A posterior fossa decompression is a surgical procedure performed to remove the bone at the back of the skull and spine. The dura overlying the tonsils is opened and a patch is sewn to expand the space, similar to letting out the waistband on a pair of pants. The goals of surgery are to stop or control the progression of symptoms caused by tonsillar herniation, to relieve compression of the brainstem and spinal cord, and to restore the normal flow of cerebrospinal fluid (CSF). The surgery takes about 2 to 3 hours and recovery in the hospital usually lasts 2 to 4 days.
You may be a candidate for decompression surgery if you have:
• An abnormal collection of CSF in the spinal cord (syrinx)
• A Chiari malformation obstructing CSF flow (confirmed by cine MRI) and is causing severe or worsening symptoms
What happens before surgery?
During the office visit, the neurosurgeon will explain the procedure, its risks and benefits, and answer any questions. Next, you will sign consent forms and complete paperwork to inform the surgeon about your medical history (i.e., allergies, medicines, vitamins, bleeding history, anesthesia reactions, prior surgeries). Discuss all medications (prescription, over-the-counter, and herbal supplements) you are taking with your healthcare provider. Some medications will need to be continued or stopped the day of surgery. You will be scheduled for presurgical tests (e.g., a blood test, electrocardiogram, chest X-ray, and CT scan) several days before surgery.
Stop taking all non-steroidal anti-inflammatory medicines (Naprosyn, Advil, Motrin, Nuprin, Aleve) and blood thinners (coumadin, Plavix, aspirin) 1 week before surgery. Additionally, stop smoking and chewing tobacco 1 week before and 2 weeks after surgery, as these activities can cause bleeding problems. Wash your hair with Hibiclens® (chlorhexidine) antiseptic soap for 3 consecutive days prior to surgery. No food or drink is permitted past midnight the night before surgery.
Morning of surgery
• Shower using antibacterial soap. Dress in freshly washed, loose-fitting clothing.
• Wear flat-heeled shoes with closed backs.
• If you have instructions to take regular medication the morning of surgery, do so with small sips of water.
• Remove make-up, hairpins, contacts, body piercings, nail polish, etc.
• Leave all valuables and jewelry at home (including wedding bands).
• Bring a list of medications (prescriptions, over-the-counter, and herbal supplements) with dosages and the times of day usually taken.
• Bring a list of allergies to medication or foods.
Arrive at the hospital 2 hours before your scheduled surgery time to complete the necessary paperwork and work-ups. You will meet with a nurse who will ask your name, date of birth, and what procedure you are having. The nurse will explain the preoperative process and discuss any questions you may have. An anesthesiologist will talk with you to explain the effects of anesthesia and its risks. An intravenous (IV) line will be placed in your arm before transport to the operating room.
What happens during surgery?
Step 1: prepare the patient
You will lie on the operating table and be given anesthesia. Once asleep, your head will be placed in a 3-pin skull-fixation device, which attaches to the table and holds your head in position during surgery. An inch wide strip of hair is shaved along the planned incision. The scalp is prepped with an antiseptic.
Step 2: make a skin incision
A skin incision is made down the middle through the neck muscles so that the surgeon can see the skull and top of the spine. The skin incision is about 3 inches long (Fig. 14). The skin and muscles are lifted off the bone and folded back.
|Figure 14. A 3 inch incision is made down the middle of the neck. Shaded areas represent bone to be removed.
||Figure 15. A small portion of the skull is removed (craniectomy). The dura covering the brain is seen.
Step 3: remove bone
The surgeon removes a small section of skull at the back of your head (suboccipital craniectomy). In some cases the bony arch of the C1 vertebra may be removed (laminectomy). These steps expose the protective covering of the brain and spinal cord called the dura (Fig. 15). Bone removal relieves compression of the tonsils.
Step 4: open the dura
Next, the surgeon opens the dura to view the tonsils and cisterna magna (Fig. 16). Some surgeons perform a Doppler ultrasound study during surgery to determine if opening the dura is necessary. Sometimes bone removal alone may restore normal CSF flow.
