Spasticity and Anti-spasticity Medications

Question 1

What is the definition of Spasticity?

Answer 1

• Spasticity is a motor disorder marked by a velocity-dependent increase in muscle tone
• Spasticity results from hyper-excitability of the tonic stretch reflex in people with upper motor neurone (UMN) syndrome following damage to the brain or spinal cord.

Question 2

Why does spasticity arise?

Answer 2

Spasticity is considered to be a positive sign of the upper motor neuron syndrome (UMNS), which refers to motor behaviours resulting from lesions proximal to the alpha motor neuron, therefore within the spinal cord or brain

Question 3

What is the mode of action of Baclofen?

Answer 3

• Baclofen is a skeletal muscle relaxant / antispasmodic
• Baclofen activates GABA receptors (specifically GABA-B)
• Baclofen is thought to reduce the release of excitatory neurotransmitters in presynaptic neurons and stimulate inhibitory neuronal signals in postsynaptic neurons, thus leading to decreased input to muscle fibres

Question 4

What is a common dose of Baclofen?

Answer 4

• Baclofen is commenced at 5mg TDS
• Normal maintenance dose can be around 20mg TDS
• Maximum daily dose of Baclofen is 100mg

Question 5

What are side effects of Baclofen?

Answer 5

• Sedation
• Drowsiness
• Dizziness
• Confusion
• Withdrawal symptoms
• Can lower seizure threshold

Question 6

What is the mode of action of diazepam

Answer 6

• Diazepam works by facilitating GABA’s effects on GABA receptors, leading overall to membrane hyperpolarization and decreased firing of neurons
• Its net effect is increased presynaptic inhibition and reduced reflexes.

Question 7

Tell me about some non-pharmacological means of managing spasticity?

Answer 7

As spasticity arises through abnormal processing of sensory stimuli, nociceptive stimuli will aggravate it and make it more difficult to treat. Aggravating factors should be identified and minimised e.g. pain, infection, constipation, tight clothing, poor management of posture

Other measures that can help:
- Stretching
- Splinting
- Vibration
- Serial casting
- Direct tendon pressure
- Functional Electrical stimulation

Question 8

What are some side effects of diazepam

Answer 8

• Diazepam is the most sedating of the anti-spasticity medications
• Diazepam can impair memory
• Diazepam can impair REM sleep
• Can lead to significant CNS depression (particularly if used in combination with alcohol)

Question 9

What is the mode of action of Dantrolene?

Answer 9

• Dantrolene acts peripherally at the level of the muscle by blocking the release of calcium from the sarcoplasmic reticulum
• Note: it has minimal effect on smooth muscle and cardiac muscle

Question 10

What is the mode of action of Tizanidine?

Answer 10

• Tizanidine works as an alpha-2 adrenergic agonist, chemically related to clonidine. Its mechanism of action is to enhance pre-synaptic inhibition of the spinal reflex

Question 11

What are some side effects of Dantrolene

Answer 11

• Liver toxicity - specifically hepatonecrosis - is seen in 1% of those given Dantrolene (particularly high risk are women over the age of 30, who have been taking higher doses for over 2 months). LFTs should be monitored
• Drowsiness, sedation, weakness, fatigue, paraesthesias, diarrhoea, nausea, and vomiting are also side effects

Question 12

Name a scale that can be used to rate spasticity?

Answer 12

The Ashworth Scale

Question 13

What is zero on the Ashworth Scale?

Answer 13

No increase in tone.

Question 14

What is 1 on the Ashworth Scale?

Answer 14

“Catch and release,” or minimal resistance towards end-of-range of motion

Question 15

What is 2 on the Ashworth Scale?

Answer 15

Increased muscle tone through the majority of ROM while still able to move the affected part

Question 16

What is 3 on the Ashworth Scale?

Answer 16

Difficult passive movement throughout the majority of ROM

Question 17

What is 4 on the Ashworth Scale?

Answer 17

Affected part in rigid flexion or extension

Question 18

Why is spasticity harmful?

Answer 18

If left untreated, a vicious cycle occurs, in which unopposed contraction (spastic dystonia) in the affected muscle groups leads to an abnormal limb posture, resulting in soft tissue shortening and further biomechanical changes in the contracted muscles.

This in turn prevents muscle lengthening and
perpetuates further stiffness.

Spasticity can be painful, distressing and is a potentially costly disability.

Question 19

What is a standard dose for Dantrolene?

Answer 19

• Patients are started on 25mg OD
• Dose can be increased to 100mg QDS
• Normal dose is around 75mg TDS
• Dose is generally increased at weekly intervals

Question 20

What are some side effects of Tizanidine?

Answer 20

• Sedation
• Drowsiness
• Bradycardia
• Dry mouth
• Dizziness
• Hypotension
• Liver damage (requires monitoring of LFTs)

Tizanidine also has a relatively short half-life and, as such, requires frequent dosing