No abstract

The neural integrator, which converts eye velocity signals into position signals, is central to oculomotor theory. Similar integrators are probably necessary in any neural system that changes and maintains muscular tension. The integrator for horizontal eye position is in the pons, but the locations of the vertical and torsional integrators have not been clearly defined. Recording three-dimensional eye movements in alert monkeys during microstimulation and pharmacological inactivation of midbrain sites showed that the interstitial nucleus of Cajal generates both the torsional and vertical eye position signals. Up and down signals are linked with clockwise signals in the right brain and counterclockwise signals in the left brain. This three-dimensional coordinate system achieves orthogonality and bilateral symmetry without redundancy and optimizes energy efficiency for horizontal visual scanning.

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We describe the first documented association of congenital cytomegalovirus (CMV) infection and cyclopia. A previous report has suggested that any infant with congenital ocular defects should be investigated for CMV infection [Frenkel et al, 1980]. Our case underlines this suggestion and questions a teratogenic role for CMV in cyclopiaholoprosencephaly. More documented cases may help clarify the relationship of transplacental CMV infection to the holoprosencephaly developmental field defect, including cyclopia.

Hereditary trembling chin is an autosomal dominant condition characterized by recurrent bouts of tremor involving the chin. These episodes are precipitated by emotional upset. There has been considerable debate about the gravity of this condition. This may be a benign movement disorder; however, the rhythmic trembling of mentalis at rest or during times of stress in these patients is often misinterpreted as betraying an incipient emotional upset. For this reason, some patients with this condition may find it socially disabling. We have recently successfully treated one such family with regular botulinum toxin injections to the mentalis muscle.