title: Unexplained lower limb pain in Parkinson's disease: a phenotypic variant of "painful Parkinson's disease".
abstract: Unexplained pain is a key non-motor symptom (NMS) of Parkinson's disease (PD) that is prevalent throughout the condition and often unrecognized and under treated. We have identified a cluster of patients with unexplained refractory and intrusive lower limb pain.
  
  
  METHODS
  Patients with 'unexplained' pain were identified from a survey using a non-motor symptom questionnaire and scale (NMSQuest, NMSS). Patients reporting unexplained severe proximal lower limb pain were then assessed using a newly devised PD pain scale. Co-morbid conditions were excluded and all had lower spine imaging.
  
  
  RESULTS
  From a cohort of 225 patients we have identified 22 with unexplained lower limb pain described as persistent leg pain ranging from unilateral to bilateral sometimes associated with whole body pain. None had significant spinal pathology or evidence of large fiber neuropathy. 14 were on regular analgesics with poor effect while 9 took morphine based remedies. Severe unremitting pain led to accidental overdose and death in one patient. All took a combination of levodopa and dopamine agonist treatment including 3 on intrajejunal levodopa infusion. All had high NMSQuest (mean = 17/30) and NMSS (mean = 95 (normal range 30-60)) scores.
  
  
  CONCLUSIONS
  We believe that unexplained lower limb pain is a specific non-motor phenotype in Parkinson's disease that is problematic and often undisclosed. This may be a variant of central pain and merits recognition.
authors.affiliation: National Parkinson Foundation International Centre of Excellence, King's College Hospital, Kings College and Kings Health Partners, London SE5 9RS, UK. Electronic address: vcjwallace@gmail.com.
authors.forename: Victoria C J
authors.initials: VC
authors.lastname: Wallace
authors.affiliation: National Parkinson Foundation International Centre of Excellence, King's College Hospital, Kings College and Kings Health Partners, London SE5 9RS, UK.
authors.forename: K Ray
authors.initials: KR
authors.lastname: Chaudhuri
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006801:Humans; D035002:Lower Extremity; D008297:Male; D008875:Middle Aged; D010146:Pain / Q000453:epidemiology / Q000209:etiology*; D010300:Parkinson Disease / Q000150:complications*; D010641:Phenotype
keywords: Central pain; Lower limb pain; NMSS; Opiate; Pain; Parkinson's disease