====== Ivalon ======

Many [[ablative]] [[procedure]]s are effective for [[hemifacial spasm]] (HFS) (including sectioning of divisions of the [[facial nerve]]), however, this leaves the patient with some degree of facial paresis. The current procedure of choice for HFS is [[microvascular decompression]] (MVD) wherein the offending [[vessel]] is physically moved off of the nerve, and a [[sponge]] (e.g. [[Ivalon]]®, polyvinyl formyl alcohol foam) is interposed as a [[cushion]].
Other cushions may not prove to be as satisfactory ([[muscle]] may disappear, and [[Teflon]] felt may thin
((Rhoton AL. Comment on Payner T D and Tew J M:
Recurrence of Hemifacial Spasm After Microvascular
Decompression. Neurosurgery. 1996; 38)).

Synthetic materials, such as [[Teflon]] or Ivalon sponges have also been associated with a direct subsequent neurovascular compression by the same vessel because of a slipped prosthesis
((Liao JJ, Cheng WC, Chang CN, Yang JT, Wei KC, Hsu YH, Lin TK. Reoperation for 
recurrent trigeminal neuralgia after microvascular decompression. Surg Neurol.
1997 Jun;47(6):562-8; discussion 568-70. PubMed PMID: 9167781.)).

Compression of the trigeminal root entry zone, caused by the prosthesis itself or by severe adhesions, has been reported by several authors 
((Cho DY, Chang CG, Wang YC, Wang FH, Shen CC, Yang DY. Repeat operations in
failed microvascular decompression for trigeminal neuralgia. Neurosurgery. 1994
Oct;35(4):665-9; discussion 669-70. PubMed PMID: 7808609.
))
((Yamaki T, Hashi K, Niwa J, Tanabe S, Nakagawa T, Nakamura T, Uede T, Tsuruno
T. Results of reoperation for failed microvascular decompression. Acta Neurochir 
(Wien). 1992;115(1-2):1-7. PubMed PMID: 1595390.
))
, and even indirect vascular compression caused by fairly hard implants like Ivalon has been reported 
((Goya T, Wakisaka S, Kinoshita K. Microvascular decompression for trigeminal
neuralgia with special reference to delayed recurrence. Neurol Med Chir (Tokyo). 
1990 Jul;30(7):462-7. PubMed PMID: 1701856.
))
((Jannetta PJ, Bissonette DJ. Management of the failed patient with trigeminal
neuralgia. Clin Neurosurg. 1985;32:334-47. Review. PubMed PMID: 3905144.
)).