Role of Diffusion MRI Tractography in Endoscopic Endonasal Skull Base Surgery

Summary

We present a protocol to integrate diffusion MRI tractography in patient work-up to endoscopic endonasal surgery for a skull base tumor. The methods for adopting these neuroimaging studies in the pre- and intra-operative phases are described.

Abstract

Endoscopic endonasal surgery has gained a prominent role in the management of complex skull base tumors. It allows the resection of a large group of benign and malignant lesions through a natural anatomical extra-cranial pathway, represented by the nasal cavities, avoiding brain retraction and neurovascular manipulation. This is reflected by the patients' prompt clinical recovery and the low risk of permanent neurological sequelae, representing the main caveat of conventional skull base surgery. This surgery must be tailored to each specific case, considering its features and relationship with surrounding neural structures, mostly based on preoperative neuroimaging. Advanced MRI techniques, such as tractography, have been rarely adopted in skull base surgery due to technical issues: lengthy and complicated processes to generate reliable reconstructions for inclusion in the neuronavigation system.

This paper aims to present the protocol implemented in the institution and highlights the synergistic collaboration and teamwork between neurosurgeons and the neuroimaging team (neurologists, neuroradiologists, neuropsychologists, physicists, and bioengineers) with the final goal of selecting the optimal treatment for each patient, improving the surgical results and pursuing the advancement of personalized medicine in this field.

Introduction

The possibility to approach the skull base midline and paramedian regions through an anterior route, adopting the nasal fossae as natural cavities, has a long history, dating back more than one century¹. However, in the last 20 years, the visualization and operative technologies have improved enough to expand their possibility of including the treatment of the most complex tumors such as meningiomas, chordomas, chondrosarcomas, and craniopharyngiomas¹ due to the (1) introduction of the endoscope, which gives a panoramic and detailed 2D/3D view of these regions to the surgeon, (2) the development of intraoperative neurona....

Protocol

The protocol is following the Local Research Committee's ethical standards and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.

1. Selection of the patients

1. Adopt the following inclusion criteria: patients older than 18 years old, fully collaborating, presenting a tumor of the skull base, or pituitary-diencephalic region.
2. Exclude patients with contraindication to MRI (i.e., a pacemaker or ferromagnetic material) or presenting with emergent clinical conditions (i.e., intracranial hypertension, the acute visual loss that requires immediate surgery), or pregnant women, or pa....

Results

A 55-year-old woman presented with progressive visual deficits. Her medical history was unremarkable. On ophthalmological evaluation, bilateral reduction of visual acuity (6/10 in the right eye and 8/10 in the left eye) was revealed, and the computerized visual field showed complete bitemporal hemianopia. No further deficits were evident on neurological examination, but the patient reported persistent asthenia and an increase in hunger and thirst sensation in the previous 2-3 months, with.......

Discussion

The application of the presented protocol resulted in a safe and effective treatment of one of the most challenging intracranial tumors such as a craniopharyngioma invading the 3^rd ventricle, possibly opening up a new horizon for a lesion that was defined by H. Cushing about a century ago as the most baffling intracranial neoplasm¹. The combination of accurate preoperative planning, integrating advanced MRI techniques, and multidisciplinary clinical assessments have permitted us to tail.......

Materials

Name	Company	Catalog Number	Comments
BRAF V600E-specific clone VE1	Ventana
Dural Substitute	Biodesign, Cook Medical
Endoscope	Karl Storz, 4mm in diameter, 18 cm in length, Hopkins II – Karl Storz Endoscopy
Immunohistochemical staining instrument	Ventana Benchmark, Ventana Medical Systems
MRI	3T Magnetom Skyra, Siemens Health Care
Neuronavigator	Stealth Station S8 Surgical Navigation System, MEDTRONIC