What to Know About Low-Pressure Headaches
Dr. Deborah Friedman, MD, MPH, FAHS, shares her insights on the connection between Spontaneous Intracranial Hypotension (SIH) and headache.
What is Spontaneous Intracranial Hypotension (SIH)?
In the simplest of terms, SIH is a low-pressure headache. Intracranial hypotension literally means that there is low spinal fluid pressure in the brain. In SIH, there is a leak of spinal fluid from the spine, either in the neck (cervical) or mid-back (thoracic) area. Spinal fluid bathes the brain, cushioning it from impact against the skull when the head moves. The brain makes spinal fluid continuously, and absorbs it at the same rate, creating a delicate balance that keeps the spinal fluid volume and pressure normal.
What are the Symptoms of SIH?
The most common symptom of SIH is a “typical” headache, located in the back of the head, often with neck pain. It is worse when standing or sitting and improves or goes away within 20-30 minutes of lying down, called “orthostatic” or “postural” headache. The pain is often very severe. The next most common variation is a headache that is not present (or mild) upon awakening but develops in the late morning or afternoon and worsens throughout the day.
The location of the headache varies – it may be in the front, affect the entire head or be one-sided. It may resemble migraine with sensitivity to light and noise, nausea or vomiting. There is no specific character of the pain, which may be aching, pounding, throbbing, stabbing, or pressure-like, as examples.
Another common feature of the headache is marked worsening with coughing, sneezing, straining (lifting, bearing down during a bowel movement), exercise, bending over and sexual activity. Other symptoms include hearing changes (muffled hearing, ringing in the ears, hearing loss), dizziness, impaired concentration, back or chest pain, and double vision. Rarely loss of consciousness, coma, or a Parkinson-like state may occur.
SIH is one cause of New Daily Persistent Headache, which is a headache that starts “out of the blue” one day and never goes away.
Who Gets SIH?
Although anyone can get SIH, it seems to occur more often in people who have a weak “connective tissue matrix”. These people are often tall and thin, have a slender neck, are double-jointed or unusually flexible. Their dura is probably thinner and prone to tearing than in most people.
How is SIH Diagnosed?
If you think that have the symptoms of SIH, it’s important to consult your doctor to conduct a series of tests. From the Trendelenburg test, where the patient lies flat and the exam is tilted to lower the head, imaging studies such as an MRI scan, CT scan or cisternogram, can help to determine if SIH is the cause of the headaches. Still, even through diagnostic testing, a substantial minority of patients may have normal results.
How is SIH Treated?
Many patients with long-standing SIH discover that virtually all of the standard medications used for headache treatment are ineffective. The medical management is similar to what is used for the headache that occurs immediately after a spinal tap, including caffeine, hydration and lying flat. Sometimes an abdominal binder or a medication called theophylline (which acts similar to caffeine) are helpful but rarely make the headache go away permanently.
Because epidural blood patches are usually successful, they are often the first line of treatment. The patient’s own blood is drawn from the arm and injected in the low spine into the epidural space, which is the space immediately outside the dura. The procedure is performed under fluoroscopy (x-ray) or CT as an outpatient. The most common complication is lower back pain that generally resolves within a week. Occasionally, the back pain lasts weeks or months; rarely there may be scarring (arachnoiditis) causing persistent back pain, or a rebound high pressure state which usually resolves on its own. There is a potential risk of infection. The blood patch often brings instant relief. Sometimes the effect wears off and additional blood patches are needed.
Why Not Just Fix the Leak?
It sounds easy but the site of the leak may be VERY difficult to find. The tests that are most helpful to locate the leak are special MRI images (which are not part of the standard MRI software package and not readily available), as well as MR and CT myelography. Even with these techniques, there may be “false positive” results that are misleading because the abnormality on the image is not really the site of the leak. The most difficult leaks to find and treat are in front of the spinal cord. Directed blood patches and surgery may ultimately be needed.
Deborah I. Friedman, MD, MPH, FAHS
Director, Headache and Facial Pain Program
Professor of Neurology and Neurotherapeutics and Ophthalmology