Respiratory Function Changes as Early Signs of Amyotrophic Lateral Sclerosis.

BACKGROUND: The current diagnostic criteria for amyotrophic lateral sclerosis (ALS) may remain unsatisfactory for months or years in the early disease. Pulmonary assessment has never been considered useful in the early diagnosis of ALS, and studies of pulmonary function in this patient category are lacking. OBJECTIVES: The objective of this study was to assess the pulmonary function in subjects with unspecific symptoms of ALS in whom an ALS diagnosis cannot be reached based on the current available guidelines. METHODS: We performed pulmonary function tests, arterial gas analysis, maximal inspiratory (MIP) and expiratory (MEP) pressure, and respiratory drive (P0.1) assessment in 35 patients with unspecific neurological symptoms at the time of the visit and those were subsequently diagnosed with ALS 2 years after the initial visit ("pre-ALS"); we compared these patients with 29 patients with established ALS and with 28 control subjects. RESULTS: Spirometric parameters were not different between the three groups. However, MIP was significantly lower and P0.1 was significantly increased (with the ratio P0.1/MIP significantly higher) in both established and pre-ALS patients compared to controls, while both MIP and P0.1 were similar between established ALS and pre-ALS. CONCLUSIONS: Changes in MIP, P0.1, and P0.1/MIP ratio are highly suggestive of preclinical ALS when the spirometry and neurodiagnostic tests are still inconclusive. MIP and P0.1 are noninvasive measurements that can be easily assessed in an ambulatory setting. Future studies on larger cohorts are needed to validate the use of these parameters in the preclinical diagnosis of ALS as well as in other neuromuscular diseases.

Diagnosis of amyotrophic lateral sclerosis by respiratory function test.

The diagnostic criterion for amyotrophic lateral sclerosis (ALS) based on the findings of concomitant clinical and electrophysiological evidence of upper and lower motor neuron involvement may remain unsatisfied for months and in some patients, even for years in the early stage of the disease. Since respiratory involvement is an onset symptom of ALS in only 1-3% of patients, pulmonary assessment has never been considered useful in the early diagnosis of ALS. However, studies on pulmonary function are lacking, especially in those early stages where neurologic tests are also inconclusive. In contrast to the scarcity of data in the early stages, as the disease progresses, it is increasingly enriched by a rich set of symptoms and positive respiratory tests until respiratory failure occurs, which represents the main cause of death in ALS. Hereby we analyze the main pulmonary function tests (PFT) in the various stages of the disease, up to the recent evidence for the possibility of an early diagnosis.