Priming of head premotor circuits during oculomotor preparation

Large, rapid gaze shifts necessitate intricate coordination of the eyes and head. Brief high-frequency bursts of activity within the intermediate and deeper layers of the superior colliculus (dSC) encode desired gaze shifts regardless of component movements of the eyes and head. However, it remains unclear whether low-frequency activity emitted by oculomotor neurons within the dSC and elsewhere has any role in eye-head gaze shifts. Here we test the hypothesis that such low-frequency activity contributes to eye-head coordination by selectively priming head premotor circuits. We exploited the capacity for short-duration (10 ms, 4 pulses) dSC stimulation to evoke neck muscle responses without compromising ocular stability, stimulating at various intervals of a "gap-saccade" task. Low-frequency neural activity in many oculomotor areas (including the dSC) is known to increase during the progression of the gap-saccade task. Stimulation was passed during either a fixation-interval while a central fixation point was illuminated, a 200-ms gap-interval between fixation point offset and target onset, or a movement-interval following target onset. In the two monkeys studied, the amplitude of evoked responses on multiple neck muscles tracked the known increases in low-frequency oculomotor activity during the gap-saccade task, being greater following stimulation passed at the end of the gap- versus the fixation-interval, and greater still when the location of stimulation during the movement interval coincided with the area of the dSC generating the ensuing saccade. In one of these monkeys, we obtained a more detailed timeline of how these results co-varied with low-frequency oculomotor activity by stimulating, across multiple trials, at different times within the fixation-, gap- and movement-intervals. Importantly, in both monkeys, baseline levels of neck EMG taken immediately prior to stimulation onset did not co-vary with the known pattern of low-frequency oculomotor activity up until the arrival of a transient burst associated with visual target onset. These baseline results demonstrate that any priming of the head premotor circuits occurs without affecting the output of neck muscle motoneurons, We conclude that low-frequency oculomotor activity primes head premotor circuits well in advance of gaze shift initiation, and in a manner distinct from its effects on the eye premotor circuits. Such distinctions presumably aid the temporal coordination of the eyes and head despite fundamentally different biomechanics.     

Author’s Reply: Single Dose Steroid Injection After Loss of Signal (LOS) During Thyroid Surgery is Effective to Recover Electric Signal Avoiding Vocal Cord Palsy and the Need of Staged Thyroidectomy: Prospective Evaluation on 702 Patients

World Journal of Surgery -     

Bevacizumab Doubles the Early Postoperative Complication Rate after Cytoreductive Surgery with Hyperthermic Intraperitoneal Chemotherapy (HIPEC) for Peritoneal Carcinomatosis of Colorectal Origin

Background

Patients with stage IV colorectal cancer and peritoneal carcinomatosis are increasingly treated with curative intent and perioperative systemic chemotherapy combined with targeted therapy. The aim of this study was to analyze the potential impact of bevacizumab on early morbidity after cytoreductive surgery with hyperthermic intraperitoneal chemotherapy (HIPEC) in patients with peritoneal carcinomatosis of colorectal origin.

Methods

From 2004 to 2010, in three referral centers, 182 patients with colorectal carcinomatosis were treated with complete cytoreduction followed by HIPEC after either preoperative systemic chemotherapy alone or in combination with bevacizumab. Because there was no control on treatment allocation, propensity score methods were used to control for this bias.

Results

The median time from discontinuation of bevacizumab to HIPEC was 7 weeks (range 6–10 weeks). Major morbidity was greater in the bevacizumab group (34 vs. 19 %, p = 0.020). Nine patients died postoperatively, 5 (6.2 %) in the bevacizumab group (n = 80) and 4 (3.9 %) in the group treated with chemotherapy alone (n = 102) (p = 0.130). The rate of digestive fistulas was greater in the bevacizumab group, although not statistically significant (18 vs. 10 %, p = 0.300). The effect of bevacizumab on major morbidity (including death) was found to be statistically significant (odds ratio 2.28, 95 % confidence interval 1.05–4.95) (p = 0.04).

Conclusions

Administration of bevacizumab before surgery with complete cytoreduction followed by HIPEC for colorectal carcinomatosis is associated with twofold increased morbidity. The oncologic benefit of bevacizumab before HIPEC remains to be evaluated.