FiO2 should be titrated to maintain arterial oxygen saturation of greater than 90%, bearing in mind that oxygen supply is often limited in high altitude clinics/environments.In addition to oxygen therapy, a portable hyperbaric chamber (Gamow bag) can by used as a temporary measure in the treatment of HACE. These devices simulate a decrease in altitude of up to 7000 ft, but they are resource intensive and symptoms will often return after discontinuation of the device. Portable hyperbaric chambers should not be used in place of descent or evacuation to definitive care.Diuretics may be helpful, but pose risks outside of a hospital environment. Sildenafil and tadalafil may help HACE, but there is little evidence of their efficacy. Theophylline is also theorized to help the condition.Although AMS is not life-threatening, HACE is usually fatal within 24 hours if untreated. Without treatment, the patient will enter a coma and then die. In some cases, patients have died within a few hours, and a few have survived for two days. Descriptions of fatal cases often involve climbers who continue ascending while experiencing the conditions symptoms. Prognosis
Recovery varies between days and weeks, but most recover in a few days. After the condition is successfully treated, it is possible for climbers to reascend. Dexamethesone should be discontinued, but continual acetazolamide is recommended. In one study, it took patients between one week and one month to display a normal CT scan following HACE.
Single Photon emission computed tomography (SPECT) may also be used which involves the use of a radiotracer that is taken up by the ictal region of the brain where,  typically the tumor lies. Positron Emission Tomography (PET-CT) using F-18 fluorodeoxyglucose (FDG) show reduced metabolism at the site of seizure onset. Gelastic seizures have been observed after taking a birth control pill (Maxim (R)). Optic nerve hypoplasia is the only reported condition with gelastic seizures without hypothalamic hamartomas, suggesting that hypothalamic disorganization alone can cause gelastic seizures. History
Very likely gelastic seizures were already recognized at the time of Babylonian medicine. A detailed description was given by the Scottish physician Robert Whytt in 1765, and the term "gelastic seizure" was coined in 1898 by the French neurologist, neuropathologist and epileptologist Charles Féré. Notable Cases
George William Helon (Australian author and businessman) is a Gelastic seizure patient, mentor, counsellor and advocate. Media references
Gelastic syncope was also referred to in one paper also as "Seinfeld syncope" after an incident in which a patient repeatedly fainted while watching an episode of Seinfeld. References
External links
Gelastic Seizures - Goran Brandberg, Orvar Eeg-Olofsson
Epilepsy Ontario - Gelastic seizures
Hypothalamic hamartomas and gelastic epilepsy
MR imaging of hypothalamic hamartoma