The parkinson's complex: Parkinsonism is just the tip of the iceberg

A 78-year-old man presented with a 15-year history of chronic constipation. At age 68, he experienced a nearcomplete loss of his sense of smell. Recently, he has developed an unusual sleep disorder, characterized by abrupt and at times combative behavior during the night that has resulted in injury to his spouse on two separate occasions; he is referred to a sleep disorders clinic. For most physicians, this medical history would not immediately bring Parkinson’s disease (PD) to mind. Yet, accumulating clinical and pathological evidence suggests it should. The traditional “textbook” description of PD defines the disease as a progressive disorder characterized by the triad of rigidity, bradykinesia, and rest tremor. A large body of evidence suggests that these features are due to degeneration of the dopaminergic nigrostriatal system. Although these clinical features typically lead a patient to the door of the neurologist, it is now increasingly clear that parkinsonism is only one aspect of a multifaceted and complex disorder. Furthermore, it is increasing clear that at least some of these nonparkinsonian features can precede the onset of parkinsonism by years and perhaps even decades. This essay argues that parkinsonism represents the disease as seen through the somewhat myopic lens of the neurologist, whereas in reality, parkinsonism only represents the tip of the iceberg that makes up this diverse disease (Fig 1). If one accepts this view, then the time has come to radically rethink the complex of features that constitute the disorder, which might be better viewed as a “centrosympathomyenteric neuronopathy.” The implications of this thesis are of more than academic importance. A failure to reevaluate how we view this disease at a time when our knowledge about its clinical and pathological features is expanding rapidly will adversely affect not only efforts to improve the diagnosis and management of the patients that we care for, but also is likely to impede research into the cause of the disease and attempts to slow or halt its progression.