الفهرس 
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Abstract
PD is the most common movement disorder and the second most common neurodegenerative disorder of the central nervous system.
The clinical findings of PD consist of cardinal motor features which are tremors, rigidity, bradykinesia, and postural instability, in addition to non-motor symptoms which are classified into autonomic symptoms, sleep disturbances, neuropsychiatric symptoms, cognitive dysfunction, and sensory symptoms.
Pain is one of the most common NMS in PD affecting up to 85% of patients. chronic pain in PD was even mentioned by James Parkinson in his original description of the disease in 1817. Furthermore, it has been described by PD patients as one of their most bothersome symptoms which significantly impacts their quality of life.
Despite those facts, pain in PD remains under-recognized and undertreated; this may be attributed to the lack of consensus regarding the classification of pain and the mechanisms underlying its pathology.
There were many attempts to create standard scales to rate or assess pain in PD, but most of them were flawed, either by being non-specific for PD patients, or unavailable in other languages apart from which they were initially developed.
However, in 2015, the King’s Parkinson’s disease Pain Scale (KPPS) was introduced as the first disease specific
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scale to assess pain in PD, not to mention it has been accepted by the international movement disorder society (MDS) and validated in its original language and other languages as well.
KPPS is an easy and fast to administer scale. It consists of 14 items divided into 7 domains (musculoskeletal pain, chronic pain, fluctuation-related pain, nocturnal pain, orofacial pain, edema/swelling, and radicular pain). Each item is rated on a degree of severity (range 0 to 3), multiplied by frequency (range 0 to 4), resulting in a sub score from 0 to 12 each. The total sum of items may range from 0 to 168 where a higher score reflects a greater pain burden.
Using KPPS, the primary aim of our study was to investigate the prevalence and severity of different types of pain in PD patients in comparison with healthy controls, and to identify pain determinants in those patients as well as its impact on their quality of life. Our Secondary aim was to translate the KPPS scale into an Arabic version and to assess its validity and reliability.
This cross-sectional case control study was conducted on 45 PD patients and 40 sex- and age-matched healthy controls (excluding participants suffering from other secondary causes for pain and those with dementia).
In this study, the prevalence of pain within PD patients was significantly higher than control group, more specifically in musculoskeletal pain, fluctuation related pain, nocturnal pain and orofacial pain. The average number of pain types per patient was higher among the PD patients‟ group as well. Furthermore, the mean total KPPS score (reflecting pain severity and frequency) in the PD group was statistically
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higher than control group as well as almost all subdomain scores.
All the PD patients in our study (100%) reported at least 1 type of pain. The most common type of pain in those patients was fluctuation-related pain (75.6%) followed closely by musculoskeletal pain (73.3%) and nocturnal pain (68.9%), while the least common types were radicular pain (40%) and orofacial pain (46.67%).
We also studied the relation between KPPs scores and other factors such as sex, age of onset, duration of illness, depression, quality of life, fluctuation of symptoms, motor symptoms and complications, and the following correlations were observed. In the PD patients‟ group, factors associated with higher KPSS scores were duration of illness (P = 0.02); depression as assessed by BDI (P = 0.028); worse quality of life as assessed by PDQ-39 (P = 0.005); severity of disease evaluated by HY (P = 0.017); impaired capability as assessed by S&E-ADL scale (P = 0.004); the presence of dystonia (P = 0.001); higher NMSS total scores (P = 0.001), higher NoMoFA total score (more specifically fluctuation of non-motor symptoms reflected by non-motor fluctuation “NMF” domain) (P = 0.001), MDS-UPDRS part II (P < 0.001), and MDS-UPDRS part IV (P = 0.019) (reflecting motor activities and motor complications respectively).
However, it is important to mention that a stepwise multiple linear regression model was conducted to determine which of these factors could be considered as predictors (dependent variables) of pain and none of them achieved statistical significance.
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On the other hand, pain was not associated with gender or motor symptoms as rigidity and bradykinesia.
Using KPPS, we were able to further identify the types of pain especially influencing QoL and depression in PD patients. While depression was associated with nocturnal pain in particular, QoL was affected mainly by fluctuation- related pain and nocturnal pain followed by chronic pain and discoloration/edema.
Comparing motor subtypes, PIGD subtype had significantly higher musculoskeletal pain scores compared to TD but there was no significant difference regarding total pain severity or prevalence. Additionally, patients with early onset of disease had significantly higher total scores of pain than patients of late onset, more specifically regarding fluctuation- related pain and nocturnal pain.
Finally, the interclass correlation coefficient of translated KPPS was 0.9- 1 reflecting fair agreement between readings of first and second rater (rater A and B) in total score and subdomains scores of KPPS, while Wilcoxon Rank test showed no statistical difference between the two readings of the same rater, both of which indicate strong reliability of the translated Arabic version of KPPS allowing for a wider use of this tool. We believe that adopting a unified classification system for pain in PD can markedly improve identification, proper analysis, management, and follow up of pain in PD patients. Moreover, it will make direct comparison and analysis of results between different studies easier and more coherent.