Anatomical Surface Guided Techniques for Botulinum Toxin Injection in Spastic Cerebral Palsy Children

Abstract

Spasticity, a classical clinical manifestation of an upper motor neuron lesion, has been traditionally and physiologically defined as a velocity-dependent increase in muscle tone caused by the increased excitability of the muscle stretch reflex. Clinically, spasticity manifests as an increased resistance offered by muscles to passive stretching (lengthening) and is often associated with other commonly observed phenomena, such as clasp-knife phenomenon, increased tendon reflexes, clonus, and flexor and extensor spasms. If spasticity is not treated leads to abnormal posture, contracture, and painful deformities. This chapter will cover the botulinum toxin used in the management of spasticity while using the surface anatomy of upper and lower limb muscles. This will help enhance the use of this technique even in remotest setups where USG and EMG facilities are unavailable.

1. Introduction

Cerebral Palsy (CP) is a combined disorder of movement, posture, and motor function often complicated or associated with various sensory, neurological, musculoskeletal complications, and behavioral problems. Nowadays, spastic CP is the most common type (more than 2/3rd cases) followed by dyskinetic, hypotonic, and ataxic. In spastic CP, diplegia is the most common (>50%), followed by quadriplegia, hemiplegia, and monoplegia [1]. Spasticity is commonly managed by stepped-up management protocol beginning with the more conservative options (exercises, physical modalities, occupation therapy, and orthoses) followed by oral medications (like baclofen, tizanidine, dantrolene, and tolperisone) and various surgical options for relatively older children at last resort, where stiffness and progressive deformities continue to hamper rehabilitative treatment. Chemodenervation by botulinum toxin-A (BTx-A) decreases spasticity by denervating the muscle by inhibiting acetylcholine release from the neuromuscular junction [2]. It has a relatively focal, reversible effect with a wide safety margin. This BTx-A denervation temporarily reduces muscle tone and provides an opportunity to effect changes in motor learning and cortical motor organization [3].

BTx-A injection in the lower limb muscles may help in reducing spasticity, increase in range of motion, and improvement in gait pattern [4, 5]. BTx-A injection in the upper limb may also have favorable effects on decreasing the spasticity or resistance to passive movement of the spastic wrist and fingers and on self-care as an adjunct to other basic conservative means described above [6, 7].

In this chapter, we will be discussing surface anatomical or landmark-guided injection techniques in children with spastic cerebral palsy.

Most of the spastic upper and lower limb muscles can be injected by surface or anatomical landmark-guided technique. However, in the case of obese children or distorted anatomy, multiple times botulinum toxin injection ultrasound (US) guidance may be useful nowadays.

For surface anatomy or landmark-guided BTx-A injections, a common spastic pattern affecting the muscle and dynamic function is identified. In upper limb spasticity, the child has usually various combinations of isolated adducted and internally rotated shoulder, flexed elbow, forearm pronation, flexed wrist and finger, and thumb in palm posturing. Muscle injected commonly are pectoralis major, subscapularis, biceps, brachialis, brachioradialis, pronator teres & pronator quadratus, flexor carpi radialis & ulnaris, flexor pollicis longus, flexor digitorum superficialis, and profundus, adductor pollicis, opponents pollicis, and flexor pollicis Brevis. Whereas in the lower limb, any combination of hip in flexion, adduction, knee in flexion, ankle in equinus/equinovarus, flexed toes, and stiff knee on dynamic or static assessment.

For practical purposes, the injection site in the center of maximum muscle bulk usually lies in the midpoint of muscle or some cases between proximal one-third to the midpoint of muscle bulk. So, surface anatomical landmarks are midpoint or at maximum bulk and if another injection point is required, then a few centimeters proximal to this point depending upon the age and muscle involved.

1.1 Theory pearls

At muscle bulk there lies the end plate zone. Many past animal research has shown that injections close to these motor end plates are more efficacious [8] and in some muscles, it is also scattered throughout (sartorius, gracilis) [9]. As we cannot localize end plates by surface anatomy or clinical palpation. It is easy and practical to use surface/landmark-guided injection.

So, our target should be to identify surface landmarks, insert the needle in the belly (preferably midpoint and mid-thickness) of the muscle, and then gently stretch passively, needle movement is best appreciated if it is in the desired muscle. One should also ensure nil or minimal movement of the needle, while stretching other nearby/overlapping muscles or muscle slips.

