A small tumor-like mass known as a hypothalamic hamartoma can cause patients to feel the desire to laugh, according to a case report in the February 22 issue of Neurology, the scientific journal of the American Academy of Neurology. The urge to laugh is not always followed by laughter. The report tells of three patients with small non-cancerous hamartomas located on the brain's hypothalamus, causing mild epileptic seizures and the unusual pressure-to-laugh feeling. The patients had recurring giggling bouts at a young age that remained into adulthood. Medication was able to stop the seizures, but did not stop the urge to laugh. The suppressed laughing bouts could occur up to 10 or 15 times a day for patients, causing some embarrassing situations. One woman described the feeling "like a tickling inside my head." Due to a rise in her voice occurring with the urge to laugh, she gave up singing. Another man gauged the surrounding social situation to judge whether laughter was appropriate or not. He would bite his lip to suppress his laughter or let the urge develop into laughter similar to his normal laugh. His normal laughter caused tearing and reddening of the face whereas the pressure-to-laugh occurrences did not.
"Many patients find the feeling pleasant," said neurologist and case report author Samuel Berkovic, MD, from the Austin and Repatriation Medical Center in Victoria, Australia. "However, they are aware that sometimes a seizure may follow and this is frightening. It results in patients torn between the enjoyment of the symptom and the fear of what could happen after it."
Berkovic says it's important to recognize this often undetected symptom as a clue to the presence of a hamartoma and seek treatment from a neurologist.
"How laughter occurs is not completely understood," said Berkovic. "Laughter involves a complex relationship between the thought processes and emotional aspects of the brain as well as the physical control of the muscles in the chest and voice box. We know the hypothalamus, a tiny structure deep in the brain that is involved in things like thirst, temperature control and appetite along with emotions, is very important to the generation of laughter."
These three patients had normal brain development and intelligence, unlike other cases involving hypothalamic hamartomas and laughing seizures, where problems with mental ability, multiple seizures and behavioral problems developed.
"The difference in the symptoms of these three patients and more severe hamartoma cases is the smaller size of the hamartomas," said Berkovic. "Our patients are on the mild end of the spectrum."