Step 5: reduce the tonsils (optional)
Depending on the size of herniation, the stretched and damaged tonsils may be shrunk with electrocautery. This shrinkage ensures that there is no blockage of CSF flow out of the 4th ventricle.
Step 6: attach dura patch
A patch of synthetic material or the patient’s pericranium (a piece of deep scalp tissue just outside the skull) is sutured into place (Fig. 17). This patch enlarges the dura opening and the space around the tonsils. The dural patch is sutured in a watertight fashion. The suture line is covered with a dural sealant to prevent CSF leak (Fig. 18).
|Figure 16. The dura is opened.
||Figure 17. A patch is sewn to the dura to enlarge the CSF space.
||Figure 18. A dural sealant applied to the suture line prevents CSF leak.
Step 7: close the incision
The strong neck muscles and skin are sutured together. A dressing is placed over the incision.
What happens after surgery?
You will wake up in the recovery area called the post-anesthesia care unit (PACU). Your throat may feel sore from the tube inserted to assist your breathing during surgery. Once awake, you’ll be moved to your room. Blood pressure, heart rate, and respiration will be monitored. If you feel nausea or headache after surgery, medication can be given. When your condition stabilizes, you will be discharged in the care of your family or a caregiver, usually 1 or 2 days after surgery.
The length of the hospital stay varies but is usually 2 to 3 days. When released from the hospital, you will be given discharge instructions:
• After surgery, pain is managed with narcotic medication. Because narcotic pain pills are addictive, they are used for a limited period (2 to 4 weeks). Thereafter, pain is managed with acetaminophen (e.g., Tylenol) and nonsteroidal anti-inflammatory drugs (NSAIDs) (e.g., aspirin; ibuprofen, Advil, Motrin, Nuprin; naproxen sodium, Aleve).
• Regular use of narcotics can cause constipation, so drink lots of water and eat high fiber foods. Stool softeners (e.g., Colace, Docusate) and laxatives (e.g., Dulcolax, Senokot, Milk of Magnesia) may be bought over-the-counter.
• Ice packs for 20 minutes can help relieve neck and shoulder pain and muscle spasms. Muscle relaxants may be prescribed.
• Avoid activities that increase pressure in the head:
- Bending over, with head low
- Straining / pushing during a bowel movement
- Prolonged coughing (use a cough suppressant)
• Do not drive after surgery until discussed with your surgeon and avoid sitting for long periods.
• Do not lift anything heavier than 5 pounds (e.g., gallon of milk), including children.
• Housework and yard-work are not permitted until the first follow-up office visit. Avoid gardening, mowing, vacuuming and loading / unloading the dishwasher, washer, or dryer.
• Do not drink alcoholic beverages while on pain medicine.
• Gradually return to your normal activities. Fatigue is common.
• Begin the isometric neck exercises and stretches as instructed.
• Walking is encouraged: start with short walks and gradually increase the distance. Wait to participate in other exercise until discussed with your surgeon. Avoid getting over heated.
• Shower and wash hair with mild shampoo after surgery unless otherwise directed by your surgeon. Avoid water directly on the incision or rubbing the incision dry. No tub baths, hot tubs, or swimming pools.
• Sutures or staples, if used, will need to be removed 7 to 14 days after surgery. Ask your surgeon or call the office to find out when.
When to Call Your Doctor
• Fluid may accumulate under the skin around the incision. A visible swelling that is soft and squishy may be a sign of cerebrospinal fluid (CSF) leakage. A clear sticky fluid may leak from the incision. Call the surgeon should any drainage occur.
• If you experience any of the following:
- A temperature that exceeds 101º F
- An incision that shows signs of infection, such as redness, swelling, pain, or drainage.
- Decreased alertness, increased drowsiness, weakness of arms or legs, increased headaches, vomiting, or severe neck pain that prevents lowering your chin toward the chest.
Before you leave the hospital, appointments with the neurosurgeon will be scheduled 10 to 14 days after surgery to remove your sutures and check your recovery. Recovery from the actual surgery varies from 4 to 6 weeks, depending on your general health.
