Tag: brainstem cavernoma

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Functional DTI tractography in brainstem cavernoma surgery

J Neurosurg 135:712–721, 2021

Surgical 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.

METHODS Twenty-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.

RESULTS Mapping 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.

CONCLUSIONS nTMS-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.

 

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Brainstem cavernoma surgery with the support of pre and postoperative diffusion tensor imaging

Brainstem cavernoma surgery

Neurosurg Rev (2014) 37:481–492

The spatial complexity of highly vulnerable structures makes surgical resection of brainstem cavernomas (BSC) a challenging procedure. Diffusion tensor imaging (DTI) allows for the visualization of white matter tracts and enables a better understanding of the anatomical location of corticospinal and sensory tracts before and after surgery.

We investigated the feasibility and clinical usefulness of DTI-based fiber tractography in patients with BSC.Pre- and postoperative DTI visualization of corticospinal and sensory tracts were retrospectively analyzed in 23 individuals with BSC. Preoperative and postoperative DTIfiber accuracy were associated to the neurological findings.

Preoperatively, the corticospinal tracts were visualized in 90%of the cases and the sensory tracts were visualized in 74 % of the cases. Postoperatively, the corticospinal tracts were visualized in 97 % of the cases and the sensory tracts could be visualized in 80 % of the cases. In all cases, the BSC had caused displacement, thinning, or interruption of the fiber tracts to various degrees. Tract visualization was associated with pre- and postoperative neurological findings. Postoperative damage of the corticospinal tracts was observed in two patients. On follow-up, the Patzold Rating (PR) improved in 19 out of 23 patients (83 %, p= 0.0002).

This study confirms that DTI tractography allows accurate and detailed white matter tract visualization in the brainstem, even when an intraaxial lesion affects this structure. Furthermore, visualizing the tracts adjacent to the lesion adds to our understanding of the distorted intrinsic brainstem anatomy and it may assists in planning the surgical approach in specific cases.

 

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The presigmoid approach to anterolateral pontine cavernomas

J Neurosurg 113:701–708, 2010. DOI: 10.3171/2010.1.JNS08413

Anterolateral cavernomas of the pons have been surgically removed via a variety of approaches, commonly retrosigmoid or transventricular. The goal in this study was to evaluate the presigmoid approach as an alternative.

Methods. Clinical data were reviewed in 9 patients presenting with anterolateral pontine cavernomas between 1999 and 2007.

Results. All patients were treated via a presigmoid approach, which provided a nearly perpendicular trajectory to the anterolateral pons. The brainstem was entered through a “safe zone” between the trigeminal nerve and the facial/ vestibulocochlear nerve complex. Complete resection was achieved in all cases. No patient experienced recurrent events during follow-up (1–24 months). The patients’ modified Rankin Scale score improved within 1 year of surgery (1.7 ± 0.4) compared with baseline (2.6 ± 0.2; p < 0.05). Only one patient experienced a new deficit (decreased hearing), which was corrected with a hearing aid.

Conclusions. The presigmoid approach is recommended for the resection of anterolateral pontine cavernomas. With this approach, the need for cerebellar retraction is nearly eliminated. The lateral “presigmoid” entry point creates a trajectory that allows complete resection of even deep lesions at this level, or anterior to the internal acoustic meatus.

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