Despite attempts to preserve cortical areas of function during awake craniotomy procedures, postoperative neurologic decline still occurs as a result of subcortical injury, report researchers.
"Subcortical injury is the primary cause of neurological deficits following awake craniotomy procedures," write Victoria Trinh (University of Texas, Houston) and colleagues in Neurosurgery.
The team conducted a retrospective review of 214 patients who underwent awake craniotomy for brain tumors and assessed post-operative changes in cortical versus subcortical areas using diffusion-weighted magnetic resonance-imaging (DWI).
Patients with preoperative motor or language deficits had a threefold increased chance for developing new or exacerbated neurologic dysfunction compared with patients without any preoperative deficits. Patients who intraoperatively acquired such deficits during subcortical dissection were over six times more likely to have worsened neurologic function 3 months later.
Regression analysis showed that three parameters predicted the risk for neurologic deficit 3 months following surgery. A patient without preoperative or subcortical dissection deficit who did not have any subcortical grade III DWI changes had only a 5% risk for worsened neurologic deficits. By contrast, a patient who was positive for all three parameters had a 90% risk.
Grade III DWI changes predicted either a persistent deficit that did not resolve at 3 months or a slower functional recovery, with most lesions occurring in the eloquent subcortical fiber tracts. Compared with grade I or grade II, subcortical grade III DWI changes significantly predicted postoperative neurologic deficits immediately and 3 months after surgery, with an eight times greater likelihood for persistently worsened neurologic function.
The location of the lesion was found to be as significant in the DWI grading system as volume. DWI lesions that did not correspond to major structures, such as eloquent areas, were thus given a grade II, which was useful in predicting post-operative deficit severity.
"Preserving subcortical areas during tumor resections may reduce the severity of both immediate and late neurological sequelae," Trinh et al conclude.
They add that Grade III DWI changes occurring mostly in eloquent subcortical areas "underscores the importance of both subcortical injury as an independent predictor of persistent postoperative deficits, and of subcortical mapping as a technique for complication avoidance."
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