In a few situations, we may have to use US guidance or US visualization for muscle identification and depth, then surface anatomical guidance may become more easier and precise. This is particularly required for deep muscles and relatively smaller muscles.

Otherwise, it might inject into undesired or neighboring muscles. As for any injection technique, we must ensure needle tips should not be in blood vessels or injure neural tissues.

Here, only commonly done lower limb and upper limb muscle is described in this chapter from proximal to distal joints/muscle and ease of doing the injection, which are as follows-.

2. Lower limb muscles

2.1 Iliopsoas

The child should lie supine on the edge of the table. Mark the inguinal ligament, palpate the femoral pulse, and now mark the femoral pulse line at the inguinal ligament. The midpoint of these two (obviously lateral to the femoral pulse) just below the inguinal ligament is the entry point of the needle. Passive extension of the hip on the edge of the table will show the movement of the needle, and adjust the depth accordingly. Prior US evaluation is better. For injection to be a more effective translumbar approach is required, authors do not advocate this injection without image guidance (Figure 1).

Figure 1.

Iliopsoas (IP): ASIS: Anterior superior iliac spine, IL- inguinal ligament, FA- line of femoral artery pulsation. Plus sign denotes the injection point.

2.2 Adductor longus (AL)

The child should be in a supine position with hip and knee flexed. The spastic adductor will stand prominent in most cases in the anteromedial proximal thigh, while doing hip abduction. One can hold the muscle between the nondominant thumb and index finger and insert the needle at about proximal one-fifth to one-fourth of the muscle (Figures 2a and b).

Figure 2.

a. Adductor longus(AL): red line denotes the prominence area of AL. b. Adductor longus(AL): plus denote vertical injection point, while holding the muscle in between fingers.

2.3 Adductor magnus (AM)

If we want to inject (less practiced). The position will be the same as AL. At about proximal one-third of the medial thigh, just medial to gracilis. (Bony landmark 3–4 inch anteromedial to ischial tuberosity). The US is helpful because the needle may be in the gracilis or a medial hamstring if the needle enters a more anterior or posterior. Sometimes it may be deeper. Needle movement with passive abduction in knee extension/flexion confirms needle entry in gracilis or adductors (Figure 3).

Figure 3.

Adductor Magnus (AM): in medial thigh inferomedial to AL point, at proximal one-third thigh plus demarcate injection point.

2.4 Semitendinosus (ST)

(Authors preferred approach) Patient lying prone with knee slightly flexed (already in most spastic patients) allowing terminal 30–40-degree extension or child lying supine with hip and knee 90-degree flexion. Now, the knee is extended as much as possible to mark and palpate the muscle. Now palpate the muscle at the junction of the proximal one-third distal and half of the thigh. It lies on the line joining from ischial tuberosity to medial post knee crease (tendon of semimembranosus) can be appreciated here. Here, we find the maximum bulk. Here, another point of injection 2–4 cm proximal to the previous injection point may be taken.

2.5 Semimembranous (SM)

Position and line same as semitendinosus. At the junction of proximal two-thirds and distal one-third, ST will be standing out prominently. Just medial to the prominent ST tendon. The injection is given. Passive extension of the hip in both positions helps in appreciating the good needle movement, thus confirming the muscle.

2.6 Biceps femoris (BF)

Same position as ST/SM. But the line changed. Draw a line between ischial tuberosity to lateral post knee crease (BF tendon is palpable). The midpoint of this line will be the target of needle entry. Palpate the muscle here by passive extension flexion of the knee. If one is confident, enter at the above-described midpoint for an injection. Caution should be taken for entry either medial or lateral to the tendon, the muscle may be deeper or even it may be congenitally absent. The needle movement must be appreciated. The US helps locate in case of difficulty (common with beginners) (Figure 4).

Figure 4.

Hamstring muscles: SM- semimembranosus, ST- semitendinosus, BF- biceps femoris. L1- line one joining ischial tuberosity to medial posterior knee crease. L2- line two joining ischial tuberosity to lateral posterior knee crease. Plus denotes the points of injection of mentioned muscle.

2.7 Rectus femoris (RF)

Make the child supine and draw a vertical line from the ant superior iliac spine to the center of the patella. The injection point is in the middle of it. It lies most superficial, just have to pass skin and subcutaneous tissue. So, adjust the depth accordingly. More deep needle insertion will go in vastus intermedius (Figure 5).

Figure 5.

Rectus femoris(RF): plus mark denotes injection point, which is middle of the line, joining ASIS and patella center.

