Reduction in thigh muscle cross-sectional area and strength in a 4-year follow-up in late polio.

OBJECTIVE

To study changes in cross-sectional thigh muscle area and muscle strength in late polio subjects over a 4-year period.

DESIGN

Longitudinal study of a cohort of polio survivors, comparing subjects who acknowledge (unstable) with those who do not acknowledge (stable) new muscle weakness.

SETTING

University hospital.

SUBJECTS: Eighteen subjects (6 men, 12 women) with polio-myelitis sequelae (39 to 46 years of age) were studied on two occasions 4 years apart; the first examination was 37 to 44 years after onset of polio. Subjects were recruited through hospital registers, newspaper advertisement, and a patient organization.

OUTCOME MEASUREMENTS: Thigh muscle and intermuscular and intramuscular adipose tissue (AT) cross-sectional areas were measured by computed tomography. Isometric muscle strength for knee extension and flexion was measured using a Kin-Com dynamometer.

RESULTS

Cross-sectional muscle area decreased on average 1.3 +/- 3.6 cm2 (1.4%, p < .05); the intermuscular and intramuscular AT area increased 1.8 +/- 3.4 cm2 (12.1%, p < .05). When divided by legs in which subjects reported (unstable) or did not report (unstable) or did not report (stable) increased muscle weakness, unstable legs showed significant reduction (p < .05) in muscle area, whereas stable legs did not. Estimated total thigh muscle strength decreased 7.8% +/- 2.9% (p < .01), with a significant (p < .001) reduction in unstable legs (13.4% +/- 4.3%) but not in stable legs. The reduction in strength appears to be greater than the reduction in cross-sectional muscle area, but there is still a significant correlation (r = .44, p < .05).

CONCLUSION

The present results demonstrate not only progress of muscle weakness, but also of muscle atrophy in postpolio subjects.