Clinical Study
Clinical outcomes of 114 patients who underwent Gamma-knife radiosurgery for medically refractory idiopathic trigeminal neuralgia

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Abstract

The optimal radiation dose and target of Gamma-knife radiosurgery (GKRS) for medically refractory idiopathic trigeminal neuralgia (TN) are contentious. We investigated the effects and trigeminal nerve deficits of GKRS using two isocenters to treat a great length of the trigeminal nerve. Between January 2005 and March 2010, 129 patients with idiopathic TN underwent GKRS at the West China Hospital of Sichuan University. A maximum central dose of 80–90 Gy was delivered to the trigeminal nerve root with two isocenters via a 4 mm collimator helmet. One hundred and fourteen patients were followed-up periodically by telephone interview to determine the effects, trigeminal nerve deficits and time to the onset of pain relief. The mean follow-up duration was 29.6 months. One hundred and nine patients had complete or partial pain relief and the treatment failed in five patients. Nine patients experienced a recurrence after a mean time of 12.7 months, following an initial interval of pain relief. There were no significant differences between patients with different grades of pain relief with respect to central doses. The mean time to the onset of pain relief was 3.6 weeks. The time to the onset of complete pain relief was significantly shorter than that for partial pain relief. Forty-nine patients reported mild-to-moderate facial numbness and one patient experienced paroxysmal temporalis muscle spasms two weeks after the treatment. GKRS treatment for medically refractory idiopathic TN with two isocenters resulted in an initial pain improvement in 95.6% of patients. The early response to the treatment might suggest a good outcome but, given the high incidence of nerve deficits, GKRS for TN with two isocenters is not recommended as a routine treatment protocol.

Introduction

Trigeminal neuralgia (TN) is a neuropathic disorder characterized by episodes of intense facial pain originating from the trigeminal nerve. Everyday quality of life can be seriously affected, as the condition can be triggered by common activities such as eating, talking, shaving and brushing teeth. Several techniques are considered for treatment of medically refractory TN including microvascular decompression (MVD), radiosurgery, radiofrequency ablation, balloon compression and ethanol injection. Gamma-knife radiosurgery (GKRS) is a minimally invasive surgical technique for the treatment of TN that has a low incidence of morbidity.1 Although the treatment procedure has been standardized, the optimal treatment parameters, including the radiation dose and the treatment volume of the trigeminal nerve, are yet to be confirmed. This retrospective study presents our experience with 114 patients treated by GKRS with two isocenters.

Section snippets

Patients

Between January 2005 and March 2010, 129 patients with medically refractory idiopathic TN underwent GKRS. Patients were followed-up periodically by telephone interview after the treatment. Fifteen patients (11.6%) could not be contacted. Eleven patients were treated several months before the May 2008 earthquake and were lost to follow-up after that time; these patients were not included in this study.

Patient characteristics are summarised in Table 1. The male:female ratio was 69:45, and the

Pain control

The median follow-up time of the 114 patients was 29.6 months (range = 6–58 months). At the last follow-up, complete pain relief (Grade 1) was achieved in 85 patients (74.6%), and 24 patients (21.1%) reported partial pain relief (Grade 2). The remaining five patients (4.4%) reported treatment failure (Grade 3).

Patients who had undergone previous invasive treatment had less promising results: 38 patients (Grade 1), 18 patients (Grade 2) and four patients (Grade 3) had undergone previous invasive

Discussion

Most recent reports describe GKRS treatments targeting the trigeminal nerve REZ. Typically, radiation is focused a sufficient distance from the pons to avoid damage to the brainstem. However, debate remains regarding where to focus the radiation and the optimal trigeminal nerve length within the treatment volume. The outcomes of different studies are difficult to compare as a result of the different treatment protocols used. An early study conducted by Pittsburgh University found that

Conclusion

GKRS is a safe and effective treatment option for patients with idiopathic TN. There is not enough evidence to demonstrate the advantages of GKRS with two isocenters in the early stage following treatment, and the incidence of trigeminal nerve toxicity might be increased with this protocol. The time to the onset of pain relief may be a predictive factor for complete pain relief; however, long-term follow-up studies should be carried out. Considering the high incidence of nerve deficits, GKRS

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