2.8 Gastrocnemius (GN)

The child should lie prone. Transverse mark the area/point where maximum calf bulk is there. Mark a vertical midline to differentiate the medial and lateral head. Now mark the lateral line corresponding fibular head and the medial line on the most anteromedial border of the tibia. The midpoint of the medial line and midline is the entry point of the medial gastrocnemius and the midpoint of the lateral line and the midline is the entry point of the lateral gastrocnemius. It is a very superficial muscle (needle vertical entry depth is only 0.5–0.8 cm in most children). Passive dorsiflexion beautifully elicits needle movement in both heads (Figure 6).

Figure 6.

Gastrocnemius(GN): line marked at the area of maximum calf bulk. Plus denotes the entry of the needle for MG (medial head gastrocnemius) & LG (lateral head gastrocnemius).

2.9 Soleus

The patient should lie prone, and look at the midpoint of the back of the leg. Between post knee crease and post upper margin of the calcaneus, where gastrocnemius lower margin is visible and palpable. One can inject just below the lower margin of the gastrocnemius. After needle insertion flexes the knee to 90 degrees (to avoid gastrocnemius action), and passively moves the ankle, good movement of the needle helps in correctly identifying the soleus. If the needle movement is less, may imply going deep into the flexor digitorum or tibialis posterior (Figure 7).

Figure 7.

Soleus(sol): plus denotes injection for sol at the lower margin of GN.

2.10 Tibialis posterior (TP)

Although we recommend US guidance for it, it may be injected with practice. The child should lie supine with hip and knee slightly flexed and externally rotated, so that the medial leg face upwards, Now just distal to the hallway of the leg, insert the needle just (0.5 to 1 cm) behind the tibia from the medial leg and advance it parallel to the tibia, first flexor digitorum Longus is traversed then will reach the tibialis posterior. Passive toe extension and flexion initially the passive eversion at the ankle will confirm the needle position.

2.11 Flexor digitorum Longus (FDL)

Positioning same as above (TP). In the mid-leg, this muscle lies anterior to soleus and posterior to tibia. Insert the needle at mid-leg just posterior to the tibia from the medial side and advance laterally parallel to the posterior tibia, It is the first muscle in the needle path, needle movement is appreciated well if we passively extend the 2nd to 4th toe. The needle will go in the tibialis posterior if we go more lateral. So, we can inject both FDL and TP in one go of a needle. If needle entry is more posterior, one can be mistakenly injected into the soleus (Figure 8).

Figure 8.

Tibialis posterior (TP) & flexor digitorum longus (FDL): line is at the medial tibial border, plus is an entry point for TP& FDL injection (just posterior to the mid-tibia).

2.12 Flexor hallucis longus (FHL)

The child should lie in a prone position, feet preferably hanging out from the bed. As we know this muscle crosses laterally to the medial from the upper two-third of the leg to the lower leg. At about proximal three-fourth and distal one-fourth junction of the leg just anterior to tendon Achilles tendon, one may insert the needle here and angle it toward laterally (aiming obliquely toward fibula), on passive extension of great toe, the needle should tilt/move. Adjust the depth accordingly. Prior US scans or guidance are helpful (Figure 9).

Figure 9.

Flexor hallucis longus (FHL): the line represents the length of the leg (post knee crease to tendo-achilles insertion), plus at the distal one-fourth anterior to tendon Achilles is injection point.

3. Upper limb muscles

3.1 Pectoralis major (PM)

Abduction of the arm to make it easily visible pectoralis. Hold it between your thumb and fingers. Then insert the needle, and try to give an injection from the single insertion in its upper, middle, and lower part by going tangentially. Take precaution to not go more medial and steep in very lean and thin children to avoid pneumothorax (Figure 10).

Figure 10.

Pectoralis major (PM): fingers elevating PM from anterior axilla, plus denotes entry point of a needle. Arrows depicting needle directions.

3.2 Subscapularis (SS)

Place the child supine. This muscle lies anterior to the scapula. So, mark the medial border of the scapula. At the proximal two-thirds and distal one-third junction of the medial border, the needle is inserted after slightly pushing the scapula posteriorly. The needle should advance laterally parallel to the scapular spine. Do not advance the needle anterior to avoid any pneumothorax. Once the needle reaches some distance, preferably near or less near to the center of the scapula. Somewhat needle movement may be appreciated if the arm is moved in external rotation (Figure 11).

Figure 11.

Subscapularis (SS): plus at medial scapular border showing entry point for SS and arrow showing the direction of the needle.

