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Spasticity can be defined as
velocity dependent hypertonus seen in upper motor neuron (UMN) diseases.
It manifests as resistance to passive movement, involuntary spasms,
hyperactive stretch reflexes, abnormal primitive reflexes and difficulty
in co-ordination of movements. As it interferes with the patient’s
activities of daily living (ADL) and can cause serious disability, it
constitutes a major problem for professionals who care for patients with
central nervous system (CNS) pathologies.
Interference with motor mechanism resulting in spasticity can be caused by congenital disorders, cerebral palsy trauma, inflammatory or vascular lesions, multiple sclerosis,
hereditary disorders, etc. After dealing with the etiological problem, the patients may be left with residual
spasticity which needs to be ameliorated.
T he patients suffering from
spastic disorders may have associated neurological problems or orthopedic
complications such as contractures, dislocations, and deformities. A
multidisciplinary rehabilitative approach is essential.
Pathogenesis of spasticity:
Normotonia is the
result from a fine balance between the suprasegmental inhibitory and
segmental facilitatory impulses. The gamma efferents in the anterior root
carry the impulses from the motor nuclei to the muscle spindle. The
muscle spindles contract and generate impulses which are carried by the
gamma afferents in the posterior root to the alpha motor neurons in the
anterior horn and subsequently by alpha motor fibers to the extrafusal
muscle fibers to produce contraction.
The exact
pathogenesis of spasticity is not clear. Spasticity, as a result of a
variety of lesions of the cerebral cortex, brain stem or spinal cord, is
presumed to be caused by involvement of the inhibitory pyramidal and parapyramidal descending
tracts terminating on the spinal facilitatory myotatic reflex. A
lesion of the descending tracts disturbs this
equilibrium leading to spasticity. In addition, loss
of supraspinal input leads to an increase in the discharge from dorsal root fibers; this results in excess of
afferent impulses reaching the interneurons and anterior horn cells, resulting in their overactivity.
Clinical features:
In traumatic lesions (e.g. spinal cord
injury, brain injury), spasticity evolves gradually after the spinal
shock period, which is characterized by depressed reflexes and
hypotonus. In non-traumatic lesions (e.g. tumors, spondylosis),
there is no period of spinal shock.
Its characteristic findings are abnormal
resistance to passive limb movement (hypertonus) and hyperactive stretch
reflexes; however not all hypertonus is spasticity. It is a
velocity-dependent phenomenon that helps distinguish it from other
non-velocity-dependent forms of hypertonus such as those observed in
dystonias or Parkinson’s disease.
In general, it involves flexor muscles
in upper extremities and extensors in lower extremities. In spasticity,
resistance to the passive movement of a limb is maximal at the beginning
of the movement and decreases as more pressure is applied.
Symptoms of spasticity include increased
muscle tone, abnormal limb posture, excessive contraction of antagonist
muscles, and hyperactive tendon reflexes. There may also be a phasic
pattern of uncontrolled, sometimes violent, leg spasms that can result in
fractures, dislocation and other serious injuries.
Spasticity may interfere with the normal
control of limb position and movement, which can cause a wide range of
clinical problems. The patient may complain of difficulty walking,
stiffness, clonus (alternating muscle contraction and relaxation) or
impaired balance.
Spasticity may not only mask residual
motor function but also creates difficulty in transfer ambulation and
self-care activities such as eating, grooming, dressing and toileting. It
also affects patients sleep and sexual function.
There
is also a risk that the patient may develop complications such as
pressure sores and contractures. A contracture is caused by fibrosis of
muscle or connective tissue, which produces shortening of the muscle and
may result in deformity of a joint.
Evaluation:
Disability produced by spasticity
depends on the degree to which mobility is restricted, and this varies
from patient to patient.
Spasticity may
sometimes help to perform certain motor activities, reduces the risk
of deep venous thrombosis (DVT) and edema, helps maintain bone muscle
mass and locking knees during standing and walking. and should not be disturbed.
It is useful to
establish the non-progressive nature of spasticity before
surgical help
can be offered.
