Approach To The Patient With Visual Failure

Two questions must be answered when a patient with visual failure is seen: Where is the lesion? and What is its pathologic nature? Clinical answers to the second question come mainly from the patient's history, and the physical examination should answer the first question.

The first step, then, is the detailed history of the mode of onset and evolution of the symptoms. The second step is then to search for evidence to localize the lesion, involving one or both eyes, and to establish a baseline for monitoring progression of the disease and the treatment effects. The second step involves the rigorous examination of the first six cranial nerves, followed by the remainder of the standard neurologic examination to detect spread of the tumor beyond the sella region.

The final stage of the neurologic assessment involves selecting appropriate investigations to confirm clinical localization and diagnosis, to provide more evidence about the pathologic nature of the compressing lesion, and to plan treatment. Magnetic resonance imaging (MRI) and, to a lesser extent, computed X-ray tomography (CT) provide invaluable and sometimes complementary evidence. MRI usually with and without gadolinium-DPTA (diethylene-triaminepenta acetic acid) enhancement, is the method of choice for delineating the extent of the lesion and its relationship to neural structures. CT gives information about bone involvement and calcification, which may be difficult to interpret on MRI. The presence of calcification is important to differential diagnosis, because it is common in craniopharyngiomas, occasionally seen in men-ingiomata, and only rarely seen in pituitary adenomas. MRI should be the first imaging investigation whenever possible, and other imaging is seldom required. Plain-skull X-rays and cerebral angiography are now virtually never required. Postoperatively, MRI is the clear imaging choice for following progress.

Other physiologic examinations, such as visual evoked potentials with half-field stimulation, had a brief place in the investigative armamentarium, but imaging techniques have advanced to such an extent that their place in now questionable.

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