"Eight and a half" and "nine syndrome" rare presentation of pontine lesions; case reports and review of literature

Background: Eight-and-a-half syndrome (EHS) is one-and-a-half syndrome [(conjugated horizontal gaze palsy and internuclear ophthalmoplegia (INO)] plus ipsilateral fascicular seventh cranial nerve palsy. Involvement of lower pontine tegmentum including the abducens nucleus, the ipsilateral medial longitudinal fasciculus (MLF), and the adjacent facial colliculus contribute to the clinical findings of EHS. Recently, nine syndrome with addition of hemiparesis or hemianesthesia to EHS (due to involvement of adjacent corticospinal tract or medial lemniscus) is suggested. Methods: Consecutive patients with presentation of EHS or nine syndrome were reviewed from referral neuro-ophthalmology and strabismus clinics. Results: Three cases of EHS were identified with different etiologies of intracerebral hemorrhage (ICH), demyelination, and neuromyelitis optica spectrum disorder. Moreover, one case of "nine syndrome" due to ICH was described. Brain magnetic resonance imaging (MRI) in all of them revealed lesion in lower tegmentum of pons. Conclusion: Apart from different etiologies, recognition of EHS or nine syndrome allows precise localization of the lesion to lower pontine tegmentum ipsilaterally.