CEREBRAL PALSY

Cerebral palsy (CP) is a lifelong condition that affects the individual, family, and immediate community. It is a childhood condition in which there is a motor disability (palsy) caused by a static, non-progressive lesion in the brain.

The causative event has to occur in early childhood, usually defined as less than 2 years of age. Children with CP have a condition that is stable and non- progressive; therefore, they are in most ways normal children with special needs.

The goal of having a concept of motor control is to help in treatment of children with motor control problems. When considering individual pathological problems, the neurological aspects of the motor impairments can be separated into abnormalities of the three subsystems of motor control. These subsystems are muscle tone, motor planning, and balance.The variety of abnormalities in these three subsystems leads to almost all the motor problems in children with CP.

In my succeeding blogs, I will be writing about Cerebral palsy and problems related to it. In this blog i would like to give a brief information about the medications like BOTOX (Botlinum toxin), Phenol and local anesthetics in controlling SPASTICITY which is a tonal abnormality.

TONE :

TONE is defined as the resistance of muscle to passive elongation or stretch when an individual attempts muscle relaxation. It is due to a. physical inertia; b. intrinsic mechanical-elastic stiffness of muscle and connective tissues and c. reflex muscle contraction. Disorders of Muscle Tone: Tonal abnormalities are categorized as hypertonia (increased above normal resting levels), hypotonia (decreased below normal resting levels) or dystonia (impaired or disordered tonicity).

Spasticity:  Spasticity is the most common presentation of all neurological alterations in children with CP. It is a hypertonic motor disorder characterized by velocity-dependent resistance to passive stretch. Symptoms such as clonus, hyperactive tendon reflexes, and spasms are included within the umbrella term ‘spasticity’. It occurs as a part of UPPER MOTOR NEURON (UMN) syndrome as injury to the pyramidal tracts (corticospinal pathways). The signs and symptoms of UMN syndrome includes:

Measuring Muscle Tone:

A. Clinical measures : Range of motion, Modified Ashworth Scale , Tardieu Scale

Modified Ashworth Scale:

00 Hypotonia

0 Normal tone, no increase in tone

1 Slight increase in tone manifested by a slight catch and release or minimal increased resistance to joint range of motion.

1+ Slight increase in tone manifested by a slight catch and minimal increased resistance to joint range of motion for more than half the joint range.

2 More marked increase of tone through most of the whole joint range, but the affected joint is easily moved.

3 Considerable increase in muscle tone; passive movement difficult but possible

4 Affected joint is stiff and cannot be moved

B. Mechanical instruments: The pendulum test

C. Electrophysiological measures: The H reflex, Vibration inhibition index

D. Functional measures: Upper extremity function, Gait.

EFFECTS OF SPASTICITY

Positive effects

Treatment methods

•Physiotherapy: Positioning, Exercises, Stretching,Neurofacilitation

• Electrostimulation.

•Splinting & Casting.

•Oral medications: Baclofen, Diazepam, Clonazepam, Dantrolene, Tizanidine.

•Intrathecal medications: Baclofen, Morphine, Clonidine.

•Neuromuscular blocks: Local anesthetics, Phenol, Botulinum toxin.

•Orthopedic surgery.

•Selective dorsal rhizotomy.

                                            Neuromuscular Blocking Agents Local Anesthetics,  Phenol,  Botulinum Toxin

§Local anesthetics: 

• These block nerve conduction by changing membrane permeability to sodium ions. They affect both sensory and motor function in the area innervated by the nerve. This effect is completely reversible and causes no structural damage to the nerve.
• The effect starts within 3-15 minutes after the injection and lasts from 45 minutes to 8-12 hours depending on the type of drug used. Median nerve in the upper extremity and many nerves in the lower extremity are available for local anesthetic blocks. (like; Tibial, Obturator, Femoral ,Sciatic blocks).
• Local anesthetic blocks may be used as a diagnostic tool to differentiate spasticity from contracture and to predict functional changes with long term therapy.

Advantages of local anesthetic blocks:

• Reversible short duration effect.
• Relatively painless.
• Helps differentiate contracture from spasticity.
• Unmasks activity in the antagonists by relaxing the spastic muscles.

Side effects and precautions:

• Hypersensitivity reaction.
• Hematoma at injection site.
• Sudden weakness may cause injuries in the unprepared patient.
• Systemic toxicity (dose related).

