Vocal cord abductor paralysis (VCAP) is considered a sign of a poor prognosis in neurodegenerative diseases, because severe laryngeal dysfunction by VCAP may result in acute airway obstruction and require emergency tracheotomy.1

Although VCAP is a cardinal feature in multiple system atrophy (MSA), it has not been reported in several types of spinocerebellar ataxia with dominant inheritance. We evaluated the movements of the vocal cords of seven patients with SCA1 by laryngofibroscopy.

Seven unrelated patients with SCA1 who had the expanded CAG repeat of ataxin-1 were investigated. There were two men and five women ranging in age from 27 to 67 years old (mean 44.5 years). Spouses and other family members, in addition to the patients, were questioned about events of stridor, dyspnoea, and dysphagia. Vocal cord movement was examined by laryngofibroscopy and recorded during inspiration and phonation. The rating scale used to evaluate maximal abduction of the vocal cords during larygofibroscopy was as follows: (-)=normal; (+)=median position; (++)=paramidline position; (+++)=midline position. For the evaluation of VCAP, we tried the respiratory flow volume loop study as well in one patient (patient 2) in whom maximal abduction of the vocal cords was slightly limited (+) on laryngofibroscopy.

The correlations between VCAP and CAG repeat length or duration of illness were analysed with the non-parametric Mann-WhitneyU test.

The clinical features, including the vocal cord findings, are summarised in the table. VCAP was present in five of the seven patients with SCA1. Although it is difficult to know when the VCAP first became manifest in each patient, patient 1 showed VCAP confirmed by laryngofibroscopy only 2 years after the onset of gait disturbance.

All five patients with VCAP showed mild dysphagia requiring no tube feeding, and four patients had a history of stridor at night. Patient 1 showed VCAP accompanying dysphagia without stridor at night even in an early stage of the disease. The VCAP was found to be severe on laryngofibroscopy in all three patients with breathing difficulty on inspiration. Patient 5, who had the severest VCAP, developed stridor during wakefulness as well. In patients 4 and 5, the breathing difficulty on inspiration was improved by tracheostomy. The respiratory flow volume loop study did not detect abnormality in patient 2.

The CAG repeat number tended to be higher in the patients with VCAP than in the patients without VCAP (p=0.05), but the duration of illness was not significantly correlated with the presence of VCAP (p=0.43).

This is the first report that VCAP is often found in patients with SCA1. As VCAP may not usually be a late feature in patients with SCA1, evaluation of VCAP is necessary even in early stages of the disease. It is not surprising to find VCAP in patients with stridor, because stridor is usually caused by airway obstruction of the larynx. However, VCAP was detected by laryngofibroscopy in a patient without stridor who had dysphagia. Furthermore, all patients with VCAP exhibited dysphagia. We therefore think that laryngofibroscopy should be performed in SCA1 patients with dysphagia as well as stridor.

The mechanism of VCAP may be divided into some types, the paralytic type, the non-paralytic type, and these two combined type.2 The first is possibly caused by loss of neurons in the nucleus ambiguus.2 3 The second is considered to be due to overactivity of the intrinsic laryngeal muscles.2 Stridor due to paralysis has been found to be more prominent in sleep than during wakefulness; whereas stridor by non-paralytic dysfunction has been found both during the daytime and during sleep.2 4 We suspect that the VCAP in patients with SCA1 may be dominantly paralytic, because the nucleus ambiguus is sometimes pathologically involved in SCA1 and because stridor in our patients with SCA1 was more marked in sleep.5

Our laryngofibroscopic findings suggested that severe VCAP caused breathing difficulty on inspiration in the patients with SCA1 by obstructing the airway. Moreover, the stridor during wakefulness as well as sleep indicated it to be very serious. The important question concerns when tracheostomy should be carried out after the diagnosis of VCAP to prevent respiratory abnormalities leading to sudden death. Although we consider tracheostomy at the stage when breathing difficulty on inspiration or stridor during wakefulness is noted, it awaits further study with a large number of patients to decide which stage is best for tracheostomy.

Furthermore, we now consider endoscopic cord lateralisation as another possible management for VCAP.