title: Point pressure sensitivity in early stage Parkinson's disease.
abstract: A number of sensory changes occur in the earliest stages of Parkinson's disease (PD), some of which precede the expression of the classic motor phenotype by years (e.g., olfactory dysfunction). Whether point pressure sensitivity (PPS), a cutaneous measure of light touch mediated by myelinated Aβ fibers, is altered in early PD is not clear. Prior studies on this point are contradictory and are based on non-forced-choice threshold tests that confound the sensitivity measure with the response criterion. While α-synuclein pathology, a defining feature of PD, is present in the skin of PD patients, it is restricted to unmyelinated nerve fibers, suggesting PPS may be spared in this disease. We determined PPS thresholds using a state-of-the-art forced-choice staircase threshold test paradigm in 29 early stage PD patients and 29 matched controls at 11 body sites: the center of the forehead and the left and right forearms, index fingers, palms, medial soles of the feet, and plantar halluces. The patients were tested, in counterbalanced sessions, both on and off dopamine-related medications (DRMs). PPS was not influenced by PD and did not correlate with DRM l-DOPA equivalents, scores on the Unified Parkinson's Disease Rating Scale, side of the major motor disturbances, or SPECT imaging of the striatal dopamine transporter, as measured by technetium-99m TRODAT. However, PPS thresholds were lower on the left than on the right side of the body (p=0.008) and on the upper extremities relative to the toes and feet (ps<0.0001). Positive correlations were evident among the thresholds obtained across all body sectors, even though disparate regions of the body differed in terms of absolute sensitivity. This study indicates that PPS is not influenced in early stage PD regardless of whether patients are on or off DRMs.
authors.affiliation: Smell and Taste Center, Department of Otorhinolaryngology: Head and Neck Surgery, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA. Electronic address: richard.doty@uphs.upenn.edu.
authors.forename: Richard L
authors.initials: RL
authors.lastname: Doty
authors.affiliation: Smell and Taste Center, Department of Otorhinolaryngology: Head and Neck Surgery, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA.
authors.forename: Shifa S
authors.initials: SS
authors.lastname: Gandhi
authors.affiliation: Smell and Taste Center, Department of Otorhinolaryngology: Head and Neck Surgery, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA.
authors.forename: Allen
authors.initials: A
authors.lastname: Osman
authors.affiliation: Department of Neurology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA.
authors.forename: Howard I
authors.initials: HI
authors.lastname: Hurtig
authors.affiliation: Smell and Taste Center, Department of Otorhinolaryngology: Head and Neck Surgery, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA.
authors.forename: Ian
authors.initials: I
authors.lastname: Pawasarat
authors.affiliation: Smell and Taste Center, Department of Otorhinolaryngology: Head and Neck Surgery, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA.
authors.forename: Evan
authors.initials: E
authors.lastname: Beals
authors.affiliation: Smell and Taste Center, Department of Otorhinolaryngology: Head and Neck Surgery, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA.
authors.forename: Inna
authors.initials: I
authors.lastname: Chung
authors.affiliation: Department of Radiology, Division of Nuclear Medicine and Clinical Molecular Imaging, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA.
authors.forename: Jacob
authors.initials: J
authors.lastname: Dubroff
authors.affiliation: Myrna Brind Center of Integrative Medicine, Thomas Jefferson University, Philadelphia, PA USA.
authors.forename: Andrew
authors.initials: A
authors.lastname: Newberg
authors.affiliation: Department of Ophthalmology and Center for Clinical Epidemiology and Biostatistics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA.
authors.forename: Gui-Shang
authors.initials: GS
authors.lastname: Ying
authors.affiliation: Smell and Taste Center, Department of Otorhinolaryngology: Head and Neck Surgery, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA.
authors.forename: Fidias E
authors.initials: FE
authors.lastname: Leon-Sarmiento
mesh_terms: D003342:Corpus Striatum / Q000000981:diagnostic imaging / Q000187:drug effects / Q000503:physiopathology; D015259:Dopamine Agents / Q000627:therapeutic use; D050483:Dopamine Plasma Membrane Transport Proteins / Q000378:metabolism; D005260:Female; D005528:Foot / Q000503:physiopathology; D005546:Forehead / Q000503:physiopathology; D007839:Functional Laterality; D006801:Humans; D008297:Male; D008875:Middle Aged; D015609:Organotechnetium Compounds; D010300:Parkinson Disease / Q000000981:diagnostic imaging / Q000188:drug therapy / Q000503:physiopathology*; D010812:Physical Stimulation; D011312:Pressure; D019275:Radiopharmaceuticals; D012684:Sensory Thresholds / Q000502:physiology; D012720:Severity of Illness Index; D012727:Sex Characteristics; D015899:Tomography, Emission-Computed, Single-Photon; D055698:Touch Perception / Q000502:physiology*; D014326:Tropanes; D034941:Upper Extremity / Q000503:physiopathology
chemical_list: D015259:Dopamine Agents; D050483:Dopamine Plasma Membrane Transport Proteins; D015609:Organotechnetium Compounds; D019275:Radiopharmaceuticals; D014326:Tropanes; C104196:technetium Tc 99m TRODAT-1
keywords: Brain laterality; Parkinson's disease; Somatosensation; Touch; l-DOPA