Oculomotor Dysfunction in Motor Neuron Disease

Though eye movements are relatively spared in motor neuron disease (MND), recent literature suggests patients may exhibit oculomotor dysfunction (OD). Frontal lobe involvement has been postulated based on oculomotor pathway anatomy and clinical overlap of amyotrophic lateral sclerosis (ALS) with frontotemporal dementia. We examined oculomotor characteristics in patients with MND presenting to an ALS Center, hypothesizing that patients with prominent upper motor neuron involvement or pseudobulbar affect (PBA) may demonstrate greater OD.

This was a single-center prospective observational study. Patients with diagnosis of MND were examined at bedside. Center for Neurologic Study-Liability Scale (CNS-LS) was administered to screen for pseudobulbar affect. Primary outcome was OD and the secondary outcome was the association between presence of OD in patients with MND experiencing symptoms of PBA or upper motor neuron dysfunction. Wilcoxon rank-sum scores and Fisher's exact tests were used to perform statistical analyses.

53 patients with MND underwent the clinical ophthalmic evaluation. On bedside examination, 34 patients (64.2%) presented with OD. There were no significant associations between locations of MND at presentation and the presence or type of OD. OD was associated with increased disease severity as measured by reduced FVC (p = 0.02). There was no significant association between OD and CNS-LS (p = 0.2).

Though our study did not find a significant association between OD and upper versus lower MND at presentation, OD may be useful as an additional clinical marker for advanced disease.