Head and Neck ImagingTrigeminal neuropathy
Patients with trigeminal neuropathy may complain of numbness of the face, weakness of the muscles of mastication, trismus and facial pain.
The facial pain may occur as severe, sudden bursts of pain, distributed along one or more branches of the trigeminal nerve; such paroxysmal attacks are often induced by touching trigger points in or about the mouth. This is known as trigeminal neuralgia or tic douloureux.
Physical examination may show abnormal corneal reflex and decreased pain, touch or temperature sensation; masticatory muscle atrophy may be present.
MRI is the imaging modality of choice. As the clinical examination does not allow accurate localization of the offending lesion, imaging should cover the trigeminal nerve over its entire course (from the nuclei in the brain stem to its peripheral branches). It is also recommended that a T2-weighted sequence of the entire brain is obtained in these patients.
The most common trigeminal nerve lesions can be classified according to the four segments of the nerve:
brain stem:
multiple sclerosis, infarct,
glioma cisternal portion: neurovascular conflict, acoustic and trigeminal schwannoma,
meningioma,
epidermoid cyst,
metastasis Meckel's cave and cavernous
sinus: meningioma,
trigeminal schwannoma, epidermoid
cyst,
metastasis,
pituitary adenoma,
carotid artery aneurysm extracranial part:
schwannoma head and neck,
squamous cell carcinoma head and neck,
lymphoma,
adenoid cystic carcinoma.
A neurovascular conflict is the most common reason for trigeminal neuralgia. The offending vessel is in most cases the superior cerebellar artery, sometimes associated with a cerebellar vein; in a minority of cases, the conflict is caused by a cerebellar vein alone, or by an elongated anterior inferior cerebellar artery or vertebrobasilar artery. In about 30% of the normal population, MR shows a vessel in contact with the cisternal portion of the trigeminal nerve; therefore, the radiological diagnosis of neurovascular conflict can only be made if the nerve appears deformed in the other cases, the close relationship between the vessel and nerve should be reported in descriptive terms. Also, see hemifacial spasm.
RH