Noninvasive C-13-octanoic acid breath test shows delayed gastric emptying in patients with amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disorder c haracterized by progressive loss of motor neurons. However, ALS has been re cognized to also involve non-motor systems. Subclinical involvement of the autonomic system in ALS has been described. The recently developed C-13-oct anoic acid breath test allows the noninvasive measurement of gastric emptyi ng. With this new technique we investigated 18 patients with ALS and 14 hea lthy volunteers. None of the patients had diabetes mellitus or other disord ers known to cause autonomic dysfunction. The participants received a solid standard test meal labeled with C-13-octanoic acid. Breath samples were ta ken at 15-min intervals for 5 h and were analyzed for (CO2)-C-13 by isotope selective nondispersive infrared spectrometry. Gastric emptying peak time (t(peak)) and emptying half time (t(1/2)) were determined. All healthy volu nteers displayed normal gastric emptying with a mean emptying t(1/2) of 138 +/- 34 (range 68-172) min. Gastric emptying was delayed (t(1/2) > 160 min) in 15 of 18 patients with ALS. Emptying t(1/2) in ALS patients was 218 +/- 48 (range 126-278) min (p < 0.001). These results are compatible with auto nomic involvement in patients with ALS, causing delayed gastric emptying of solids and encouraging the theory that ALS is a multisystem disease rather than a disease of the motor neurons only.