Keywords spasticity - rhizotomy - cerebral palsy - electrical stimulation - surgery
Palavras-chave espasticidade - rizotomia - paralisia cerebral - monitorização intraoperatória - cirurgia
Introduction
Spasticity is a motor disorder characterized by increased muscle tone, leading to
a frame of resistance to passive articular movement. In the clinical practice, spasticity
is one of the positive signs of upper motor neuron syndrome, which may be accompanied
by stiffness, hyperreflexia, primitive reflexes, hypertonia of antigravitary muscles,
increased reflexogenic areas, bladder hyperreflexia and clasp knife spasticity. Negative
signs can also accompany the clinic examination in these patients, such as paresis,
incoordination, fatigue, reduction of tissue elasticity, among others. These signs,
under extreme conditions, impair posture, ambulation and self-care. As a direct consequence,
we can cite pain, fractures and decubitus ulcers. The worsening of these patients
also worsens the quality of life of their respective caregivers. However, the degree
of spasticity may help some patients in the maintenance of posture and gait.
Cerebral palsy (CP) is considered one of the most important causes of spasticity,
especially in children in whom, when associated with other symptoms such as dystonia,
ataxia or stiffness, it leads to a serious disability condition. Even with the advances
in care in the neonatal period, an increase in the incidence of CP cases has been
observed, which may be related to an increase in the survival of children with very
low weight.[1 ]
[2 ]
Etiologically, CP is associated with prenatal events (multiple pregnancies, maternal
alcoholism, infections), perinatals (hemorrhages, infections, bradycardia, fetal anoxia)
and postnatal (drowning, traumatic brain injury, among others).[3 ]
To objectively evaluate spasticity, we use quantitative and qualitative indicators
that measure the degree and functional repercussion of patients.
The modified Ashworth scale is the most widely used to assess muscle tone. It is a
qualitative scale that evaluates the degree of spasticity, measured according to the
degree of resistance to passive movement of a segment moved rapidly by an examiner[4 ] ([Table 1 ]). The Penn scale, also widely used in the clinical practice, evaluates the occurrence
of spasms ([Table 1 ]).
Table 1
Modified Ashworth Scale and Penn Scale
Modified Ashworth Scale
Penn Scale
Degree
Description
Description
0
Normal muscular tonus
Absence of spasms
1
Increase in tone at the beginning or end of the arc of motion
Only spasms precipitated by stimuli
1+
Increased tonus in less than half of the arc of motion, manifested by abrupt tension
and followed by minimal resistance
2
Increased tonus in more than half of the arc of motion, but the affected part is easily
mobilized
Spontaneous, strong and irregular spasms, less than one per hour
3
Considerable increase in muscle tone with difficult passive movement
Spontaneous spasms, one or more per hour
4
Rigid parts in flexion or extension
Spontaneous spasms, more than ten per hour
The Tardieu scale measures the intensity of the muscular reaction to passive movement.
The arc of motion should be measured by a goniometer. The angle of resistance is the
measure relative to the position of minimum stretch for all joints. It is a good option
to evaluate the gain after treatment ([Table 2 ]).
Table 2
Tardieu Scale
Modified Tardieu Scale
Degree
Description
0
No resistance in the course of passive movement
1
A slight resistance along the course of the passive movement, without precision of
the specific angle
2
Clear stiffness at a specific angle, interrupting the stretch, followed by relaxation.
3
Fatigable Clin that lasts less than 10 seconds and appears at a specific angle, while
the evaluator is maintaining pressure.
4
Non-fatigable Clin that lasts for more than 10 seconds and appears at a specific angle
while the evaluator is maintaining pressure.
Gait can be used to evaluate the improvement of spasticity, either in clinical observation
or in the gait laboratory using dynamic electromyography (EMG).[5 ]
Other tests are also used, such as upper limb skill tests and dynamometry hold,[6 ] measurement of functional independence, Barthel index (quantitative method that
evaluates independence in daily activities), quantitative muscle strength and myometrial
tests,[7 ] and the Lyon Université scale, which evaluates automatisms.[8 ] Initially, spasticity treatment should focus on the causal factor, be it tumor,
inflammation, multiple sclerosis, infectious disease, vascular disease, degenerative
disease, hydrocephalus, etc. It is mandatory to prevent or eliminate factors that
aggravate spasticity, such as pain, visceral dysfunctions, decubitus ulcers, urinary
infections, constipation, heterotopic ossification, ingrown nail, psychological stress
and sleep disorders.
