SPASTICITY

Spasticity is one of the most common sequels of neurologic diseases. In most patients, spasticity is useful in compensating for lost motor strength. However, in a significant number of patients it may become harmful and lead to further functional losses. When not controllable by physical therapy and medications, excessive spasticity can benefit from neurostimulation, intrathecal Baclofen pharmacotherapy, botulinum toxin injections, or selective ablative surgical procedures. Lesioning can be performed at the level of the peripheral nerves, spinal roots, spinal cord, or the dorsal root entry zone (DREZ). Here, only selective procedures in the spinal roots, spinal cord, and DREZ will be described.

POSTERIOR RHIZOTOMIES
After Sherrington demonstrated in 1898 that decerebrate rigidity in an animal model was abolished by section of the dorsal roots (that is, by interruption of the afferent input to the monosynaptic stretch and polysynaptic withdrawal reflexes), posterior rhizotomy for the modification of spasticity was first performed by Foerster in 1908. Its undesired effects on sensory and sphincter function have limited its application in the past. To minimize these disadvantages, several authors in the 1960s and 1970s attempted to develop more selective operations, especially for the treatment of children with cerebral palsy.
Posterior Selective Rhizotomy
To reduce the sensory side-effects of the original Foerster method, Gros and coworkers introduced a technical modification that consisted of sparing one rootlet of the five of each root, from L1 to S1. On similar principles, Ouaknine, a pupil of Gros, developed a microsurgical technique that consisted of resecting one third to two thirds of each group of rootlets of all the posterior roots from L1 to S1.
Sectorial Posterior Rhizotomy
In an attempt to reduce the side-effects of rhizotomy on postural tone in ambulatory patients, Gros and his pupils Privat and Frerebeau proposed a topographic selection of the rootlets to be sectioned. First, a preoperative assessment of spasticity useful for postural tone (abdominal muscles, quadriceps, gluteus medius) and spasticity harmful to the patient (hip flexors, adductors, hamstrings, and triceps surae) is conducted. Mapping of the evoked motor activity of the exposed rootlets, from L1 to S2, by direct electrostimulation of each posterior group of rootlets is then carried out, and the rootlets to be sectioned are determined according to the preoperative program.
Partial Posterior Rhizotomy
Fraioli and Guidetti reported on a procedure by which the dorsal half of each rootlet of the selected posterior roots is divided a few millimeters before its entrance into the posterolateral sulcus. The authors report good results without significant sensory deficit, the latter being explained by the fact that partial section leaves intact a large number of fibers of all types.
Functional Posterior Rhizotomy
The search for specially organized circuits responsible for spasticity led Fasano and associates to propose a new method called functional posterior rhizotomy. This method is based on bipolar intraoperative stimulation of the posterior rootlets and analysis of different types of EMG reflex responses. Responses characterized by a permanent tonic contraction, an after-discharge pattern, or a large spatial diffusion to distant muscle groups were considered to belong to disinhibited spinal circuits responsible for spasticity. Functional posterior rhizotomy—which was especially conceived for children with cerebral palsy— has also been used by other outstanding surgical teams, each one having brought its own technical modifications to the method. Adaptation of these methods is illustrated in Fig.1.

RESULTS OF POSTERIOR RHIZOTOMIES
The results of posterior rhizotomies in children with cerebral palsy—whatever the technical modality may be—have been recently reported in several publications. Briefly, these publications show that about 75% of the patients had nearly normal muscle tone at 1 year or more after surgery without spasticity limiting the residual voluntary movements of the limbs. After a serious and persisting physical therapy and rehabilitation program, most children demonstrated improved stability in sitting and/or increased efficiency in walking. It must be noted, however, that preexisting orthopedic deformities cannot be improved with this method.


	FIGURE.1 Lumbosacral posterior rhizotomy for children with cerebral palsy. The technique consists of performing a limited osteoplastic laminotomy using a power saw, in one single piece, from T11 to L1 (left). The laminae will be replaced at the end of the procedure and fixed with wires (right). The dorsal (and ventral) L1, L2, and L3 roots are identified by means of the muscular responses evoked by electrical stimulation performed intradurally just before entry into their dural sheaths. The dorsal sacral rootlets are recognized at their entrance into the dorsolateral sulcus of the conus medullaris. The landmark between S1 and S2 medullary segments is located approximately 30 mm from the exit of the tiny coccygeal root from the conus. The dorsal rootlets of S1, L5, and L4 are identified by their evoked motor responses. The sensory roots for bladder (S2–S3) can be identified by monitoring vesical pressure. Those for the anal sphincter (S3–S4) can be identified by rectomanometry (or simply using finger introduced into the patient’s rectum) or EMG recordings. Surface spinal cord SEP recordings from tibial nerve (L5–S1) and pudendal nerve (S1–S3) stimulation may also be helpful. For the surgery to be effective, a total amount of 60% of dorsal rootlets must be cut (with a different amount of rootlets cut according to the level and function of the roots involved). Also, the correspondence of the roots with the muscles having harmful spasticity or useful postural tone must be considered in determining the amount of rootlets to be cut; in most cases, L4 (which predominantly gives innervation to the quadriceps femoris) has to be preserved.

