Object: The authors sought to establish whether the safety-efficacy of Gamma Knife radiosurgery (GKRS) as a second treatment
for intractable trigeminal neuralgia (ITN) are influenced by prior microvascular decompression (MVD) which remains, for some
of the authors, the reference technique.
Methods: Between July 1992 and November 2010, 737 patients have been operated with GKRS for ITN and prospectively
evaluated in Timone University Hospital in Marseille, France. Among these, 54 patients had a previous MVD history.
Radiosurgery using a Gamma Knife (model B or C or Perfexion) was performed relying on both MR and CT targeting. A single
4 mm isocenter was positioned in the cisternal portion of the trigeminal nerve at a median distance of 7.6 mm (range 3.9-
11.9) anteriorly to the emergence of the nerve (retrogasserian target). A median maximum dose of 85 Gy (range 70-90) was
delivered. Are further analyzed only 45 patients with previous MVD and a follow-up longer than one year (the patients with
megadolichobasilar artery compression and multiple sclerosis were excluded).
Results: The median age in this series was 56.75 years (range 28.09-82.39). The median follow-up period was 39.48 months
(range 14.10-144.65). All the patients had a past history of surgery, with at least one previous failed MVD, but also a
radiofrequency lesion (RFL) in 16 (35.6%) patients, balloon microcompression in 7 (15.6%) patients and glycerol rhizotomy
in 1 case (2.2%). Thirty-five patients (77.8%) were initially pain free in a median time of 14 days (range 0, 180). Patients from
this group had less probability of being pain free compared to our global population of essential trigeminal neuralgia without
previous MVD history (p=0.010, hazard ratio of 0.64). Their probability of remaining pain free at 3, 5, 7 and 10 years was 66.5%,
59.1%, 59.1% and 44.3%, respectively. Twelve patients (34.3%) initially pain free experienced a recurrence with a median
delay of 31.21 months (range 3.40-89.93). The hypoesthesia actuarial rate at 1 year was 9.1% and remained stable till 12 years
with a median delay of onset of 8 months (range 8-8).
Conclusions: Retrogasserian GKRS proofed to be safe and effective on the long-term basis even after failed previous MVD.
Even if the initial result of pain free was of only 77.8%, the toxicity was low with only 9.1% hypoesthesia. No patient reported
a bothersome hypoesthesia. The probability of maintaining pain relief in long-term was of 44.3% at 10 years.