Neurosurgical treatment of spasticity is diverse. Intrathecal infusion of myorelaxants,
such as baclofen, tizanidine, midazolam, clonidine or morphine, is indicated in patients
with preserved motor function and when oral medication is not tolerated or effective.
Spinal cord stimulation is an option in mildest cases. Nerve neurotomies such as shutter,
sciatic, posterior tibial, fibular or femoral — in the lower limbs — and musculocutaneous,
radial or median in the upper limbs, are options for more localized spasticity.
Percutaneous radiofrequency rhizotomy is used in debilitated patients and in the treatment
of spastic bladder. The longitudinal myelotomy (longitudinal section of the spinal
cord gray matter) is reserved for paraplegics with total impairment of sexual and
sphincter function. The lesion of the Lissauer tract and the posterior horn of the
spinal cord, proposed by Sindou in 1969, is used in the treatment of spasticity and
pain in the lower limbs.[9 ] Dentatotomy is efficient in the treatment of spasticity evidenced by several casuistics.[10 ] A selective dorsal rhizotomy (SDR) is a safe, economical and possible technique
to be performed in most centers with neurosurgical support, especially pediatric.
It is an excellent option in cases of ambulatory patients and quadrispastic children.
Patient Selection
Up to the present moment, there are no completely efficient measures to repair the
damage to motor areas that control movement. We have several therapeutic measures
for the treatment of spasticity, which include: drug therapy, physical therapy, occupational
therapy, applications of botulinum toxin, orthopedic surgery, SDR, in addition to
the surgical procedures already explained. The choice for the use of these therapies
is extremely important for the patient, since victims of polytraumatism are usually
young with long survival, and that children with CP have a mean survival of 20 years.[11 ]
Selective dorsal rhizotomy is a definitive surgery in which the cauda equina is exposed
through osteoplastic laminotomy followed by L2-S1 roots identification.
The results of dorsal rhizotomy have been known since the initial experiments of Sherington
(1894) in decerebrated cats. In 1889, Abbe and Bennett described the result of nerve
root section with pain control.[1 ]
[13 ] In 1913, Foerster achieved improvement in spasticity after dorsal rhizotomy was
performed.[14 ] Despite good results, dorsal rhizotomy was abandoned for about half a century, due
to the comorbidities related to the procedure. Only in 1960s, Gros et al performed
partial rhizotomies EMG to help identify dysfunctional nerves.[15 ] Fasano et al described the criteria for evaluating abnormal motor responses after
electrical nerve stimulation.[16 ] The traditional surgery proposed by Peacock et al consists of a laminotomy from
L1 to L5 with a laminectomy of S1-S2.[17 ] In many services, the level of the approach is varied, including lumbar topographies
or medullary cone (MC), aiming to maintain a balance between the preservation of strength
and the elimination of spasticity.[3 ]
The use of electromyography (EMG) to define which dorsal roots were injured also became
a reason for discussion due to the variability of the motor response,[18 ] of the standardization of the technique used in each center,[19 ] the use of drugs used in anesthetic induction that may interfere with the results
of stimulation,[20 ] and the variability of segmental innervation of the musculature of the lower limbs.[21 ] One study performed a histological analysis of the sectioned roots of children with
CP submitted to SDR, and found that the altered roots in the EMG presented axonal
degeneration or demyelination. The roots that appeared normal in the EMG presented
minimal histological alterations limited to myelin sheath or demyelination without
axonal degeneration, showing that this is a significant method to find the roots that
should be sectioned.[22 ]
Spastic patients present contractions sustained at a stimulation of 50 Hz, but did
not present the same contralateral pattern.[21 ] We have observed in daily practice that a stimulation of 5 Hz is enough to differentiate
the motor and sensitive roots . Intraoperative EMG is essential in the identification
of the hyperactive roots, contributing to a balance between the reduction of spasticity,
bladder control and the preservation of sensitivity.
