P015: ANESTHETIC MANAGEMENT OF TYPE 1 SPINAL MUSCULAR ATROPHY IN A 4-MONTH OLD FEMALE
Harshvardhan Rajen, MD1; Victor Wang2; Adryan Perez, MD1; Luis Rodriguez Alfonzo, MD2; Raul Fernandez Torrealba, MD2
1University of Miami/Jackson Memorial Hospital; 2Nicklaus Children's Hospital
Spinal Muscular Atrophy (SMA) is a genetic disorder that causes progressive muscle weakness and primarily affects the muscles responsible for movement. It involves the degeneration of motor neurons in the spinal cord caused by a deficiency in the survival motor neuron (SMN) protein, leading to the muscle atrophy characteristic of SMA.
SMA is divided into four main types, which are distinguished by the age of onset and severity of symptoms. Type 1 is the most severe, appearing within the first six months of life. Type 2 occurs between 6 and 18 months. Type 3 typically appears in late childhood or adolescence. Type 4 is the mildest, emerging in adulthood.
Our patient was a 4 month old female with a PMH of SMA type 1 who presented for tracheostomy and gastrostomy tube placement. The patient was originally admitted for failure to thrive and was transferred to the PICU after requiring intubation for acute hypercapnic respiratory failure. Genetic analysis revealed diagnosis of GARS 1 pathogenic variant causing infantile spinal muscular atrophy.
The patient was sedated and paralyzed in the PICU prior to transport using a bag valve mask and in-situ 3.0 cuffed endotracheal tube. Anesthesia was maintained via inhaled anesthetic and fentanyl boluses and nondepolarizing muscle relaxant. The patient tolerated the procedure without complication and was eventually discharged home several weeks later with a ventilator.
The anesthetic implications surrounding SMA depend on the type of disease and its severity. For all types of the disease there are some common considerations that must be taken into account for these patients when undergoing any anesthetic.
SMA type 1 is characterized by hypotonia with symmetric and rapidly progressive paralysis of the extremities, major respiratory failure caused by intercostal muscles paralysis, and typically early death. Anesthetic considerations would be the association with a hypoplastic left heart, ASD, or VSD, as well as midface hypoplasia causing difficulty with direct laryngoscopy.
With SMA type 2 vertebral abnormalities are possible. Development of a restrictive pulmonary syndrome and alveolar hypoventilation is likely. Also can be associated with gastroparesis, gastric dilation, midface hypoplasia, malnutrition. Anesthetic considerations would include severe scoliosis, growth retardation, paralysis of facial nerve and masseter contractures increasing the risk of difficult intubation.
SMA type 3 disease accounts for less than 15% of cases. The child is able to walk with difficulty, however scoliosis is quite common, as well as the development of cardiomyopathy. One of the main anesthetic considerations would be increased sensitivity to nondepolarizing muscle relaxants.
SMA type 4 accounts for less than 4% of cases. This is characterized by a progressive paralysis of the lower limbs with loss of the patellar reflexes. These patients can remain mobile until 50 years of age, without major change to life expectancy.
SMA type 0, or neonatal form, is associated with major hypotonia and respiratory distress at birth, involvement of the facial nerves. It can be identified on prenatal screening. It is a very severe form and unfortunately commonly seen with rapid death within the first months of life.