[A case of hemi-hyperhidrosis and non-paralytic pontine exotropia due to brainstem infarction]

A case of hemihyperhidrosis and non-paralytic pontine exotropia due to brainstem infarction is reported. A 55-year-old hypertensive man developed right hemiparesis with slight dysarthria and nausea upon awaking. The right side of his face and right upper limb and trunk to the level of the Th8-9 territory showed hyperhidrosis, which disappeared in a week. Ocular motor examination revealed that during forward gaze with the left eye fixing, the right eye deviated outward. The patient was able to adduct the right eye to midposition with the right eye fixing. Rightward gaze elicited full abduction and right-beating nystagmus of the right eye, but the left eye did not adduct. When he attempted to gaze leftward, both eyes made the full excursion, but saccades were slow in that direction. Convergence was intact. Vertical gaze was full, and he did not show Horner's sign. This ocular sign, non-paralytic pontine exotropia, disappeared three days later. T2-weighted spin echo magnetic resonance imaging disclosed a small lesion with high intensity in the inner side of the left middle pons. This hyperhidrosis was thought to be caused by destruction of inhibitory fibers thermoregulating sweating. These findings suggest that at the level of the middle pons inhibitory fibers descend along the inner side of facilitatory fibers thermoregulating sweating, which are speculated to descend the dorso-lateral part of the pontine tegmentum. These findings also suggest that lesions of non-paralytic pontine exotropia may be located in the paramedian pontine reticular formation rostral to the abducens nucleus with ipsilateral medial longitudinal fasciculus lesion, but further investigation is necessary.