82. Trigeminal neuralgia Flashcards
What are the clinical features of a patient with trigeminal neuralgia?
Sudden, usually unilateral, severe brief stabbing recurrent pain in the
distribution of one or more branches of the trigeminal nerve.
The most common sites are the mandibular and maxillary branches together (42%).
The pain is usually unilateral but may be bilateral in 3%–5% of cases.
The patient typically has a trigger zone.
What is the differential diagnosis?
‘Primary’ trigeminal neuralgia (more than 90% of cases) is caused by an
abnormal vascular loop (usually arterial) in contact with the nerve at the
dorsal root entry zone as it exits the pons.
It is unclear how this contact with the nerve results in the characteristic clinical features however abnormalities of the somatosensory evoked response as well as sensory malfunction have been demonstrated.
It may be detected by magnetic resonance imaging.
Post-herpetic neuralgia
Atypical facial pain
Cluster headache
Temperomandibular joint dysfunction
Lesions by site:
Brainstem Tumour
Multiple Sclerosis (18% of bilateral cases have MS)
Infarct
Syringobulbia
Cerebellopontine angle
Acoustic neuroma
Meningioma
Apex of petrous temporal bone
Middle ear infection
Cavernous sinus
ICA aneurysm
Tumour
Cavernous sinus thrombosis
What features suggest primary trigeminal neuralgia?
Asymptomatic between attacks. Patients with another aetiology as listed
above may complain of persistent pain.
Absence of neurological signs. The presence of any neurological signs
suggests a secondary cause and should be investigated as such.
Pain is usually unilateral.
What treatment options are available?
Treatment will be determined by the cause and the suitability for surgery.
Surgical Microvascular decompression (MVD) involves
craniotomy and the associated anaesthetic and surgical
risks. If an artery is found to be the cause of the
compression it is dissected away and held clear of the
nerve using Ivalon sponge or teflon. Veins may be
ligated or coagulated. ‘Minor’ surgical interventions
include radiofrequency rhizolysis and glycerol rhizolysis.
Pharmacological
Usually involves the use of anti-convulsants such as Carbamazepine (NNT 2,6), phenytoin or sodium valproate.
Signs of complete trigeminal nerve lesion:
Loss of corneal reflex.
Unilateral sensory loss of face, tongue and buccal mucosa.
Mouth opening leads to deviation of jaw to the side of the lesion.
