**3. Spasticity assessment**

The degree of affection, its evolution over time, and the response to the therapeutic options can be evaluated with the use of some scales. There are several widely used scales: Ashworth Scale (AS), Modified Ashworth Scale (MAS) and Gross Motor Function Classification System (GMFCS). They are formed of different points to construct ordinal scale that assess muscle tone. A higher score indicates a more intense spasticity [7].

Moreover, to comprehend correctly the information said before it is necessary to understand the meaning of two important concepts: spasticity and spasms. Spasticity is "hypertonia that is associated with one or both of the following signs: resistance to passive movement that increases with speed of stretch, or when the resistance to externally imposed movement rises rapidly above a threshold speed or joint angle" [8]. On the other hand, spasms can be defined as "episodes of involuntary motor contractions that occur following a lesion of the ascending motor pathway" [9]. It is important to mention that spasticity is detrimental to human health due to the miscommunication between the brain and the muscles, as a consequence those patients have a diminished quality of life. Spasms can be presented in long periods of time that is why problems in the musculoskeletal system can appear, affecting mobility and tone of posture.

Bryan Ashworth, in 1964, created a classification in which patients with multiple sclerosis could be graded in order of their clinical manifestations, starting to objectivize the knowledge of the pathology mentioned before [10]. Between the decades of 1960's to late 1980's the scale was used by doctors all over the world to help get a more accurate diagnose of spasticity, contributing to the progress of science in the field of neurology.

**Table 1** shows the classic Ashworth Scale that consist in five different types of categories that describe clinical manifestations of spasticity [11].

Furthermore, in 1987 Richard Bohannon's group added to the scale a category "1+" for a more accurate classification regarding clinical manifestations in patients with spasticity. Since then, the scientific community has been using this scale of measure to add a more specific diagnose in patients that present rigid upper limb due to its extension [12]. It is important to mention that both scales, Ashworth and Modified Ashworth, are useful in the detection of spasticity and can be helpful to objectivize the manifestations of spasticity.

In this image, it can be seen the modifications that Richard Bohannon added to the Ashworth Scale (**Table 2**) [13].

Richard Penn has published several articles concerning spasticity, and also is attributed as the creator of a scale that measures the frequency of spasms "Penn Spasm Frequency Scale (PSFS)".

**Table 3** shows the different categories of spasms over time to identify characteristics according to the clinical manifestations [14].


**Table 1.** *Ashworth scale.*


### **Table 2.**

*Modified Ashworth scale (MAS).*


#### **Table 3.**

*Penn spasm frequency score (PSFS).*

#### **4. Treatment**

The objective of the different pharmacological and surgical treatment options is to compensate the excitation/inhibition imbalance that occurs in the motoneurons of the ventral horn, the common final pathway for motor control. When possible, the underlying cause (e.g., tumor, abscess) that could be generated this imbalance should be eliminated. It is important to say that spasticity does not always require specific treatment. In many cases, spasticity can be helpful in maintaining balance and compensate for loss of motor power. Thus, spasticity should be treated when excess muscle tone leads to further functional disability, impaired locomotion, causes deformities, or induces chronic pain [5].

The different treatment options can be classified according to the location (focal vs. general) and duration (temporary vs. permanent) of their therapeutic effect. The choice of a treatment is made according to the severity and extent of spasticity and is adjusted according to the response and evolution of each patient. In general, surgical treatment is considered a second-line option, for patients with non-satisfactory response with drugs and physical therapy. Neurosurgical treatment options are divided into neuroablative and neuromodulatory procedures. The latter allow chemical or electrical regulation in the functioning of the neural circuits involved in spasticity. Importantly, such neuromodulation is characteristically adjustable and reversible. Ablative procedures are fixed and non-reversible. However, they still constitute a viable option for many patients, especially in those circumstances in which the use of neuromodulation equipment is not available. **Figure 1** shows a general algorithm for the treatment of a patient with spasticity from its initial assessment to management with lesioning procedures. This algorithm is only a general guide, and in each patient the treatment should be individualized in the context of a multidisciplinary management.

