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Laryngeal abductor paralysis (LAP) and stridor are well known features that occur in over one third of patients with multiple system atrophy (MSA).1 The pathogenesis of LAP is thought to be crico-arytenoid abductor muscle denervation,2 although there is a lack of consistent evidence of motor cell loss in the nucleus ambiguus.2,3 More recently, dystonia of the laryngeal adductor muscle has also been proposed.4 LAP/stridor usually occurs in the advanced stages of the disease,6 and is considered to be a poor prognostic feature.1,2 In contrast, some MSA cases have shown LAP initially, with most of these reported by otolaryngology departments.5–7 However, there are no systematic surveys as to the extent to which MSA patients initially present with LAP. We describe the result of a survey of 200 MSA inpatients conducted in a neurology department.
We reviewed the case records of 200 consecutive “probable” MSA patients who met the inclusion and exclusion criteria.8 They were 119 men and 81 women, mean age 60 years; 29 had the Parkinsonian form (MSA-P) and 171 the cerebellar form (MSA-C). Among these, eight patients (4%) (four MSA-P, four MSA-C) were shown to have stridor as the initial manifestation (table 1). Stridor was the solitary manifestation in six of the patients, though it was combined with minimal laryngeal signs in two of these six patients (inspiratory gasp in one; hoarseness in one) and REM (rapid eye movement)-sleep related behavioural disorder (“night terror”) in one. In the remaining two patients stridor occurred together with bladder dysfunction or gait ataxia. In the former six patients, stridor was followed by bladder dysfunction in four, constipation in three, tremor/akinesia in one, ataxia in one, and postural hypotension in one. The average interval between the development of stridor and these later symptoms and signs was 3.3 years (range 1 to 6). The average interval between stridor and hospital admission was 5.4 years (1–10). In all eight patients, laryngoscopy confirmed that the stridor was caused by LAP. The grade of LAP at the first admission to our hospital (table 1), according to Isozaki’s laryngoscopy classification,9 was moderate (abductor paresis during waking; paradoxical adduction during sleep) in three and severe (complete paralysis) in five. Among those patients, continuous positive airway pressure was introduced in three, laser incision of the vocal fold was carried out in one, and subsequent tracheostomy was necessary in five.
In the cases presented, it proved true that LAP/stridor can be a solitary manifestation of MSA. The interval between LAP/stridor and hospital admission was rather long (on average 5.4 years), suggesting that the progression of LAP was not very rapid in those patients. Although the initial presentation of LAP/stridor was not common (it occurred in only 4% of all MSA patients), it is clinically relevant because patients with LAP/stridor but without obvious neurological symptoms may see general physicians or otolaryngologists first. Laryngeal stridor also occurs because of local inflammation or tumours, or from distant causes that affect the vagal nerves, such as upper thoracic or nasopharyngeal carcinoma. If such conditions have been excluded, central neurological causes should be considered. Co-morbid bladder dysfunction (particularly urinary incontinence and post-voiding residual volume of more than 100 ml), postural and postprandial syncope, parkinsonism, and ataxia are all red flags suggestive of MSA.10 In our eight patients, bladder dysfunction was an early sign and was chronologically correlated with LAP/stridor; this finding is in line with a previous report.9 These atypical features for a local laryngeal pathology suggest that further studies of the brain are necessary to confirm the diagnosis of MSA.
Published Online First 9 June 2005
Competing interests: none declared