1) To describe the anatomy of the Vth and VIIth nerve emphasizing the structures involved in case of trigeminal neuralgia and/or facial nerve palsy. 2) To learn the routine techniques and potential new imaging techniques used to evaluate these patients. 3) To review the most frequent causes and clinical presentation in these patients. 4) To report the most frequent pathology found on MR and/or CT.
Both the anatomy and pathology of the fifth nerve are best seen on MR. The sequences used in patients with neuropathy (anatomy of the nerves/branches) and neuralgia (neurovascular conflicts) are different but have also some sequences in common. There is however a bad correlation between the clinically involved branch(e.g.V2 )and the location of the lesion (e.g. brain stem). This is the reason why the complete trigeminal system must always be imaged. One should always start with T2 SE images of the brain, selective T2 and proton density images of the brain stem, selective GE or TSE T2 images of the cisternal segment and coronal Gd-enhanced high resolution images through the trigeminal territory. In case of “neuropathy” additional unenhanced coronal T1 and axial Gd-enhanced T1 images through the trigeminal territory should be made. In case of “neuralgia” additional unenhanced and Gd-enhanced time-of-flight images through the cisternal segment should be made. Different pathology will be found for the different segments of these nerves and this again will help the radiologist to narrow the differential diagnosis.
The facial nerve nuclei, cisternal and internal auditory canal segment and extracranial segment of the facial nerve can only be visualised and examined on MR. The labyrinthine, tympanic and mastoid segment of the nerve is only visible on MR but its canal can only be evaluated in a reliable way on CT. A different imaging strategy will be used to study supranuclear, nuclear and infranuclear lesions. The most frequent pathology involving the facial nerve is: neuritis, VIIIth nerve schwannoma, cholesteatoma, trauma, abnormal (congenital) course of the nerve, hemifacial spasm. Centrally infarction and multiple sclerosis are the most frequent causes of facial nerve palsy.
Finally one has to know that 4 major connections exist between the VIIth and Vth nerve. Hence involvement of the Vth nerve can result in VIIth nerve symptoms and vice versa be
Casselman, J,
The Fifth and Seventh Cranial Nerves: Trigeminal Neuralgia and Facial Nerve Palsy. Radiological Society of North America 2007 Scientific Assembly and Annual Meeting, November 25 - November 30, 2007 ,Chicago IL.
http://archive.rsna.org/2007/4402620.html