                                     Chemical neurolysis: alcohol and phenol

Alcohol and phenol are chemical agents that block nerve conduction by creating a lesion in a portion of the nerve. Even though alcohol has fewer adverse effects and is safer than phenol it has not been used as extensively in spasticity treatment possibly because of the pain it causes during the injection. Phenol blocks are generally used for lower extremity spasticity.

Mechanism of effect:

• It causes protein denaturation and non-selective tissue destruction in the injected area. Wallerian degeneration of neurons occurs in the weeks following injection. Most axons regrow, over a period of time.
• The effect of phenol starts rapidly because of its local anesthetic properties and lasts for up to 2 to 12 months.

Phenol blocks for lower extremity spasticity:

• The rectus femoris motor point block.
• The hamstring motor point block.
• Adductor muscle motor point block.
• Tibial nerve block.

Advantages of phenol:

• Rapid action
• Longer duration
• Low cost
• No antibody formation

Disadvantages and precautions:

• Relatively painful injection
• Chronic dysesthesia and pain
• Peripheral edema, deep venous thrombosis
• Reversible sensory loss
• Systemic side effects (dose related)
• Relatively difficult technique

                                                              BOTULINUM TOXIN

Botulinum toxin, produced by the anaerobic bacteria Clostridium botulinum, is one of the most potent poisons known to man.In the past two decades it has been transformed into one of the most useful antispastic agents. Of the seven distinct toxins from A to G, only type A and B are used for therapeutic purposes. The structure of all toxins and their mechanism of action are similar, only their site of action is different. THE MECHANISM OF EFFECT

The toxin inhibits acetylcholine release at the neuromuscular junction causing a reversible chemodenervation. Studies suggest that the toxin affects the muscle spindle and afferent nerve fibers as secondary actions.

§Effect at the neuromuscular junction:

• §The toxin must enter the nerve endings to exert its effect. It becomes fully active once inside the cholinergic nerve terminal.
• §When the impulse for contraction arrives at the axon terminal acetylcholine (Ach) vesicles fuse with the nerve membrane and the Ach is released into the synaptic cleft. This causes excitation in the muscle fiber and muscle contraction.
• §The various serotypes of botulinum toxin act on different portions of the acetylcholine vesicle complex. Botulinum toxin inhibits the fusion of acetylcholine vesicles at the pre-synaptic membrane.
• §Ach cannot be released into the synaptic cleft, the impulse from the nerve to the muscle fiber is blocked and the muscle fibers innervated by that axon cannot contract. This is chemical denervation.
• §The extent of muscle weakness created by the botulinum toxin depends on the serotype, dose and volume of toxin used.
• §The effect of botulinum toxin is reversible. Nerve sprouts form at the unmyelinated terminal axon immediately proximal to the end plate.
• § These sprouts innervate the muscle fiber. Eventually, the original neuromuscular junction regains function .
• §This terminates the clinical effect in 3 – 6 months and spasticity reappears.

Specific goals for botulinum toxin A treatment:

• §To improve walking in the spastic diplegic and hemiplegic child.
• §To minimise adductor tone in the child with early hip subluxation.
• §To decrease the spasms and pain in the spastic-athetoid patients.
• §To reduce tone in the psoas muscle in patients with back pain because of hyperlordosis.
• §As a simulation for orthopedic surgery, to have a general idea of how the child will be when spasticity is reduced. 

Children with spasticity who do not have fixed contractures benefit a great deal from treatment whereas patients with dyskinesia have a variable response and athetoids do not benefit at all.

The timing of the injections is controversial. Most clinicians agree that the earlier the spasticity is reduced, the better the outcome.

Botulinum toxin can be injected as early as 18 months of age.There is no upper age limit, however, once the muscle is shortened as occurs with age, the effect of spasticity relief will not be apparent because of contracture.

Side effects (Rare, all reversible): Slight weakness at site of injection, Local pain, Flu-like syndrome, Generalized weakness and Incontinence.

Contraindications & precautions: Aminoglycoside antibiotic use, Pregnancy (for adult CP patients), Lactation (for adult CP patients). In the end this picture will help you all to summarize the effect of the three NEUROMUSCULAR BLOCKING AGENTS. • I hope i could give you the brief overview of  tone and tonal abnormalities along with use of these medications in the treatment of CEREBRAL PALSY.