One-and-a-half syndrome in ischaemic locked-in state: a clinico-pathological study.

Abstract

SUMMARY Five patients with "locked-in" syndrome and dysconjugate palsy of horizontal gaze were studied. In all cases internuclear ophthalmoplegia due to dysfunction or destruction of the median longitudinal fasciculus was combined with an ipsilateral gaze palsy, producing the "oneand-a-half" syndrome. Clinical and electro-oculographic examination suggested involvement of the paramedian pontine reticular formation when all ipsilateral saccades were abolished, when exotropia of the contralateral eye was present, and when vestibular stimulation showed full conjugate deviation to the damaged side. Involvement of the abducens nucleus was suggested when the palsy of ipsilateral gaze was not dissociated on vestibular stimulation. In three cases these clinical deductions were confirmed by the pathological study, which showed a corresponding destruction -of the median longitudinal fasciculus, paramedian pontine reticular formation and abducens nucleus. In one case the one-and-a-half syndrome evolved into a total horizontal gaze palsy, which corresponded to involvement of the abducens nucleus contralateral to the initially destroyed paramedian pontine reticular formation. Vertical oculocephalic response disappeared, because of destruction of the median longitudinal fasciculus on both sides (bilateral internuclear ophthalmoplegia). Patients with the locked-in syndrome provide a unique situation in which complex pontine oculomotor disturbances may be studied, because consciousness is preserved. In these patients, dissociated and dysconjugate oculomotor palsy may have been underestimated.

Internuclear and supranuclear disorders of eye movements: clinical features and causes

“…Some patients with one‐and‐a‐half syndrome also have an associated facial nerve palsy, hemiparesis, and unilateral hemihypoanesthesia [9]. One‐and‐a‐half syndrome is most often caused by multiple sclerosis, brainstem stroke, brainstem tumors, and arteriovenous malformations affecting the pontine tegmentum [7,16–18]. Ocular myasthenia can also mimic one‐and‐a‐half syndrome [11].…”

Metastatic renal cell carcinoma presenting as one-and-a-half syndrome

“…The paramedian pontine reticular formation (PPRF) is a small ill-defined area in pons, which lies ventral to the abducens nucleus and forms the horizontal gaze center. [ 1 ] Frontal eye field in the cerebral cortex initiates voluntary signals for contralateral gaze, which further passes to contralateral PPRF through superior colliculus. To produce a horizontal saccade, contraction of lateral rectus of one eye and medial rectus of contralateral eye occur simultaneously, with the help of innervations from ipsilateral abducens nucleus and contralateral oculomotor nucleus, respectively.…”