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Comparative Study
. 2025 Dec 22;167(1):334.
doi: 10.1007/s00701-025-06752-9.

Comparison between olfactory bulb and olfactory tract implantations through an endoscopic supraorbital keyhole approach: a cadaveric study

Hakim Benkhatar  1   2 , Douglas Henderson  3 , Teofil Mures  4   5 , Claire Martin  6 , Damien Bresson  4   5   7
Affiliations
Comparative Study

Comparison between olfactory bulb and olfactory tract implantations through an endoscopic supraorbital keyhole approach: a cadaveric study

Hakim Benkhatar et al. Acta Neurochir (Wien). .

Abstract

Purpose: Since the COVID-19 pandemic, olfactory loss has been recognized as a highly prevalent condition that greatly impacts the quality of life. Similar to other sensory implants, the idea of an olfactory implant has emerged. Evidence indicates that electrical stimulation of specific olfactory structures can evoke smell sensations. However, debates on the most appropriate anatomical target and surgical technique for implantation are still ongoing. By extrapolating data from other surgical indications, transcranial approaches appear to carry a lower risk of cerebrospinal fluid leakage and infection compared with endoscopic endonasal routes. The aim of this study was to compare two electrode placements (dorsal olfactory bulb and ventral olfactory tract) through a supraorbital keyhole craniotomy in human cadavers.

Method: Four fresh human cadavers were dissected in a staged manner. Supraorbital keyhole craniotomy was performed through an eyebrow incision and the frontal lobe was slightly retracted to allow angled (30°) endoscope insertion. An auditory brainstem implant (ABI) from MED-EL was used for electrode placement.

Results: Endoscopic placement of the electrode on the dorsal side of the olfactory bulb was achieved after orbital roof drilling in all cases, but was not stable. On the contrary, endoscopic placement of an electrode under the olfactory tract was easily achieved without drilling and the electrode was stable between the olfactory tract and the planum sphenoidale, behind the olfactory bulb.

Conclusion: Ventral olfactory tract implantation posterior to the olfactory bulb using an ABI is straightforward and is associated with satisfactory electrode stability. Such a procedure could be used for clinical pilot studies evaluating the effects of various stimulation protocols on the olfactory tract in patients with long-lasting olfactory loss.

Keywords: Neurostimulation; Olfactory bulb; Olfactory implant; Olfactory loss; Olfactory tract; Supraorbital keyhole craniotomy.

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Conflict of interest statement

Declarations. Ethical approval: This cadaveric study has been approved by the ethical comity of the the Fer à Moulin School of Surgery. Disclosure: No relationship that may pose a conflict of interest exist for the authors. Competing interests: The authors declare no competing interests.

Figures

Fig. 1
Fig. 1
Illustration of supraorbital approach to the homolateral olfactory bulb and tract. A supraorbital craniotomy, B, C, D Access (red arrow) to the olfactory bulb (*) and access (green arrow) to the olfactory tract (O)
Fig. 2
Fig. 2
Supraorbital keyhole approach through a suprabrow incision. 1: Supraorbital notch outlined, 2: Craniotomy exposing the dura mater
Fig. 3
Fig. 3
Mi1000 DEMO auditory brainstem implant (MED-EL) and its 12-contact electrode array (measuring 5.5 x 3 mm)
Fig. 4
Fig. 4
Olfactory bulb and tract implantation. A Endoscopic placement of the electrode on the dorsal olfactory bulb, B Illustration of corridors (green arrows) from the supraorbital craniotomy to the olfactory bulb and tract. An ABI electrode (black arrow) is placed under the anterior olfactory tract, C Endoscopic placement of the electrode under the anterior olfactory tract, D Olfactory tract in contact with the optic nerve posteriorly. 1: Corridor to the olfactory bulb, 2: Corridor to the anterior olfactory tract, 3: Corridor to the intermediate olfactory tract, 4: Olfactory tract, 5: Olfactory bulb, 6: Crista galli, 7: Frontal lobe, 8: Orbital roof, 9: Optic nerve
Fig. 5
Fig. 5
Illustration of the anatomical divide within the olfactory bulb [19] and the ventral olfactory tract, up to the olfactory striae. 1: Medial olfactory bulb, 2: Medial olfactory tract, 3: Medial olfactory stria, 4: Lateral olfactory bulb, 5: Lateral olfactory tract, 6: Lateral olfactory stria
See this image and copyright information in PMC

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