Neurophysiologic assessment of mucopolysaccharidosis III

Objective To describe finding of various neurophysiologic tests in patients with mucopolysaccharidosis III (MPS III) early in the disease course. Methods Patients were evaluated with flash visual evoked potentials (VEP), brainstem auditory evoked potentials (BAEP), electroencephalography (EEG), and nerve conduction studies (NCS) before they underwent hematopoietic stem cell transplantation (HSCT). Results Thirteen children underwent at least one neurophysiologic test before HSCT. The mean age at testing was 2.7 years. Ten of 11 (91%) patients had a normal flash VEP, and all 9 who had BAEP had normal central conduction. EEG was normal in 7/13 (54%), with the others showing diffuse slowing. NCS was normal in 10/11 (91%) patients. Conclusions Despite extensive central nervous system involvement in MPS III, flash VEP and BAEP are almost always normal. EEG is often abnormal early in the disease. Significance This is the first report of neurophysiologic tests in a large series of MPS III patients.