What is Spontaneous Intracranial Hypotension?
The pressure inside your skull, known as intracranial pressure, is regulated by the creation, movement, and absorption of a fluid known as cerebrospinal fluid (CSF). If there’s a change in these activities which in turn affects the CSF pressure, it can lead to symptoms affecting the nervous system. The most common symptom is a headache. A condition known as spontaneous intracranial hypotension (SIH) is characterized by a headache that worsens upon standing or sitting up and low levels of CSF. This usually happens due to a CSF leak.
In most cases, a type of brain scan called magnetic resonance imaging (MRI) will show a general increase of fluid around the membranes that cover the brain. However, there have been a few instances where patients experienced a constant headache (not affected by changes in posture), their CSF pressure was normal, and there was no involvement of the brain’s membranes on their MRI. Over time, this condition has been called by various names, such as an unexplained headache due to low CSF pressure, liquorrhea, headache due to low CSF volume, CSF hypovolemia, headache due to CSF volume depletion, hypoliquorrhoeic headache, and headache due to a CSF leak.
What Causes Spontaneous Intracranial Hypotension?
A leak in the cerebrospinal fluid (CSF), the clear liquid that cushions and delivers nutrients to your brain and spinal cord, can occur naturally (congenital) or be due to some sort of trauma that causes defects in the dura, the protective layer around your brain and spinal cord. These defects usually come in the form of small openings or tears resulting in CSF leaks.
Spontaneous intracranial hypotension, a medical condition where there is low fluid pressure in the brain, is typically due to a decrease in the volume of CSF, rather than a drop in CSF pressure as was previously believed.
There are several different factors that could lead to CSF leakage. These include, for example, a missing dura layer around the spaces where the nerves leave the spinal cord (nerve root sheaths), inherited disorders that affect your connective tissues causing structural abnormalities, bony outgrowths on your spine (osteophytes), or where a spinal disc slips out of place (herniation).
Areas of the dura that are weak, particularly around the middle and lower part of your spine, are especially prone to CSF leaks. These weakened areas create sac-like outpouchings known as arachnoid diverticula.
Apart from these, CSF can also leak due to trauma, surgery, or when too much fluid is drained by a CSF shunt, a device used to reduce pressure in your brain caused by the excess fluid. Consequently, these scenarios could lead to spontaneous intracranial hypotension.
Risk Factors and Frequency for Spontaneous Intracranial Hypotension
Spontaneous intracranial hypotension, or SIH, is a condition that affects around 5 in 100,000 people. It’s more often found in females, with twice as many women as men getting it. Most commonly, it affects people around 40 years old, but it can still occur in both children and older adults.
- SIH affects about 5 in every 100,000 people.
- There are twice as many female cases as there are male cases.
- People around the age of 40 are the most likely to get SIH.
- Both children and older adults can also get SIH.
Signs and Symptoms of Spontaneous Intracranial Hypotension
Spontaneous intracranial hypotension is a condition often recognized by its main symptom – postural headaches. Though, it can also cause other neurological symptoms such as:
- Nausea
- Neck pain
- Vomiting
- Neck stiffness
- Loss of appetite
- Excessive sweating
- Double vision
- Sensitivity to light
- Hiccups
- Unsteady walk
- Heightened sense of hearing
- Ringings in ears
- Blurred vision
- Distorted or bad taste in the mouth
The associated headache can come on suddenly or gradually, can be felt all over the head or only in one spot, and may be throbbing or dull. It can range from mild to severe, to the point of incapacity. Thankfully, laying down usually provides relief within minutes. However, in cases with uneven leaking of brain spinal fluid, relief might only come from lying on a certain side. Additionally, activities such as sneezing, coughing, standing, moving the head, and being at high altitude can make the headache worse.
Testing for Spontaneous Intracranial Hypotension
When a doctor suspects a condition called spontaneous intracranial hypotension, several tests and scans are usually ordered. This condition causes a decrease in the amount of cerebrospinal fluid (CSF) – the fluid that cushions your brain and spinal cord. Symptoms include a headache that gets worse when standing and improves when lying down.
Firstly, an MRI of the brain and spine is typically recommended. This imaging test can provide detailed pictures of these areas and help the doctor spot any issues. Measuring the pressure of the CSF can give further clues about the condition. If there’s been a recent trauma or surgery, and you develop a specific type of headache afterwards, this could also suggest spontaneous intracranial hypotension.
During a brain MRI, the doctors will use a contrast dye to help see some areas more clearly. A typical sign of this condition is something called “pachymeningeal enhancement,” which essentially means that the lining of the brain shows more clearly on the scan. Other things a doctor might note on the MRI are swelling of the brain’s blood vessels, a decrease in the size of the brain’s ventricles (fluid-filled structures), and a sinking of the brainstem – to name a few.
In one study of 165 people with this condition, brain MRIs, CT scans, and another type of MRI called an MR myelography were used to find the exact location of the CSF leaks in patients. In most cases, the leakage was seen in the top part of the spine or neck area.
Spinal MRIs can also play an important role in diagnosing and managing this condition. They can help in spotting the exact site where the CSF is leaking. They might also reveal an enlargement of the spinal venous plexus (a network of veins in the spinal canal), or a decrease in the size of the dural sac (a covering that protects the spinal cord and contains the CSF).
