Optical neuronavigation facilitates transcranial surgical access to the equine pituitary gland.

Overview

• This study investigated the use of optical neuronavigation to guide transcranial surgical access to the equine pituitary gland.
• It compared the effectiveness of MRI versus CT imaging for guiding pituitary tissue biopsies and evaluated two biopsy tools: an automated morcellation device and a standard biopsy needle.

Background and Objectives

• Equine pituitary pars intermedia dysfunction is a common endocrine disorder in horses that may benefit from surgical treatment, such as hypophysectomy (removal of the pituitary gland).
• Accessing the pituitary gland in horses is challenging due to its location deep within the skull.
• The study aimed to assess the feasibility of an optical neuronavigation system to guide the transcranial (through the skull) surgical approach specifically to the equine pituitary gland.
• Two main imaging techniques—MRI and CT—were compared to determine which better supports accurate navigation for pituitary biopsies.
• Additionally, the study evaluated an automated tissue resection device (morcellator and aspiration device) versus a standard biopsy needle for obtaining pituitary tissue samples.

Methods

• Thirteen equine cadaver heads from euthanized horses were used for the experiments.
• A fiducial array (reference markers) was attached to each head’s frontal bone for image registration and neuronavigation purposes.
• Imaging was performed:
  • 7 heads underwent computed tomography (CT)
  • 6 heads underwent magnetic resonance imaging (MRI)
• Imaging data were imported into a neuronavigation system to create 3D reconstructions, plan the surgical path, and register the system to the physical head.
• Biopsy procedures:
  • 18 pituitary biopsy samples were collected in total.
  • Two biopsy techniques were compared:
    • Automated morcellation and aspiration device (used 7 times)
    • Standard biopsy needle (used 11 times)
  • In the 6 MRI-guided heads, both techniques were applied (paired design) for direct comparison.
• Histological examination:
  • All biopsy samples were stained with hematoxylin and eosin to confirm the presence of pituitary tissue.
  • A veterinary pathologist blinded to the biopsy technique and imaging modality assessed the tissue samples.

Results

• Overall success at obtaining pituitary tissue was 53.8% (7 out of 13 heads).
• Imaging modality comparison:
  • MRI guidance was significantly more effective: pituitary tissue was confirmed in all 6 MRI-guided heads (100%).
  • CT-guided biopsy was successful in only 1 of 7 heads (14.3%).
• Biopsy technique comparison in MRI-guided heads:
  • The automated morcellation device yielded pituitary tissue in 4 of 6 heads (66.7%).
  • The standard biopsy needle yielded pituitary tissue in 2 of 6 heads (33.3%).
  • This suggests the automated tool improved tissue acquisition over the standard needle when guided by MRI.

Conclusions and Implications

• Optical neuronavigation successfully enabled a feasible transcranial surgical approach to the equine pituitary gland in cadaver specimens.
• MRI guidance significantly improved the accuracy of tissue acquisition compared to CT guidance.
• The automated morcellation and aspiration device was more effective than the standard biopsy needle for sampling pituitary tissue when MRI guidance was used.
• These promising results support the potential for neuronavigation-guided hypophysectomy as a treatment option for equine pituitary pars intermedia dysfunction.
• Further research is warranted to explore clinical applications of this technique in live horses and to optimize surgical tools and protocols.