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  • Atrophy (of skeletal muscle): A reduction in the size of muscle fibres, the strength of the muscle, and the resistance to fatigue.

  • Autosomal recessive disorder: In an autosomal recessive disorder such as spinal muscular atrophy, 2 copies of an abnormal gene must be present in order for the disease or trait to develop. In other words, both parents must be carriers of the trait.

  • Bilevel positive airway pressure (BiPAP): A BiPAP machine provides 2 levels of positive airway pressure delivered via a mask (nasal/mouth). The machine delivers a higher pressure and increased volume when the patient inhales. On exhalation, the machine lowers the pressure to allow for a more normal breathing pattern.

  • Carrier: A carrier is an individual who carries and is capable of passing on a genetic mutation associated with a disease, though they may or may not display symptoms. Two carriers may produce a child with the disease.

  • Central nervous system (CNS): The CNS is the part of the nervous system that includes the brain and spinal cord.

  • Chromosome: A chromosome is an organised package of genetic material called DNA, which is found in the nucleus of a cell. The nucleus is the command centre of the cell, giving instructions to the cell to grow, mature, divide, or die. DNA, or deoxyribonucleic acid, is the genetic material found in humans and almost all other living organisms.

  • Cognition: The mental action or process of acquiring knowledge and understanding through thought, experience, and the senses.

  • Cough assist device: A cough assist device can be used (with a nose mask or mouthpiece) to help a child inhale and exhale. The machine pushes air into the lungs at a preset pressure and then sucks the air out of the lungs at a preset pressure.

  • Distal hereditary motor neuropathy or Type V SMA: This condition has a different genetic cause from SMA Types I-IV. Type V SMA is very rare and typically affects the hands and feet only, causing muscle weakness and wasting. Symptoms usually begin during adolescence, but may occur from infancy through the mid-thirties.

  • Durable medical equipment: Equipment and supplies ordered by a healthcare professional for everyday or extended use, such as a wheelchair or cough assist device.

  • Electromyography (EMG): A measurement that determines how muscles and the nerves that activate them are functioning at rest and during activity.

  • Gastrostomy tube (G-tube): A G-tube delivers liquid feedings directly to the stomach via a tube inserted through the abdomen. It is inserted during a brief surgical procedure and allows children with feeding problems to maintain proper nutrition and fluids.

  • Invasive ventilation: Invasive respiratory support usually describes the use of a mechanical ventilator, which is connected to the patient via an airway. This may require a tracheotomy and cuffed tracheostomy tube.

  • Motor neurons: Motor neurons (also known as motoneurons) are large neurons in the brain stem and spinal cord that activate skeletal muscle fibres, resulting in muscular contraction.

  • Nasogastric (NG) tube: An NG tube is passed down into the stomach through the nasal passage, allowing the caregiver to provide nutritional support and medication.

  • Nasojejunal (NJ) tube: A small tube that is passed through the nose and guided into the jejunum (small bowel). The tube allows the caregiver to provide nutritional support.

  • Noninvasive (NIV) respiratory care: This term usually refers to respiratory support (including bilevel positive airway pressure, or BiPAP, ventilation) that does not require endotracheal intubation (breathing tube) or tracheostomy (trach tube). The short-term goals of NIV include relief of respiratory distress, reduced work of breathing, improved oxygenation, and making the patient more comfortable. Ultimately, the purpose is to help support the patient’s respiratory function while avoiding the need for tracheotomy.

  • Nonsitters: Children with spinal muscular atrophy who are not able to sit independently.

  • Palliative care: The type of patient care that aims to improve the quality of life for patients with a life-threatening illness. Palliative care is intended to relieve pain and other symptoms that can cause the patient distress and discomfort. This approach does not mean that the patient is near death. According to the World Health Organization, palliative care in children is best accomplished by a multidisciplinary care team that includes the family.

  • Proximal muscles: The proximal muscles are those closest to the centre of the body.

  • Pulmonologist: Pulmonologists are internal medicine doctors with specific expertise and experience in the treatment of diseases of the lungs and the management of breathing disorders.

  • Referral: An order or permission granted by the primary care provider to receive specialty care.

  • Scoliosis: A deviation in the normally straight vertical line of the spine—causing the spine to take on an S-shaped curve.

  • Sitters: This term describes those children with spinal muscular atrophy who can sit without assistance but cannot walk independently.

  • Spinal

    Spinal muscular atrophy (SMA)

    Infant-onset SMA (also known as Werdnig-Hoffmann disease or Type I SMA): Infant-onset is the most severe form of SMA, comprising 60% of all cases of the disease. It is often diagnosed during an infant’s first 6 months of life. Affected individuals are unable to sit and are also referred to as “nonsitters”.

    Intermediate SMA (also known as Dubowitz disease or Type II SMA): Intermediate SMA is usually diagnosed between 7 and 18 months. Affected individuals can typically sit up (also known as “sitters”) without help, though they may need assistance getting into a seated position. However, they are typically unable to walk and may require a wheelchair.

    Juvenile-onset SMA (also known as Kugelberg-Welander disease or Type III SMA): Juvenile-onset SMA is usually diagnosed after 18 months of age, but before the child is aged 3 years. Individuals affected by Type III SMA are initially able to walk (also known as “walkers”), but may lose mobility as they grow, and may eventually need to use a wheelchair.

    Adult-onset SMA (also known as Type IV SMA): This type of SMA is very rare. Mild motor impairment is seen in adulthood. Symptoms can begin as early as age 18, though they often begin after age 35.

  • Spinal muscular atrophy with respiratory distress (SMARD): SMARD is a variant of Type I SMA. Infants with SMARD are in severe respiratory distress because they have extremely weak breathing muscles.

  • Survival motor neuron 1 (SMN1) gene: The SMN1 gene produces a protein called survival motor neuron protein (SMN protein), which is important for the maintenance of specialised nerve cells called motor neurons. Without SMN protein, motor neurons die, and nerve impulses are not passed between the brain and muscles. As a result, some muscles cannot perform their normal functions, leading to weakness and impaired movement.

  • Survival motor neuron 2 (SMN2) gene: Also called the SMA “back-up gene”. Several different versions of the SMN protein are produced from the SMN2 gene, but only one version is full size and functional.

  • Tracheotomy: A tracheotomy is a surgical procedure to create an opening through the neck into the trachea (windpipe). A tube (tracheostomy tube) is usually placed through the opening to provide a secure airway and enable the removal of secretions from the lungs.

  • Ventilation (mechanical ventilation): A mechanical ventilator is a machine that helps people breathe when they’re unable to breathe sufficiently on their own. Mechanical ventilation can be noninvasive, using nose/mouth masks, or invasive, involving endotracheal intubation.