DoseResponse and DoseComplications Relationships in Stereotactic Radiosurgery for Trigeminal Neuralg

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Dose-Response and Dose-Complications
Relationships in Stereotactic Radiosurgery for
Trigeminal NeuralgiaSandra Vermeulen MD, Robert
Meier MD, Vivek Mehta MD, Ron Young MD, Francisco
Li MSNorthwest Gamma Knife Center, Seattle, WA,
USA
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Trigeminal Neuralgia Overview

• Definition brief episodic, unilateral face pain,
  confined to one or more divisions of the 5th
  nerve.
• Cause tumors, vascular compression of the root
  entry zone, multiple sclerosis and idiopathic
  causes
• Pharmacotherapy is the initial treatment modality
  of choice
• Annual incidence in the United States 15,000

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Purpose/Objective

• In Patients treated with Gamma Knife Radiosurgery
  for Trigeminal Neuralgia, to determine if a
  relationship exists between dose delivered, and
  the incidence of response, or the incidence of
  complications

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Material and Methods

• 382 patients with either typical or atypical TN
  were treated between August 1993 and January 2005
• None had tumor or Multiple Sclerosis
• All were treated with a single 4-mm isocenter
  targeting the ipsilateral trigeminal nerve at the
  dorsal root entry zone
• Dose was prescribed at the Dmax

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Treatment Iso-Center
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Dose Protocols

• Three dose protocols were employed using an
  output factor or 0.87
• 76 patients received 76 Gy
• 179 patients received 87 Gy
• 127 patients received 98 Gy

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Patient Characteristics
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Treatment Characteristic
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Results

• Treatment outcomes were measured at 6 months, at
  last follow-up and actuarially
• Favorable responders were patients rendered
  free of pain, either with or without medication
• Complications were defined as lasting neurologic
  deficits attributable to treatment and included
  numbness or paresthesias

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Pain Relief

• At 6 months post-treatment, favorable outcomes
  occurred with similar rates in all 3 groups
• Log-rank test showed no significant difference in
  the Kaplan-Meier curves for these three groups
  (p0.835)

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Complications

• The only lasting complication was new numbness or
  paresthesia
• At 6 months, patients treated with higher doses
  more often developed sensory deficits (plt0.05)

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Severity of Numbness
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Conclusion

• In stereotactic radiosurgery for TN, escalation
  of maximum nerve dose from 76 Gy to 87 Gy to 98
  Gy does not significantly improve pain relief,
  but is associated with a higher incidence of
  complications