Risus Sardonicus

What is risus sardonicus?

Risus sardonicus (rye-sus sar-dan-uh-kes) is when the muscles in your face tighten, forcing a big, open-mouth smile and raised eyebrows. Some people describe it as a sneer. It’s a type of painful, involuntary muscle spasm.

But it isn’t like spasms that occur in other parts of your body. Those can occur due to dehydration, overuse or sitting too much. Instead, risus sardonicus usually happens from a certain type of bacterial infection. It can also result from particular genetic conditions and exposure to certain poisons.

“Risus” is Latin for “laugh.” “Sardonicus” comes from the Greek word “sardónios,” which means a bitter or scornful laugh or smile. Other names for risus sardonicus include:

• Rictus grimace
• Rictus grin
• Tetanus smile

What causes risus sardonicus?

The most common cause of risus sardonicus is tetanus. Tetanus is a bacterial infection. It causes muscle spasms, especially in your head, neck and face.

Other possible risus sardonicus causes include:

• Strychnine poisoning: Strychnine is a bitter, odorless, white powder. It’s mostly used in rat poisons. In rare cases, cocaine, heroin and LSD (acid) may contain strychnine. It affects the nerve signals in your muscles and causes severe spasms.
• Wilson disease: This is a rare condition that some people have at birth. It causes copper to build up in your body, especially in your brain and liver. Not everyone who has Wilson disease experiences the same symptoms. But some experience muscle stiffness, including risus sardonicus.

How is it treated?

Risus sardonicus treatment depends on the cause.

Tetanus treatment generally includes medications, such as:

• Antibiotics like metronidazole and penicillin G
• Tetanus antitoxin (human tetanus immunoglobulin)
• Tetanus shot (tetanus toxoid)

Healthcare providers may recommend muscle relaxers to help reduce spasms. You may also need benzodiazepines (benzos) to slow down your nervous system.

If you have strychnine poisoning, it’s important to get it out of your system as quickly as possible. Treatment usually includes:

• Antiseizure medications and antispasmodics to treat muscle spasms or shaking
• IV fluids to help flush out strychnine
• Lowering a high body temperature

If Wilson disease causes risus sardonicus, providers may recommend botulinum toxin (Botox®) injections. They’ll inject Botox around your mouth and eyebrows.

What are the possible complications or risks of not treating it?

The causes of risus sardonicus are life-threatening without treatment. Get help as soon as possible if your face locks into a big smile and raised eyebrows.

Can risus sardonicus be prevented?

You can’t prevent all risus sardonicus causes, like Wilson disease. But you can avoid other causes by:

• Avoiding acid, cocaine and heroin
• Getting a tetanus vaccine
• Using the proper PPE and washing your hands when handling rat poisons

When should this symptom be treated by a doctor?

Call 911 (or your local emergency service number) or get to the nearest ER immediately if you have painful facial muscle spasms. Healthcare providers can help diagnose and treat the cause of risus sardonicus.

What is the difference between trismus and risus sardonicus?

Trismus is also a type of facial muscle spasm. But unlike risus sardonicus, trismus prevents you from opening up your mouth as wide as usual. Tetanus and other infections can cause trismus. But the main causes are head and neck cancer treatments and dental surgery.