[Electrophysiological examination of the cranial nerves: technical aspects and practical applications]

Electrophysiological investigations of cranial nerves have long been limited to conventional electromyography, but recently have undergone new developments. Brainstem reflex testing is now well defined with correlations to imaging data. Brainstem reflexes can be tested in trigeminal and facial nerve diseases, but also in the case of intra-axial lesions. Surface neurography has developed to quantify troncular nerve responses, abnormal facial nerve responses or assessment of neuromuscular junction function through repetitive stimulation. Transcranial magnetic or electrical stimulation allows to functionnally investigate proximal cranial nerve segments as well as central pathways. Intra-operative monitoring of various cranial nerves can be useful but techniques still need to be validated. Therapeutic use of botulinum toxin involves the electromyographist, as well for the diagnosis as for EMG-guided injections.