Scanning electron microscopy (SEM) of two fractions of cerebrospinal fluid (CSF) from our patient with amyotrophic lateral sclerosis (ALS) and a control subject. Cerebrospinal fluid was dripped onto the surface of a polycarbonate filter with 0.6μm pores (visible in the images and can be used for size reference). A total of 100μL of cerebrospinal fluid was used from our patient, and 200μL from the healthy control subject. Although only half the volume of control cerebrospinal fluid was used for our patient, the amyotrophic lateral sclerosis filters are filled with compact aggregates of spherical particles of lipid appearance, sticking together in a viscous batter. This process can be clearly seen in the image from our patient’s sample in the upper left corner (CSF I × 500) where the subcellular structures are closely attached, leaving the remaining filter free of aggregates. Control filters (CSF I × 2000) and (CSF II × 2000) are free of particles except a tiny skin flake in the middle of the control filter (CSF II × 2000).