To provide a clinical description of subjective and objective autonomic dysfunction in moderate-severe TBI.

We conducted two UK-based cohort studies. Cohort 1 comprises msTBI patients prospectively recruited over 6 months from a regional referral TBI outpatient clinic, in whom we assessed burden of autonomic symptoms using the Composite Autonomic Symptom Score (COMPASS31) questionnaire. Cohort 2 comprises msTBI patients who had standard clinical autonomic tests (including: tilt, Valsalva, catecholamines and respiratory sinus arrhythmia assessment), retrospectively identified from the database of a national referral clinical autonomic unit over a 10-year period.

Cohort 1 comprises 29 msTBI patients (6 females, median age 40 years, range 19-76), with a median time since injury of 19 months (range 4-105). There was multi-domain symptom burden, with all but 3 patients reporting symptoms on the COMPASS31 questionnaire, and 17/29 reporting symptoms in 3+ domains. The most commonly reported symptoms were gastrointestinal (22/29), followed by orthostatic (17/29), pupillomotor (14/29), secretomotor (14/29), bladder (12/29) and, least commonly, vasomotor (6/29). Cohort 2 comprises 18 msTBI patients (7 females, median age 44 years, range 21-64), with a median time between injury and testing of 57.5 months (range: 2-416). Orthostatic symptoms were the primary reason for referral. Clinical autonomic tests revealed a broad spectrum of autonomic dysfunction: 3/18 had evidence of sympathetic dysfunction, 10/18 had evidence of parasympathetic dysfunction, of which 6 also had evidence of mixed dysfunction.

Our results provide evidence for clinically relevant autonomic dysfunction in patients with chronic, moderate-severe TBI. Our study advocates for routine enquiry about potential autonomic symptoms in this population, and the utility of formal clinical autonomic testing in providing diagnoses.