Resolution of palinopsia with carbamazepine

Cognitive vision, its disorders and differential diagnosis in adults and children: knowing where and what things are

As ophthalmologists we need a basic model of how the higher visual system works and its common disorders. This presentation aims to provide an outline of such a model. Our ability to survey a visual scene, locate and recognise an object of interest, move towards it and pick it up, recruits a number of complex cognitive higher visual pathways, all of which are susceptible to damage. The visual map in the mind needs to be co-located with reality and is primarily plotted by the posterior parietal lobes, which interact with the frontal lobes to choose the object of interest. Neck and extraocular muscle proprioceptors are probably responsible for maintaining this co-location when the head and eyes move with respect to the body, and synchronous input from both eyes is needed for correct localisation of moving targets. Recognition of what is being looked at is brought about by comparing the visual input with the "image libraries" in the temporal lobes. Once an object is recognised, its choice is mediated by parietal and frontal lobe tissue. The parietal lobes determine the visual coordinates and plan the visually guided movement of the limbs to pick it up, and the frontal lobes participate in making the choice. The connection between the occipital lobes and the parietal lobes is known as the dorsal stream, and the connection between the occipital lobes and the temporal lobes, comprises the ventral stream. Both disorders of neck and extraocular muscle proprioception, and disorders leading to asynchronous input along the two optic nerves are "peripheral" causes of impaired visually guided movement, while bilateral damage to the parietal lobes can result in central impairment of visually guided movement, or optic ataxia. Damage to the temporal lobes can result in impaired recognition, problems with route finding and poor visual memory. Spontaneous activity in the temporal lobes can result in formed visual hallucinations, in patients with impaired central visual function, particularly the elderly. Deficits in cognitive visual function can occur in different combinations in both children and adults depending on the nature and distribution of the underlying brain damage. In young children the potential for recovery can lead to significant improvement in parietal lobe function with time. Patients with these disorders need an understanding of their deficits and a structured positive approach to their rehabilitation.

Placebo effects in oncology

BACKGROUND

Previous studies have suggested that placebo treatment can have positive effects on a variety of disorders and disease-related symptoms. However, the methodology used to collect and interpret the data may not have been ideal, because the studies were not double-blinded or the endpoints were not properly validated. The purpose of the present study was to determine the probability of improvement in symptoms or quality of life and tumor response in cancer patients treated with placebos in randomized controlled trials. We hypothesized that administration of placebos would improve symptom control and quality of life but would not lead to tumor response.

METHODS

We reviewed reports of randomized controlled trials in which there was a placebo arm (37 trials) or a best supportive care (BSC) arm (10 trials).

RESULTS

In trials that assessed average responses for patients in the placebo arm, improvements in average levels of pain were reported in two of six trials and in appetite, in one of seven trials. No improvements in average levels of weight gain (six trials), in quality of life (as assessed by patients; 10 trials), or in performance status (as assessed by physicians; nine trials) were reported. In trials that assessed response to a placebo in individual patients, 0%-21% of patients showed reduced pain or decreased analgesic intake, 8%-27% of patients showed appetite improvement, 7%-17% of patients showed weight gain, and 6%-14% of patients showed improvement in performance status. Quality of life for individual patients was not reported in any trial. Tumor response assessed by World Health Organization criteria was observed in 10 (2.7%) of 375 patients (seven trials total). Response as assessed by a serum marker was observed in 1 (1.7%) of 60 patients (two trials total). The probability of symptom improvement in patients receiving BSC was generally similar to that in patients receiving placebo, although no improvement in pain and only one tumor response among 191 patients (five trials) were reported.

CONCLUSION

In randomized double-blinded, placebo-controlled trials, presumably with minimum sources of bias, placebos are sometimes associated with improved control of symptoms such as pain and appetite but rarely with positive tumor response. Substantial improvements in symptoms and quality of life are unlikely to be due to placebo effects.

Central disorders of vision in humans

Over the past 20 years, researchers have discovered over 30 separate visual areas in the cortex of the macaque monkey that exhibit specific responses to visual and environmental stimuli. Many of these areas are homologous to regions of the human visual cortex, and numerous syndromes involving these areas are described in the neurologic and ophthalmic literature. The focus of this review is the anatomy and physiology of these higher cortical visual areas, with special emphasis on their relevance to syndromes in humans. The early visual system processes information primarily by way of two separate systems: parvocellular and magnocellular. Thus, even at this early stage, visual information is functionally segregated. We will trace this segregation to downstream areas involved in increasingly complex visual processing and discuss the results of lesions in these areas in humans. An understanding of these areas is important, as many of these patients will first seek the attention of the ophthalmologist, often with vague, poorly defined complaints that may be difficult to specifically define.