Researchers at Kaohsiung Medical University Hospital, Taiwan studied the prevalence and risk factors of feeding and swallowing problems in 108 genetically confirmed patients with types II and III spinal muscular atrophy (SMA), age range 3-45 years, 60 with type II and 48 with type III. A questionnaire survey showed the 3 most common feeding and swallowing difficulties were choking (30.6%), difficulty conveying food to the mouth (20.4%), and difficulty chewing (20.4%). Motor function status (sitters vs walkers) was an independent risk factor for feeding and swallowing difficulties; 28 were walkers, 76 sitters, and 4 nonsitters. All 4 SMA II nonsitters had feeding and swallowing difficulties. Poor head control when feeding was a factor in 13 (12%) patients. Age was not an independent risk factor in this study; 10 patients, all with type II SMA and age <20 years (range 3-19 years), had feeding and swallowing difficulties and required respiratory management. Respiratory assistance or suction was required in 17 patients (15.8%). Patients with feeding and swallowing difficulties had higher rates of underweight and aspiration pneumonia than those without these problems. Individual treatment plans for SMA II/III patients should depend on motor function status. [1]

COMMENT. Classification of SMA types I, II, III, and IV is based on age at onset and the highest function achieved [2]. In a Hong Kong, China study [3] survival probabilities for type I SMA (n=22) at 1, 2, 4, 10, and 20 years were 50%, 40%, 30%, 30%, and 30%, respectively. For type II SMA (n=26), survival probabilities at 1, 2, 4, 10, and 20 years were 100%, 100%, 100%, 92%, and 92%, respectively. Sixteen of the SMA I patients and 4 of the SMA type II patients died of cardiorespiratory failure. All SMA III patients were surviving. The probability of remaining ambulatory at 20 years after onset of type IIIa (age of onset <3 years) was 50%, and for type IIIb (age of onset 3-30 years) it was 68%. Interval between disease onset and inability to walk was 15 years for type IIIa and 21.2 years for type IIIb patients. In the Taiwan study, feeding and swallowing difficulties, especially choking, in SMA types II and III patients were correlated with current motor function status.

Double-trouble: SMA type II and seropositive myasthenia gravis in a 51 yr old male [4]. A case report from Finland concerned a patient with SMA type II living to age 51 years and then developing worsening of dysphagia and chewing over a few weeks. A mild respiratory infection led to rapid deterioration in ventilatory function and need for tracheostomy and permanent night-time ventilator support. Ptosis of left eye, ophthalmoplegia, myopathic face, and left hand weakness followed. Serum acetylcholine receptor antibodies were elevated (44 nmol/L; normal 0.25-0.40 nmol/L), and edrophonium testing for myasthenia gravis was positive. CT chest was negative for thymoma or thymus hyperplasia. Myasthenia responded to a course of iv immunoglobulin, oral prednisone, and pyridostigmine. Azathioprine was substituted for the prednisone. Ocular findings are very atypical for SMA and a diagnosis of MG was suspected as a chance association of two rare diseases.