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John H. Sampson and Jenny K. Hoang

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Tejas Sankar, Nina Z. Moore, Joshua Johnson, Lynn S. Ashby, Adrienne C. Scheck, William R. Shapiro, Kris A. Smith, Robert F. Spetzler and Mark C. Preul

Object

Oligodendrogliomas that enhance on MR images are associated with poor prognosis. However, the importance of the volume of enhancing tumor tissue, and the extent of its resection, is uncertain. The authors examined the prognostic significance of preoperative and residual postoperative enhancing tissue volumes in a large single-center series of patients with oligodendroglioma. They also examined the relationship between enhancement and characteristic genetic signatures in oligodendroglial tumors, specifically deletion of 1p and 19q (del 1p/19q).

Methods

The authors retrospectively analyzed 100 consecutive cases of oligodendroglioma involving patients who had undergone T1-weighted gadolinium-enhanced MRI at diagnosis and immediately after initial surgical intervention. The presence of preoperative enhancement was determined by consensus. Preoperative and residual postoperative volumes were measured using a quantitative, semiautomated method by a single blinded observer. Intrarater reliability for preoperative volumes was confirmed by remeasurement in a subset of patients 3 months later. Intrarater and interrater reliability for residual postoperative volumes was confirmed by remeasurement of these volumes by both the original and a second blinded observer. Multivariate analysis was used to assess the influence of contrast enhancement at diagnosis and the volume of pre- and postoperative contrast-enhancing tumor tissue on time to relapse (TTR) and overall survival (OS), while controlling for confounding clinical, pathological, and genetic factors.

Results

Sixty-three of 100 patients had enhancing tumors at initial presentation. Presence of contrast enhancement at diagnosis was related to reduced TTR and OS on univariate analysis but was not significantly related on multivariate analysis. In enhancing tumors, however, greater initial volume of enhancing tissue correlated with shortened TTR (p = 0.00070). Reduced postoperative residual enhancing volume and a relatively greater resection of enhancing tissue correlated with longer OS (p = 0.0012 and 0.0041, respectively). Interestingly, patients in whom 100% of enhancing tumor was resected had significantly longer TTR (174 vs 64 weeks) and OS (392 vs 135 weeks) than those with any residual enhancing tumor postoperatively. This prognostic benefit was not consistently maintained with greater than 90% or even greater than 95% resection of enhancing tissue. There was no relationship between presence or volume of enhancement and del 1p/19q.

Conclusions

In enhancing oligodendrogliomas, completely resecting enhancing tissue independently improves outcome, irrespective of histological grade or genetic status. This finding supports aggressive resection and may impact treatment planning for patients with these tumors.

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Rachid Assina, Tejas Sankar, Nicholas Theodore, Sam P. Javedan, Alan R. Gibson, Kris M. Horn, Michael Berens, Volker K. H. Sonntag and Mark C. Preul

Object

Axonal regeneration may be hindered following spinal cord injury (SCI) by a limited immune response and insufficient macrophage recruitment. This limitation has been partially surmounted in small-mammal models of SCI by implanting activated autologous macrophages (AAMs). The authors sought to replicate these results in a canine model of partial SCI.

Methods

Six dogs underwent left T-13 spinal cord hemisection. The AAMs were implanted at both ends of the lesion in 4 dogs, and 2 other dogs received sham implantations of cell media. Cortical motor evoked potentials (MEPs) were used to assess electrophysiological recovery. Functional motor recovery was assessed with a modified Tarlov Scale. After 9 months, animals were injected with wheat germ agglutinin–horseradish peroxidase at L-2 and killed for histological assessment.

Results

Three of the 4 dogs that received AAM implants and 1 of the 2 negative control dogs showed clear recovery of MEP response. Behavioral assessment showed no difference in motor function between the AAM-treated and control groups. Histological investigation with an axonal retrograde tracer showed neither local fiber crossing nor significant uptake in the contralateral red nucleus in both implanted and negative control groups.

Conclusions

In a large-animal model of partial SCI treated with implanted AAMs, the authors saw no morphological or histological evidence of axonal regeneration. Although they observed partial electrophysiological and functional motor recovery in all dogs, this recovery was not enhanced in animals treated with implanted AAMs. Furthermore, there was no morphological or histological evidence of axonal regeneration in animals with implants that accounted for the observed recovery. The explanation for this finding is probably multifactorial, but the authors believe that the AAM implantation does not produce axonal regeneration, and therefore is a technology that requires further investigation before it can be clinically relied on to ameliorate SCI.

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Tejas Sankar, Rachid Assina, John P. Karis, Nicholas Theodore and Mark C. Preul

✓Mannitol is widely considered the hyperosmolar therapy of choice in routine neurosurgical practice for the reduction of intracranial pressure (ICP). The authors present a unique case of a patient with a large meningioma treated with mannitol, in which mannitol accumulation within the tumor and its surrounding parenchyma was shown using in vivo magnetic resonance spectroscopy (MRS). This rare appearance of mannitol on MRS was characterized by a wide-based peak at 3.8 ppm, which remained detectable several hours after the last dose. These findings provide the first in vivo evidence in support of the prevailing theory that mannitol leakage into the peritumoral edematous region may contribute to rebound increases in ICP and suggest that this phenomenon has the potential to occur in extraaxial tumors. Judicious use of mannitol in the setting of elevated ICP due to tumor may be indicated to avoid potentially deleterious side effects caused by its accumulation.