A case of idiopathic unilateral peripheral facial palsy showing unique findings and time course of the head shaking nystagmus was reported.
A 15 year-old woman complained of right facial paralysis. She was admitted to our hospital for treatment using a drip infusion of steroids. Three days after onset of the paralysis, she complained of vertigo. At that time she showed no spontaneous or positional nystagmus but manifested right beating nystagmus 5 seconds after the cessation of head shaking stimulation. Six days after onset of the vertigo, right beating nystagmus was also observed but it appeared 40 seconds after the cessation of head shaking. It is assumed that she showed only the 2nd phase of head shaking nystagmus without the 1st phase because of the long latency period. She showed a mild increase in complement fixing antibody titer to the varicella-zoster virus.
The head shaking test is well known to be quite sensitive in the detection of unilateral vestibular disorders. Since the 1st phase of head shaking nystagmus is due to velocity storage, any process that interferes with velocity storage can alter the pattern of nystagmus. When velocity storage is very poor, the 1st phase of head shaking nystagmus may be brief or absent. Thus, it is assumed that the patient in the present report had a lesion in the central vestibular system, presumably in the velocity storage mechanism due to varicella-zoster virus infection.