In most patients the nature of the
disorder is obvious, e.g. cerebral palsy.
Occasionally there may be difficulty in differentiating
nonprogressive conditions like
cerebral palsy from progressive metabolic or hereditary disorders. The progressive symptomatology, regression of milestones, consanguinity,
family history, the clinical
picture and the absence of a history of insult to the developing brain
help to confirm a progressive disorder.
A detailed clinical history is essential
in order to determine to what extent spasticity interferes with the
patient’s ADLs and motor function and if it should be treated.
Radiation and degree of involuntary
spasms, involved muscle groups, occurrence of pain and precipitating
factors should be noted.
A thorough physical examination
including active and passive range of motion (ROM), deep tendon reflexes,
pathological reflexes and voluntary muscle strength is carried out.
Spontaneous spasms and their distribution should be noted.
Functional impairments and improper bed
or wheelchair positioning due to spasticity should be examined.
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Quantification methods of
spasticity consist of clinical (Ashworth scale), electroneuromyographic
(H-reflex/M ratio, dynamic EMG) and biomechanical (ramp and hold test,
pendulum test) analysis
Other quantitative methods are
not widely used in daily practice as they are time consuming; require
special instrumentation to give additional information.
Management:
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The Ashworth Scale
(Ashworth, 1964).
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1) No increase in tone
2) Slight increase in tone,
giving a ‘catch’ when affected part is moved in flexion or extension
3) More marked increase in
tone, but affected part easily flexed
4) Considerable increase in
tone, passive movement difficult
5) Affected part rigid in
flexion or extension.
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The goal is to
maximize functional capacity with minimum side effects.
The target for
neurosurgical therapy and the approach must be chosen with care.
The role of the
surgeon and the associate team members should be clearly defined.
The patient and
the guardians must be well informed. Everyday care often falls on family and
guardians, which may prove to be an emotional and financial strain.
Education of both the family and patients is important. The family
provide valuable opinions concerning progress and may be the first to
spot worsening spasticity.
Before treatment is initiated,
exacerbating factors and noxious stimuli should be eliminated. This
includes proper positioning, avoiding tight clothing and wrapping,
treatment of urinary complications (stones, infections), proper bladder
and bowel management, prevention of pressure, ulcers, contractures, and
DVT.
Disabling
spasticity is initially treated with non surgical therapies.
Physical Measures:
Physical therapy
must be the first line of treatment and that medications, and other
measures may added later.
Physical therapy
helps to improve the strength and control of muscles.
Proper motor
activity depends on adequate control of various muscles. Certain physical
interventions such as positioning, splinting and casting have proved to
be helpful in decreasing reflex muscle tone. Daily range of movement and
stretching exercises prevent muscle shortening and contracture and reduce
spasticity.
Local heat and cold applications are
valuable adjuncts to other modalities.
Electrical stimulation of the peripheral
nerves and muscles and biofeed back can also help spasticity reduction.
Physiotherapists and Orthotists and
Occupational therapists have an important role.
Biofeedback therapy has long been used
to treat various neurological problems; it has been reported to help in
spasticity as well.
Oral medications:
Diazepam is the oldest antispastic
agent. It enhances the action of the inhibitory neurotransmitter GABA by
binding to benzodiazepine receptors coupled to GABAA receptors. It is
effective in high doses.
Baclofen is the most
widely used antispastic agent. It was introduced by Birkmayer in 1967. A
structural analogue of GABA, it binds to the GABAB receptor at pre and
post synaptic sites. It inhibits mono and polysynaptic transmission at
spinal cord level and depresses the CNS. The net effect is inhibition of
spinal reflexes. Baclofen is effective with a well-demonstrated use in MS
and spinal cord injury. But it is less effective in spasticity of
cerebellar origin. In patients with Parkinson's disease baclofen may
interfere with dopamine metabolism, so concurrent use with levodopa should
be avoided. Baclofen may also lower the seizure threshold, so caution
must be taken in treating patients with epilepsy. The hypotensive effect
of antihypertensive drugs (eg ACE inhibitors) may be enhanced when
baclofen is used concurrently. It may be wise to avoid ibuprofen and
other non-steroidal anti-inflammatory drugs (NSAIDs) during baclofen
treatment. NSAIDs may cause renal insufficiency, which can decrease the
renal excretion of baclofen. This increases the risk of baclofen
toxicity, which presents as confusion, bradycardia, disorientation, and
blurred vision.
