Neuromuscular Disorders

Amyotrophic Lateral Sclerosis (ALS)

Definition
According to the ALS association, Amyotrophic Lateral Sclerosis (ALS), often referred to as Lou Gehrig's Disease, is a progressive neurodegenerative disease that affects nerve cells in the brain and the spinal cord. Motor neurons reach from the brain to the spinal cord and from the spinal cord to the muscles throughout the body. The progressive degeneration of the motor neurons in ALS eventually leads to their death. When the motor neurons die, the ability of the brain to initiate and control muscle movement is lost. With voluntary muscle action progressively affected, patients in the later stages of the disease may become totally paralysed.

Prevalence
It is estimated that Amyotrophic Lateral Sclerosis is one of the most common neuromuscular diseases worldwide with 1 to 2 individuals per 100,000 developing ALS each year worldwide1

Roughly fifteen people are newly diagnosed with ALS each day (= an estimated 5,000 people each year) in the United States alone1.

Patient Profile

  • People of all races and ethnic backgrounds can be affected, men more often than women

  • ALS most commonly strikes people between 40 and 60 years of age, but younger and older people can also develop the disease1

  • Most people with ALS die from respiratory failure, usually within 3 to 5 years from the onset of symptoms

  • However, about 10-20 percent of individuals with ALS survive for 10 or more years

Chronic/Long-Term Ventilation Indications

  • FVC < 50% predicted 

  • MIP <60% predicted

  • Chronic daytime hypercapnia with PaCO2 ≥ 45mmHg

  • Nocturnal hypercapnia with PaCO2 ≥ 50mmHg

  • Daytime normocapnia with a rise in PTcCO2 of ≥ 10mmHg during the night

  • 20% drop of VC in supine position: decline in supine FVC >20% 

    Tracheostomy and permanent positive pressure ventilation can prolong life. With permanent ventilation in place, patients may survive many years. The risk of a “locked in” stage should be discussed with the patient and family in advance. Patients often require placement in a nursing home as care at home relies on the availability of continuous care1.

Duchenne Muscular Dystrophy (DMD)

Definition
Duchenne Muscular Dystrophy (DMD), is defined by WHO as a neuromuscular disease characterised by rapidly progressive muscle weakness. The disease primarily affects males and onset occurs early. People with the disease usually die in young adulthood, succumbing to cardiomyopathy, the effect of the disease on the heart muscle and respiratory failure.

Prevalence
The disease affects one in 3500 males, making it the most prevalent of muscular dystrophies1.
Every year, an estimated 20,000 babies (almost all of them boys) are born with DMD worldwide2.

Patient Profile

  • In general, only males are afflicted, though females can be carriers

  • Symptoms usually appear before the age of 6 and may be visible in early infancy

  • By age 10, leg braces may be required to aid walking, but most patients are wheelchair dependent by age 12

  • The average life expectancy varies from early teens to mid 30s1

Chronic/Long-Term Ventilation Indicators                                                                
According to the ATS consensus statement3 patients with DMD should be taught strategies to improve airway clearance and how to employ those techniques early and aggressively. Use of assisted cough technologies in patients whose clinical history suggests difficulty in airway clearance, or whose peak cough flow is less than 270 L/minute and/or whose maximal expiratory pressures are less than 60 cm H2O. Home pulse oximetry is useful to monitor the effectiveness
of airway clearance during respiratory illnesses and to identifypatients with DMD needing hospitalisation. Consider daytime ventilation when measured waking PCO2 exceeds 50 mmHg (or when haemoglobin saturation remains < 92% while awake). In centres with appropriate expertise, mouthpiece intermittent positive pressure ventilation or other forms of non-invasive daytime ventilation can be considered. Consider tracheostomy when contraindications or patient aversion to non-invasive ventilation are present4.  

Myotonic Dystrophy (Steinert's Disease) & Other Myopathies

Definition
It is the most frequent adult onset neuromuscular disorder, with a worldwide prevalence of 14 cases per 100,000 people. It is more than 10 times higher in the Saguenay-Lac-Saint-Jean region of Quebec1. It is an autosomal dominant disorder resulting from an unstable myotonin kinase gene at 19q133. Respiratory involvement is very common in MD, caused by a combination of respiratory muscle weakness and altered central ventilatory control2. Alveolar hypoventilation, ineffective coughing, microatelectasis, and reduction in compliance result in disproportionate hypercapnia from lung volume restriction3-4. These patients are prone to sleep-related breathing disorders (SRBD)5 and most progress from nocturnal hypoventilation to daytime chronic ventilatory failure.

Indicators

  • PcCO2 >45 mmHg

  • Significant nocturnal desaturation

  • FVC < 50% predicted

  • SNIP < 40 cmH20

  • MIP <60% predicted

  • 20% drop of VC in supine position