Other anatomical abnormalities have been considered, including differences of trigeminal nerve (TN) volume.
No correlation between volumetry and clinical data was detected 1).
The incidence rates of posterior fossa tumor-induced TN range from 2.1–11.6% percent; in the literature; these cases mainly comprise meningiomas (14–54% percnt;), epidermoid tumors (8–64% percent;), and vestibular schwannomas (7–31% percnt;) 2) 3) 4) 5).
It appears that aggressive bony edges may contribute-at least indirectly-to the neuralgia. This should be considered for surgical indication and conduct of surgery when patients undergo MVD 6).
Horínek et al. did not find any association between the clinical neurovascular conflict (NVC) and the size of the posterior fossa and its substructures. MRI volumetry may show the atrophy of the affected trigeminal nerve in clinical neuromuscular conflict 8).
Park et al. did not find any volumetric differences (including the cisternal and parenchymal volumes) 9).
Chiari's malformation and hydrocephalus are rare associates of TN. The pathophysiology of TN in these cases may be due to neurovascular conflict, related to raised intracranial pressure from the hydrocephalus and/or the small posterior fossa volume in these patients. Drainage of associated hydrocephalus may be an effective surgical treatment 10).
High-resolution magnetic resonance imaging scans are able to demonstrate significant volumetric differences of the pontomesencephalic cistern in patients with unilateral TN. A smaller cistern may be correlated with the occurrence of a neurovascular compression, and these findings support the neurovascular compression theory in idiopathic TN 11).
Park et al. confirmed that small pontomesencephalic cistern volumes were more frequent in patients with TN 12).