A headache. A runny nose. Neck pain. Everybody gets them now and then. Most of the time they don't indicate a serious disease, and they pass quickly on their own. But what if they don't? How do you know when that headache is a sign of a rare but debilitating disorder known as a cerebrospinal fluid (CSF) leak? 

Here are answers to five key questions about this painful and sometimes dangerous condition—from telltale symptoms, when to see a doctor and what to expect if you need treatment.

Read: Know Your Headaches

A CSF leak happens when there's a small tear in the dura—the lining of the spinal cord and brain. When the fluid leaks out, the volume and pressure of fluid in your skull drops, leading your brain to slump.

"This 'brain sag' can trigger severe, relentless headaches, and can also cause vision and hearing disturbances, seizures and other symptoms such as neck pain and a heightened sense of smell," explains Wouter I. Schievink, MD, director of Microvascular Neurosurgery and the Cerebrospinal Fluid (CSF) Leak Program at Cedars-Sinai. "In other cases, cerebrospinal fluid can start draining from the nose, which is why many patients think they have a cold or allergy," he adds.

A leak that occurs at the cranial level, rather than the spine, doesn't result in the same drop in volume and pressure of fluid in the skull. A cranial CSF leak results in a runny nose and carries a high risk of meningitis, an inflammation of the membrane around the brain and spinal cord, which can be fatal and requires emergency attention.

Read: An Uncommon Cold: Runny Nose and Headaches Signaled Rare Disease

Spontaneous CSF leaks (ones that are not triggered by a medical procedure such as a lumbar puncture, or by a serious injury such as a gunshot wound) occur in at least five in 100,000 people per year, making them fairly rare. 

"Because doctors and patients alike aren't used to seeing them, spontaneous CSF leaks are underdiagnosed," says Dr. Schievink, who is one of the world's foremost authorities on the condition.

Patients can suffer a long time without knowing what's wrong, and they may make repeated trips to the hospital or doctor's office without getting clear answers or relief. Prompt medical attention can reduce a patient's suffering much sooner, spare them from disability and even save their life. 

"The longer the diagnosis is delayed, the higher the risk of the leak continuing and having lasting effects," says Dr. Schievink, who has successfully treated many patients who had lost hope after being told by other doctors that they didn't know what was wrong or how to help.

Read: Back on Her Feet Thanks to CSF Leak Repair

For every aspect of your health, it's important to pay attention to symptoms that are unusual for you. A CSF leak is an example of what can happen if you're not listening to your body. 

"Headaches caused by CSF leaks don't feel like ordinary headaches. They're typically more severe," says Dr. Schievink. If your head hurts and the pain just isn't going away, don't ignore it. 

One key characteristic of a CSF leak is that symptoms get much worse when you're sitting or standing, while lying down often brings relief. A combination of symptoms is also noteworthy. You may sometimes get bad headaches, neck pain or a clogged feeling in the ears, but having all at once for a prolonged period of time merits attention—not least if accompanied by changes in your hearing, vision or other senses. 

Read: CSF Leak Patient Brianna Won't Wait for a Cure to Be Happy

Risk factors include having a connective tissue disorder such as Ehlers-Danlos syndrome, but a spontaneous CSF leak can happen to anyone—and in many cases the reason is simply unknown. The average age for a leak developing spontaneously is 42, but it can occur at any age, including among children. Women are about twice as likely as men to develop the condition.

"Patients are often shocked to get the diagnosis," says Dr. Schievink, "but they are also relieved because they finally know what's wrong." 

Better yet, Dr. Schievink can often share good news: In some cases, a CSF leak will heal with basic treatment, including strict bed rest, increased fluid intake and caffeine. 

When that's not enough, one successful approach is to use blood patches—a surgical procedure that uses the patient's blood to patch the leak. In more difficult cases, a surgical sealant known as fibrin glue can be used to good effect, as can neurosurgery. Relief can be quick and dramatic, and any continued discomfort is often more tolerable. 

"If you suspect you may be suffering from a CSF leak, don't delay and don't despair," says Dr. Schievink. "There is help here for you."