Respiratory difficulty with palatal, laryngeal and respiratory muscle tremor in adult-onset Alexander's disease

Abstract

Sleep apnoea and respiratory difficulties are reported in adult-onset Alexander's disease (AOAD), an autosomal-dominant leukodystrophy that presents mainly with progressive ataxia. We demonstrate for the first time that the respiratory symptoms can result from association of palatal tremor with a similar tremor of laryngeal and respiratory muscles that interrupts normal inspiration and expiration.A 60-year-old woman presented with progressive ataxia, palatal tremor and breathlessness. MRI revealed medullary atrophy, bilateral T2 hyperintensities in the dentate nuclei and hypertrophic olivary degeneration (HOD). AOAD was confirmed genetically with a positive glial fibrillary acidic protein (GFAP) mutation. Electrophysiological study revealed 1.5 Hz rhythmic laryngeal and respiratory muscle activity. Her respiratory symptoms were significantly improved at night with variable positive pressure ventilation.This case illustrates that palatal tremor in AOAD, and potentially in other conditions, may be associated with treatable breathlessness due to a similar tremor of respiratory muscles.

Keywords: Mechanical ventilation; Movement disorders (other than Parkinsons); Neuroimaging; neurogenetics.

Figure 1

(A) Sagittal FLAIR MRI showing medullary and spinal cord atrophy. (B–D) Contiguous 5 mm slice axial T2-weighted MRI showing bilateral dentate signal hyperintensity (B) and bilateral signal hyperintensity in the anterior medulla with relative hypertrophy (C, D).

Figure 2

Power spectra of filtered and rectified surface electromyogram signal digitally sampled at 2000 Hz from right laryngeal, right respiratory and right sternomastoid muscles. There is a peak frequency in laryngeal and respiratory muscle activities at around 1.5 Hz that corresponds to the visible palatal and tongue tremor rhythm. This peak frequency is not present in sternomastoid muscle activity.