Evaluation of Spasticity to be Managed by Selective Dorsal Rhizotomy in Children

History

See Presentation for history at presentation.  It is key that a thorough history of birth, development and prior management including surgeries be obtained as part of the assessment.

Examination

Strength

• Antigravity strength in legs: Locomoting children who are being considered for SDR need to be evaluated for leg strength to insure that it is sufficient to maintain the standing and walking function.  Early on in their experience the Cape Town group found that children who could rise from a squat or heel sitting position to a full stand for 7 consecutive cycles using only their leg musculature to maintain their standing/walking function after elimination fo spasticity by a SDR (54).  Children with functionally important abilities in the standing position should not undergo a SDR if they cannot do this maneuver.

Muscle Tone

• Hypertonia:  First, the PROM is measured for the musculature of the leg.  The limbs are evaluated for limitation in movement, and the . This is done by slowly moving a limb in the desired direction (to avoid triggering an increase in muscle hypertonia) The extent of movement is measured and recorded in degrees short of normal range (goniometry).  The limb is then rapidly and repetitively moved in a desired direction and the degree of movement recorded as the number of degrees short of normal range. The difference between this number and the degrees of PROM in the direction being measured is the amount of movement limitation due to spasticity.  Typically, the degree of hypertonia present is graded using the Modified Ashworth Scale (even though this scale was not developed to measure just spasticity).

Modified Ashford Scale: This is the most widely accepted tool for quantifying spasticity although it is critized for its poor intra- and interrater reliability and the fact that it does not control for factors such as speed of limb movement which may affect limb tone (55).

• Hypotonia in truck musculature:  In the locomotor group, low tone in the musculature of the trunk assessed for the sitting position. If the child has difficulty holding an erect posture while sitting (the so-called floppy trunk) then hypotonia of the trunk musculature is present.  This is a relative contraindication as it predicts difficulty with balance when upright and learning to walk.  The child can be evaluated for treatment with intrathecal baclofen instead of SDR.
• Care to avoid misidentification of type of hypertonia: Most patients present with a mixed form of CP, and only those whose hypertonia is primarily spasticity should be considered for SDR.    Children with mixed CP can exhibit abnormal involuntary movements of the distal extremities (athetosis) or proximal limbs and trunk (dystonia) . Chorea, predominantly presenting as involuntary abrupt, jerky movements, may also be present, occurring spontaneously or during periods of stress and emotions. If the athetosis, chorea, or dystonia are the predominant patterns of motor difficulty, surgical treatment of spasticity using SDR is contraindicated.

Motor Function

• Grading of functional development: In 1987 Russell reported on a rating tool, the GMFM, for measuring motor development in infants and young children that could be used to measure the impact of physical therapy on delayed motor development (40).  It was shown to have high intra- and interrater reliability and it has been widely accepted as the “gold standard” for tracking motor function in young and disabled children.
• Grading of motor function: Children assessed in the spasticity clinic are graded with respect to the functional ability of their legs. In turn, the different preoperative grades given to the children will determine what the objectives of the treatment will be and the child’s potential for locomotor improvement. Scales such as that shown below focus on leg function and not on locomotive means of the child (as is the case with the GMFCS).  Over time, as the evaluation team gains experience following children who have undergone SDR, pre-operative motor function grades can be used to predict outcome in candidates for SDR.

Motor Function Grading: A grading scheme developed at the Rusk Institute in New York for categorizing SDR candidates according to their motor function (14).

• Children of GMFCS Grade 4-5: Children with no locomotive potential (GMFCS 4 & 5) may also benefit from SDR in certain specific incidents when spasticity is severely compromising their care and no other treatment is available.
  Efforts should be made to evaluate function for each child, regardless of GMFCS Grade: Evaluate , posture, movement and function in standing, sitting, and lying. Functions must be evaluated that are specific to the patient, e.g., sitting posture in a wheelchair, ability to reach out for a cup to drink water f if the child is wheelchair bound vs. climbing stairs for a mobile child.

Laboratory Tests

• Coagulopathy evaluation if history indicates: Patients with cerebral infarction should be considered for coagulation (hypercoagulation) disorder investigation. Also be aware of other medications that the patient may be using for comorbid diseases such as valproate for epilepsy, which may affect platelet function and cause abnormal oozing during surgery.

Radiologic Tests

• Review images previously obtained: Most children diagnosed with CP will have undergone MRI of the brain. Detection of brain malformations in children with CP can suggest an underlying genetic or metabolic etiology, and that,in turn, would represent a contraindication to proceed a SDR. Always evaluate the spine as well. Do not be caught out by the full-term CP patient with spasticity that has a degenerative neurological condition or a spinal abnormality.
• Other x-rays: Basic x-rays of the hips, if recent imaging is not available, are also a good practice in any child with CP. This helps monitor for progressive hip subluxation.

Nuclear Medicine Tests

• Not indicated

Electrodiagnostic Tests

• Not indicated: Preoperaticve electrodiagnostic testing is not needed when evaluating candidates for a SDR procedure.

Neuropsychological Tests

• Not mandated: There are no clear guidelines or recommendations for neuropsychological testing. However, Peacock and colleagues have reported on the improved outcomes in children with good baseline mental abilities compared with those with impaired abilities (26) So, an argument could be made for the use of neuropsycholical testing to identify modifiers that could affect the outcome of post-SDR therapy.

Correlation of Tests

• History and examination: As units gain experience assessing children for SDR, they typically look for children born prematurely around 28-32 weeks gestation who on examination have spastic diplegia, the so-called ideal candidate.