Hypotonia
Hypotonia is a congenital, non-progressive neuromuscular disorder characterized by decreased skeletal muscle tone and generalized muscle weakness. The condition may occur as a disorder of unknown cause, or as a symptom of other neuromuscular diseases.
Individuals with hypotonia frequently suffer from an inadequate gag reflex and tongue movements. Consequent swallowing and feeding difficulties may be associated with aspiration or gastroesophageal reflux. Weakened respiratory muscles and an impaired ability to cough may lead to the retention of pulmonary secretions and aspirate in the lungs. Concomitant central nervous system disturbances, such as seizures, occur commonly in this patient population.
Airway clearance indications associated with hypotonia include:
Dysphagia: Impaired swallowing as a result of inadequate bulbar function or dysphagia may lead to aspiration. Aspiration of salivary or gastric contents introduces bacteria into normally sterile airways, resulting in pulmonary infection.
Weakened Respiratory Muscles: Inadequate control of respiratory muscles due to denervation or hypotonia can impair the normal cough reflex and, as a result, interfere with the ability to clear aspirated material and pulmonary secretions from the airways.
Seizure activity: Seizures carry a high risk for aspiration of saliva and gastric contents. Because saliva and gastric contents contain bacteria, aspiration introduces microorganisms into normally sterile airways.
Forced immobility: Inability to exercise may diminish aerobic capacity, bellows function, and lung volume, resulting in restrictive lung disease. The consequent inability to generate a large inspiratory or expiratory force or to cough effectively may lead to retained secretions.
Retained secretions: Ineffective clearance of pulmonary secretions can lead to secretion retention and pooling. Retained secretions are an ideal growth medium for bacterial pathogens. Consequent infections produce still more mucus, initiating a vicious cycle of mucus obstruction, recurrent bouts with pneumonia, bacterial colonization, and progressive pulmonary compromise.
Aggressive bronchial hygiene, including daily Airway Clearance Therapy, is an essential component in the management of patients with pulmonary complications from hypotonia. Conscientious attention to daily secretion clearance may prevent or minimize the pulmonary complications associated with this disorder.
Sources
:
1. Thoene JG, ed. Physicians' Guide to Rare Diseases. Dowden Publishing. Montvale, NJ. 1995;
305.
2. Andersson PB, Rando TA. Neuromuscular Disorders of Childhood. Current Opinion in Pediatrics 1999. 11(6):497-503.
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