Paroxysmal alternating skew deviation and nystagmus after partial destruction of the uvula

A patient with suspected brain stem glioma involving the area of the left v estibular nuclei and cerebellar peduncle, developed paroxysmal alternating skew deviation and direction changing nystagmus after biopsy of the inferio r cerebellar vermis resulting in destruction of the uvula. Between attacks she had right over left skew deviation with asymptomatic right beating hori zontal nystagmus. Slow phases of the resting nystagmus showed increasing ve locity, similar to congenital nystagmus. At intervals of 40-50 seconds, par oxysmal reversal of her skew deviation occurred, accompanied by violent lef t beating horizontal torsional nystagmus lasting 10-12 seconds and causing severe oscillopsia. It is proposed that this complex paroxysmal eye movemen t disorder results from (1) a lesion in the left vestibular nuclei causing right over left skew and right beating resting nystagmus and (2) a disrupti on of cerebellar inhibition of vestibular nuclei, causing alternating activ ity in the vestibular system with intermittent reversal of the skew deviati on and paroxysmal nystagmus towards the side of the lesion.