ITB Therapy

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ITB Therapy
By Carey Miklavcic
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Spasticity

• Motor disorder characterized by velocity
  dependent increase in tonic stretch reflex
  (muscle tone).
• Results from imbalance in excitatory and
  inhibitory impulses that control alpha motor
  neurons
• Insufficient inhibition along neural pathway
  results in impaired synaptic activity at SC
  levelexcessive muscle tone

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Characteristics of Upper Motor Syndrome

• Positive symptoms
• Cutaneous reflexes (Babinski)
• Hyperactive reflexes
• Clonus
• Rigidity
• Athetosis
• Spasticity

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• Negative symptoms
• Decreased dexterity
• Paresis or weakness
• Fatigability
• Impaired coordination
• Impaired motor control and planning

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ITB pump

• Used to treat moderate and severe spasticity of
  both spinal and cerebral origin in patients
  either refractory to oral meds or have
  intolerable SE to meds

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Mechanism of Action

• Binds to GABAB receptors (substantia gelatinosa)
  causing inhibition of mono and polysynaptic
  spinal reflexes
• Thought to ? excitatory NT release from primary
  afferent terminals by reducing Ca influx
• Intrathecal is delivered directly to CSF thus
  lower systemic doses needed for greater effect on
  spasticity (100x less)

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Risks and Side Effects

• Drowsiness, dizziness, nausea, hypotension, HA,
  excessive weakness
• Overdose may occur with incorrect filling or
  programming?respiratory depression, coma
• Withdrawal may cause ? spasticity, hyperthermia,
  mental status ? and rhabdomyolysis, multisystem
  failure and death

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Evaluation of Response

• Tendon reflex scale
• Ashworth scale
• Spasm frequency scale
• Functional scales
• All have limitations

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Neurophysiologic Evaluation

• Index of SC neuronal response to treatment could
  complement clinical assessment scales
• Not dependent on muscle stiffness
• Evaluation techniques
• Hoffman reflex
• F wave
• FWR

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H reflex

• Commonly evoked by stimulating tibial n. in
  popliteal fossa and recording from soleus
• Amplitude ratio between max H reflex and max M
  wave is index of spasticity
• Strong correlation with clinical assessment of
  muscle stiffness is lacking
• H reflex amplitude is typically decreased or
  abolished after ITB treatment (dose dependent)

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Flexion Withdrawal Reflex

• Evoked by mechanical stim of plantar surface
  (Babinski)
• Parise et al found that continuous ITB attenuated
  FWR amplitude and ?reflex threshold

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F wave

• Produced by antidromic activation of motor
  neurons in anterior horn
• Some studies show ? in F wave amplitude, duration
  and persistence with oral and ITB treatment
• Less sensitive than H reflex

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Pump Basics 101
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Screening Trial

• Injection 50mcg via percutaneous LP
• ? spasticity gt 2 point drop in avg. LE Ashworth
  score for spinal origin, gt 1 point drop for
  cerebral origin
• Pts with dystonia may require continuous infusion
  trial

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• Pump is implanted sq in abdominal wall and
  catheter is tunneled to back and placed in
  arachnoid space
• Types of pumps
• Infusaid constant rate, gas powered
• Medtronic SynchroMed Drug Infusion Pump-used for
  ITB electronic and programmable to deliver
  boluses or continuous infusion

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• Initial dose is 50-100 mg/day
• Titrate upward 10-30 (SO) 5-15 (CO) until
  results obtained
• Maintenance ? 10-20
• Average effective dose 200-500mg/day but some as
  high as 1500mg/day

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Pump Refill

• Identify pump model, reservoir size
• Confirm location center reservoir fill port
• Use refill template provided in kit
• Completely aspirate reservoir before filling
• Do not exceed reservoir volume
• Record actual residual volume, expected residual
  volume and refill volume
• Remember Intrathecal baclofen is stable for 90
  days in the pump

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References

• Yablon SA, Stokic DS Neurophysiologic Evaluation
  of Spastic Hypertonia Implications for Maagement
  of Intrathecal Baclofen Pump. Am J Phys Med
  Rehabil 2004 83(suppl)S10-S18.
• Ivanhow CB, Reistetter TA Spasticity The
  Misunderstood Part of the Upper Motor Neuron
  Syndrome. Am J Phys Med Rehabil 2004
  83(suppl)S3-S9.
• Medtronic ITB Therapy Reference Guide