Autonomic Nervous System Dysfunction in Concussion (IN5-2.005)

OBJECTIVE: To describe the frequency, pattern, and severity of autonomic signs and symptoms following concussion. BACKGROUND: Autonomic nervous system impairment (ANS) is recognized as a potential complication following severe traumatic brain injury. 9Dizziness9, often reported by those who experience concussion (mild traumatic brain injury), is widely considered to be due to vestibular injury/dysfunction, despite normal vestibular testing. Following the clinical observation that the dizziness reported by many concussion patients could be more accurately characterized as postural lightheadedness, exercise intolerance, and pre-syncope, we sought to determine the frequency, pattern, and severity of ANS impairment in a consecutively studied cohort of patients evaluated in the concussion clinic at our institution. DESIGN/METHODS: A retrospective review of 20 consecutive concussion patients was performed, recording clinical, radiologic, laboratory, and autonomic test findings in this cohort of patients. RESULTS: Nearly all patients reported symptoms of orthostatic intolerance, including postural lightheadedness, exercise intolerance. Four patients reported a history of syncope. All 20 patients had significant abnormalities on autonomic testing, consisting of excessive tachycardia and/or oscillations or unstable blood pressures with tilt-table testing. These findings were attributed to adrenergic dysfunction. Calculations of adrenergic baroreflex sensitivity demonstrated adrenergic insufficiency in 8 patients, and adrenergic hypersensitivity in 5 patients. Standing norepinephrine levels correlated with adrenergic sensitivity, suggesting the presence of a hyperadrenergic state in some and adrenergic insufficiency in others. Impairment in cardiovagal and postganglionic sympathetic sudomotor function was present in a minority of patients. CONCLUSIONS: These findings suggest that: 1) ANS dysfunction is a common and previously unrecognized cause of 9dizziness9 following concussion; 2) abnormalities can be identified on standard autonomic testing; 3) abnormal adrenergic function is the primary cause of autonomic findings; 4) ANS impairment is a potential biomarker for concussion; and 5) this novel finding has therapeutic implications for patients reporting dizziness following concussion. Disclosure: Dr. Goodman has nothing to disclose. Dr. Vargas has received personal compensation for activities with Merck & Co., Inc. as a speaker. Dr. Dodick has received personal compensation for activities with Allergan, Inc., Pfizer Inc, Merck & Co., Inc., Coherex, Ferring, Neurocore, Neuralieve, Neuraxon, NuPathe Inc., MAP Pharmaceuticals, SmithKlineBeecham, Boston Scientific, Medtronic, Inc., Colucid, Novartis, Johnson & Johnson, Nautilus, Eli Lilly & Company, Nevro, GlaxoSmithKline, Inc., Autonomic Technologies, Zogenix, Inc., Impax Laboratories, Inc., Bristol-Myers Squibb Company, CogniMed, Scientiae, Intramed, SAGE Publishing, Lippincott Williams and Wilkins, Oxford University Press, Cambridge University Press, Miller Medical, and Annenberg for Health Sciences. Dr. Dodick has received personal compensation in an editorial capacity for The Neurologist, Lancet Neurology, Postgraduate Medicine, Headache Currents, Headache, Handbook of Headache, and Cephalalgia, and UpToDate. Dr. Dodick has received research support from St Jude Medical, Inc, and Medtronic, Inc.