Introduction 

Croup is an upper respiratory infection, that can present unique challenges to young children with neuromuscular disorders (NMDs), such as muscular dystrophy (MD) or spinal muscular atrophy (SMA), due to their weakened respiratory muscles. This combination can lead to more severe respiratory symptoms and potential complications, requiring specialized medical attention and interventions. Understanding the relationship between the two is crucial for healthcare professionals and caregivers to identify accurately in providing effective treatment and management. 

This article aims to explore the relationship between croup and neuromuscular disorders, highlighting the potential risks and considerations in the provision of optimal care for the vulnerable population. 

Understanding croup 

Croup (laryngotracheobronchitis) is a respiratory tract infection among infants and young children, causing upper airway oedema and inflammation, along with laryngeal mucosa resulting in the narrowing of the subglottic region. Among the various croup-causative viruses, human parainfluenza virus is the most common pathogen, others include influenza A and B viruses, coronavirus, and adenovirus. The infection would lead to narrowing of the airway, resulting in a characteristic abrupt barky cough and difficulty breathing, typically appearing in late fall.¹ 

Signs and symptoms 

Croup typically begins with a mild upper airway infection, with low-grade fever. As the condition progresses, the child develops an abrupt, harsh barking cough, accompanied by a hoarse voice, and noisy inhalation. The symptoms are mostly short-lived, worse at night, leading to sleep disturbances, yet with rapid fluctuations depending on the child’s emotional status. In severe cases, inspiratory stridor could be induced, leading to respiratory distress, with rapid breathing and retractions.¹

Risk factors

Several risk factors contributing to croup development are as follows:^1,2

• Age: Susceptible to 6 months infants to 3 years young children
• Season: More common during the fall and winter months
• Allergies and asthma: Cause respiratory inflammation
• Tobacco smoke exposure: Secondhand smoke-irritated and inflamed airways, increasing susceptibility to respiratory infections
• Family history
• Exposure to viral infections

Understanding neuromuscular disorders 

Definition and types of neuromuscular disorders

Neuromuscular disorders are a group of conditions involving the nerves controlling voluntary muscles. Characterised by impaired neuromuscular communication, leading to weakness, muscle wasting, and difficulties with movement. The various NMD subtypes are plexopathies, anterior horn cells, nerve roots, peripheral nerves, neuromuscular junction, and muscular conditions. These disorders can be inherited or acquired, and their severity and progression vary widely.³ 

Common neuromuscular disorders affecting respiratory function 

NMD can have a significant impact on respiratory functions. Here are a few examples of young children:⁴ 

• Spinal muscular dystrophy (SMA): Genetic disorder that leads to progressive (respiratory) muscle weakness. Infants with severe forms may experience respiratory distress, in need of respiratory support
• Muscular dystrophy (MD): Genetic progressive muscular degenerations, that could lead to respiratory weakness and insufficiency
• Congenital myopathies: Genetic muscular disorder affecting tone and strength, could potentially weaken respiratory muscles, leading to breathing difficulties
• Myasthenia Gravis (MG): Though rare among children, is an autoimmune neuromuscular junction disorder affecting muscles, respiratory muscles can be affected when severe, causing respiratory distress, and even failure

Impact of neuromuscular disorders on airway management

NMD poses significant challenges to airway management by weakening the phrenic nerve and breathing muscles, in lead to respiratory muscle weakness, and reducing the expiratory muscle length-tension, and chest wall recoil force, impairing cough reflexes and limiting secretion clearance.

Thereby increasing the risk of airway obstruction and respiratory complications. While swallowing difficulties, aspiration, gastroesophageal reflux, and immune dysfunction risks are common. Sleep-disordered breathing, impacting the quality of rest, could also exacerbate respiratory compromise.^5,6

Croup among neuromuscular disorders

Unique challenges in diagnosis and management

Atypical presentation

Due to compromised respiratory function, NMD patients may exhibit atypical symptoms of croup. Such as less pronounced or absent barking cough and stridor with more prominent increased work of breathing or behavioural changes. These make croup diagnosis among the NMD population will become more challenging. 

Limited vocalization

Dysarthria are common among NMD patients, in which they may have limited vocalisation abilities. This can hinder their accurate expression ability to express symptoms or discomfort related to croup accurately, making diagnosis and monitoring more challenging.^7,8

Impaired airway clearance

Croup involves upper airway inflammation and swelling, which further compromise the already weakened respiratory muscles among the NMD population. The impaired ability to clear secretions and maintain a patent airway increases the risk of airway obstruction and exacerbates respiratory distress.⁶

Challenging treatment administration

Administering medications for croup might be challenging due to dysphagia, coordination issues, or the need for specialised equipment among NMD individuals, which could complicate the administration process, requiring careful adaptation and support.⁹

Potential complications associated with croup 

Due to the underlying neuromuscular respiratory impairments, NMD patients are more vulnerable to the following complications:^6,10

