Avid rock climber suddenly could not get up from squats

Medical Mysteries Medical Mysteries is a series that spotlights rare diseases or unusual conditions.

- Judith Tan

In 2021, Ms Siti Nur Sabrina Anis, 26, had to swop one set of wheels for another — her Yamaha motorcycle for a motorised wheelchair.

"I used to enjoy riding my motorcycle. It was a great way to de-stress," said the secretary of the Motor Neurone Disease Association Singapore (MNDaSG), a charitable organisation.

She was 22 when she was diagnosed with amyotrophic lateral sclerosis (ALS), also known as Lou Gehrig's disease.

ALS is a rare, terminal neurodegenerative disorder that affects nerve cells in the brain and spinal cord, which control voluntary movements and muscle function.

The disease causes these nerve cells to atrophy over time, and a patient may lose the ability to speak, eat, move and breathe. There is currently no cure for ALS.

It all began when Ms Sabrina had trouble lifting the front part of each foot. This is known as foot drop, which is often due to the compression of a nerve.

"It was at the end of 2021 when I sprained my ankle, and I thought my gait was off because of that.

"However, all the doctors, all the physicians I consulted simply recommended rehabilitation or physiotherapy. They did not really think much about it," she said.

Soon, more than just her gait was affected. The avid sports enthusiast, who enjoyed trekking and rock climbing, suddenly could not jump or get up from squats.

This unexpected onset of muscle weakness confused her.

At that time, Ms Sabrina was graduating from the National University of Singapore with an honours degree in philosophy. She did not want to start working "without figuring out what was wrong".

"I persisted until I found a polyclinic doctor who referred me to a hospital. It took quite a while — around nine months — to finally get answers," she said.