Argentina’s President, Cristina Kirchner, is to undergo surgery on Tuesday to drain a brain hematoma, officials said, leaving her party in uncertainty in the run-up to this month’s congressional elections.

Kirchner’s spokesman revealed on Saturday that she had been diagnosed with a brain injury following an August 12 fall. Doctors treating her had initially prescribed 30 days rest.

But a decision to operate was taken after Kirchner complained of tingling and a temporary loss of muscle strength in her left arm late Sunday, the Fundacion Favaloro hospital announced.

“A surgical procedure to drain the hematoma has been scheduled,” the hospital confirmed on Monday. Kirchner was hospitalized on Monday ahead of the operation.

“It does not seem serious,” surgeon Carlos Schwartz said adding that “any act of neurosurgery contains risks; but it’s a simple procedure.”

News of Kirchner’s ailment caught Argentina by surprise.

The 60-year-old showed no hint of ill-health in the weeks following the fall as she maintained a busy schedule and undertook trips to Paraguay, Russia and the United Nations General Assembly meeting.

Kirchner, first elected in 2007 before being re-elected for a final four-year term in 2011, spent Sunday resting at her official residence with her son and close advisors.

Vice President Amadou Boudou will act as interim leader in Kirchner’s absence, but has not officially assumed the presidency.

Boudou has filled in once before, running the country for 20 days in January 2012 when the president underwent an operation to remove a growth on her thyroid which was wrongly diagnosed as cancerous.