After surgery, you can expect headache and neck pain from the incision that may last several weeks. You will be given isometric neck exercises to do at home. These will help with neck mobility and healing. The exercises can be done while sitting, standing, or lying on your back. Repeat this series at least 4 times a day.
Neck stretches. With good posture, take a deep breath and relax.
- Turn your head slowly to the right and left several times.
- Bend your right ear to shoulder and repeat on other side.
- Extend your neck forward and backward.
- Tilt your chin toward chest and slightly up.
Isometric neck exercises. The key to isometric exercise is to prevent your head from moving. Resist the pressure of your hands and maintain constant tension in your neck muscles. Be sure to breathe. Holding your breath may cause an increase in your blood pressure that may result in becoming dizzy or lightheaded.
- Side neck muscles. Place your palm against the right side of your head (temple area). Take a breath. Have your head match the resistance on the right side without bringing your ear towards the shoulder. Breathe out to 10 seconds. Repeat 10 times. Switch sides to work your left side.
- Front neck muscles. Place the palms of your hands on the top of your forehead. Take a deep breath in through the nose. Have your forehead match the resistance of your palm. Breathe out slowly through your mouth to the count of 10. Repeat 10 times.
- Back neck muscles. Clasp your hands behind the top of your head. Take a breath in. Press the back of your head against your hands and breathe out. Hold this position for 10 seconds and repeat 10 times.
Patients typically return to work in 4 to 6 weeks, but be sure to check with your surgeon. A follow-up cine MRI is planned for 6 months to 1 year.
Recovery from the Chiari syndrome and its symptoms may take months or longer. Returning to "normal" is gradual – time is your best ally (listen to Ray's story). Slowly increase activity, avoid strenuous lifting, adhere to instructions and maintain a positive attitude. Focus on the symptoms that have improved, and have patience with those symptoms that remain. Keep a symptom diary (download a PDF) to track your progress over time.
What are the results?
The results of your decompression surgery depend on the severity of the Chiari malformation and the extent of any previous brain and nerve injury before treatment. Eighty five to 95% of patients experience some relief of symptoms . However, nearly 50% of patients may continue to have residual symptoms from syringomyelia. If injury in the spinal cord has already become permanent, surgery won't reverse the damage.
Exertional headache and neck pain respond well to decompressive surgery as do most of the brainstem signs (e.g., swallowing problems, facial pain/numbness, voice changes, tinnitus, eye problems, dizziness). Recovery of sleep problems, memory, and spinal cord signs (e.g., numbness or tingling in hands and feet, muscle weakness) take longer and may not completely return to normal.
Figure 19. MRIs before and 1 year after surgery showing restored CSF flow (blue line) around the tonsils and disappearance of the syrinx (yellow arrow) in the spinal cord.
Decompression surgery may allow the syrinx to drain on its own. Follow up is needed to monitor CSF flow and the syrinx site. This is evaluated at one year with cine MRI (Fig. 19). For any residual symptoms, you and your doctor will discuss possible options to determine the best care.
Recurrence of compression or obstruction of CSF flow is rare.
What are the risks?
No surgery is without risks. General complications of any surgery include bleeding, infection, blood clots, stroke, reactions to anesthesia, and death (rare). Specific complications related to a Chiari decompression craniectomy and duraplasty may include:
• Risk of head and neck pain is variable.
• Cerebrospinal fluid (CSF) leakage is the escape of CSF that flows around the brain. This usually takes the form of a squishy pocket of fluid or drainage from the incision. If leakage is suspected, apply a pressure dressing over the incision and contact the surgeon immediately. If the leak continues, surgical repair may be necessary. New closure techniques and use of biologic glue greatly reduces the risk of CSF leak.
• There is a risk of pseudomeningocele, an abnormal collection of cerebrospinal fluid (CSF) under the tissues of the neck. The collection may resolve on its own; however notify your surgeon if this occurs.
• Nerve or brain damage may cause permanent disability.
reviewed by: John M. Tew, MD, Nancy McMahon, RN
Mayfield Clinic, University of Cincinnati Department of Neurosurgery