors: Bernal-Sprekelsen
authors: Department of Neurosurgery, Hospital Clinic, Faculty of Medicine.
authors: Joaquim
authors: J
authors: Enseñat
authors: Laboratory of Surgical Neuroanatomy, Faculty of Medicine, Universitat de Barcelona, Spain.
authors: Alberto
authors: A
authors: Prats-Galino
authors: Division of Neurosurgery, Department of Neurosciences, Reproductive and Odontostomatological Sciences, Università degli Studi di Napoli Federico II, Naples.
authors: Paolo
authors: P
authors: Cappabianca
mesh_terms: D002102:Cadaver; D019299:Decompression, Surgical / Q000379:methods*; D006801:Humans; D057605:Natural Orifice Endoscopic Surgery; D044583:Neuroendoscopy / Q000379:methods*; D019635:Neurosurgical Procedures / Q000379:methods*; D009666:Nose; D009900:Optic Nerve / Q000033:anatomy & histology* / Q000601:surgery*
keywords: endoscopic endonasal, anatomy; endoscopic transorbital; optic nerve decompression; superior eyelid transorbital