Tizanidine is relatively a
newer drug. The central alpha 2 adrenoceptor agonist tizanidine is a
myotonolytic agent with similar efficacy to that of baclofen and a more
favorable tolerability profile.
Dantrolene reduces calcium
release in skeletal muscle and is the only antispastic agent to act
peripherally. Others act on CNS. In clinical practice, dantrolene is most
suited to patients with good muscle strength who are limited by their
spasticity, or those with complete paralysis, such as paraplegics.
Gabapentin is emerging as
a useful alternative in spasticity management. Patients may
require higher doses of this drug (2700–3200 mg/d), and its
safety at this level over long periods in spasticity is
unknown; thus, caution is advised.
Clonidine is used only as
an alternative when other medications are ineffective; its use
should be limited to very resistant cases.
Fampridine-SR
(sustained-release 4-aminopyridine) is a potassium-channel blocker
and has recently been shown to be helpful in managing spasticity
in patients with spinal cord injuries.
Delta-9-tetrahydrocannabinol, the
active ingredient in cannabis, has also been shown to be useful
in spasticity.
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All of the centrally acting
drugs are sedating at therapeutic doses, and many patients cannot get
adequate muscle relaxation without too much sedation.
Additionally, all of these
medications cause weakness, so that adequate control of spasticity
almost invariably causes some weakness in addition to some sedation.
Care should be taken when antispastic drugs are used in combination
with other CNS depressants because drowsiness and sedation may be
enhanced.
The goal is to reduce
spasticity without causing too much weakness.
The dosage has to be
individualized and their liver function is monitored periodically.
Withdrawal must be gradual.
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Drug
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Starting dose
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Daily maintenance
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Maximum recommended dose/day
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Diazepam
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5mg nocte or 2mg bd
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20-40mg
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0-60mg
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Baclofen
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5mg tds
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60-80mg
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100mg
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Dantrolene
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25mg o.d
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100mg
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400mg
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Tizanidine
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2mg nocte
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16-24mg
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36mg
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Surgical
procedures:
Only in severe or resistant cases after
other techniques have failed or patients have developed complications
should it be necessary to use more advanced and specialized techniques,
or to intervene surgically.
Shortening of the
muscles and other soft tissues, dislocation or subluxation of joints,
deformities, etc influence the results of surgery adversely. Various
orthopedic procedures can be used including tenotomy, tendon lengthening
and tendon transfers to improve function especially in cerebral palsy. Orthopedic and plastic surgeons have an
important role. The
improvement depends on the presence of preoperative selective control and
voluntary strength in various parts of the body.
a) Nonablative neurosurgery:
Bupivacain nerve blocks on the
peripheral neural structures reduce spasticity by reducing excessive
gamma fusimotor drive. These procedures can also be used prior to any
contemplated definitive surgery. Inaccessible nerves can be approached by
an open method.
Botulinum toxin injection: Motor
plate neurolysis using either phenol or botulinium-Phenol has been utilized
successfully in selected cases for over 30 years, and provides rapid
control of spasticity in a cost-effective manner and improves function.
Botulinum toxininjection is currently
the favored local technique and has largely replaced the others. It
is a neurotoxin produced by the gram-positive bacterium Clostridium
botulinum. There are eight antigenically different strains of
botulinum toxin. Type A toxin is most commonly used because it is potent,
easily crystallized and relatively stable. It is established as a
treatment of blepharospasm, spasmodic dysphonia and spasmodic
torticollis. It has also been used in management of cerebral palsy
recently.
