Table 1.

Neuropsychological tests used to assess cognitive function

Test	Instructions	Cognitive Domain
Digit Span Forwards	Patient was asked to repeat the number sequence, with a point awarded for each correct answer. One number was added in each subsequent trial, with a maximum possible score of 16 [24].	Memory
Digit Span Backwards	Patient was asked to recite the number sequence in reverse order, which required mental representation of the sequence and higher order functioning [24]	Attention executive functioning
Mental Control	Patient was asked to count to 20, recite the alphabet, state the days of the week and months in order, and then repeat the process in reverse order. The amount of time needed to complete in seconds was recorded per task, with the total seconds recorded [24].	Attention executive functioning memory
Stroop Test	Patient was asked to state the color of 28 words from a list where the words and color of the printed words did not match. The total number of seconds required to correctly recite all the colors was recorded for each subject, with a lower value indicating better performance [25]	Executive functioning
Word List: Immediate Recall	Patient was asked to repeat a list of 12 words, with 1 point awarded for each correct answer. This process was repeated a total of four consecutive times using the same list, with the cumulative total score recorded [26].	Attention memory
Word List: Delayed Recall	Patient was asked to repeat the 12 words after a 25 min delay. One point was given per correct answer [26].	Attention memory
Controlled Oral Word Association Test	Subjects were asked to verbalize as many possible words for 1 min each, starting with the letters C and F. Phonemic fluency was assessed, with one point awarded per word. Patients were then instructed to list as many animals as they could within 1 min to assess semantic fluency. The total score from the three categories was recorded, with a higher score representing increased performance [27].	Attention executive functioning
Oral Trail Making Test	Subjects were asked to alternate between letters and numbers until he/she had gone through the entire alphabet (A1, B2, C3 etc. to Z26). Time to errors ratio was recorded, with a lower ratio representing increased cognitive function [28].	Executive functioning
Letter-Number Sequencing	After being given a list of letters and numbers, the subject was asked to reorder the numbers first in chronological order followed by the letters in alphabetical order, and awarded a point for each correct sequence. Maximum possible score was 21 [29]	Executive functioning
Brief Pain Inventory: Pain level	This questionnaire assessed the patient’s pain level using four questions, each on a scale of 0–10 (maximum possible total score of 40) [29].	N/A
Brief Pain Inventory: Pain interference	The second portion of the questionnaire attempted to quantify (scale of 1–10 with 10 as the most severe) pain interference with the variables such as activity, mood, and ambulation. The maximum total possible score for the pain interference section was 70 [29].