Bilateral Vocal Cord Paralysis: A Rare Onset of Amyotrophic Lateral Sclerosis

We read with great interest the neurological review about vocal cord dysfunction in amyotrophic lateral sclerosis (ALS).¹ We agree that vocal cord dysfunction, including hoarseness and stridor, may be part of the clinical picture of ALS but in our experience they are quite rare at onset; of 350 patients diagnosed with ALS in the province of Modena from 1990 to the present, only 1 patient had stridor at onset. This 74-year-old man without a family history of ALS presented to the emergency department after a 6-month history of persistent hoarseness. He had dyspnea associated with hoarseness and stridor. Neurological examination revealed fasciculations of the tongue and 4 limbs. Dysarthria, dysphagia, and sensory, extrapyramidal, autonomic, and cerebellar signs were absent. Tendon reflexes were brisk. The laryngologist detected bilateral vocal cord abductor paralysis. Results of nerve-conduction studies were normal, and electromyograph revealed widespread acute and chronic denervation in the 4 limbs and bulbar region. Clinical and neurophysiological findings were consistent with ALS. Other diseases were excluded with appropriate tests. During his stay in hospital, respiratory distress increased with severe stridor. Noninvasive ventilation and partial cordotomy were ineffective. The patient agreed to perform tracheostomy to recover from acute respiratory distress. Spirometry showed mildly reduced forced vital capacity, arterious emogasanalysis was normal, and the patient did not need mechanical ventilation.

Although uncommon, stridor has been described as the first symptom of ALS.^{1 - 2} We think it is interesting that, in a large family with an inherited form of motor neuron disease (MND) caused by a G59S missense mutation of the p150Glued subunit of dynactin, affected members developed early bilateral vocal cord paralysis and prominent lower motor neuron signs.³ The postmortem study showed loss of motor neuron in the hypoglossal nucleus and not in the motor nucleus of the vagus nerve, suggesting a supranuclear origin of vocal cord palsy.³ However, we agree that in ALS bilateral vocal cord palsy can probably be of infranuclear or supranuclear type (lower or upper motor neuron involvement), as reported for extrapyramidal neurodegenerative diseases.¹

Given the similarities with the described inherited MND cases,³ we suggest that early vocal cord involvement may be a peculiar clinical feature of ALS associated with dynactin disfunction. Recently, the role of dynactin dysfunction in ALS has been demonstrated,⁴ suggesting that dynactin gene mutations may be a susceptibility factor for ALS.

Further genetic and pathological studies of dynactin in ALS are needed.

Correspondence: Dr Mandrioli, Clinica Neurologica, Dipartimento di Neuroscienze, Nuovo Ospedale Civile S. Agostino Estense, Via Giardini 1355, 41100 Modena, Italy (j.mandrioli@ausl.mo.it).

Financial Disclosure: None reported.