Small doses of botulinum toxin are
injected directly into the overactive muscle,in the same
manner as local anesthetics. A small needle is placed into the target
muscle. Targeting is confirmed simply by feel in larger, more accessible
muscles, or by electromyography or electrical stimulation monitoring in
small or deep muscle groups. Small muscles may be injected in only 1-2
sites, while larger muscles may require 3-4 sites. While most people have
no trouble tolerating the small needle punctures, local anesthetic cream
or sedation is available, and may be particularly useful for children.
Dose dependent relaxation of the target
muscle is achieved within 1-2 weeks, with little or no effect on adjacent
muscles. The toxin is believed to act via three mechanisms: (a)
inhibition of calcium influx (b) induction of calcium efflux (c) direct
action on acetylcholine release. It is most effective in treating focused
areas of spasticity. The injected muscle is paralyzed until nerve
sprouting forms new neuromuscular junctions. At this point the clinical
effect wears off, typically after 2-4 months, so repeated injections are
required to maintain the antispastic effect. However, injection intervals
must not be more frequent than once every 12 weeks to minimize the risk
of non-responsiveness. Non-responsiveness is suggested to be due to the
development of antibodies to the toxin. In such cases, Type B toxin may
help.
Botulinum toxin has been evaluated in
various spastic disorders, including MS, cerebral palsy and stroke. It is
well tolerated and generally produces no deterioration of functional
ability. Botulinum toxin A injection is safe with few side effects and a
simple procedure. There is no need for precise localization (as in a
nerve block), and the dosage can be easily adjusted according to the
previous response. In addition, there is no sensory disturbance, and the
effect is reversible after 2-3 months which may be advantageous in some
cases. However, there is a small risk of inducing over weakness of the
injected muscle. In severe and widespread spasticity focal
techniques may not improve function, unless they are used in combination
with a global tone reduction using oral medication, or in combination
with physical therapy.
Botulinum toxin should not be used in individuals with a known hypersensitivity to any
component of the formulation, patients who have generalized disorders of
muscle activity (e.g. myasthenia gravis), patients where aminoglycoside
antibiotics or spectinomycin are already being used or are likely to be
used, patients who have bleeding disorders of any type, and pregnant or
lactating women.
Intrathecal baclofen: Because of
poor penetrance of the blood brain barrier (BBB), intrathecal baclofen may be a useful option in
those patients who cannot get adequate muscle relaxation without too much
sedation. By providing a high local concentration in the lumbar cord with
a very low systemic concentration, muscle relaxation can be accomplished
without sedation. Since it was first proposed by Penn and Kroin in 1984,
this new form of treatment, in which baclofen is delivered directly to
CSF via an implantable programmable pump, had become an area of growing
interest. Severe intractable spasticity refractory to other treatments
can be managed with intrathecal baclofen. Under local anesthesia, an
intrathecal tube is passed through the lumbar intervertebral space and
left in the subarchnoid space. The other end is connected to a reservoir
positioned in any convenient site in the abdominal wall. The reservoir is
filled with baclofen which can be delivered to the spinal cord through a
programmable pump in a smooth and sustained manner. A prior trial of
intrathecal instillation of baclofen by a needle helps.
Development of intolerance is a major
concern, though results of a recent study found that tolerance occurs
only within the first 12 months and does not require discontinuation of
the treatment.
Neurostimulation: Electrical
stimulation of spinal cord (dorsal column and the posterior
column) has a mild effect in rigidity and spasms. Electrodes are
implanted at the desired level, either by open method or percutaneously
under fluroscopy/CT control. The electrodes are connected to a
subcutaneous reservoir. The frequency is controlled by the patient
through an external stimulator(transmitter). Programmable receiver and
transmitter have been devised.
The mechanism is not clear. Stimulation
of descending inhibitory pathways, release of chemical substances,
blockade of afferent pathways, blockade of nociceptive afferent
influences on long loop reflexes, and influence on the ascending and
descending reticular systems have been proposed. It is rarely used
nowadays except in some cases of mild paraparesis in MS.