Longitudinal myelotomy, which was introduced by Bischof, was made more selective by Pourpre and later on by Laitinen. The method consists of a frontal separation between the posterior and anterior horns of the lumbosacral enlargement from T11 to S2 performed from inside the spinal cord after a posterior commisural incision that reaches the ependymal canal. In Laitinen’s series of 25 patients, 60% had complete relief of spasticity and 36% showed some residual spasticity in one or both legs. Within 1 year, some muscular tone returned in most patients but seldom produced troublesome spasticity. A harmful effect on bladder function was present in 27% of the patients. Longitudinal myelotomy is indicated only for spastic paraplegias with flexion spasms, when the patient has no residual useful motor control and no bladder and sexual function.

Selective posterior rhizotomy in the dorsal root entry zone (DREZ), referred to as micro-DREZotomy (MDT), was introduced in 1972 to treat intractable pain. Because of its inhibitory effects on muscular tone, it has been applied to patients with focalized hyperspasticity. This method attempts to selectively interrupt the small nociceptive and the large myotatic fibers (situated laterally and centrally, respectively), while sparing the large lemniscal fibers which are regrouped medially. It also enhances the inhibitory mechanisms of Lissauer’s tract and the dorsal horn (Fig.2 left). MDT, the technique of which has been described elsewhere, consists of microsurgical incisions that are 2 to 3 mm deep and at a 35° angle for the cervical level (Fig.2 right) and at a 45° angle for the lumbosacral level (Fig.3), followed by bipolar coagulations performed ventrolaterally at the entrance of the rootlets into the dorsolateral sulcus, along all the cord segments selected for operation. For patients with paraplegia, the L2–S5 segments are approached through a T11-L2 laminectomy, whereas for the hemiplegic upper limb, a C4–C7 hemilaminectomy with conservation of the spinous processes is sufficient to reach the C5–T1 segments. Identification of the cord levels related to the undesirable spastic mechanisms is achieved by studying the muscle responses to bipolar electrical stimulation of the anterior and/or posterior roots. The motor threshold for stimulation of anterior roots is one third that of the threshold for posterior roots. Then, the lateral aspect of the DREZ is exposed so that the microsurgical lesioning can be performed. Lesions are 2 to 3 mm in depth and are placed at 35 to 45° angles in the ventrolateral aspect of the sulcus all along the selected segments of the spinal cord. Intraoperative neurophysiological monitoring may be of some help for identifying cord levels, quantifying the extent of MDT, and avoiding impairing long fiber tracts.


	FIGURE.2 Micro-DREZotomy (MDT). Left, organization of fibers at the DREZ in humans. The large arrow shows the proposed extent of the MDT affecting the lateral and central bundles formed by the nociceptive and myotatic fibers, as well as the excitatory medial part of the Lissauer Tract and the upper layers of the dorsal horn. Right, principle behind the MDT technique. Example of the MDT at the cervical level through a right cervical hemilaminectomy (the procedure for the lumbosacral roots is the same). The right C6 posterior root has been retracted toward the inside to make the ventrolateral region of the DREZ accessible. The incision is performed into the dorsolateral sulcus using a small piece of razor blade (upper operative view). The incision is 2 to 3 mm deep and is made at a 35° angle (at a 45° angle for the lumbosacral level). Then microcoagulations are created with a very sharp and graduated bipolar microforceps down to the apex of the dorsal horn (lower operative view).	FIGURE.3 MDT technique at the lumbosacral level. Top left, exposure of the conus medullaris through a T11–L1 laminectomy. Bottom left, approach of the left dorsolateral sulcus. For this approach, the rootlets of the selected lumbosacral dorsal roots are displaced dorsally and medially to obtain proper access to the ventrolateral aspect of the DREZ. Right, the rootlets of the selected dorsal roots are retracted dorsomedially. They are subsequently held with a specially designed ball-tip microsucker, used as a small hook to gain access to the ventrolateral part of the DREZ. After the fine arachnoidal filaments sticking the rootlets together with the pia mater are divided with curved sharp microscissors (B), the main arteries running along the dorsolateral sulcus are dissected and preserved, while the smaller ones are coagulated with a sharp bipolar microforceps (F). Then, a continuous incision is performed using a microknife (K) made with a small piece of razor blade inserted within the striated jaws of a curved razor blade holder (K). The cut is—on average—at a 45° angle and to a depth of 2 mm. The surgical lesion is completed by doing microcoagulations under direct magnified vision, at a low intensity, inside the posterolateral sulcomyelotomy down to the apex of the dorsal horn. These microcoagulations are made by means of the special sharp bipolar forceps (F), insulated except for 5 mm at the tips and graduated every millimeter.

