Transient subacute cerebellar ataxia in a patient with Lambert-Eaton myasthenic syndrome after intracranial aneurysm surgery

Several reports have presented patients with subacute cerebellar ataxia (CA) and Lambert-Eaton myasthenic syndrome (LEMS). Some clinical features of those patients have been described in the previous reports, manifestation of subacute CA prior to LEMS or a co-existence of both diseases, a high incidence of malignancy, and less efficacy of the treatment for subacute CA compared with that for LEMS. Cerebellar ataxia in some patients with LEMS has been suggested to be caused by antibodies to P/Q-type voltage-gated calcium channels (VGCCs). We report herein a patient with subacute CA and LEMS. Cerebellar ataxia appeared 15 months after the occurrence of LEMS, and the onset of CA was thought to be due to serum anti-P/Q-type VGCC antibodies. The clinical course of this patient was atypical, as follows: (1) LEMS preceded subacute CA, which developed after intracranial aneurysm surgery, (2) no malignancy was detected when both diseases co-existed, (3) symptoms of LEMS did not progress with the onset of CA, and (4) there was a definite improvement in symptoms of CA and ¹²³I-IMP SPECT imaging findings after steroid administration. In addition, it is remarkable that LEMS became aggravated in electrophysiologic examinations, in contrast to subacute CA. We suggest that these atypical features of subacute CA and the changes in LEMS may be associated with a balance between the amount of serum anti-P/Q-type VGCC antibodies and the susceptibility of the cerebellum and presynaptic nerve terminals to the antibodies. More cases are needed to investigate the mechanisms involved. The subacute CA and LEMS in this patient have remained comparatively silent after the withdrawal of steroids, and we are continuing to observe her condition.