Central neurostimulation have been
expensive with equivocal results.
The electrodes are positioned
steretactically. Stimulation of the sensory relay nuclei of the
thalamus has been tried.
The long-term results of cerebellar
(cortex or dentate nucleus) stimulation are poor and the method
has been abandoned.
b) Ablative neurosurgery:
Chemodenervation:
Peripheral nerve block using phenol/alcohol
is a relatively old technique. Focal chemodenervation is achieved by
injecting phenol 2-5 per cent into a peripheral nerve, which causes
protein denaturation of nerve fibres. Peripheral nerve block may be used
to manage localized spasticity as a temporary measure in spasticity
following incomplete spinal cord injury.
Intrathecal alcohol and
phenol may be of help in those with short life expectancy. The results
are not satisfactory.
Neurectomy:
Selective (functional) neurectomy
involves intraoperative stimulation and division of appropriate fascicles
by open method. Non functional procedures have no place.
Rhizotomy:
Foester first performed
posterior rhizotomy in 1913. In 1945, Munro described the anterior
rhizotomy for marked spasticity. Fasano (1977) introduced functional
posterior rhizotomy at the conus medullaris with the use of
electrical stimulation of the rootlets to detect the hyperactive
rootlets. Peacock (1982) modified and reintroduced selective
posterior selective posterior rhizotomy at cauda equina. Rhizotomy
is an open surgical technique involving multiple level laminectomy and
expose the spinal cord at the appropriate levels. After laminectomy
the dura is opened and the S1 root can easily be identified as being the
largest. Generally, the posterior roots are broad and flat whereas the
anterior roots are smaller and rounded. In order to verify appropriate
roots, intraoperative monitoring system including EMG and SEP should be
placed in the appropriate dermatome and myotome. After
identification of roots is completed, involved roots are then
divided. Reports suggest a very high success with these procedures.
Percutaneous radiofrequency
rhizotomy:
It avoids the risks of open surgery.The
exact mechanism of relief of spasticity by thermocoagulation is not
known. Recurrence is common; but the procedure can be repeated. CT/MRI
guidance may be used.
DREZ lesioning:
At the dorsal root entry zone, the fine
myelinated and unmyelinated nociceptive fibres and large 'A' alpha
myotatic fibres are rearranged more centrally and laterally. A lesion at
45 degrees into the DREZ spares the lemniscal fibres responsible for
touch and kinesthetic sensations. At open surgery, the selected posterior
rootlets (as confirmed by electrostimulation of the root lets) are
retracted dorsomedially and a 2mm deep incision is made at a 45 degree
angle into the ventrolateral region of DREZ.
This procedure appears to be more
effective in spasticity due to spinal lesions. Motor movements also may
improve.
Percutaneous CT/MRI guided
drezotomy and endoscopic techniques are increasingly being reported.
Longitudinal myelotomy:
Bischof (1951)
introduced this procedure for the reduction of spasticity. He
divided the cord into anterior and posterior halves from L1 to S1 by
introducing a knife anterior to dentate ligaments and reported good
results.
Pourpre modified it. He
opened the dorsal fissure and passed the knife laterally,
disconnecting the dorsal and ventral horns. The corticospinal fibers were
spared.
Stereotactic myelotomy, disconnecting
dorsal and ventral horns, is a more finer technique.
Endoscopic procedures have also been reported.
Myelotomy is beneficial to patients with
paraplegia and painful spasticity, who do not have hope of regaining
voluntary motor function ideally. However, transections of basic
pathways of spasticity are not always sufficient for complete antispastic
effects. Good results after the operation may deteriorate in time.
Stereotactic Ventrolateral
thalamotomy relieves hypertonia due to rigidity. It is not indicated
for hypertonia due to spasticity alone. Stereotactic Pulvinotomy,
stereotacic lesioning of Fastigeous nucleus and stereotactic Cerebellar
lesions have been reported with good results in the past. Recent
developments in stereotaxy may give a fresh lease to these procedures.
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