A parkinsonism is a syndrome defined by akinesia associated with rigidity or rest tremor. The akinesia can be expressed as motor slowness (bradykinesia) or as a paucity of movement (hypokinesia), i.e., difficulty in the initiation of or decreased amplitude of movements such as arm swing or facial expression. This syndrome is usually the result of a dysfunctional nigrostriatal pallidal pathway. Impairment of postural reflexes is not included as one of the features of the parkinsonian syndrome since abnormal postural reflexes are generally the consequence of dysfunction of other motor pathways. There are a variety of causes of parkinsonism, but Parkinson's disease (PD) is the most common (Fig. 1). Although there is extensive literature on PD, this is one of the few books dedicated to the remaining atypical parkinsonian disorders.To appropriately diagnose PD, one should be aware of when to suspect that a patient does not have PD and may be suffering from one of these atypical disorders.
The "atypical parkinsonian disorders" (previously known as "Parkinson plus syndromes") are characterized by a rapidly evolving parkinsonism that has a poor or transient response to dopaminergic therapy and often associates with one or more atypical features for PD. Some of these features include early presence of postural instability, early autonomic failure, vertical supranuclear gaze palsy, pyramidal or cerebellar signs, alien limb syndrome, and apraxia (Table 1; see corresponding video segments on accompanying DVD). Making the distinction between these two major groups of disorders is critical for both clinical practice and research because the prognosis and treatment of patients with an atypical parkinsonian disorder and those with PD differ (1-4). In the clinical setting, although patients with PD may have an almost normal life-span if treated appropriately (4-6), those with atypical parkinsonian disorders have a shorter survival time and more complications occur at early stages and are frequently more severe (3,7-10) (see Table 2 for an example). Moreover, indicated therapies (particularly surgical approaches) differ significantly since some may not be indicated to treat patients with atypical parkinsonian disorders. Until recently, clinicians would "lump" all the atypical parkinsonian disorders together and would only distinguish between this group and PD. However, the need for early identification of the different atypical parkinsonian disorders is becoming increasingly recognized (11), as their prognosis, complications, and survival differ (3,7,8,12-19).
For research, this distinction is crucial; homogenous groups are a necessity for studies that lead to firm conclusions. Genetic, analytical, epidemiological, and clinical trials require the inclusion of accurately diagnosed patients. However, diagnosis of the atypical parkinsonian disorders can be at times challenging (20-25) since these disorders may have similar presentations at early disease stages
From: Current Clinical Neurology: Atypical Parkinsonian Disorders Edited by: I. Litvan © Humana Press Inc., Totowa, NJ
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