Ephaptic transmission is one of the electrophysiological hallmarks of @entity1649 . It is generally accepted that in the majority of @entity1 with @entity1649 , microvascular compression of the facial nerve at the site where the nerve exits the brain stem is the underlying cause. Whether the actual site of the ephapse is at the site of the lesion or at a nuclear level due to hyperexcitability of the facial motor nucleus is still controversial. Rarely, @entity1649 may be due to space occupying lesions in the cerebellopontine angle or in the brain stem. We report the electrophysiological findings of four @entity1 with @entity1649 due to extra-axial @entity5 in different locations of the posterior fossa. The location of the @entity5 was intrameatal in one @entity1 , in the cerebellopontine angle in two @entity1 and in the brain stem in another @entity1 . @entity2103 motor neurographies including transcranial magnetic stimulation revealed abnormal findings in two @entity1 . Selective stimulation of facial nerve branches demonstrated delayed (ephaptic) responses in all but one @entity1 whose @entity1649 had disappeared after treatment with @entity2049 . The latencies of the delayed responses did not correlate with the @entity5 location. In sum, the site of ephaptic transmission cannot be reliably determined by latency measurements of the delayed response because of its variability which is probably caused by the different size and diameter of the axons participating in ephaptic transmission as well as by the extent of focal @entity17 at the site of the lesion. A neuroradiological work up including MR imaging should be mandatory in all @entity1 with @entity1649 because electrophysiological studies fail to differentiate between idiopathic and symptomatic @entity1649 .

Hemifacial spasm due to posterior fossa tumors: the impact of XXXX location on electrophysiological findings.

@entity1 :: ('9606', 'Species') :: ['patients', 'patient'] @entity17 :: ('MESH:D003711', 'Disease') :: ['demyelination'] @entity5 :: ('MESH:D009369', 'Disease') :: ['tumor', 'tumors'] @entity2103 :: ('MESH:D005155', 'Disease') :: ['Facial nerve'] @entity2049 :: ('MESH:D002220', 'Chemical') :: ['carbamazepine'] @entity1649 :: ('MESH:D019569', 'Disease') :: ['hemifacial spasm', 'idiopathic hemifacial spasm']
@entity5 :: (MESH:D009369,Disease) :: ['tumor']
