A retrospective review was done on all patients with SMA and MD undergoing spinal surgery on a neuromuscular protocol. Baseline demographics, perioperative results, and long-term outcomes were collected. Per the protocol, patients remained intubated after surgery and were transported to the intensive care unit (ICU) for extubation. We present the results of protocol implementation and compare patients with MD to those with SMA.
Twenty-four patients were treated using the protocol. Average age was 13.1 years. Severe restrictive lung disease was present in 75% of patients. Nocturnal BiPAP was required in 68% of patients. Average number of instrumented levels was 17. All patients were immediately extubated upon entering the ICU. There were three respiratory complications and only was patient was re-intubated. Average ICU stay was 1.8 days and average hospital length of stay was 6.7 days. No differences in postoperative inspiratory or expiratory positive airway pressures were observed between the MD and SMA groups.
Through a multidisciplinary neuromuscular protocol, excellent clinical outcomes were achieved in patients with neuromuscular scoliosis and restrictive lung disease, with complication rates and length of stay significantly lower than previously published data 1)
Hooijmans et al. from The Netherlands evaluated 13 patients with SMA and 15 controls with a 3T MRI protocol consisting of DIXON method, DTI, and T2 sequences. qMRI measures were compared between groups and related to muscle force measured with quantitative myometry. The fat fraction was significantly increased in all upper arm muscles of the patients with SMA compared to controls and correlated negatively with muscle force. Additionally, the fat fraction was heterogeneously distributed within the Triceps Brachii (TB) and Brachialis (BR) muscle but not in the Biceps Brachii (BB) muscle. Diffusion indices and water T2 relaxation times were similar between patients with SMA and healthy controls but we did find a slightly reduced MD, λ1 and λ3 in the TB of patients with SMA. Furthermore, MD positively correlated with muscle force in the TB of patients with SMA. The variation in fat fraction further substantiates the selective vulnerability of muscles. The reduced DTI indices along with the positive correlation of MD with muscle force point to myofiber atrophy. The results showed the feasibility of qMRI to map disease state in the upper arm muscles of patients with SMA. Longitudinal data in a larger cohort is needed to further explore qMRI to map disease progression and to capture possible effects of therapeutic interventions 2).
Iannaccone et al. published a retrospective chart review of all SMA patients seen at a single site between 2016 and 2020 for treatment with nusinersen.
They reported 8 patients who underwent placement of an Ommaya reservoir and lumbosacral catheter for drug delivery. Complications included infection and revisions due to catheter separation. One patient required fluoroscopy for injections because of the location of the port site.
They conclude that the placement of an Ommaya port is a viable option for patients who have challenges with access to intrathecal space. Practical innovations have the potential to control administration costs, achieve therapeutic value, and promote patient safety 3).
Habets et al. recorded surface electromyography (sEMG) of various muscles of upper- and lower extremities of 70 patients with spinal muscular atrophy (SMA) types 2-4 and 19 healthy controls performing endurance shuttle tests (ESTs) of arm and legs. They quantitatively evaluated the development of fatigability and motor unit recruitment using time courses of median frequencies and amplitudes of sEMG signals. Linear mixed-effect statistical models were used to evaluate group differences in median frequency and normalized amplitude at onset and its time course.
Normalized sEMG amplitudes at the onset of upper body ESTs were significantly higher in patients compared to controls, yet submaximal when related to maximal voluntary contractions, and showed an inverse correlation to SMA phenotype. sEMG median frequencies decreased and amplitudes increased in various muscles during execution of ESTs in patients and controls.
Decreasing median frequencies and increasing amplitudes reveal motor unit reserve capacity in individual SMA patients during ESTs at submaximal performance intensities.
Significance: Preserving, if not expanding motor unit reserve capacity may present a potential therapeutic target in clinical care to reduce fatigability in individual patients with SMA 4).