Abstract
Objective
Spirometry is the most common test recommended to monitor respiratory dysfunction
in patients of amyotrophic lateral sclerosis (ALS). However, the test depends on the
patient's efforts and may be difficult to conduct in patients with faciobulbar weakness.
We aimed to study the role of phrenic nerve-electrophysiological studies to predict
respiratory dysfunction and correlate it with the forced vital capacity (FVC) in patients
of ALS.
Methods
Forty-three unselected patients (32 male, 25 with limb-onset ALS, age 50±15 years) with clinically definite or probable ALS were included. They were evaluated
at entry and after a period of 6 months with the ALS functional rating scale (ALSFRS), their respiratory subscores
(ALS-FRSr), their FVC values as determined by spirometry, and phrenic nerve studies.
Results
Six patients could not perform a satisfactory spirometry at the onset and during the
course of illness. All the six patients had severe faciobulbar weakness. Respiratory
abnormalities on spirometry were found in 85% of patients, whereas only 30% were symptomatic
for respiratory dysfunction. In patients with severe respiratory dysfunction (FVC<60%), the phrenic nerve motor amplitudes (PNAMPs) were significantly reduced compared
to those with mild-to-moderate respiratory dysfunction (FVC≥60%). The FVC value showed a significant correlation with the PN-AMP. Nine patients
had a poor outcome (death or severe disability) at the end of a period of 6 months. Low levels of both FVC and PN-AMP were predictors of poor outcome for patients
at the end of 6 months.
Conclusion
We conclude that respiratory dysfunction, as determined by spirometry, is common in
patients of ALS. However, only about one-third of patients show symptoms of respiratory
distress. Clinical symptoms of respiratory distress are unreliable predictors of respiratory
failure in ALS. Measurement of PN-AMP at the time of presentation may be an additional
tool to assess respiratory dysfunction in ALS. Reduced PN-AMP values may be indicative
of low FVC and may have some role in the assessment of respiratory function in patients
in whom a routine spirometry is not possible due to limitations arising from the illness.
Both low FVC and reduced PN-AMP at the time of presentation are predictors of poor
outcome for patients at the end of 6 months.
Keywords
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Article info
Publication history
Published online: April 15, 2011
Accepted:
March 24,
2011
Received in revised form:
March 19,
2011
Received:
November 27,
2010
Identification
Copyright
© 2011 Elsevier B.V. Published by Elsevier Inc. All rights reserved.