MDT is indicated in paraplegic patients, especially when they are bedridden as a result of disabling flexion spasms, and in hemiplegic patients with irreducible and/or painful hyperspasticity in the upper limb. MDT also can be used to treat neurogenic bladder with uninhibited detrusor contractions resulting in leakage of urine around a catheter.
To date, Sindou et. al. series has consisted of 45 patients with unilateral cervical (C5–T1) MDT for harmful spasticity in the upper limb, 121 patients with bilateral lumbosacral MDT (L2–S1 or S5) for disabling spasticity in the lower limbs, and 12 patients with bilateral sacral S2–S3 (S4) MDT for hyperactive neurogenic bladder only. Effects on muscular tone can be judged only after a 3-month follow-up. A “useful” effect on spasticity, allowing withdrawal of antispasmodic medications, was obtained in 78% of the patients with a spastic upper limb. A similarly useful effect was obtained in 75% of the patients with spasticity in the lower limbs. When spasms were present in paraplegic patients, they were suppressed or markedly decreased in 88% of the patients. When compared to patients with multiple sclerosis (75% with good results), the results were better in patients with spasticity (and spasms) caused by pure spinal cord lesions (80% with good results). The least improvement was observed in patients with spasticity resulting from cerebral lesions (60% with good results). Reduction in spasticity usually leads to a significant improvement in abnormal postures and articular limitations. This was achieved in about 90% of our patients.
For the hemiplegic upper limb, the increase in articular amplitude was most remarkable for the elbow and shoulder (when not “frozen”) and much more limited for the wrist and fingers, especially if there was retraction of the flexor muscles and no residual voluntary motor activity in the extensors. For the lower limb(s), with abnormal postures in flexion, the increase in amplitude of joint movement was very much dependent on the degree of the preoperative retractions.
When the post-MDT gains were deemed insufficient because of persistent joint limitations, complementary orthopedic surgery was indicated. With regard to the patients (n = 5) who had paraplegia with irreducible hyperextension, all were completely relieved. In the patients with some voluntary movements hidden behind spasticity, reduction in the hypertonia resulted in an improvement in voluntary motor activity. Fifty percent of the patients operated on for spasticity in the upper limb had better motor activity of the shoulder and arm, but only half of those with some preoperative distal motor function obtained additional hand prehension. Only 10% of the patients with spasticity in the lower limb(s) had significant motor improvement after surgery (because most patients in this group had no preoperative motor function). In these severely affected patients, the main benefit was better comfort, less pain, ability to resume physical therapy, and less dependence in daily life. Bladder capacity was significantly improved in 85% of the 38 patients who had a hyperactive neurogenic bladder with urine leakage around the catheter. The 32 patients who improved were those in whom the detrusor was not irreversibly fibrotic. Pain, when present, was in general favorably influenced.
MDT continually produced a marked decrease in sensation. Because most patients were in a precarious general and neurological state, death occurred in 5 patients (4%), resulting from respiratory problems in 4 and bed sores in 1. Two patients with multiple sclerosis (MS) presented with acute but transient increases in their preexisting neurological symptoms during the postoperative period. Two others had a new postoperative clinical manifestation of the disease. The last of the complications to be mentioned concerns a patient who was operated on at the cervical level and had a persistent motor deficit in the ipsilateral leg after surgery.
With rigorous selection of patients, MDT can be very effective in relieving pain and suppressing excessive spasticity. Good long-lasting relief of excess spasticity was achieved in 80% of our patients. As a result, MDT, sometimes combined with complementary orthopedic surgery, resulted in significant improvement in patient comfort and joint deformities, and even enhancement of residual voluntary motility hidden preoperatively behind hypertonicity.

