Amyotrophic Lateral Sclerosis (ALS) spreading pattern and detection of findings that can predict the development of respiratory failure in ALS patients

BACKGROUND: In ALS, respiratory complications are important in the prognosis of the disease. The aim of this study was to determine the electrophysiological findings that may predict respiratory failure and evaluate the pattern of ALS spread. MATERIAL- METHODS: According to the Awaji electrodiagnostic criteria, 30 patients with ALS who were diagnosed as definite or probable ALS but without respiratory failure were included in the study. The patients were examined at intervals of 2-4 months. Neurological examination, nerve conduction studies, needle electromyography (EMG) and single breath count test were performed in all patients. In the upper extremity, median and ulnar nerve sensorial and motor conduction studies; in the lower extremity, fibular and posterior tibial motor nerve conduction studies and sural nerve sensory conduction studies were performed. Bilateral phrenic nerve conduction studies were also performed. The activity of the bilateral lower extremity and upper extremity muscles (at least 3 muscles), abdominal muscles, paraspinal muscles, intercostal and cranial muscles were recorded electromyographically using needle electrodes. In addition, patients pulmonary function tests, swallowing electromyography, arterial blood gas analysis were recorded and evaluated. Patients were followed until respiratory failure developed. RESULTS: At the end of the 18-month follow-up period, 26 of 30 patients developed respiratory distress. Neurological examination and other tests were performed on average 3-4 times during follow-up. The sociodemographic and clinical data of the patients were found to be consistent with the literature. It was noted that the coexistence of clinical findings of upper motor neuron (UMN) and lower motor neuron (LMN) was prominent in all segments with disease progression and neurogenic changes were increased in all segments in EMG examinations. There was also a statistically significant decrease in ALSFRS-R scores with disease progression. During follow-up, half of the patients who developed respiratory failure had sternocleidomastoid (SCM) muscle with the latest neurogenic EMG findings. In addition, respiratory distress was developed in the patients immediately after SCM and rectus abdominis muscles participated in respiratory effort. It was found that prolongation of phrenic nerve latency and increased amplitude of diaphragmatic combined muscle action potential were directly related to respiratory failure. Despite the development of respiratory failure, arterial blood gas analysis was normal in the most of patients. Most of the patients who developed respiratory failure could not perform effective pulmonary function test (PFT) because of weakness in facial and bulbar muscles. A statistically significant decrease in FVC values was observed in proportion to disease progression and respiratory failure. CONCLUSION: Although there are many studies of ALS, there is no reliable test for early detection of respiratory failure. In our study, although the number of cases were not sufficient, neurogenic EMG findings detected in SCM muscle and participation of respiratory muscles such as SCM and rectus abdominis in respiratory effort could be predictive for the development of respiratory failure. Despite the development of respiratory failure, arterial blood gas analysis was normal in most patients. Therefore, it was thought to be limited in the follow-up of respiratory failure. Also, it was observed that the majority of the patients who developed respiratory failure could not perform effective PFT and single breath count test. It was observed that these tests use was limited as the disease progressed. Phrenic nerve conduction studies were found to be directly related to respiratory failure but not a good marker in the early period. Phrenic nerve conduction studies were found to be directly related to respiratory failure but not a good marker in the early stage. To sum up, the presence of neurogenic changes in certain muscles in needle EMG and demonstration of the participation of the certain accessory muscles in respiration can be used as an electrophysiological marker to predict the development of respiratory failure. There is a need for further studies by increasing the number of cases and designing longer-term follow-up.