Vascular Offenders in Trigeminal Neuralgia: A Unified Classification and Assessment of the Outcome of Microvascular Decompression

BACKGROUND: Vascular loop compression remains the most accepted theory for trigeminal neuralgia (TN). Apart from the normal adjoining vascular loops, certain unusual vascular loops incriminated in TN such as vertebrobasilar dolichoectasia and pure venous compressions do not truly fit into the traditional classification. Moreover, vascular diseases such as cavernoma and aneurysms causing TN are considered as secondary TNs. There is a lack of unified classification for TN with underlying vascular offenders, otherwise amenable to microvascular decompression. METHODS: We classified vascular offenders in TN (n = 53) into the usual offenders such as superior cerebellar artery or anterior inferior cerebellar artery loop with (n = 4) or without (n = 34) superior petrosal vein loop (n = 38, group I). The unusual vascular offenders (n = 15, group II) comprised unusual arterial loops (n = 4, IIa), pure venous compressions (n = 8, IIb) and vascular diseases (n = 3, IIc). The clinical symptoms, pain severity scores, and surgical outcomes were compared. RESULTS: A right-sided preference and male predominance typified the unusual group. The incidence of atypical pain and sensory impairment was higher in group II. Group II also showed a less favorable immediate pain outcome, particularly the patients in group IIb. Group IIb also showed a higher incidence of postoperative hemorrhagic complications. However, long-term outcomes did not differ significantly. CONCLUSIONS: Unusual vascular offenders in TN do constitute a significant population. They differ from the usual group with respect to the type of pain, gender, and side of involvement and tend to have more complications with similar pain outcomes after microvascular decompression.