Recurrent abducens nerve palsy and hypophosphatasia syndrome.

A 47-year-old woman presented with six episodes of horizontal binocular double vision over a 2-year period. CT imaging was significant for extensive dural calcification in the spine and calcification of the skull base, likely involving Dorello's canal. Biochemical testing revealed a persistently low alkaline phosphatase level. Recurrent nerve palsy may possibly be induced by mechanical compression of the sixth cranial nerve in Dorello's canal from calcification due to hypophosphatasia syndrome.

Divided visual attention: A comparison of patients with multiple sclerosis and controls, assessed with an optokinetic nystagmus suppression task.

Multiple sclerosis (MS) frequently causes impairment of cognitive function. We compared patients with MS with controls on divided visual attention tasks. The MS patients' and controls' stare optokinetic nystagmus (OKN) was recorded in response to a 24°/s full field stimulus. Suppression of the OKN response, judged by the gain, was measured during tasks dividing visual attention between the fixation target and a second stimulus, central or peripheral, static or dynamic. All participants completed the Audio Recorded Cognitive Screen. MS patients had lower gain on the baseline stare OKN. OKN suppression in divided attention tasks was the same in MS patients as in controls but in both groups was better maintained in static than in dynamic tasks. In only dynamic tasks, older age was associated with less effective OKN suppression. MS patients had lower scores on a timed attention task and on memory. There was no significant correlation between attention or memory and eye movement parameters. Attention, a complex multifaceted construct, has different neural combinations for each task. Despite impairments on some measures of attention, MS patients completed the divided visual attention tasks normally.