Studies have shown that SDR is accompanied by significant improvement in several parameters,
for example, improvement in motor function,[23 ]
[24 ]
[25 ] significant spasticity reduction,[26 ] strength gain,[27 ] increase in movement amplitude,[28 ]
[29 ] and qualitative[30 ] and quantitative.[31 ]
[32 ] improvements in the upper limbs motor function. Some services use strict criteria
to indicate SDR, including the Reimer index, which, when > 50%, can postpone SDR for
a period of 6 to 12 months.[3 ] However, early dorsal rhizotomy would prevent a posterior approach in soft tissues
and articular joints.[33 ]
In the end of the 1980s, the main concern with intraoperative complications was the
risk of bronchospasm and aspiration pneumonia; However, with the development of new
anesthetic techniques and new drugs, the risks were reduced.[34 ]
Children with CP who evolve with spastic diplegia or tetraplegia, associated with
an important spastic component in the lower limbs and minimal impairment in the upper
limbs, are the main beneficiaries of this technique. Selective dorsal rhizotomy is
not indicated for children under 2 years old because the CP cannot be safely diagnosed
in this age group. Dystonia is not an absolute contraindication for surgery, but if
there are lesions in basal nuclei with dystonic predominance, other procedures present
better results, such as pallidotomy or deep cerebral stimulation. History of multiple
orthopedic surgeries counterclaims the procedure due to fixed deformities and muscle
weakness.[24 ]
The main objective of SDR is the reduction of two levels in the Ashworth scale in
the deprecated muscular target of the lower limbs. In 50% of the cases, there is also
improvement in the upper limbs.[35 ]
For a good postsurgical outcome, the patient should be duly selected. The clinical
examination will define which segments are most affected by the disease and which
would be the focus of the rhizotomy. A multidisciplinary team that includes physiatrist,
orthopedist, neuropediatrician, psychologist and physical therapist is essential.
Posture, sphicnter control, amplitude of the articular movements, whether there are
bone or muscular deformities, presence of dystonia, dyskinesias, presence of spasms,
gait observation, cognition and comorbidities should be evaluated.
Technique Description
The technique created by Park et al[36 ] in 1991 differs from the others by removing the lamina of one or two vertebrae,
while traditional techniques use laminectomy from five to seven vertebrae.
The patient is sedated and intubated in dorsal decubitus on the lateral stretcher
at the surgical table ([Fig. 1 ]). Medications that do not alter the EMG activity, such as long-lasting neuromuscular
blockers, should be avoided.
Fig. 1 Patient intubated on a side stretcher at the surgical table. Appropriate cushions
are positioned to avoid decubitus ulcers after the patient is positioned in ventral
decubitus.
After orotracheal intubation, electrodes are introduced bilaterally in the long, large
lateral, tibial anterior and medial gastrocnemius muscles ([Fig. 2 ]).
Fig. 2 Positioning of the EMG electrodes in the muscles of the lower limbs.
Subsequently, the patient is transferred carefully to the ventral decubitus position
to maintain soft structures at strategic points of the body to avoid decubitus ulcers.
In this position, electrodes are introduced in the perichannel region and the wires
are fixed with adhesive in the patient's lower limb ([Fig. 3 ]).
Fig. 3 Patient in ventral decubitus with electrodes positioned on the lower limbs and in
the perichannel region.
We use continuous EMG and a trigger with 14 channels to stimulate the following L1-L2,
L2-L3, L3-L4, L5-L5, L5-S1, S1-S2 and on-the-side segments. The interpretation of
the EMG result is done by the neurophysiologist. Intraoperative EMG provides valuable
information to the neurosurgeon that helps differentiate the sensory root of the motor,
in addition, the mapping of the sphincter fibers is a safety factor for not adding
deficits to the patient.[37 ] It is also necessary to have the utmost care with the sacral fibers of S2 to S4
to protect the bladder and sexual function.[38 ] The patient is kept in a slight position of Trendelenburg to reduce CSF losses.
Radioscopy or ultrasonography (in case of children < 10 years old) is used to find
the vertebral level to be approached (previously chosen through magnetic resonance
imaging [MRI]) to find the MC end, and the incision is made after marking this level
([Fig. 4 ]). Since laminectomy should be limited to this segment, it is important that the
MC is found.
Fig. 4 Left: patient positioned in ventral decubitus at the moment radioscopy is performed
to find the level of the spine that will be approached. Right: marking on the skin
with the size of the incision.
After making a horizontal incision, with the opening of the subcutaneous cell tissue,
we dissected the dorsal musculature away from the thorny process until the slides
of the L1 vertebra were exposed, in this example ([Fig. 5 ]). After exposure of the interlaminar space, the yellow ligament is removed with
visualization of the dural sac. A linear incision is made to expose the medulla and
visualize the MC and the cauda equina.
Fig. 5 Left: dorsal musculature distanced with visualization of the supraspinatus ligament
and spinous process of L1. Right: after laminotomy, exposure of the dural sac to the
level of the medullary cone.
