Cranial nerve palsies, SIADH and atrial fibrillation: a diagnostic challenge

We recently encountered a 79-year-old Caucasian man who presented with blurring of vision and facial muscle weakness. The patient also had hyponatraemia, atrial fibrillation with rapid ventricular response and underlying Brugada type II pattern. Urine and serum osmolality were consistent with syndrome of inappropriate antidiuretic hormone secretion (SIADH). It was only after extensive imaging and workup that we were able to tie together these three different presentations of Lyme disease-cranial nerve palsies, SIADH and atrial fibrillation and treat them accordingly. To the best of our knowledge, only eight cases of SIADH in patients with Lyme neuroborreliosis have been reported in the literature. Although our patient did not have a history of arrhythmias, case findings suggest that underlying Brugada type II morphology could have been the predisposing factor, and Lyme disease the trigger.