Selective Dorsal Rhizotomy for Treatment of Spastic Cerebral Palsy

Cerebral palsy (CP) is a disorder that causes problems with movement and balance due to a brain injury that occurs during brain development.  Sometimes cerebral palsy is noticed soon after birth, but in other children, the disorder won’t be noticed until a few years later.  Babies with cerebral palsy are often slow to roll over, sit, crawl, or walk, and may look weak and have poor head position.  Cerebral palsy noticed a few years later in life is characterized by abnormal muscle tone, poor reflexes and motor coordination, permanently fixed/tight muscles (spasticity), spasms and other involuntary movements, unsteady walking, problems with balance, and scissor or toe walking.

Spastic cerebral palsy is the most common type of cerebral palsy.  Normally, muscles coordinate in pairs; when one group of muscles contract (tighten), the other group relaxes.  This allows free movement. People with spastic cerebral palsy have complications in brain-to-nerve-to-muscle communication, and the balanced degree of muscle tension is disrupted.  Muscles affected by spastic cerebral palsy become active together, which effectively blocks coordinated movement.  Thus, the muscles in children with spastic cerebral palsy are constantly stiff, or spastic.

The main difference between spastic diplegia (spastic cerebral palsy that primarily affects the lower body) and a normal gait (body propulsion/movement) pattern is its signature “scissor gait.”

Scissor gait is characterized by the following:

• Hips and pelvis are often locked, as if crouching while walking
• Knees and thighs may cross or touch while walking
• Ankles may be turned inwards while walking
• Feet often make contact with the ground primarily at the ball of the foot, not the heel (may look like “tip toe” walking)
• Arms and hands may go outwards from the body to provide balance

The degree of spasticity varies widely from child to child. Some have barely noticeable misalignments, while others require the use of a walker or wheelchair. Above the hips, children with spastic diplegia typically retain normal or near-normal muscle tone and range of motion, though some spasticity may also affect the upper body.  Additionally, because leg tightness often leads to instability when in an upright position, extra muscle tension usually develops in the upper body, shoulders, and arms due to compensatory stabilization movements.

The causes of spastic cerebral palsy include (among others):

• Hypoxic-ischemic encephalopathy (HIE): A form of brain damage that occurs around the time of birth, when the flow of oxygenated blood to a baby is disrupted.
• Exposure to toxins (such as too much bilirubin/untreated jaundice)
• Infant brain bleeds
• Neonatal infections
• Periventricular leukomalacia (PVL): A condition in which the brain’s white matter is damaged.

Selective dorsal rhizotomy (SDR) is a surgical procedure that selectively destroys malfunctioning nerve roots in the spinal cord, most often to treat neuromuscular conditions, such as spastic diplegia and other forms or spastic cerebral palsy.  During an SDR, the lower vertebrae are opened to reveal the spinal cord, which contains neurons of the central nervous system.  These neurons (bundles of nerve fibers) channel messages between the brain and different areas of the body.  Electrical stimulation is used to identify and sub-divide sensory and motor nerves.  This procedure continues until the specific nerves and nerve roots affecting the spastic muscles are identified and cut.  Due to the size of the nerves and rootlets, this is a very precise procedure and surgery can last several hours.  It requires general anesthesia.

Many months of physical therapy (PT) are needed after the surgery to train and retrain the legs.  In fact, PT is necessary in order to maximize benefits of the surgery.

Research shows that selective dorsal rhizotomy coupled with PT provides significant benefit over PT alone.  Spasticity is significantly reduced and there is improvement in function as measured by the Gross Motor Function Measure (GMFM).  The GMFM is a classification system that describes the gross motor function of children with cerebral palsy on the basis of their self-initiated movement, with particular emphasis on sitting, walking, and wheeled mobility.  Spasticity, range of motion, and functional muscle strength typically improve through five years or more after surgery.  SDR patients usually show sustained improvement in alignment and postural stability, as well as an increased ability to perform difficult transitional movements.  There also are long-term improvements of gait abnormalities.

For those under 18 years of age, selective dorsal rhizotomy requires that they be:

• At least 2 years of age
• Have a diagnosis of spastic diplegia, spastic quadriplegia, or spastic hemiplegia
• Have some form of independent mobility (crawling or walking with or without an assistive device)
• Have a history of premature birth; if born at full term, the child must have typical signs of spastic diplegia
• Have no severe damage to the basal ganglia on MRI examination
• Have a potential for improvement in functional skills

For adults between 19 and 40 years of age, selective dorsal rhizotomy requires:

• A diagnosis of spastic diplegia
• A history of premature birth
• That the person currently ambulates (walks/moves about) independently without an assistive device
• That the person has no fixed orthopedic deformities that either prevent current walking or would prevent walking after SDR; in these cases orthopedic release surgeries are to be done first, after which SDR can be discussed.
• The potential for functional gains after SDR
• Strong motivation to attend intensive PT and perform home exercise program

In the limited number of adults with spastic diplegic that have been treated with SDR, satisfactory functional gains are similar to those in children.

All candidates for selective dorsal rhizotomy must have good muscle strength in the legs and trunk.  Candidates also must have adequate motor control, or the ability to make reciprocal movements for crawling or walking, and to move reasonably quickly from one posture to another.

In pediatric SDR, candidates are children with cerebral palsy who have shown age-appropriate progression in motor development, but whose spasticity hinders the development of skills and/or causes gait patterns such as scissor gait.  In adults, the primary requirements are that candidates can ambulate independently, but spasticity limits energy, flexibility, walking speed and balance, and sometimes causes pain and muscle spasms.

There are a few situations in which it is likely that someone may not be a candidate for the selective dorsal rhizotomy.  These situations include those who have suffered meningitis, a congenital (birth-originating) brain infection, congenital hydrocephalus unrelated to the person’s premature birth, a person who has suffered head trauma, or a person with some sort of familial disease (people with hereditary spastic diplegia are said to not be SDR candidates).

Also precluded are people who have a “mixed” cerebral palsy with predominant rigidity/dystonia, significant athetosis (involuntary writhing movements of the fingers, hands, toes, feet, arms and/or legs) or ataxia (lack of voluntary coordination of muscle movements).  People who have very severe scoliosis also are precluded.   As with any procedure, however, an individual evaluation is needed in all instances to determine eligibility.

Most rehabilitation from selective dorsal rhizotomy is done on an outpatient basis, though it may also include an initial several-week inpatient component.  Typical base restrengthening and restoration of full ambulatory function takes about 12 weeks of intensive PT, 4-5 times per week.  Subsequent buildup and maintenance beyond that initial several-week period is just as necessary, and may require continued 4-5 times per week therapy, as much as 6 months postoperatively, for a total of about 1 year and 4 months after surgery in order to achieve maximum basic functionary movement from the surgery.