Validation of the Subjective Neuropsychological Symptoms Scale (SNPSS) in Injured Motorists

Background: There is a need for scales for standardized assessments of subjective neuropsychological symptoms reported by diverse patient populations such as injured motorists, patients with multiple sclerosis, very severe anorexia, and neurotoxin exposure. This article introduces the Subjective Neuropsychological Symptoms Scale (SNPSS) and describes its validation on a sample of persons injured in high-speed motor vehicle accidents (MVAs). The SNPSS consists of post-concussion items not included in the Rivermead Post-Concussion Symptoms Questionnaire (that is, e.g., tinnitus, impaired balance, word finding difficulty), items to assess motor symptoms (e.g., hand tremor), and symptoms frequently observed in patients with spinal injury or deterioration (tingling, numbness, or reduced feeling in the limbs).

Method: De-identified file data of 141 post-MVA patients (49 men, 92 women, average age 39.4 years, SD=13.0) included their responses to the SNPSS, the Rivermead Post-Concussion Symptoms Questionnaire, Insomnia Severity Index, the PCL-5 measure of PTSD according to DSM5,the ratings of worst, least, and average pain on the Brief Pain Inventory and ratings of depression, anger, and anxiety on the Whiplash Disability Questionnaire. The patients’ responses to the SNPSS and the Rivermead were compared to those of a sample of 23 normal controls (11 men, 12 women, average age 45.0 years, SD=21.2).

Results: Average SNPSS score of patients (20.3 points, SD=11.3) was significantly higher than of normal controls (average of 2.5 points, SD=4.8): the magnitude of this relationship (r=.51, p<.001) indicates satisfactory criterion validity of the SNPSS on post-MVA patients. With respect to convergent validity, the SNPSS correlated significantly (r=.79, p<.001) with the Rivermead scores. The SNPSS also correlated significantly with clinical variables often associated with neurological trauma in injured motorists: pain (r=.37), insomnia (r=.45), and PTSD (r=.56). Cronbach alpha coefficient of the SNPSS is very satisfactory (.90).

Discussion and Conclusions: Criterion and convergent validity data of SNPSS on injured motorists in this study are satisfactory. Validation data from populations other than injured motorists are much needed, e.g., survey data from patient groups with neurological disease such as multiple sclerosis or those accidentally exposed to neurotoxins.

Keywords: neurology, neuropsychology, whiplash, concussion.