Finally, in order to officially diagnose someone with spontaneous intracranial hypotension, doctors refer to the International Classification of Headache Disorders. It requires the following:
1) A specific type of headache that is triggered or worsened by a certain body position.
2) Low CSF pressure.
3) A link between the headache and CSF leakage or low CSF pressure.
4) Ruling out any other conditions that might be causing these issues.
Treatment Options for Spontaneous Intracranial Hypotension
Spontaneous intracranial hypotension, or sudden low pressure or volume of cerebrospinal fluid (CSF) in the brain, can cause headaches and other symptoms. The right treatment depends on how severe the condition is. For mild to moderate cases, doctors usually recommend conservative treatment. This involves resting in bed, drinking caffeine, not sitting upright, and taking painkillers. Doctors may also recommend high salt intake and taking hydrating fluids orally or through a drip (IV hydration) to increase the volume of the CSF, which can help ease symptoms.
If the symptoms are still there after 1 to 2 weeks of this treatment, or if it’s a bad headache, or if it’s related to a connective tissue disorder or a severe injury, then doctors might consider an epidural blood patch (EBP). This is a procedure where the doctor injects some of the patient’s blood into the epidural space in the spine. It is thought to be effective because it can plug up the CSF leak, relieving symptoms quickly. Meanwhile, in the long run, the procedure can stimulate the formation of fibrin (a protein that helps blood clot) and scar tissue around the leak, which provides a long-term solution.
If this EBP method still doesn’t work after several tries, healthcare professionals might use epidural fibrin glue or even perform surgery to treat the CSF leak. Epidural fibrin glue can prove successful in about one third of patients who did not respond to EBP. This strategy, along with surgery, requires the healthcare professional to locate the exact spot where the CSF is leaking.
When less invasive therapies fail, surgical treatment may be necessary. To locate the CSF leak, a medical imaging technique such as CT or MR myelography can be used. The healthcare professional would then seal the leak either with stitches or metal clips. In addition to stitches, they might use fibrin glue, a muscle plug, or a special sponge-like substance called gel foam to manage any tears or lesions in the dura (this is the outermost layer that surrounds the brain and spinal cord).
If the EBP treatment doesn’t work and the leak can’t be found, healthcare professionals might try a continuous epidural infusion of dextran or saline. This helps to increase the CSF volume, which can help relieve symptoms.
What else can Spontaneous Intracranial Hypotension be?
Spontaneous intracranial hypotension, or a sudden decrease in brain fluid pressure, can sometimes be confused with other medical conditions that show similar symptoms. For example, postural tachycardia syndrome, a condition that affects blood flow, can also cause orthostatic headaches, or headaches that occur when standing up. However, this syndrome does not involve a leak of cerebrospinal fluid (CSF), which is a key feature of spontaneous intracranial hypotension.
Another condition that might appear like spontaneous intracranial hypotension involves too much drainage from CSF shunts, small devices sometimes used in brain surgeries to divert excess fluid away from the brain. But again, this does not necessarily involve a leak of CSF.
It’s important to note that just because there are orthostatic headaches and no apparent CSF leak, it doesn’t confirm that the person has spontaneous intracranial hypotension. One case reported a patient with such symptoms, but an MRI scan revealed a lumbar intradural mass. This mass was later removed and identified as a myxopapillary ependymoma, a type of tumor typically found in the lower part of the spinal cord.
What to expect with Spontaneous Intracranial Hypotension
In a few instances, people have experienced improvement from spontaneous intracranial hypotension, a condition where the fluid in the brain drops, within two weeks. However, some people may still face symptoms even after the problem with the fluid leakage has been fixed.
There are also instances where this condition persists for months, and in rare situations, it can even last for years. If the leaks of brain fluid are ongoing, but happen with big intervals of weeks or months, they can result in occasional headaches with no symptoms in the time gaps in-between.
About 10 percent of affected patients may again experience fluid leakage from the brain, despite having received proper treatment.
Possible Complications When Diagnosed with Spontaneous Intracranial Hypotension
During the EBP procedure, a person’s own blood, usually between 10 to 20 cc, is infused into the area surrounding the spinal cord, known as the epidural space. If initial treatment doesn’t work, the volume can increase, anywhere from 20 to 100 cc. However, doing this may cause back pain or radiculopathy, a nerve condition that causes pain, weakness, or loss of sensation in the arms or legs. You could also experience other side effects such as fever and leg tingling or numbness.
In rare cases, spontaneous intracranial hypotension – a condition where the fluid pressure inside the skull is lower than normal – can cause a person to fall into a coma. This happens when the brain sags due to the lowered pressure. The way to help a person in this condition regain consciousness is to close the cerebrospinal fluid (CSF) leak causing the problem.
Side Effects of EBP:
- Experiencing back pain or radiculopathy
- Fever
- Leg tingling or numbness
Potential Serious Complications:
- Coma due to spontaneous intracranial hypotension
Preventing Spontaneous Intracranial Hypotension
It’s important for patients to understand their medical condition. Before proceeding with a medical procedure called a lumbar puncture, the patient should be informed about potential risks, including a possible condition called spontaneous intracranial hypotension, which is when the pressure inside the skull becomes too low. Successful management of the condition will largely depend on how well the patient understands the disease.
To aid in their understanding, patients can be given educational materials or recommended online resources about the disease. By understanding their condition better, patients are more likely to comply with the advice and instructions given by their healthcare providers, which can assist in improving their health outcomes.
