"Stress itself is not a universal risk factor for seizures," said lead author Dr. Ichiyo Shibahara, a staff neurosurgeon at Sendai Medical Center in Japan. "Most of the seizure patients had some sort of neurological disease before the earthquake."

The report, published in Epilepsia, looked at 440 patient records from Kesennuma City Hospital and found that 13 patients were admitted with seizures in the eight weeks after the earthquake and tsunami - and only one had been admitted in the eight weeks prior to the disaster.

That's nearly twice the average of 7.3 seizure patients admitted during the same 16-week period in the three previous years.

Five of the 13 seizure patients in 2011 were admitted to the hospital just in the first week following the earthquake and tidal wave.

The tsunami flooded a third of Kesennuma, a city of 73,000 residents, but the hospital remained operational in the aftermath.

Previous research has linked stressful life-threatening disasters with an increased risk of seizures, but most case reports lacked clinical data with multiple patients, Shibahara told Reuters Health.

So his team examined medical records from patients admitted to the neurosurgery ward in the eight weeks before and after the March 11, 2011 tsunami, and compared them to the same time period each year between 2008 and 2010.

In 2008, there were a total of 11 seizure patients admitted between January 14 and May 15. In 2009, there were seven and in 2010, just four.

Of the 13 seizure patients admitted after the disaster, 11 had preexisting brain disorders that included epilepsy, head injuries or stroke. All the patients lived independently, and eight took anti-convulsion medications.

Shibahara noted that of the five seizure patients admitted days after the tsunami, it was "not because of a lack of anticonvulsants, but because of the stress."

One later seizure patient was unable to refill his anti-epilepsy medication weeks after the devastation, however.

Kesennuma City Hospital neurosurgeons typically treat patients with stroke, head trauma and brain tumors, but the researchers found no increases in patients with those conditions in the weeks after the earthquake and tsunami.

"This is interesting, but I'm not 100 percent convinced," said Dr. William Theodore, senior investigator of the clinical epilepsy section at the National Institute of Neurological Disorders and Stroke in Bethesda, Maryland.

Theodore, who was not involved in the current study, told Reuters Health that because the number of patients was so small, random variation could explain the apparent surge in seizures in 2011.

Or, instead of stress, upset patients may have forgotten to take, or weren't able to find, anti-epileptic drugs, Theodore said.

There are also various ways that natural disasters might cause seizures, according to Theodore, including head trauma, infections from polluted water or a lack of sleep.

Other researchers have shown how earthquake and tsunami-stricken residents suffered increased heart failure and workers at the crippled Fukushima Daiichi nuclear power plant suffered psychological distress. (See Reuters Health stories of September 27, 2012 reut.rs/VOVZLC and August 14, 2012 reut.rs/Ni8KtJ).

The current study highlights the necessity of local treatment and information networks for seizure-prone residents, said Dr. Sunao Kaneko, neuropsychiatry professor at the Hirosaki University Graduate School of Medicine and president of the Japan Epilepsy Society, who was not involved in the research.

After the 2011 disaster, Japan started to develop a nationwide epilepsy treatment network that includes a thousand doctors along with information and rescue centers for epilepsy patients.

"The establishment of local epilepsy centers where patients with epilepsy can easily access clinics is crucial," Kaneko wrote to Reuters Health in an email.

Whether a natural disaster takes the form of an earthquake, tsunami, blizzard or Superstorm Sandy, Theodore noted, the study has a practical take home message.

"If you already have seizures and you're taking medication, always make sure you have a decent supply just in case some natural disaster occurs," Theodore said.

SOURCE: bit.ly/V6aiPN Epilepsia, online January 7, 2013.

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