*Neurosurgical Spasticity Treatment: From Lesion to Neuromodulation Procedures DOI: http://dx.doi.org/10.5772/intechopen.96054*

#### **Figure 1.**

*General purpose algorithm for the treatment of spastic patients.*

#### **4.1 Ablative treatment**

This treatment modality implies the realization of some injury in certain levels of the nervous system that participate in the motor function in order to counteract spasticity. These lesions include selective neurotomies, rhizotomies, DREZotomies, myelotomies, and supramedular lesions. These procedures should be performed in such a way as to reduce excess muscle tone, but preserving residual sensorimotor functions and useful muscle tone. In cases of refractory spasticity, including paraplegic, hemiplegic or tetraplegic patients, the evolution and severity of the spasticity may require neuroablative management. In these cases, the injury procedure must be selective, and will be chosen considering the location of the spasticity (**Figure 1**). The characteristics of the most important and useful injuries will be reviewed below.

#### *4.1.1 Selective neurotomy*

Peripheral neurotomy was first introduced by Lorenz in 1887 for hip spasticity and by Stoffel in 1912 for spasticity in the foot [15]. This procedure consists of selectively identifying and injuring one motor nerve bundle that supply the spastic muscles. The goal of selective neurotomy is to inhibit the segmental reflex arc and thus limit the level of muscle spasticity. Selective neurotomy is indicated in cases of localized spasticity in a single or a few muscle groups, both in cases of focal or multifocal spasticity. The target nerves are selected according to the spastic region affected. Examples include lower subscapular nerve injury for spastic shoulder, median nerve injury for pronation spasticity of the upper limb, ulnar neurotomy for spastic wrist flexion with ulnar deviation, obturator nerve lesion in case of hip adduction spasticity, sciatic nerve for knee flexion spasticity and tibial neurotomy for equinus or equinovarus spastic foot [16].

The evaluation prior to neurotomy should include nerve blocks with a reversible agent such as botulinum toxin. These blocks allow us to observe a therapeutic effect previous to neurotomy and to evaluate its usefulness and acceptance. The injury must be performed with intraoperative electrophysiological monitoring of the nerve to be injured and must include 50–80% of the spastic muscle fibers to expect an effective result [5]. The most relevant long-term complications of the neurotomies are allodynia and neuropathic pain. To reduce the probability of the appearance of these adverse effects, it is important to identify and try to avoid sensory fibers during the procedure [17].

#### *4.1.2 Selective dorsal rhizotomy*

Sir Charles Sherrington, in 1898, showed that stiffness could be abolished by dorsal rhizotomy in a feline model with midbrain transection [18]. With this background, Otfrid Foerester, in 1913, reported the first dorsal rhizotomy for the management of lower limb spasticity in patients with cerebral palsy [19]. Rhizotomy consists of the selective section of the dorsal roots of the spinal nerve at a specific medullary level. It is thought that its effect is due to the reduction of the afferent information of the *Ia* fibers of the spastic muscle, which would produce a decrease in the excitatory input, and an increase in the inhibitory activity of the interneurons, to the alpha motoneurons [18, 19]. Dorsal rhizotomy is indicated in patients with diffuse or regional spasticity, in patients with spasticity in one or two limbs. There is no consensus on the precise selection criteria, but it is most frequently performed in paraplegic patients with spasticity in the lower extremities, however, it has also been performed successfully in the cervical region in patients with spasticity in the upper extremities [20, 21].

The procedure for the lower extremities is usually performed on the posterior roots of L1-S2 levels, exposed with a laminectomy or laminoplasty. For spasticity of the upper extremities, rhizotomy has been described from C1-C3 levels, not sectioning dorsal root of C4 to avoid affecting the diagrammatic function [20, 21]. Similar to neurotomies, it is important to perform intraoperative electrophysiological mapping to identify the roots that contribute to spasticity. In cases of pediatric

#### *Neurosurgical Spasticity Treatment: From Lesion to Neuromodulation Procedures DOI: http://dx.doi.org/10.5772/intechopen.96054*

cerebral palsy, it has been observed that the patients with the greatest improvement are those between 4 and 7 years old and have a preoperative gross motor function measure test (GMFM-88) between 65–85% [22]. The most important side effects of this procedure are impaired sensation, sphincter dysfunction, cerebrospinal fluid fistula, and chronic low back pain [17]. Techniques with more limited and selective lesions have been tried to improve the results and reduce the probability of the appearance of side effects [7].
