Bone strength in multiple sclerosis: cortical midtibial speed-of-sound assessment

It has been previously suggested that multiple sclerosis (MS) patients are at increased risk for osteoporosis due to reduced mobility, decreased exposure to sunlight and recurrent steroid treatment. In order to systematically evaluate bone strength we assessed 256 MS patients (171 females, 75 males) through quantitative ultrasound measurement of cortical bone. Tibial speed of sound (SOS, m/sec) was measured at midpoint of the tibial shaft using a Soundscan 2000 (Myriad Ultrasound Systems, Rehovot, Israel) and results were compared to age- and gender-matched population norms. T-score distribution in male MS patients was similar to normal population. In contrast, for female MS patients T-score distribution was significantly different from population norms, reflected by increased SOS in 30.4% (T-score intervals 1-2 and >2 above normal values; P=0.001), compared with 7.4% in controls. These findings held true for both female patients younger and older than 45 years of age. Increased neurological disability and specifically motor involvement were more frequent in female patients with increased SOS (P<0.05). Bone strength was preserved in MS patients. In a subgroup of female patients increased SOS was conceivably related to spasticity.