The inability to laugh audibly is an exceedingly rare neurologic symptom. The authoritative textbooks of Lewandowsky, Oppenheim and Gowers make no mention of it, although Kinnier Wilson said that neurologists have occasion "every now and then" to see patients with this symptom. So far as I can determine, but two cases have been recorded in the literature.
Weisenburg,1 in 1909, reported a case in a woman, aged 32, who had shown a moderate degree of morbid somnolence since the age of 16. Neurologic examination gave negative results. Treatment, consisting of static electricity, "suggestive therapy" and alterations in the daily routine, was followed by considerable improvement. Weisenburg made the following comment with regard to the laughing function: "A rather interesting feature of her disorder has been that for many years she has never been able to laugh audibly. She is usually of a cheerful, optimistic disposition, and while she would
Levin M. INABILITY TO LAUGH AUDIBLY: APHONOGELIA. Arch NeurPsych. 1931;25(1):157-159. doi:10.1001/archneurpsyc.1931.02230010169012