Long-term follow-up of spinal and bulbar muscular atrophy in Taiwan

Abstract

Spinal and bulbar muscular atrophy (SBMA), also known as Kennedy disease, is a rare neurodegenerative disorder presenting with insidious onset of weakness in bulbar and limb muscles. Information regarding long-term clinical and functional progression has been limited, especially for the Taiwanese population. The purpose of the study aimed to investigate early diagnosis and long-term prognosis of SBMA. We retrospectively analyzed 21 genetically confirmed SBMA patients who visited our hospital between 1993 and 2010, focusing on clinical symptoms, nerve conduction studies, and functional disability. We also analyzed the relationship between length of cytosine-adenine-guanine (CAG) repeats and age of disease onset. Weakness developed at a mean age of 39±7 years (mean±standard deviation). The length of CAG repeats and age at onset of weakness showed inverse (but nonsignificant) correlation. The most common symptoms at initial presentation were hand tremor (86%), limb weakness (86%), and perioral fasciculation (76%). Creatine kinase (CK) was elevated in 17 out of 18 patients. Initial nerve conduction studies showed statistical difference from normal controls, especially decreased amplitudes of compound motor action potential (CMAP) and sensory nerve action potential (SNAP). Functional disability showed very slow progression, with only three patients becoming wheelchair-dependent during follow-up at a median age of 72 years. Patients with SBMA may present with a myriad of symptoms, including limbs weakness, tremor, muscle atrophy, and perioral fasciculations. Elevated serum CK and decreased CMAP and SNAP amplitudes were supportive laboratory findings of SBMA. Disease progression was gradual, and most patients remained functionally independent many years after the onset of weakness.