Frequency of Formication Symptoms in Injured Motorists and in Normal Controls

Abstract

Background: Formication is the sensation or feeling as if insects were crawling on or under the skin. It is observed in a variety of clinical situations including drug intoxications, multiple sclerosis, and diabetic neuropathy, among many others. Furthermore, it can be associated with injuries incurred during motor vehicle accidents (MVAs). We examined the frequency of reports of formication in a normal control sample as well as in a sample of motorists who sustained concussive and whiplash injuries following high impact MVAs. We also evaluated the correlations of the formication to measures of pain, insomnia, and of various post-accident neuropsychological symptoms. Method: De-identified data on 23 injured motorists (mean age=38.0 years, SD=12.8) and on 20 normal controls (mean age 42.8 years, SD=19.9) were available. All motorists responded to the following True/False item: “I have pain in my body which seems to feel like bugs crawling under the surface of my skin.” Their data were also available on the Brief Pain Inventory, Post-MVA Neurological Symptoms (PMNS) scale, Insomnia Severity Index, and on the Rivermead Post-Concussion Symptoms Questionnaire. The data of normal controls included responses to the following specific item of the formication questionnaire: “Do you sometimes have an annoying feeling in some of your limbs or in some other part of your body as if insects were crawling on or under your skin?” The participants were to circle one of the following responses: “never, very rarely, sometimes, often, or almost constantly.” Results and Discussion: Almost a third (30.4%) of the motorists who sustained whiplash trauma in their MVA reported the formication. In contrast, only one of the 20 normal controls (i.e., 5%) reported formication (this was an elderly man with MRI documented pathology in lumbosacral spine). Notably, formication correlated significantly with the ratings of “reduced feeling in the limbs” (r=.55, p=.010), but not with ratings of “tingling in the limbs” (r=.21, p>.05). Conclusion: The painful form of formication has been reported by almost a third of motorists who sustained whiplash injuries in their accident.