Cortico-spinal fiber tracking

Applications: Brain tumour surgery, epilepsy surgery, cerebrovascular surgery, radiation therapy

Functional seed points for DTI-fiber tracking

There is variability in the accurate demarcation of descending white matter fibers of the corticospinal tract, which doesn't always respect the classical course in the context of complex and diffuse neoplasms such as gliomas, which are capable of displacing or infiltrating white matter and often causing functional reorganisation (or plasticity).

Some DTI analyses incorporate the precentral gyrus origin only, and others will include premotor and postcentral portions, though the main drawback in this method is the choice of anatomic seed points for the subsequent computation of the CST.

The use of nTMS DTI-FT has been shown to improve visualisation of the CST in brain tumour patients, in which anatomical distortion caused by mass effect and neuroplasticity reduces the reliability of standard DTI-FT nTMS also permits the somatotopic organisation of the motor cortex, objectively distinguishing between the cortical representation of the face, arm, and leg muscles.

How?

  • Pre-op motor mapping conducted within 48 hours prior to the planned procedure.

  • Diffusion-weighted imaging (DWI) sequences are imported with the nTMS map of the motor cortex and MRI scan into navigation software (Medtronic, Brainlab, Stryker)

  • DWI is co-registered with the MRI and nTMS data and used to compute the DTI-FT

  • Subject to region of interest (ROI), the directionally encoded colour (DEC) maps are calculated for the lesion-occupying hemisphere

  • Individual computation of the DTI tractography is computed for each CST fiber bundle using the anterolateral portion of the ipsilateral cerebral peduncle as the first ROI and each somatotopically different motor cortex areas as the second ROI.

  • DTI-FT is then calculated using tracking algorithms with specific parameters, which cater to the directional changes of each fiber bundle

  • This data is then verified and matched with intraoperative cortical and subcortical mapping

Hospital purchase of Nexstim NBS

In-house:

Referral for patient MRI

Outsourced:

Patient books appointment with Neuroclast

En-TMS conducted by Neuroclast

Data sent to consultant surgeon for analysis

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Motor fiber tracking with face, arm, leg tractography, using functional seed points which can cater to displaced or infiltrated white matter tracts (source: Nikolenko & Picht, 2017).

En-TMS conducted by Neuroclast can be included in multiple multi-centre trials throughout Australia. Consent will be sought prior to any data capture, and acquired from the patient, consultant and hospital.

Recommended Reading

  • Chapter 6. Nikolenko, O. & Picht, T. (2017). Navigated TMS in Neurosurgery. 97-115.

  • Haddad et al. (2021). Preoperative applications of navigated transcranial magnetic stimulation. Frontiers in Neurology, 11, 1-11.

For patients:

Surgical procedures of any description pose risk. This is a safe and non-invasive measure to distinguish how close or far the areas of the brain are with respect to your procedure. Just because you're here reading this does not mean that you're in immediate danger whatsoever, in fact, this is a proactive and preventative measure to ensure that all possible data is acquired to contribute to a safe procedure.

When you schedule an appointment with Neuroclast, you'll be greeted and given an overview of the technology and what's in store. Here's a brief summary to get you ahead:

  • You'll enter our clinic, and see a big fancy piece of equipment

  • You'll sit in a comfortable chair and engage in banter with our clinical specialists

  • We'll load up your MRI scan, and find the 'target' areas necessary for mapping

  • If it puts you at ease, we'll show you how it works first!

  • You will hear occasional semi-loud clicks, and at times you may feel a twitch - all is perfectly normal

  • The test takes between 25-40 minutes, and then you're good to go!

  • We'll forward your data to your surgeon