Introduction: We investigate the microsurgical anatomy of peritrigeminal perforators, that pierce the brainstem in proximity to the trigeminal root, and evaluate their effects on the mobility of the SCA and AICA. Additionally, we propose strategies for mitigating these effects, and the associated potential complications, caused by the presence of short peritrigeminal perforators.
Methods: Retrosigmoid approaches and dissection of neurovascular structures of the upper cerebellopontine angle (CPA) were performed on 11 cadaveric heads (22 sides). The number of perforators as well as their origin, shape, and direction were recorded. Perforators were classified according to their shape and length as either Type I, short direct (< 3 mm in length); Type II, long direct perforators (> 3 mm in length); or Type III, long circumflex (> 3 mm in length) perforators. Transposition of the SCA and AICA away from trigeminal nerve was simulated to determine the level of inhibition posed by the perforators and the degree of useful surgical mobilization was evaluated and graded.
Results: 123 perforators (mean: 5.6 per side, range 1–11) were identified in the upper CPA. Type I was most common at 53.7%, while Type III was the least common at 15.4%. Peritrigeminal Type I perforators prevented mobilization of the SCA and AICA in 22.7% and 13.6% of sides, respectively. In these cases, surgical mobilization for interposition (3 mm) was obtained after extensive arachnoidal dissection of the main vessel. Use of an endoscope helped identify approximately 20% of perforators found.
Conclusions: Identification of inhibiting and potentially dangerous perforators is essential before performing MVD in order to avoid injury to the brainstem and resultant morbidity. The presence of Type I perforators may necessitate extensive surgical dissection of the surrounding arachnoid and the use of an interpositioning technique with minimal repositioning of the offending vessel.
Patient Care: By elucidating an area of potential surgical complications.
Learning Objectives: By the conclusion of this session, participants should be able to describe the inhibiting role of perforators during microvascular decompression for trigeminal neuralgia.