3.3 Biceps

Child supine or sitting, arm by the side of the body, in elbow slightly flexed with the forearm in full supination. Palpate the anterior acromion point. Draw a line from the mid-elbow flexion crease (biceps tendon) and anterior acromion. The midpoint of this line corresponds to the center of the biceps belly. Muscle positioning may seem more medially in severe upper limb spasticity, such as adducted and internally rotated shoulder, so always take care of rotations and positioning. Hold the biceps between the nondominant thumb and index finger. Inject at this point. Passive slight extension and flexion will elicit good needle movement (Figure 12).

Figure 12.

Biceps: plus sign denotes the mid-muscle belly of the biceps as the injection point.

3.4 Brachialis (Br)

Positioning as for Biceps, mark the proximal two-thirds and distal one-third junction. At this point, find the place between the lateral border of the biceps and the lateral head of the triceps. Repeated supination and pronation will help in finding out the entry point, which is the first point/groove, where there is no biceps movement seen. Insert the needle at this point and push it further medically parallel to the transverse plane (toward the humerus). Pay attention not to go posterior to avoid entering in triceps. With the forearm in pronation passively gently extend flex the elbow a bit eliciting good needle movement (Figures 13a and b).

Figure 13.

a. Brachialis palpation: thumb in between lateral border of biceps and triceps. b. Brachialis (Br): B- biceps, T- lateral head of triceps, plus denotes injection entry point between B and T gap.

3.5 Brachioradialis (BR)

Supine position or cooperative child may be sitting with elbow 90 degrees flexed forearm in the mid-prone position. Now, keep the thumb in the antecubital fossa and index finger laterally to hold the muscle belly of brachioradialis between both fingers. At half to one inch distal to elbow crease, Insert the needle vertically down to reach a mid-depth of brachioradialis. Beware of posterior needle advancement, otherwise may inject extensor tendons. Passive elbow extension may show needle movement (Figure 14).

Figure 14.

Brachioradialis: line represents elbow flexor crease, forearm mid-prone, plus denotes injection for BR.

3.6 Pronator teres (PT)

The child should be supine or sitting as per convenience and cooperation with the forearm in supine. Take the midpoint of the elbow flexor crease and also mark the lateral and medial points. Now, bisect the medial and mid-elbow crease points. Now, mark a point 1–2 cm distal to this point (medial one-fourth). Now place the index finger in the antecubital fossa, just medial to the index finger is pronator teres at the final mark point. Now, try to stabilize PT with the index finger and thumb, and confirm it by doing prono-supination. Now, insert the needle into it and again reconfirm the needle movement. If one is more medial and distal might inject into flexor carpi radialis, sometimes into flexor digitorum superficialis (Figure 15).

Figure 15.

Pronator teres (PT): A & B – medial & lateral elbow flexor crease, C – midpoint of A&B, D- the midpoint of A& C (junction of medial one-fourth and lateral three-fourth of elbow flexor crease).

3.7 Flexor carpi radialis (FCR)

Positioning same as PT. Find out the apex of the cubital fossa. It is the point where the medial border of BR and lateral border of PT meet. Keep your index finger here. Palpate and try holding it between your thumb. Reconfirm it with the PT method by going 2–3 cm distal to the PT injection point. Good needle movement is appreciated by doing wrist radial-ulnar deviation and gentle passive extension (Figure 16).

Figure 16.

Flexor carpi radialis(FCR): A, B, C, D – as stated above in Figure 15. Distal plus sign denotes FCR injection point, proximal (left one) marked for PT.

3.8 Flexor digitorum superficialis (FDS)

Draw the first line between the mid-elbow flexor crease to the mid-wrist crease, second line from the medial epicondyle to the pisiform bone. Select the middle one-third between these two lines and make a rectangular box (as in Figure 17). Then, again divide this rectangle (with line 3) into equal medial and lateral halves. Now, 2nd finger FDS is more superficial at/near the distal part of 3rd line, 3rd FDS at the proximal part of 3rd line. 4th FDS and 5th FDS falls near just medial to 2nd line. 4th FDS superomedial to 3rd FDS and 5th FDS infero-medial to 2nd FDS. Avoid going near or crossing the first line laterally to avoid inadvertent injury to the neurovascular bundle. So, we should focus on the medial rectangle. This is the author’s practice method based on adult cadavers as described by Bickerton LE et al. [10].

Figure 17.

