Parkinsonism is a clinical syndrome characterized by a combination of six cardinal features: (1) bradykinesia, (2) rigidity, (3) tremor at rest, (4) postural instability, (5) flexed posture, and (6) freezing or motor blocks. Idiopathic Parkinson’s disease (PD) is by far the most common cause of parkinsonism and should always be the diagnosis if a definite secondary cause cannot be identified (Table 17.1). Slow progression, unilateral presentation with asymmetrical signs, a pill-rolling rest tremor, and good sustained response to levodopa support the diagnosis  (Table 17.2). Other forms are broadly classified as atypical parkinsonian syndromes (multiple system atrophy parkinsonism (MSA-P), progressive supranuclear palsy (PSP), corticobasal syndrome (CBS)), heredodegenerative disorders associated with parkinsonism and secondary (symptomatic, acquired) parkinsonism (Table 17.1). Less frequently, patients who receive an initial clinical diagnosis of PD are found to have parkinsonian features as part of other diseases, such as dementia with Lewy bodies (DLB) or Alzheimer’s disease (AD). The present chapter focuses on PD, PD with cognitive impairment, and DLB. Chapter 19 describes the most frequent causes of non-PD parkinsonism, both clinically and with respect to the neuroimaging characteristics. The present diagnostic approach in PD The definitive diagnosis of idiopathic PD requires a histological demonstration of intraneuronal Lewy body inclusions in the substantia nigra (SN) pars compacta . In most cases, the diagnosis of probable PD can be made on clinical grounds and no ancillary investigations are needed. The most widely used clinical criteria for the diagnosis of PD are those introduced by the Queen Square Brain Bank (QSBB) . These criteria are based on a three-step approach (Table 17.2): (1) signs that must be present, (2) signs that should not be present, and (3) supportive criteria. However, a number of pitfalls have been suggested: (a) some other forms of parkinsonism, including atypical ones, may also, albeit transiently, respond to dopamine replacement therapy and have prolonged disease course; (b) asymmetry may also occur in atypical parkinsonism; and (c) having more than one affected relative cannot exclude a diagnosis of PD. In practice, positive clinical criteria for PD-related parkinsonism (i.e. bradykinesia in combination with rigidity, tremor at rest, or postural instability) include the progressive character of the symptoms, the unilateral onset with persistent unilateral preponderance, and a persistent levodopa responsiveness. Clinicopathologic studies suggest that when an established PD is diagnosed according to QSBB criteria , there is a 90% concordance between expert clinical impression and the presence of nigral Lewy bodies .
|Title of host publication||Imaging Acute Neurologic Disease: A Symptom-Based Approach|
|Publisher||Cambridge University Press|
|Number of pages||21|
|ISBN (Print)||9781139565653, 9781107035942|
|Publication status||Published - Jan 1 2014|
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