Special sensory ataxia in Miller Fisher syndrome detected by postural bodysway analysis

To investigate whether ataxia in Miller Fisher syndrome (MFS) is caused by loss of proprioception or cerebellar dysfunction, we studied the power spec trum peak of the body sway frequency in 10 MFS patients, and compared the r esults with those of patients with cerebellar or sensory ataxia. The cerebe llar patients had a peak at 2.4 Hz, whereas sensory ataxia patients had a 1 -Hz peak. Nine of the MFS patients had a distinct 1-Hz peak. Clinical senso ry loss or abnormal sensory nerve potentials were present in only 3 patient s, whereas soleus H-reflexes were absent in all the MFS patients. MFS patie nts have dysfunction of the proprioceptive afferent system, and the special sensory ataxia may be caused by the selective involvement of muscle spindl e afferents.