Parasagittal meningiomas (PSM) may pose a difficult surgical challenge since venous patency and collateral anastomoses have to be clearly defined for correct surgical planning. The aim of this study was to assess the diagnostic value of contrast-enhanced (CE) magnetic resonance venography (MRV) in the preoperative evaluation of venous infiltration and collateral venous anastomoses in patients with PSM. CE-MRV was compared with phase-contrast (PC) magnetic resonance (MR) angiography, conventional angiography (when available), and surgery as a reference. Twenty-three patients undergoing surgery for meningiomas located adjacent to the superior sagittal sinus were prospectively evaluated. All the patients underwent both conventional MR examination and MRV. This was performed by means of PC and CE techniques. Both sets of angiograms (CE and PC) were evaluated by two expert neuroradiologists to assess (1) patency of the sinus (patent/occluded), (2) the extent of occlusion (in centimeters), and (3) the number of collateral anastomoses close to the insertion of the meningioma. Eight patients underwent digital subtraction angiography (DSA). All patients were operated on, and intraoperative findings were taken as the gold standard to evaluate the diagnostic value of MRA techniques. PC-MRV showed a flow void inside the sinus compatible with its occlusion in 15 cases, whereas CE-MRV showed the sinus to be occluded in five cases. CE-MRV data were confirmed by surgery, showing five patients to have an occlusion of the superior sagittal sinus. The PC-MRV sensitivity was thus 100% with a specificity of 50%. In those cases in which both MRV techniques documented occlusion of the sinus, the extent of occlusion was overestimated by PC compared with CE and surgery. CE-MRV depicted 87% of collateral venous anastomoses close to the meningioma as subsequently confirmed by surgery, while PC showed 58%. In the preoperative planning for patients with meningiomas located close to a venous sinus, CE-MRV provides additional and more reliable information concerning venous infiltration and the presence of collateral anastomoses compared with PC sequences.
Diffusion-weighted imaging (DWI) has been shown to be highly sensitive in detecting acute cerebral infarction, but its use in detecting hypoxic-ischemic encephalopathy (HIE) in neonates is still controversial. Moreover, few reports concern pre-term infants with possible periventricular leukomalacia (PVL). We examined the ability of this technique to detect cerebral changes in the acute phase of PVL. Fifteen MR examinations were performed in 11 pre-term infants (mean age 3.4 days, range 2-6 days). Conventional DWI sequences, apparent diffusion coefficient (ADC) maps, and US obtained in the acute phase were compared. All the neonates underwent US follow-up up to 4 months after delivery; those with suspected PVL also underwent MRI follow-up for up to 2 months. Qualitative and quantitative evaluations were performed to assess the presence of DW changes compatible with PVL. Diffusion-weighted MRI showed signal hyperintensity associated with decreased ADC values in 3 subjects (27%). In these patients conventional MRI sequences were interpreted as normal and US (performed at the same time) as doubtful in 2 and compatible with PVL in 1 subject. The MRI and US follow-up confirmed severe damage in all these patients. In 1 neonate hemorrhages involving the germinative matrix were identified. In 8 neonates MRI was considered normal. In these subjects US follow-up (up to 4 months) confirmed no signs of PVL. Diffusion-weighted imaging may have a higher correlation with later evidence of PVL than does conventional MR imaging and US when performed in the acute phase of the disease.
Magnetic resonance (MR) tractography offers the neurosurgeon an anatomical panoramic view that can improve surgical planning for the resection of intracranial tumours. Despite the high incidence of cases in which the lesion is responsible for changes that hinder the reconstruction of white matter tracts, the technique can change the surgical approach for corticotomy, defines the extent of resection and leads to some change in the procedure in 80% of cases. The improvement of pre-existing symptoms and the absence of new symptoms in the postoperative phase, in our opinion, confirms the value of the technique.
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