Provided that the spasticity is mild and the dorsal columns are still functioning, spinal cord stimulation can be useful for treating spasticity from diseases affecting the spinal cord (e.g., MS or degenerative diseases such as Strumpell-Lorrain syndrome). A percutaneous trial before a definitive implantation may be useful.

Intrathecal baclofen administration is indicated for para- or tetraplegic patients with severe and diffuse spasticity, especially when spasticity has a spinal origin. Because of its reversibility, this method should be used before an ablative procedure is considered. But the range between excessive hypotonia with loss of strength and an insufficient effect is very narrow. An intrathecal test through a temporary access port can be useful when deciding if permanent implantation is indicated.

Neuroablative techniques are indicated for severe focalized spasticity in the limbs of paraplegic, tetraplegic, or hemiplegic patients. Neurotomies are preferred when spasticity is localized to muscle groups innervated by a small number of, or a single, peripheral nerve (or nerves). When spasticity affects an entire limb, MDT is preferred. Several types of neuroablative procedures can be combined in the treatment of one patient, if needed. Whatever the situation and the etiology may be, orthopedic surgery should be considered only after spasticity has been reduced by physical and pharmacological treatments first and, when necessary, by neurosurgical procedures. Guidelines for surgical indications are summarized in Fig.4. The general rule is to tailor individual treatments as much as possible to the patient’s particular problems.

Surgical indications depend on preoperative abilities, disabilities, and the eventual functional goals. As a means of guidance, it is adopted the six-group classification as defined by Abbott.
Independent Ambulatory Patients
In independent ambulatory patients, the goal is to improve efficiency and cosmetics in walking by eliminating as many abnormally responsive neural circuits as can be identified through functional posterior rhizotomy. Surgery is best performed as soon as possible after the child has demonstrated the ability to work with a therapist, usually between ages 3 and 7 years, and frequently must be done in conjunction with operations on tendons because of concomitant shortened muscles.
Ambulatory Patients Dependent on Assistance Devices
For ambulatory patients dependent on assistance devices (canes, crutches, rollators, walkers), the goal is to lessen that dependence. A child with poor trunk control or lack of protective reaction but with good underlying strength in the antigravity muscles can safely undergo a functional posterior rhizotomy. In children dependent on hypertonicity in the quadriceps to bear weight, a limited sectorial rhizotomy is preferable. For children who are in the process of developing ambulatory skill and need a temporary assistance device, it is important to delay surgery until they have perfected these skills.
Quadruped Crawlers
For quadruped crawlers (or bunny hoppers) the goal is to achieve assisted ambulation during mid-childhood to early adolescence. A functional posterior rhizotomy will decrease hypertonicity in the leg musculature and allow better limb alignment in the standing position for a child with adequate muscular strength. However, a child who exhibits quadriceps weakness can be considered for a sectorial posterior rhizotomy. Children in this group can present at a young age with progressive hip dislocation. The goal is to stop the progressive orthopedic deformity by using obturator neurotomy with adductor tenotomies or functional posterior rhizotomy.
Commando (or Belly) Crawlers
For commando (or belly) crawlers disabled by severe deficiencies in the postural control, the goal of posterior rhizotomy is only to improve functioning in the sitting position by increasing stability.
Totally Dependent Children
In totally dependent children with no locomotive abilities, the goals are to simply improve comfort and facilitate care. As with group 4 (commando [or belly] crawlers), the preferred treatment is posterior rhizotomy, but there is also a need for exploring the efficacy of intrathecal baclofen.
Children with Asymmetrical Spasticity
For asymmetrical spasticity, selective peripheral neurotomies must be considered, especially obturator and tibial for a spastic hip or foot, respectively. For upper limb spasticity, the MDT procedure and/or selective neurotomies of the flexor muscles of wrist and fingers can be considered.

Spasticity is usually a useful substitute for deficiencies in motor strength. Therefore, it must be preserved. Although it happens infrequently, it can lead to the harmful aggravation of a motor disability. When excessive spasticity is not sufficiently controlled by physical therapy and pharmacological agents, patients can consider surgery, especially neurosurgical procedures. By suppressing excessive spasticity, correcting abnormal postures, and relieving the frequently associated pain, surgery for spasticity allows physiotherapy to be resumed and sometimes results in the reappearance of, or improvement in, useful voluntary motility. When dealing with these patients, the surgeon must know the risks of the available treatments. To minimize those risks, the surgeon needs a strong anatomic, physiological, and chemical background, rigorous methods to assess and quantify the disorders, and the ability to work in a multidisciplinary team.