We assume that between lateral geniculate and visual cortical cells there exist labile synapses that modify themselves in a new fashion called threshold passive modification and in addition, non-labile synapses that contain permanent information. In the theory which results there is an increase in the specificity of response of a cortical cell when it is exposed to stimuli due to normal patterned visual experience. Non-patterned input, such as might be expected when an animal is dark-reared or raised with eyelids sutured, results in a loss of specificity, with details depending on whether noise to labile and non-labile junctions is correlated. Specificity can sometimes be regained, however, with a return of input due to patterned vision. We propose that this provides a possible explanation of experimental results obtained by Imbert and Buisseret (1975); Blakemore and Van Sluyters (1975); Buisseret and Imbert (1976); and Frégnac and Imbert (1977, 1978).
Survival for extensive recurrent squamous cell carcinomas of the head and neck remains poor, with the major cause of death being local recurrence. Surgical implantation of iodine‐125 interstitial seeds allows tumoricidal doses of radiation to be delivered to residual tumor while minimizing radiation doses to the surrounding tissues. From 1978 to 1988, 39 implantations were performed on 35 patients for extensive recurrent squamous cell carcinoma of the head and neck. The decision for implantation was based on positive margins or close to resection margins from frozen sections after salvage resection. The determinate 5‐year disease‐free survival was 41%, with both the overall and no evidence of disease 5‐year survivals being 29%. Significant complications occurred in 36% of all cases. This figure increased to 56% when flap reconstruction was required. Possible reasons for this seemingly high complication rate are discussed. Considering the advanced nature of these recurrent carcinomas, surgical resection with iodine‐125 seed implantation appears to be an effective method of managing disease that might otherwise be judged unresectable and treated for palliation only.
From 1978 to 1988, 41 patients with extensive recurrent carcinomas of the head and neck were treated with surgical resection plus intraoperative iodine-125 seed implantation. Surgery was performed to resect the tumors and to expose the tumor beds for implantation. I-125 seeds were implanted intraoperatively, with a spacing of 0.75-1 cm between adjacent seeds, either into the soft tissue in the tumor bed or onto small patches of gelatin sponges to cover the bone, nerve, or blood vessel involved with disease. Reconstructive flaps were used in 18 patients. The average I-125 dose delivered by the implanted seeds was 8,263 cGy. The determinate 5-year actuarial survival rate for the entire group was 40%. The 5-year local disease control rate was 44%. Major complications were transient wound infection (32%), flap necrosis (24%), fistula formation (10%), and carotid blowout (5%). These results indicate that surgical resection plus I-125 seed implantation provides a potentially curative treatment for patients with extensive recurrent head and neck carcinomas that would be considered traditionally unresectable and that would be treated only with palliative therapy.
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