Functional DTI tractography in brainstem cavernoma surgery

Abstract

OBJECTIVESurgical resection of brainstem cavernomas is associated with high postoperative morbidity due to the density of local vulnerable structures. Classical mapping of pathways by diffusion tensor imaging (DTI) has proven to be unspecific and confusing in many cases. In the current study, the authors aimed to establish a more reliable, specific, and objective method for somatotopic visualization of the descending motor pathways with navigated transcranial magnetic stimulation (nTMS)–based DTI fiber tracking.METHODSTwenty-one patients with brainstem cavernomas were examined with nTMS prior to surgery. The resting motor threshold (RMT) and cortical representation areas of hand, leg, and facial function were determined on both hemispheres. Motor evoked potential (MEP)–positive stimulation spots were then set as seed points for tractography. Somatotopic fiber tracking was performed at a fractional anisotropy (FA) value of 75% of the individual FA threshold.RESULTSMapping of the motor cortex and tract reconstruction for hand, leg, and facial function was successful in all patients. The somatotopy of corticospinal and corticonuclear tracts was also clearly depicted on the brainstem level. Higher preoperative RMT values were associated with a postoperative motor deficit (p < 0.05) and correlated with a lower FA threshold (p < 0.05), revealing structural impairment of the corticospinal tract (CST) prior to surgery. In patients with a new deficit, the distance between the lesion and CST was below 1 mm.CONCLUSIONSnTMS-based fiber tracking enables objective somatotopic tract visualization on the brainstem level and provides a valuable instrument for preoperative planning, intraoperative orientation, and individual risk stratification. nTMS may thus increase the safety of surgical resection of brainstem cavernomas.

Experience and Balance: Long-Term Trends in Preferred Skull Base Approach for a Case Series of Cavernous Malformation Resections

“…CMs, especially BSCMs, can be devastating, given the impact that multiple hemorrhages may have on critical structures in a neuroanatomically dense and eloquent region. 24,25 Furthermore, in contrast to benign skull base neoplasms, for which the risks associated with aggressive resection are considerable and little is gained for local control given the compelling outcomes associated with adjuvant stereotactic radiosurgery, microsurgical resection is the only curative treatment for BSCMs. This reality is emphasized by the failed attempts at both the primary and adjuvant medical and radiotherapeutic strategies for BSCMs.…”

“…CMs, especially BSCMs, can be devastating, given the impact that multiple hemorrhages may have on critical structures in a neuroanatomically dense and eloquent region. 24,25 Furthermore, in contrast to benign skull base neoplasms, for which FIGURE 5. Comparator set of orbitozygomatic and pterional approaches highlighting an example of 2 CMs in a similar location.…”

Impaired phase synchronization of motor‐evoked potentials reflects the degree of motor dysfunction in the lesioned human brain

“…Additionally, time‐frequency‐based motor mapping could assist in delineating the “cortical origin” of the CST. There is good evidence that information derived from TMS‐based tractography helps to prevent postoperative deficits after neurosurgical interventions, such as brain (Rosenstock, Grittner, et al, 2017; Rosenstock et al, 2021; Sollmann et al, 2018) or brainstem surgeries (Zdunczyk, Roth, Picht, & Vajkoczy, 2021). Furthermore, postoperative information about the CST status could improve the prediction of functional outcome after brain surgery (Ille et al, 2021; Rosenberg et al, 2010).…”