Is postural control associated with mental functioning in the persistent postconcussion syndrome?

Objective: To investigate whether balance is associated with mental functioning after mild traumatic brain injury (MTBI). Design: Experimental two-group design. Setting: Outpatient rehabilitation department. Patients and Other Participants: From a consecutive sample of referred MTBI patients, 15 subjects who complained of imbalance were included (8 men and 7 women, age 35.9 +/- 8.6yrs), Subjects with detectable neurologic impairments were excluded. Twenty healthy control subjects of the same age group also were tested. Main Outcome Measures: In both groups, a force platform recorded center-of-pressure (CP) fluctuations during standing and weight shifting in different conditions. For the patients, attention and mental speed were assessed with the Symbol-Digit Substitution Test of the Wechsler Adult Intelligence Scale (Dutch version), verbal learning and memory were assessed with the 15-Words Test, and emotional distress was assessed with the Symptom Checklist-90. Results: Compared with controls, patients showed an overall increase of 60% in CP velocity and an overall weight-shifting speed 25% slower (p <.005), indicating static and dynamic postural instability. Only performance on the Symbol-Digit Substitution Test was associated with both static and dynamic balance (p <.02), giving an explained variance of over 40%. Conclusion: The results indicate a possible association of balance with cognitive performance but not with emotional well-being after MTBI, suggesting an organic rather than a functional cause of postural instability. Further research is needed to assess the possible clinical implications. (C) 1999 by the American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation.