Evoked potentials in trigeminal neuralgia associated with multiple sclerosis

Area of Science:

• Neurology
• Neurophysiology
• Neuroimmunology

Background:

• Multiple sclerosis (MS) is a chronic inflammatory demyelinating disease of the central nervous system.
• Trigeminal neuralgia (TN) is a neuropathic pain disorder characterized by sudden, severe facial pain.
• MS is a common cause of secondary TN, often linked to demyelinating lesions in the trigeminal pathways.

Observation:

• A 49-year-old male patient with established multiple sclerosis presented with a two-week episode of right-sided trigeminal neuralgia.
• The trigeminal neuralgia episode occurred without other clinical signs of a multiple sclerosis exacerbation.
• Serial electrophysiological assessments, including evoked potentials, were performed before, during, and after the symptomatic period.

Findings:

• Brain-stem auditory evoked potentials (BAEPs) from the right ear showed developing abnormalities during the trigeminal neuralgia episode.
• These BAEP abnormalities persisted beyond the resolution of clinical trigeminal neuralgia symptoms.
• The abnormalities resolved in a delayed manner after the cessation of facial pain.

Implications:

• This case highlights a rare clinical-EEG correlation in multiple sclerosis.
• The findings suggest a pontine demyelinating lesion affecting both the right trigeminal sensory root and the right lateral lemniscus.
• Electrophysiological monitoring can reveal subclinical involvement of neural pathways during focal neurological symptoms in MS.