P64-S Reduced phosphene prevalence in ALS despite normal threshold

Abstract

Introduction Although ALS is one of the most common degenerative diseases of the motor neuron system, symptoms, and findings of the disease are not always restricted solely to the motor system. Certain clinical and electrophysiological findings observed in ALS patients imply some sensorial abnormalities. The aim of this study to investigate whether visual sensorial involvement occurs in ALS patients. For this, we investigated occipital cortex excitability with the phosphene threshold method. Method Twenty-one ALS patients and 16 healthy controls were included in the study. Visual cortex TMS was performed using a standard round coil. TMS was performed in a semi-dark room. Eyes of participants were closed with an eye mask. Coil was placed vertically to 7 cm above the inion. Right, and left occipital cortices were stimulated at the same session. Short interval intracortical inhibition (SICI) and resting motor threshold (RMT) were also studied as well as ALSFRS-R scores in patients. Results Phosphenes were elicited in 13 (81.2%) of controls, 9 (42.9%) of ALS patients (p = 0.041). Mean phosphene thresholds obtained with the occipital TMS was no difference between two groups (p > 0.05). No correlation was found between the phosphene threshold and ALSFRS-R scores, SICI, RMT (p > 0.05) Discussion Results of this study indicated a reduced prevalence of phosphene in connection with decreased occipital cortex excitability in ALS patients for the first time. This finding may indicate the loss of function of V1, V2/V3 or abnormal connectivity between V1 and V2/V3, regardless of clinical status or motor cortex excitability of the patients.