Seizures at high altitude in a patient on antiseizure medications

To the Editor: Seizures are a common neurological phenomenon. Whether the high altitude environment triggers a seizure is a commonly asked question.1.Basnyat B. Cumbo T. Edelman R. Acute medical problems in the Himalayas outside the setting of altitude sickness.High Altitude Med Biol. 2000; 1Crossref PubMed Scopus (46) Google Scholar A case is reported here of an epileptic patient who had seizures at a high altitude despite being on phenytoin for a number of seizure-free years. A 46-year-old male trekker to the Himalayas presented with shortness of breath at the Pheriche clinic (4300 m) on the way to Mount Everest. After a conservative ascent profile to around 4000 m, he gradually felt very tired and short of breath. Prior to this, he had a persistent cough for a day or two. He neither smoked nor drank alcohol on the trek. On examination at the aid post at 4300 m, he was oriented but appeared very tired. His pulse rate was 100 beats/min and his blood pressure was 140/70 mm Hg. His respiratory rate was 30/min. He had bilateral, obvious crackles in his lungs and his oxygen saturation was 80%. His heart sounds were normal but difficult to hear because of the crackles. He was given 3 L of oxygen per minute and subsequently put in the hyperbaric bag, where he made a tremendous improvement after an hour. His respiratory rate decreased to 20/min, his oxygen saturation level rose to 86% and he felt much better. He had to be put in the bag again after a couple of hours as his respiratory rate again increased to 30/min, the saturation dropped to 79%, and he felt uncomfortable. He improved and the next morning gradually walked down to around 3800 m with assistance. The day after that he felt much better and descended to Namche Bazaar at about 3400 m. He was on no other medicines besides phenytoin. He continued to cough, but felt much better. At the same altitude the next morning, he had a grand mal seizure that lasted for about 30 seconds and was observed by his wife, who had seen his previous seizure 4 years earlier. He returned to full consciousness after 15 minutes, but he had another generalized seizure 2 hours later. He then took 5 mg of diazepam, which he had brought with him. He became seizure free and walked to Lukla in 2 days and then flew out to Kathmandu. He was on 400 mg of phenytoin and 5 mg of diazepam twice daily. He had no more seizures after that, and flew back home to the United States. His past history revealed that he had had epilepsy for 15 years. His last seizure was 4 years prior to his Himalayan trip when he had missed medications for days. He took phenytoin conscientiously. Computerized axial tomography of his head taken 1 year earlier was normal. Eight days prior to the seizure, he had developed diarrhea and had taken ciprofloxacin for 2 days. In the United States he said he regularly trekked up to around 4000 m, but did not sleep at that altitude. He was lost to follow-up. There are reported cases of seizures at high altitudes,2.Basnyat B. Seizure and hemiparesis at high altitude outside the setting of acute mountain sickness.Wilderness Environ Med. 1997; 8: 221-222Abstract Full Text PDF PubMed Scopus (14) Google Scholar,3.Basnyat B. Fatal grand mal seizure in a Dutch trekker.J Travel Med. 1998; 5: 221-222Crossref PubMed Scopus (8) Google Scholar but the author is unaware of other literature about a sojourner at high altitude who had seizures despite being well controlled on antiseizure medications. His initial presentation was of high altitude pulmonary edema (HAPE). It is possible that he might have had some high altitude cerebral edema (HACE),4.Hackett P.H. Roach R.C. High altitude medicine.in: Auerbach P.A. Wilderness Medicine. Mosby, St. Louis, MO1995: 1-37Google Scholar as well, that triggered the seizures, although a seizure is not a hallmark presentation of HACE.4.Hackett P.H. Roach R.C. High altitude medicine.in: Auerbach P.A. Wilderness Medicine. Mosby, St. Louis, MO1995: 1-37Google Scholar The other possible trigger for seizures might be the hypocapnia brought on by the hyperventilation in a seizure-prone individual.5.Hackett P.H. Medical problems of high altitude.in: Du Pont H.L. Steffen R. Textbook of travel medicine and health. BC Decker Inc, Hamilton, Ontario1997: 51-62Google Scholar Hypoxia itself could be a trigger for seizures. Lastly, this patient took ciprofloxacin for gastroenteritis that could have lowered his seizure threshold and precipitated the seizure.3.Basnyat B. Fatal grand mal seizure in a Dutch trekker.J Travel Med. 1998; 5: 221-222Crossref PubMed Scopus (8) Google Scholar He could also have had a space-occupying lesion (no investigations were done in Kathmandu) that manifested for the first time at high altitude6.Shlim D.R. Meijer H.J. Suddenly symptomatic brain tumors at altitude.Ann Emerg Med. 1991; 20: 315-316Abstract Full Text PDF PubMed Scopus (29) Google Scholar and presented with a seizure. The important point is that this man had a breakthrough seizure at high altitude despite being well controlled on phenytoin. Many people on antiseizure medications continue to safely trek up to high altitude; certainly this single case report is not an attempt to change that trend. But with the burgeoning trekking in the mountains, close monitoring and documentation of these trekkers, especially in the event of a seizure, will be helpful for both the seizure-prone trekker and the wilderness medicine health care provider alike.

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