Flexor digitorum superficialis(FDS): L1- the line between the mid-elbow flexor crease to the mid-wrist crease. L2- medial epicondyle to pisiform bone. The central big rectangle represents the middle one-third of the medial forearm. L3- equally divide this rectangle into equal medial and lateral half. s2- 2nd finger FDS, s3- 3rd FDS, s4- 4th FDS, s5- 5th FDS. Plus at s2, s3, s4, & s5 denoted vertical entry point for respective FDS slips.

3.9 Flexor digitorum profundus (FDP)

The child may be sitting on a chair with the elbow supported on the table or a child lying supine arm on the side of the body in some abduction. Elbow should be completely flexed, forearm in the mid-prone position. Make a line proximally from the olecranon to the distal medial wrist crease (line 1). The needle entry point is the needle entry point in the proximal one-third to the distal two-thirds junction of the forearm, just anterior to the ulnar shaft or midpoint between the ulnar shaft and line 1. Here, it traverses through flexor carpi ulnaris. So, we are more distal. We may inject it into FCU. So, inject between proximal one-fourth to proximal one-third. Passive extension of distal interphalangeal (DIP) joints will elicit the best needle movement. Individual fascicles may be injected with expertise and US guidance (Figure 18).

Figure 18.

Flexor digitorum Profundus (FDP): L1- line from olecranon medial wrist crease. US- line at ulnar shaft. Plus denotes needle entry point through the midpoint between the ulnar shaft and L 1 in proximal one-third to the distal two-thirds junction of the forearm.

3.10 Flexor carpi ulnaris (FCU)

The child should lie supine or sitting with the dorsal forearm resting on the table in full supination. In the middle of the medial forearm, try to hold the muscle with fingers near/anterior to the ulnar border. Gentle wrist extension -flexion and radial-ulnar deviation should result in good needle movement. While finger flexion-extension should not show needle movement. Adjust the needle if one has gone anteriorly into FDS or deep into FDP (Figure 19).

Figure 19.

Flexor carpi Ulnaris (FCU): line represents ulnar border. Plus denotes an injection entry point for FCU in the middle of the medial forearm. Arrow showing the direction of the needle.

3.11 Flexor pollicis longus (FPL)

Position supine or sitting. Forearm in full supination. Draw a line from the middle of the elbow flexor crease to the lateral wrist flexor crease. The middle point of this line is the area of interest. Also, start palpating the radial artery from distal to proximal. In the midpoint of this line, just lateral to radial artery pulse (almost lost at this point) is the needle entry point straight vertically downwards in mid-depth (skin to radius bone). Do not forget to aspirate, as the radial artery is very close. Passive extension-flexion of the thumb distally will help in the localization of FPL and movement of the needle confirms its placement in FPL (Figure 20).

Figure 20.

Flexor pollicis longus (FPL): L1- line joining medial & lateral elbow flexor crease. L2 a line from MID PINT OF L1 to lat wrist flexor crease. Small plus (on line L2) denotes the absence of a palpable radial pulse. Larger plus lateral to it is a vertical needle entry point for FPL.

3.12 Opponens pollicis

Supinated forearm means Palm facing up. Thumb adducted or thumb in the palm. Mark the midpoint of the thumb metacarpal. Gently aside the abductor pollicis brevis medially and insert the needle just medial to the bone from this midpoint and remain close to the bone. Gently move the thumb laterally (opposite action of opponens) to confirm needle movement and injection placement (Figure 21).

Figure 21.

Opponens pollicis: plus denotes the entry point for OP.

3.13 Adductor pollicis (AP)

Forearm pronated, palm facing down, thumb as much laterally as possible to make the dorsal first web as prominent as possible. Place one finger from the palm side and one from the dorsal side in between the first and second metacarpal to feel AP. Now, insert the needle in the center of palpated AP from the dorsal 1st web space (center), and adjust the needle depth accordingly (Figure 22).

Figure 22.

Adductor pollicis (AP): plus denotes the injection point.

3.14 Lumbricals

These are small muscles, that may be injected with sound anatomical knowledge, surface landmarks, or the US-guided. For the first lumbrical, the point marks the distal one-third and proximal two-thirds junction of the second metacarpal (radial side). At this, it lies just radial to this point. First, palpate the muscle by doing metacarpal flexion with distal joints in extension. Once palpated, inject at this point. Similarly, all others can be injected (Figure 23).

Figure 23.

Lumbricals: plus denotes the entry point for the first lumbrical (1st lumbrical), line represents the radial border of the 1st index metacarpal.