Middle fossa approach for a petrous apex bony spur causing trigeminal neuralgia: illustrative case.

Background: Trigeminal neuralgia (TN) can arise from trigeminal nerve compression at the root entry zone due to neurovascular conflict, which most often presents in the 6th decade of life. The authors report the case of a young patient with TN with a petrous apex bony spur near the entrance of Meckel's cave, causing compression of the proximal trigeminal nerve.

Observations: A 21-year-old woman presented with a 5-year history of progressive right-sided TN. Axial T2 sampling perfection with application optimized contrast using different flip angle evolution magnetic resonance imaging (MRI) did not reveal vascular compression of the trigeminal nerve. However, sagittal reformats demonstrated a prominent bony ridge along the petrous apex, causing compression of the right trigeminal nerve at the porus trigeminus. Removal of the bony spur via a middle fossa approach completely resolved the patient's symptoms.

Lessons: Although TN is most frequently caused by neurovascular compression, it is vital to examine the entire course of the trigeminal nerve on MRI to identify alternative causes of nerve compression in the absence of neurovascular conflict. Bony compression is a rare cause of TN that should be considered, particularly in younger patients. The presence of prominent osseous structures along the course of the trigeminal nerve can be evaluated reliably on sagittal MRI. https://thejns.org/doi/10.3171/CASE24321.