Introduction

Awake surgery for gliomas of the left insula, while crucial for preserving cognitive function, can result in transient language deficits, particularly severe naming disorders. A recent study examined the links between these deficits and the appearance of mini-strokes in the connections between Broca’s area and the caudate nucleus.

Objective

Understanding the intraoperative occurrence of severe naming deficits during awake resection of left insula gliomas.

Methodology

This retrospective study analyzed 14 patients operated on under awake conditions for IDH-mutated left insula glioma. Key milestones included:

• Preoperative imaging: High-resolution MRI with diffusion sequences generated a complete brain tractogram using the constrained spherical deconvolution method.
• Cerebral parcellation: Freesurfer was used to identify connections between the caudate nucleus and Broca’s area.
• Post-operative MRI: Performed the day after surgery, this enabled areas of diffusion hyperintensity associated with mini-strokes to be detected and recorded on the pre-operative MRI.
• Language assessment: Certified speech therapists assessed patients’ naming abilities before, during and after the intervention. A severe deficit was defined as a score below 40/80 items.

Data were analyzed using Fisher’s exact test, with statistical significance set at 0.05.

Results

Of the 14 patients studied :

• Mini-strokes detected: 8 patients had a mini-stroke on immediate postoperative MRI.
• Link to severe deficits:
  • None of the 6 stroke-free patients showed severe naming deficits.
  • 5 of the 8 patients with mini-stroke showed severe deficits, marked by strong verbal perseverations.
  • Mini-strokes involving the pars triangularis – caudate or pars opercularis – caudate pathways were significantly associated with these deficits(p = 0.03).

However, all patients recovered near-normal naming abilities at 4 months post-surgery.

Conclusion

Mini-strokes in the connections between Broca’s area and the caudate nucleus explain the sudden onset of naming deficits during awake resection of left insula gliomas. These results underline the importance of anticipating these events to minimize their impact, not only on language, but also on other cognitive functions.

Outlook

Further studies are needed to better predict these mini-strokes, improve cortical mapping techniques and explore the consequences on other brain functions.