From this moment, saline solutions should be avoided because they alter the responses
of the EMG. The edges of the dura mater are anchored with Vicryl or nylon 4.0 to keep
the channel open. The first foramen of the anterior and posterior roots, lateral to
the MC, is sought. The root is found, it is divided into four parts to initiate the
stimulation to pulses of 0.1 thousandth of a second to a frequency of 0.5 Hz and then
50 Hz, and then identify if we are stimulating motor or sensory fibers. In spasticity,
sensory fibers are hyperactive; In these cases, the most altered part for neurolysis
is chosen, preserving those that are in better condition. By not choosing to cut the
entire sensory root, it avoids the pain of deafferentation. In the Fig. 6a, we visualize
the medullary dura mater at the open L1 level, exposing the MC and the cauda equina.
We find the L1 sensory root and use a latex repair to separate the motor from the
sensory part ([Fig. 6b ]). Half of the fibers in the L1 dorsal root are cut without stimulation ([Fig. 6c ]). In sequence, we stimulated L2 roots with EMG, isolating the sensory part and separating
it into four parts. Again, we stimulate each segment to evaluate the degree of hyperactivity
and recorded the electrical patterns of the related muscles. The most injured segments
are sectioned.
Fig. 6 Intraoperative images showing the open dura mater with visualization of the medullary
cone and roots being stimulated during electromyography with bipolar configuration.
The root that has already been cut is separated from the others with a tape or vascular
shoelace, so as not to risk approaching them again ([Fig. 6d ]). After finding another root and separating again with repair ([Fig. 6d ]), we do a new stimulation and repeat the whole process ([Figs. 6e ] and [6f ]) until you approach the whole L2 S2 segment or, depending on the case, those in
which the patient has more functional impairment.
The stimulation of nerve roots intraoperatively assesses the functional integrity
of the nerve, since it is visually impossible for the surgeon to make this differentiation.
As each root is stimulated, a motor response in the musculature of the corresponding
segment is perceived, and the information of the action potential is received in the
software that analyzes and records the stimuli corresponding to each root. In [Fig. 7 ], we observe a graphic example of stimulation. The motor latency was 7 seconds and
the sensory was 9 seconds. It shows that the L3 root is being stimulated and that
the action potential has a late peak to the Yellow Line, which marks the division
between motor and sensory, confirming it to be a sensory root. In the left column
(in blue) the stimulations are separated into the four parts of the root. It is noted
that parts 2 and 3 are more hyperactive. Therefore, these parts can be sectioned,
preserving parts 1 and 4.
Fig. 7 Stimulation of the L3 segment. We visualize that the wave pulse is to the right of
the yellow line and denotes the separation between a motor or sensory impulse. The
left side (blue) shows the division of the four parts, evidencing that parts 2 and
3 of the L3 root are hyperactive and should be sectioned.
The advantages of this technique consist in the reduction of spinal deformity, especially
in children, if compared with the extensive laminectomy in the traditional technique,
improvement of spasticity in the hip, due to the section in the first lumbar dorsal
root, reduced surgical access with lower muscular manipulation, and, consequently,
less postoperative pain and early resumption of rehabilitation activities. However,
the risks are shared with other procedures such as paraplegia, paralytic bladder,
sexual impotence and sensitivity deficit.
A study that included 95 patients treated with SDR in childhood, and accompanied them
for periods varying from 20 to 28 years, showed that 91% of the patients submitted
to surgery reported that the surgical treatment positively impacted the quality of
life. In 42% of the patients, there was improvement in ambulation, 88% would recommend
the procedure for other patients and there were no late complications for these patients.[39 ]
Daunter et al selected patients with CP who underwent SDR in infancy (before 10 years
old) and compared them with an unoperated control group. They concluded that the SDR
group presented less pain, fatigue and functional decline compared with the nonsurgical
group.[40 ]
The SDR technique by single-segment laminoplasty provides a less invasive approach,
and the incidence of scoliosis after this approach is comparable with the natural
history of children accompanied as outpatients.[41 ]
Conclusion
Selective dorsal rhizotomy is efficient in the treatment of severe spasticity. It
is a surgery with low morbidity, and electrophysiological stimulation has shown to
be efficient in the choice of root segments that should be safely sectioned. However,
for a successful treatment, the patient should be rigorously selected. In addition
to the functional improvement of the spastic patients, there is an expressive improvement
in the quality of life of the caregivers.
