Normal pressure hydrocephalus (NPH) is characterized by the presence of ventriculomegaly associated with the triad of gait, memory, and urinary problems in the absence of a detectable cause. There is a group of individuals with longstanding compensated hydrocephalus that might develop a clinical picture similar to idiopathic NPH (iNPH) at an age younger than the typical age of presentation of iNPH. The syndromes of hydrocephalus in young and middle-aged adults, SHYMA, or longstanding overt ventriculomegaly, also known as LOVA, specifically refer to this phenomenon. This characteristic clinical presentation of iNPH, however, also accompanies the insidious onset of hydrocephalus secondary to other processes, such as infection, malignancy, and hemorrhage. In this chapter, we discuss the clinical features, evaluation, and management of secondary and/or compensated hydrocephalus. The syndrome of compensated hydrocephalus Compensated hydrocephalus is usually associated with macrocephaly and copper cranium. Other common radiologic features include: herniation of the third ventricle into the sella turcica, empty sella, less prominent temporal horns and atrophy of the corpus callosum. These patients commonly have mild symptoms that can manifest in frequent mild to moderate headaches, clumsiness, or difficulty concentrating. Literature would suggest that these other forms of chronic or compensated hydrocephalus are subsets of normal pressure hydrocephalus; however, there are enough distinctive features to suggest that some of these syndromes represent an entirely separate clinical entity based on the same pathophysiologic mechanism (Figure 21.1).
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