Parkinson’s disease: chameleons and mimics Khalid Ali, 1 Huw R Morris 2,3,4 1 Department of Neurology, Royal Gwent Hospital, Newport, Gwent, UK 2 Department of Clinical Neuroscience, UCL Institute of Neurology, London, UK 3 Department of Neurology, Royal Free Hospital, London, UK 4 Neurology, National Hospital for Neurology, London, UK Correspondence to Professor Huw R Morris, Department of Clinical Neuroscience, UCL Institute of Neurology, Upper 3rd Floor, Royal Free Hospital, Rowland Hill Street, London NW3 2PF, UK; h.morris@ucl.ac.uk Accepted 18 August 2014 Published Online First 24 September 2014 To cite: Ali K, Morris HR. Pract Neurol 2015;15:14–25. ABSTRACT Parkinson’s disease (PD) is a common neurodegenerative condition that usually presents with symptoms related to asymmetric bradykinesia, resting tremor, rigidity and postural instability. Making the correct diagnosis can be challenging as many conditions—including tremor, gait and atypical parkinsonian disorders —can mimic PD. PD can present with unanticipated motor and non-motor symptoms, and so can masquerade as a number of rheumatological, neurological, sleep and mood disorders. Careful clinical assessment, informed by well-validated diagnostic criteria, is important in the initial diagnostic formulation. In uncertain or ambiguous cases, follow-up with monitoring of the treatment response usually gives the correct diagnosis, as validated in postmortem follow-up studies. ‘Premotor’ PD—a range of non-motor symptoms, particularly sleep disorders and constipation, which can occur up to 20 years before PD motor onset—is common. The presence of non-motor features in early disease sometimes supports the diagnosis of PD. Here we give an overview of the diagnosis of PD and its most important chameleons and mimics, and review the recent advances in structural and functional imaging in parkinsonism. INTRODUCTION Parkinson’s disease (PD) is a common clin- ical condition affecting approximately 1% of the population older than 65 years. 12 Many lay people and non-specialists inevit- ably associate PD with tremor. However, tremor is a presenting feature in only half of all patients with PD, although 90%– 100% of patients with PD have tremor at some stage in their disease course. 3–6 There are other common causes of tremor —as well as conditions that cause slowness or a change in gait and posture—that can present as PD mimics. 7 Our concept of PD has changed from a pure movement dis- order to a clinicopathological entity with protean features, including changes in mood, sleep, behaviour, cognition and autonomic function. PD can cause symp- toms that lead to referrals to psychiatry, general medicine, care of the elderly, orthopaedic and rheumatology clinics, before arriving at the correct primary underlying diagnosis. A definite diagnosis of PD can only be made at postmortem by identifying degeneration of the substantia nigra pars compacta and the presence of Lewy bodies—insoluble cytoplasmic inclusions containing aggregated alpha- synuclein. Although early diagnosis is occa- sionally difficult, by the time of death at least 90% of postmortem-proven patients with PD have a correct clinical diagnosis. 8 TYPICAL PD AND THE CLINICAL EXAMINATION The distinctive pathological features of PD have led to robust and well-validated clinical diagnostic criteria. In 1988, Gibb and Lees developed the Queen Square Brain Bank (QSBB) criteria for PD, based on careful clinical observation combined with clinicopathological correlation. 9 In 1992, Hughes and colleagues showed that only 76% of patients diagnosed as having PD by UK neurologists fulfilled the neuropathological diagnostic criteria for the disease. Retrospective application of the QSBB clinical criteria improved the diagnostic accuracy to 82%. Multiple system atrophy, progressive supranuclear palsy, Alzheimer’s disease, Alzheimer-like pathology and vascular parkinsonism comprised most of the alternative diagno- ses. 10 The same group’s subsequent study in 2001 showed that the clinical diagnosis accuracy had improved to 90%. 11 The QSBB criteria remain a benchmark for PD diagnosis, and careful application and appreciation of the criteria will prevent most pitfalls for the clinician. However, it is important to appreciate that many patients with PD may not fulfil the QSBB criteria for PD at presentation (box 1). Expert clinicians are reportedly more REVIEW 14 Ali K, et al. Pract Neurol 2015;15:14–25. doi:10.1136/practneurol-2014-000849 on November 26, 2021 by guest. Protected by copyright. http://pn.bmj.com/ Pract Neurol: first published as 10.1136/practneurol-2014-000849 on 24 September 2014. Downloaded from