• Airway obstruction
• Retractions 
• Hypoxemia 
• Cyanosis
• Respiratory failure 
• Aspiration pneumonia 
• Increased susceptibility to secondary infections 

Management and treatment

Medical interventions for croup among neuromuscular disorders

Pharmacological treatments 

Glucocorticoids

Glucocorticoids are a type of steroid that decreases the swelling of the voice box (larynx), typically within six hours of the first dose. While dexamethasone and prednisolone are the most often used glucocorticoids, one dose will usually need to be taken by your child orally. If your child is experiencing severe bulbar weakness that affects their oral intake, intravenous or intramuscular dexamethasone can also be given.¹¹ 

Nebulised breathing treatment (Epinephrine) 

Epinephrine will be given to your child as an inhaled mist (nebulizer), used to reduce the swelling of their airways, it usually starts to be effective within 10 minutes. Due to its less than 2 hours effectiveness, repeated treatment every 15020 minutes may be necessary if your child’s symptoms are severe.¹¹

Airway clearance techniques

Due to the already compromised oropharyngeal and respiratory muscles among NMD patients, airway clearance techniques become crucial for airway management, to reduce mucus retention and potential severe complications occurrence.^12,13 

Oxygen therapy and ventilatory support

For severe cases, the provision of humidified air or oxygen, even mechanical ventilation can help for respiratory support among NMD kids.^11,13

Multidisciplinary approach to croup management

NMD is an illness that affects different muscle groups, establishing a multidisciplinary and collaborative care approach, with coordination among healthcare professionals is essential in croup management to reduce the potential risk and complications among NMD patients.

Preventive measures 

Croup is contagious through physical contact and air. These can help your children with NMD from preventing it:¹¹

• Respiratory support: Work closely with your child’s healthcare team, including neuromuscular specialist and respiratory therapist, to ensure optimal respiratory function. The use of respiratory support devices, such as non-invasive ventilation (NIV), cough assist devices, or airway clearance techniques. Proper respiratory function management can reduce the risk and severity of respiratory infections.
• Personal hygiene: Teach or help your children to wash and dry their hands before eating or touching their face. Encourage them to avoid touching their face, eyes, or nose with unwashed hands, and also to cover their mouth and nose when coughing or sneezing.
• Avoid close contact with sick individuals: Limit your child’s contact with individuals who have respiratory symptoms, especially coughing or sneezing
• Environmental cleanliness: Regularly clean and disinfect the frequently touched places, especially the room or toys of your kids
• Avoid crowded places during increased respiratory infection periods
• Vaccinations: As croup is usually caused by viruses, ensure your children are up-to-date with their vaccinations, including routine childhood immunizations and influenza vaccines, to protect against various viral infections
• Regular medical checkups: Maintain regular checkups with your child’s healthcare providers, to monitor their overall health and discuss any concerns
• Caregiver education and training: Seek specific guidance from your child’s neuromuscular specialist or respiratory therapist on recognising and managing croup symptoms

Impact on quality of life and long-term outcomes 

Respiratory function and complications 

Not only can croup cause inflammation and swelling of the upper airway, leading to airway obstruction. This severe or recurrent episode of obstruction of croup can further impair the ability of children with compromised respiratory functions with NMD, exacerbating respiratory muscle weakness. Also heightened the risk of complications such as respiratory distress, pneumonia, atelectasis, or respiratory failure.^6,10

Exacerbation of underlying condition

Croup can worsen the symptoms and progression of underlying NMD. The increased respiratory effort and compromised respiratory function associated with croup can lead to a decline in overall muscle strength, including respiratory muscles, resulting in respiratory muscle fatigue, decreased lung capacity, and further respiratory compromise. 

Psychological impact 

Croup and its associated respiratory challenges can have psychological effects on children with NMD. The frequent respiratory distress, hospitalisations, and medical interventions may cause anxiety, fear and emotional distress. It can also affect the mental well-being of parents and caregivers responsible for the child’s care. 

Strategies for optimising quality of life and functional outcomes

• Individualised treatment plan among multidisciplinary care 
• Education and inclusion 
• Social integration and support network 
• Regular monitoring and adaptation 

Summary 

Croup is an upper airway inflammation that presents significant implications to children with neuromuscular disorders. While further compromising the weakened respiratory function, increasing distress and secretion-clearing difficulties. Due to their vulnerability to respiratory infection, early recognition, accurate diagnosis, and appropriate management are crucial, to reduce the heightened risk of pneumonia, respiratory failure, and underlying neuromuscular disorder exacerbation.

Regular monitoring by a comprehensive collaborative interdisciplinary team, involving healthcare professionals such as neuromuscular specialists, respiratory therapists, and physiotherapists is crucial in optimising the outcomes and quality of life of both the children with neuromuscular conditions and their families.