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Parkinson's disease without nigral degeneration: a pathological correlate of scans without evidence of dopaminergic deficit (SWEDD)?
  1. Helen Ling1,2,
  2. Seamus Kearney1,3,
  3. Helen Lai Kuen Yip4,5,
  4. Laura Silveira-Moriyama1,6,
  5. Tamas Revesz1,2,
  6. Janice L Holton1,2,
  7. Catherine Strand2,
  8. Karen Davey2,
  9. Kin Ying Mok7,8,
  10. James M Polke7,
  11. Andrew J Lees1,2
  1. 1Reta Lila Weston Institute of Neurological Studies, UCL Institute of Neurology, London, UK
  2. 2Queen Square Brain Bank for Neurological Disorders, UCL Institute of Neurology, London, UK
  3. 3Belfast Health and Social Care Trust, Belfast, Ireland
  4. 4Department of Rehabilitation and Extended Care, Wong Tai Sin Hospital TWGHs, Hong Kong, Hong Kong
  5. 5Neuro-medical Unit, Department of Medicine and Geriatrics, Kwong Wah Hospital TWGHs, Hong Kong, Hong Kong
  6. 6Postgraduate Program in Medicine, Universidade Nove de Julho, UNINOVE, São Paulo, Brazil
  7. 7Department of Molecular Neuroscience, UCL Institute of Neurology, London, UK
  8. 8Division of Life Science, Hong Kong University of Science and Technology, Hong Kong, Hong Kong
  1. Correspondence to Professor Andrew J Lees, Reta Lila Weston Institute of Neurological Studies, UCL Institute of Neurology, 1 Wakefield street, London WC1N 1PJ, UK; andrew.lees{at}ucl.ac.uk

Abstract

Objective To describe 5 cases of Parkinson's disease lacking any detectable histopathology.

Background The diagnosis of Parkinson's disease is supported histologically by the findings of α-synuclein immunopositive Lewy bodies and neurites and severe substantia nigra cell loss. Bradykinesia as defined by slowness of initiation of movement and a progressive reduction in speed and amplitude on finger tapping is a clinical correlate of pars compacta nigral degeneration. There are very few published cases of Parkinson's disease in which no pathological abnormality was found, and some of these cases were in hindsight thought to have probably been cases of indeterminate senile tremor or dystonic tremor.

Methods Retrospective case notes review of the Queen Square Brain Bank archival collection and detailed neuropathological analysis of the selected cases.

Results 5 cases considered to have Parkinson's disease by neurologists throughout the entirety of their illness that lacked any histopathological findings known to be associated with Parkinson's syndromes were identified out of a total number of 773 brains with a final clinical diagnosis of Parkinson's disease in the Queen Square Brain Bank. Retrospective case note analysis did not suggest dystonic tremor or indeterminate tremor in any of them. There was a reduction in tyrosine hydroxylase (TH) density in the striatum in these cases when compared with healthy controls, but not in the substantia nigra.

Conclusions Striatal dopamine deficiency without nigral cell loss is the most likely explanation for the clinical findings; other possible explanations include slowness due to comorbidities misinterpreted as bradykinesia, a tardive syndrome related to undisclosed previous neuroleptic exposure, or ‘soft age-related’ parkinsonian signs. These cases emphasise the need to regularly review the diagnosis in cases of suspected Parkinson's disease and highlight the need for precision in the neurological examination particularly of elderly patients. These cases may represent a distinct entity of diagnostic exclusion and may be considered one explanation for the radiological phenomenon of SWEDD (scans without evidence of dopaminergic deficit).

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