Natural history of spinal-bulbar muscular atrophy

Background: Although spinal-bulbar muscular atrophy (SBMA) is generally believed to be associated with better survival and function compared to other motor neuron diseases, no systematic study of long-term functional status or survival has been reported. Methods: We report the results a retrospective review of 39 patients with genetically confirmed diagnosis and compared their survival to normal, population-based, age-and gender-matched controls. We assessed the functional status of 25 of the 33 survivors by completing the revised ALS Functional Rating Scale (ALSFRS-r) by telephone. Results: The subjects with SBMA had a 10-year survival of 82% compared to 95% among the age-matched controls (p = 0.053). The mean ALSFRS-r score for the survivors was 37 (range 27 - 43). The ALSFRS-r subscores indicated mild deficits in all areas in most, with the greatest limitation being the use of stairs. While all reported bulbar symptoms, none had disabling deficits. None of the subjects required a percutaneous endoscopic gastrostomy tube and one subject used noninvasive positive pressure ventilation. Conclusions: The long-term survival of subjects with spinal-bulbar muscular atrophy is minimally reduced from their age-matched controls. The long-term functional assessments demonstrate mild neurologic impairment in most without devastating bulbar or respiratory dysfunction and good ambulatory function years after diagnosis.