Exploratory evaluation of an eye-tracking system in patients with advanced spinal muscular atrophy type I receiving nusinersen

Analysis of Eye Movements in Adults with Spinal Muscular Atrophy

Background and Objectives: Spinal muscular atrophy (SMA) is a progressive, autosomal recessive, rare neuromuscular disorder caused by a genetic defect in the SMN1 gene, where the SMN2 gene cannot sufficiently compensate. Patients experience progressive and predominantly proximal muscular weakness and atrophy. Oculomotor disorders are currently not regarded as a typical feature of SMA. The aim of this study was to determine whether oculomotor abnormalities are present in subjects with SMA and to assess a potential relationship between the oculomotor parameters and disease duration. Materials and Methods: An analysis of 15 patients with SMA type 2 and type 3 and 15 age-matched healthy controls was conducted. The oculomotor performance, including the analysis of smooth pursuit velocity gain and saccades parameters (latency, velocity, accuracy) in the horizontal and vertical directions, was compared between both groups. Results: The analysis of smooth pursuit gain in the participants revealed a marginally significant reduction between the SMA patients and the healthy controls in the horizontal direction at a frequency of 0.2 Hz (p = 0.051), but no significant differences were observed at any other frequency or direction. The vertical velocity of the saccade eye movements of the SMA patients was increased compared with the healthy subjects, which was statistically significant for the amplitude of ±10° (p = 0.030), but not for the amplitude of ±16.5° (p = 0.107). The horizontal saccade latency, saccade velocity and saccade accuracy did not differ significantly between the SMA patients and the controls. None of the oculomotor parameters were associated with disease duration. Conclusions: While certain oculomotor abnormalities, such as increased vertical saccade velocity, were observed in the SMA patients, these findings do not indicate a defining role of oculomotor impairment in SMA pathology or its clinical characteristics.

Experience of nusinersen treatment in advanced spinal muscular atrophy type 1: Characteristics of late responders with delayed treatment efficacy

OBJECTIVE

Little clinical data is available for advanced cases of spinal muscular atrophy (SMA) type 1, particularly those requiring ventilation support. Therefore, this study aimed to evaluate the effectiveness of nusinersen treatment on motor and respiratory function in advanced cases of SMA type 1.

METHODS

This observational cohort study included seven patients with advanced SMA type 1, requiring permanent ventilator support and tracheostomy, at Hyogo Medical University School of Medicine Hospital between July 2017 and July 2019. The primary outcome was change in motor function, assessed using the Children's Hospital of Philadelphia Infant Test of Neuromuscular Disorders (CHOP-INTEND) score. Subjective changes, which could not be measured with CHOP-INTEND, were also evaluated. The secondary outcomes included changes in respiratory function, measured by tidal volume (TV) and transcutaneous carbon dioxide (TcCO2) levels.

RESULTS

Two patients showed a meaningful improvement in CHOP-INTEND scores (an increase of 4 points) after 2-3 years of nusinersen treatment. The remaining five showed changes ranging from 0 to 2 points. Subjective changes were observed in all patients. Patient respiratory function outcomes varied; TV increased in two patients and decreased in five, and TcCO2 levels decreased in three patients and increased in four.

CONCLUSIONS

Nusinersen may provide meaningful improvement in motor function in some patients with advanced SMA type 1; however, treatment response may take a while and varies between individuals. Further research is needed to substantiate these findings and identify potential prognostic factors for nusinersen treatment.

Changes in saccadic intrusions over time as an objective biomarker to follow ALS disease progression

Objective: Saccadic Intrusions (SIs) are abnormal eye movements during gaze fixation. Studies have indicated the clinical relevance of SIs, especially of square wave jerks (SWJ) in ALS. We used a software-based platform to extract SIs as a part of an interventional drug trial. The objective was to examine SIs' change over time as a potential biomarker of ALS disease progression. Methods: 28 ALS patients (61.95 ± 8.6 years) were assessed with the revised ALS Functional Rating Scale (ALSFRS-R) and with an oculometric test. Changes of SIs over time and correlations with ALSFRS-R and its bulbar subscale were calculated. A power calculation was conducted to understand the practical implications of results. Results: A significant increase of SWJ over trial duration was observed, with an increase in frequency (mean rise of 0.14 ± 0.28, p < 0.01), amplitude (0.001 ± 0.0016 degrees, p < 0.005), overall duration of SWJ (0.13 ± 0.25, in %, p < 0.01), and in their relative part out of all intrusions (0.18 ± 0.32, in %, p < 0.005). Negative correlations were found with the bulbar subscale (R=-0.43, -0.41, -0.39 and -0.47, respectively, p < 0.001). The required sample size for observing a 40% reduction in bulbar aspects when using the oculometric test (α = 0.05 and β = 0.8), was found to be 150 patients per arm, compared with 200 patients using the bulbar subscale. Conclusions: Evaluation of saccadic intrusions during fixation was able to detect disease progression over time, correlated with ALSFRS-R bulbar subscale. Eye movements can potentially serve as an objective biomarker in ALS clinical trials and reduce the required sample size to show clinical effect of therapies.

Cognition and communication in patients with spinal muscular atrophy: A systematic review

•Synthesizes evidence from 12 studies on cognitive and communicative impacts in SMA, focusing on nuanced functional outcomes.•Highlights cognitive variability in SMA1, revealing subtle challenges in SMA2 and 3, and stresses tailored assessment methodologies.•Identifies communication barriers in SMA, emphasizing the urgency of investigating their potential interplay with cognitive functions.•Stresses integrating cognitive and communicative assessments into SMA management, to enhanceunderstanding of treatment impacts.•Calls for standardized, sensitive tools to evaluate cognition and communication, ensuring consistent assessments across SMA phenotypes.

Nusinersen induces detectable changes in compound motor action potential response in spinal muscular atrophy type 1 patients with severe impairment of motor function

BACKGROUND

Most long-term affected spinal muscular atrophy (SMA) type 1 patients have severe impairment of motor function and are dependent on mechanical ventilation with tracheostomy. The efficacy and safety of nusinersen in these patients have not been established.

METHODS

We retrospectively evaluated the efficacy of intrathecal nusinersen treatment in patients with SMA type 1 who continued treatment for at least 12 months. There were three patients enrolled in our study (3, 4 and 16 years of age) who had severe impairment of gross motor function without head control or the ability to roll over. All three needed mechanical ventilation with tracheostomy and tube feeding. Motor function was assessed using the Children s Hospital of Philadelphia infant test of neuromuscular disorders (CHOP-INTEND) and the caregivers' evaluations. Concurrently, we examined nerve conduction longitudinally and compared compound motor action potential (CMAP) amplitudes.

RESULTS

All patients continued nusinersen administration without significant adverse events for more than three years. While CHOP-INTEND scores did not remarkably increase, according to the caregivers, all three patients had improved finger or facial muscle movements that enabled them to make their intentions understood. Some CMAPs before treatment were not identified but became traces after nusinersen administration.

CONCLUSIONS

The improvement in motor function that leads to smoother communication could be a basis for continuing nusinersen treatment. Currently available motor function scorings are not efficient for assessing therapeutic interventions in SMA patients with medical care complexity. Longitudinal nerve conduction studies could be an objective indicator.