Perineural cysts, which are
also known as Tarlov cysts, are
fluid-filled sacs that form on nerves at the base of the spine. A person with
such cysts would likely never know it. They almost never cause symptoms. When
they do cause symptoms, however, the most common is pain in the lower back,
buttocks, and legs. This occurs in rare cases when the cysts become enlarged
with spinal fluid and press on nerves.
Because they rarely cause
symptoms, perineural cysts are not often diagnosed. A doctor can determine if a
patient has the cysts using imaging techniques. They are often misdiagnosed
because perineural cysts that cause symptoms are so rare. These cysts can be
drained to provide temporary relief of symptoms. However, only surgery can keep
them from coming back or refilling with fluid and producing symptoms again. If
not treated, the rare cysts that cause symptoms can produce permanent
What are Perineural Cysts?
A cyst is a sac that can
form anywhere in the body and is filled with air or some type of fluid. Most of
these are completely benign and noncancerous. Perineural cysts are those that
form in the sacrum, or the base of the spine. They form around the roots of
nerves in this part of the body. They are different from other cysts that can
form in the sacrum because the nerve fibers from the spine are found within the
cysts. Women are more likely than men to develop perineural cysts.
Symptoms of Perineural Cysts
People with perineural cysts
are not likely to have any symptoms. Most people who have them never know they
are there. Symptoms only occur when the cysts fill up with spinal fluid and
expand in size. When this happens, the enlarged cysts can compress nerves and
cause other problems.
The most common symptom
associated with perineural cysts is pain. The enlarged cysts can compress the
sciatic nerve, causing sciatica.
This condition is characterized by pain in the lower back and buttocks, and
sometimes down the back of the legs. The pain can be sharp and sudden or more
mild and achy. Sciatica is also often accompanied by numbness in the same
areas, and muscle weakness in the feet and legs.
In severe cases where
perineural cysts have enlarged, there can be a loss of bladder control, constipation,
or even sexual dysfunction. Having these symptoms with perineural cysts is
possible, but very rare.
Causes of Perineural Cysts
Why cysts grow in the sacrum
is not known, but there are reasons why they may develop into enlarged cysts
that cause symptoms. If a person experiences some type of trauma in the
relevant area of the back, undiagnosed perineural cysts can begin to fill up with
fluid and start producing symptoms.
Types of trauma that can trigger symptoms include falls, injuries, and
Diagnosis of Perineural Cysts
Because the vast majority of
perineural cysts cause no symptoms, most are never diagnosed. However, a doctor
can order imaging tests to identify them when a person experiences symptoms.
Magnetic resonance imaging (MRIs) can show cysts. A computed tomography (CT)
with a dye injected into the spine can show if fluid is moving from the spine into
cysts in the sacrum.
Treatments for Perineural Cysts
For most cases of perineural
cysts, no treatment is needed. If a patient exhibits symptoms, however, they may
need treatment to relieve the pressure called by the enlarged cysts. A quick fix
is to drain the cysts of fluid. This can relieve symptoms immediately, but it
is not a long-term treatment. The cysts usually fill up again.
The only permanent treatment
for perineural cysts is to have them surgically removed. Surgery is usually
recommended for serious, chronic pain, as well as bladder problems from the
Outlook for Perineural Cysts
In the large majority of
cases of perineural cysts the outlook is excellent. Most people with these
cysts will probably never have any symptoms or need any treatment. Only one
percent of people with perineural cysts experience symptoms (Lucantoni et al.,
2011). For those with symptoms, surgery to remove the cysts typically relieves
those symptoms and the cysts rarely recur. People with cysts that cause
symptoms who do not seek treatment might experience nerve and neurological